【作者】 刘婷；

【导师】 张学俊；

【作者基本信息】 中北大学 ， 高分子化学与物理， 2011， 硕士

【摘要】 聚丙烯(PP)因其低温脆性、缺口敏感性和韧性差等缺点限制了PP的广泛应用。解决这一问题的根本方法是通过在PP基体中添加成核剂改善聚丙烯的结晶性能,从而改善PP的热性能和力学性能。本文由原料固体山梨醇分别与苯甲醛、对羟基苯甲醛或对硝基苯甲醛在溶剂环己烷、促进剂无水甲醇和酸性催化剂对甲苯磺酸的作用下发生缩醛反应,制备了三种聚丙烯成核剂1,3-2,4-二苄叉山梨醇(DBS)、1,3-2,4-二(对羟基)苄叉山梨醇(DHDBS)和1,3-2,4-二(对硝基)苄叉山梨醇(DNDBS),采用傅里叶红外光谱仪和熔点测定仪对三种聚丙烯成核剂进行表征。熔点分析表明,三种产物的熔点在175~190℃之间,大于聚丙烯167℃的熔点,能起到提供晶核的作用。本文考察了影响缩醛反应的因素,得到制备三种聚丙烯成核剂的最佳反应条件。实验结果表明,制备三种聚丙烯成核剂的最佳反应条件基本相同,最佳的原料醛醇摩尔比为2.1:1,反应时间为6h、催化剂对甲苯磺酸(TSA)用量为4wt%、溶剂环己烷用量为600wt%,促进剂无水甲醇用量为20wt%,反应温度为65℃。以对二甲苯为溶剂,采用溶液沉淀法将制备的三种聚丙烯成核剂分别与PP制成成核剂质量分数为0.1wt%、0.2wt%、0.3wt%、0.4wt%和0.5wt%的改性PP粉末样品。采用扫描电子显微镜(SEM)和偏光显微镜(PLM)观察改性PP的球晶尺寸和形貌。结果表明,改性PP的球晶尺寸在12～30微米,与纯聚丙烯相比,尺寸均一,排列规整。通过PLM和X射线衍射(XRD)对改性PP的结晶形态和结晶度分析表明,三种成核剂都能很好的诱导α晶的生成,增加PP的结晶度。通过差示扫描量热法(DSC)和热失重(TG)分析表明改性PP的熔融峰温度升高,说明添加成核剂可以改善PP的稳定性,提高PP的分解温度。采用双螺杆挤出机和注塑机制备成核剂含量为0.1wt%、0.2wt%、0.3wt%、0.4wt%和0.5wt%的PP标准样条。用冲击试验机和万能试验机测定标准样条的力学性能。结果表明,三种成核剂都能不同程度的改善PP的力学性能,冲击强度提高9.86～33.10%,断裂伸长率提高13.33～71.11%,拉伸强度增加51.21～69.59%,弯曲模量提高42.46～64.45%,弯曲强度增加56.99～85.34%。通过本实验研究发现制备的三种成核剂DBS、DHDBS和DNDBS的最佳用量都为PP的0.3wt%,其中成核剂1,3-2,4-二(对羟基)苄叉山梨醇(DHDBS)分子结构中含有多个羟基,可以形成多个氢键,有助于增加分子间的氢键作用,它对PP的性能改善效果最优。更多还原

【Abstract】 Due to low-temperature brittlethe, notch sensitivity and toughness of polypropylene (PP) limits its applications. To solve this problem, the fundamental way is which adding nucleating agent into PP matrix improves the crystallization properties of PP, thus improves thermal properties and mechanical properties of PP.In this study, 1,3-2,4-dibenzylidene sorbitol (DBS), 1,3-2,4-di (p-hydroxyl) benzylidene sorbitol (DHDBS) or 1,3-2,4-di (p-nitro) benzylidene sorbitol (DNDBS), acted as nucleating agent, were synthesized by acetal reaction from benzaldehyde, p-hydroxyl benzaldehyde, p-nitro benzaldehyde and D-sorbitol, with p-toluenesulfonic acid as catalyst, cyclohexane as solvent and methanol as accelerating agent. Fourier transform infrared (FT-IR) spectroscopy showed that nucleating agents were synthesized. Melting point tests showed that melting point of three kinds of PP nucleating agent was higher than that of PP.The factors, which effect acetal reaction to improve the yield of the nucleating agent, were discussed in this paper. The results showed that preparation of three kinds of polypropylene nucleating agent had same optimum reaction conditions, that the optimum mole ratio of aldehyde to alcohol is 2.1:1, the reaction time is 6h, amount of TSA is 4wt%,amount of cyclohexane is 600wt%, amount of methanol is 20wt%, and the suitable temperature is 65℃.Blends of PP and nucleating agent at mass percents (0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt% and 0.5 wt%) were prepared using solution precipitation method, respectively. The size of the spherulite, which was studied by scanning electron microscope (SEM) and polarizing microscope (PLM), was decreased. Crystallization Morphology and crystallinity was studied by PLM and X-ray diffraction (XRD). The result showed that three kinds of nucleating agent can induceαcrystal generated and increase the degree of crystallization of PP. The molten peak of PP analysed by differential scanning calorimetry (DSC) were rised. It explains that the crystallinity and crystalline perfect degree of modified PP were increased. Thermo-gravimetric (TG) analysis showed that adding nucleating agent can improve the stability and the decomposition temperature of PP. And optimal amount of three kinds of nucleating agent all were 0.3wt %.Blends of PP and different nucleating agent having different mass percents (0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt% and 0.5 wt%) were prepared using a twin screw extruder and were compression molded by injection molding machine. Mechanical properties of PP were measured using impact test enginery and micro-computer control universal test machine. The result showed that three kinds of nucleating agent can improve mechanics properties of PP in different degree. Impact strength, elongation at break, tensile strength, Young’s modulus and bending strength of PP were increased 9.86~33.10%, 13.33~71.11%, 51.21~69.59%, 42.46~ 64.45% and 56.99~85.34%, respectively .Optimal amount of three kinds of nucleating agent all were 0.3wt %, and properties of PP modified with 1,3-2,4-di (p-hydroxyl) benzylidene sorbitol (DHDBS) are excellent.更多还原