Textile Properties of Tussah Silk Fabric by Eco-friendly Crosslinking
Zhimei Liua, Gang Lib, Dehong Chengc*, Yanhua Lud*
1Functional Textile Material Key Laboratory, School of Chemical Engineering and Material Science,
Eastern Liaoning University, Dandong, 118001, P. R. China
Keywords: tussah silk, eco-friendly crosslinking agents, wrinkle resistant property, mechanical property
Abstract. To increase the wrinkle resistant property of tussah silk fabric, the eco-friendly
crosslinking agents of citric acid (CA) was applied to tussah silk wrinkle resistant finishing process.
Tussah silk fabric was treated with a conventional pad-dry-cure method. The finishing effects of
tussah silk fabric including wrinkle recovery angle, whiteness and mechanical properties were
characterized. The finishing agents CA in the presence of catalyst of sodium monophosphate (SHP) as
well as the treatment conditions significantly affected the anti-wrinkle effects of treated tussah silk
fabrics. The treated fabric samples showed increased wrinkle resistant property. The retention rate of
breaking strength and whiteness of CA treatment tussah silk meet to the demands of the fabric
Tussah silk, as a very excellent natural protein fiber, can absorb ultraviolet light and has the property
of resistant to sunlight. It is comfortable to humans skin and has porosity which formed the
textured porosity in tussah fiber[2,3]. However, Tussah silk fiber has inferior properties similar to
those of mulberry silk, such as low wrinkle resistance and deformation for its poor crystallinity and
orientation degree. In order to overcome inferior textile properties, considerable interest in the
improvement of the such as anti-yellowing, wash and wear properties, and crease proofing of the silk
with some kinds of chemicals have been attempted[4-6]. So far, chemical modifications of tussah silk
fibroin are including epoxide-based modifications, polycarboxylic acids, organic silicone,
polyurethane treatment and di-methylol di-hydroxy ethylene urea (DMDHEU) treatment for textile
These chemical finishing agents do improve the durable press of the tussah silk fabric. The
modification result of some treatment agents such as DMDHEU is good, but the agents produced
formaldehyde in the process of finishing and wearing. Therefore, the ecological problems limited its
application in textile [7-9].
In this work, the eco-friendly crosslinking agents of CA agent were applied to tussah silk finishing.
The effects of the technique factors on the results of wrinkle resistant property, retention rate of
breaking strength and whiteness were analysized.
Materials. Tussah silk fabric(Type 5023), CA, sodium monophosphate(SHP), triethanolamine
(TEA), nonionic and softener were chemicals pure agents and purchased from
Sinopharm Chemical Reagent Co. Ltd.
Preparation of CA treatment solutions. CA treatment solution were prepared according the
following formula. The formula of CA treatment solution
Applied Mechanics and Materials Vol. 685 (2014) pp 68-71 Submitted: 26.09.2014Online available since 2014/Oct/27 at www.scientific.net Accepted: 27.09.2014 (2014) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMM.685.68
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In the formula, TEA was added into the treatment agents of CA and SHP. The reason was that the
CA treatment is often caused yellowing of the tussah silk fabric. On the other hand, TEA could
increase the wet wrinkle resistance angles and maintain the strength of the silk fabric in the CA
treatment process. The reason is that the basic property of TEA neutralize the acidic property, the -OH
of TEA could react with COOH of CA. As a result, the crosslinking degree and branched degree
increase a lot. Therefore, the strength decrease was limited. As we all know, the treatment with resin
and CA anti-wrinkle treatment have serious loss of strength. It is very important of application of
TEA for CA treatment.
Tussah silk fabric treatment process with CA. First, the silk samples were dipped into the solution
of BTCA and CA, then treated with above treatment solutions by pad-dry-cure method.
Tussah silk samples were treated with double dip double pad process:
Dipping 5min (90% pick up)
Drying (80 oC, 5min)
Curing (130~170 oC, 1~4min)
Washing40 oC, 10min Dry (80
Wrinkle-resistant properties of tussah silk fabrics treated with CA. Dry wrinkle-recovery angles
of tussah silk fabrics samples were measured according to AATCC Test Method 66-1998 using
YG541A wrinkle-recovery tester (Darong Standard Textile Apparatus Co. Ltd., Wenzhou, China).
The results were characterized by calculated by averaging 10 wrap and 10 weft samples, respectively.
Breaking strength retention rate of tussah silk fabrics treated with CA. The samples were put in
the room (20C, a relative humidity of 65%) for 48 h before measurement. The breaking strength
before and after treatment with CA was tested using Instron 3365 universal testing machine. The
results were obtained by averaging 10 wrap and 5 weft samples, respectively. The retention rate was
calculated according to the following formula.
Breaking strength before treatment Retention rate = 100%
Breaking strength after treatment
Whiteness of tussah silk fabrics treated with CA. Whiteness index of tussah silk fabrics before and
after treatment were measured on a Gretag-Macbeth ColorEye 7000A Spectrophotometer according
to AATCC Test Method 110-1995. Each silk fabrics sample was folded 8 layers, and the results were
obtained by averaging 10 samples.
Result and discussion
Effects of CA finishing on the properties of tussah silk fabric. There are three adjacent carboxyl
groups in each CA molecule. Under the condition of curing temperature, CA becomes anhydride by
dehydration. Then the ester generated by reacting the anhydride with hydroxyl groups of tussah silk
fiber. The carboxyl groups of CA reacts not only the hydroxyl of tussah silk fiber, but also the
hydroxyl triethanolamine. Bridging effect of TEA makes several citric acid molecules connected with
each other, each link of citric acid molecule can react with the hydroxyl, amino and carboxyl groups
of tussah silk molecular, thus forming a three-dimensional crosslinking structure in the fiber, which
will increase the anti-wrinkle effect. The effect of process factors on the properties of CA finishing
tussah silk fabric is shown in Table 1.
Applied Mechanics and Materials Vol. 685 69
Table 1 Effects of the process factors on the properties of CA finishing tussah silk fabric
% Dry immediate
Untreated 131.6 168.8 82.69
Treated 1 8 4 2 130 4 125.7 156.5 90.95 78.94
Treated 2 7 3 1 140 3 129.1 155.8 92.53 80.24
Treated 3 6 5 1 150 2 133.2 165.0 88.88 77.21
Treated 4 7 5 2 160 1 138.3 189.0 90.72 79.68
Treated 5 8 5 2 160 1 129.1 181.3 87.25 74.19
Treated 6 7 5 1 170 1 135.4 176.8 83.77 72.51
From Table 1 we can obtain the follow three analysis.
(1) the wrinkle recovery angle of the treated tussah fabric increases when the concentration of CA
is from 6% to 7%, and decreases when the concentration of CA is 8%. While the wrinkle recovery
angle of the treated tussah fabric increases with the SHP concentration increasing. The breaking
strength and whiteness of the treated tussah fabric decrease with the increasing concentration of CA.
The retention rate of breaking strength decreases to 83.77, the whiteness decreases by 8.5% when the
concentration of CA and SHP reaches the maximum. (2) the wrinkle recovery angle of the treated
tussah fabric increases when the curing temperature is less than and equal to 160oC, and decreases
when the curing temperature is more than 160 oC. The breaking strength and whiteness of the treated
tussah fabric decrease with the increasing of the curing temperature. The retention rate of the breaking
strength decreases by about 7.2% and the whiteness of 10.2%, when the curing temperature is up to
170 oC. (3) the wrinkle recovery angle of the treated tussah fabric reaches to the maximum, and the
breaking strength changes a little from treatment 1 to 5. The breaking strength decreases more when
the concentration is under treatment 6.
The optimum process conditions are determined as follows:
CA concentration 7%
SHP concentration 5%
TEA concentration 2%
Curing temperature 160 oC
Curing time 1 min
Based on the above process condition, the wrinkle recovery angle increases by 20.17o, the retention
rate of breaking strength is 83.77%, whiteness decreases by 3.0%.
Scheme 1 Esterification reaction between tussah silk fiber and CA
70 Machine, Industry and Manufacturing Based on Applied-InformationTechnology IV
Scheme 2 Amidization reaction between tussah silk fiber and CA
The decrease of breaking strength came from the acid action of CA and BTCA[11,12]. The
whiteness of treated tussah silk fabric is attributed to the side reaction of CA, BTCA and tussah
The optimum process conditions are as follows: the CA concentration is 7%, SHP concentration is
5%, TEA concentration is 2%, curing temperature is 160 oC, curing time is 1 min. The wrinkle
recovery angle increases by 20.17o, the retention rate of breaking strength is 83.77%, whiteness
decreases by 3.0%.
This work was financially supported by Chinese Nature Science Foundation [grant number
51343002], Natural Science Foundation of Liaoning Province [grant number 201202081], and the
Project of Functional Textile Materials Laboratory of Eastern Liaoning University.
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Applied Mechanics and Materials Vol. 685 71
Machine, Industry and Manufacturing Based on Applied-Information Technology IV 10.4028/www.scientific.net/AMM.685 Textile Properties of Tussah Silk Fabric by Eco-Friendly Crosslinking Agents Modification 10.4028/www.scientific.net/AMM.685.68