Evolution of Morphology and Structure During Crystallization and Melting in Syndiotactic Polypropylene

Polypropylene( PP) has developed into one of the most useful plastic materials.Ithas many attractive properties,among them,a relatively low price.It also possesses awide range of possibilities for chemical modification[1 ,2 ] .The structure and morphologyof PP have a directimpacton the final properties. Therefore,there is growing interestinunderstanding the structure and morphology of stereoregular PP[1～ 6] .　For isotactic PP(i PP) ,extensive structural and morphological studies have be…     

Blends of Polypropylene and Syndiotactic 1,2-Polybutadiene:Morphology,Crystallization Behaviors and Mechanical Properties

Morphologies,crystallization behavior and mechanical properties of polypropylene（PP）/syndiotactic 1,2-polybutadiene（s-1,2 PB）blends were investigated.Morphology observation shows the well dispersed domains of s-1,2 PB in PP matrix with the rather small domain sizes from 0.1 to 0.5μm when the s-1,2 PB content increases from 5%to 20%（mass fraction）in the blends,and the phase structure tends to become co-continuous as s-1,2 PB content further increases.Crystallization temperature（Tc）of PP component in the blends is fluctuated with the variation of s-1,2 PB content in the blends.Compatibilization,to some extent,between the two components is inferred from the examination of both morphology and crystallization behavior.Improvement of impact strength of PP toughened by s-1,2 PB becomes significant only in the case of s-1,2 PB content above 20%（mass fraction）.     

间规立构聚丙烯的结晶度研究

Ｎａｔａ等用Ｚｉｅｇｌｅｒ－Ｎａｔａ催化剂首次合成了间规度为～５０％间规聚丙烯，并对其进行了表征，指出其具有（ＴＴＧＧ）２螺旋构象，正交晶系，Ｃ２２２１空间群［１，２］．近年来用茂金属催化剂合成的间规立构聚丙烯（ｓＰＰ）的间规度可达９３％以上，高间规...     

多相聚合物共混过程中的相结构研究及其在线分析

叙述了多相聚合物共混过程中相结构的形成及变化机理,并综术了多相聚合物共混加工在线分析的几种方法。介绍了天津大学自己研制的动态激光背散射在线分析系统。     

间规聚丙烯(sPP)的研究开发进展

对sPP的研究开发进展进行了总结与评,包括间规选择性藏金属催化剂、sPP的结构与性能以及sPP的加工与应用等。分析了新型藏金属催化剂对sPP间规度1结晶性等的影响,表明sPP具有良好的性能和广泛的潜在胜任。文章强调指出;要使sPP成为商业化产品,还需在催化剂负载化、sPP的改性及加工性等方面做深入研究。     

原位X射线研究拉伸过程中间规聚丙烯晶体熔融与晶体取向关系

间规聚丙烯熔体(sPP)淬冷至液氮温度并保持5 min, 于20, 40, 80, 120 ℃下等温退火10 h, 制备出具有不同片晶厚度的样品. 在室温条件下, 利用原位X射线在线研究sPP样品拉伸过程中应力诱导的晶体熔融和晶体取向关系. 结果表明, 在单轴拉伸过程中, 应力导致的晶体熔融和晶体取向同时发生, 即两者在同一应变、 同一应力下同时发生, 这一特性不受片晶厚度的影响. 随着片晶厚度的增加, 晶体熔融和取向需要的临界应力不断增大, 在所研究范围内, 该临界应力的增加和片晶厚度基本呈线性关系. 另外, 随着片晶厚度增大, 样品的弹性模量、 屈服强度和应变硬化模量均有一定程度的增大.     

二次注射成型聚丙烯中剪切诱导连接界面的形态演变

研究了剪切作用对二次注射成型聚丙烯连接界面形态演变的影响.利用偏光显微镜研究了连接界面距离浇口不同区域和不同位置的形态差异,探索了连接界面形态的演变规律,通过改变注射压力和注射速度对其加以验证,并通过DSC分析证实了形态结构的差异.研究表明:剪切作用对连接界面形态的影响显著,在高剪切作用下分子链沿流动方向取向程度高,不利于其规整排列并沿垂直界面方向生成横晶;可以通过注射压力和注射速度来控制连接界面的剪切作用,从而得到具有完善横晶结构的连接界面形态.     

茂金属支化聚乙烯的结构、形态与熔融行为

综述了茂金属支化聚乙烯的形态，结构和熔融行为，详细讨论了支链大小和含量以及分子量对其物理性质的影响。     

间规聚丙烯的多晶型及结晶行为的研究进展

综述间规聚丙烯复杂的多晶型现象以及各晶型的结构特点。并对间规聚丙烯的结晶和熔融行为等方面的研究进展进行了详细的总结。     

拉伸和退火诱导间同立构聚丙烯的构象转变

90年代以来,随着锆和铪茂金属催化剂的出现,人们已能得到高立构度的sPP^[1].由于sPP具有无毒,软硬适中,尤其是在高度结晶时仍具有很好的透明性等优点,越来越受到人们的广泛注意.     

Multiple Melting Endotherms of Syndiotactic Polystyrene in β Crystalline Form

Multiple melting behaviors have been studied extensively. Syndiotactic polyStyrene(SPS), in 6 crystalline form exhibited such phenomena. It was suggested that arecrystallization process occurred since it has been clarified that no other modificationswere observed during the DSC heating scanl. In this study, a series of SPS samples in 0form were prepared by cooling from the melt at various cooling ratesl and the factors thatinfluence the multiple melting behavior of SPS in 0 form were exam…     

Polymorphic Behavior of Syndiotactic Polypropylene Induced by Heat Treatment

The polymorphic behavior of syndiotactic polypropylene (s-PP) crystallized from the melt under different conditions was investigated by means of WAXD and DSC. The isothermal melt crystallization of s-PP proceeded in form I at tc≥ 110℃ and in form Ⅱ at tc≤110 ℃ s-PP crystallized nonisothermally from the melt was the mixture of forms and . With increasing the cooling rate (a), the content of form increased, and the content of form decreased. On heating, at 10 K/min, of quenched s-PP, it crystallized in form at t≤70 , continuing heating resulted in form form transition, which was an endothermal process.     

间规聚丙烯过氧化物在多官能团单体存在下的交联

过氧化物交联;交联动力学;间规聚丙烯过氧化物在多官能团单体存在下的交联     

Morphology Evolution During Polymer Crystallization Simultaneous Calorimetric and Optical Measurements

The crystallization of the isotactic poly(propylene) (I-PP) has been studied carrying out measurements by means of a special calorimeter connected to a microscope and a digital acquisition system of images. To authors' knowledge, this is the first time that simultaneous calorimetric and optical measurements are carried out on polymers. The analysis of Polarized Optical Microscopy images has allowed the appraisal of nucleation density and growth rate in isothermal and non isothermal conditions. The results obtained in isothermal conditions have been analyzed through the Kolmogoroff model and the crystallinity calculated from the model has been compared with that obtained from the calorimetric measurements.     

Crystallization and Melting of β-Nucleated Isotactic Polypropylene

Ca salts of suberic (Ca-Sub) and pimelic acid (Ca-Pim) were synthesized and used as β-nucleating agents in different grades of isotactic polypropylene (IPP). Propylene homo-, random- and block-copolymers containing these additives crystallize principally in pure β-modification as demonstrated in isothermal and non-isothermal crystallization experiments. Ca-Sub proved the most effective β-nucleating agent known, so far. It broadens the upper crystallization temperature range of pure β-IPP formation up to 140°C. The effect of the additives on the crystallization and melting characteristics of the polymers was studied. The degree of crystallinity of the β-modification was found to be markedly higher than that of α-IPP. High temperature melting peak broadening was first observed and discussed in literary results regarding the same phenomenon for α-IPP. This revised version was published online in August 2006 with corrections to the Cover Date.     

聚丙烯釜内合金的相态研究

聚丙烯釜内合金具有良好的刚韧平衡性能,历经30多年的发展,在包装、汽车和建筑等领域已得到广泛的应用。其优异的性能及复杂的多相、多组分结构更是引起了相关领域研究者的高度关注。聚丙烯釜内合金是一种在聚合釜内直接合成的多相、多组分聚合物体系,其初始产品常以粉末或球型颗粒的状态存在,具有非常复杂的相形态,并且在加工成型过程中,由于相形态的演变会形成更加丰富的微结构,从而对聚丙烯釜内合金最终的力学性能产生决定性的影响。目前对于聚丙烯釜内合金体系的分子链结构-聚集态结构-产品性能之间的构效关系仍然有很多问题亟待解决。近期研究表明在某些情况下,聚丙烯釜内合金体系中增韧相形成“核-壳”型结构(或多重“核-壳”型结构)时,可以实现最佳的刚性与韧性的平衡,但对于这些“核-壳”结构形成条件的控制及结构成分的精确测定仍有不足。本文主要总结了近年来聚丙烯釜内合金相态研究的进展,展望了该领域可能的发展方向。     

The Role of the trans-Planar Mesophase in the Polymorphic Behavior of Syndiotactic Polypropylene

The transformations of the trans-planar mesophase of syndiotactic polypropylene (sPP) subjected to thermal, mechanical and solvent treatments, were investigated. The unoriented trans-planar mesophase, obtained by quenching the melt at 0°C, was annealed at 80°C and the thermal transformation was investigated by X-rays, infrared and dynamic-mechanical analysis. The presence of the helical form II was recognized in the annealed sample. The oriented trans-planar mesophase, obtained by drawing at room temperature and releasing the tension, was immersed in liquid dichloromethane for 24 hours. After drying the sample showed the presence of the oriented form II, although it was not possible to exclude a partial transition into form IV. On the basis of the present and literature results we suggested a scheme of the polymorphic transitions of sPP, in which the central role of the trans-planar mesophase is enlightened.     

间规聚苯乙烯的同质多晶现象

间规聚苯乙烯具有复杂的同质多晶现象，有α，β，γ，δ四种晶型和两种介晶型。本文综述了间规聚苯乙烯的晶体结构、晶型转变以及其结晶和熔融行为等方面的研究进展。     

Surface Reaction of Ozone at High Concentration with Isotactic And Syndiotactic Polypropylene

The surface reaction of isotactic and syndiotactic polypropylene (I-PP and S-PP) films with ozone was studied with FT-IR spectroscopy with differential scanning calorimetry (DSC) and making use of 2,2,4-trimethylpentane as a model compound of PP chain segment. I-PP and S-PP were found reactive toward ozone, and it was found that I-PP being more crystalline than S-PP, reacts more slowly with O₃. In fact, the pseudo first rate constant of I-PP with ozone was k’_I-PP = 8.0 × 10^?6 s^?1 while that of S-PP with ozone k’_S-PP = 1.3 × 10^?5 s^?1. However, the DSC study has shown that the ozone attack on I-PP or S-PP films is not selective and simultaneously destroys the amorphous and the crystalline phases. The ozone treated I-PP and S-PP films are much less resistant to the combined thermal and oxidative degradation reaction than the unexposed films. Thus, ozone is a naturally occurring pollutant at the soil level which accelerates the ageing of I-PP and S-PP materials.