溶剂诱导双酚A型聚碳酸酯快速结晶的研究

聚碳酸酯(PC)热结晶十分困难,但在某些溶剂诱导作用下,其结晶能力能得到显著提高。且诱导剂的种类、溶度参数和极性等物化性质的不同,其诱导 PC 结晶的能力与形态也不同。从溶剂分子在聚合物内的扩散动力学、诱导结晶行为与特性、诱导结晶形态、诱导结晶机理及应用前景等方面对溶剂诱导 PC 结晶的研究工作和理论进展进行了综述。     

聚偏氟乙烯纳米多孔膜结构调控及离子传递特性

在纳微米尺度调控膜孔结构对发展高性能膜分离材料具有重要意义。使用半结晶性高分子材料聚偏氟乙烯(PVDF),利用非溶剂诱导相分离(NIPS)、蒸汽诱导相分离(VIPS)、溶剂蒸发诱导相分离(EIPS)方法,成功制备了不同形貌的多孔膜。提出了根据聚合物的结晶生长机制调控膜孔结构概念,根据溶剂蒸发时间调控结晶生长。利用SEM和BET对膜孔形貌进行表征,XRD和DSC对结晶进行检测,氢离子(H+)和四价钒离子(VO2+)以及其他常用离子的扩散系数表征传质特性。在溶剂蒸发诱导结晶的过程中,随着溶剂蒸发时间的延长,膜断面的球晶比例逐渐增加,最后至球晶完全融合,膜孔结构发生了显著变化,且膜的结晶度和结晶形态随之发生变化,离子选择性能随膜孔尺寸减小而逐渐增大。     

聚偏氟乙烯纳米多孔膜结构调控及离子传递特性

在纳微米尺度调控膜孔结构对发展高性能膜分离材料具有重要意义。使用半结晶性高分子材料聚偏氟乙烯（PVDF）,利用非溶剂诱导相分离（NIPS）、蒸汽诱导相分离（VIPS）、溶剂蒸发诱导相分离（EIPS）方法,成功制备了不同形貌的多孔膜。提出了根据聚合物的结晶生长机制调控膜孔结构概念,根据溶剂蒸发时间调控结晶生长。利用SEM和BET对膜孔形貌进行表征,XRD和DSC对结晶进行检测,氢离子（H⁺）和四价钒离子（VO²⁺）以及其他常用离子的扩散系数表征传质特性。在溶剂蒸发诱导结晶的过程中,随着溶剂蒸发时间的延长,膜断面的球晶比例逐渐增加,最后至球晶完全融合,膜孔结构发生了显著变化,且膜的结晶度和结晶形态随之发生变化,离子选择性能随膜孔尺寸减小而逐渐增大。     

几种新的PET球晶

几种新的ＰＥＴ球晶有关ＰＥＴ球晶形态的研究已有一些报道。一般认为，ＰＥＴ能够形成正常球晶（包括正球晶和负球晶）、反常球晶和混合球晶。以何种形态出现，与结晶条件（如结晶温度、结晶时间、试样干燥程度等因素）有关。我们在实验中发现ＰＥＴ可产生环状和放射状球...     

PBT/PET共聚酯的结晶和熔融

研究了 PBT/PET 共聚酯的球晶形态、等温结晶动力学和热历史对其 DSC 曲线的影响。结果表明:在120℃下,随着共聚酯中 PBT 含量的增加,共聚酯的球晶形态有很大差异,结晶动力学参数 n,k,t_(1/2)~(-1)增大。经不同的温度热处理,共聚酯在 DSC 曲线上出现两个熔融峰。低温峰对应于不完善的结晶,高温峰属于在 DSC 的升温过程中形成的较完善的结晶。     

聚甲醛/聚氧化乙烯晶/晶共混体系溶液结晶行为

研究不同组成配比下的聚甲醛(POM)/聚氧化乙烯(PEO)晶/晶共混体系溶液结晶行为和结晶形态.结果表明:POM和PEO溶于其共同溶剂六氟异丙醇(HFIP),溶剂挥发过程中两组分由于分子链的相互作用,形成不完善结晶,POM在DSC升温曲线中出现熔融双峰,高熔点峰与纯POM熔点峰相同,而低熔点峰则随PEO含量增大而降低.PEO熔点随POM含量增大而降低.偏光显微镜测试表明:当体系中PEO质量含量低于40%时,POM球晶明显,其直径随PEO含量增加而增大,PEO形成碎晶;当PEO质量含量在60%到80%之间,POM先结晶形成较小的球晶,PEO后结晶,并可穿越POM球晶继续生长至布满整个视场.     

溶液结晶中晶体形态与结构调控

综述了化学因素(溶剂和添加剂等)和工程因素(过饱和度,晶种和搅拌等)对溶液结晶中晶体形态与结构的影响,分析了这些因素会影响溶质分子在溶液主体中的聚集形式及其在晶体界面的扩散和吸附过程,进而影响晶体的成核和生长机理及速率,并由此改变最终产品的形貌和结构。调控结晶工艺参数和优化操作条件可得到目标结晶产物。     

聚乳酸结晶的研究进展

综述了自合成以来聚乳酸（PLA）结晶行为研究的主要成果，介绍了PLA的α、β、γ三种晶型结构参数及不同晶型晶体的形成条件，以及PLA球晶、单晶、孪晶、微纤晶和串晶等结晶形态及其形成条件。此外，还介绍了PLA在不同条件下的结晶行为，着重阐述了分子结构、第二组分及温度场、应力场以及辐照等外部因素对其结晶行为的影响。     

聚酯PTT及PTT/PBT共混体系的结晶形态

选取均聚物聚对苯二甲酸丙二醇酯(PTT)及PTT/聚对苯二甲酸丁二醇酯(PBT)共混物为研究对象,以偏光显微镜(POM)和X射线衍射(XRD)为研究手段探讨了均聚物PTT的结晶形态,以及结晶温度、共混物的组成、等温结晶时间等因素对PTT/PBT共混物结晶形态和性能的影响。结果表明,PTT形成环带球晶的条件是155℃,PTT/PBT共混物的结晶尺寸由于PBT的引入而变小,在PTT质量分数小于60%以后就不能产生环带球晶;PTT/PBT共混物结晶时是两个组分各自结晶,并且相互竞争,使其生成环带球晶的关键是结晶组分的结晶速率要和非结晶组分之扩散速率相匹配。     

聚碳酸酯超疏水表面的构建及其表征

采用丙酮溶剂诱导结晶的方法在聚碳酸酯(PC)基片上构建超疏水表面。通过扫描电子显微镜观察发现PC基片表面由微米级球状结构组成,这些微米球状结构表面又存在纳米级微突起,即仿荷叶表面结构。3D表面形貌分析仪测试结果表明PC基片表面粗糙度明显增加。X射线衍射结果证实,在丙酮的诱导作用下,PC分子链发生了二次结晶。经丙酮处理后PC基片表面水接触角为153°,表现出良好的超疏水效果。这种制备超疏水材料的方法简单易行,成本低,具有广阔的应用前景。     

Surface crystallization of poly(ethylene terephtalate) studied by atomic force microscopy

Poly(ethylene terephtalate) (PET) crystallization was shown by atomic force microscopy (AFM) to occur at 85 °C in the first few nanometers near the polymer-air interface. The surface was fully transformed into spherulites after 30 min, while no signs of bulk crystallization were observed by FTIR. All the observed spherulites presented a nucleation centre, indicating that the crystallization process started at the surface of the film. Tapping mode AFM confirmed that the spherulites were not covered by an amorphous layer. The most probable explanation is a decrease of T_g near the surface. Due to the poor crystallization conditions, the constitutive units of the spherulites were small crystalline blocks. By changing the annealing time, it was possible to produce PET surfaces with different surface fractions consisting of semi-crystalline material (spherulites) and amorphous matrix. This provided a controlled surface heterogeneity on the submicrometer scale, with a contrast in terms of stiffness, roughness and swelling by organic solvents.     

PET/PTT合金结晶形态的研究

采用XP-201热台偏光显微镜研究了对苯二甲酸乙二醇酯（PET）/对苯二甲酸丙二醇酯（PTT）合金等温结晶时的结晶形态及影响因素。研究结果表明：随着等温结晶温度的升高,PET/PTT(40/60)合金的结晶诱导期变长;在观察的时间范围内各样品的球晶尺寸随着时间的延长而增大;随着PTT含量的增加,样品球晶的线生长速率增大,球晶尺寸增大;对比不同温度下等温结晶的球晶形态,PET/PTT(100/0)样品在190℃结晶时球晶尺寸最大, PET/PTT(40/60)样品和PET/PTT(100/0)样品在180℃结晶时球晶尺寸最大; PET/PTT(0/100)样品等温结晶时呈现出了复杂的条带球晶。     

Effects of solvents and temperature on spherulites of self-assembled phloroglucinol tristearate

Herein, phloroglucinol tristearate (PhgTS) was used to study the crystallization process due to its unique symmetric structure containing a benzene ring and three aliphatic chains. Spherulites of crystallized PhgTS from four solvents under diverse conditions were analyzed in detail and their formation process was studied. Maltese cross is shown by PhgTS spherulites obtained from aprotic solvents via polarized optical microscopy. In comparison, no Maltese cross can be observed from branch-like crystals formed from protic solvents. Independent on the microscaled morphology, lamellae were found to be the basic blocks constructing both PhgTS spherulites and branch-like crystals, which were formed predominantly by stacked PhgTS molecules. Although differential characters of the solvents did not affect the formation of lamellas, the solvents played a crucial role in the formation of self-assembled microscaled morphologies. In particular, the morphologies of spherulites were strongly affected by the concentration of PhgTS solutions, surrounding temperature and evaporation rate of solvents. Generally, a higher concentration of PhgTS led to more homogeneous spherulites, a lower evaporation rate resulted in more compact spherulites, and a higher surrounding temperature generated preferentially more ring-banded spherulites of PhgTS.     

Enhanced crystallization behaviour and impact toughness of poly(ethylene terephthalate) with a phenyl phosphonic acid salts compound

Low crystallization rate and inherent brittleness characteristics limit the wide application of PET. In this paper, it was found that a low molecular weight Phenyl phosphonic acid salts compound (TMC-210) is a very effective nucleator and can enhance the impact strength very much. So, the effect of TMC-210 on the crystallization behaviour and mechanical properties of poly(ethylene terephthalate) were systematically evaluated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), wide angle X-ray diffraction (WAXD), scanning electron microscope (SEM) and mechanical properties test. The results show that TMC-210 obviously improves the crystallization temperature and accelerates the crystallization rate of PET and reflects a significant heterogeneous nucleating effect with a nucleation efficiency of 99.8 % when introducing a low content of 0.6 wt% TMC-210. The spherulites size and number of blended PET are greater than pure PET. The crystal structure of PET does not change but the blends with high TMC-210 content appears new diffraction peaks in x-ray diffraction spectrogram and it may attribute to the agglomeration of TMC-210 particles, which is verified by SEM observation. The impact fracture surface of PET develops a brittle ductile transition and thus the impact strength of PET improves significantly. Additionally, Lauritzen–Hoffman equation was used to discuss the effect of TMC-210 on the fold surface free energy (σ _e) of PET in the crystallization process and found that the σ _e values of PET/TMC-210 blends is smaller than that of pure PET.     

Effect of shearing on crystallization behavior of poly(ethylene terephthalate)

The shear‐induced crystallization behavior of PET was investigated by measuring the time‐dependent storage modulus (G′) and dynamic viscosity (η′) with a parallel‐plate rheometer at different temperatures and shear rate. The morphology of shear‐induced crystallized PET was measured by DSC, X‐ray, and polarizing optical microscopy. When a constant shear rate was added to the molten polymer, the shear stress increased with the time as a result of the orientation of molecular chains. The induction time of crystallization is decreased with frequency. Moreover, the rate of isothermal crystallization of PET was notably decreased with increasing temperature. The shape of spherulites is changed to ellipsoid in the direction of shear. In addition, aggregation of spherulites is increased with increasing frequency. Particularly, the row nucleation morphology could be observed under polarized light for ω = 1. From the results of DSC, the melting point and enthalpy have a tendency to decrease slightly with increasing frequency. The crystallite size and perfectness decreased with frequency, which was confirmed with X‐ray data. The unit length of the crystallographic unit cell of the PET increased and the (1 0 3) plane peak increased with increasing frequency. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2640–2646, 2001     

苯乙烯-甲基丙烯酸钠离聚物的合成及其对PET结晶行为的影响

采用溶液法制备苯乙烯-甲基丙烯酸钠(SMA-Na)离聚物,研究其对聚对苯二甲酸乙二酯（PET）的结晶及熔融行为的影响。结果表明：SMA-Na是PET的良成核剂,加入1wt %的苯乙烯-甲基丙烯酸钠使PET的熔融结晶温度（Tmc）提高了17.9 ℃,冷结晶温度(Tcc)降低了17.3℃,显著的提高了PET在高温区和低温区的结晶速度。加入离聚物,使得PET球晶变得更加细化完善。     

Effect of photofunctional organo anion-intercalated layered double hydroxide nanoparticles on poly(ethylene terephthalate) nonisothermal crystallization kinetics

Very recently, we report a facile preparation and strong UV-shielding function of poly(ethylene terephthalate) (PET) nanocomposites using 4,4′-diaminostilbene-2,2′-disulfonic acid anion-intercalated layered double hydroxide (LDH_DDA). Herein, the effect of the photofunctional organo anion-intercalated LDH nanoparticles on nonisothermal crystallization kinetics of PET is reported by differential scanning calorimetry technique. First, the nonisothermal crystallization behaviour is discussed by several basic parameters including crystallization peak temperature, relative degree of crystallinity with temperature or time, and half-time of crystallization. Then, Avrami and Jeziorny method, as well as Mo model were applied for the PET/LDH_DDA nanocomposites. Finally, the crystallization activation energy was investigated by Kissinger method and Flynn conversion. The results reveal that the incorporation of LDH_DDA nanoparticles acted as nucleating agent and significantly accelerated the PET nonisothermal crystallization process, whereas had little effect on the three-dimensional growth pattern of spherulites.     

DSC studies on the crystallization characteristics of poly(ethylene terephthalate) for blow molding applications

The crystallization behavior of blow-molded PET bottles, which helps determine the product's transparency, was investigated by DSC dynamic cooling experiments that simulated the cooling that occurs in the injection blow-molding manufacturing process. Dynamic cooling crystallization of PET optimized the conditions for keeping crystallinity to a minimum during the production of PET bottles. The kinetic parameters of non-isothermal crystallization behavior were determined, which indicate that the competing processes of nucleation and the growth of PET spherulites during the cooling process are the controlling factors for the degree of crystallinity in the final product. In addition, DSC measurements were employed to obtain information on related aspects, such as the ease of crystallization from glassy and molten states and the crystallinity in the products. An Avrami equation was used for the calculations of the crystallization kinetic parameters.     

PTT／PET共混体系结晶行为和形态研究

利用差示扫描量热仪、正交偏光显微镜研究了聚对苯二甲酸丙二醇酯(PTT)、聚对苯二甲酸乙二醇酯(PET)及PTT/PET共混体系(质量比为25∶75)的结晶行为、形态和等温结晶动力学。结果表明,PTT/PET共混物中,少量的PTT部分地起到了成核作用,但在一定程度上阻碍了PET链段规则地进入晶格,影响了结晶速率。偏光显微镜观察到PET、PTT和PTT/PET共混物在120℃下1、20min的溶液滴膜有较清晰的球晶。     

PP／PET／EPDM-g-GMA共混物结构与性能研究

通过反应共混制备了PP／PET／EPDM—g-GMA共混物。用扫描电镜和图像处理软件对共混物形貌进行定性和定量分析，用偏光显微镜观察共混物等温结晶形态，最后测量共混物的力学性能。结果表明：在PP／PET共混物中加入EPDM-g—GMA后，两相相容性改善，进一步加入成核剂后分散相尺寸更小、粒径分布更均匀；PP球晶随PET的混入而减小；在PP／PET体系中加入EPDM-g—GMA起到反应增容和橡胶增韧的协同效应，使缺口冲击强度由未加增容剂时的2．0kJ／m^2提高至6．6k．1／m^2，弹性模量较PP提高了38％；PP／PET共混物的拉伸强度随PET含量的增加下降，在相同PET含量的情况下，加入EPDM—g-GMA后，共混物的拉伸强度与未增容体系基本一致。