Synthesis and study of MPNS/SMA nano-composite

tanning agent

Hui Pan *, Mei Qi, Zhi Jun Zhang

Laboratory of Special Functional Material, Henan University, Kaifeng 475004, PR China

Received 22 October 2007

Abstract

The radical polymerization of maleic anhydride (MA), styrene (ST) with the vinyl groups introduced onto the surface of the

nano-sized silica via solution polymerization method was developed. The methacryloxypropyl nano-sized silica (MPNS) was used

as macromonomer and polymerized with maleic anhydride and styrene by initiating with BPO in toluene. The structure and

properties of MPNS/SMA nano-composite were characterized by FT-IR spectra and TEM. Meanwhile, it was applied as tanning

agent compared with the traditional styrene–maleic anhydride copolymer in leather. It was found that the applied leather had better

quality characteristics with the addition of the nano-sized silica.

# 2008 Hui Pan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Keywords: Nano-composite; Tanning agent; Polymerization; Leather

The styrene–maleic anhydride copolymer tanning agents have been studied a great deal by technologists and

chemists all over the world since the 1970s.The copolymers have been utilized for filling of the tanning and retanning

in the manufacture of leather. It has been found that they have good quality characteristics such as fullness, softness

and grain effects [1]. However, there are few literatures on polymeric nano-composites composed of styrene and

maleic anhydride for making leather in recent years.

As is well known, the nano-composites derived from nano-sized inorganic particles and organic compounds are

promising new functional materials exhibiting specific properties [2,3], such as quantum effects. If the nano-sized

silica particles are dispersed equably and adequately into the resinic materials, the capabilities of the resins will

be improved comprehensively due to their small granularities and high activities [4–6]. The intensities, the

abrasion and the ageing resistant qualities of the materials can be enhanced evidently. For example, the

transparence, intensity, tenacity and ageing resistance of the PST plastic film will be increased with the addition

of nano-sized silica.

In this paper, we have synthesized a new nano-composite material MPNS/SMA and explored its application in the

tannage of the sides of sheep skin. The application test shows that the nano-composite induces the higher shrinkage

temperature and more increased thickness compared with the traditional SMA copolymer after tanning and retanning.

So this is a new type polymeric nano-composite tanning agent with a wide prospect [7].

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Chinese Chemical Letters 19 (2008) 435–437

* Corresponding author.

E-mail address: panhui@henu.edu.cn (H. Pan).

1001-8417/$ – see front matter # 2008 Hui Pan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

doi:10.1016/j.cclet.2008.01.011

MPNS was synthesized by our laboratory. The prepare procedure of MPNS/SMAwas described as follows: MPNS,

ST, MA and dried toluene were charged into a four-neck 250 mL flask, and the mixture was dispersed with ultrasonic

vibrations for 15 min. Then the mixture was heated to 55 8C and BPO dissolved in toluene was dropped tardily and

continuously within 30 min at this temperature. After that, the mixture was heated to 75 8C and stirred for 2 h at this

temperature. Then the mixture was stirred at 85 8C for another 3 h. After cooling the precipitate was filtered and dried

in vacuum at room temperature. The resulting product was neutralized with 5% sodium hydrate solution. The final

product is a pale yellow viscous solution.

The FT-IR spectra of MPNS/SMA nano-composite (Fig. 1a), MPNS (Fig. 1b) and the poly(ST–MA) (Fig. 1c) are

shown in Fig. 1. The bands, 1100 cm�1 of Si–O–C group, 1698 cm�1 of C O, 1652 cm�1 of C C group in the

spectrum of MPNS. The bands of 703 cm�1, 758 cm�1, 1856 cm�1, 1778 cm�1 and 1089 cm�1of Si–O–C group in the

spectrum of MPNS/SMA were the testimonies of the success of the polymerization of ST, MA and MPNS.

In order to study the tanning suitability of MPNS/SMA nano-composite, it has been used both in tanning and

retanning. It is advantageous in the level of application compared with the typical tanning agent of SMA copolymer.

The results of the trials are shown in Table 1. Table 1 shows that MPNS/SMA nano-composite possesses better tanning

and retanning properties than SMA copolymer. The shrinkage temperature of pickled sheep skin can be increased by

17 8C after tanning with MPNS/SMA, which indicates MPNS/SMA combines firmly with collagen. But the

temperature increment begins to reduce with the addition of MPNS, the value reaches the maximum when MPNS

content is 3% in polymer. The nano-composite gives the highest value of 70% increase in thickness showing the filling

capacity and its use as a tanning filling agent. It is also interesting that the increased thickness reduces evidently with

the increasing MPNS. This is probably that the more nanoparticles block the pores embedded the surface of leather and

permeate the leather not easily, so the tanning effect is reduced obviously with the increasing concent of MPNS.

The SEM photographs of pickled sheep skin (a) and the tanned leather by MPNS/SMA nano-composite (b) are

shown in Fig. 2. It is observed that the fasciculus of the tanned leather become unwound after the tanning agents

H. Pan et al. / Chinese Chemical Letters 19 (2008) 435–437436

Table 1

Effects of tanning and retanning leather

MPNS content in polymer (%) Increase in shrinkage

temperature, DTs (8C)

Increased thickness (%)

Tanning Retanning Tanning Retanning

SMA 0 11 3 40.4 27.8

MPNS/SMA-1# 3 17 11 70.0 45.7

MPNS/SMA-2# 5 8 7 35.1 33.3

MPNS/SMA-3# 7 6 4 6.5 2.1

Fig. 1. FT-IR spectra of (a) MPNS/SMA, (b) MPNS and (c) SMA.

permeated the fasciculus. This indicates that the product has certain properties of filling and tanning. That is

determined that the leather has better characteristics of chubbiness and increased thickness after tanning by MPNS/

SMA nano-composite.

As shown in Fig. 3, the fasciculus of MPNS/SMA retanning leather (b) is thinner, curls more greatly and twisted

more loosely than the chrome tanning leather (a). Also the fibre disperses all the better. This shows that the nano-

composite can penetrate into the collagen fibre to reduce the inner friction, then the segment motion becomes more

easily.

In conclusion, a facile preparation procedure of styrene and maleic anhydride grafted onto the surface of the

methacryloxypropyl nano-sized silica via radical polymerization was developed. The applied test showed that the

shrinkage temperature and the thickness of the leather tanned by MPNS/SMAwere evidently improved compared with

SMA. So it is expected to be a new nano-composite tanning agent and used as filler for tanning and retanning leather.

Acknowledgment

The authors thank the Leather Engineering College of Shaanxi University of Science & Technology for the

assistance of the experiments.

References

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[2] K. Yoshinaga, Y. Tani, Y. Tanaka, Colloid Polym. Sci. 280 (2002) 85.

[3] E. Bourgeat-Lami, J. Lang, J. Colloid Interface Sci. 197 (1998) 293.

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[5] P. Liu, J. Tian, W.M. Liu, Q.J. Xue, Mat. Res. Innovat. 7 (2003) 105.

[6] K. Yoshinaga, J. Shimada, H. Nishida, M. Komatsu, J. Colloid Interface Sci. 214 (1999) 180.

[7] J.Z. Ma, X.J. Chen, Y. Chu, Z.S. Yang, J. Soc. Leather Tech. Chem. 87 (2002) 131.

H. Pan et al. / Chinese Chemical Letters 19 (2008) 435–437 437

Fig. 2. SEM images of (a) the pickled sheep skin and (b) the tanned leather.

Fig. 3. SEM images of (a) the chrome tanning leather and (b) the retanning leather.