尼龙6与半芳香性非晶尼龙原位共混物的结构与性能

THE STRUCTURE AND PROPERTIES OF AN in situ BLEND COMPOSED OF POLYAMIDE 6 AND A NON-CRYSTALLIZABLE SEMI-AROMATIC POLYAMIDE COPOLYMER

一种半芳香的非晶尼龙共聚物溶解于熔融的己内酰胺中,引发后者负离子开环聚合原位制备尼龙6与非晶尼龙的共混物.与纯尼龙6相比较,此原位共混物的强度与模量显著提高.非晶区呈现单一的玻璃化转变,表明共混物为均相体系,其组分的相容性源于负离子聚合过程中链交换反应引起的共聚.与纯尼龙6相比较,此共混物的熔点与结晶度显著降低.此外,与纯尼龙6只存在α晶不同,共混物中伴生有大量的γ晶.当非晶尼龙含量为20 wt%时,绝大部分晶体为γ晶.然而,共混物中球晶仅有一定程度细化.共混物强度和模量的提高被认为主要源于非晶区分子活动能力降低以及γ晶相对含量的提高.

The molten caprolactam was polymerized by means of anionic ring-opening polymerization in the presence of a non-crystallizable semi-aromatic polyamide copolymer （NSAP） in order to in situ fabricate the resultant polyamide 6 blends with NSAP. The in situ blends exhibit remarkably improved strength and modulus compared with those of the virgin system. The results of the characterization by using scanning electron microscope （SEM） and dynamic mechanical analyzer （DMA） reveal that there exist a homogeneous morphology and single glass transition for the blends. It is suggested that the miscibility results from the interchange reaction during polymerization. The traces of differential scanning calorimeter （DSC） demonstrate that as compared with the virgin system, both the melting temperature and crystallinity for the blends decrease. Wide-angle X-ray diffraction （WAXD） analysis shows that the crystals exist exclusively in α form for the virgin system; however, a drastic increase in the fraction of γ form appears in the in situ blends, e. g., with the addition of 20 wt % NSAP, the majority of crystals is in γ form. However, only a slight refinement of spherulites occurs as observed by polarized optical microscope （POM）. It is indicated that the improvement in the strength and modulus for the blends results from the reduction of molecule mobility and the fraction of PA6 γ crystals as well.