Combined effect of β‐nucleating agent and processing melt temperature on the toughness of impact polypropylene copolymer

The phase morphology and toughening behavior of impact polypropylene copolymer (IPC) with and without nucleating agent (NA), prepared at different processing melt temperatures (T_p), were investigated. Interestingly, three different structures can be formed in the IPC samples by adding NA or tuning T_p. A well‐defined core–shell structure is obtained in samples with α‐NA or without NA prepared at all T_p. A developing multilayered structure is mainly formed at high T_p with added β‐NA, while an incomplete phase separation structure with interpenetrating chains is the dominant structure for IPC samples prepared at low T_p with added β‐NA. In this case, because of the synergistic effect between phase morphology and relatively high β‐form crystal content, the chain interaction among the components and chain mobility of the amorphous portion of IPC are distinctly improved, resulting in a largely improved toughness under 0 °C. This improvement in toughness is very important for applications. © 2012 Society of Chemical Industry     

The effect of microstructure on the toughness of polypropylene random copolymer

ABSTRACT

This article mainly explores the mechanism and deformation of polypropylene random copolymer at different temperatures and the role of microstructure in the toughening process. Firstly, the conventional differential scanning calorimetry, wide-angle X-ray diffraction, and scanning electron microscopy were employed to study different structures of crystalline and amorphous regions. Furthermore, the dynamic thermomechanical analysis was used to study the changes in the molecular mobility in samples. Secondly, the toughness and fracture morphology of the material was analyzed by notched Izod impact test and scanning electron microscopy. Thirdly, samples were stretched and combined 2D-WAXD to analyses the changes in its crystal regions. The thickness and distribution of the lamellae, as well as stress transmitters, work synergistically during polypropylene random copolymer deformation. The yield is due to the spherulite deformation and a small part of lamellae rotation and reorientation when the temperature is 25 C. When near the glass transition temperature, a large number of lamellae are crushed and oriented to form a large number of microfibers at the yield point.

The in-situ formed rubber phase in polypropylene random copolymer plays a significant role in the toughening process. When the temperature is 25 C the yield is due to the spherulite deformation and a small part of lamellae rotation and reorientation. While a large number of lamellae are crushed and oriented to form a large number of microfibers at the yield point when the temperature is 0 C.     

Phase morphology and impact toughness of impact polypropylene copolymer

Factors influencing the impact toughness of two impact polypropylene copolymers (IPC) with almost the same ethylene content, molecular weight and molecular weight distribution were studied by temperature gradient extraction fractionation (TGEF), scanning electron microscopy (SEM), nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC). The results indicate that poor interfacial adhesion between the disperse phase and the continuous matrix, larger dimensions and non-uniform distribution of disperse phases are main reasons for the low impact toughness of IPC B that possesses of a low content of ethylene-propylene segmented copolymer with long crystallizable PE and PP sequences as a compatibilizer between the disperse phase and the matrix.     

水辅注射成型聚丙烯制品的取向结晶

应用小角X射线散射研究了水辅注射成型(WAIM)等规聚丙烯制品中串晶(shish-kebab)结构的形成、分布以及片晶取向行为.结果表明:根据取向度不同,WAIM制品沿壁厚方向可明显分为表层、芯层和水道层.表层和水道层均有shish-kebab结构生成,且在表层生成的数量比水道层多,而芯层则没有这种结构.这种shish...     

低熔指透明聚丙烯注塑专用料T40B的开发

采用单环管工艺均聚法,通过对前期调研和多次试验筛选,选用合适的新型成核剂,并针对大庆石化聚丙烯装置的具体情况,研制开发出光泽度好、透明度高、低指数的高品质透明聚丙烯注塑专用料,各项指标符合要求,产品应用效果良好,达到了预期目的.     

抗冲共聚聚丙烯J842的开发

通过设计合理的生产控制方案,成功开发出高性能抗冲共聚聚丙烯J842产品,并分析了产品的力学性能.J842产品综合性能优良,抗冲击性能好,刚性稍有不足.建议通过改变催化剂体系、适当提高均聚聚丙烯粉料的熔体流动速率、优化改性剂添加配方等来改进J842产品的质量.     

Hierarchy structure in injection molded polypropylene/ethylene–octane copolymer blends

In this article, the phase morphology and mechanical properties of polypropylene (PP)/ethylene–octane copolymer (POE) blends with fixed ratio (60/40) obtained via different processing conditions, including barrel temperature, injection speed, and mold temperature, have been investigated. SEM was carried out for detailed characterization of phase morphology from the skin to the core, layer by layer. It was interesting that for all the processing conditions no dispersed POE elastomer was observed in the skin layer but elongated POE particles with large size were observed in the subskin layer. From the transition zone to the core layer, an increased phase separation was observed, which could lead to a formation of cocontinuous morphology, depending on the processing condition used. Higher barrel temperature, lower mold temperature, and higher injection speed could result in a smaller size of POE phase. The tensile strength and impact strength were found not sensitive to barrel temperature and mold temperature but to the low injection speed, both tensile strength and impact strength had a higher value for specimen obtained via low injection speed. The formation of the skin‐core morphology and the effect of processing conditions on the phase morphology were discussed based on crystallization kinetics of PP matrix, rheology, and shear induced phase mixing. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

无规共聚聚丙烯管材氧化诱导时间测试探究

以无规共聚聚丙烯（PP?R）管材为研究对象,采用差示扫描量热仪（DSC）测试了PP?R管材的氧化诱导时间（OIT）,并研究了测试部位、样品直径、样品厚度以及取样方式等测试条件对OIT测试结果的影响。结果表明,从垂直管壁方向取芯层直径为6 mm、厚度为650 μm的试样进行测试时,OIT测试结果相对可靠。     

成型工艺参数对MBS、PP注塑件收缩率的影响

运用Taguchi技术研究了成型工艺参数对甲基丙烯酸甲酯-丁二烯一苯乙烯共聚物(MBS)和聚丙烯(PP)注塑制品收缩率的影响,并获得优化的成型工艺参数以使制品的收缩率最小.以碱性蓄电池壳为例,利用L9(34)正交矩阵进行实验,研究对比了成型工艺参数对制品收缩率的影响程度.结果表明,所选成型工艺参数中冷却时间和注射时间对MBS制品的收缩率影响较大.熔体温度和冷却时间对PP制品的收缩率影响较大.     

Melting and crystallization behaviors of injection‐molded polypropylene

The melting and crystallization behaviors of the skin layer in an injection‐molded isotactic polypropylene (PP) have been studied, mainly in comparison with those of the core layer and subsidiarily in comparison with those of a compression‐molded PP and a nucleator (talc)–added PP. The skin layer contains about 5% crystals, which have a high melting point of up to 184°C. They thermally vanish by melting once. The subsequent melting history will scarcely affect the melting behaviors. On the other hand, crystallization behaviors are strongly affected by the melting history. The skin layer crystallizes in a wide temperature range at high temperature. This tendency weakens with increasing melting temperature, approaching a constant and that of the core layer above 230°C, which suggests that the memory effect of the residual structure of PP vanishes by melting above 230°C. In explaining these experimental results, it is assumed that the residual structure substance is a melt orientation of molecular chains that works as crystallization nuclei and that the vanishing of the residual structure is nothing but a relaxation of the melt orientation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1751–1762, 2000     

Alternating multilayer structure of polyethylene/polypropylene blends obtained through injection molding

The formation of multilayer structures in the high‐speed thin wall injection‐molded samples of high‐density polyethylene/isotactic polypropylene blends is reported. Based on the morphology development in injection runner and mold, a possible formation mechanism of multilayer structure was proposed in this study. Injection molding could be used as a simple and an effective method for the fabrication of multifunctional multilayer structure. This work is interesting and important for scientific research as well as several potential applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Assessing the effect of processing variables on the mechanical response of polysytrene molded using vibration‐assisted injection molding process

The present work is focused on the study of vibration‐assisted injection molding (VAIM) process, using polystyrene as a model polymeric system. This recently developed polymer processing operation is based on the concept of using motion of the injection screw to apply mechanical vibration to polymer melt during the injection and packing stages of injection molding process, to control the polymer behavior at a molecular level, which would result in improvements/alterations to the mechanical behavior of molded products. In this study, the afore‐mentioned concept was verified experimentally from monotonic tensile experiments and birefringence measurements of VAIM molded polystyrene in comparison with those of conventional injection molding process. The results of our study indicate that the actual degree of strength improvement depends on at least four parameters, namely, vibration frequency, vibration amplitude, vibration duration, and the delay time between the injection start and the vibration start. Furthermore, when these parameters were optimized, as much as a 28% strength improvement was observed, accompanied by an increase in toughness. Furthermore, birefringence measurements revealed that VAIM processing significantly altered the residual stress distribution throughout final products, but it did not, however, change the material density in the products. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Self‐interference flow of an isotactic polypropylene melt in a cavity during injection molding. II. Morphology and crystallinity

This article is principally concerned with the morphology and crystallinity of isotactic polypropylene (iPP) parts molded by injection molding, during which a self‐interference flow (SIF) occurs for the melt in the cavity. Scanning electron microscopy shows that a transverse flow takes place in SIF samples. Wide‐angle X‐ray diffraction and differential scanning calorimetry show that SIF moldings exhibit a γ phase, in addition to α and β phases, and high crystallinity. Meanwhile, the results for iPP moldings made by the conventional flow process, that is, conventional injection molding, are reported for comparison. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2791–2796, 2003     

Effect of melt flow on morphology and linear thermal expansion of injection‐molded ethylene–propylene–diene terpolymer/isotactic polypropylene blends

An ethylene–propylene–diene terpolymer/isotactic polypropylene blend with a structure of co‐continuous microlayers was fabricated by injection molding and was then investigated. The blend exhibited an extremely low coefficient of linear thermal expansion (CLTE) in the directions of the length and the width. As the thickness of the oriented portion increased, the CLTE was further reduced. The morphology of the co‐continuous microlayers and the thermal expansion behavior varied with the sampling positions on the injection‐molded sheets. To study the relationship between the morphology and the melt flow, the melt flow behavior during injection molding was simulated using Moldflow. Orientation of the microlayers was determined using shear flow. When the shear rate increased, the orientation state increased and the CLTE decreased. © 2015 Society of Chemical Industry     

Super‐toughed polymer blends derived from polypropylene random copolymer and ethylene/styrene interpolymer

In this article, blends of polypropylene random copolymer (PP‐R) with a novel impact modifier, namely ethylene/styrene interpolymer (ESI), were prepared to evaluate the effectiveness of ESI in toughening PP‐R and the influence of ESI content on the mechanical, thermal, and rheological properties of polymer blends. Results showed that super‐toughened PP‐R/ESI blends (ca. Izod impact strength ≥ 500 J/m) were readily achieved with only 5 wt % ESI. The blends exhibited significant improvement in both impact strength and elongation, while small loss in tensile strength and elastic modulus when increasing ESI content. ESI had a nucleating effect that caused PP matrix to crystallize at higher temperatures, whereas PP‐R/ESI blends presented lower melting temperatures (T_m) than PP‐R matrix and T_m decreased with the increment of ESI content. Rheology study indicated that both PP‐R matrix and PP‐R/ESI blends presented shear thinning behaviors during melt processing. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Characterization of high melt strength propylene/1-butene copolymer synthesized by in situ heat induction melt reaction

Propylene/1-butene copolymer powders were produced through bulk copolymerization of propylene with 1-butene in a 12 m³ polymerization reactor. High melt strength polypropylene (HMSPP) was synthesized by in situ heat induction melt reaction, in which pure propylene/1-butene copolymer powders without any additives were used as a basic resin and trimethylolpropane triacrylate (TMPTA) as a crosslinking agent. The structure and properties of the resultant HMSPP were characterized by means of various measurements. The content of TMPTA strongly influenced the melt strength and melt flow rate (MFR) of HMSPP. With increasing the content of TMPTA, the melt strength of HMSPP increased, and the MFR reduced. In addition, owing to the existence of crosslinking structure, thermal stability and tensile strength of HMSPP were improved compared with pristine propylene/1-butene copolymer. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

高相对分子质量PP-R高强高韧机理的研究

在工业化聚丙烯(PP)装置生产出高相对分子质量的乙丙无规共聚PP(HWPPR1),用差示扫描量热仪、X射线衍射仪和偏光显微镜研究了HWPPR1和常规相对分子质量PP-R的非等温结晶行为、晶体结构和形态,并测试了力学性能。结果表明,HWPPR1表现出很高的刚性和韧性,其常温缺口冲击强度和拉伸强度分别比常规相对分子质量抗冲共聚物高约21J/m和5MPa。     

Spatial distribution of molecular orientation in injection molded iPP: influence of processing conditions

In this paper, the influence of processing conditions on the spatial distribution of the molecular orientation was determined within the depth of the thickness of injection molded isotactic polypropylene (iPP) plates. Small 35 μm-thick slices were microtomed from the surface to the core of 1 and 3 mm-thick plates. The orientation functions along the three crystallographic axes were determined on the slices from IR dichroism measurements and WAXS pole figures. It was found that the orientation of the amorphous phase was low and the crystalline orientation had a maximum in the shearing layer, which was solidified during the filling stage. The plate thickness seemed to govern the global level of orientation, while the injection speed determined the thickness of the shearing layer without changing the maximum of orientation. Changing the mold temperature from 20 to 40 °C did not modify the molecular orientation. A specific bimodal crystalline orientation was found in the shearing layer. This crystalline structure continued in the post-filling layer, but the local symmetry axes tilted towards the core.     

Microstructure and tensile properties of injection molded thermoplastic polyurethane with different melt temperatures

The use of injection molding technology to prepare heterogeneous interlayer film of laminated glass holds strong applicable potential. This article aims to investigate the effects of melt temperature and melt flow on the microstructure evolution and tensile properties of thermoplastic polyurethane (TPU) specimens during the injection molding process. The tensile properties of the TPU specimens show dependency on the melt temperature and melt flow direction. The results of birefringence indicate that melt flow and lower melt temperature induce higher stretching deformation of the molecular chain network. Small-angle X-ray scattering analysis approves that besides the melt temperature and flow direction, the testing position on the cross section of the specimen has great influence on the microstructure of the TPU sheet. Further analysis and conclusions can be made using wide-angle X-ray scattering method. The above results demonstrate that both the tensile properties and microstructure of the injection molded TPU specimens tend to be isotropic with the increase of melt temperature. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48891.