DESIGNING AND PROCESSING POLYLACTIC ACID WITH BAMBOO ADDITIVES

A Major Qualifying Project Report Submitted to the Faculty of the

WORCESTER POLYTECHNIC INSTITUTE

In partial fulfillment of the requirements for the

Degree of Bachelor of Science

in Mechanical Engineering

Submitted by:

____________________________

Brandon Okray

____________________________

Janelle Boucher

Date: 01/14/2014

Keywords:

1. Biodegradable Polymers

2. Bamboo Additives

3. Coupling Agents

Approved by:

________________________________

Prof. Satya Shivkumar, Major Advisor

Acknowledgements

We would like to thank our advisor, Satya Shivkumar, for all his support and guidance

throughout the duration of our project. We thank the mechanical engineering department for their

financial support. We would also like to thank Victoria Huntress in the biomedical department for the use

of her Zeiss microscope. We also want to thank John Macdonald for use of his TGA and DSC machines,

as well as taking the time to help us understand the results for our paper. We also want to express our

deep gratitude to the outside support we received for our project from Dave Beaudoin and Nathan Smith

from Absolute Machinery and Scott Brewer from A. Schulman for the use of their injection molder and

twin-screw extruder respectively as well as donation of supplies. Our project would not have taken off the

ground without their help.

Abstract

The desire for sustainable materials increased investigations into biodegradable polymers and

improving their capabilities with natural fillers for reinforcement. Natural fillers affect processing of

bioplastics therefore the objective of this project was to improve the molding properties of a

biodegradable polymer. For this experiment injection molded samples of polylactic acid (PLA) and

bamboo powder were formed. Observed distribution of the powder within the polymer, flexural and

thermal properties were measures of processing improvements. Optimal temperatures for the injection

molder, pre-heat treatment of the samples, and coupling agents helped processing of the samples. More

improvements are needed for reinforced biopolymers to be competitive with traditionally formed

bioplastics.

Table of Contents Acknowledgements ........................................................................................................................2

Abstract ...........................................................................................................................................3

Introduction ....................................................................................................................................5

Objectives........................................................................................................................................6

Procedure ........................................................................................................................................7

Paper 1 ............................................................................................................................................9

Paper 2 ..........................................................................................................................................20

Design/ CAD .................................................................................................................................35

Conclusions ...................................................................................................................................38

References .....................................................................................................................................38

Introduction

Currently, there is increasing demand for renewable resources and environmentally friendly

products because of the environmental implications of plastic pollution derived from fossil fuels. Another

drawback of synthetic polymers is the increasing and sporadic cost of fossil fuels, a result of supply. In

order to decrease reliance on finite fossil fuels in polymer production polymers developed from renewable

materials are considered a viable substitution. Polylactic acid (PLA) is an example of renewable polymers

made from plants such as corn and potatoes. It is a versatile polymer used widely in the medical and

packaging fields. (Shah, 2008)

However, some of the drawbacks of PLA is its poor mechanical properties such as low strength,

impact toughness, heat resistance and brittleness. One of the ways this can be improved is by using

natural fiber reinforcement. (Lee, 2006) Additionally PLA is an expensive polymer compared to most

commercial polymers. Fiber additives can be used as a method to displace the polymer and thereby

reduce the cost. One of the most promising fibers for reinforcement and as a filler is bamboo. Bamboo is

abundant, fast growing, light-weight, capable of growing in various environments, cheaply processed and

exhibits strength comparable to mild steel. (Khalil, 2012)

The main issue when using natural fibers such as bamboo to reinforce polymers is its composition

which primarily consists of cellulose and lignin. Cellulose is hydrophilic in nature and therefore prevents

sufficient integration into a hydrophobic polymer matrix. As a result, the mechanical properties of the

composite suffer leading to problems with facture and residual stresses within the polymer matrix. (Tran,

2013)

The work in this MQP will investigate the use of coupling agents and compatibilizers to improve

the interface adhesion between bamboo and PLA matrix. PP-g-MA is an anhydride wax which has gained

a lot of interest because of its ability to create homogenous nucleation of hydrophilic additives. The

reactive agent in the anhydride wax is maleic anhydride (MA) which readily reacts and forms bonds with

the hydroxyl functional group in the cellulose of the bamboo. (Khalil, 2012), (Bonse, 2010)

Currently, there is a lack of information on how bamboo powder additives affect the PLA

polymer matrix when it is injection molded. During some initial mixing tests using a brabender at ECM

Plastics (Worcester, MA) there were large agglomerations within the polymer matrix that significantly

reduced fracture toughness and increased brittleness. Therefore, an injection molding process was

selected to be used for its increased torque and mixing capabilities.

This work will use alkaline treatment, coupling agents and injection molding to help improve

some of the traditional drawbacks of using simply pure PLA. This additional processing should show

improvements in the composite’s degradation, flexural properties and agglomeration formation.

However, due to the limited resources and equipment allocated to this project, in order to obtain

the materials and equipment necessary this project will also focus on establishing connections with

companies in the plastics field. This project aims to work with local companies like ECM plastics and

Absolutely Machinery whom are located in the Worcester area.

Objectives

The overall objectives of this MQP are to:

● Communicate with companies in the plastic industry for polymer samples and manufacturing

equipment

● Design a method for producing a polymer with bamboo additives

○ Investigate injection molding settings for producing a usable sample

○ Incorporate coupling agents to improve bamboo distribution and nucleation

● Analyze injection molded samples for improved mechanical, thermal and degradation properties

● Generate a paper to document the results of the PLA with bamboo additives sample produced and

submit for conference publication

● Write a paper on the current status of using bamboo additives with biodegradable polymers when

produced using an injection molder

Procedure

1. Communicate with plastic companies using email and phone to request free samples of various

polymers that could be incorporated into experimentation

a. PLA Prime Natural 3251D from Jamplastics Inc. (Billerica, MA)

b. Bamboo Flour from Natural Sourcing LLC (Oxford, CT)

c. Acrylic Acid from Sigma-Aldrich (St. Louis, MO)

d. Licocene PP MA 6252 from Clariant (Holden, MA)

2. Communicate with plastic manufacturing companies by email and phone to request equipment

that could be incorporated into experimentation

a. Zhafir VE 1900/580 (214 tons) injection molder from Absolute Machinery

b. Brabender from ECM Plastics Inc.

3. Preform preliminary testing of PLA with bamboo flour additives of 20 wt%, 10 wt%, 5wt%,

2wt% and 1wt% using Brabender

4. Redesign procedure for producing PLA with bamboo additives to improve distribution

5. Pretreat bamboo powder using 0.1M Acrylic Acid (AA) and distilled water solution for two

hours to improve surface conditions

6. Dry pretreated bamboo until all moisture is removed and it is a resembles a powder consistency;

approximately ten hours at 75ºC

a. Don’t overdry samples to avoid thermal degradation of mechanical properties

7. Mix 0%, 3% and 5% bamboo powder batches with PLA and PP-g-MA

8. Run injection molder until workable samples are produced

a. Record settings for future experiments

b. Record observations of material as a result of different exit temperatures (high vs. low)

9. Analyze bamboo distribution and agglomerations using scanning electron microscopy (SEM) and

optical microscopy

10. Test samples using 3 point flexural testing, thermogravimetric analysis (TGA) and differential

scanning calorimetry (DSC)

11. Write experimental paper that demonstrates the steps taken to make bamboo and PLA composite.

a. Show procedure

b. Show injection molding settings

c. Show results from:

i. Microscopy

ii. 3 point Flexural Test

iii. Thermogravimetric Analysis (TGA)

iv. Differential Scanning Calorimetry (DSC)

d. Analyze and discuss results

e. Derive Conclusions

12. Submit paper for acceptance to Society of Plastic Engineers ANTEC 2014 Conference

13. Using knowledge from experimental aspects and research article collect data

14. Extract and analyze relevant information

15. Write a review article on the current status of injection molding biodegradable polymers with

bamboo additives

This MQP is presented in the form of two technical

papers:

B. Okray, J. Boucher, and S. Shivkumar, “Processing and Characterization of PLA-Bamboo

Composites with Acrylic Acid Coupling Agent and Maleic Acid Compatibilizer” submitted for

publication in ANTEC proceedings 2014.

B. Okray, J. Boucher, and S. Shivkumar, “Processing of Bamboo Additives in Biodegradable

Polymers” Journal of Polymer Research (2014) submitted for publication.

The papers are attached in the following sections.

Paper 1

B. Okray, J. Boucher, and S. Shivkumar, “Processing and Characterization of PLA-Bamboo

Composites with Acrylic Acid Coupling Agent and Maleic Acid Compatibilizer” submitted for

publication in ANTEC proceedings 2014.

PROCESSING AND CHARACTERIZATION OF PLA-BAMBOO

COMPOSITES WITH ACRYLIC ACID COUPLING AGENT AND MALEIC

ACID COMPATIBILIZER.

Janelle Boucher, Brandon Okray and Satya Shivkumar

Department of Mechanical Engineering

Worcester Polytechnic Institute, MA 01609

Abstract

Biodegradable polymer products based on renewable resources are rapidly gaining interest.

The purpose of this work explores molding behavior and structural characteristics of bamboo

reinforced Polylactic Acid (PLA). Bamboo flour with a particle diameter on the order of 400

microns was mixed with PLA and injection molded. A coupling agent of acrylic acid and maleic

anhydride (MA) compatibilizer was found essential in improving distribution of bamboo

particles in the PLA matrix. The data indicate that the addition of bamboo particles significantly

alters injection molding characteristics. Agglomerations of bamboo particles may contribute to

the observed reduction in flexural strength.

Introduction

In recent years the demand for developing materials from renewable sources has increased

dramatically due a need for ecological sustainability. Currently biological materials are being

combined with many synthetic petroleum based materials such as PC, PP, ABS, HIPS, PET, and

PMMA to potentially improve biodegradation [2]. Thermoplastic materials are being developed

from starches such as PCL, PBAT, PHB, and PLA, approaching complete biodegradation [2].

More importantly as these bioplastics degrade in soil they do not release harmful toxins [9].

Polylactic acid (PLA) in particular has gained popularity in recent years as the one of the most

economically viable plastics for commercial applications because of its desirable mechanical

properties. In addition, PLA is a thermoplastic that can be molded in a variety of processes such

as injection molding, blow molding and extrusion, while still having the ability to undergo

mechanical recycling.

Despite the environmental advantages of bio-based thermoplastics, these polymers tend to be

more costly than traditional commercial polymers and soften in the presence of humidity.

Bioplastics have low elongation at break resulting in brittle behavior [9]. To address these

issues, copolymerization was utilized to combine the monomers of multiple polymers in order to

develop a resulting material with optimum properties. It has been shown with copolymerization

of PBS an improvement in elongation at break and impact strength can be obtained if the

concentration of the comonomer was kept below a certain mol%. Copolymerization can

however lead to a reduction in strength [6].

In order to improve biocompatibility synthetic polymers have been combined with natural

fiber derived from renewable sources such as jute, kenaf, sisal, coconut, and bamboo [2] [8].

Natural fibers are ideal to include in bioplastics because of their relatively low cost in

comparison with current synthetic materials such as glass or carbon fibers. The low density and

hardness of renewable fibers result in the production of lighter materials and reduced abrasion on

equipment during processing [10]. In addition natural fibers have characteristics of high

toughness, versatility, abundance, and most importantly, biodegradability [9]. Disadvantages

associated with natural fibers include a reduced modulus and strength, and an increased

susceptibility to humidity and moisture absorption. The mechanical properties of bioplastic and

natural fiber composites are heavily influenced by the adhesion of the fibers to the polymer

matrix [7]. Due to the fibers’ hydrophilic nature and the hydrophobic characteristic of the

polymer, properties such as elongation at break and strength can be decreased significantly

because of poor bonding at the interface [7].

Among the potential renewable fibers, bamboo has received a lot of attention due to its

incredible physical properties and wide availability. It is a versatile material utilized in

commercial areas such as construction, transportation, eating utensils, clothing, and food. It can

survive a variety of environments and can grow at a rapid rate allowing it to be cheaply

harvested much faster than other woods. Some species of bamboo have a tensile strength that is

comparable to mild steel which makes this material more attractive in biocomposites than other

renewable sources [1].

Many researchers have combined bamboo fibers with polymers such as PP, PBS, HDPE, and

PLA. In each experiment the tensile strength and modulus decreased with increasing weight

concentrations of bamboo [5, 7, 9]. This trend is a result of the contrasting hydrophilic and

hydrophobic characteristics of the cellulose in the bamboo and the polymer matrix. To improve

adhesion pretreatments with coupling agents and compatibilizers have been introduced. In

addition, experiments have emphasized the importance of eliminating moisture in the bamboo in

order to improve processing of the material.

The purpose of this work is to observe the effect of bamboo particle additions on the molding

characteristics of PLA. Commercially obtained bamboo powders were used, thus eliminating

costly or potentially harmful procedures for fiber extraction. The addition of a coupling agent to

improve the distribution of bamboo particles in the PLA matrix was examined.

Procedure

Materials

The base resin PLA Prime Natural 3251D was supplied from Jamplastics Inc. (Billerica,

MA). The banslochan bamboo flour was purchased from Natural Sourcing LLC (Oxford, CT).

The bamboo (Bambusa Arundinacea) was mechanically ground to an average size of 400 μm.

The acrylic acid coupling agent was ordered from Sigma-Aldrich (St. Louis, MO).

Polypropylene grafted with maleic anhydride (PP-g-MA), commercially known as Licocene PP

MA 6252, was the compatibilizer for the batch mix and was supplied from Clariant (Holden,

MA).

Bamboo and Polymer Preparation

A way of improving the properties and surface bonding was to introduce a bamboo surface

treatment and a maleic anhydride compatibilizer. The surface treatment of the bamboo used a

coupling agent, which was a weak acrylic acid (AA) solution that would react with the hydroxyl

groups in the bamboo to reduce bamboo’s hydrophilic nature. The compatibilizer was a small

amount of polypropylene grafted with maleic anhydride (PP-g-MA) which is used to help

improve adhesion of the bamboo and the PLA polymer matrix [1].

The bamboo flour was pretreated by placing the bamboo flour in a 0.1 M solution of acrylic

acid and then draining it. This treatment could also help remove any impurities or oils

accumulated in the bamboo during mechanical separation. The bamboo was left to soak in the

acid for 3 hours. The solution was diluted until it was at a neutral pH and then the liquid was

drained from the bamboo. Subsequently the bamboo flour was placed in an oven at 65C for 12

hours to remove any accumulated moisture. The temperature of the oven was kept relatively low

in order to prevent major thermal degradation of the mechanical properties of the bamboo.

The bamboo flour, PLA and PP-g-MA were mixed together to produce 2.3 kg batch mixtures

at 3 wt% and 5 wt% bamboo. The compatibilizer PP-g-MA was mixed in at 2 wt% to each batch.

Directly before injection molding, the batches were dried again for 3 hours at 100°C, to

minimize any residual moisture.

Injection Molding Specifications

The injection molder that was used was a Haitian Zhafir VE 1900/580 (214 tons) injection

molder, at Absolute Machinery (Worcester, MA). The injection molder was purged with PE

before each new batch. For each bamboo concentration, the entire batch was poured into the

hopper and ran until none of the batch remained. The injection molder was set to a back pressure

of 145 MPa. The 5 zones of the injection molder shown below correspond to 5 zones along the

screw, where the 1st zone is the beginning on the screw and zone 5 is just before injection.

Table 1: Injection molder temperature zone settings

Zone

1

Zone

2

Zone

3

Zone

4

Zone

5

Set Temp.

(°C)

350 340 330 330 320

Sample Characterization

The injection molded samples were examined by an Inverted Zeiss Axiovert 135 Microscope

to study the distribution of bamboo particles. The samples were also examined in an ISM-7000F

Sanning Electron Microscope (SEM). The degradation characteristics were investigated using a

Hi-Res TGA 2950 thermogravimetric analyzer and a Perkin-Elmer DSC 7 differential scanning

calorimeter at a heating rate of 10°C/ min. The flexural properties were measured at a crosshead

speed of 1.667 mm/s. The stress and strain were calculated according to the following equations:

Stress:

Strain:

The P is the load at the given point on the deflection curve (N), L is the support span (mm), R

is the radius of the sample, D is the maximum deflection of the center of the beam (mm), and d is

the depth of the test beam (mm).

Results

In order to gain an initial understanding of the properties of PLA when bamboo was added to

the melting process, a brabender was first used to mix the components. This early mixing

identified the capabilities and drawbacks of bamboo interactions the polymer. When using the

brabender samples of 20 wt%, 10 wt%, 5wt%, 2wt% and 1% bamboo batches were produced.

Immediately after mixing a compression molder was used to produce thin sheets to examine the

distribution of the bamboo particles. The initial results indicated that as the concentration of

bamboo was increased the sheets became brittle. The brittleness of the material made it difficult

to measure the properties. In addition the bamboo flour had a tendency to clump together rather

than evenly dispersing.

Injection Molding of Samples

The results of the brabender showed that the distribution of the bamboo needed to improve as

well as the size of the bamboo agglomerations had to decrease. Several previous studies have

supported the use of Maleic Anhydride as a compatibilizer between the hydrophilic bamboo and

the hydrophobic polymer [1] [3] [4]. The maleic anhydride material used in this investigation

was a polypropylene-grafted-maleic anhydride (PP-g-MA), which is shown to have a positive

effect on the bonding of bamboo with a polypropylene matrix by improving modulus, tensile

strength and surface bonding, however it is also shown to decrease flexural strength and

elongation [3].

During the process of injection molding the batches there were some conditions that

produced noticeably better results. The polymer supplier recommended the temperature for

molding PLA to be about 400°C for optimum viscosity of the material into the mold; however,

when processing the batches with bamboo the material produced wasn’t viscous enough and

resulted in a runny material. Better results were found at ~350°C. Further, during molding, there

were difficulties with the moisture content within the bamboo. This moisture would expand in

the chamber and release hot air making the flow very discontinuous. In order to resolve this issue

the batches were placed in a vacuum bake at 65°C for an additional 3 hours. An additional

observation to note was that, when purging, the batches with bamboo experienced significant

expansion creating a foam consistency.

Table 2: Injection Molding Processing Characteristics at various bamboo concentrations

Bamboo wt% Added 0% 3% 5%

Samples Produced 16 41 26

Average Cycle Time (sec) 16.7 18.8 19.4

Injection Peak Pressure

(MPa) 0.36 0.65 0.47

In Table 2, the effects of bamboo on the injection molding characteristics are compared.

These measurements were taken from the injection molder itself to analyze the melt flow with

the injection molder. On average, 3 wt% of bamboo additive provided the highest injection peak

pressure. Additionally, as the concentration of bamboo increased the average cycle time

increased as well.

Particle Distribution

The optical images of the injection molded samples are shown in Figure 1. In the images, it is

clear that as the batch concentration of bamboo increases there is an increase in the distribution

of bamboo particles in the polymer matrix. Figure 1 shows the difference in transparency

between the 3 wt% and 5 wt% bamboo samples. The 5 wt% bamboo sample is less transparent

and the concentration of bamboo is visibly higher.

In Figure 2, a sample of 3% bamboo and 2% MA-g-PP is shown. The sample shows that

there are some bamboo particles that vary greatly in size. There is a noticeable large bamboo

particle that measures ~450 microns in size. However, most of the other particles measured

closer to 100-200 μm. A closer look at the surface of the 3 wt% sample can be seen below in

Figure 3. The image shows an uneven distribution of the particles and suggests a need for

improvement during processing.

Figure 2: Microscopic image of a sample with 3% bamboo showing clumping (indicated by arrows).

Figure 1: Photographs (5x) of the injection molded samples A – (PLA – 3wt% Bamboo), B – (PLA – 5wt% Bamboo). The

clumping of bamboo particles is indicated by the arrow.

Bamboo

B

Figure 3: Image of a 3 wt% bamboo & PLA sample showing the agglomerations of the bamboo

particles beneath the surface.

Another example of agglomeration is shown in Figure 4. In general as the concentration of

bamboo increased, a greater agglomeration was observed.

Figure 4: Photograph showing large agglomeration of bamboo particles (highlighted by circles) in a

5wt% bamboo sample with 2wt% PP-g-MA compatibilizer.

Figure 5, the interaction of a ~200 μm bamboo particle and the PLA matrix can be seen. This

particle appears to be partly imbedded into the PLA and exhibits poor bonding at the surface.

Bamboo

Figure 5: SEM image of bamboo particle interacting with surface of 5 wt% bamboo sample

Properties of the Molded Product

The TGA data indicate that the decomposition of the polymer begins at a lower temperature

as the wt% of bamboo is increased. The rate of degradation slowed significantly in the 5%

sample containing both coupling agent and compatibilizer, when the sample was about 20% of

the original mass.

The addition of bamboo initially stimulates degradation in a sample exposed to a high-

temperature environment. In both the 3% and 5% batches a residue of up to 10% was observed

even after 500°C. This can most likely be attributed to the decomposition of most of the PLA

from the sample and the residual bamboo. The compatibilizer may have formed stronger bonds

Figure 5: Results of TGA Analysis for Samples

between the bamboo and PLA, which required the temperature and resulting heat to be much

greater in order to break those bonds. A TGA trial was done with solely bamboo flour to

observe its degradation, but the mass of the bamboo only degraded by approximately 6% as the

sample was heated to 600°C. Bamboo additions did not have a significant effect on the glass

transition temperature and the malting temperature as shown in Figure 6. Bamboo particles may

inhibit crystallization in PLA. The addition of bamboo significantly affects degradation of PLA,

generally lowering the overall rate of degradation.

Figure 6: DSC data for various samples.

Flexural strength data show a decrease in strength of both the 3 wt% and 5 wt% composites

by about 14% and 41% respectively at the point of fracture. However the flexural modulus of

the samples increased significantly with the addition of bamboo particles. These results are

consistent with the data from other investigations [5]; however the flexural strength of other

investigations exceed the strength from this experiment which may suggest that the treatment of

the bamboo with the acrylic acid and PP-g-MA may not be quite effective. In addition the

inclusion of bamboo particles enable some stretching in the samples.

Figure 7 Typical flexural stress-strain curves for various samples.

0

50

100

150

200

250

300

350

400

0.0000 0.0500 0.1000 0.1500 0.2000

Fle

xura

l Str

en

gth

(M

Pa)

Strain (mm/mm)

PLA, 0%Bamboo

3%Bamboo

5%Bamboo

Conclusions

The purpose of this work was to observe the behavior of bamboo in PLA. When trying to

injection mold the samples there were several functions needed to enhance molding

characteristics. The bamboo particles had to be dried thoroughly at 65°C for at least 3 hours to

achieve continuous melt flow during molding. Additionally, a more continuous and viscous melt

was achieved when injection temperature was set to ~350°C, compared to the PLA supplier’s

recommendation of 400°C. The addition of the bamboo particles to the degradable polymer,

PLA, may alter the degradation properties. Further bamboo particles in PLA may also lower the

flexural strength but improve the flexural modulus. The addition of both acrylic acid and PP-g-

MA may have improved the bonding characteristics but additional enhancements may be needed

to improve the surface bonding and particle distribution.

Acknowledgements

The authors would like to thank Victoria Huntress and John Macdonald for use of their

equipment and their contribution for obtaining and understanding results in this paper. The

authors would also like to express deep gratitude to Dave Beaudoin, Nathan Smith, and Scott

Brewer for the use of their equipment and donation of supplies.

References

1. A. Khalil, I. U. H. Bhat, M Jawaid, A. Zaidon, D. Hermawan, Y. S. Hadi. Bamboo Fibre Reinforced

Biocomposites: A Review. Materials & Design, 42, 353 (2012).

2. A. Soroudi and I. Jakubowicz. Recycling of Bioplastics, Their Blends and Biocomposites: A Review. European

Polymer Journal, 49, 2839 (2013).

3. B. C. Bonse, M. C. S. Mamede, R. A. da Costa and S. H. P. Bettini. Effect of Compatibilizer and

Bamboo Fiber Content on The mechanical properties of Pp-g-MA compatibilized

Polypropylene/Bamboo Fiber Composites. Proceedings of the Polymer Processing Society 26th

Annual Meeting, (2010 October).

4. D.T. Tran, D.M. Nguyen, C.N. Ha Thuc, T.T. Dang. Effect of coupling agents on the properties of

bamboo fiber-reinforced unsaturated polyester resin composites. Composite Interfaces, 20, 343

(2013).

5. H. Liu, Q. Wu, G. Han, F. Yao, Y. Kojima, S. Suzuki. Compatibilizing and Toughening Bamboo Flour-Filled

Hdpe Composites: Mechanical Properties and Morphologies. Composites Part A: Applied Science and

Manufacturing 2008; 39 (12): 1891-900.

6. J. Xu and G. Bao-Hua. Poly(Butylene Succinate) and Its Copolymers: Research, Development and

Industrialization. Biotechnology Journal, 5, 1149 (2010).

7. M. Thwe and K. Liao. Effects of Environmental Aging on the Mechanical Properties of Bamboo–Glass Fiber

Reinforced Polymer Matrix Hybrid Composites. Composites Part A: Applied Science and Manufacturing, 33,

43, (2002).

8. O. Faruk, A. K. Bledzki, H. Fink, M. Sain. Biocomposites reinforced with natural fibers. Progress in

Polymer Science, 37, 1552 (2012).

9. S. Lee and S. Wang. Biodegradable Polymers/Bamboo Fiber Biocomposite with Bio-Based Coupling Agent.

Composites Part A: Applied Science and Manufacturing, 37, 80 (2006).

10. X. C. Ge, X. H. Li, and Y. Z. Meng. Tensile Properties, Morphology, and Thermal Behavior of PVC

Composites Containing Pine Flour and Bamboo Flour. Journal of Applied Polymer Science, 93, 1804 (2004).

Paper 2

B. Okray, J. Boucher, and S. Shivkumar, “Processing of Bamboo Additives in Biodegradable

Polymers” Journal of Polymer Research (2014) submitted for publication.

Processing of Bamboo Additives in Biodegradable Polymers

Janelle Boucher, Brandon Okray and Satya Shivkumar

Department of Mechanical Engineering

Worcester Polytechnic Institute, MA 01609

Abstract

A desire for sustainability has increased investigations into biodegradable polymers.

However, the capabilities of biopolymers are still lacking which prevents many of these

materials from replacing widely used synthetic polymers. In order to address the shortcomings

of these materials experiments are reinforcing these materials with natural fibers from robust and

plentiful materials in order to improve their properties while still maintaining biodegradability.

A material gaining attention for reinforcement is bamboo due to its strength, abundance, and

inexpensive nature. However, processing biopolymers with natural fibers is difficult because of

cellulose’s hydrophilic characteristics and plastic’s hydrophobic characteristics. This paper is a

review which addresses the processing steps and difficulties of combining biopolymers with

bamboo during injection molding.

Corresponding Author: S. Shivkumar

Keywords: biopolymers, biodegradable, bamboo, fiber, powder

1. Introduction

There has been a strong shift to become more conscious about the use of plastics in everyday

applications and its dependence on fossil fuels for production. The rising price of fossil fuels

most commercial plastics are derived from has generated interest in producing polymers from

renewable resources. The plastic industry is being pressured by new laws and environmentalists

to try and improve the ecofriendly aspects of plastics [1] and [2].

In response biodegradable polymers are increasing in demand because of their

environmentally friendly nature which allows the polymer to readily degrade in the environment

or in composts. In 2007, world production of plastics was about 260 million tons, which in

Europe alone translated to 24.6 million tons of post-consumer plastic waste. Half of the plastic

waste in Europe was disposed of in landfills, whilst 20% was recycled and 30% was recovered as

energy [3]. The demand for eco-friendly materials is rapidly expanding at a rate of 10-20% per

year. Some of the advantages of biodegradable materials include sustainability [4], a high

modulus and low density. These biodegradable polymers have found applications in the

agriculture, medical devices, packaging and household components[5]. However, there are

drawbacks to biodegradable polymers, for example, starch and sugar based biopolymers tend to

have drawbacks such as expensive and poor processability, weak mechanical properties, poor

long-term stability and poor water resistance [4], [5] and [6].

One of the methods for improving the poor mechanical properties of biodegradable

polymers is to use natural fibers to reinforce the material. Fibers have also been used as fillers to

help offset the cost of traditionally expensive biodegradable polymers. Some of the advantages

of these natural fibers additives is their good thermal insulation, low hardness and therefore

reduced machine wear, reduced respiratory and skin irritation, low cost and abundance [7] [8] [9]

[10]. Some examples of natural fibers used for reinforcement include jute, sisal, corn husk,

coconut and bamboo.

Bamboo in particular has drawn a significant amount of attention for its mechanical

properties and commercial availability. The United States and Europe import $254 million and

$230 million, respectively, worth of bamboo every year. Unlike typical wood species that take

20 years to mature, bamboo only takes 1-3 years. After maturity, bamboo can have a comparable

tensile strength to mild steel [11]. Bamboo itself can have impressive mechanical properties as

shown in the table below [11] and [12]:

Table 3: Property ranges for a typical species of bamboo

Bamboo Mechanical Properties

Density

(g/cm³)

Tensile

Strength

(MPa)

Tensile

Modulus

(GPa)

Flexural

Strength

(MPa)

Flexural

Modulus

(GPa)

0.6-11 500-575 57-40 100-150 10-13

One species of bamboo grows at a rate of 2 inches per hour [11] and [13]. Its abundance is

seen in tropical parts of the globe as bamboo plants consist of 20 to 25% of the total biomass in

the tropics and sub-tropics [14]. There are about 1250 species of bamboo and the largest species

can reach a height of 60 feet. There are also approximately 1500 applications of bamboo [15].

These properties of bamboo make it very appealing to use in biodegradable polymers.

In previous works of biodegradable polymers studies involving bamboo have incorporated it

into the polymers as a fiber and as a powder or flour [11] and [14]. Typically, when bamboo

fiber is added to a polymer matrix, it causes the polymer matrix to become stiffer and increases

the tensile strength [11], [6] and [16]. However, using bamboo additives in a polymer matrix can

also greatly reduce impact strength due to stress concentrations created around the bamboo

additive [16]. When examining the research done on bamboo additives in biodegradable

polymers there was a lack of information and consensus on how to process bamboo additives in a

biodegradable polymer matrix. There was also a large variation on what steps should be taken to

process the material.

2. Bamboo Additives Pre-Treatment and Extraction

In the research collected there are two typical methods of adding bamboo into a

biodegradable polymer matrix. One method is to introduce bamboo fibers, which are directional

strands of bamboo laid in the polymer matrix. Another method is to add bamboo powder or flour

into the polymer matrix. Depending on which type of bamboo additive used can yield different

results.

3. Bamboo Fiber Extraction

Bamboo fiber can be prepared using two different methods: chemical or mechanical.

Bamboo, like most cellulose based fibers contains lignin, which bonds the fibers of cellulose

together. During the chemical extraction of bamboo fiber an alkaline treatment is performed to

break the lignin bond known as mercerization [18]. The process has an additional benefit of

reducing fiber diameter effectively increasing rough surface topography resulting in the

improvement of interface adhesion between fibers and the polymer matrix [18]. The alkaline

treatment is typically done by letting the lignin dissolve in a sodium hydroxide bath [19].

However, it is unclear how long and the NaOH concentrations should be, with variations

between 6 – 72 hours and 0.1 M – 1.5 M.

Another method for producing bamboo fibers is to mechanically separate the fibers which

usually involve letting strips of bamboo sit in water until softened. Then a method called roller

molding technique (RMT) is used, which consists of a two stage rolling. RMT has several

advantages including being simple and environmental friendly for producing a large number of

fibers [19] and [20]. During RMT the bamboo strips are rolled in parallel directions until they

reach a desired diameter and length [19]. Another method of mechanically separating bamboo

fibers is to use the compression molding technique (CMT). During CMT, the strips of bamboo

are placed between two flat plates and compressed for a certain amount of time which

determines the thickness of the fibers [19].

Another method of bamboo fiber extraction method that has been gaining interest for its

enhanced fiber properties is the steam explosion method [21]. One study documented their

procedure as cutting the bamboo husks into manageable sections and then placed in a steam

chamber. The steam chamber was set to 175°C and 0.7-0.8 MPa this setting is maintained for

roughly one hour. Then the pressure is released which causes the fibers to separate. The process

of pressurizing, maintaining the pressure and depressurizing was repeated for eleven cycles.

Figure 7: Flowchart of the steps for extracting bamboo powder and bamboo fibers

Then the remaining fibers are treated in a sodium hydroxide solution, washed with water and

then drained to remove everything but the fibers [21].

4. Bamboo Powder Extraction

Typical bamboo powder extraction is much simpler than bamboo fiber extraction and

therefore much cheaper to produce. Therefore, bamboo powder was researched as possible filler

for expensive biodegradable and renewable polymers [14] and [22]. The process for obtaining

bamboo powder involves using small chopped pieces of bamboo broken up into a powder using

a hammer mill or other crushing methods. Then a screen mesh or sieve is used to separate the

bamboo powder based on the desired size. The typical mesh size of bamboo flour used in

injection molding applications will be between 30 and 140 mesh size [14], [23] and [24]. Most

bamboo flour can be obtained through various retailers because of its wide applications in

cooking and cosmetics. Figure one is a flowchart summarizing the processing steps for the

inclusion of bamboo powder or fiber into a polymer matrix.

5. Alkaline Treatment

Alkaline treatment is important when working with any type of cellulose based considered

for reinforcement or as filler. The alkaline treatment is used to remove any impurities and the

waxy surface of the cellulose which prevents the bamboo from mixing with the hydrophobic

polymer matrix. The alkaline treatment increases the fibers wetting ability, the aspect ratio and

the effective surface area that comes in contact with the polymer matrix. Studies show typically a

3% sodium hydroxide, NaOH, will yield significant improvement [2]. Additionally, if the

alkaline treatment is too strong (>4% NaOH) then it starts to decrease the tensile strength of the

fiber [2].

6. Coupling Agents and Compatibilizers

The natural state of the bamboo additive is far too hydrophilic to mix well with most

polymers. An abundance of hydroxyl (–OH) groups are available along the surface of the

cellulosic fibers which absorb moisture in order to bond with these groups [25]. As a result the

hydrophobic nature of polymers repel the bamboo additive during the mixing process. Coupling

agents and compatibilizers are introduced into composites with the intention of bonding their

free functional groups with the hydroxyl groups of the cellulose [20] and [22], creating a network

of covalent bonds known as cross-linking [25]. When successful the bamboo has improved

dispersion and adhesion to the resin resulting in enhanced mechanical properties [26].

Common bonding agents and techniques used with synthetic polymers in the past include

grafted copolymers, silanes, poly/isocyanates, acetylation, alkaline treatment, and enzyme

treatment [12] and [27]. While grafted anhydride copolymers have received much attention in

the past such as maleic anhydride [29], [29], [30], [31] and [32], these materials are usually

grafted on synthetic polymers. In the interest of preserving the polymer’s biodegradability

experiments are transitioning to using bonding agents such as silane [33] and [34] which is

known to improve mechanical and ecological properties [25].

Due to the infancy of studies conducted with biodegradable polymers and bamboo,

coupling agents are still in their experimental phase. The table below summarizes a few

coupling agents used in previous studies.

Table 4: Coupling agents with given biodegradable polymer and resulting property

increase percentages

Polymer Optimum wt% of Bamboo

Coupling Agent

Tensile Strength Improvement

Tensile Modulus Improvement

Elongation Improvement

Source

Polylactic Acid 30 wt% lysine-based diisocyanate (0.65 wt%)

+65%

+10% +15%

[6]

-- Sodium Hydroxide (1.5 N solution)

-- +120% -47% [21]

Polybutylene Succinate (PBS)

50 wt% lysine-based diisocyanate (0.65 wt%)

+200%

+18% +35%

[6]

15 wt% Poly-polyethylene glycol methyl ether methacrylate (7 wt%)

+110%

+33% +35% [36]

Polycaprolactone (PCL)

10 wt% Aluminate (1.6 wt%)

-17% -- -10% [37]

7. Processing Nature of Bamboo

Experiments done in the past that have look at the possibility of simple extrusion and

injection molding bamboo clumps; however, the strength of bamboo was lost through the

processing. Other techniques are currently being research to try and establish high bamboo

content material [38]. Bamboo, when found in nature, is very hydrophilic and therefore will not

mix well with hydrophobic materials, which includes most polymers. Therefore one of the

greatest difficulties for processing bamboo with polymers is the ability to remove the hydrophilic

surface and the moisture content of the bamboo. The bamboo additive itself can come in all

different variations and sizes that can alter its properties; however, generally the bamboo

additives will be comparatively strong, light weight, wear resistant and have low water

absorption [39].

8. Drying

When using an injection molder to create plastics, it is important that the resin and any

additives are free of any excess moisture. Water molecules act to keep fibers separate from the

polymer matrix. In addition evaporation of water during processing can leave behind unwanted

voids in the matrix material [27]. One of the biggest variations found when examining the

process using bamboo additives is the amount of drying required to remove the moisture content

within the bamboo. Drying times for bamboo flour ranged from 75-105°C for 6-48 hours [6],

[17] and [40].

When drying pure bamboo fibers it is important to keep the temperature below 170°C when

drying for longer than 20 minutes and keeping the moisture content of the bamboo powder or

fiber between 1-3% [23]. One study found at the given temperature and time the fiber will begin

to decrease in tensile strength. However, the study also showed that drying pure fibers at 150°C

for 30 minutes increased fiber stiffness by 19% [41].

9. Injection Molding

Bamboo is limited in the types of polymers it can interact with, since it can’t be processed at

high temperatures. Bamboo has been shown to stop interacting with polymers when processed

above temperatures of around 240°C-250°C because at these temperature the bamboo fiber will

undergo thermal degradation. Additionally, there are many other factors that must be taken into

consideration that make it difficult to process such as moisture, agglomerations, hydrophilic

nature and impurities [11].

As discussed be coupling agents and alkaline treatment can help reduce the hydrophilic

nature, moisture content of bamboo and impurity concentration. In order to reduce

agglomerations a majority of experiments had their specimens undergo an initial mixing,

typically through a brabender, twin screw extruder or torque rheometer before the specimens

were injection molded. The pre-mixing step helps disperse the bamboo through the polymer

matrix and improve the reaction of the coupling agent.

When looking at a variety of studies the settings of both the premixing and injection molding

had to be reduced to accommodate the sensitive nature of the fibers compared to powders. For

example, the following study which utilized flour within an HDPE matrix, the twin screw

extruder was set to a speed of 30 rpm and a temperature of 175°C. Then the extrudate was

quenched, pelletized and dried. The dried pellets were used in an injection molder at an internal

melt temperature of 190°C and a mold temperature of 68°C [14]. Typical extruder settings can

be seen below in table 3: In contrast the pre-mixing process using fibers within polypropylene

(PP) used a torque rheometer, which had the screw melt temperature set between 165°C to

190°C and was allowed to mix for 8-10 minutes at 40 rpm. Once the extrudate was generated it

was fed into a granulator to produce pellets of 10 mm. The pellets were then placed in an

injection molder, which had a melt temperature of 175-185°C [42].

Several studies were analyzed of experiments which used biodegradable polymer

matrices and bamboo additives, both for bamboo powder and fiber. Typically, when working

with bamboo powder compared to long bamboo fibers higher temperatures, screw speeds and

back pressures were used to process the bamboo biocomposite. As seen in the table the back

pressure for the injection can vary greatly depending on the size and model of the injection

molder [23] and [35].

Table 5: Injection molder settings for polymers and bamboo additives

Extruder

Settings

Injection

Molder Settings

Polymer

Matrix

Extruder

Temp

Extruder Screw

Speed Time

Melt

Temp

Back

Pressure

Reference

PLA 140 – 190 °C 150 - 250 rpm 5 min 140-190

°C

1.5 - 8

MPa

[23] and

[35]

PHBV 170 °C 50 rpm 5 min 170 °C -

[43]

PHB 175 °C 100 rpm - 175 °C -

[44]

PBS 110 - 180 °C 250 rpm - 160 - 190

°C 8-10 MPa

[23] and

[45]

PCL 100-120 °C 60-100 rpm 5 min 90-110 °C -

[37]

One of the aspects not included in the table but important when using an injection molder is

the cycle time. This directly corresponds to the dynamics in the mold, which will alter the

required injection and cooling temperature. Typically, injection molders will have a short

injection time followed by a much longer cooling time and then a mold opening time. These

three parameters correspond to the cycle time. One indication that the cycle time is too short is to

look for flow marks in the part, which is evidence of uneven cooling dispersion [46]. In one

study a typical ASTM “dog-bone” test specimen had an injection time of 8 seconds, a cooling

time of 25 seconds and finally a mold opening time of 2 seconds.

10. Alternative Processing Methods

Another popular method to producing bamboo fiber reinforced polymer compounds is

hot press compression molding. This is usually done after some kind of initial mixing performed

using a brabender, extruder or torque rheometer. Settings used for hot press compression

molding was to mix polymer samples included a screw speed of 30-70 rpm for 5-10 minutes.

Then the set the hot press compression molder to a pressure of 15 MPa and a temperature of

approximately 180 °C for PLA and 140°C for PBS [6]. Some evidence has shown that hot

pressing can lead to better impact strength properties [21].

Another less common method of producing sample of bamboo and polymer composites is

to use transfer molding. One experiment used a transfer molding die assembly, where the

temperature was set to 200°C and the cavity pressure was set to 150 MPa (Figure 2 shows the

process of transfer molding with bamboo) [47].

Figure 8: Process of transfer molding: Image from Yamashita (2007) [47]

11. Effects of Bamboo on Mechanical Properties

The effect of the inclusion of bamboo additives in a biopolymer matrix on mechanical

properties is summarized in the table below. The mechanical properties would typically see

noticeable changes in tensile and flexural strength, tensile and flexural strength, elongation and

degradation when bamboo was added to the polymer matrix [6].

Table 6: Bamboo additives and their affects on the mechanical properties of the polymer

matrix

Tensile Modulus

(GPa)

Tensile Strength

(MPa)

Tensile Elongation

(%)

Reference

s

PLA 3.4 60 3.3 [12]

PLA + Bamboo

Fiber 3.5-3 50-40 3.5-2 [6]

PLA + Bamboo

Powder 3.8 54 - [6]

PHB 1.04 11 1.94 [44]

PHB + Bamboo

Fiber 1.8 12.05 1.7 [44]

PHBV 2.14 27.3 7 [12]

PHBV + Bamboo

Fiber 2-2.5 20-17 2.5 [48]

PBS 1.1 29 6.7 [49]

PBS + Bamboo 1.5-2.0 31-35 4-6 [6]

Fiber

PBS + Bamboo

Powder 1.8 26 - [23]

PCL - 48 750 [37]

PCL + Bamboo

Powder - 40-15 650-20 [37]

PVA .044 14.0 339 [50]

PVA + Bamboo

fiber 12.9 - - [51]

While the table represents the properties of some biodegradable polymers with bamboo

additives and the use of injection molding it will vary in accuracy depending on the

concentration of bamboo additives in the polymer matrix. For example, in the study using PCL

with bamboo powder additives, when the tensile elongation properties were measured at 30 wt %

and 40 wt % properties changed from ~575% elongation to 20% elongation, respectively [37].

Typically, when looking at variety of studies the range of bamboo concentration was between 0-

20 wt %.

As shown in the table 4 above, when bamboo fiber reinforcement was used it decreased

the tensile strength and elongation but increased tensile modulus. When adding bamboo it will

tend to increase the crystallinity compared to the pure polymer. The crystallinity would tend to

increase more with shorter bamboo fiber or larger agglomerations of bamboo powder [21]. When

adding bamboo flour to a polymer matrix it was found that the tensile strength decreased and

modulus increased. Additionally, the stiffness and brittleness of the polymer composite generally

increased [23]. Studies have also found bamboo powder can significantly improve the storage

and loss modulus of a polymer matrix [45].

Thermal gravimetric analysis of biodegradable polymers such as PLA with bamboo

fibers additives show that in a PLA/bamboo fiber composite thermal degradation occurred at

280-340°C, which is significantly less than pure PLA ~380°C. Additionally, the melt

temperature was roughly 165°C [6]. In one study it was found that the addition of bamboo

powder into a PLA matrix showed a slight drop in Tg [52]. Additionally, pure PHB was found to

have a glass transition temperature and melt temperature of 41.1°C and 166.4°C, respectively

then with the addition of 20% bamboo fiber the glass transition temperature and melt

temperature were 40.8°C and 166.3°C, respectively [44].

Additionally, when the PLA bamboo composite was exposed to enzymatic activity to

observe degradation behavior, the rate of degradation was shown to increase in the presence of

bamboo fiber reinforcement. A similar increase in degradation rate was seen in PBS as well

when bamboo fiber reinforcement was present [6].

12. Conclusion

While the interest in renewable and biodegradable materials is rapidly increasing there is

still a large amount of ambiguity on details to processing these materials. Much research has

been conducted with the introduction of fibers; however, due to the costly nature of fiber

extraction more research should be conducted with the incorporation of cellulose based powders.

The purpose of this review paper is to collect some of the information out there about processing

bamboo additives when using injection molding processes.

References

1. Beldzki, A. K., Sperber, V. E., Faruk, O., Ebrary Academic Complete, & ebrary, I.

(2002). Natural and wood fibre reinforcement in polymers. Shawbury, U.K: Smithers

Rapra

2. Osorio, L., Trujillo, E., Van Vuure, A. W., Verpoest, I. (2011). Morphological aspects

and mechanical properties of single bamboo fibers and flexural characterization of

bamboo/ epoxy composites. Journal of Reinforced Plastics and Composites, 30(5), 396-

408.

3. Lazarevic, D., Buclet, N., Brandt, N. (2010). The influence of the waste hierarchy in

shaping European waste management: the case of plastic waste. Regional Development

Dialogue 31(2): 124-148.

4. Fengwei Xie, Eric Pollet, Peter J. Halley, Luc Avérous, Starch-based nano-

biocomposites, Progress in Polymer Science, Volume 38, Issues 10–11, October–

November 2013, Pages 1590-1628.

5. Corrêa, M. C. S., Branciforti, M. C., Pollet, E., Agnelli, J. A. M., Nascente, P. A. P., &

Avérous, L. (2012). Elaboration and characterization of nano-biocomposites based on

plasticized poly(hydroxybutyrate-co-hydroxyvalerate) with organo-modified

montmorillonite. Journal of Polymers and the Environment, 20(2), 283-290.

6. Lee, S., Siqun Wang (2006). Biodegradable polymers/bamboo fiber biocomposite with

bio-based coupling agent, Composites Part A: Applied Science and Manufacturing,

Volume 37, Issue 1, Pages 80-91.

7. K. Murali, K. M. Rao, Extraction and tensile properties of natural fibers: Vakka, date and

bamboo, Composite Structures, Volume 77, Issue 3, February 2007, Pages 288-295.

8. Mwaikambo, L. Y. and Ansell, M. P. (2002), Chemical modification of hemp, sisal, jute,

and kapok fibers by alkalization. J. Appl. Polym. Sci., 84: 2222–2234.

9. A.K Mohanty, A Wibowo, M Misra, L.T Drzal, Effect of process engineering on the

performance of natural fiber reinforced cellulose acetate biocomposites, Composites Part

A: Applied Science and Manufacturing, Volume 35, Issue 3, March 2004, Pages 363-

370.

10. Sgriccia, N., Hawley, M. C., & Misra, M. (2008). Characterization of natural fiber

surfaces and natural fiber composites. Composites Part A, 39(10), 1632-1637.

11. Khalil, H., Bhat, I., Jawaid, M., Zaidon, A., Hermawan, D., & Hadi, Y. (2012). Bamboo

fibre reinforced biocomposites: A review. Materials & Design, 42, 353-368.

12. Omar Faruk, Andrzej K. Bledzki, Hans-Peter Fink, Mohini Sain, Biocomposites

reinforced with natural fibers: 2000–2010, Progress in Polymer Science, Volume 37,

Issue 11, November 2012, Pages 1552-1596.

13. Chen, X., Guo, Q. and Mi, Y. (1998). Bamboo fiber-reinforced polypropylene

composites: A study of the mechanical properties. J. Appl. Polym. Sci., 69: 1891–1899.

14. H. Liu, Q. Wu, G. Han, F. Yao, Y. Kojima, S. Suzuki, Compatibilizing and toughening

bamboo flour-filled HDPE composites: Mechanical properties and morphologies,

Composites Part A: Applied Science and Manufacturing, Volume 39, Issue 12, December

2008, Pages 1891-1900.

15. J.M.O. Scurlock, D.C. Dayton, B. Hames, Bamboo: an overlooked biomass resource?,

Biomass and Bioenergy, Volume 19, Issue 4, October 2000, Pages 229-244.

16. LEE, Y., YOON, H., TAKAGI, H., & OHKITA, K. (2012). Effects of additive on the

mechanical properties of bamboo/pbs composites. International Journal of Modern

Physics: Conference Series, 6, 780-784.

17. Cai, G., Wang, J., Nie, Y., Tian, X., Zhu, X., & Zhou, X. (2011). Effects of toughening

agents on the behaviors of bamboo plastic composites. Polymer Composites, 32(12),

1945-1952.

18. Kalia, S., Kaith, B.S. and Kaur, I. (2009), Pretreatments of natural fibers and their

application as reinforcing material in polymer composites—A review. Polym Eng Sci,

49: 1253–1272.

19. Deshpande, A. P., Bhaskar Rao, M. and Lakshmana Rao, C. (2000), Extraction of

bamboo fibers and their use as reinforcement in polymeric composites. J. Appl. Polym.

Sci., 76: 83–92.

20. Tran, D. T., Nguyen, D. M., Thuc, C. N. H., Dang, T. T. (2013). Effect of coupling

agents on the properties of bamboo fiber-reinforced unsaturated polyester resin

composites. Composite Interfaces, 20(5): 343-353.

21. Tokoro, R., Vu, D. M., Okubo, K., Tanaka, T., Fujii, T., & Fujiura, T. (2008). How to

improve mechanical properties of polylactic acid with bamboo fibers. Journal of

materials science, 43(2), 775-787.

22. Xu, J. and Guo, B.-H. (2010), Poly(butylene succinate) and its copolymers: Research,

development and industrialization. Biotechnology Journal, 5: 1149–1163.

23. Kim, H. S., Lee, B. H., Lee, S., Kim, H. J., & Dorgan, J. R. (2011). Enhanced interfacial

adhesion, mechanical, and thermal properties of natural flour-filled biodegradable

polymer bio-composites. Journal of thermal analysis and calorimetry, 104(1), 331-338.

24. Isa, A., Minamino, J., Mizuno, H., Suzuki, S., Kojima, Y., Ito, H., Makise, R., Masaki

Okamoto & Takamoto Hasegawa (2013) Increased Water Resistance of Bamboo

Flour/Polyethylene Composites, Journal of Wood Chemistry and Technology, 33:3, 208-

216

25. Bledzki, A. K., Reihmane, S., Gassan, J. (1998). Thermoplastics Reinforced with Wood

Fillers: A Literature Review; Polymer-Plastics Technology and Engineering, 37(4), 451-

468.

26. Lu, J. Z., Qinglin, W., Mcnabb, H. S., (2000). Chemical coupling in wood fiber and

polymer composites: A review of coupling agents and treatments; Wood and Fiber

Science, 32(1), 88-104.

27. Bledzki, A. K., Gassan, J., Composites reinforced with cellulose based fibres, Progress in

Polymer Science, Volume 24, Issue 2, May 1999, Pages 221-274.

28. Dányádi, L., Móczó, J., Pukánszky, B., Effect of various surface modifications of wood

flour on the properties of PP/wood composites, Composites Part A: Applied Science and

Manufacturing, Volume 41, Issue 2, February 2010, Pages 199-206.

29. Bledzki, A. K., Faruk, O., (2004). Wood Fiber Reinforced Polypropylene Composites:

Compression and Injection Molding Process PP, Polymer-Plastics Technology and

Engineering, 43:3, 871-888.

30. Snijder, M. H. B., Bos, H. L., (2000). Reinforcement of polypropylene by annual plant

fibers: optimisation of the coupling agent efficiency, Composite Interfaces, 7(2), 69-75.

31. Keener, T. J., Stuart, R. K., Brown, T. K. (2004). Maleated coupling agents for natural

fibre composites, Composites Part A: Applied Science and Manufacturing, 35(3), 357-

362.

32. Thwe, M. M., Liao, K., (2002). Effects of environmental aging on the mechanical

properties of bamboo–glass fiber reinforced polymer matrix hybrid composites,

Composites Part A: Applied Science and Manufacturing, 33(1), 43-52.

33. Hasan, M. S., Ahmed, I., Parsons, A. J., Walker, G. S., Scotchford, C. A., (2013). The

influence of coupling agents on mechanical property retention and long-term

cytocompatibility of phosphate glass fibre reinforced PLA composites, Journal of the

Mechanical Behavior of Biomedical Materials, Volume 28, Pages 1-14.

34. Gree Bang, Seong Woo Kim, Biodegradable poly(lactic acid)-based hybrid coating

materials for food packaging films with gas barrier properties, Journal of Industrial and

Engineering Chemistry, Volume 18, Issue 3, 25 May 2012, Pages 1063-1068.

35. Okubo, K., Fujii, T., Thostenson, E. T., Multi-scale hybrid biocomposite: Processing and

mechanical characterization of bamboo fiber reinforced PLA with microfibrillated

cellulose, Composites Part A: Applied Science and Manufacturing, Volume 40, Issue 4,

April 2009, Pages 469-475.

36. Bao, L., Chen, Y., Zhou, W., Wu, Y. and Huang, Y. (2011), Bamboo fibers @

poly(ethylene glycol)-reinforced poly(butylene succinate) biocomposites. J. Appl. Polym.

Sci., 122: 2456–2466.

37. Chen Qin-hui, Li Xue-fang, Lin Jin-huo, 2009, Preparation and properties of

biodegradable bamboo powder/ polycaprolactone composites, Volume 20, Issue 3, Pages

271-274.

38. Okada, S., Iizuka, T., Yamaishi, K., Mitani, M., Miki, T., & Takakura, N. (2012).

Examination of injection molding properties of nozzle and attempt of product filling into

mold in injection molding of only steamed bamboo powder. Journal of the Japan Society

for Technology of Plasticity, 53(620), 821-825.

39. Bamboo used as reinforcement, Reinforced Plastics, Volume 52, Issue 11, December

2008, Page 14.

40. Ge, X. C., Li, X. H. and Meng, Y. Z. (2004), Tensile properties, morphology, and thermal

behavior of PVC composites containing pine flour and bamboo flour. J. Appl. Polym.

Sci., 93: 1804–1811.

41. Trujillo, E., Osorio, L., Van Vuure, A. W., Ivens, J., & Verpoest, I. (2010).

Characterisation of polymer composite materials based on bamboo fibers. Submitted to

the 14th European Conference on Composite Materials.

42. Hassan, A., Rahman, N. A., & Yahya, R. (2011). Extrusion and injection-molding of

glass fiber/MAPP/polypropylene: effect of coupling agent on DSC, DMA, and

mechanical properties. Journal of Reinforced Plastics and Composites, 30(14), 1223-

1232.

43. Jiang, L., Huang, J., Qian, J., Chen, F., Zhang, J., Wolcott, M. P., & Zhu, Y. (2008).

Study of poly (3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV)/bamboo pulp fiber

composites: effects of nucleation agent and compatibilizer. Journal of Polymers and the

Environment, 16(2), 83-93.

44. Krishnaprasad, R., Veena, N. R., Maria, H. J., Rajan, R., Skrifvars, M., & Joseph, K.

(2009). Mechanical and thermal properties of bamboo microfibril reinforced

polyhydroxybutyrate biocomposites. Journal of Polymers and the Environment, 17(2),

109-114.

45. Shih, Y. F., Lee, W. C., Jeng, R. J., & Huang, C. M. (2006). Water bamboo husk‐reinforced poly (butylene succinate) biodegradable composites. Journal of applied

polymer science, 99(1), 188-199.

46. Grillet, A. M., Bogaerds, A. C., Peters, G. W., Baaijens, F. P., & Bulters, M. (2002).

Numerical analysis of flow mark surface defects in injection molding flow. Journal of

rheology, 46, 651.

47. O. Yamashita, Yokochi, H. Imanishi, K. Kanayama, Transfer molding of bamboo,

Journal of Materials Processing Technology, Volumes 192–193, 1 October 2007, Pages

259-264.

48. Sanjeev Singh, Amar K. Mohanty, Tomohiko Sugie, Yoshihiro Takai, Hiroyuki Hamada,

Renewable resource based biocomposites from natural fiber and polyhydroxybutyrate-co-

valerate (PHBV) bioplastic, Composites Part A: Applied Science and Manufacturing,

Volume 39, Issue 5, May 2008, Pages 875-886.

49. Yang, Q., Hirata, M., Hsu, Y., Lu, D., Kimura, Y. (2014), Improved thermal and

mechanical properties of poly(butylene succinate) by polymer blending with a

thermotropic liquid crystalline polyester. J. Appl. Polym. Sci., 131.

50. Wei Zhang, Xiaoliang Yang, Cuiying Li, Mei Liang, Canhui Lu, Yulin Deng,

Mechanochemical activation of cellulose and its thermoplastic polyvinyl alcohol

ecocomposites with enhanced physicochemical properties, Carbohydrate Polymers,

Volume 83, Issue 1, 1 January 2011, Pages 257-263.

51. Yao, Wu; Li, Zongjin; Flexural Behavior of bamboo-fiber-reinforced mortar laminates,

Cement and Concrete Research, Volume 33, Issue 1, 2003, 15-19.

52. Avella M, Buzarovska A, Errico ME, Gentile G, Grozdanov A. Eco-Challenges of Bio-

Based Polymer Composites. Materials. 2009; 2(3):911-925.

Design/ CAD

Due to the access limitations to appropriate dies or molds for this project the testing bar

was fashioned from molds available. A relatively long tapered cylinder was used for the flexural

testing for this project. For simplicity of the experimental calculations the diameter where the

load was applied and the length between the supports were used in deflection calculations and

then carried into stress calculations. The Young’s modulus and tensile yield were both taken

from MSDS sheets for PLA from Natureworks.

In order to evaluate the effects of the changing cross-section on the final results in

comparison to a uniform bar two models were created and analyzed using simulation software.

One model was a tapered cylinder with dimensions of our experimental samples and the other

model was a cylinder with a uniform cross-section of the same length. The uniform cross-

section used the same diameter as the experimental deflection calculations for comparison.

The material for the model used the same Young’s modulus and tensile yield values from

the deflection calculations. The constraints were chosen to restrict the X and Z movement of the

neutral axis of the sample on the side with the largest diameter to match the constraints of the

sample during testing and allow for greater deflection. The second set of constraints simulated

the supports. Surfaces simulating the dimensions of the support arms as well as the width

between them were applied to the model then the displacement in the Y direction was set to zero

at these surfaces.

Figure 1: Left shows the X and Z zero displacement along the neutral axis of the model, the right

shows the two Y direction zero displacements on the bottom surface of the part.

A point load was then applied to the top surface of the model at halfway between the two

points. Two loads were used in the analysis in order to show consistencies with the simulation

and the calculations. The two loads were the lowest (6.11 N) and the highest (681 N) which

were seen by the part during testing. When the same constraints and loads were all applied each

model was simulated. The results of the deflection in the y-direction, in the up and down

direction, of both the uniform bar and the tapered bar are compared below. In figure 2 and 3

below the images show the displacement in the y-direction of the highest load applied to both

simulated bars.

Figure 2: Left shows the high load y-displacement of the tapered bar, right shows the high load

y-displacement of the uniform bar

Figure 3: Left is a zoomed in view of the point where the high load was applied to the tapered

bar, right is a zoomed in view of the point of the high load application of the uniform bar.

The images below compare the y-displacement of both simulated bars as a result of the lowest

load applied.

Figure 4: Left shows the displacement results of the low load applied tapered bar, the right shows

the displacement of the low load of the uniform bar

Figure 5: Left is a zoomed in view of the point where the low load was applied to the tapered

bar, right is a zoomed in view of the point of the low load application of the uniform bar.

The results of experimental calculations showed a deflection of 0.065mm for the

minimum load of 6.11 N, while a deflection of 7.3mm was calculated for the maximum load of

681 N. Comparing the results of the uniform bar the light blue area of the low load had a range

of 0.063 to 0.079mm of deflection while the range on the high load simulation was 7.07 to 8.77.

In comparison the same area was used for the tapered part. For the low load application the

range was 0.057 to 0.071mm and the high load application had a range of 6.35 to 7.89mm

deflection.

The range for the tapered edge didn’t reach the exact same values of the ranges of the

uniform bar. However both sets of simulations included the value of the experimental result

within each range. Therefore, the treatment of the tapered beam as a uniform beam, for the

purposes of this experiment, was justified with negligible variations.

Overall Conclusions for the MQP

The results of this project show the potential for biopolymers and their comparable

properties to synthetic polymers. Results from research show a certain weight percent of

bamboo, physical nature of filler, coupling agent, and moisture reduction is necessary for optimal

tensile properties for the reinforced biopolymers. However, these values change with different

polymer matrices, for example, PLA responds well with bamboo concentrations of about 30 wt%

while PCL responds to concentration of 10 wt%. The physical nature of the bamboo additive

also has an effect on the mechanical properties of the polymer, powder shows a greater increase

in tensile strength than fiber while fiber demonstrates a greater increase in tensile modulus than

powder. With regard to experimental results, bamboo powder in PLA reduces flexural strength

at small weight percentages but improves flexural modulus.

References

1. A. Khalil, I. U. H. Bhat, M Jawaid, A. Zaidon, D. Hermawan, Y. S. Hadi. (2012).

Bamboo Fibre Reinforced Biocomposites: A Review. Materials & Design, 42, 353.

2. B. C. Bonse, M. C. S. Mamede, R. A. da Costa and S. H. P. Bettini. (2010). Effect of

Compatibilizer and Bamboo Fiber Content on The mechanical properties of Pp-g-MA

compatibilized Polypropylene/Bamboo Fiber Composites. Proceedings of the Polymer

Processing Society 26th Annual Meeting.

3. D.T. Tran, D.M. Nguyen, C.N. Ha Thuc, T.T. Dang. Effect of coupling agents on the

properties of bamboo fiber-reinforced unsaturated polyester resin composites. Composite

Interfaces, 20, 343.

4. Shah, A. A., Hasan, F., Hameed, A., & Ahmed, S. (2008). Biological degradation of

plastics: a comprehensive review. Biotechnology Advances,26(3), 246-265.

5. S. Lee and S. Wang. (2006). Biodegradable Polymers/Bamboo Fiber Biocomposite with

Bio-Based Coupling Agent. Composites Part A: Applied Science and Manufacturing, 37,

80.