Casting (metals) Forming Plastics - materials, molding and ... · 1 Slide: 1 Plastics - materials, molding and principles of construction List of manufacturing processes: • Casting

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Slide: 1

Plastics - materials, molding

and principles of construction

List of manufacturing processes:

• Casting (metals)

• Forming

• Machining

• Joining

• Molding (plastics)

• Additive manufacturing …

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Polymers and plastics - introduction

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Plastics - examples of applications

Plastics Applications can be found in almost all areas of everyday living due to their versatility.

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The history of plastics

The first "plastics" were modified plastics (from natural raw materials). In 1859, fibra appeared on the

market, and then in 1869 celluloid (nitrocellulose). The first "synthetic material" was phenol-

formaldehyde resin (bakelite), which was introduced in 1908.

Here are the dates of the develop of some popular plastics:

PVC - poly (vinyl chloride) - 1928

PS - polystyrene - 1930

PA - polyamide - 1937

SI - silicones - 1933-1937

PC - polycarbonate - 1956

PP - polypropylene - 1957

PC

What are plastics?

The word plastic derives from the Greek

„plastikos” meaning "capable of being

shaped or molded”.

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What are plastics?

Plastic is the colloquial name for hard polymers at room temperature.

Depending on the method of their processing, two groups can be distinguished: thermoplastic

and thermosetting.

https://nptel.ac.in/courses/104103071/39

Classification of polymers (based on molecular forces)


Thermoplastic Thermoplastic Thermosetting Thermosetting Elastomers Elastomers Fibers Fibers Coatings/ Adhesives Coatings/ Adhesives

plastics

Elastomers at the room temperature

is a elastic material (not a solid).

The plastic at the room temperature

is a rigid material (solid).

What are plastics?





plastics

Processing polymers into end products mainly involves physical phase change such as

melting and solidification (for Thermoplastics) or a chemical reaction (for Thermosets).

Thermosetting polymers, can take shape only once: after they have solidified, they stay

solid. In the thermosetting process, a chemical reaction occurs that is irreversible.

http://www.dc.engr.scu.edu/cmdoc/dg_doc/develop/material/overview/a3000001.htm

What are polimers?

Polymers are built from relatively simple units called monomers (or mers)

through a chemical polymerization process. This process is illustrated below.

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The Greek word "poly" means the English word a lot or many.

The Greek word „Mer” means the English part.

So the „polymer” means „many the same parts”

Polymer is a large molecule, or macromolecule,

composed of many repeated subunits.

Polymer - definition and chemical structure

Polyethylene polypropylene

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Chemical composition of polymers

The basic building blocks of all polymers are

carbon atoms (C) and hydrogen (H).

A special section polymers are silicones, in which

the component is silicon (Si).

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Thermoplastics vs Thermosets polymers

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Thermoplastics vs Thermosets





plastics

Thermoplastic polymers are generally available

in films, sheets, rods, tubing, and several molded

or extruded shapes. Thermoplastic polymers

exhibit plastic properties.

Thermosetting polymers are generally available

in liquid resins.

Thermoplastics vs Thermosets

https://slideplayer.com/slide/6356492/

Thermoplastic polymers exhibit plastic properties.

They can be formed at elevated temperatures,

cooled, remelted, and reformed into different shapes.

In the thermoplastic materials bonds between

polymer chains are weak.

Thermosetting polymers have strong primary

bonds, often formed by condensation polymerization.

Their properties are the result of chemical changes

undergone during processing, under heat or through

the application of a catalyst. Once hardened,

thermosets can not be softened or reshaped. After

cured, if further heat is applied to a thermosetting

material, it will char, burn, or decompose.

Semi-crystalline and amorphous thermoplastic




Thermoplastic Thermoplastic

semi-cristalline

semi-cristalline

amorphous amorphous

Thermosetting Thermosetting Elastomers Elastomers Fibers Fibers Coatings/ Adhesives Coatings/ Adhesives

plastics

Due to the degree of ordering of the internal structure, all solid substances can be divided into

crystalline and amorphous. Crystalline substances are characterized by the regular arrangement of

atoms, molecules or ions. Therefore, they have a strictly defined melting point at which the viscosity

and density change rapidly. Amorphous solids soften gradually during heating and go into liquid in a

certain temperature range.

Two type of thermoplastics

https://texasinjectionmolding.com/injection-molded-composites-outperform-thermoset-composites-on-price-and-performance/

It became well-known to present generally available plastics as a pyramid, the basis of which illustrates

the scale of production of consumer materials, the middle segment represents the share of construction

materials, while the top corresponds to the share of plastics with the best utility properties in the general

group of materials. Plastics occupying the highest positions characterize better functional properties,

expressed through their mechanical, thermal and chemical parameters.

https://www.salon24.pl/u/srodowiskowiec/875361,wszechobecny-plastik

Advantages and disadvantages of plastics

Advantages:

• it is very light (less used fuel during transport),

• you can produce thin walls,

• it can be used repeatedly (limited number of times, glass theoretically in infinite),

• you can get back a lot of energy from it,

• takes little places in transport,

• HDPE and PET are quite safe for health,

• there are many methods of processing and it is usually easy to process,

• it is usually resistant to corrosion, chemicals (not for example PVA),

• they usually have a aesthetic appearance,

• they can easily be colored and mixed with different surface textures,

• injection molded or blow molded parts are sterile (applications in medicine),

• there are many types (flexible, rigid, resistant to chemicals or bioresorbable),

• is cheap.

Disadvantages: • usually they are not resistant to UV radiation,

• usually they are not resistant to higher temperatures (over 100-200 ° C),

• typically, toxic gases are released during smoking,

• the recycling process is currently quite complicated,

• for production, considerable amounts of raw materials are consumed

• it is usually difficult to decompose in the natural environment.

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Plastics - examples of applications

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The use of plastics in car

The average car already contains about 700 parts made of plastics.

Their average mass share is approx. 10%.

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The use of plastics in car - example

In cars there are large plastic components like dashboards or fuel tanks

as well as small ones, such as door handles or mirror housings.

The use of plastics in cars

Abbreviation Chemical

name

Examples

of plastic parts in cars Reason for use

Main methods

of production

ABS

Acrylonitrile

butadiene

styrene

mirror housing, bumpers,

door handle, dashboard

mechanical properties of ABS are impact

resistance and toughness, very good quality of

surface, the possibility of easy and lasting

metallization or painting, the possibility of

production very large components

injection molding

(only mass

production)

caliper

ABS is amorphous and therefore has no true melting point. For the

majority of applications, ABS can be used between −20 and 80 °C


Abbreviation Chemical name Examples

of plastic parts in cars Reason for use

Main methods

of production

PA Polyamide

inlet collectors, gears for car

windows, fans, hubcaps,

covers of engine

very good mechanical strength and

thermal resistance, the possibility

of production precision part

injection molding (mass

production) or milling

(unit production)

injection molding (mass production)

Polyamides occur both naturally

and artificially. Examples of

naturally occurring polyamides are

proteins, such as wool and silk.

Artificially made polyamides are for

example nylons, aramids.


Abbreviation Chemical

name

Examples

of plastic parts

in cars

Reason for use Main methods of production

PC Polycarbo

nate

lamps, car windows,

ventilation tunnels

good mechanical strength,

high transparency, low scratch resistant,

high impact-resistance

injection molding (only mass

production) or thermoforming

(unit or mass production)

injection molding (only mass production) thermoforming (unit or mass production)


Abbreviation Chemical name Examples of plastic parts in

cars Reason for use Main methods of production

PP Polypropylene battery casing, fuel tanks,

containers for petrol

very good chemical resistance,

cheap material, easy to process,

low weight relative to other

polymers; not resistant to UV

radiation

or thermoforming (unit or

mass production),

injection molding

(only mass production)

blow molding

Polypropylene belongs to the group of polyolefins and is partially

crystalline. Its properties are similar to polyethylene, but it is harder

and more heat resistant. Polypropylene is the second-most widely

produced commodity plastic (after polyethylene). In 2013, the

global market for polypropylene was about 55 million tonnes.

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Abbre

viation

Chemical

name Examples of plastic parts in cars Reason for use

Main methods

of production

HDPE High Density

Polyethylene

containers for car fluids, e.g. oil, coolant,

windshield washer and other, cans, pipe

installation

good chemical resistance, very

cheap material, easy to process

blow molding, extrusion

or injection molding

(only mass production)

injection molding

(only mass production) blow molding

In 2007, the global HDPE market reached

a volume of more than 30 million tons.


Abbreviation Chemical name

Examples

of plastic parts

in cars

Reason for use Main methods

of production

SBR styrene-butadiene rubbers

(group of synthetic rubber)

car tires, gaskets,

wipers

very elastics; these materials have good

abrasion resistance and good aging stability

when protected by additives.

extrusion or

injection

molding

The version of SBR was developed by Goodyear is called Neolite. In 2012, more than 5.4 million tons of SBR were

processed worldwide. About 50% of car tires are made from various types of SBR.


Abbre

viation

Chemical

name Examples of plastic parts in cars Reason for use

Main methods

of production

PUR Polyurethane foam sponge to the seats, carpets elastics foaming in mold

While most polyurethanes are thermosetting polymers that do not melt

when heated, thermoplastic polyurethanes are also available.

Polyurethanes are used in the manufacture of high-resilience foam seating,

gaskets, durable elastomeric wheels and tires (such as shopping cart,

elevator, and skateboard wheels), automotive suspension bushings, surface

coatings and surface sealants, synthetic fibers.

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Examples of modern polymers

Kevlar

Lycra Teflon

Main methods of plastics processing

1. for Thermoplastics:

blow molding

extrusion blow molding

injection blow molding

extrusion molding

injection molding

rotational molding (or rotomolding)

thermoforming

…

2. for Thermosets:

laminating

reaction injection molding

vacuum forming

…

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Injection molding

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Usually we design part for injection molding with ribs

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Comparison of the strength

of the part without and with ribs

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Different sizes of plastic injection molding machines

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Construction of an injection machine

Nozzle – An adapter between injection unit and

the mold which is designed to deliver the melt

from the injection unit to the mold

Barrel – This contains the screw and is where

the plastic is melted

Heater Bands – Heat the barrel and keep it at

an appropriate, even temperature to prepare

the melt.

http://www.beaumontinc.com/injection-molding-glossary/injection-molding-machine/

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Construction of an injection unit

http://www.beaumontinc.com/injection-molding-glossary/injection-molding-machine/

Injection molding is a manufacturing process for producing parts by injecting molten material

into a mold.

Polymer granules

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Color palette according to RAL

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Temperature distribution after injection

Construction of the injection mold

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Place of mold assembly

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The next stages of injection molding

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Injection molding - instead of a screw there is a piston

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Mold moving

https://www.polyplastics.com/en/support/mold/outline/ani2.htm Slajd: 44

Visible defects on the injection elements from the ejector and the

injection site

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Sinks and traces of joining mold elements (eg sliders) Views of the injection part

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Examples of injection molds

Examples of injection molds

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Examples of injection molds Examples of injection molds

Examples of injection molds Examples of injection molds

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Recommendations regarding the inclination of the molded walls

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Shaping the walls of the molding

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Shaping the walls of the molding

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Shaping the ribs of the molding

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Recommendation for joining

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Recommendation for joining

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Ways of joining injection elements

good poor

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Extrusion blow molding

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Elements produced by extrusion blow molding

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The next stages of blow molding

Shape of mold to the extrusion blow molding

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Construction of forms for injection blow molding

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The next stages of extrusion blow molding

https://www.petallmfg.com/blog/how-extrusion-blow-molding-differs-from-injection-molding/

Extrusion blow molding (EBM) is a manufacturing process whereby plastic is melted and extruded to a

hollow tube. The next mold is closed on this plastic. The parison is held and sealed in the metal mold.

Air is then blown into the mold thereby shaping it into the desired shape of the bottle or container. Once

the plastic has cooled, the mold is opened and the part is discharged.

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Diagram of packaging production using blow molding technology

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Advanced blow molding technology Examples of packaging manufactured by blowing

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Visible defects on blow molds

- traces from the elements of the mold

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Injection blow molding

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Preforms form injection blow molding

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Preforms form injection blow molding

www.polimer.org.pl

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Heating preforms

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www.polimer.org.pl

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Injection Stretch Blow Molding

http://www.silganplastics.com/capabilities-technologies/injection-stretch-blow-molding-ISBM Slajd: 80

The rules of shaping the blow molds

http://www.witoplast.pl/pl/site/100/102/historia.html

Finished bottles

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Visible defects - patch of mold elements and thickness

changes

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Rotational molding (rotomolding)

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Rotational molding

Rotational Molding is a thermoplastic process for producing parts by placing powder or liquid resin into

a hollow mold and rotating the tool bi-axially in an oven until the resin melts and coats the inside

of the mold cavity. A resin powder is either dumped or blown into the cavity to create a foamed

core. Next the tool is cooled and the part is removed from the mold.

www.abplanalp.com.pl

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Diagram of the rotational casting process

https://lifeark.net/rotomolding Slajd: 86

Rotational molding machines

www.marseille.com.pl

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Example of rotational molding process

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www.abplanalp.com.pl

Example of rotomoulding parts

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Vacuum thermoforming

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The process of thermoforifying plastics (ABS, LDPE, HDPE, PP, PCV, PMMA) consists in heating the

plastic plate until it reaches the state of plasticity and creates a vacuum between the above-

mentioned plate and mold.

www.michart.vel.pl

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Example of vacuum thermoforming parts

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elcar.com.pl

Example of vacuum thermoforming parts Vacuum Forming

https://www.custompartnet.com/wu/thermoforming

Vacuum forming - A vacuum is formed between the mold cavity and the thermoplastic sheet. The vacuum

pressure (typically 14 psi) forces the sheet to conform to the mold and form the part shape.

Pressure Forming


Pressure forming - In addition to utilizing a vacuum underneath the sheet, air pressure (typically 50 psi, but

up to 100 psi) is applied on the back side of the sheet to help force it onto the mold. This additional force

allows the forming of thicker sheets and creating finer details, textures, undercuts, and sharp corners.

Mechanical Forming


Mechanical forming - The thermoplastic sheet is mechanically forced into or around the mold by direct

contact. Typically, a core plug will push the sheet into the mold cavity and force it into the desired shape.

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Casting (metals) Forming Plastics - materials, molding and ... · 1 Slide: 1 Plastics - materials, molding and principles of construction List of manufacturing processes: • Casting