Pilling Resistance of Fabrics: How to Test and Enhance it?

Piling is the most progressive appearance of small balls of fibers on the surface of textiles, which occur most rapidly on the part where there is the most intense friction, making textiles poor in wearability. So it is of great benefit to make assessments of the textile pilling resistance reasonably and objectively for the exploration and production of qualified textiles. There are numerous test methods for pilling resistance, in the way that simulates the environment where the fabric develops small balls on its surface under the effect of rubbing which occurs in the process of wearing and washing in daily life. As we can see, diverse standards, such as American standards, European standards, Chinese standards, and customer standards, are proposed in response to various demands. Generally speaking, test methods are adopted according to product categories, consumer demand, places of birth, and so on. As a result, test methods vary from nation to nation. The following are the currently popular methods, such as the ICI pilling box method, Martindale abrasion meter method, Random tumble pilling method, Elastic shim method, and Circular locus method. For further consideration, apart from original forms, specimens with other forms can also be utilized to test their pilling resistance. For example, nowadays most consumers tend to grade textiles based on the degree of pilling after washing. Alternately, they are also eager to use a variety of test techniques to evaluate how well fabrics resist pilling after washing.

Figure 1

Test methods for pilling resistance of fabrics

1 ICI pilling box method

The principle of test: three pieces of every kind of square specimen with a certain size should be taken along the warp and weft directions respectively from the fabric under test. Among them, two samples need to be stitched into a tube face-to-face and set on the polyurethane sample tube (the pilling box is displayed in Figure 2) at first with its front face outward. Then, tumble them together in a cork-lined box “9×9×9” and set the test chamber to flip at the speed of 3600 revolutions per hour to satisfy with consumer’s requirements. Finally, take out the specimen and compare it with its original form or standard form in the rating box. Additionally, the degree of pilling can be categorized into five degrees using the aforementioned criteria. The worst is level one while the best is level five. When the outcome lies halfway between two adjacent levels, the fabrics can be considered as half level. And the three test standards that are most frequently utilized are IWS TM 152, GB/T 4802.3, and ISO 12945-1. By adopting this method, the pilling situation can be simulated that textiles rub by themselves or develop friction after contacting other fabrics. This test method can be applied to all types of fabrics. It is primarily applicable to knitted sweaters in the domestic market or exported to the European market.

Figure 2

2 Martindale abrasion and pilling method

The principle of test: Three pairs of circular specimens are initially taken from textiles under test and put respectively in the upper and lower clamping device. Then specimens rub against each other (as depicted in figure 3), according to the theory of Liza Ru curve trajectory friction. Finally, after revoluting a certain number of times, compare it with its original form or standard form in the rating box. Additionally, the degree of pilling can be categorized into five degrees using the aforementioned criteria. The worst is level one while the best is level five. When the outcome lies halfway between two adjacent levels, the textile can be considered as half level. This method is also applicable to all types of fabrics but is mostly used in woven fabrics. It mainly simulates the pilling condition when the fabric itself is rubbed more frequently against each other. The most commonly used test standards are ISO 12945-2, GB/T 4802.2, IWS TM 196, and ASTM D4970. But few buyers apply the American standard ASTM D4970. The fabrics regarded as level 3.5 are commercially acceptable.

Figure 3

3 Random tumble pilling method

The principle of the test: firstly, take three square specimens from the area in the direction of 45°of test specimen. Then dry them after sealing their sides with glue and put them along with a small number of lint shavings (if the JIS L 1076 D3 method is applied, there is no need for the lint shavings) into a tumble ( as displayed in figure 4) with a rotation rate of about 1200 rpm for 30 minutes (some customers require 60 minutes). Finally, compare it with its standard form in the rating box. Additionally, the degree of pilling can be categorized into five degrees using the aforementioned criteria. The worst is level one while the best is level five. When the outcome lies halfway between two adjacent levels, the fabrics can be considered as half level. It mainly simulates the pilling condition when the fabric itself is rubbed more frequently against each other, other things, and fibers. This method is mainly used to test anti fuzzing and pilling performance of textiles in the American market.

Mainly simulate the fabric in the high frequency of friction made by themselves and friction with the outside world and the outside fiber implicated in the pilling issue. This method is used to test the pilling resistance of most fabrics exported to the U.S. There are also some other commonly used standards, such as ASTM D3512, JIS L 1076 D3 method, and CAN / CGSB – 4.2 NO.51.2. The fabrics regarded as level 3.5 are commercially acceptable.

Figure 4

4 Elastic shim method

The principle of test: take three circular samples from the specimen under test, put them on the specimen holder, and fix them with rubber rings. Samples rub against the elastic shim which can be seen in figure 5 under slight pressure. It is mainly for simulating the situation of pilling when the fabric is subject to friction with other things. This method has not enjoyed a wide application. Some buyers choose this method to test the pilling resistance of woven fabrics exported to the U.S. market. They often choose to make the specimen rotate at 300 rpm. The test standard used is ASTM D3514. And the degree of pilling can be categorized into five degrees using the aforementioned criteria. The worst is level one while the best is level five. When the outcome lies halfway between two adjacent levels, the fabric can be considered as half level. The fabrics regarded as level 3.5 are commercially acceptable.

Figure 5

5 Circular locus method

The principle of the test: take five circular samples from the tested specimen and put them on the specimen holder. Affected by constant pressure, the fabric samples and nylon will be fuzzing based on the trajectory of circular motion and then pilling by the relative friction with standard fabrics (shown in figure 6). Besides, choose the appropriate categories of a parameter from the below table. The process of friction needs to be repeated several times. And then based on the above standards, the degree of pilling can be rated into five levels. Level one means the worst and level five points to the best. When the result is between two adjacent levels, it can be evaluated as half level. This method applies to low-stretch filament woven fabrics, knitted fabrics, and other chemical fiber pure or blended fabrics with a test standard of GB/T 4802.1 which is suitable for the domestic market.

Figure 6

Table 1 Parameter Category of samples
Parameter Category	Pressure/N	The number  of fuzzing	The number of pilling	Applicable fabric types
A	590	150	150	Workwear; Sportwear; Tight and thick fabrics
B	590	50	50	Outerwear fabrics made of synthetic filament
C	490	30	50	Quartermaster uniforms
D	490	40	50	Fabrics blended with chemical fiber or interwoven fabrics
E	780	0	600	Combed woolen fabrics, light pile fabrics, knitted fabrics made of short fibers
F	490	0	50	Coarse and sparse wool fabrics, velvet fabrics, loose-structured fabrics

 

Some ways to improve pilling resistance

The introduction of the pilling mechanism of fabrics and test methods for evaluating the pilling resistance of fabrics contributes to forming a comprehensive consideration for manufacturers who plan to develop raw materials or textiles meeting a certain requirement of the pilling resistance. For example, the choices of suitable raw materials and the manufacturing process help to make superior design, performance, and quality with reasonable cost, optimizing the benefit. All measures are taken for the sake of hitting this target. If finished fabrics fail to satisfy the standard, they can not be put into usage and improved to a great extent even though some remedial measures are taken.

1 Weaving production stage

There are some suggestions on how to select the raw materials and process technology during the production stage.

(1) Choosing the proper fibers

For the production of pure spinning staple fiber fabric, you should pay attention to the selection of the raw materials, such as fiber length, uneven rate of coarse and fine, and so on. If the selected fiber is relatively short with a poor uneven rate of coarse and fine, the hairiness of the yarn may increase. And even if what you want to produce are not the chemical fiber blended fabrics (such as cotton, pure viscose, pure wool, and other fabrics), it is less likely to make the uneven rate meet the specified standard.

(2) Choosing a tight tissue structure and the appropriately increased twist of the yarn

For instance, choosing a strand to weave the yarn.

(3) Selecting the appropriate process

The pilling resistance of ring spinning yarn is better than that of air spinning yarn while the pilling resistance of the combed fabric is better than that of coarse combed fabric.

(4)Chemical fibers can be blended with anti-pilling fiber, a kind of short fiber fabric. In the market, there are anti-pilling polyester fiber and acrylic fiber which can improve the pilling resistance of fabrics. The pilling resistance of chemical fiber fabric with round cross-sections is better than that of chemical fiber with shaped cross-sections.

(5) Using chemical methods to modify synthetic fibers by changing the internal structure of the polymer to reduce the fracture strength of the fiber. As a result, the pompoms produced in the way that the fabric is blended with staple fiber fabric will fall off more easily than those produced in the way that the fabric is blended with the conventional polyester fiber. The difference between the two kinds of fabrics can be seen in figure 7.

Figure 7

2 Finishing stage

One question is often asked by consumers: how to improve the pilling resistance of the finished fabrics and ensure fabrics can pass the re-test. Unfortunately, only the finishing process can improve the pilling resistance of the fabric, which has little effect on enhancing it substantially and brings a risk of damaging fabrics. For example, the inappropriate process may destroy the yarn strength and the fabric structure, which causes a decline in the overall strength of the fabric and failure in the fabric’s other performances.

There are some physical methods, such as singeing, shearing, heat setting, and resin finishing to improve the fuzzing and pilling resistance of finished fabrics.

Singeing can significantly remove the fluff on the surface. However, excessive singeing will cause a decline in the fabric strength, hard cloth body, uneven dyeing, and even serious damage to fabric service-ability. Heat setting can enhance the dimensional stability of the fabric while flattening the fabric surface as well as reducing the likelihood of pilling. However, compared with singeing, heat setting has less effect on the improvement of the pilling resistance.

Resin finishing refers to the bonding and fixture of fibers on the surface of the fabrics, internal fibers, and fiber junction by applying the resin coating process. When the fabric is being rubbed, we can not move and tangle the fibers, making it more challenging to develop pilling. But the excessive resin finishing often leads to the fabric feeling hard, but also too light to work and poorly washable.

Two methods are commonly used to improve the pilling resistance of the fabric in chemical means. Biological enzyme finishing is applied to cellulose fibers. Under the effect of such kind of finishing, fibers exposed to the surface of the fabrics will be digested by biological enzymes, making the surface smooth without lints. Mercerization treatment is also an effective way to remove the lints on the surface of the fabric. An anti-pilling agent has a significant enhancement to some specific fabrics.