PP/EPR共混体系的相容性

利用橡胶类聚合物二元乙丙(EPR)与聚丙烯(PP)熔融共混是PP常用的增韧改性手段。共混体系中PP连续相与EPR橡胶相分散成具有良好相界面作用的“海-岛”结构,EPR对PP的增韧机理主要是“银纹-剪切带屈服”理论。虽然EPR与PP都含有丙基,根据相似相容性原理,它们之间应具有较好的相容性。但是在实际的共混中,EPR在基体PP中的分散状态还要取决于共混的工艺条件。在相同的共混组成条件下,当PP与EPR具有相近的熔融粘度时,所制得共混物的形态结构较均匀。在PP／EPR共混体系中,加入增塑剂邻苯二甲酸二辛脂(DOP)后,部分DOP分散在PP／EPR两相界面上,可以降低两相界面的结合强度,而使共混物的强度降低;另外加入第三组份PE后的三元共混物,可以通过控制PP、EPR、PE的含量,使EPR起到PP和PE的相容剂的作用,使体系形成一种特殊的“棱-壳”结构。     

PP/LLDPE交联共混物的力学性能研究

采用两步交联加工法制备出具有优良力学性能的PP／LLDPE共混物。实验表明：当m(PP)／m(LLDPE)／m(SBS)／m(交联剂)为80／20／10／3时，交联共混物的冲击强度、拉伸强度和断裂伸长率分别达到466．3J／m、27．1MPa和715．1％，比未交联的共混物分别提高262％、8．28％和115％；交联作用的存在使共混物的脆韧转变点明显提前；随交联剂用量的增加，共混物的力学性能不断提高，但增大趋势逐渐变小。     

SBS/PE-LD共混物的强化辐射交联研究

研究了多官能团单体的用量、官能团数目以及辐射剂量对苯乙烯丁二烯共聚物（SBS）与低密度聚乙烯（PE-LD）共混物的强化辐射交联效应,测试了共混物的辐射交联程度、力学性能与形状记忆性能。结果表明,随辐射剂量的增加,SBS/PE-LD共混物的交联程度增加;多官能团单体的加入能够提高共混物的交联程度;相同辐射剂量时,官能团数目越多,交联程度越高;辐射剂量高于150 kGy时,多官能团单体的加入可以提高SBS/PE-LD共混物的拉伸强度;强化辐射交联SBS/PE LD共混物具有优异的形状记忆性能。     

SBS/PE-LD的强化交联与形状记忆效应研究

用苯乙烯丁二烯共聚物（SBS）与低密度聚乙烯（PE-LD）共混,采用过氧化二异丙苯（DCP）作为引发剂,3种不同的多官能团单体作为强化交联剂,使共混物发生强化交联形成网状结构,对多官能团单体的强化交联作用进行了分析,测试了交联共混物的拉伸强度与断裂伸长率,探讨了交联共混物的形状记忆效应。结果表明,多官能团单体的加入能够显著提高SBS/PE-LD交联共混物的交联程度,交联SBS/PE-LD共混物具有优异的形状记忆性能,形状固定率和形状回复率均可达100 %。     

CacO3在PP和PP/mPE共混物基体中的作用比较

研究CaCO3填料在取丙烯（PP）和茂金属聚乙烯（mPE)弹性体增韧PP共混物（PP／mPE)2种基体中的不同作用。结果表明：在PP基体中，填料显著提高其刚性，而在共混物基体中，由于弹性体的存在，填料的增强作用减弱；弹性体能够改善填料粒子和基体的界面粘合，增大弹性体分散相的尺寸，使PP/mPE共混物的拉伸断裂韧性提高。低温下（－30℃）的Charpy缺口冲击实验表明：少量的CaCO3即可导致PP/mPE体系冲击强度的迅速下降。     

极性化SBS对ABS/PP共混性能的影响

采用单螺杆挤出机对ABS和PP进行了共混挤出,研究了极性化SBS的加入对其共混性能的影响。试验结果表明,随着极性化SBS含量的增加,共混物的拉伸强度降低,断裂伸长率和抗冲强度增加。动态力学性能分析表明,随着极性化SBS含量的增加,共混物的储存模量和玻璃化转变温度降低。TEM分析表明,极性化SBS可以很好地改善ABS和PP的相容性,随着极性化SBS含量的增加,PP越来越均匀地分散在ABS相中,两相之间的界面也越来越模糊。     

相容剂改性PE/PP共混物在滴灌带中的应用

介绍了相容剂改性聚乙烯/聚丙(烯PE/PP)共混物在生产滴灌带中的应用,探讨了相容剂改性PE/PP共混体系的相容机理,通过大量的实验找到了最佳配比方案。结果表明:以相容剂改性PE/PP共混物生产的滴灌带与普通滴灌带对比界面黏结性强;改善和提高了PE/PP共混物的相容性和力学性能。     

PP／PE-LLD／SBS共混交联体系的结构与性能研究

采用两步交联法制备PP/PE-LLD/SBS交联共混物。DSC和WAXR测试结果表明,交联作用对共混物组分的结晶度无明显影响;从维卡软化点和TG、DTG曲线可以看出,交联提高了共混物的耐热温度,热稳定性增强;通过DMA测试发现,交联后共混物组分的玻璃化转变温度Tg无明显变化,交联作用对分子链段的运动影响不大;但交联共混物的内耗角tanδ、存储模量Ε′和损耗模量Ε″都有很大提高,刚、韧性增强。交联使共混物的熔体流动速率减小,流动性下降,但仍保持假塑性流体行为,随剪切速率增大出现剪切变稀;交联作用增大了共混物的活化能,分子链间作用力加强,刚性增大,黏度对温度变化更为敏感。     

PP-g-(GMA-co-St)增容PVC/PP共混物的研究

制备了一种新型的多单体接枝PP[PP-g-（GMA—co—St）]，研究了其对聚氯乙烯／聚丙烯（PVC／PP）共混体系的增容作用。讨论了接枝PP用量对共混物的界面相互作用、力学性能、耐热变形性能和加工流变性能的影响，并通过扫描电镜（SEM）对共混物的微观相结构进行了观察。结果表明，该接枝PP对PVC／PP共混体系有较好的增容效果，接枝PP的加入使共混物的界面相互作用增强。共混物的力学性能在接枝PP用量为20份时最佳；熔体流动速率在其质量分数为20％后下降缓慢，共混物的耐热变形性能随PP—g-（GMA—co—St）用量的增加而增强。     

相容剂改性PE/PP共混物在滴灌带中的应用

介绍了相容剂改性PE/PP共混物在生产滴灌带中的应用情况,探讨了相容剂改性PE/PP共混体系的相容性机理,通过大量的实验找到了最佳配比方案。结果表明:以相容剂改性PE/PP共混物生产的滴灌带与普通滴灌带配方对比界面黏结性强,不分层剥离。改善和提高了PE/PP的相容性和产品力学性能。     

Annealing of polypropylene/poly(ethylene-co-propylene) blend. II. Influence of the structure and properties of poly(ethylene-co-propylene) and blended polyethylene on impact strength

The effect of annealing on the impact strength of PP/poly(ethylene-co-propylene) (PEP) and PP/PEP/PE blends was studied with regard to the structure of PEP and the polyethylene crystallinity. The tensile impact strength of annealed blends was remarkably affected by the PEP structure such as molecular weight and comonomer composition and the annealing temperature, while the brittle temperature was scarcely affected. For the PP/PEP/PE blends, annealing at temperatures above the melting point of PE lowers the tensile impact strength in a similar manner as the PP/crystalline PEP blend. These phenomena were explained on the basis of the deformation mechanism presented in the previous article, that is, a thicker interfacial layer of PP and PEP forms by means of annealing to increase the energy needed to deform the interface. By using a scanning electron microscope, the transition layer was observed at the interface between amorphous PEP and PE in the PP/amorphous PEP/PE blend after etching with nitric acid. The formation of a thicker transition layer between amorphous PEP and PE and a sizeable increase in PE particle size by annealing was observed. The phenomena should be correlated with the impact sensitivity, especially tensile impact strength, in the PP/crystalline PEP and PP/amorphous PEP/PE blends. A reasonable explanation of the microstructure in PP/PEP blends has been developed in terms of comonomer composition and melting property of PEP.     

Mechanical properties and morphology of crosslinked PP/PE blends and PP/PE/propylene–ethylene copolymer blends

Blending is an effective method for improving polymer properties. However, the problem of phase separation often occurs due to incompatibility of homopolymers, which deteriorates the physical properties of polyblends. In this study, isotactic polypropylene was blended with low-density polyethylene. Crosslinking agent and copolymers of propylene and ethylene (either random copolymer or block copolymer) were added to improve the interfacial adhesion of PP/LDPE blends. The tensile strength, heat deflection temperature, and impact strength of these modified PP/PE blends were investigated. The microstructures of polyblends have been studied to interpret the mechanical behavior through dynamic viscoelasticity, wide-angle X-ray diffraction, differential scanning calorimetry, picnometry, and scanning electron microscopy. The properties of crosslinked PP/PE blends were determined by the content of crosslinking agent and processing method. For the material blended by roll, a 2% concentration of peroxide corresponded to a maximum tensile strength and minimum impact strength. However, the mechanical strength of those products blended by extrusion monotonously decreased with increasing peroxide content because of serious degradation. The interfacial adhesion of PP/PE blends could be enhanced by adding random or block copolymer of propylene and ethylene, and the impact strength as well as ductility were greatly improved. Experimental data showed that the impact strength of PP/LDPE/random copolymer ternary blend could reach as high as 33.3 kg · cm/cm; however, its rigidity and tensile strength were inferior to those of PP/LDPE/block copolymer blend.     

Influences of dicumyl peroxide on morphology and mechanical properties of polypropylene/poly(styrene‐b‐butadiene‐b‐styrene) blends via vane‐extruder

Polypropylene (PP) and poly(styrene‐b‐butadiene‐b‐styrene) block copolymer (SBS) were melt‐blended in the presence of initiator system. Dicumyl peroxide (DCP)/Triallyl isocyanurate (TAIC) via self‐deigned VE, aiming at in situ reactive compatibilization of toughed PP/SBS blend. The reactivity, morphology and mechanical properties of PP/SBS/DCP/TAIC blends were studied. Online torque detection was conducted to monitor changes in viscosities of reactive compatibilized blends, which could give proof of the interfacial grafted reaction induced by DCP/TAIC system. The effect of reactive compatibilization on the dispersed particles sizes and interfacial adhesion was studied by scanning electron microscopy. Analysis on mechanical performance revealed the impact strength improved after treated by initiator system, moreover, the impact‐fractured surface observation showed, the failure mode changed from debonding mechanism of neat 50PP/50SBS blend to plastic deformation mechanism of blend containing 3.0 phr initiator system. With improved interfacial adhesion, compatibilized blends not only were toughened but also exhibited enhanced tensile strength and thermal stability. Dynamic mechanical analysis showed a reduction of between PP phase and the PB segments in SBS phase, indicating reactive compatibilization of the blend was achieved. In the final part, a brief discussion was given about the dominant effects from chain scission of PP matrix to intergrafting reactions of PP and SBS, under different content of DCP/TAIC initiator system. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41543.     

The Use of Ethylene/Propylene Copolymers as Compatibilizers for Recycled Polyolefin Blends

Compatibilizing effects of ethylene/propylene (EPR) diblock copolymers on the morphology and mechanical properties of immiscible blends produced from recycled low‐density polyethylene (PE‐LD) and high‐density polyethylene (PE‐HD) with 20 wt.‐% of recycled poly(propylene) (PP) were investigated. Two different EPR block copolymers which differ in ethylene monomer unit content were applied to act as interfacial agents. The morphology of the studied blends was observed by scanning‐ (SEM) and transmission electron microscopy (TEM). It was found that both EPR copolymers were efficient in reducing the size of the dispersed phase and improving adhesion between PE and PP phases. Addition of 10 wt.‐% of EPR caused the formation of the interfacial layer surrounding dispersed PP particles with the occurrence of PE‐LD lamellae interpenetration into the layer. Tensile properties (elongation at yield, yield stress, elongation at break, Young's modulus) and notched impact strength were measured as a function of blend composition and chemical structure of EPR. It was found that the EPR with a higher content of ethylene monomer units was a more efficient compatibilizer, especially for the modification of PE‐LD/PP 80/20 blend. Notched impact strength and ductility were greatly improved due to the morphological changes and increased interfacial adhesion as a result of the EPR localization between the phases. No significant improvements of mechanical properties for recycled PE‐HD/PP 80/20 blend were observed by the addition of selected block copolymers.     

PVC/SBS/MBS三元共混体系的力学性能及光学透明性研究

采用冲击实验、拉伸实验、超景深三维显微镜、扫描电镜和分光光度计等手段，对PVC／SBS／MBS三元共混体系的冲击强度、拉伸强度、形态结构以及光学透明性等进行了研究。实验结果表明，MBS能有效改善PVC／SBS共混体系的界面相容性。当SBS和MBS的总量不变时，随着MBS相对含量的增加，共混体系的缺口冲击强度逐渐增加，透光率在m（MBS）／m（SBS）=28／80时达到最大值，光学透明性能最好。     

PE/PP共混物卷绕丝微观结构的研究

用透射和扫描电子显微镜研究PP/PE共混物在熔融纺丝时 ,PE掺入对PP结构的影响。研究结果表明 :PE与PP存在一定程度的相互作用 ,PP中加入PE能改变卷绕丝中PP结晶结构 ;PP中加入质量分数低于 10 %的PE时可以顺利纺丝 ,所得的卷绕丝断裂伸长率较大 ,具有良好的可拉伸性     

Compatibilization of polystyrene and low density polyethylene blends by a two-step crosslinking process

A new method has been developed to compatibilize the blends of polystyrene (PS) and polyethylene (PE). Polyethylene is first crosslinked partially by using a small amount of dicumyl peroxide (DCP) in a mixer at 165°C. Then the crosslinked PE is melt-blended with PS for another 5 min. Finally, a styrene–butadiene–styrene block copolymer (SBS) is added to the melt and mixed for another 5 min. We refer to this special procedure as the two-step crosslinking process. During the final mixing step of this process, the residual free radicals in the PE react with SBS. The crosslinking that occurs between PE and SBS has a significant impact on the mechanical properties of the blends including the impact strength, the tensile modulus, and the elongation-at-break. Scanning electron microscopy (SEM) results indicate that the interfacial adhesion is increased significantly, even though the domain sizes have not changed significantly in comparison with the non-crosslinked system. Transmission electron microscopy (TEM) results indicate that a thin SBS interfacial layer fully encapsulates the PE particles. This method could also be applied to other blend systems containing at least one component and a compatibilizer that are crosslinkable.     

Synergistic effect of SBS and trimethylopropane trimethacrylate (TMPTMA) on dynamically vulcanized SEBS/PP blends

The SEBS/PP thermoplastic vulcanizates (TPVs) were prepared by melt blending. Di‐tert‐butyl peroxide (DTBP) was used as the curing agent in combination with trimethylopropane trimethacrylate (TMPTMA) and poly(styrene‐b‐butadiene‐bstyrene) (SBS) as the coagents for the curing process. The synergistic effect of TMPTMA and SBS on the structure and properties of TPVs was studied by means of FT‐IR, DSC, torque rheometer, and universal testing machine. Both SEBS and PP crosslinked and the network structure formed under the participation of TMPTMA and SBS. Compared with the sole addition of the coagent, simultaneous loading of both TMPTMA and SBS could provide the TPVs with better solvent‐resistance and excellent mechanical properties. The crosslinking mechanism of the TPVs was also proposed. The slight lower value of T_m for the TPVs indicated the improved miscibility between PP and SEBS due to the crosslinking reaction. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44392.