72 World Journal of Textile Engineering and Technology

72 World Journal of Textile Engineering and Technology, 2020, 6, 72-88

E-ISSN: 2415-5489/20 © 2020 Scientific Array

Multi-Functional Finishing for Cotton Materials

Vasilica Popescu1,*, Daniel Manole1 and Luminita Ciobanu2

1Department of Chemical Engineering in Textiles and Leather, “Gheorghe Asachi” Technical University, 29 Blvd. D. Mangeron, Iasi, 700050, Romania 2Department of Knitting and Garment Engineering, “Gheorghe Asachi” Technical University, 29 Blvd. D. Mangeron, Iasi, 700050, Romania

Abstract: Finishing treatments are used to improve the comfort indices or to induce special properties for the textile supports. Regardless of their category, all these treatments can generate maximum 2 effects, like fireproof and anti-crease, waterproof and oleophobization, anti-crease and fireproof or any other such combination, according to the finishing agents and treatment conditions. Multi-functional finishes (more than 3 simultaneous effects) require the judicious selection of the treatment agents, working conditions and most suited textile support. The selection of the finishing agents is based on the chemical structure, reactivity, compatibility with other chemical compounds, efficiency. The nature of the textile fibers, fabric weight, density and destination are the selection criteria for the textile support. This paper deals with the creation, experimentation and optimization of a finishing treatment that generates 4 simultaneous effects: fireproof, anti-soil, oleophobization and anti-crease. The final treatment was obtained by combining the substances that are normally used in the classic individual finishing treatments, following numerous experimental combinations of different concentrations, treatment agents and catalysts. The optimum treatment variants were identified using statistical analysis. The method of multiple linear regression allowed quantifying the multi-functional finishes by modelling each effect (the char length, crease recovery angles and anti-soil and oleophobization effects). The study also determined the positive/negative influence of the 3 independent factors (the treatment conditions, X1, X2 and X3) on the optimum multiple effects; they corresponded to the situation when X1, X2 and X3 were close to the “zero” value.

Keywords: Fireproof, anti-soil, oleophobization, anti-crease, statistical analysis.

1. INTRODUCTION

The textile fabrics used for protective equipment must be chemically treated / finished so that they will acquire several effects needed to protect the users according to the specificities of the work place [1]. The finishing treatments are used to improve the comfort indexes (no creasing, permanent-press, no soiling, no static charge, oleophobization) or to impart special properties to the treated textiles (fireproofing, hydrophobization/waterproofing).

The selection of the finishing treatments to be applied to a certain fabric is based on its type/nature, compatibility with the chemicals and especially what type of effects are desired [2].

More chemical compounds, each for a different effect, must be used for multi-functional finishes. In these cases, the optimum mix of effects is difficult to obtain, even if the treatments are well done. Statistical analysis represents an efficient way to optimize treatments for multi-functional finishing, most used being regression and dispersion analysis [1, 3].

*Address correspondence to this author at the Department of Chemical Engineering in Textiles and Leather, “Gheorghe Asachi” Technical University, 29 Blvd. D. Mangeron, Iasi, 700050, Romania; Tel/Fax: +40 232 230491; Email: [email protected]

The most significant input variables for a finishing treatment considered for these statistical methods are the treatment parameters (temperature, time) and concentration of the compounds [1].

For protective equipment used by people in close proximity to fire (firefighters) or high temperatures (steel workers, stokers), the textile materials must withstand flame/fire, must not catch fire, nor get wet or soiled.

When considering the burning behavior of the textile fibers, one may observe that best behavior is exhibited by glass, asbestos and certain polyclorvinil fibers which are considered fireproof. Still, these fibers are not used in protective equipment, as they do not offer comfort, glass is irritating and asbestos is among the carcinogens.

Fibers with fireproof characteristics (polyamides, polyester, polyetilene, cellulose acetates, wool) have clear disadvantages, as the synthetic fibers melt when subjected to fire and would adhere to the human skin with severe consequences, while wool fibers do not ensure thermal comfort to the user in case of fire or high temperature.

Other possible textiles for protective equipment could be made of inflammable fibers (like acrylic, rayon, cellulosic fibers, silk) that are treated to resist the action of fire and the resulting high temperatures [4].

Multi-Functional Finishing for Cotton Materials World Journal of Textile Engineering and Technology, 2020, Vol. 6 73

Most textile materials catch fire and burn; pyrolysis (irreversible chemical decomposition) appears in the areas in direct contact with the flames, generating the so-called “carbonized areas”. A mix of flammable and inflammable gases and liquids/solid byproducts (tars/coals) are formed during burning.

It is important for the textile material to start burning at the highest possible temperatures and then develop the smallest amount of heat (in order to inhibit the burning process) and as much noninflammable gases as possible [5].

Cotton textile materials are most used for protective garment items, but untreated cotton burns quickly with a strong flame, leaving embers that immediately turn into char.

Soil behavior of textile materials: Part of the finishing process that improve the comfort indices are treatments controlling the soil behavior of textiles: anti-soil, antistatization and oleophobization [2, 5-8].

Anti-soil finishes prevent the fabrics from getting soiled with dry / pigmentary particles or wet dirt brought by water. If the fabric soils, but the dirt is completely removed during washing, then the treatment is passive, actually a soil-release finishing.

Oleophobization is another anti-soil treatment that protects the fabrics from soiling with oils and their impurities.

Textile materials can soil through staining, direct contact with dirt particles, particle attraction due to static charge or dirt re-deposit during washing [2, 5-8].

The soiling phenomenon depends on the type of dirt and nature of the textile material, as follows:

a. Solid dirt that is insoluble in water or solvents – they soil the fabrics through direct contact or deposit of air particles like pigments, metals, dust, suit, etc. (aerosols);

b. Soluble or water dispersed dirt – it is the case of juices, coffee and components of sweat (salts, urea, amino acids, etc.)

c. Oily dirt, insoluble in water, but soluble in organic solvents – they can act alone or in combination with other dirt particles in suspensions, like fats, waxes, resins, pigments, etc.

Soiling due to physical contact can occur in the following situations:

• Direct contact with dirt and transfer of dirt and fats from skin; it is common to collars and cuffs;

• Direct contact with aqueous/oil solutions that contain dirt particles dispersed in water or oil;

• Direct contact through friction on soiled surfaces;

• Direct contact of textile materials with dirt particles from aerosols.

The nature of the textile fabric influences its capacity to retain dirt, as well as the degree of soil visibility in the following way:

• natural fibers (cellulosic and protein) retain a bigger amount of dirt, but it is not so visible; furthermore, these materials are more difficult to wash due to the bilobate or rugged structure of their fibers (bean cross section for cotton and scales for wool);

• synthetic fibers retain a smaller amount of dirt, but the dirt is strongly visible due to the fibers’ circular cross section, as well as the specific extremely low hydrophilicity that do not allow the dirt particles to penetrate the fabric, forcing them to remain at its surface.

The anti-crease finish of cellulosic materials is a treatment for the dimensional stability of fabrics based on their chemical setting.

A recipe for anti-crease finishing must contain the following substances [3, 5, 9]:

1. crosslinking agents;

2. catalysts;

3. auxiliaries/softeners.

1). The crosslinking agents can be grouped into [3, 5, 9]:

• self-crosslinking, substances producing resins in the treated fabric;

• substances with double action, self-reticulation and reticulation of cellulose;

• reticulation reactants, such as the reactant resins with or without nitrogen in the molecule.

2). Catalysts are very important as they increase the speed of the curing reaction and the elimination of

74 World Journal of Textile Engineering and Technology, 2020, Vol. 6 Popescu et al.

water between the OH groups in the cellulose, respectively the reticulation agents. As catalysts, at the end of the treatment, they maintain their initial amount. Still, their type and nature influence the effect of the anti-crease treatment. The catalysts can be acids, acid generators (metallic salts) or bases (NaOH). Catalysts are selected based on their nature and reactivity of the crosslinking agents, the nature of the textile support and the parameters of the curing reaction.

Considering the reactivity and chemical structure of the crosslinking agents, the catalysts can be as follows [3, 5, 9]:

a) more reactive crosslinking agents, containing nitrogen in the molecule require as catalysts only salts that free inorganic acids during the curing reaction;

b) less reactive crosslinking agents, with nitrogen in the molecule require more energetic catalysts, like strong inorganic acids (H2SO4, HCl, HNO3,

etc.);

c) agents that have no nitrogen in their molecule require alkaline catalysts like NaOH.

3). The softeners are added in the bath to improve the rough touch caused by the other substances used for crosslinking/reticulation. The softeners can be anionic (alkyl sulfates, condensation products of the fatty acids), cationic (ammonium quaternary salts, aminoesthers, aminoamides), or even nonionic (polyoxyethylene products, ethers or polyglycolic esters) [5].

The anti-crease effect is caused by the reticulation of cellulose, the formation of chemical/covalent bonds between the resin and fibers and the deposit of resin within the fibers [3, 5, 9].

The paper aims to present the optimization of a finishing treatment with multi-functional finishes applied on a cotton woven fabric used for protective equipment. The effects are: fireproof, anti-soil, oleophobization and anti-crease.

2. MECHANISMS OF THE FINISHING TREATMENTS

2.1. Fireproofing Mechanisms

Fireproofing is a finishing treatment that protects the textile materials from fire, flame, therefore ignition, burning or flame propagation.

The protection of textiles against fire is obtained using substances containing phosphorus, nitrogen combinations, halogens or sulphur [1, 5 ,9]. The fireproofing effect can be permanent or temporary, resistant to a few home washings cycles [5]. Still, most used fireproofing agents are based on combinations of phosphorus and halogens that can create permanent fireproof effects, if the treatment is done correctly.

The following theories can be used to explain the fireproof effect:

1. Theory of the gaseous medium: states that the fireproof effect/protection against burning is caused by the fireproofing agents, that under the action of flames and high temperatures liberate high quantities of non-inflammables gases/vapors, such as CO2, NH3, SO2;

2. Theory of the protective layer: states that the fireproof effect/protection against burning is caused by the fireproofing agents that melt at relatively low temperature and form a glassy layer that cuts the flow of oxygen toward the textile fabric, stopping the burning process;

3. Modern theory: states that the fireproof effect is caused by one of the two phenomena:

a) decrease of the amount of energy released during burning by the fireproofing agents; this causes fewer inflammable gases; therefore, less heat is liberated during the burning process. Examples:

1) phosphorus based fireproofing agents applied to cotton fabrics;

2) halogen based fireproofing agents disrupt the burning process by slowing the reaction, releasing smaller amounts of energy in time and decreasing the temperature of the burning points. The halogen based fireproofing agents (fluorine, chlorine) create fireproof effects but with different efficiencies.

b) increased amount of energy needed for the treated fabric to start burning.

An ideal fireproof treatment for cotton fabrics should lead to a complete dehydration, without any release of volatile gases and tars that could maintain and propagate the flames, generating only char/carbon (it is known that the reaction products of any pyrolysis


process are carbon and water) [10]. The resulting char can propagate only smouldering burning that develops only noninflammable gases like CO2 [1, 2, 5].

A comparison of the percentage of inflammable gases developed during the burning of cotton materials with or without fireproof treatment shows that:

• Treated cotton fabrics subjected to open flames develop only 40% inflammable products and 5 - 40 % char;

• Untreated cotton fabrics subjected to open flames develop up to 80 % gases/inflammable products.

The presence of the fireproof agents reduces the heat released through the burning of inflammable gases and increases the amount of residual char that limits the flames [5].

The burning process of the cellulose from the cotton fibers contains the following stages [1, 2, 4, 5]: ignition, propagation and afterglow.

1. Ignition (short time): requires the presence of open fire or an external heat source to ignite the fabric;

2. Fabric burning/propagation: flame burn of cotton, producing incandescent embers and finally char. In this stage, the flames are rapidly propagated, the fire intensifies and the textile fabric burns completely, leaving only ash/char. Flame propagation depends on the rate of the pyrolysis reaction, the amount and especially the volatility of the pyrolysis products, the amount of oxygen around the textile fabric, the fabric weight and surface structure (compactness, hairiness) [1, 5].

3. Afterglow: The subsequent burning of the char formed during the second step involves two stages of successive oxidation: in solid state, forming CO and in gaseous state, forming CO2 [5]. The afterglow may be prevented by depositing soluble salts on the textile fabric that will inhibit the flames, as well as the following incandescence (afterglow).

2.2. Anti-Soiling Mechanisms

Anti-soiling mechanisms are:

• in case of an active anti-soil treatment, the agents prevent the deposition and adherence of

any dirt particle on the fabric surface, due to the modification of tension at the treated fabric’s surface, as well as the repelling forces that appear between the dirt particles and the finishing agent [2];

• in case of soil-release, as passive anti-soil finish, can be explained based on [2]:

Ø a certain level of hydrophily generated by the hydroxyl or carboxyl groups in the agents used for treatment;

Ø the lower water-fiber interfacial tension increases the fiber – finishing agent – dirt interfacial tension; this causes an easier detachment/dislocation of the dirt particles;

Ø the increase of the ionic/electronegative capacity of the finished fibers also leads to the easier detachment/dislocation of the dirt particles, reducing their ability to be redeposited on the fabric.

2.3. Anti-Creasing Mechanism

The use of anti-crease crosslinking agents can increase the fabric elasticity due to the reticulation between the agents and the textile fibers, usually of cellulosic nature. This reticulation links the two partners (finishing agents – fibers), reducing the fabric’s tendency for dimensional change under external stress [9].

3. CLASSIC RECIPES FOR FINISHING TREATMENTS

Based on the mode the finishing treatments are carried out, they can be grouped as follows [11, 12]:

a) non-reactive mode

1. Deposition of the finishing agents on the textile support;

2. Exhausting of the agents in the treatment bath;

3. Adding of finishing agent in fibers, before spinning.

b) reactive mode:

1. Reaction between the finishing agents and textile fibers;

2. Copolymerization of a graft with the textile fiber;


3. Copolymerization of finishing agents with the monomers forming the fibers;

4. In situ polymerization of the finishing compounds.

Usually, a reactive finishing treatment employs the pad-dry-cure technology and has the following stages: impregnation, squeezing, drying, curing and final steps [1, 9, 13, 14] (see Table 1).

The classic recipes presented in Table 1 can create maximum 2 effects: fireproof+anti-crease; hydropho-bization+anti-soil; anti-crease+hydrophobization (water proofing).

The following conditions are required in order to obtain more than 2 finishing effects:

- the finishing compounds must be compatible and ensure the desired effects;

- the finishing recipes must ensure optimum effects;

- the odor the agents release during storing/interaction with cellulose must not be unpleasant;

- the treatment does not affect the fabric whiteness or color;

- the treatment does not destroy the fabric.

Literature [5] indicates that the amounts of finishing agent depend on the type of fibers, fabric weight, density and the desired level of finishing. In order to obtain multiple finishing effects, it is recommended to add to the impregnation bath 300 - 400 g / L Pekoflam DPN-1 liq., a crosslinking agent like Arkofix NDS (40-80 g / L reactant resin, contains nitrogen and produces small amounts of formaldehyde on finished products) because it creates a synergetic fireproof and anti-crease effect that resists to cold/hot washing. If the recommendation is not followed, the amount of fireproofing agent must be increased significantly. For a hydrophobization/oleophobization effect, wetting agents (like Sandozin, with 3 g/L concentration) or water and oil repellents (40-60 g/L Nuva FB) can be added to the impregnation bath. Another surfactant agent, 15 g/L Ceraperm MW (hydrophilic micro silicone emulsion) and 20-25 % phosphoric acid (85 %) as cat-alyst can be also added. After impregnation, the fabric is dried at 110-130 °C, followed by curing at 160 °C for 2 minutes. In the end, the fabric is rinsed and then neutralized with 5-10 g / L sodium carbonate at 60-80 °C, neutral rinsing and finally, drying at 100-120 °C.

4. CONTROL OF THE MULTI-FUNCTIONAL FINISHING TREATMENTS

4.1. Control of Fireproof Treatments

In general, the following characteristics indicating the efficiency of the fireproof treatment are determined after the Burn test [1, 2, 5, 9]:

Table 1: Classic Recipes for Mono-Functional Finishing

Finishing treatments Stages

Fireproof Anti-soil Anti-crease

Padding 500 g/L Pekoflam DPN-1 60 g/L Cassurit HML

25 g/L orthophosphoric acid

40 g/L Tubiquard 66 20 g/L Tubicoat HPE 2 mL/L CH3COOH

40 g/L Arkofix-NEC plus 80 g/L Appretan-N-9212

20 g/L Ceraperm-MW 20 g/L Ceranine-L

6 g/L MgCl2

Squeezing DS= 70 % DS= 70 % DS= 70 %

Drying 100 ˚C, t = 2 min. 100 ˚C, t = 2 min. 100 ˚C, t = 2 min.

Curing t = 2 min. 150 ˚C 130 °C, t=2 min. 150 °C, t=4 min

Rinsing 20 ˚C 20 ˚C 20 ˚C

Neutralization 20 g/L Na2CO3; t=20 min.; T=60 ˚C

20 g/L Na2CO3; t=20 min.; T=60 ˚C

20 g/L Na2CO3; t=20 min.; T=60 ˚C

Warm, then cold rinsing

40 ˚C 20 ˚C

40 ˚C 20 ˚C

40 ˚C 20 ˚C

Drying 100 ˚C 100 ˚C 100 ˚C


• Length of the carbonized area;

• Flame propagation time;

• Incandescence time;

• Limiting Oxygen Index (LOI).

4.2. Control of Anti-Soil Treatments

The anti-soil effect is evaluated based on:

• in the case of anti-soil treatments: if dirt particles do not penetrate the textile fabric the anti-soil effect is considered good;

• in the case of soil-release treatments: measuring the soiling degree/concentration of deposited dirt, whiteness assessment, rate to which dirt is redeposited, photometric characteristics, dirt visibility. The tests used to evaluate the soil-release effect are:

Ø SAD index (Soiling Additional Density) [15, 16];

Ø AATCC 130-2004 (Soil release Test) [15].

The efficiency of the oleophobization treatments can be determined based on: AATCC 118-2004 (Oil Repellency test) or AATCC 130-2004 (Soil release Test) [15].

4.3. Control of the Anti-Crease Treatments

The anti-crease treatment is more efficient if the following aspects are ensured [2, 5, 9]

• Higher crease recovery angles (CRA);

• Quality indexes over 1; these indices consider the crease recovery angles, as well as the loss of strength at breaking caused by the reticulation phenomenon specific to the finishing treatment;

• Minimum modification of fabric color for the finished materials;

• Minimum amount of yellow stains in the case of white fabrics with anti-crease finish; usually, the stains appear due to the thermal degradation at high temperatures during the curing process;

• Low chlorine retention, during home bleaching with NaOCl;

• High resistance to acid or alkaline hydrolysis.

EXPERIMENTAL PART

5. MULTI-FUNCTIONAL FINISHING TREATMENTS

The paper proposes and tests a treatment for multi-functional finish: fireproof + oleophobization + anti-soil + anti-crease. The optimum variants for each effect were determined using statistical analysis (multiple linear regression) [3, 17-20].

5.1. Materials

The experiments were carried out using a 100 % cotton woven fabric with 150 g/m2, that was previously dyed with vat dyes. The finishing treatment used the

Table 2: Recipe and Treatment Stages of the Multi-Functional Finishing

Operation Recipe

IMPREGNATION 200-400 mL/L Pekoflam DPN-1 27-53 g/L Tubiguard 66

20 g/L Tubicoat HPE 40 g/L Cassurit HML

20 g/L orthophosphoric acid 5 g/L urea

2 g/L Kerallon GET

SQUEEZING Degree of squeezing, DS=5 %

DRYING T =120 ºC t= 2 minutes up to a residual humidity = 8-10 %

CURING Temperatures, T= 150-170 °C Time, t=1-3 minutes

RINSING Water at 30 ºC

NEUTRALIZATION 10 g/L Na2CO3, time = 20 minutes, T= 20 ºC

RINSING Water at 30 ºC and then at 20 ºC

DRYING Temperature = 100 ºC


following substances: Pekoflam DPN-1, Cassurit HML, orthophosphoric acid, urea, Kerallon GET, sodium carbonate Tubiguard 66 and Tubicoat HPE.

5.2. Treatment Method

The multi-functional finishing treatment considered in the present study uses a padding-drying-curing. The experimental part required a careful design to process the data using multiple linear regression. Table 2 indicates the recipe for the multi-functional finish.

The substances used in the padding stage have the following characteristics [1, 21, 22]:

• Pekoflam DPN-1 is a fireproofing agent with 1.24 g/cm3 density and 37 mL viscosity at 20 °C; its chemical structure contains phosphorus and can withstand a burning temperature of approx. 455 ºC. It can be used in an acid bath (pH = 4), at room temperature [1];

• Tubiguard 66 is a perfluarinated resin, a cationic product that leads to efficient oleophobization and hydrophobization;

• Tubicoat HPE is a modified cationic melamine resin that improves the effect of the fluorocarbon resin used for oleophobization-hydrophobization and softening;

• Cassurit HML is an anti-crease melamine agent (1,3,5 trazine -2,4,6 – triamine, an etherified methylol-melaminic compound with 50 % concentration and 1.15 g/cm3 density); the agent is linked to the textile material in the presence of an acid catalyst (egg. orthophosphoric acid, also used as a catalyst for the fireproof finish);

• Kerallon GET is a softener introduced to improve the fabric touch after the fireproof finish and reticulation of the textile material; in fact, it is a mixture of non-ionic surfactants [1];

• orthophosphoric acid is used to obtain an acid pH (pH=2.5 – 4.5) and acts as catalyst;

• Urea is a hydrotropic agent that can solubilize hydrophobic compounds in aqueous solutions by means other than micellar solubilization. Urea swells the cellulosic fibers, enhancing the accessibility of the phosphorus-based fireproof agent. The P-N bonds can be formed that are reactive to cellulose, even creating a crosslinked

network in cellulose, inhibiting the release of volatile combustible gases and promoting the formation of char [22]. Without urea, the finished fabric has an oily touch.

All these substances may contribute to the formation of multi-functional finish of fireproof + oleophobization + anti-soil + anti-crease. The study also considers their compatibility and efficiency.

5.3. Experimental Design

The experimental design was defined according to the multiple regression plan.

The experimental design requires the identification of the most important factors of influence. Analyzing the recipe presented in Table 2, the concentrations of the fireproof agent (Pekoflam DPN-1) and anti-soil/oleophobization agent (Tubiguard 66) as well as the curing parameters (temperature and time) influence the final results of the multi-functional finish.

The following independent variables were selected:

X1 = curing temperature (ºC);

X2 = curing time (minutes);

X3 = concentration of Pekoflam DPN-1 (mL/L);

X’3 = concentration of Tubiguard 66 (g/L).

Two sets of tests were used to characterize the fireproof/anti-crease, respectively anti-soil/oleophobization effect efficiency:

1. set I containing 20 samples tested for fireproofing using X1, X2 and X3 as the independent variables;

2. set II, also 20 samples, tested for anti-soil, oleophobization/hydrophobization and anti-crease using X1, X2 and X’3 as the independent variables;

The codes defined for the three independent variables is presented in Table 3, while Table 4 illustrates the design experiment.

5.4. Studied Effects

After the samples were finished according to the recipes presented in Table 3, the first half was subjected to a burn test (set I), while the other half was tested to evaluate the efficiency of the


antisoil/oleophobization and anticrease treatments (set II).

For each set, the following characteristics were determined:

• the weight increase for the treated samples (in comparison with the initial weight), before testing;

• the increase in thickness after curing (in comparison with the initial thickness);

For burning, the samples were tested according to DIN 53906 (vertical burning)/SR EN ISO 6941- 2004/BS 5852 Section 4 AATCC [15]. The samples were fixed at the upper part of the box, while a constant flame was applied to the fabric for 8 seconds. At the end, the following characteristics were determined:

Table 3: Coding and Definition of Variables X1, X2, X3 and X’3 for the Two Sets of Tests

Test Set Independent variable -1,682 -1 Code 0 +1 +1,682

X1 = curing temperature (ºC) 150 154 160 166 170

X2 = curing time (minutes) 1 1,4 2 2,6 3

I

X3 = concentration of Pekoflam DPN-1 (mL/L) 200 240 300 360 400

X1 = curing temperature (ºC) 150 154 160 166 170

X2 = curing time (minutes) 1 1,4 2 2,6 3

II

X’3= concentration of Tubiguard 66 (g/L) 27 32 40 48 53

Table 4: Experimental Design

X1 Curing temperature

(ºC)

X2 Curing time (minutes)

X3 Concentration of Pekoflam

DPN-1 (mL/L)

X’3 Concentration of

Tubiguard 66 (g/L)

Run

Codes Real values Codes Real values Codes Real values Codes Real values

1 -1 154 -1 1,4 -1 240 -1 32

2 1 166 -1 1.4 -1 240 -1 32

3 -1 154 1 2.6 -1 240 -1 32

4 1 166 1 2.6 -1 240 -1 32

5 -1 154 -1 1.4 1 360 1 48

6 1 166 -1 1.4 1 360 1 48

7 -1 154 1 2.6 1 360 1 48

8 1 166 1 2.6 1 360 1 48

9 -1.682 150 0 2.0 0 300 0 40

10 +1.682 170 0 2.0 0 300 0 40

11 0 160 -1.682 1.0 0 300 0 40

12 0 160 +1.682 3.0 0 300 0 40

13 0 160 0 2.0 -1.682 200 -1.682 27

14 0 160 0 2.0 +1.682 400 +1.682 53

15 0 160 0 2.0 0 300 0 40

16 0 160 0 2.0 0 300 0 40

17 0 160 0 2.0 0 300 0 40

18 0 160 0 2.0 0 300 0 40

19 0 160 0 2.0 0 300 0 40

20 0 160 0 2.0 0 300 0 40


• char length (length of the carbonized area for the tested samples, cm);

• weight loss (%);

• modification of color after treatment.

For anti-soil and oleophobization, the tests were carried out in the following manner: a drop of aqueous or oily soil was applied on each sample form set II and it was measured the duration of its absorption by the treated sample. The efficiency of the finishing treatments was evaluated for:

• anti-soil effect (for soda drink);

• oleophobization effect (sunflower oil);

• certain alcohols (ethylene glycol and respectively ethanol).

All results for both set of samples were coded using Y when processed using the multiple linear regression.

6. RESULTS

In the case of multiple linear regression with 3 independent variables, the equation describing the behavior of each dependent variable (the effects of the multi-functional finish) is (1):

Y=b0+b1X1+b2X2+b3X3+b12X1X2+b13X1X3+b23X2X3+b11X12+b22X22+b33X32 (1)

where:

• Y is the dependent variable (each effect obtained after finishing);

• X1, X2 and X3 are the independent variables (Table 3);

• b0, b1, b2, b3, b12, b13, b33, b23, b11, b22 and b33 are the coefficients of the polynomial equation; they were determined using multiple regression on a central composite design. These coefficients show direct or indirect influences:

1) direct influence (bi>0 meaning b1>0, b2>0, b3>0);

2) inversely proportional influence (for factors for which bi <0);

3) the presence of a minimum or maximum that express the behavior of the 100 % cotton fabric

after the finishing treatment (minimum: b11>0, b22>0 and b33>0; maximum: b11<0, b22<0 and b33 <0).

Each mathematical equation was validated using two tests:

1. Student test (testing the significance of each regression coefficient);

2. Fisher test (testing the adequacy of each mathematical model).

The Student test demonstrated that all coefficients are significant, and therefore the independent variables (X1, X2 and X3) have a strong influence on the dependent variables (Y, the effects of the multi-functional finish).

The existent stationary points (the optimum of the mathematical equation) were determined by annulling the derivatives of each model.

6.1. Add-on Degree

In order to evaluate the efficiency of the impregnation stage, a characteristic called “add-on degree” was defined.

The degree of add-on (DA) was calculated with relation (2):

DA= [(mf -mi)/ mf] x 100 (%) (2)

where:

mf = final sample weight, after curing (g);

mi = initial sample weight, before curing (g).

Considering that the initial weight of each sample varied in the 1.5-1.6 g range, the increase in weight and thickness (Table 5) was 21.75 % - 33.87 % for DA. Weight loss in the 0.37 % -2.66 % range (Table 5) was determined after the burn test.

Table 5 indicates that all fireproofed samples have increased weight and thickness in comparison with the control values, due to the presence of substances from the impregnation bath.

6.2. Char Length

The untreated cotton sample burned completely, with flame and afterglow. Figure 1 shows the aspect of the treated samples after the burn test.


Table 5: Treated Sample Characteristics, before and after the Burn Test

Before burning After burning Sample no.

Mass increase (g) Diameter increase (mm) Weight loss (%)

control - - total

1 0.485 0.09 2.66

2 0.448 0.16 1.81

3 0.511 0.15 1.31

4 0.456 0.25 1.41

5 0.670 0.17 0.86

6 0.684 0.16 0.41

7 0.664 0.08 0.42

8 0.648 0.12 0.84

9 0.770 0.06 0.40

10 0.770 0.30 1.19

11 0.861 0.14 0.37

12 0.482 0.15 1.35

13 0.522 0.23 1.76

14 0.684 0.20 1.23

15 0.484 0.11 1.34

16 0.489 0.12 1.84

17 0.489 0.12 1.84

18 0.489 0.12 1.84

19 0.489 0.12 1.84

20 0.489 0.12 1.84

Figure 1: Aspect of fireproofed samples after burning.


Figure 2: Planar variation of the char length with each variable.

Figure 3: Response surface for the variation of the char length and contour plot.


Figure 4: Variation of the crease recovery angle with each independent variable X1, X2 and X3.

Figure 5: Response surfaces for the variation of the crease recovery angle and contour plots.


The mathematical model describing the burn

behavior of the fireproofed samples, respectively the char length (cm) is given in equation (3):

Y=1.0751+0.0809X1+0.0322X2–0.0977X3-0.0250X1X2+0.10X1X3+0.2250X2X3+ 0.0108X12 + 0.0461X22+0.1698X32 (3)

This relation indicates that the char length presents a point of minimum for X1 = 164.2364 °C, X2= 2.8094 minutes and X3= 263.0263 mL/L Pekoflam DPN-1, while the Y value for this optimum is Y minimum = 1.1349 cm.

Figures 2 and 3 show the dependence of the char length on the independent variables X1, X2 and X3.

The presence in the impregnation bath of Cassurit HML determines a good anti-crease effect. Cassurit HML is a melamine anti-crease agent that is fixed on the cellulosic material, in the presence of a catalyst, such as orthophosphoric acid, generating a reticulation network.

The mathematical model illustrating the influence of the independent variables (X1, X2 and X3) on the crease recovery angle determined for the treated samples is given in equation (4):

Ymax = 201.8607 + 1.8724X1 + 2.2283X2 + 0.2895X3 + 1.8788X1X2 - 8.9612X1X3 + 2.5888X2X3 - 14.0705X12 - 4.6727X22 - 3.0519X32 (4)

This equation suggests that function Y (crease recovery angle) has a maximum point (Y maximum = 202.2177 °) for X1= 160.5399 °C, X2 =2.1487 minutes and X3= 298.5852 mL/L PeKoflam DPN-1. Figures 4 and 5 indicate variation of the recovery angles with each independent variable and the response surface and contour plot.

6.3. Color Modification after the Fireproof Treatment

The multi-functional finishing treatment leads to small variations of the CIELab measurements, as it results from Tables 6 and 7. The significance of the analyzed CIELab measurements is: L* represents lightness/luminance, C* saturation/chroma, while H* hue [23, 24].

Table 6 shows that the values of lightness L*, saturation C* and hue H* differ than the ones for the control sample, the fabrics turning darker, with green-blue shades.

Table 6: The CIELab Values for the Treated Samples

Sample no. L* Lightness C* Saturation H* Hue

control 37.712 11.752 252.933

1 36.768 13.652 267.040

2 37.351 19.933 267.851

3 37.257 13.915 267.544

4 38.325 13.946 267.911

5 36.353 13.404 266.977

6 36.736 13.729 267.983

7 36.455 13.716 267.796

8 38.164 13.724 268.030

9 36.059 13.794 267.699

10 37.662 13.598 267.581

11 36.239 13.574 266.715

12 38.287 13.871 267.444

13 37.578 13.662 266.318

14 36.310 13.891 268.132

15 37.526 13.792 267.294

16 37.289 14.134 267.669

17 37.289 14.134 267.669

18 37.289 14.134 267.669

19 37.289 14.134 267.669

20 37.289 14.134 267.669


The data from Table 7 indicate:

• dL*< 0 shows a darker color;

• da*> 0 shows the samples have a redder shade;

• db*< 0 shows the samples have a bluer shade;

• dC*> 0 shows the difference saturation/chroma is bigger than the control sample;

• dH*, hue difference is in general “darker less green bluer”.

• dE* varies between 3.139 and 3.713, and color difference dE* < 4 shows acceptability between the treated and control samples. dE* is the most representative value for color difference as it considers the existing differences for lightness dL*, saturation dC* and hue dH* [23, 24]. Equation (5) is used to calculate dE* as presented in [23, 24]:

dE*= [(dL*)2 + (dC*)2 + (dH*)2] ½ AN units (Adams – Nickersen) (5)

6.4. Anti-Soil

The anti-soil and oleophobization effects are illustrated in Figures 6 and 7. The spherical drops on the tested samples (set II) correspond to the following sources:

- row 1: soda drink;

- row 2: sunflower oil;

- row 3: ethylene glycol (antifreeze);

- row 4: Dracila extract, in ethanol.

Figures 6 and 7 show that all 16 samples presented in the images are phobic to the drink (soda drink), including the control sample. The soda drink drops were absorbed after 2 hours.

Table 7: The Values for the Color Differences

Sample no. dL* da* db* dC* dE* dH* Observations

1 -0.831 2.436 -2.133 1.690 3.342 2.761 Darker less green bluer



4 0.541 2.609 -2.423 1.973 3.601 2.964 Lighter less green bluer






10 -0.041 2.551 -2.101 1.654 3.305 2.862 Less green bluer












Figure 6: The anti-soil and oleophobization tests for the first 8 samples from Set II; 0 represents the untreated sample (control sample).

Figure 7: The anti-soil and oleophobization tests for samples 9-16 from Set II.

Figure 8: Variation of the absorption time for the pigment drops dissolved in ethanol with the independent variables X1, X2 and X3


Figure 9: Response surfaces for the variation of the absorption time for the pigment drops dissolved in ethanol and contour plots.

In contrast, the drops from rows 2 and 3, of oil and ethylene glycol/antifreeze, were not absorbed, even after 1 week, indicating that the oleophobization is permanent. The selected treatment recipe ensures permanent anti-oil effects.

The pigment drops (Dracila/berberine) dissolved in ethanol were absorbed after 5 to 20 minutes. Using regression and the total absorption times, the minimum absorption time for the cotton fabric is modeled in equation (6).

Y=6.9133-1.4417X2+1.6114X3-2.7500X2X3+ 0.9267X12+0.7500X22+0.5732X32 (6)

The Y function describing the absorption time for the pigment dissolved in ethanol presents a minimum Ymin = 6.3028 minutes, while the values of the independent variables are X1 = 160 °C, X2=2.4648 minutes and X3 = 39.2435 g/L Tubiguard 66. The variations of Y with each independent variable and the response surfaces are presented in Figures 8 and 9.

CONCLUSIONS

The experimental results allow the following conclusions to be drawn:

Ø The testing of the proposed recipe used in multi-functional finishes for materials used for protective equipment indicates a compatibility of the chemical compounds from the impregnation bath and the resulting multiple effects: fireproof + anti-soil + oleophobization + anti-crease;

Ø The treatment applied to a 100% cotton woven fabric led to an increase in weight and add-on degrees (DA between 21.75% and 33.87 %);

Ø The optimization of the treatment recipe was carried out using statistical methods, more precisely multiple linear regression with 3 independent variables;

Ø Multiple linear regression indicated the following points of optimum:


ο Point of minimum in the case of the char length for X1 = 164.2364 °C, X2= 2.8094 minutes and X3= 263.0263 mL/L PeKoflam DPN-1, while the value of the Y function is Y minimum = 1.1349 cm; small weight losses were determined after the burn test (0.37 % - 2.66 %);

ο Point of maximum in the case of the crease recovery angle (CRA) (CRA maximum = 202.2177 degrees) for X1=160.5399 °C, X2 = 2.1487 minutes and X3= 298.5852 mL/L PeKoflam DPN-1;

ο Point of minimum in the case of the anti-soil effect expressed as the absorption time for a natural pigment (dirt) solved in ethanol (Y minimum = 6.3028 minutes), for X1 = 160 °C, X2=2.4648 minute and X3 = 39.2435 g/L Tubiguard 66;

ο The anti-soil effect lasted for minimum 2 hours for soda drink;

ο The oleophobization effect is permanent, the drops not penetrating the treated samples even after 1 week after exposure.

Ø In conclusion, the simultaneous 4 effects (fireproof + anti-soil + oleophobization + anti-crease) are obtained if the independent values (X1, X2, X3, X’3) are around 160 °C for X1, 2.5 minutes for X2, 263-298 mL/L PeKoflam DPN-1 for X3 and 39 g/L Tubiguard 66 for X’3.

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Received on 25-10-2020 Accepted on 20-11-2020 Published on 03-12-2020

DOI: https://doi.org/10.31437/2415-5489.2020.06.6

© 2020 Popescu et al.; Licensee Scientific Array. This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

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72 World Journal of Textile Engineering and Technology