表面结构不同的纳米二氧化硅原位改性聚甲醛的研究

分别选用环氧基纳米二氧化硅（SiO2）(RNSE)和甲基纳米SiO2(DNS)为填料，通过原位聚合法制备了聚甲醛(POM)/纳米SiO2复合材料，采用场发射扫描电子显微镜、热重分析仪、差示扫描量热仪、偏光显微镜和X射线衍射仪对所得复合材料的结构、热稳定性和结晶行为进行了研究。结果表明，纳米SiO2的用量和表面结构不仅影响了其在复合材料中的分散性，而且对复合材料的热稳定性和结晶行为影响显著；当RNSE的用量少于1 %（质量分数，下同）时，其在POM基体中具有较好的分散性，且相对于DNS，RNSE的分散性更好；纳米SiO2加速了POM结晶，减小了球晶尺寸，提高了结晶度，而且RNSE比DNS对POM的结晶具有更显著的促进作用，但纳米SiO2没有改变POM的晶体结构；引入纳米SiO2降低了POM的热稳定性。

Study on In-situ Modification of Polyoxymethylene with Silica Nanoparticles with Different Surface Structures

Polyoxymethylene (POM)/silica nanoparticle composites were fabricated by in-situ polymerization using silica nanoparticles surface-modified with epoxy (RNSE) and methyl groups (DNS) as fillers, and their structure, thermal stability and crystallization behaviors were investigated by scanning electron microscopy, thermogravimetric analysis (TGA), differential scanning calorimetry and polarized light microscopy. The results indicated that RNSE was well dispersed in the POM matrix at the content lower than 1 phr. RNSE exhibited a better dispersibility in the matrix than DNS. The silica nanoparticles could promote the crystallization of POM, thus resulting in the decrease of spherulite size and the improvement of crystalline degree. Compared with DNS, RNSE presented a more effective enhancement on the crystallinity of POM. However, the thermal stability of the composites was reduced by the silica nanoparticles.