山梨醇衍生物对聚乙烯结晶行为的影响

Effects of Sorbitol Derivatives on Crystalline Behaviors of Polyethylene

分别以山梨醇与对甲基苯甲醛、对乙基苯甲醛、3,4-二甲基苯甲醛为原料,利用缩醛反应机理,合成出3种不同的山梨醇衍生物——1,3-2,4-二亚（对甲基）苄基山梨醇（MDBS）、1,3-2,4-二亚（对乙基）苄基山梨醇（EDBS）、二（3,4-二甲基二苄叉）山梨醇（DMDBS）。使用溶液沉淀法制备含DMDBS、EDBS、MDBS质量分数分别为0.3%的3种粉末聚乙烯（PE）样品;采用X衍射仪、红外光谱仪、偏光显微镜、差示扫描量热仪对其进行了结晶结构及性质考察;用Avrami模型、Kissinger方程计算了各PE样品的结晶动力学参数。结果表明,山梨醇衍生物没有改变PE的晶体结构,保持了PE晶体的稳定性,提高了成核密度,使PE球晶尺寸由65μm平均降至53μm。动力学数据表明,山梨醇衍生物能提高PE的结晶速率,降低结晶活化能,PE的Avrami指数由4减小至3-3.6。在添加量相同的条件下,DMDBS、EDBS和MDBS可分别令PE结晶度提高4.83%、4.42%、1.25%。DMDBS对PE的改性效果最明显,EDBS次之,MDBS最小。

The sorbitol reacts with p-methyl-benzaldehyde,p-ethyl-benzaldehyde,3,4-dimethyl-benzaldehyde respectively to synthesize three kinds of sorbitol derivatives of（1,3-2,4）-di-（p-methyl-benzylidene） sorbitol（MDBS）,（1,3-2,4）-di-（p-ethyl-benzylidene） sorbitol（EDBS） and（1,3-2,4）-di-（3,4-dimethyl-benzylidene） sorbitol（DMDBS） by the aldol condensation reation.Three PE samples were obtained by the addition of DMDBS,EDBS,MDBS at a content of 0.3%.The crystal structures and behaviors of PE and modified samples were investigated by X-Ray diffractometer, FT-IR, polarized light microscopy, differential scanning calorimeter, the crystallization kinetic parameter was then analyzed by using the Avrami equation and Kissinger model. The results show that sorbitol derivatives maintain the stability of PE crystal structure and improve the nucleation density of PE. The spherulite size of PE was reduced from 65μm to 53 μm in average. The kinetic data reveals that the nucleating agents can increase the crystallization rate while decrease the activation energy, and reduced the values of the Avrami exponent of PE from 4 to 3 - 3.6. DMDBS, EDBS and MDBS can increase the crystallinity of PE by 4. 83%, 4. 42%, 1.25% respectively when in the same addition. The crystal nucleation capacity is the most significant for DMDBS, and the least for MDBS.