国外聚合物共混物的研究进展

ADVANCES IN THE STUDIES OF POLYMER BLENDS

阐述了非均质聚合物共混物的结构、性能和形态的内在相互关系,重点介绍了形态的控制、聚烯烃的官能化及增容剂的种类和主要作用,指出目前的研究重点是开发更有效的共混手段及更有效的、多功能的、应用范围更广的增容剂。

The recent progresses in the studies of the polymer blends were reviewed with 75 references . The interrelationship between structure , properties and morphology in heterogeneous polymer blend systems were discribed . Special attention is paid to the controls of themorphology, functionalization of polyolefines and compatibilizers .The new way is to develop compositions that may be processed at elevated temperatures as homogeneous melts from which a rigid reinforcing phase develops when the materials is cooled . Liquid crystalline polymers (LCP) are known to exhibit such reinforcing behavior in its blend with polyethylene glycol terephthalate (PET).It has been shown that , when the dispersed phase formed long threadlike shapes in the melt-spun fibers of HDPE/PS blends , the resultant fibers showed reinforcement .The blends of polyamides and polyolefines are particularly interesting . Because of their strong incompatibility , their mechanical properties are very low .The polyethylene can be photooxidized and then blended with nylon - 6 . The carbonyl groups formed during photooxidating and amine groups in nylon react giving rise to copolymers which stabilize the blends .Graft copolymer may be formed in melten reaction and acts as compatibilizer in blends . The reactive blending of polyamides or polyesters with elastomers containing carboxyl , maleic anhydride or epoxy groups leads to the in situ formation of compatibilizing copolymers and obtains thoughened polyamides or polyesters .Compatibilizers can be added in blends as a third component and may be classified as non-reactive and reactive . Non-reactive copolymers have segments thathave good compatibility with each of the blend components . The effects of the copolymers on phases adhesion , dispersion , morphology and mechanical properties are dependent upon block molecular weight , block type and blending method . In reactive copolymers , segments are capable of forming stronger covalent or ionic bonds with at least one of the blend components . The majority of the blends employ polyamide as one component and copolymers containing anhydride or carboxyl functionality as compatibilizers . Maleic anhydride reactive functionality is particularly effective in tying low-modulus polyolefins and rubber to nylon for increasing toughness .Compatibilization throngh low molecular weight compounds may involve reactions such as crosslinking , grafting , these reaction can also lead to the formation of copolymers . The observed fine morphology and high impact strength are attributed to the presence of a crossliked product at the interface that plays a role similar to that of a block copolymer .Peroxide and silanes are often used in this compatibilizing system .