Study on the electrical and surface properties of polyester,polypropylene,and polyamide 6 using pen-type RF plasma treatment

Abstract

The plasma treating process used to adjust the functional groups and modifying surface properties and mechanical behavior is a very important treatment method. Many researches have shown the results, especially in the versatility of polymer material fields. In this study, a pen-type radio frequency plasma system was used to modify the surface of various organic materials, such as polyester, polypropylene, and polyamide 6. Because of the short distance between two stainless steel electrodes, argon has been selected to trigger the plasma. The Taguchi method was used to decide the optimal combinations of the experimental parameters such as argon gas flow amount, plasma irradiation power and time, and the distance between the plasma torch and the organic fabric samples. The L₉ orthogonal arrays were also used to analyze the nine combinations of samples and achieve the optimal results for improving the hydrophilic ability of polyester, polypropylene, and polyamide 6. Then, the analysis of three different types of conductive resin coating on the matrix and surface resistance of the polyester, the 50d fabric type, exhibited much higher conductive ability. After washing, the fabric treated with poly-3,4-ethylenedioxythiophene showed higher decent resistance. The experimental results found that the surface resistivity of the polyester fabric would improve by three orders and the contact angle, until reaching 180°.

Keywords

pen-type radio frequency plasma system hydrophilic ability conductive ability polyester polypropylene polyamide 6

Introduction

The retention of chemical structure and functional groups during pulsed-plasma polymerization was used for producing adhesion-promoting plasma polymer layers with high concentrations of exclusively one sort of functional groups such as OH, NH₂, or COOH [1]. Some of the possible effects are improved hydrophilic properties, an increased chemical reactivity of the fiber surface, an improved adhesion to coatings and to polymer matrices, plasma-induced hydrophobic properties, fiber surface cleaning, etc. [2]. Cold argon plasma treatment also can be used to modify the structure of cellulosic fibers for a variety of applications [3]. The surface oxygen and nitrogen content of the polypropylene fabric increases significantly after treatment in both He and He-O₂ plasmas. There is a slight decrease in nylon fabric tensile strength after treatment in helium plasma [4]. Surface modification in both types of plasma systems results in the surface oxidation, improves polymer wettability and allows the grafting of poly(acrylamide) to activated surface [5].

Recent research, however, has showed that the amount of inert gas currently used cannot be significantly reduced so that the yield efficiency is at a theoretical limit in terms of the mechanism involved [6,7]. Therefore, we propose a different way of studying to decide if inert gas can be used in the plasma treating method to produce roughness surface or generating the side chain from the polymers as those used in the plasma treating method. Such a change would decrease the demand for inert gas and open the way to increasing the yield efficiency. Therefore, argon inert gas in a pen-like RF plasma device was used to investigate the surface resistivity, morphology, and contact angle of polyester fabrics in this study. Of the various parameters evaluated, the radiation distance, flow volume of the inert gas, radiation time, and power were found to have greater influence factors in the pen-type radio frequency plasma treating method (PTRFPTM). Furthermore, modification of the optimum PTRFPTM by modifying the roughness with the plasma under an argon inert environment increased the yield efficiency. Finally, the use of PTRFPTM has modified the need for argon and provided the desired surface properties of the fabrics in higher yield efficiency than what is theoretically possible by the conventional plasma treating method [8–10].

This treating method, however, suffers from two main problems. First, a high quality rare gas was used for modifying the surface properties of the synthetic fabrics that require the use of large volumes of inert gas or mixture. Second, the yield for the treating method under optimized conditions does not exceed 90% and the uniformity of the surface properties of the fabrics is not satisfied for use in garment and industrial fields. Because of the long history and industrial importance of this treating method, much research has been devoted to modify the treating equipment and mixture formula to use less rare gas and to increase the uniformity of the fabric sample as well as to increase the yield efficiency and energy-saving consideration. Therefore, in this study, the pen-like RF plasma was proposed to treat the surface of woven fabrics for improving the surface properties. The effects of yarn specific surface and plasma parameters on the electrical, chemical properties, discoloration of dye solution, and contact angle of polyester woven fabrics were investigated [11,12]. Various types of conductive resin were used to spread on the fabric, which would significantly modify the uniformity and electrical properties of the woven fabrics.

Experimental

Configuration of pen-type RF plasma equipment

An atmosphere pen-type RF plasma system is shown in Figure 1. The pen-type system consisted of a stainless tube surrounded by a ceramic tube. The stainless tube is 150 mm long with an outer diameter of 6 mm. The ceramic tube is 100 mm long with an inner diameter of 8.5 mm. Iron clamps at the top and bottom of the ceramic tube connected the cathode and anode, respectively. Therefore, the stainless tube and the 13.56-MHz RF power were isolated by the ceramic tube. Argon passed through the stainless tube and excited to become plasma torch by RF power [13]. Because of the short distance between two stainless steel electrodes, the easily charged gas should be selected to trigger the plasma. The characteristics of argon are much more easily charged than the other inert gas for pen-like plasma system.

Figure 1.

Atmosphere pen-type RF plasma system.

Hydrophilicity modification experiment design of polyester woven fabric by the Taguchi method

The experiment was designed using the Taguchi method according to the L₉ orthogonal arrays to modify fabric hydrophilicity with optimized parameters, aiming to improve the water contact angle of polyester by 50° or above. Argon was selected to be activated for plasma generation. Parameters were adjusted, including the treatment time of the fabrics, power, distance, and irradiation air flow of the pen-type RF plasma torch. The fabric type tested was polyester 75d/72f and 292 g/m² shielding light fabric with satin weave. The experiment was designed by the Taguchi method according to L₉ (3⁴) and nine combinations of parameters were tested. The orthogonal arrays of Taguchi designs of the polyester-woven fabric are shown in Table 1 [14].

Table 1.

Experimental parameter design of the polyester woven fabric by the orthogonal arrays of the Taguchi method

		Level
	Control factors	1	2	3
1	Irradiation distance (cm)	3	5	7
2	Irradiation air flow (L/minute)	5	10	15
3	Irradiation time (seconds)	10	30	60

Note: The specification of the polyester woven fabric (refer Table 5 – Fabric A).

Hydrophilicity modification experiment design of polypropylene knitting fabric type by the Taguchi method

The experiment was designed by the Taguchi method according to the L₉ orthogonal arrays to modify fabric hydrophilicity with optimized parameters, aiming to improve the water contact angle of polypropylene by 50° or above. Ar was selected to be activated for plasma generation. Parameters were adjusted, including the treatment time of the fabrics, power, distance, and irradiation air flow of the pen-type RF plasma torch. The fabric type tested was 75d/48f polypropylene fabric type with yard weight 180 g/m² knitting fabric. The experiment was designed by the Taguchi method according to L₉ (3⁴) and nine combinations of parameters were tested. The orthogonal arrays of Taguchi designs of the polypropylene knitting fabric are shown in Table 2.

Table 2.

Experimental parameter design of the polypropylene knitting fabric by the orthogonal arrays of the Taguchi method

		Level
	Control factors	1	2	3
1	Irradiation distance (cm)	2	3	4
2	Irradiation air flow (L/minute)	3	5	7
3	Irradiation time (seconds)	10	15	20
4	Irradiation power (W)	150	200	250

Note: The specification of the polypropylene knitting fabric (refer Table 5 – Fabric B).

Hydrophilicity modification of polyamide 6 woven fabric experiment design by the Taguchi m ethod

The experiment was designed by the Taguchi method according to the L₉ orthogonal arrays to modify fabric hydrophilicity with optimized parameters aiming to improve the water contact angle of polyamide 6 by 50° or above. The aging analysis was performed after hydrophilicity modification. Argon was selected to be activated for plasma generation. The fabric type tested was 70d/12f with a yard weight 60.4 g/m² plain woven fabric. The major control factors of experimental design included plasma irradiation distance, irradiation time, irradiation power, and argon gas flow amount. So, the L₉ (3⁴) with four control factors and three levels have been selected. The experiment was designed by the Taguchi method according to L₉ (3⁴) and nine combinations of parameters were tested. The orthogonal arrays of the Taguchi designs of the polyamide 6 plain woven fabric are shown in Table 3.

Table 3.

Experimental parameter design of the polyamide 6 woven fabric by the orthogonal arrays of the Taguchi method

		Level
	Control factors	1	2	3
1	Irradiation distance (cm)	2	3	4
2	Irradiation air flow (L/minute)	3	5	7
3	Irradiation time (seconds)	10	15	20
4	Irradiation power (W)	150	200	250

Note: The specification of the polyamide 6 woven fabric (refer Table 5 – Fabric C).

Aging analysis experiment design of hydrophilicity modification of polyester, polypropylene, and polyamide 6

Aging analysis was performed on polyester, polypropylene, and polyamide 6 after hydrophilicity modification based on the optimized parameters described above. Five time points from respective fabric types were selected after the hydrophilicity modification process. Contact angle was evaluated at different times. The orthogonal arrays of the Taguchi designs of the three different fabrics included polyester, polypropylene, and polyamide 6 are shown in Table 4.

Table 4.

Experimental parameter design of the fabrics A, B, and C by the orthogonal arrays of the Taguchi method

Fabric type	Irradiation distance (cm)	Irradiation air flow (L/minute)	Irradiation time (seconds)	Irradiation power (W)
Fabric A	3	15	60	250
Fabric B	4	5	10	250
Fabric C	3	3	15	250

Note: The specification of the Fabrics A, B, and C (refer Table 5).

The polyester, polypropylene, and polyamide 6 were selected in this article, since they were the most popular ones in the market. The specifications of woven fabrics were shown in Table 5.

Table 5.

Fabric nomenclature of polyester (Fabric A), polypropylene (Fabric B), and polyamide 6 (Fabric C)

Fabric nomenclature	Warp density (epi)	Weft density (ppi)	Warp yarn count	Filling yarn count	Fabric weight (g/m²)
Fabric A	120	80	75d/72f DTY (draw textured yarn)	75d/72f DTY with 1-PLY	292
Fabric B	48 wales	56 courses	75d/48f DTY (draw textured yarn)	75d/48f DTY with 1-PLY	180
Fabric C	116	90	70d/12f DTY (draw textured yarn)	70d/12f DTY with 1-PLY	60.4

Notes: Fabric A: Polyester shield light fabric with woven fabric structure.

Fabric B: Polypropylene plain knitting fabric.

Fabric C: Polyamide 6 plain woven fabric.

Conductivity modification experiment design of polyester-woven fabric by the Taguchi method

75d/72f Polyester woven fabric and three conductive polymers were selected for the conductivity modification experiment to optimize the parameters. Argon was selected to be activated for plasma generation. Parameters for the grafting process were adjusted, including the treatment time of the fabrics, power, distance, and irradiation air flow of the pen-type RF plasma torch as well as the type of the conductive resin. In addition, three extra fabric types of different specifications and processing conditions were also tested. The experiment was designed by the Taguchi method according to L₉ (3⁴) and 27 combinations of parameters were tested. The orthogonal arrays of the Taguchi designs of the polyester-woven fabric with conductive polymers are shown in Table 6.

Table 6.

Experimental parameter design of the polyester woven fabric with conductive polymers by the orthogonal arrays of the Taguchi method

		Level
	Control factors	1	2	3
1	Irradiation distance (cm)	2	3	4
2	Irradiation air flow (L/minute)	5	10	15
3	Irradiation time (seconds)	10	20	30
4	Conductive resin	Hydrophilic polymer	Hydrophobic polymer	PEDOT

Notes: 1. The Specification of the polyester woven fabric (refer Table 5 – Fabric A).

2. Irradiation power was fixed at 200 W.

3. Hydrophilic and hydrophobic resin polymers were polyanilines.

4. PETDOT, poly-3,4-ethylenedioxythiophene.

Experimental equipments

Plasma generator

Type Nos. are Huttinger PFG 300RF (13.56 MHz Plasma Generator) and PFM 1500A (Matching Box). Maximum output power is up to 300 W. This experiment is used to stimulate the plasma on the polyester fabric surface with different specifications for low-temperature plasma treatment.

Contact angle analyzer

Type No. is FTA (First Ten Angstroms)-188(B2EA31). This instrument used ‘drop shape’ analysis to make its measurements. It captures video of liquid droplets and analyzes their shape and size to determine various surface chemistry quantities. Contact angle measurements using the drop shape method in this study are based on Physical Chemistry of Surfaces, Arthur Adamson, ISBN 0-471-61019-4 and Wettability, Berg, ISBN 0-8247-9046-4 [15–17].

Low resistivity meter

Type No. is LPRESTA-EP MCP-HT360 which measures resistivity in a low-resistance range with 4-pin probe meter (measurement range 10⁻² to 10⁶ Ω). In this study, it is used to measure the surface resistance of the fabric and modified evaluation.

Scanning electron microscopes

Type No. is JEOL JSM 7000F which is used to evaluate the complete surface analysis, characterization, and quantitative analysis of the fabric surface property in this study.

Results and discussion

Results of polyester woven fabric hydrophilicity modification

Nine combinations listed in Table 7 were selected for the modification conditions. The contact angles of the polyester woven fabric were measured in the plasma modified and unmodified woven fabrics. Table 7 shows that at 3 cm of irradiation distance, 15 L/minute of argon gas flow amount, 60 seconds of irradiation time, and 250 W of irradiation power, the contact angle lowered from 145.3° to 18.5°, with a decrease of 126.8°, exceeding the goal of a 50° decrease. This result shows that because the structure of the shield light polyester fabric is more compact than those of the two other samples (shown in Table 5), it needs more irradiation energy and air flow rate.

Table 7.

Results of polyester woven fabric hydrophilicity modification

Item No.	Irradiation distance (cm)	Irradiation air flow (L/minute)	Irradiation time (seconds)	Irradiation power (W)	Contact angle (°)
1	3	5	10	150	113.2
2	3	10	30	200	40.7
3	3	15	60	250	18.5
4	5	5	30	250	127.3
5	5	10	60	150	127.5
6	5	15	10	200	125.3
7	7	5	60	200	135.6
8	7	10	10	250	135.9
9	7	15	30	150	120.3
Unmodified fabric sample	145.3°

Note: 1. The specification of the polyester woven fabric (refer Table 5 – Fabric A).

Figure 2 demonstrates that irradiation distance was critical for effective hydrophilicity modification, especially in the range 3–5 cm. Irradiation distance was then subsequently fixed under 3 cm, while other parameters were being optimized. It is probably because the higher irradiation power and distance make the fabric undergo many more reactions with argon fluid that the contact angle of the fabrics was increased, and the power increases with decrease in the contact angle.

Figure 2.

Effect on the S/N ratio of polyester hydrophilicity modification. Note: S/N ratio : fold.

Results of hydrophilicity modification of polypropylene knitted fabric

Nine combinations listed in Table 8 were selected for the modification conditions. The contact angles of the polypropylene knitted fabric were measured in the plasma modified and unmodified knitted fabrics.

Table 8.

Results of hydrophilicity modification of polypropylene woven fabric

Item No.	Irradiation distance (cm)	Irradiation air flow (L/minute)	Irradiation time (seconds)	Irradiation power (W)	Contact angle (°)
1	2	3	10	150	75.9
2	2	5	15	200	63.3
3	2	7	20	250	56.0
4	3	3	15	250	88.9
5	3	5	20	150	46.2
6	3	7	10	200	77.9
7	4	3	20	200	43.6
8	4	5	10	250	20.9
9	4	7	15	150	103.4
Unmodified fabric sample	126.1°

Note: 1. The specification of the polypropylene woven fabric (refer Table 5 – Fabric B).

Table 8 shows that at the 4 cm of irradiation distance, 5 L/minute of irradiation air flow rate, 10 seconds of irradiation time, and 250 W of irradiation power, the contact angle lowered from 126.1° to 20.9°, with a decrease of 105.2°, exceeding the goal of a 50° decrease.

Figure 3 also demonstrates that irradiation distance was critical for effective hydrophilicity modification, and was fixed under 4 cm. The argon flow amount and irradiation time are less than those of polyester-woven fabric. It is probably because the structure of the polypropylene-knitted fabric is less compact than polyester-woven fabric; so, it needs less irradiation energy and treatment time.

Figure 3.

S/N ratio effect of the polypropylene hydrophilicity modification. Note: S/N ratio : fold.

Results of polyamide 6 woven fabric hydrophilicity modification

Nine combinations listed in Table 9 were selected for the modification conditions. The contact angles of 11 test samples (including an unmodified fabric sample and samples for reproducibility evaluation) were measured to determine the optimal combination for plasma-mediated modification.

Table 9.

Results of polyamide 6 woven fabric hydrophilicity modification

Item No.	Irradiation distance (cm)	Irradiation air flow (L/minute)	Irradiation time (seconds)	Irradiation power (W)	Contact angle 1 (instantaneous measurement)
1	2	3	10	150	56.5
2	2	5	15	200	24.1
3	2	7	20	250	28.9
4	3	3	15	250	wet
5	3	5	20	150	11.6
6	3	7	10	200	25.1
7	4	3	20	200	18.5
8	4	5	10	250	29.0
9	4	7	15	150	26.3
Reproducibility	3	3	15	250	Wetting
Unmodified fabric sample	94.5

Note: 1. The specification of the polyamide 6 woven fabric (refer Table 5 – Fabric C).

Figure 4 shows that at the 3 cm irradiation distance, 3 L/minute of irradiation air flow rate, 15 seconds of irradiation time, and 250 W of irradiation power, the contact angle decreased from 94.5° to 0°, with a decrease of 94.5°, exceeding the goal of a 50° decrease.

Figure 4.

The S/N ratio effect of the polyamide 6 hydrophilicity modification. Note: S/N ratio : fold.

Figure 5 demonstrates that the total hydrophilic treatment effects of the polyamide 6 fiber are more significant than polyester and polypropylene fiber. It is because of the higher fiber moisture contents and the functional group (–(CO NH)–) of the polyamide 6 fiber. For the same reason, the hydrophilic treatment effects of the polyester are generally better than polypropylene. The plasma-treated effect in polypropylene is maintained only for 3–4 hours, which is due to the compact fiber structure; so, the follow-up chemical grafting has to finish within 3–4 hours.

Figure 5.

Time point measurement of polyester (PET), polypropylene (PP), and polyamide 6 (PA6) hydrophilicity modification. Notes: The contact angle of original fabric Polyester is 117° The contact angle of original fabric Polypropylene is 110° The contact angle of original fabric Polyamide is 96°.

Time point measurement of polyester, polypropylene, and polyamide 6 hydrophilicity modifications

The major control factors of experimental design included plasma irradiation distance power, time, and argon gas flow amount which would affect the surface and electrical properties of different fabrics. This study tried to modify the surface and electrical properties using plasma treatment, especially the Wettability in that plasma irradiation to influence the ability of the fluid to cover fabric surface, and its degree of order, which also vary with differences in the surface functional groups.

The contact angle was measured using different aging analyses from instantaneous to 5 days using the same control parameters in Table 9 as shown in Table 10.

Table 10.

Aging analysis of polyamide 6 woven fabric hydrophilicity modification

Item No.	Contact angle 1 (instantaneous measurement)	Contact angle 2 (1 day after modification)	Contact angle 3 (2 day after modification)	Contact angle 4 (5 day after modification)
1	56.5	71.8	81.4	87.3
2	24.1	60.7	67.6	79.3
3	28.9	47.4	54.2	79.4
4	Wetting	46.5	57.4	63.8
5	11.6	64.4	67.2	73.1
6	25.1	75.2	79.6	75.6
7	18.5	57.3	61.1	82.6
8	29.0	74.9	79.3	76.8
9	26.3	71.2	72.5	71.2
Reproducibility	Wetting	25.4	56.3	65.8
Unmodified fabric sample	94.5

Note: 1. The specification of the polyamide 6 woven fabric (refer Table 5 – Fabric C).

Figure 6 demonstrates that the significant treatment occurred in Item No. 4. The effects after plasma modification lasted 2–5 days for polyamide 6 fiber.

Figure 6.

Aging analysis measurement of polyamide 6 (PA6) woven fabric hydrophilicity modification.

Results of polyester woven fabric conductivity modification

Twenty-seven combinations listed in Table 11 were selected for the modification conditions. The resistance was measured at five points in the sample fabrics. The maximum and minimum values were plotted to determine the S/N responses.

Table 11.

Results of polyester woven fabric’s conductivity modification

Item No.	Irradiation distance	Irradiation air flow	Irradiation time	Conductive resin	A1 (kΩ)	A2 (kΩ)	B1 (kΩ)	B2 (kΩ)	C1 (kΩ)	C2 (kΩ)
1	2	5	10	A	48	86	150	160	190	160
2	2	10	20	B	2600	3000	900	1200	14	19
3	2	15	30	C	0.73	1.1	0.4	0.7	0.26	0.3
4	4	5	20	C	0.5	0.9	0.26	0.1	0.2	0.5
5	3	10	30	A	36	41	90	170	47	90
6	3	15	10	B	34	57	15	17	7	11
7	4	5	30	B	10,000	6000	11,000	15,000	13	16
8	4	10	10	C	3	8	1.3	0.8	1.8	2.4
9	4	15	20	A	70	110	80	100	160	140

Samples described in Table 11 were washed once following the AATCC 135 standard and the resistance was measured again at five different points on each sample. The maximum and minimum were analyzed in Table 12.

Table 12.

Resistance after washing once in conductivity modified polyester woven fabrics

Item No.	Irradiation distance	Irradiation air flow	Irradiation time	Conductive resin	A1 (kΩ)	A2 (kΩ)	B1 (kΩ)	B2 (kΩ)	C1 (kΩ)	C2 (kΩ)
1	2	5	10	A	–^a	–^a	–^a	–^a	–^a	–^a
2	2	10	20	B	–^a	–^a	–^a	–^a	–^a	–^a
3	2	15	30	C	50	90	42	66	22	35
4	3	5	20	C	35	43	28	65	11	28
5	3	10	30	A	–^a	–^a	–^a	–^a	–^a	–^a
6	3	15	10	B	–^a	–^a	–^a	–^a	–^a	–^a
7	4	5	30	B	–^a	–^a	–^a	–^a	–^a	–^a
8	4	10	10	C	500	800	35	54	5000	6000
9	4	15	20	A	–^a	–^a	–^a	–^a	–^a	–^a

Note: ^aThe measurement value over the limitation of the meter.

Figure 7 shows that the type of conductive resin is critical for the conductivity modification with poly-3,4-ethylenedioxythiophene (PEDOT) being the most effective one. The optimal condition reached at 2 cm of irradiation distance, 15 L/minute of irradiation air flow rate, and 10 seconds of irradiation time with PEDOT. The average responses from each fabric type showed that the fabric type with thinner threads experienced higher modification. In this study, C fabric type (50d Polyester) exhibited much higher conductivity than B and C, regardless of the treatment conditions. The phenomenon could be due to the higher contact surface. After washing once, only fabrics treated with PEDOT still showed decent resistance, whereas PAN-treated fabrics after washing were found to be without any grafted polymers and with an average resistance of >10⁶ Ω, suggesting that no conductivity remained [18,19].

Figure 7.

S/N ratio responses of fabrics A, B, and C. Notes: Unit: Irradiation Distance in cm; Irradiation Rate in Lite/min; Irradiation Time in Second; Resistance in K Ω Conductive Resin A: Hydrophilic PAN; B: Hydrophobic Polyacrylonitrile; C: Poly-3,4-Ethylenedioxythiophene A1 and A2: 75d/72f Polyester Fabric with One Time Calendering B1 and B2: 75d/72f Polyester Fabric with One Time Calendering and Spray Rating C1 and C2: 50d/48f Polyester Fabric with One Time Calendering and Spray Rating.

SEM image analysis of pen-shaped RF plasma conductivity modification

SEM shows that the surface-modified fabrics became less smooth. More conductive polymers could be adhered to the surface of the modified fabrics. The observation agreed with the result that modified fabrics rendered higher resistance [20].

After being modified by plasma irradiation, the conductive resin coating on fabric is much more easily grafted on the fibers, and it is cohesive on the surface layer. Comparing SEM photographs before and after modification, it is observed that the modified fabric surface easily bounded much more conductive resin on fibers. The results are shown in Table 13.

Table 13.

SEM image comparison before and after modification in different fabric types

Fabric type	After finished processing	Conductive resin
Fabric B1	Post- processing a	Conductive resin 1
Fabric B1	Post-processing a	Conductive resin 2
Fabric B1	Post-processing a	Conductive resin 3
Fabric C1	Post-processing b	Conductive resin 1
Fabric C1	Post-processing b	Conductive resin 2
Fabric C1	Post-processing b	Conductive resin 3

Notes: Fabric B1: 75d/72f Polyester; Fabric C1: 50d/48f Polyester;

Post processing a: White Fabrics with one-time burnishing and spray;

Post processing b: Green Fabrics with one-time burnishing and spray;

Conductive resin 1: Poly-3,4-Ethylenedioxythiophene;

Conductive resin 2: Hydrophilic Polyacrylonitrile; and

Conductive resin 3: Hydrophobic Polyacrylonitrile.

Conclusions

The polyester hydrophilicity modification experiment showed (Figure 2) that the irradiation distance was critical for effective hydrophilicity modification; especially in the range 3–5 cm. Irradiation distance should be subsequently fixed under 3 cm, while other parameters are being optimized in terms of cost.

The polypropylene hydrophilicity modification experiment showed (Figure 3) that irradiation power is critical to the optimization, especially in the range 150–200 W. Irradiation power was then subsequently fixed under 200 W, while the irradiation air flow was adjusted to 3 L/m to reach the optimal outcome.

The polyamide 6 hydrophilicity modification experiment showed (Figures 4 and 5) that at 3 cm of irradiation distance, 3 L/m of irradiation air flow rate, 15 seconds of irradiation time, and 250 W of irradiation power, the contact angle lowered from 94.5° to 0°, with a decrease of 94.5°, exceeding the goal of a 50° decrease. It also demonstrated that the contact angle on day 1 after modification increased rapidly and became stabilized on day 2.

The polyester, polypropylene, and polyamide 6 hydrophilicity modification experiments showed (Figure 6) that polyester and polypropylene fabrics experienced rapid changes in hydrophilicity within 1 hour after the modification (short activated period), whereas the change of polyamide 6 occurred 1 hour after the modification (long activated period).

The results of polyester-woven fabric conductivity modification experiment, where parameters were determined by the Taguchi method, showed that C fabric type (50d/48f polyester) exhibited 0.0011–0.0026 MΩ, a much higher conductivity than B and C, regardless of the treatment conditions. The phenomenon could be due to the higher contact surface. After washing once, only fabrics treated with PEDOT still showed decent resistance is 0.011–0.065 MΩ, whereas PAN-treated fabrics after washing were found to be without any grafted polymers, the finding is good as Ref. [21] and the resistivities are 0.139 MΩ (single-warp yarn) and 0.0056 MΩ (double-warp yarn).

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