Effect of Microstructure of EPR on Crystallization and Morphology of PP/EPR Blends

Two ethylene-propylene random copolymer (EPR) fractions (sol-EPR: soluble part and insol-EPR: insoluble part in n-octane) were blended with polypropylene (PP). It was found hat sol-EPR has a random sequence distribution and is nearly amorphous, whereas insol-EPR contains long ethylene and propylene sequences and is partially crystalline. The crystallization and melting behaviors, linear spherulitic growth rate, crystal structure, and morphology were investigated with differential scanning calorimetry, polarized optical microscopy, wide angle X-ray diffraction, and scanning electron microscopy. It was observed that the PP/insol-EPR blends have a smaller domain size of EPR and a rougher fracture surface. The better compatibility between insol-EPR and PP leads to lower melting temperature (T _m) of PP/insol-EPR blends than the neat PP. For the blends cooled in air from the melt, both α and β crystals were observed. At low weight fraction (0–10%), EPR enhances the relative content of β crystals. When the weight fraction of EPR exceeds 10%, sol-EPR and insol-EPR decrease the relative content of β crystals in the blends to different extents. This difference can be correlated to the fact that sol-EPR and insol-EPR reduce the linear spherulitic growth rate (G) of PP to different extents.     

Study on Crystallization Behavior of Solid-Phase Graft Copolymers of Polypropylene with Maleic Anhydride and Methyl Methacrylate

The isothermal crystallization behavior of neat polypropylene (PP) and solid-phase graft copolymers of PP with maleic anhydride and methyl methacrylate (PPMM) were compared by differential scanning calorimetry. The Avrami equation and Hoffman theory were applied to describe the isothermal crystallization kinetics. The results show that the fitted isothermal crystallization parameters are similar to the experimental data, and suggest that the Avrami equation is suitable to describe the isothermal crystallization process of PP and PPMM. The grafted side chains on PP can change the nucleation and growth of crystallization. They caused a decrease in the apparent crystallization activation energy and lateral surface free energy, and an increase in the nucleation rate. This was attributed to the grafted side chains not only acting as nucleating agent but also hindering the motion of the molecular chains and reducing the growing rate of crystallization.     

聚丙烯/聚乙烯共混物环状型坯挤出膨胀和垂伸的研究

利用双螺杆挤出机将聚丙烯分别与不同熔体流动速率的聚乙烯进行共混,通过环状型坯挤出,研究了共混物的型坯膨胀和垂伸情况。结果表明,聚丙烯与较高熔体流动速率的聚乙烯共混后,其型坯直径膨胀的变化范围较宽,垂伸较明显。     

流动场下等规聚丙烯/无规聚丙烯共混材料结构与性能研究

通过动态保压注塑技术制备了不同无规聚丙烯(aPP)含量的等规聚丙烯(iPP)/无规聚丙烯共混试样,测试了这些试样的力学性能,并采用二维广角X射线衍射(2D-WAXD),二维小角X射线散射(2D-SAXS)和扫描电镜(SEM)研究了共混物中iPP分子链取向、晶体取向和晶体形态。结果表明,动态保压注塑条件下,aPP质量分数为20%的试样具有最均衡的强度与延展性,并能最大程度地利用通常被当作工业废弃物的aPP,拉伸强度为44.5MPa,断裂能为27.6 MJ/m3,这是由于aPP作为弹性体改善了iPP的延展性和韧性,同时流动场下形成了大量高度取向的串晶结构,提高了试样的强度。     

二氧化硅对等规聚丙烯和共聚聚丙烯结晶和熔融行为的影响

通过差示扫描量热仪(DSC)和X射线衍射分别研究了二氧化硅(SiO2)粒子填充等规聚丙烯(iPP)和共聚聚丙烯(co-PP)复合材料的结晶行为和晶体结构。DSC分析结果表明:由于异相成核作用,SiO2粒子提高了iPP的结晶温度,缩短了半结晶期;由于SiO2粒子的表面积大,表面能高,能够将co-PP分子链上的低等规度的链段吸附到填料表面,因而co-PP分子链的运动能力降低,结晶能力下降,导致co-PP的结晶温度大大下降,半结晶期延长。X-射线衍射分析结果表明:SiO2的加入抑制了iPP中β晶的结晶,而对co-PP中各α晶的相对含量影响不大。     

Crystallization assisted self-assembly of semicrystalline block copolymers

The self-assembly of block copolymers (BCPs) in the presence of crystallization as the second driving force is reviewed, for BCPs in the bulk, thin films, single crystals and micelles. The crystallization of semicrystalline BCPs in the bulk is introduced briefly and the unique morphologies of semicrystalline BCPs at various levels due to crystallization are discussed. The thin film morphologies shown by crystalline BCPs are summarized in terms of the factors affecting the relative strengths of various driving forces. Special attention is paid to the thin film morphologies of functional BCPs containing crystalline poly(3-alkylthiophene) and perylene bisimide units. The single crystal morphologies of semicrystalline BCPs are also presented. Finally, the micellar morphologies of BCPs with a semicrystalline core are reviewed. The controlled and living growth of crystalline micelles, which is the unique characteristic of such micelle, is then discussed.     

Effect of Nanoparticle Surface Treatment on Nonisothermal Crystallization Behavior of Polypropylene/Calcium Carbonate Nanocomposites

Polypropylene (PP)/CaCO₃ nanocomposites were prepared by melt-blending method using a Haake-90 mixer. The CaCO₃ nanoparticles were surface modified with a coupling agent before compounding. A fine dispersion of the modified nanoparticles in the nanocomposites was observed by transmission electron microscopy (TEM). Effects of surface treatment of CaCO₃ nanoparticles on the nonisothermal crystallization behavior and kinetics of PP/CaCO₃ nanocomposites were investigated by differential scanning calorimetry (DSC). Jeziorny and Mo methods were used to describe the nonisothermal crystallization process. It was shown that the crystallization temperature of the nanocomposites increased due to the heterogeneous nucleation of the surface-treated nanoparticles. It was found that the nanoparticles modified with a proper content range of coupling agent could facilitate the nonisothermal crystallization of the nanocomposites under certain conditions (the cooling rate and the relative degree of crystallinity). This may be a potential application for the crystallization controlling of composites in manufacturing. In addition, the activation energy of crystallization for the nanocomposites and the nucleation activity of the nanoparticle were estimated by using Kissinger and Dobreva's methods, respectively. It could be concluded that the surface-treated nanoparticles had a strong nucleating activity, which caused the decrease of the activation energy of the nanocomposites.     

Spherulitic Morphology of Isotactic Polypropylene and its Melting Behavior

Abstract

The crystallization and lamellar morphology of isotactic polypropylene (ipp) have been investigated by thermal analysis and electron microscopy. When ipp samples are crystallized above 132°C, no β-phase was detected and the samples consisted of pure α-spherulites and those showing double melting endotherms, the occurrence of double-peak shapes was attributed to the melting and reorganizing of the radial dominant lamellae, while melting of tangential cross-hatched lamellae belongs to the broad tail endotherm which leads the lower melting endotherm peak.     

Crystallization behavior of oxyethylene/oxybutylene diblock and triblock copolymers

The crystallization behavior of poly(oxyethylene)-b-poly(oxybutylene) block copolymers with different compositions, morphologies and architectures (E_mB_n diblock copolymers and E_mB_nE_m, B_nE_mB_n triblock copolymers) were investigated and the effect of volume fraction and architecture on the crystallization temperature (T_c) in non-isothermal crystallization was determined. It is found that the E_mB_n diblock copolymers having long E blocks exhibit similar crystallization temperatures, irrespective of volume fraction and morphology, but for the block copolymers with shorter E blocks the crystallization temperature increases with both the volume fraction, φ_E, and the length, m, of the E block. Some block copolymers with extremely low T_c, which fall into the temperature range normally associated with homogenous nucleation, were chosen for time-resolved small-angle X-ray scattering (SAXS) and isothermal crystallization kinetics experiments. The results show that breakout crystallization occurs in all these block copolymers. Therefore, unlike E_mB_n/B_h blends, there is no obvious relationship between T_c and crystallization behavior in neat block copolymers and homogeneous nucleation does not definitely lead to confined crystallization. The values of χ_c/χ_ODT for all the block copolymers with hex and bcc morphology were also calculated. It is found that all the block copolymers have χ_c/χ_ODT<3, in agreement with the previously reported critical value and consistent with their breakout crystallization behavior.     

Thermal Stability and Crystallization Behavior of TER Blends of Isotactic Polypropylene (iPP)/Ethylene-Propylene Diene Rubber (EPDM)/Nitrile Rubber (NBR)

The blends of isotatic polypropylene (iPP), ethylene-propylene diene rubber (EPDM), and nitrite rubber (NBR) were prepared using dimethylol phenolic resin as a crosslinking system. The dynamically crosslinked blends of iPP/EPDM/NBR showed superior thermal stability to that of virgin isotactic polypropylene (iPP). Dynamic crosslinking rendered the vulcanizate thermally more stable as compared to uncrosslinked blends, which can be attributed due to the variations in degree of crosslinking and degree of crystallinity.

Crystallization of iPP in the blends of iPP/EPDM/NBR was also studied through Temperature Modulated Differential Scanning Calorimetry (TMDSC). Other detailed analysis of endotherm peaks obtained after first and second melts in terms of heat of enthalpy, degree of undercooling, and degree of crystallinity were also evaluated. Various kinetic parameters were also determined. Degree of crosslinking increases the interfacial adhesion between the iPP and EPDM/NBR phases. Dimethylol phenolic resin used as a compatibilizer also enhanced the thermal stability of the iPP/EPDM/NBR blends.     

PEEK/PEI共混物的相容性和结晶行为研究

在380℃下熔融挤出制得聚醚醚酮（PEEK）与聚醚酰亚胺（PEI）共混物。采用差示扫描量热仪（DSC）和广角X射线衍射仪（WAXD）研究了共混物的相容性和结晶行为。结果表明,PEEK／PEI共混物完全相容．所有共混物均呈现一个玻璃化转变温度（Tg）,且与组分的关系符合Porch方程;随PEI含量的增加,共混体系的熔点、结晶度、整体结晶速率和结晶能力均降低：而PEEK的结晶度呈现先增加后减小的趋势,当PEI质量分数为50％时,达到最大。     

赤泥/聚丙烯复合材料非等温结晶动力学研究

采用DSC研究了聚丙烯(PP)及聚丙烯/赤泥复合材料的非等温结晶动力学,对所得的数据采用了Avrami方程的Jeziorny法及Mo法进行处理.结果表明:赤泥的加入提高了PP的结晶温度和结晶速率,PP的结晶活化能降低,赤泥成核活性高于改性的赤泥.在同样含量下,经钛酸酯偶联剂改性的赤泥使PP结晶温度增加,结晶活化能与赤泥/聚丙烯复合材料相比有小幅的增加.赤泥具有异相成核作用,经表面修饰的赤泥异相成核效果降低.     

Rheological Studies of Dynamic Vulcanization of Butyl Rubber and Polypropylene Blends

Butyl rubber (BR) is blended with polypropylene (PP) in ratios of 92: 8, 84: 16, 68: 32, 50: 50, 32: 68, 16: 84, and 8 : 92 (w/w) for the study of dynamic vulcanization. It is observed that the cure torque increases with the decrease in BR content up to the ratio of 50: 50. No cure torque is observed in the ratios of 16: 84 and 8: 92 of BR: PP blends as the PP content becomes very high. On comparison of cure rate of the blends, the BR (100%) shows the highest cure rate because of the fast saturation of double bonds present in BR, whereas maximum cure torque, work energy, and totalized torque are observed in the 32: 68 BR: PP blend. It is the result of the formation of an interpenetrating network.     

湿热老化对LDPE/POE结晶行为和力学性能的影响

在温度(40±2)℃,相对湿度93%条件下,研究了湿热老化对低密度聚乙烯(LDPE)与乙烯-辛烯共聚物(POE)共混物结晶行为和力学性能的影响。结果表明,随着湿热老化时间的延长,纯LDPE的拉伸强度以及POE用量分别为30%和70%共混物的断裂伸长率稍有增加。湿热老化对共混物的结晶行为产生了显著影响,且结晶行为的变化主要在老化前期完成。在老化中,POE的熔融峰和LDPE的低温熔融峰向高温方向漂移,并提高了共混物中LDPE在高温位置结晶的完善性和均一性。纯LDPE在老化过程中,小尺寸的晶体逐渐长大,结晶度逐渐增大,提高了LDPE结晶的完善性,且主要对LDPE(110)晶面产生明显的影响。     

β成核剂对等规聚丙烯结晶性能的影响

研究硬脂酸盐作为β成核荆对聚丙烯结晶性能的影响.WAXD结果表明:硬脂酸盐能诱导聚丙烯生成β晶型,在添加量为0.3%时,β晶的相对含量达到最大为76.64%.DSC曲线表明:硬脂酸盐改性的聚丙烯在152℃出现β晶型的熔融吸热峰,其结晶起始温度和结晶峰温度均向高温移动,表明添加硬脂酸盐可诱导PP中α晶向β晶转变,具有明显的β成核作用.     

Crystallization and coalescence of block copolymer micelles in semicrystalline block copolymer/amorphous homopolymer blends

Crystallization of two oxyethylene/oxybutylene block copolymers (E₇₆B₃₈ and E₁₅₅B₇₆) from micelles in block copolymer/amorphous homopolymer blends was studied by differential scanning calorimetry (DSC) and time-resolved small angle X-ray scattering (SAXS). Unlike the simultaneous crystallization and formation of superstructure in crystallization from an ordered structure, crystallization of block copolymer from micelles can be divided into two steps. The core of the micelles firstly crystallizes individually, with first-order crystallization kinetics and homogeneous nucleation mechanism. The SAXS revealed that crystallization-induced deformation occurs for the micelles, which strongly depends on microstructure of the block copolymers. For the shorter block copolymer E₇₆B₃₈, larger deformation induced by crystallization was observed, leading to coalescence of the micelles after crystallization, while for the longer block copolymer E₁₅₅B₇₆ the micelles show little deformation and the morphology of micelle is retained after crystallization.     

超微氧化钇填充聚丙烯的结晶行为

本文用偏光显微镜和ＤＳＣ表征了少量氧化钇超微粉填充聚丙烯的结晶行为，ＰＬＭ结果表明，加入Ｙ２Ｏ２超微粉能够改变聚丙烯晶型，促进生成部分β晶，等温结晶及熔融行为结果表明，Ｙ２Ｏ２可大大提高ＰＰ的结晶速率，匀速降温结晶结果表明Ｙ２Ｏ３提高了ＰＰ的起始和终了结晶温度，这都说明，氧化钇超微粉对ＰＰ的ａ晶和β晶均有明显的成核作用。     

Transport Kinetics and Diffusion of Monocyclic Aromatic Liquids in Polymeric Blends of Ethylene-Propylene Random Copolymer and Isotactic Polypropylene

Experimental results of molecular transport and diffusion parameters, determined by a gravimetric method, are presented for a thermoplastic Santoprene rubber in the presence of monocyclic aromatics between 25° and 70°C. The analysis of sorption, diffusion, and activation parameters led to the conclusion that transport depends on solvent size and the chemical nature of the molecules. Overshoot effect is attributed to the complex morphology of the Santoprene. However, other factors which might induce overshooting are the polymer segment relaxation and the leaching of the indigenous additives. Transport kinetics is studied using the first-order equation. Flory-Rehner theory is used to estimate the molar mass between physical chain entanglements.     

Foaming of Homogeneous Polypropylene and Ethylene-Polypropylene Block Copolymer Using Supercritical Carbon Dioxide

A new process was used to foam homogeneous polypropylene (HPP) and ethylene-polypropylene block copolymer (CPP). Many different foaming behaviors of these two kinds of PP were observed. The HPP and CPP were characterized by Differential Scanning Calorimetry (DSC), and Capillary Rheometry. We find that the melt shear viscosity of CPP is more sensitive to the temperature variation than that of HPP, thus leading to larger change of cell diameter of CPP with foaming temperature. Cell size of CPP is the result of competition between cell nucleation and cell growth. When the saturation pressure is lower or higher than 25 MPa, cell nucleation or cell growth plays a dominant role, which leads to the increase or decrease of cell size, respectively. Because of its low melting temperature and crystallinity, cell diameter of CPP increases with the infiltration temperature increasing, which is opposite to those of HPP. And at the foaming temperature of 152°C or 158°C, cell diameter of CPP increases or decreases with an increase in foaming time, while that of HPP decreases with foaming time increasing at both foaming temperatures.