当前位置:文库下载 > 所有分类 > Influence of lanthanum stearate
免费下载此文档

Influence of lanthanum stearate

Polymer Degradation and Stability 94(2009)845–850

Contents lists available at ScienceDirect

Polymer Degradation and Stability

journal homepage:http://www.wenkuxiazai.com

Influence of lanthanum stearate

/locate/polydegstab

In?uenceof lanthanum stearate as a co-stabilizer on stabilization ef?ciencyof calcium/zincstabilizers to polyvinyl chloride

Long Fang, Yihu Song, Xiaonan Zhu, Qiang Zheng *

Department of Polymer Science and Engineering, Zhejiang University, Key Laboratory of Macromolecular Synthesis and Functionalization of Ministry of Education, Zheda Road, Hangzhou 310027, China

a r t i c l e i n f o

Article history:

Received 13November 2008Received in revised form 15January 2009

Accepted 19January 2009

Available online 7February 2009Keywords:

Polyvinyl chloride (PVC)Calcium/zincstabilizers Lanthanum stearate Co-stabilizer

a b s t r a c t

In?uenceof lanthanum stearate (LaSt3) as a co-stabilizer on stabilization ef?ciencyof calcium stearate (Ca)/zincglutarate (Zn)stabilizers to polyvinyl chloride (PVC)at 180 C in air was investigated. The results showed that combination of LaSt 3with Ca/Znstabilizers presented an obvious improvement of stabilization ef?ciencyto PVC compared with the Ca/Znstabilizers. Moreover, addition of LaSt 3to the Ca/Zn stabilizers could signi?cantlyenhance static stability time of PVC. Incorporation of 2phr LaSt 3co-stabilizer to PVC containing 3phr Ca/Znstabilizers resulted in marked increase of onset degradation temperature and reductions in average degradation rate as well as the dynamic storage modulus (G 0) and loss modulus (G 00) at 180 C. In?uenceof Ca/Znratio on tensile strength of PVC in the absence or in the presence of LaSt 3was discussed in detail. At low Ca/Znratios LaSt 3had an obvious improvement in the tensile strength, while at high Ca/Znratios this effect became inconspicuous.

Ó2009Published by Elsevier Ltd.

1. Introduction

It is well known that low thermal stability of polyvinyl chloride (PVC)is a main drawback or limitation for its application. Proper stabilizers must be incorporated in order to restrain the degrada-tion of PVC during thermal processing. In general, the stabilizers are classi?edas lead salts [1], organic tin [2], soap salts [3]and rare earth stabilizers [4]. Stabilizers play the role in stability mainly through absorption of hydrochloric acid (HCl)released from partial PVC decomposition or substitution of labile sites of partially decomposed PVC macromolecules [5]. Application of lead salts and organic tin stabilizers are limited due to their toxicity, even they have high ef?ciencyto stabilize PVC. On the other hand, rare earth stabilizer and Ca/Znstabilizers are restrained because of their low ef?ciency.Except for exploring new kinds of stabilizers such as (natural)polyols [6], saturated polyesters [7], ester thiols [8,9], and intercalated hydrotalcite-like materials [10], a novel nontoxic complex stabilizers with high ef?ciencyhas attracted researchers’interest for PVC processing.

Ca/Znstabilizers have synergistic effect and present favorable stabilization [11–15]. However, Ca/Znstabilizers have some disad-vantages in long-term stability due to their marked ‘‘zinc burning ’’effect. Hence, extrasubstance must be added so as to improve the

*Corresponding author. Tel./fax:þ8657187952522. E-mail address:zhengqiang@http://www.wenkuxiazai.com(Q.

Influence of lanthanum stearate

Zheng).

0141-3910/$–see front matter Ó2009Published by Elsevier Ltd. doi:10.1016/j.polymdegradstab.2009.01.024

ef?ciencyof stabilization. Co-stabilization of some additives with Ca/Znstabilizers such as pentaerythritol and organotin [16], epoxidized sun?oweroil [17], b -diketone [18], polyols [19], hydrotalcites [20], zeolites [21]and inorganic phosphates [22]has been reported. However, no satisfactory stabilization exists in the above auxiliary stabilizers so that the ef?ciencyof the complex stabilizers is not so high.

Rare earth stabilizer has excellent long-term stabilization effect and rare earth compounds, such as tris(mono-i -octylphthalate) [23], stearates [24], citrates [25]and malates [25]have been used as PVC thermal stabilizers recently. The heat-stability time of PVC containing 3phr (perhundred resin) lanthanum tris(mono-i -octylphthalate) is about 40min at 190 C, being longer than that of Ca/Zncomplex and comparable with that of dibutyltin dilaurate [23]. Moreover, rare earth stearates show higher stabilizing ef?-ciency to rigid PVC as characterized by longer incubation period and lower rate of dehydrochlorination as compared with the industrial thermal stabilizers calcium stearate, zinc stearate, butyl stannum mercaptide, phosphite esters, b -diketone and epoxidized sun?oweroil [24]. On the other hand, rare earth citrates exhibit stabilization effect superior to basic lead salt stabilizers while the stabilization effect of rare earth malates is comparable to organic tin compounds [25]. The extrastabilization ability of rare earth stabilizers may be attributed to their ability to change the confor-mation of PVC [26]and to restrain dehydrochlorination [27]so as to bate the chain reaction and exchange the labile functional groups in the PVC backbone chains for other more stable substitutes derived

第1页

免费下载Word文档免费下载:Influence of lanthanum stearate

(下载1-6页,共6页)

我要评论

TOP相关主题

返回顶部