Pilling Tests

Fabric Testing

Textile World Asia Special ReportPilling TestsA look at the various pill-testing methods and
how they compareAn article of clothing should not lose its pristine appearance as a result of
pilling either after being worn for a short time or after being subjected to hard wear.
Well-balanced fabrics show their strengths in daily use, where ultimately the crucial assessment of
the article of clothing is made. This is where the quality of the fiber used with all its
advantages and disadvantages is demonstrated. A final assessment of how low-pilling a fiber is can
thus be made only by testing the textile end product, though only after it has been worn for a
certain period of time because pilling does not start suddenly but passes through several
development stages.By means of rubbing, bending and twisting, the fiber ends are first brought to
the surface of the fabric and then formed into a fairly dense fluffy mass. The pills are produced
from this mass by entanglement of the fiber ends and are held by only a few anchoring fibers — the
life of the pill depends essentially on the flexural strength and ultimate tensile strength of
these anchoring fibers. Whereas these properties have to be accepted as inherent in the case of
natural fibers, they can be tailored to requirements in the case of synthetic fibers.If the fibers
are modified toward reduced pilling susceptibility, the flexural strength and, to a much lesser
extent, the ultimate tensile strength of the polyester fibers are reduced. During the polyester
fiber production process, the flexural strength can be lowered so far that, when the pills that
form are stressed, they soon break off even though the ultimate tensile strength is still markedly
above that of the available natural fibers.This promotes the intended aim of developing fabrics
whose serviceability is unmatched in terms of wear and easy-care properties. In the classic 55
percent Trevira 350/45 percent wool blend, the properties of the wool are complemented by the good
wear and care properties of Trevira 350. Trevira clothing made of this blend offers more than
optimum textile technological properties. Economic arguments too, such as service life and purchase
cost, are supplemented by outstanding wearer comfort.

A comparison of the results from the actual wear test, the random tumble pilling test (RTPT)
and the Martindale test on the Trevira 350/viscose 67/33 (360 gram/linear meter fabric concludes
that the RTPT most closely resembles actual pilling.Common Pill Testing MethodsFabrics made of
low-pilling fibers or in which low-pilling fibers are processed in a blend with wool, cotton,
viscose and other fibers, have proved successful with their optimum wear and care properties.Since
clothing textiles are becoming more versatile, not only in their uses but also in the materials and
finishing methods used, it is becoming increasingly difficult to devise generally valid test
methods reproducing practical conditions with meaningful parameters.RTPT TO DIN 53867In the random
tumble pilling test (RTPT), fabric samples are tumbled by an impeller spinning at 1,200 revolutions
per minute (rpm) and rub against each other and against the cork lining of the chamber. The samples
move about freely and randomly. Inspection and visual assessment of the samples are done after
five, 10, 20, 30, 40, 50 and 60 minutes. Ratings are given based on the nine-step pilling ordinal
scale where nine is the best and one is the poorest. Conspicuousness of the surface change is also
assessed by the five-rating scale to DIN 53867 where one represents no visible change and five
indicates very severe surface change.

Random Tumbe Pilling Tester (RTPT) by SDL AtlasICI PillboxIn the ICI/Hoechst pilling test,
fabric samples are prepared from two fabric pieces sewn together so that one face-side and one
reverse-side of the fabric face outward. A soft rubber sheet is placed between the pieces of
fabric. This composite sample is placed with two soft rubber tubes in a square cork-lined chamber
that rotates around a central axis at 60 rpm. The samples rub against each other and against the
soft rubber tubes and the cork lining of the chamber. Inspection and visual assessment are done
after 16 hours. A series of five photographs illustrate various surface states from no pilling to
very severe pilling.Martindale To DIN 53865Two fabric samples are attached to the sample holder
with a felt pad. The fabric samples rub against each other at a specified test pressure. The
movement of the samples is determined by specifying an abrasion stroke of 24 millimeters and a
movement that forms a Lissajous Figure. Inspection and assessment of the samples are done after
125, 500, 1,000 and 2,000 revolutions. The samples are rated using the five-stage EMPA photo
standard where five represents the best rating and one the poorest rating.

Martindale abrasion tester manufactured by SDL AtlasComparisonThe RTPT method has been in
general use in the textile industry for many years because of its good correlation with practice
and has very largely replaced the ICI Pillbox. The modified Martindale method has, however, been in
use for only a short time for testing pilling properties. It has proved successful in practice as
an abrasion tester and found fairly widespread use. Since the Martindale pilling test method has
been in use for only a short time, whereas the RTPT pilling test method has been employed for many
years, it is reasonable to compare these two methods and to investigate their correlation in wear
tests.A project was undertaken by Trevira’s Development Group to check the practical relevance of
the test methods. Twenty-one fabrics of different origins and constructions produced by different
weavers were tested. The sole criterion for selection was that the fabric was to be
well-established in the market and that no or only very few complaints had been made about it.

Wear Test ProcedureIn designing the wear tests, it was extremely important to find a group of
wearers who were prepared to wear the articles for six weeks (30 working days) for at least 7.5
hours per day. Since the articles selected were menswear articles, the group of wearers was
composed entirely of men. The wearers differed greatly in build, clothing size and fields of
activity to ensure as broad an investigation as possible. All trousers were manufactured by one
maker and came in one style.A wear cycle was defined as the period comprising all the required wear
and care days, which amounted to two weeks (10 working days). After one week (five working days)
the trousers were assessed for the first time using the nine-rating pilling ordinal scale (POS)
(DIN 53867). The conspicuousness of the surface change was also visually assessed with the
fivestage scale (DIN 53867). The trousers were then commercially dry-cleaned by a local dry cleaner
and assessed a second time for the effects of cleaning and pressing. At the end of a test, graphs
and a tabular summary of the individual data were produced.Comparison of the wear test results with
the values obtained in the laboratory makes it clear that only the Random Tumble Pilling Test
differentiates the 21 fabrics in the same way as the wear tests.It can be assumed that the degree
of pilling determined in the Random Tumble Pilling Tester corresponds to the greatest surface
change in practical use.Determination of the pilling tendency in the ICI Pilling Tester is not
recommended because the result compared to actual use is virtually or completely unreproducible.
Hightenacity and unmodified polyester fibers, which are no longer used in modern outerwear, are an
exception and give acceptable results that correlate with practice when tested on the ICI Pilling
Tester.The Martindale method to DIN 53865 = ISO CD 12945/2 cannot be recommended generally for
testing the pilling tendency of clothing fabrics. In pilling testing on the Martindale instrument,
where the fabric being tested is used as an abrasion medium, the risk exists of favorable or
unfavorable circumstances cumulating and thus of extreme statements being made with regard to the
fabric’s pilling tendency. Moreover, the pill detachment tendency of the test sample cannot be
determined in the specified test time. No clear assessment of the tested fabrics is possible, and
multiple tests of identical samples show some extreme deviations in results.

Winter 2003