PS／LDPE共混体系相结构的TEM研究

ＰＳ／ＬＤＰＥ共混体系相结构的ＴＥＭ研究徐世爱，江明，沈静姝（复旦大学高分子科学系和聚合物分子工程实验室，上海，２００４３３）（中国科学院化学研究所高分子物理开放实验室）关键词相结构，透射电镜，共混体系聚苯乙烯（ＰＳ）和低密度聚乙烯（ＬＤＰＥ）共混体...     

LLDPE／LDPE共混体系的相容性与性能

ＬＬＤＰＥ／ＬＤＰＥ共混体系的相容性与性能杨毓华，花荣，白春霞，于旻李三喜，葛铁军（中国科学院长春应用化学研究所长春１３００２２）（沈阳化工学院高分子系沈阳）关键词ＤＳＣ，ＷＡＸＤ，力学性能，ＬＬＤＰＥ，ＬＤＰＥ，共混，相容性非晶－非晶－结晶共混体系...     

苯乙烯与D—120共聚物的性能研究

合成了侧基含有过氧键的苯乙烯－Ｄ－１２０共聚物（Ｐｏｌｙ（Ｓｒ－ｃｏ－Ｄ－１２０）ＰＳＤ）。用ＩＲ、ＧＰＣ进行了表征。用ＤＳＣ、ＧＰＣ、ＴＧＡ探讨了共聚物的热稳定性及分解机理，并对其就地增容ＰＳ／ＬＤＰＥ共混体系进行了初步研究。结果表明：共聚物中过氧键浓度越大，其起始分解温度越低，降解越严重，该共聚物可作为ＰＥ／ＰＳ共混体系的就地增容剂。     

引入离子基团改善聚苯乙烯和热致液晶聚合物的相容性 Ⅰ热性能和形态

ＤＳＣ和ＳＥＭ研究结果表明聚苯乙烯（ＰＳ）与一种热致液晶聚合物（ＬＣＰ）（ＰＨＢ／ＰＥＴ（６０／４０）共聚酯）完全不相容．共混体系具有与组分无关的Ｔｇ，并且表现出明显的两相结构．将ＰＳ进行化学改性（引入磺酸基团）制备成磺化聚苯乙烯（ＳＰＳ），随中和盐离子的变化有：酸式、Ｌｉ、Ｎａ、Ｚｎ和Ｍｎ盐五种形式．用ＤＳＣ和ＳＥＭ对ＬＣＰ与ＳＰＳ共混物的热性能和形态进行了分析和表征．共混体系有一个与组成相关，且明显低于纯ＳＰＳ的Ｔｇ．这表明了ＰＳ与ＬＣＰ的相容性因为磺酸基团的引入而得到了改善．同时用Ｆｏｘ方程计算了ＬＣＰ的Ｔｇ．当ＳＰＳ含量较低时（不大于５０％）在各个共混体系中，所估算的ＬＣＰ的Ｔｇ相互吻合．表明共混体系满足Ｆｏｘ方程的前提条件，即ＬＣＰ与ＳＰＳ形成相容体系．当ＳＰＳ含量较低时（２５％），ＬＣＰ／ＳＰＳ的共混物为较均一体系，断面光滑；而ＳＰＳ含量较高时，在脆断面可以观察到纳米级的颗粒．电子能谱分析证明了这些颗粒是ＳＰＳ负离子的聚集体．     

高密度聚乙烯／低密度聚乙烯／乙烯—醋酸乙烯共聚物共混体系的结晶行为

通过ＤＳＣ和ＷＡＸＤ研究了高密度聚乙烯／低密度聚乙烯／乙烯－醋酸乙烯共聚物（ＨＤＰＥ／ＬＤＰＥ／ＥＶＡ）三元共混体系的热行为和结晶性能，发现当ＨＤＰＥ含量小于４０％时，ＥＶＡ对ＬＤＰＥ起稀释剂作用，促进ＨＤＰＥ、ＬＤＰＥ的晶相分离，使ＨＤＰＥ、ＬＤＰＥ单独结晶，当ＨＤＰＥ含量高于４０％时，ＬＤＰＥ片晶入进ＨＤＰＥ晶相，形成与ＬＤＰＥ在片晶水平上的共晶。     

高密度聚乙烯与乙烯丙烯辛烯—1共聚物共混体系的相容性

用ＤＳＣ和ＷＡＸＤ方法研究了高密度聚乙烯／聚（乙烯丙烯辛烯－１）（ＨＤＰＥ／ＥＰＯ）共混体系的结晶性能。共混物的ＤＳＣ曲线皆呈单峰，表明共混体系形成了共晶。晶胞参数ａ及结晶度随共混物组成而变，进一步证明ＨＤＰＥ／ＥＰＯ共混体系的相容性。     

高密度聚乙烯与乙烯丙烯辛烯－1共聚物共混体系的相容性

用ＤＳＣ和ＷＡＸＤ方法研究了高密度聚乙烯／聚（乙烯丙烯辛烯－１）（ＨＤＰＥ／ＥＰＯ）共混体系的结晶性能。共混物的ＤＳＣ曲线皆呈单峰，表明共混体系形成了共晶。晶胞参数ａ及结晶度随共混物组成而变，进一步证明ＨＤＰＥ／ＥＰＯ共混体系的相容性．     

高密度聚乙烯／低密度聚乙烯／乙烯－醋酸乙烯共聚物共混体系的结晶行为

通过ＤＳＣ和ＷＡＸＤ研究了高密度聚乙烯／低密度聚乙烯／乙烯－醋酸乙烯共聚物（ＨＤＰＥ／ＬＤＰＥ／ＥＶＡ）三元共混体系的热行为和结晶性能。发现当ＨＤＰＥ含量小于４０％时，ＥＶＡ对ＬＤＰＥ起稀释剂作用，促进ＨＤＰＥ、ＬＤＰＥ的晶相分离，使ＨＤＰＥ、ＬＤＰＥ单独结晶．当ＨＤＰＥ含量高于４０％时，ＬＤＰＥ片晶进入ＨＤＰＥ晶相。形成与ＬＤＰＥ在片晶水平上的共晶。     

极低密度聚乙烯与其它聚乙烯的共混

从结构角度，用ＤＳＣ，ＷＡＸＤ，ＳＡＸＳ研究了聚乙烯（ＰＥ）家族中极低密度聚乙烯（ＶＬＤＰＥ）与其它ＰＥ的互容性．ＨＤＰＥ／ＶＬＤＰＥ是共晶互容的，以其大量无规部分“溶解”了ＨＤＰＥ的结晶缺陷部分，提高了ＨＤＰＥ的Ｔｃ，Ｔｍ，Ｘｃ，结晶峰半高宽变窄，晶胞参数随组成而有最低值．ＶＬＤＰＥ与ＬＬＤＰＥ结构极为相似，ＤＳＣ及ＷＡＸＤ证明其共混物是共晶相容体系．ＬＤＰＥ／ＶＬＤＰＥ的结晶度符合按组成的计算值，但晶胞参数ａ，ｂ以及晶粒尺寸增大，ＤＳＣ上有分别相应于两组份的两个Ｔｍ；ＶＬＤＰＥ的Ｔｃ，Ｔｍ峰高之和高于按组份的计算值，ＬＤＰＥ的Ｔｍ，Ｔｃ则低于计算值．认为是正如ＬＬＤＰＥ／ＬＤＰＥ，ＬＤＰＥ向充满整个体积的ＶＬＤＰＥ中不断填入，以ＶＬＤＰＥ为晶核而结晶，形成相分离的不相容体系．     

含二烯丙基双酚A醚相容剂对HDPE/PC共混体系的影响

用低密度聚乙烯接枝二烯丙基双酚Ａ醚（ＬＤＰＥ ｇ ＤＢＡＥ）作为高密度聚乙烯／聚碳酸酯（ＨＤＰＥ／ＰＣ）共混体系的增容剂,研究了其对ＨＤＰＥ／ＰＣ共混体系的影响．通过共混物形态观察、热力学性能测试和结晶性分析,发现ＬＤＰＥ ｇ ＤＢＡＥ对ＨＤＰＥ／ＰＣ共混体系有良好的增容效果．并发现了增容剂在共混物中的最佳用量为１０ｐｈｒ,提高增容剂的接枝率更有利于改善共混物的性能     

The compatibilization effect of ethylene/styrene interpolymer on polystyrene/polyethylene blends

In this study, ethylene/styrene interpolymer (ESI) was used as compatibilizer for the blends of polystyrene (PS) and low‐density polyethylene (LDPE). The mechanical properties including impact, tensile properties, and morphology of the blends were investigated by means of uniaxial tension, instrumented falling‐weight impact measurements, and scanning electron microscopy. Impact measurements indicated that the impact strength of the blends increases slowly with LDPE content up to 40 wt %; thereafter, it increases sharply with increasing LDPE content. The impact energy of the LDPE‐rich blends exceeded that of pure LDPE, implying that the LDPE polymer can be further toughened by the incorporation of brittle PS minor phase in the presence of ESI. Tensile tests showed that the yield strength of the PS/LDPE/ESI blends decreases considerably with increasing LDPE content. However, the elongation at break of the blends tended to increase significantly with increasing LDPE content. The compatibilization efficiency of ESI and polystyrene‐hydrogenated butadiene‐polystyrene triblock copolymers (SEBS) for PS/LDPE 50/50 was further compared. Mechanical properties show that ESI is more effective to achieve a combination of LDPE toughness and PS rigidity than SEBS. The correlation between the impact property and morphology of the ESI‐compatibilized PS/LDPE blends is discussed. The excellent tensile ductility of the LDPE‐rich blends resulted from shield yielding of the matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2136–2146, 2007     

Effects of poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] on the charge distributions of low‐density polyethylene/polystyrene blends

The effect of the triblock copolymer poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) on the formation of the space charge of immiscible low‐density polyethylene (LDPE)/polystyrene (PS) blends was investigated. Blends of 70/30 (wt %) LDPE/PS were prepared through melt blending in an internal mixer at a blend temperature of 220 °C. The amount of charge that accumulated in the 70% LDPE/30% PS blends decreased when the SEBS content increased up to 10 wt %. For compatibilized and uncompatibilized blends, no significant change in the degree of crystallinity of LDPE in the blends was observed, and so the effect of crystallization on the space charge distribution could be excluded. Morphological observations showed that the addition of SEBS resulted in a domain size reduction of the dispersed PS phase and better interfacial adhesion between the LDPE and PS phases. The location of SEBS at a domain interface enabled charges to migrate from one phase to the other via the domain interface and, therefore, resulted in a significant decrease in the amount of space charge for the LDPE/PS blends with SEBS. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2813–2820, 2004     

CRYSTALLIZATION AND MECHANICAL PROPERTIES OF BLENDS OF METALLOCENE SHORT CHAIN BRANCHED POLYETHYLENE WITH CONVENTIONAL POLYOLEFINS

Metallocene-catalyzed short chain branched polyethylene (SCBPE) was blended with LDPE, HDPE, PS, EPDM and iPP in the weight proportions of 80 and 20. The crystallization and mechanical properties of these blends were studied by PLM, DSC and DMA. It has been observed in PLM that SCBPE/LDPE, SCBPE/HDPE and SCBPE/EPDM can form band spherulites whose band width and size are both smaller than that of the pure SCBPE. Tiny crystallites are observed in the completely immiscible SCBPE/PS blend. The crystallites in SCBPE/iPP are very small and only irregular spherulites are seen. The crystallization kinetics and mechanical properties of SCBPE are greatly affected by the second polyolefin, but in a different way, depending on the phase behavior and the modulus of the second components. SCBPE may be phase miscible in the melt with HDPE, LDPE and EPDM and co-crystallize together with HDPE or LDPE during cooling. A big change of crystal morphology and crystallization kinetics is seen in SCBPE/iPP blend compared with pure SCBPE and the lowest tanδ is also seen for this system. DMA results show that the tensile modulus of the blends has nothing to do with phase behavior, but only depends on the modulus of the second component.     

Small-angle X-ray scattering studies on plastically deformed rubber-modified polystyrene

The deformation process of blends of polystyrene (PS) and rubbery block copolymers based on polystyrene and hydrogenated polybutadiene (SEBS, Shell Kraton G1651)was studied by Transmission Electron Microscopy (TEM) and Small-angle X-ray Scattering (SAXS) on deformed tensile samples, under loaded conditions. When the rubber concentration is increased the impact toughness as well as the elongation at break Increases while the SAXS studies show that the amount of crazing decreases. TEM studies suggest that the main deformation mechanism in these materials is cavitation-induced shearing. When a crazing agent is incorporated in the disperse phase of rubber-modified PS the amount of crazing increases more than four times, but the toughness decreases dramatically.     

Effects of reprocessing on polymers—Part III: Photo-oxidation of polyethylene-polypropylene blends

It is shown that blends of low density polyethylene (LDPE) and polypropylene (PP) photo-oxidise more readily than LDPE alone and there was evidence of cross-linking between the two phases. An ethylene-propylene rubber (EPDM) which improved the mechanical performance of LDPE/PP blends caused an increase in the rate of photo-degradation as measured by carbonyl formation and by loss of toughness.     

A METHOD TO QUANTIFY CRAZING DEFORMATION BY TENSILE TESTS FOR POLYSTYRENE/POLYOLEFIN ELASTOMER IMMISCIBLE BLENDS

A method to quantify crazing deformations by tensile tests for polystyrene （PS） and polyolefin elastomer （POE） blends was investigated. The toughness of PS/POE blends, reflected by the Charpy impact strength, increased with the content of POE. SEM micrographs showed the poor compatibility between PS and POE. In simple tensile tests, it is very easy to achieve the ratio of crazing deformation, i.e. K by measuring the size changes of samples. The K values decreased with increasing the content of POE, and the deformations of PS/POE blends were dominated by crazing. The plots of the change of volume （△V） against longitudinal variation （△I） showed a linear relationship, and the slope of lines decreased with the content of POE. Measuring samples at the tensile velocities of 5 mm/min, 50 mm/min, and 500 mm/min respectively, the K values kept unchanged for each PS/POE blends.     

Studies on fracture behaviors of immiscible polypropylene/ethylene‐co‐vinyl acetate blends with multiwalled carbon nanotubes

Immiscible polypropylene/ethylene‐co‐vinyl acetate (PP/EVA) blends with two different compositions, one (PP/EVA = 80/20) exhibits the typical sea‐island morphology and the other (PP/EVA = 60/40) exhibits the cocontinuous morphology, were prepared with different contents of f‐MWCNTs. The fracture behaviors, including notched Izod impact fracture and single‐edge notched tensile (SENT) fracture, were comparatively studied to establish the role of f‐MWCNTs in influencing the fracture toughness of PP/EVA blends. Our results showed that, for PP/EVA (80/20) system, f‐MWCNTs do not induce the fracture behavior change apparently. However, for PP/EVA (60/40) system, the fracture toughness of the blend increases dramatically with the increasing of f‐MWCNTs content. More severe plastic deformation accompanied by the fibrillar structure formation was observed during the SENT test. Furthermore, SENT test shows that the significant improvement in fracture toughness of PP/EVA (60/40) with f‐MWCNTs is contributed to the simultaneous enhancement of crack initiation energy and crack propagation energy, but largely dominated by crack propagation stage. Further results based on crystalline structures and morphologies of the blends showed that a so‐called dual‐network structure of EVA and f‐MWCNTs forms in cocontinuous PP/EVA blends, which is thought to be the main reason for the largely improved fracture toughness of the sample. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1331–1344, 2009     

SYNERGISTIC MODIFICATION OF EPDM AND CROSSLINKING AGENT IN IMMISCIBLE BLENDS OF POLYVINYL CHLORIDE WITH LOW DENSITY POLYETHYLENE

The synergism of ethylene-propylene-diene monomer copolymer （EPDM） and dicumyl peroxide （DCP, a crosslinking agent） in low density polyethylene （LDPE）/poly（vinyl chloride） （PVC） blends was investigated. When EDPM and DCP are added to the blends simultaneously, the tensile properties could be improved significantly, especially for the blends with LDPE matrix. For example, incorporation of 10/1 （mass ratio） EPDM/DCP improves the tensile strength of the LDPE/PVC （mass ratio 80/20） blend from 7.9 MPa to 8.5 MPa and the elongation at break from 25% to 503%. Results from selective extraction, phase-contrast microscopy and thermal analysis reveal that the improvement in the tensile properties of the blends with LDPE matrix is principally due to the formation of a fine crosslinking network of the LDPE and EPDM phase. The outstanding modification effect of EPDM is explained by its dual functions： molecular entanglement with LDPE and the enhanced efficiency of DCP in the blends.     

TIME-DEPENDENT MORPHOLOGY OF POLYETHYLENE-POLYPROPYLENE BLENDS

The effect of time-temperature treatment on morphology of polyethylene-polypropylene (PE-PP) blends wasstudied to establish a relationship between thermal history, morphology and mechanical properties. Polypropylene (PP)homopolymers were used to blend with various polyethylenes (PE), including high density polyethylene (HDPE), lowdensity polyethylene (LDPE), linear low density polyethylene (LLDPE), and very and ultra low density polyethylene(VLDPE and ULDPE). The majority of the blends were prepared at a ratio of PE:PP = 80:20, while blends of PP and LLDPEwere prepared at various compositions. Thermal treatment was carried out at temperatures between the crystallizationtemperatures of PP and PEs to allow PP to crystallize first from the blends. On cooling further, PE crystallized too. A verydiffuse PP spherulite morphology in the PE matrix was formed in some partially miscible blends when PP was less than 20%by mass. Droplet-matrix structures were developed in other blends with either PP or PE as dispersed domains in a continuousmatrix, depending on the composition ratio. The scanning electron microscopy (SEM) images displayed a fibrillar structureof PP spherulite in the LLDPE-PP (80:20) and large droplets of PP in the HDPE-PP (80:20) blend, providing larger surfacearea and better bonding in the LLDPE-PP (80:20) blends. This explains why the blends with diffuse spherulite morphologyshowed greater improvement in tensile properties than droplet-matrix morphology blends after time-temperature treatment.     

聚苯乙烯/聚乙烯的反应性挤出共混

多官能团单体;聚苯乙烯/聚乙烯的反应性挤出共混