Report on the 3rd Pilling Round Trial of IWTO Pilling Working Group ...

扫描电子显微镜与光学显微镜鉴 

别山羊绒纤维的技术探讨 

<strong>Report</strong> on the 3 rd Pilling Round Trial 

of IWTO Pilling Working Group DTM 

Inner Mongolia Erdos Cashmere Group Co. Ltd 

Yang Guifen

<strong>Report</strong> on the 3rd Pilling Round Trial of IWTO 

Pilling Working Group DTM 

引言: 

Abstract 

� Indicative Summary to IWTO Pilling Round Trials 

� Reason Analysis on Factors Affecting Precision of the 

Test Results in ICI Pilling Box Method 

� Recommendations

<strong>Report</strong> on the 3 rd Pilling Round Trial of IWTO 


� Brief Introduction to IWTO Pilling Round Trials 

Altogether 3 IWTO International Pilling Round Trials were organized so 

far, the 1 st one was carried out according to the Working Group Draft 

in 2006/07 organized by IWTO Pilling Working Group. 12 laboratories 

participated in that round trial, the detailed results and analysis were 

reported to IWTO Edinburgh Congress in 2007 by Working Group 

members. In the following 3 years thereafter, working group members 

have always been researching the different affecting elements that 

leads to scattered testing data and trying to find solutions. The 

Working Group Draft was modified several times afterwards. The 2 nd 

IWTO Pilling Round Trial was carried out in 2009/10 based on 

preparation works made by IWTO Pilling Work Group. The 3 rd is 

organized in 2010/11 after pilling Photograph Standards were 

developed by China Inner Mongolia Erdos Cashmere Group. The 

2010.05 version of the Pilling DTM was modified according to test 

results of The 3 rd IWTO Pilling Round Trial, which results in the 2011.05 

Version of Working Group DTM.



� Samples and Tests of the 3 rd Round Trial 

Total 12 knitted fabrics were supplied to each of the 6 

participating laboratories. 6 out of the 12 samples are 100% 

wool or wool blended and the other 6 100% cashmere fabrics, 

3 worsted and the other 3 woolen fabrics in each group, 

representing high, medium and low pilling propensity levels 

respectively. Each laboratory was supplied with a copy of 2010 

Version of IWTO Pilling Working Group DTM, together with a 

copy of Instructions to the Round Trial to carry out the tests.



� Experiment Design 

Each sample is required to be tested twice both at 2 and 3 

hours or2 and 4 hours correspondingly(3-hour test for pure 

cashmere fabrics and 4-hour test for wool or cashmere/wool 

blended fabrics). Pilling conditions of cashmere and cashmere 

blended fabric specimens are assessed by comparing with 

Pilling Photographic Standard for Cashmere Knitted Fabrics; 

Pilling grades of pure wool fabrics are assessed by comparing 

with Photographic Standard: SM54 Lambswool.

95% Confidence Interval 



� Relationship between Confidence Limit 

and Pilling Grade from the Round Trial 

2.5 

2 

1.5 

1 

Combined Ratings 

y = -0.5126x2 + 2.6812x - 1.4438 

R2 0.5 

0 

= 0.5075 

1 1.5 2 2.5 3 

Mean Rating 

3.5 4 4.5 5 

Figure 1. Relationship between 

Confidence Limit and Pilling 

Grades in 2006/07 Round Trial 

95% Confidence Limits 

2 

1.5 

1 

0.5 

0 

y = -0.2727x 2 + 1.5487x - 0.8475 

R 2 = 0.7154 

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 

Mean Pilling Grade 

Figure 2. Relationship between 

Confidence Limit and Pilling 

Grades in 2009/10 Round Trial



� An obvious relationship exists between Confidence Limit and 

pilling grade, which basically is that testing precision is high 

when pilling grades are extremely high or extremely low; 

testing precision is low when pilling grades are between 2~3.5 

Grade. 

95%Confidence Limite 

1.5 

1.0 

y = -0.2023x 2 + 1.0225x - 0.2413 

R 2 0.5 

0.0 

= 0.5894 

0.0 1.0 2.0 3.0 4.0 5.0 

Mean Pilling grade 

Figure 3. Relationship between Confidence 

Limit and Pilling Grades in 2010/11 Round Trial



� Precision value of 2010/11 Round Trial is shown in 

the following Table 1. 

Mean Grade 

1.0 

1.5 

2.0 

2.5 

3.0 

3.5 

4.0 

4.5 

Within-Laboratory 

Variance 

0.002 

0.035 

.0.053 

0.003 

0.057 

0.065 

0.039 

0.022 

Between-Laboratory 

Variance 

0.056 

0.154 

0.329 

0.306 

0.207 

0.149 

0.063 

0.11 

95%Confidence 

Limit 

0.5 

0.8 

1.0 

1.0 

1.0 

0.9 

0.6 

0.5



� Reason Analysis on Factors which will influence on 

Precision of Test Results in ICI Pilling Box Method 

� Precision of a test method includes both precision under 

repeatability conditions and precision under reproducibility 

conditions. It’s seen from test results of several Pilling Round 

Trials and statistical results in Table 1 that this test method 

shows a good repeatability but comparatively bad 

reproducibility when pilling grade lies between grade 3.5~ 

grade 2.



� Reason Analysis on Low Reproducibility 

� Considerable works have been done by IWTO Pilling Working Group 

members after the 1 st and the 2 nd Round Trials, trying to figure out 

whether the pilling tester or pilling rating plays greater influence on test 

result differences, including carried out comparison analysis tests on 

two different types of cork linings and polyurethane tubes commonly 

used in various labs; Requiring laboratory that exhibited significant 

differences on pilling grades to evaluate tested specimens from other 

participating labs; sent all tested specimens in total 12 labs to one 

specific lab which organized the round trial for rating etc.. Finally, it’s 

found that differences on pilling grade in different labs are mutually 

caused by both pilling tester and pilling rating.



Pilling Tester elements affects test results in the following 2 

ways: 

1) Polyurethane tubes produced by different manufacturers will have 

significant influence on test result. 

2) Cork linings which are initially put into use or come to the end of its 

service life will have significant influence on test result. 

Pilling Grade Evaluation will affect test result from the 

following 2 points: 

1) Pilling grade evaluators in different testing laboratories formed their 

own particular assessment criteria for a long time, so they will give 

more consistent pilling grades to a whole set of tested specimens but 

larger variation to the pilling grade of a single tested specimen.



For example, Laboratories No. 7 and 9 (labs that exhibited a 

significant difference in reported results) rated 3 full sets of tested 

specimens from other laboratories after 2009/10 Round Trial, Mean 

grade values are shown in Figure 4. 

Rating 

5 

4.5 

4 

3.5 

3 

2.5 

2 

1.5 

1 

0.5 

0 

Mean of all fabrics 

1 2 

Hours 

Figure 4 Mean Grade Rated by 2 Labs to Specimens Tested in 3 Other Labs 

Wherein:Abscissa 1 = 2hrs test 2 = 4hrs test 

Lab 9 

Lab 7



Pilling Grade 

Another example: one laboratory gave significant lower test results to all 

samples in the 2 round trials than all other labs. A specific laboratory was 

selected to carry out ratings on specimens tested in other laboratories to 

investigate whether such differences are caused by pilling tester or by 

pilling grade evaluation. It’s seen from Figure 5and 6 that Laboratory No. 

2 gave generally lower grades to all samples than other labs. 

5 

4 

3 

2 

1 

0 

c1 c2 c3 c4 c5 c6 w1 w2 w3 w4 w5 w6 

Samples 

Lab 1 

Lab 2 

Lab 3 

Lab 4 

Lab 5 

Lab 6 

Figure 5 Test Results of All Participating Labs 

in 2010/11 Round Trial 

Mean Pilling Grade 

4.0 

3.5 

3.0 

2.5 

2.0 

1.5 

1.0 

0.5 

0.0 

2hr 3hr 

Testing time 

4hr 

Lab 1 

Lab 2 

Lab 3 

Lab 4 

Lab 5 

Lab 6 

Figure 6 Mean grade of all participating labs 

in 2010/11 Round Trial



� Ratings given by Lab A to specimens tested in other 3 labs are shown in 

the following Figure 7. It’s seen from Figure 7 that pilling grades rated 

to tested specimens of Lab 2 lie between those rated to Lab 3 and Lab 

4, which means pilling raters in Lab 2 have stricter visual criteria on 

pilling grade rating. 

Rating 

5 

4 

3 

2 

1 

0 

c1 c2 c3 c4 c5 c6 w1 w2 w3 w4 w5 w6 

Tested Samples 

Lab 2 

Lab 3 

Lab 4 

Figure 7. Ratings Given by Lab A to samples Tested in 

other 3 different labs



2) Photographic Standard used in the 2 previous round trials does not 

conform to the actual pilling conditions of tested samples, so little 

reference effects can be relied on, pilling raters in different participating 

labs assessed the pilling grades mainly according to their own 

experiences, which showed greater subjective influence on the test 

results. 

In order to know whether there is any large difference on test results to the 

same set of samples by ICI Pilling Box Method during long time interval, 

the same set of samples are used in the 2 Pilling Round Trials (same 

batch of yarn is used with the same cover factor and finishing 

procedures).



Results of 2 hours test in 2009/10 round trial is 0.5 grade more or less different from 

those in 2010/11 round trial except those of sample W2 and W3. It’s believed after 

analysis, that test results of sample W2 are mainly affected by Pilling Photographic 

Standard (the Photographic Standard affiliated to ASTM D 3512 is used in 2009/10 

round trial, while SM54 Lambswool is used in 2010/11 round trial). Differences on 

test results of sample W3 between these 2 round trials are affected by both sample 

preparation and Pilling Photographic Standard. Pilling grades of sample W1 and W2 

after 4 hours test in 2010/11 is 1 grade lower than those in 2009/10 trial, that’s 

mainly affected by Pilling Photographic Standard. It’s seen from reported data that 

Chinese labs gave significantly different pilling grades to samples W1 and W2 from 

those given by labs out of China. So It is decided that the Pilling Photograph 

Standards developed by Pilling Working Group is adopted in this standard.



� Recommendations 

It’s seen from results of the 3 Pilling Round Trials that precision of 

the pilling test method fundamentally reaches to a reasonable 

level under the active works of the IWTO Pilling Working Group. 

It’s recommended that this Working Group Draft to be 

upgraded to Draft Test Method in efforts to further tackle the 

following issues:



1) Pilling rating relies significantly on subjective assessment of the 

operators. No international round trials on pilling are organized by any 

institute or organization. Each lab has its own pilling assessment style 

and evaluation criteria. This is a very important reason of low 

reproducibility on test results of ICI Pilling Box Method. It’s 

recommended that more pilling round trials are organized among 

international laboratories after the implementation of IWTO Pilling 

Draft Test Method. Like those round trials identifying cashmere wool 

fibers, from which pilling rating orientation may gradually be unified so 

that can greatly improve reproducibility of test results.



2) Calibration procedures to cork lining and polyurethane tube are 

stipulated in detail in IWTO Pilling Working Group Draft Test Method, 

which is significant different from ISO or other countries’ ICI Pilling Box 

Method, but laboratories will not strictly follow such stipulations 

because this Working Group DTM is not a valid standard on current 

stage. Precision of test results between laboratories will be highly 

improved after this test method is implemented.

Thanks for your time and concerns

Report on the 3rd Pilling Round Trial of IWTO Pilling Working Group ...

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