CROSSLINKING AND COMPATIBILIZATION IN BLENDS OF POLYSTYRENE AND POLYETHYLENE

This paper investigated the influences of butadiene rubber (BR) and dicumylperoxide (DCP) on thermal and rheological behaviour, morphology and mechanical proper-ties of PS/LLDPE/SBS blend. Addition of DCP alone was found to decrease the mechanicalproperties of PS/LLDPE/SBS blend due to the decomposition of PS. When BR was addedtogether with DCP, it is found that the co-crosslinking of BR, SBS and PE takes place,and the decomposition of PS is reduced simultaneously because of the consumption of thefree radicals in the crosslinking process. Synergism was thus realised which resulted in theimprovement of the ductility of blend.     

BR和DCP在PS／LLDPE／SBS体系中的协同作用

ＢＲ和ＤＣＰ在ＰＳ／ＬＬＤＰＥ／ＳＢＳ体系中的协同作用方征平，许承威，项义崇（杭州大学化学系，杭州，３１００２８）关键词聚苯乙烯，聚乙烯，共混物，相分散－交联协同作用相分散（增容）－交联协同作用是提高不相容聚合物共混物性能的有效方法，我们曾将此方法成...     

Morphology,structure, and properties of in situ compatibilized linear low‐density polyethylene/polystyrene and linear low‐density polyethylene/high‐impact polystyrene blends

Blends of linear low‐density polyethylene (LLDPE) with polystyrene (PS) and blends of LLDPE with high‐impact polystyrene (HIPS) were prepared through a reactive extrusion method. For increased compatibility of the two blending components, a Lewis acid catalyst, aluminum chloride (AlCl₃), was adopted to initiate the Friedel–Crafts alkylation reaction between the blending components. Spectra data from Raman spectra of the LLDPE/PS/AlCl₃ blends extracted with tetrahydrofuran verified that LLDPE segments were grafted to the para position of the benzene rings of PS, and this confirmed the graft structure of the Friedel–Crafts reaction between the polyolefin and PS. Because the in situ generated LLDPE‐g‐PS and LLDPE‐g‐HIPS copolymers acted as compatibilizers in the relative blending systems, the mechanical properties of the LLDPE/PS and LLDPE/HIPS blending systems were greatly improved. For example, after compatibilization, the Izod impact strength of an LLDPE/PS blend (80/20 w/w) was increased from 88.5 to 401.6 J/m, and its elongation at break increased from 370 to 790%. For an LLDPE/HIPS (60/40 w/w) blend, its Charpy impact strength was increased from 284.2 to 495.8 kJ/m². Scanning electron microscopy micrographs showed that the size of the domains decreased from 4–5 to less than 1 μm, depending on the content of added AlCl₃. The crystallization behavior of the LLDPE/PS blend was investigated with differential scanning calorimetry. Fractionated crystallization phenomena were noticed because of the reduction in the size of the LLDPE droplets. The melt‐flow rate of the blending system depended on the competition of the grafting reaction of LLDPE with PS and the degradation of the blending components. The degradation of PS only happened during the alkylation reaction between LLDPE and PS. Gel permeation chromatography showed that the alkylation reaction increased the molecular weight of the blend polymer. The low molecular weight part disappeared with reactive blending. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1837–1849, 2003     

MODIFICATION OF POLYETHYLENE BY in situ FORMED SODIUM ACRYLATE

To improve the water tree resistance of PE, linear low-density polyethylene （LLDPE） was compounded with sodium acrylate （NaAA） for in situ polymerization, in which NaAA was fbrmed through the neutralization of acrylic acid （AA） with sodium hydroxide （NaOH） before adding dicumyl peroxide （DCP） to initiate the in situ graft polymerization and homo polymerization. A series of LLDPE/NaAA compounds were investigated for their water absorption ratio （WAR） measurement, water treeing, mechanical and dielectric properties. The results strongly suggest that NaAA can improve the water tree resistance of LLDPE. In addition, the LLDPE/NaAA compounds possess satisfactory mechanical properties and dielectric properties. Characterization of LLDPE/NaAA compounds by using Fourier transform infrared spectrometry （FTIR） suggests that the neutralization and polymerization reaction could be achieved effectively. Using adequate DCP content is the key factor for controlling the polymerization of NaAA with precise conversion ratio.     

聚丙烯共混物一步法反应共混增容的研究

研究了影响聚丙烯／（丙烯腈 苯乙烯）共聚物（ＰＰ／ＡＳ）合金反应挤出生成的各项因素,发现在过氧化二异丙苯（ＤＣＰ）存在的条件下进行反应共混可以发生接枝反应,生成ＰＰ与ＡＳ的相互接枝物．接枝物的生成显著地细化了分散相粒子,改善了合金相形态．为抑制反应共混过程中聚丙烯的降解,同时促进接枝反应,在ＰＰ／ＡＳ／ＤＣＰ反应共混中加入了含适量双键组分的添加剂亚油酸三甘酯（ＧＴＬ）．结果发现,较少量ＧＴＬ的加入就显著抑制了聚丙烯的降解,且进一步改善了合金的相形态．在合适的ＧＴＬ与ＤＣＰ用量下,反应共混不但显著改善了ＰＰ／ＡＳ合金的相形态,而且提高了合金的力学性能,初步确立了聚丙烯共混物一步反应共混挤出增溶的方法．     

线形低密度聚乙烯／废胶粉热塑弹性体动态硫化性能研究

利用动态硫化法制备了线形低密度聚乙烯(LLDPE)/废胶粉(GTR)热塑弹性体。重点研究了两种交联剂:硫和过氧化二异丙苯(DCP)对共混物性能的影响。加入一定量的苯乙烯-丁二烯-苯乙烯(SBS)共聚物作为增容剂。结果表明,经过DCP动态硫化后的共混物的力学性能比简单共混的共混物有明显的提高,而加入硫磺体系对共混物力学性能影响不大甚至有所下降。通过红外光谱、热分析(DSC)和扫描电镜(SEM)对共混物的热行为和表面形态研究表明,加入DCP交联剂使LLDPE、SBS和胶粉之间发生了交联反应,从而增加了胶粉颗粒与LLDPE间的界面相容性,使其热塑性弹性体的力学性能得以提高。     

HIPS／PP熔融反应共混及其动态力学性质

研究了高抗冲聚苯乙烯（HIPS）／聚丙烯（PP）共混物在过氧化二异丙苯（DCP）存在下的熔融反应过程及其动态力学性质．HIPS在DCP存在下以聚苯乙烯（PS）的降解为主，伴随着聚丁二烯（PB）的交联和接枝，PP在DCP存在下以降解为主，HIPS／PP在DCP存在下以PP同HIPS的反应接枝为主，这种原位生成的增容剂显著地改善了HIPS／PP两组份间的相容性，其分子运动特征较前两者发生明显变化，PS的Tg下降，PB和PP的Tg升高．     

Calytic Degradation of Mixed Plastics Using Natural Clinoptilolite Catalyst

Catalytic degradation of the mixture of polyethylene (PE), polypropylene (PP), and polystyrene (PS) was investigated in a semi-batch reactor. The main degradation product was liquid oil with gasoline range carbon number distributions. Clinoptilolite a natural zeolite (HNZ) showed as good a catalytic performance as silica-alumina (SA). The protonated catalysts (HNZ, HZSM-5) showed an increased production of ethylbenzene, but a decrease of styrene production. Increase of degradation temperature resulted in a decrease of ethylbenzene and propylbenzene, but an increase of styrene. Thermogravimetric analysis revealed that the increased degradation rate in the mixed plastics came from the intermolecular carbenium ion transfer between the degraded fragments of PE, PP, and PS.This revised version was published online in December 2005 with corrections to the Cover Date.     

Effects of different types of polyethylene on the morphology and properties of recycled poly(ethylene terephthalate)/polyethylene compatibilized blends

Recycled poly(ethylene terephthalate) (R‐PET) was blended with four types of polyethylene (PE), linear low density polyethylene (LLDPE; LL0209AA, Fs150), low density polyethylene (LDPE; F101‐1), and metallocene‐LLDPE (m‐LLDPE; Fv203) by co‐rotating twin‐screw extruder. Maleic anhydride‐grafted poly(styrene‐ethylene/butyldiene‐styrene) (SEBS‐g‐MA) was added as compatibilizer. R‐PET/PE/SEBS‐g‐MA blends were examined by scanning electron microscopy (SEM), differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), and mechanical property testing. The results indicated that the morphology and properties of the blends depended to a great extent on the miscibility between the olefin segments of SEBS‐g‐MA and PE. Due to the proper interaction between SEBS‐g‐MA and LDPE (F101‐1), most SEBS‐g‐MA, located at the interface between two phases of PET and LDPE to increase the interfacial adhesion, lead to better mechanical properties of R‐PET/LDPE (F101‐1) blend. However, both the poor miscibility of SEBS‐g‐MA with LLDPE (LL0209AA) and the excessive miscibility of SEBS‐g‐MA with LLDPE (Fs150) and m‐LLDPE (Fv203) reduced the compatibilization effect of SEBS‐g‐MA. DSC results showed that the interaction between SEBS‐g‐MA and PE obviously affected the crystallization of PET and PE. DMA results indicated that PE had more influence on the movement of SEBS‐g‐MA than PE did. Copyright © 2010 John Wiley & Sons, Ltd.     

GMA和共单体对聚乙烯木塑复合材料的直接反应增容

通过甲基丙烯酸缩水甘油酯(GMA)、聚乙烯(PE)、木粉和其它助剂的熔融挤出,实现了GMA及GMA与共单体对PE和木粉的直接反应增容.通过扫描电镜(SEM)观测了PE基木塑复合材料(WPC)的冲击断面形貌.测试了WPC经抽提后所得木粉的傅立叶变换红外光谱(FTIR)和WPC的力学性能及热变形温度(HDT).研究了共单体苯乙烯(St)和抑交联剂亚磷酸三苯酯(TPP)对反应增容的影响.结果显示,经GMA和引发剂反应增容后,有部分PE分子键合到了木粉粒子上,从而增强了木塑两相的结合力;St的加入有利于提高GMA的接枝率,导致更多PE分子键合到了木粉粒子上,而TPP的加入则使GMA的接枝率有所下降.经GMA和引发剂直接反应增容后,WPC的力学性能和HDT均明显改善;St的加入有助于抑制PE的交联,但并未造成WPC力学性能和HDT的明显劣化;同时加入St和TPP后,WPC的HDT有所下降,而断裂伸长率和冲击强度则明显提高.