乙烯-丙烯嵌段共聚物与高密度聚乙烯熔体相容性的探讨

利用MiniLab微型混合流变仪测定高聚物熔体平衡转矩-转速关系曲线,探讨乙烯-丙烯嵌段共聚物(E-b-P)和高密度聚乙烯(HDPE)的熔体相容性.结果表明:Eb-P/HDPE共混物熔体是完全互容的,HDPE对E-B-P中的PE链段有更大的亲和力,可形成不同的核壳结构,使共混物的平衡转矩偏离原有的加和性,表现出协同效应.     

HDPE/PP/EPDM共混物的性能研究

研究了PP对HDPE性能的影响,随着PP用量增加,HDPE的熔体流动速率提高,冲击强度下降,PP含量为25%时,拉伸强度提高10%.三元乙丙共聚物可作为相容荆,改善HDPE/PP间的相容性,EPDM含量为8份时,能同时提高共混物的拉伸强度和冲击强度,当HDPE/PP/EPDM的质量比为77/23/8时,HDPE/PP/EPDM共混体系的综合性能较好.     

相容共混物熔体的平衡转矩与组成关系的探讨

以熔体指数不同的高密度聚乙烯(HDPE)和均聚聚丙烯(PP)为试样,利用MiniLab微型混合流变仪,研究了在熔融状态下完全互容的HDPE/HDPE、PP/PP和HDPE/PP共混物熔体的平衡转矩随组成的变化规律。结果表明:相容共混体系的熔体平衡转矩-组成关系曲线一般表现为线性或者二次抛物曲线。当高分子链的化学结构单元不同时,其共混熔体的平衡转矩-组成关系多为二次抛物曲线。     

PP熔体接枝物改善HPVC/PP共混物的相容性

采用PP熔体接枝物改善HPVC/PP共混物的相容性。考察了共混比、不饱和极性单体、PP熔体挤出接枝物、增塑剂及EPDM用量对共混物力学性能的影响。     

POE/HDPE/PP三元复合材料的形貌和力学性能研究

用熔融共混法制备了高密度聚乙烯/聚丙烯(HDPE/PP)和乙烯-辛烯弹性体/高密度聚乙烯/聚丙烯(POE/HDPE/PP)复合材料。通过冲击、弯曲和拉伸测试研究了复合材料的力学性能,采用扫描电镜(SEM)观察了材料的形貌。结果表明,由于HDPE和PP的相容性有限,限制了HDPE对PP综合力学性能的提高;通过添加POE,能改善HDPE/PP共混物的相容性,使HDPE/PP复合材料在保持较高弯曲和拉伸性能的前提下,抗冲击性能获得明显提高。当HDPE/PP的含量比为12/88和POE含量为8wt%时,POE/HDPE/PP三元复合材料的综合力学性能较好。     

PP/HDPE共混物的黏弹性对泡孔结构的影响

将聚丙烯(PP)分别与两种高密度聚乙烯(HDPE)共混,并采用超临界二氧化碳(SC-CO2)作为发泡剂进行高压釜发泡,得到PP/HDPE发泡材料。同时考察了PP/HDPE熔体的黏弹性,并研究了其对PP/HDPE发泡材料泡孔结构的影响。结果表明:PP与黏弹性低于其本身的HDPE共混时,随着HDPE含量的增加,熔体的黏弹性逐渐减小,其中当HDPE含量为25%时,能够得到均匀细小的微孔结构;PP与黏弹性高于其本身的HDPE共混时,随着HDPE含量的增加,熔体的黏弹性逐渐增大,但所得PP/HDPE发泡材料的泡孔尺寸、孔隙率却不减反增,且泡孔结构完整。     

聚烯烃共混研究

研究了LLDPE/HDPE、LLDPE/LDPE、HDPE/PP及HDPE/PP/EVA各共混体系的配比对拉伸性能的影响,并利用示差扫描量热计、毛细管流变仪分别对其中某些共混物的相容性及加工性能作了进一步探讨。结果表明,LLDPE/HDPE两组分能以任何配比互混,且配比为30/70时拉伸性能超过了纯组分,加工行为优于LLDPE;LLDPE/LDPE是不相容或存在极限相容性的多相共混物,其拉伸性能没有表现出强烈的协同效应,且配比低于40/60时,拉伸性能低于预料的迭加值;HDPE/PP是相容性很差的共混体系,其拉伸性能低于纯组分,在HDPE/PP共混物中加入EVA(乙烯-醋酸乙烯共聚物)后,其拉伸性能没有得到可望的改善,却降低了低剪切速率时的加工行为。     

不相容共混高聚物熔体的平衡转矩-组成关系

选用苯乙烯-丙烯腈共聚物(SAN),高密度聚乙烯(HDPE),聚丙烯(PP)和线性低密度聚乙烯(LLDPE)为样品,利用MiniLab微型混合流变仪,研究了SAN/HDPE,SAN/PP和SAN/LLDPE共混高聚物熔体不相容体系的平衡转矩随组成变化的规律。结果表明:与相容共混体系不同,不相容共混体系的平衡转矩不随组成单调的递增或递减,而呈现水平钝角型或者U型曲线变化。当两纯组分的流动性差异较大时其为水平钝角型曲线,相近时则为U型曲线。     

PP/HDPE/滑石粉复合材料微孔发泡实验研究

为了改善聚丙烯(PP)的微孔发泡性能,将PP与高密度聚乙烯(HDPE)共混,提高其熔体强度;然后在PP/HDPE共混体系中加入少量滑石粉,研究滑石粉的用量对共混体系熔体强度及微孔发泡过程的影响。研究结果表明,滑石粉的加入使体系的熔体强度提高,发泡样品的泡孔结构变得更均匀。而且,随着滑石粉用量的增加,泡孔尺寸减小,泡孔密度增加。     

超支化聚（酰胺-酯）对聚丙烯／聚氯乙烯／苯乙烯-甲基丙烯酸甲酯共聚物接枝聚丙烯共混体系的增容作用

研究了超支化聚(酰胺-酯)(HBP))对聚丙烯/聚氯乙烯/苯乙烯-甲基丙烯酸甲酯共聚物接枝聚丙烯共混体系[PP/PVC/PP-g-(St-co-MMA)]的增容作用。讨论了HBP的用量对PP/PVC(80/20)共混物力学性能的影响；研究了剪切应力、剪切速率和温度对PP/PVC(80/20)共混物熔体黏度的影响。实验结果表明在PP/PVC/PP-g-(St-co-MMA)(80/20/6)共混物中加入1份HBP时，就可以很好改善共混体系的相容性，使共混物拉伸强度达到最大值，同时使熔体表观黏度达到较小值。该共混物熔体属于假塑性流体。扫描电子显微镜(SEM)研究结果证明了HBP增强了PP/PVC/PP-g-(St-co-MMA)的界面粘结作用，减小了共混体系的相分离程度。     

Investigating polypropylene–green coconut fiber composites in the molten and solid states through various techniques

A series of polypropylene (PP)–green coconut fiber (GCF) composites were prepared by melt mixing and their properties studied in the molten state using an advanced nonlinear harmonic testing technique, and in the solid state using standard mechanical testing and scanning electron microscopy (SEM). The effect of fiber loading as well as the role of maleated polypropylene as compatibilizing agent was investigated. PP–GCF composites are heterogeneous materials that, in the molten state, are found to exhibit essentially a nonlinear viscoelastic character, in contrast with the pure PP, which has a linear viscoelastic region up to 50–60% strain. Complex modulus increases with GCF content but in such a manner that the observed reinforcement is at best of hydrodynamic origin, without any specific chemical interaction occurring between the polymer matrix and the fibers. The addition of maleated polypropylene improves the wetting of fibers by the molten polymer but the effect is so small that specific chemical reactions could hardly be considered as occurring. Flexural modulus data confirm the reinforcing effects of the fiber and an improvement is noted when some maleated polypropylene is used, with an optimum level of around 1% (or the PP content). SEM microphotographs clearly show that maleated polypropylene imparts a better wetting of GC fibers by PP, but chemical interactions are unlikely to occur between the polymer and GCF. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1922–1936, 2006     

From polymer blends to in situ polymer/polymer composites: Morphology control and mechanical properties

In situ polymer/polymer short fiber composites were generated by a two‐step process. In the first step, a polyamide (PA) dispersed phase is blended with a polypropylene (PP) matrix in a twin‐screw extruder at a temperature at which both polymers are in molten state. The extrudate was then stretched at the die exit to generate long and thin fibers of PA in the PP matrix well oriented in the direction of flow. Adhesion between the phases was promoted by addition of PP grafted with maleic anhydride (PP‐g‐MA). During the second step, the chopped extrudates were molded by injection or compression molding at a temperature at which PA in the form of fibers is in the solid state and the PP matrix is molten. The control of the formation of such ultrafine fibers was obtained by quantitative analyses for the deformation of the minor PA‐phase during twin‐screw extrusion and stretching at the exit of the die that involve both shear and extensional flows. Morphology and mechanical properties of such polymer/polymer composites were compared to equivalent blends with dispersed spherical particles‐type morphology prepared in a batch mixer device.     

The comparison of the behaviors of polymer/clay nanocomposites based on high density polyethylene and polypropylene in exposure of electron‐irradiation

The effect of irradiation on thermal and mechanical properties of high density polyethylene (HDPE) and polypropylene (PP)/clay nanocomposites in the presence of polyethylene glycol (PEG) and polypropylene glycol (PPG) for enhancing the clay dispersion into the polymer matrices is considered. The morphology studies show that clay layers satisfactorily expand in the presence of compatibilizers. The irradiation improves the mechanical properties of HDPE nanocomposites at 500 kGy, but it decreases the tensile strength of PP nanocomposites. The addition of PEG markedly ameliorates the mechanical properties of HDPE nanocomposites at 500 kGy, while this improvement is not deduced for PP nanocomposites. The thermogravimetric analysis data show that the irradiation increases the thermal stability of HDPE nanocomposites at the clay content of 5 wt% with and without compatibilizer. The thermal stability of PP nanocomposites descends with the irradiation dose, and the presence of PPG into the PP matrix intensifies this reduction. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Processing of wood plastic composites: The influence of feeding method and polymer melt flow rate on particle degradation

Spruce wood particle (WP)/polypropylene (PP) compounds were prepared in an internal mixer using different rotor speeds. To analyze the effect of feeding method on particle degradation, WP and PP were either fed as dry‐blend or WP was fed into the PP melt. To prevent melt freezing, pre‐heated WP were used as comparison to cold WP. In addition, WPs were compounded with different grades of PP or high‐density polyethylene (HDPE) to analyze the effect of polymer matrix melt flow rate (MFR) on particle degradation. Mixing behavior of compounds containing 30% and 70% (w/w) WP depended on feeding method, represented by a changing relation of final torque values. Feeding as dry‐blend and using pre‐heated particles led to stronger WP degradation. Degradation decreased with increasing polymer MFR. For PP compounds, particle degradation was stronger when containing 70% WP, for HDPE the difference due to WP content was only marginal. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43231.     

Morphology and electrical conductivity of injection-molded polypropylene/carbon black composites with addition of high-density polyethylene

This work attempts to clarify the influence of carbon black (CB) addition on the microstructure of injection-molded high-density polyethylene (HDPE)/polypropylene (PP) blends and effect of shear-induced polymer deformation on the conductive network structure. We observed that HDPE molecules are strongly interacted with carbon surfaces and CB particles are selectively located in HDPE domains. Morphology of the injection-molded specimen consists of three parts, namely, CB-HDPE complex domain, free HDPE domain and PP domain. The volume and microstructure of the free HDPE domain are significantly influenced by HDPE and CB concentration, CB structure, and PP viscosity. We also confirmed that the CB particles are capable of self-assembly to form random conductive networks even under high shear rate within very short time. The morphological changes were finally correlated to the variation of electrical conductivity.     

Rheological properties of polypropylene/high-density polyethylene blend melts. I. Capillary flow properties

Three kinds of isotactic polypropylenes (PP) with different melt flow indexes (MFIs) were melt-blended with three kinds of high-density polyethylenes (HDPE) with different MFI using a screw extruder, and the morphologies and capillary flow properties such as flow curve, entrance effect, Barus effect, and melt fracture were studied. When HDPE contents were 70 wt % or above and PP particles formed the disperse phase, the size of the particles decreased with decreasing viscosity of PP. When HDPE contents were 30 wt % or below and HDPE particles formed the disperse phase, the size of the particles was minimum when the viscosities of PP and HDPE were similar. The die swell ratios of the blends were higher than those of the components. On the other hand, the entrance correction coefficients of the blends were intermediate between those of the components. There was no correlation between the die swell ratio and the entrance corretion coefficient. Therefore, it is not always appropriate to regard the entrance correction coefficient as a measure of melt elasticity in the case of inhomogeneous polymer systems such as PP/HDPE blend.     

Comparison between five experimental methods to evaluate interfacial tension between molten polymers

In this work, an experimental comparison between five different techniques to measure interfacial tension between molten polymers is presented. The five techniques include two equilibrium methods: the pendant drop (PD) and the sessile drop (SD); two dynamic methods: the breaking thread (BT) and imbedded fiber retraction (IF); and a rheological method based on linear viscoelastic measurements of the blend (RM). The polymer pairs studied were polystyrene/polypropylene (PS/PP); and PP/high density polyethylene (PP/HDPE). It was possible to determine the interfacial tension between PP/PS with all the methods tested and the results corroborated within 20%. However, the interfacial tension between PP and HDPE could be evaluated only using rheological methods because of a too‐small difference of index of refraction between both polymers. The experimental precision increased in the following order: RM < SD < BT < IF < PD. The rheological method had the advantage of being simpler and faster than dynamic and equilibrium methods. However, when using the rheological method, care should be taken because the results obtained may depend upon the concentration of the blend used for the measurements. It was observed that the pendant drop and breaking thread methods cannot be used for polymers with high viscosity (above 5 × 10⁵ Pa.s).     

Polyethylene–polyethylene blends modified with an additive of isotactic polypropylene

The blends of very high molecular weight high-density polyethylene (VHMW–HDPE) or ultrahigh molecular weight high-denisity polyethylene (UHMW–HDPE) and low-density polyethylene with normal molecular weight (LDPE) in equal or prevailing concentrations of the first component have excellent mechanical properties but very high viscosity in a molten state. The present investigations are a continuation of the fact, established by us for the first time, that the addition of a third polymer, isotactic polypropylene (I-PP), at optimal low concentrations increases the melt flowability of these systems without considerable deterioration of their very good mechanical properties in the solid semicrystalline state. The comparison between the thermomechanical behavior and the sorption in organic media of the systems leads to the supposition that an uninterrupted physical network from the VHMW–HDPE has been formed. © 1996 John Wiley & Sons, Inc.     

PP／HDPE复合材料ECAE加工后的结构与性能

研究了不同共混配比的PP/HDPE复合材料经等通道转角挤压(ECAE)加工后的结构与性能。结果表明,PP/HDPE复合材料经ECAE加工后产生取向,形成各向异性结构;当HDPE质量分数在10%时,ECAE加工可增加PP/HDPE复合材料两组分的界面粘结,导致其冲击强度显著提高;当HDPE质量分数为30%和50%时,ECAE加工可使复合材料两相间的接触面积增加,结合较紧密,但界面粘结仍然较弱,因此其冲击强度提高较小。     

Enhanced fracture energy during deformation through the construction of an alternating multilayered structure for polyolefin blends

The effects of polymer blend components on the phase morphology, crystallization behavior and mechanical performance of materials processed by high speed thin‐wall injection molding (HSTWIM) and compression molding (CM) processes were investigated. High density polyethylene (HDPE) and polypropylene (PP) containing different ratios of rubber phase (0%, 18% and 21%) were selected to construct different blends. HSTWIM is shown to trigger the formation of a multilayered structure for these blends with oriented polymer crystals and epitaxial growth of HDPE crystals on PP. Such a layered structure is thought to provide a good template for morphological control of various functional polymer composites. Moreover, the addition of rubber in the multilayered structure with the rubber phase partially distributed between layers is observed. These issues are thought to be responsible for the much enhanced fracture energy compared with specimens from CM. The structural details and formation mechanism of these layered structures consisting of different compositions were investigated. Such a study could provide some guidelines for the preparation of high performance bio‐mimic materials or various functional polymer composites with alternating multilayered structure. © 2018 Society of Chemical Industry