间规聚苯乙烯及间规聚丙烯结晶研究

【作者】 窦红静；

【导师】 朱诚身；

【作者基本信息】 郑州大学 ， 材料学， 2000， 硕士

【摘要】 八十年代以来，对茂金属佑化剂的深入研究使高间规度聚烯烃的合成成为可能，随之诞生了一系列性能优异、应用前景广阔的聚烯烃新品种，间规聚苯乙烯（s－PS）和间规聚丙烯（s－PP）就是其中令人瞩目的两种。二者均具有复杂的多晶型现象和独特的优良性能。s干S分子中，分于链两旁均匀间隔地分布着侧基苯环，这种有序结构赋予s干S优良的耐热性、耐化学性、结晶性和尺寸稳定性；s干P则具有较高的透明度、耐冲击强度、韧性及弹性。 S干S可划分为四种品型：Q、e、Y和6品型。其中，Q和p晶型具有平面锯齿形链构象，等同周期 0．sin。，（二者又可以不同有序程度的变体存在）； s和6晶型则具有S（2八）2螺旋构象分子链，等同周期0．77urn。s干S结晶的晶型可受结晶方式（熔融或溶液结晶）、压力、退火等多种因素的影响。 S干P结晶也有四种品型：品型 1、11、Ill、IV。其中晶型 1、11均具有 T。G。链构象，晶型1是于一般结晶条件卜所得样品中最稳定的品型，品型11常出现在退火的＊－叮纤维样品中／ 梨m具有平面锯齿形链构象，常出现于冷拉样品中；晶型IV则具有T，G。T币。构象，将晶型IllS干P样品暴露于有机溶剂蒸汽中可得。 S－PS及S－PP均是具有多品型的半品性高聚物，其晶型、品体结构及结晶形态等对加工应用有十分重要的影响，近年来二者结品研究已取得一定进展，但仍存在如下一些薄弱环节。首先，熔体结品在加厂过程中非常常见，但熔体结晶条件对品体结构的影响尚无系统研究；其次，不同品兜之间在升温过程中是否存在晶型转变及如何转变尚无系统研究；此外，对二者非等温结晶动力学过程的处理文献报道较少，且多是以cia。a和Jezioeny方法进行，所得结果不能说明结晶前、后期成核机理的差异；此外，以人球晶存在的S千S 极易具存性脆的缺点，故其聚集态结构对性能有十分重要的影响，但此方面系统研究尚未见文献报道。基于以上儿点，本论文做了如下卜作，以拙对选择合适加工卜艺、提高材料性能提供一定的理论指导。 首先系统研究结晶条什对等温熔体结晶 S干S的影响。发现不同温度（Tc）下结晶所得s千S均为口、6两品型的混合物，高温下结晶有利于p晶型的生成，分子量和间规度的提高有利于形成。品型。晶面间距山。；．、山；；，随＊升高而 －VI－ 增加，do。卜 d。。。、d＊受间规度及分于量影响较人，d门受间规度及分于量影响 影响较小。分于链规整度的提高使S－PS沿各方向结品速率提高。 其次，对S干S 不同条件结晶样品的熔融行为进行了系统研究。发现骤冷样 品冷结晶只形成口品型，冷结晶样品的熔融过程伴随有再结晶现象。冷结晶时间 （t。）与升温速率m）关系为t。二1215．6R“‘”’（S），冷结品温度随R增加而升高， 凸 H。则变化不大。非等温熔体结晶 S－PS 则为口、p两晶型的混合物，缓速降温 有利于生成p品型，且使所得S－PS结品度增加。 此外，在文献基础上设计了较简便方法制得两种溶剂诱导结晶 S－PS：Y、6 晶型c并以变温 X射线衍射和 DSC相结合动态研究了二晶型在升温过程中的晶型 转变。发现在10K／min升温过程中，Y晶型s千S丁190－Z10t发生Y－。转变， 5晶型 S斗S在 150C左心发生 CHCI，；分于的“脱笼”，180－200T和 200－Z15’C 分别发生6－Y和Y－口转变。 另外，还以BOp。X。bCkUfi方法系统研究了 S干S和 S干P的非等温结品动力 学，发现二者非等温结晶过程中 t；。。和 t。、均随降温速率（a）增加呈指数卜降， s－PS、s－PP 的 t；。和 t．，。关系式分别为 b。＝1007a““”t。、t。－＝1102a‘””‘’ t。。。S－PS、S千P非等温结品过种中均存在二次结晶现象，结晶前、后期成核机 理有明显差异。结晶前期二者成核机理受a影响较人，结晶后期s干S 为异相成 核、二维生K：S干P 为二维条带和圆形生K且后划结晶速率人了前期。S干S 和 s－PP的非等温结品活化能分别为382．OKJ／。of和 137．3KJ，mol，s－PS的冷结品 活化能为158．ZKJ／mol。 以偏光显微镜（PLM）和扫描电镜（SEM）研究了S－PS 等温熔体结晶的球品结 构，发现S－PS出昂熔体结品样品随结品温度不同可形成七类球品。220230oC可得 止光性羽毛状球品，其品片较人、堆砌松散，品片沿品核向四周．发散排列：230℃ 以上形成的羽毛状球品则为混光性，其品片细小、堆砌紧密；240℃形成人量八瓣 球品和个别四瓣球品，八瓣球晶与前二者相比品片更为细小且无规排列、相互交 联：此外，230C左心还可能有螺旋品和末品形成。S斗S进行SE＼1观察的刻蚀条 什为：铬酸刻蚀液T 80aC氧化刻蚀 27min。 最后，系统研究了不同条件更多还原

【Abstract】 As two kinds of potential engineering plastics, syndiotactic polystyrene (s-PS) and syndiotactic polypropylene (s-PP) have enjoyed intense industrial and academic interest, due to their good performance and complex polymorphic behavior. In the past, the work in structure of s-PS demonstrated that four different crystalline forms is possible by different processing behavior: a, P, i~ and 6. The crystalline Q and P forms are characterized by chains in the trans planar conformation with an identity period of c=0.Slnm, can be obtained from the melt or the glassy state of s-PS under different thermal condition, whereas the crystalline Y and 6 forms have chains in the S(2/1)2 helical conformation with an identity period of c=0.78nm, are formed under condition where solvents are in vol ~Ted. s-PP presents polymorphism in the solid state, too. It can be divided as four kind of crystalline forms that were named as form I . II , III and IV, respectively. Both form I and II were characterized by chains in helical (TTGG)~ conformation, crystalline form III have chains in trans- planar conformation, and form IV presents chains in a (T6G2T2G2)~ conformation which intermediate between the helical (TTGG)~ and the trans-planar conformation. The research on the crystal of s-PS and s-PP have made progress these years but still need step further in some fields. In this paper, the crystal structure, crystal form transition, melting, morphology and -lx- kinetics was studied by WAXD, DSC, successive WAXD, PLM, SEM and TG, respectively. Based on WAXD diffraction patterns of isothermal melt crystallization, the conclusion that s-PS crystallized from melt contain a and P s-PS. The increasing of T~ and degree of syndiotacticity is benefit to the formation of P and a s-PS, respectively. Crystal plane distance (d) and crystallite dimension is influenced by T~ greatly. The decreasing of cooling rate (a) benefit to the formation of P s-PS. The relation of cool crystallization time (ta) of quenched s-PS and heating rate (R) is calculated as t~12l5.6R0843. The crystal formed within cool crystallization could be only a s-PS, and the melt of it is company with re-crystallization. Two kind of solvent-induced s-PS: v and 6 s-PS was prepared by a new simple way. Corresponding to successive WAXD patterns during heating at 10K/mm of Y and 6 s-PS, y s-PS transform to a s-PS within 190-2100C before melt. 6 s-PS transform to y s-PS at 180-200 憕C and transform continue to a form at 200-2150C. 6 - y and y - a transition is endothermal and exothermal process, respectively. To the nonisothermal crystallization of s-PS, the nucleation mechanism of earlier and later stage is different. The mechanism of earlier stage is influenced by cooling rate greatly, by that Qf later stage is heterogeneous nucleation and three-dimension growing. Energy of nonisothermal and cool crystallization is 382KJ/mol and 158.2KJ/mol, respectively. The m7orphology of melting-crystallization s-PS which has different content of a and P forms was observed by PLM and SEM. There are eight kinds of spherulite formed as crystalline temperature (Ta) changed from 220 0C to Tm. Four-sectional spherulite and eight-sectional spherulites can be obtained when crystallized in higher temperature (T~>2400C). The spherulite is feathered and lamellae structure is bulking As T~ low更多还原