甲基丙烯酸缩水甘油酯/苯乙烯固相接枝聚丙烯

以苯乙烯(St)为共单体，过氧化苯甲酰(BPO)为引发剂，采用固相接枝反应将甲基丙烯酸缩水甘油酯(GMA)接枝到聚丙烯(PP)大分子链上。研究了反应时间、单体用量、引发剂用量等因素对接枝率的影响。采用凝胶渗透色谱(GPE)测定了PP和接枝物PP-g-(GMA-St)的分子量和分子量分布。结果 表明固相接枝PP反应条件为[GMA／[St]=2，反应3．5h，加入GMA 10份，BPO 5份。St的加入有助于GMA与PP的接枝，同时在一定程度上抑制了PP的降解。     

硅烷气相接枝水解交联聚丙烯

硅烷气相接枝水解交联聚丙烯;聚丙烯;气相接枝;硅烷交联     

Reactive processing of polymers: Effect of bifunctional and tri-functional comonomers on melt grafting of glycidyl methacrylate onto polypropylene

Two reactive comonomers, divinyl benzene (DVB) and trimethylolpropane triacrylate (TRIS), were evaluated for their role in effecting the melt free radical grafting reaction of the monomer glycidyl methacrylate (GMA) onto polypropylene (PP). The characteristics of the GMA-grafting systems in the presence and absence of DVB or TRIS were examined and compared in terms of the yield of the grafting reaction and the extent of the main side reactions, namely homopolymerisation of GMA (poly-GMA) and polymer degradation, using different chemical compositions of the reactive systems and processing conditions. In the absence of the comonomers, i.e. in a conventional system, high initiator concentrations of peroxides were typically required to achieve the highest possible GMA grafting levels which were found to be generally low. Concomitantly, both poly-GMA and degradation of the polymer by chain scission takes place with increasing initiator amounts. On the other hand, the presence of a small amount of the comonomers, DVB or Tris, in the GMA-grafting system, was shown to bring about a significant increase in the grafting level paralleled by a large reduction in poly-GMA and PP degradation. In the presence of these highly reactive comonomers, the optimum grafting system requires a much lower concentration of the peroxide initiator and, consequently, would lead to the much lower degree of polymer degradation observed in these systems. The differences in the effects of the presence of DVB and that of TRIS in the grafting systems on the rate of the GMA-grafting and homopolymerisation reactions, and the extent of PP degradation (through melt flow changes), were compared and contrasted with a conventional GMA-grafting system.     

Grafting of styrene onto low molecular weight polymers and copolymers of butadiene

The grafting of styrene onto low molecular weight polybutadienes and butadiene–styrene co-polymers was studied. A mathematical method was used for the design of experiments and for the determination of the optimum grafting conditions with respect to the conversion of styrene and the efficiency of grafting. The reaction parameters were temperature (65–105°C), time (2–10 hr), concentration of the initiator, polymer to monomer ratio (10/90–90/10) and dilution by solvent (toluene). The optimum grafting conditions were chosen under which 50–60 wt-% of styrene was grafted onto backbone polymer at a high conversion of the monomer. It was found that the reactions producing graft copolymer prevailed over the styrene homopolymerization when the temperatures employed were lower (65–85°C), and the reaction time (8–10 hr), backbone polymer/monomer ratio, and the dilution by solvent were higher. The efficiency, density, and degree of grafting were found to increase with the increase in the molecular weight of the backbone polymer. The efficiencies and densities of grafting onto low molecular weight polybutedienes were higher than those of grafting onto low molecular weight butadiene–styrene copolymers. Grafting efficiencies and grafting densities were in the ranges 37.8–61.6 wt % and 0.06–0.26, respectively, in the studied range of number-average molecular weights (M?_n = 2400–6000).     

Solid‐state modification of polypropylene (PP): grafting of styrene on atactic PP

Grafting of unsaturated vinyl monomers onto polypropylene (PP) is a convenient route to develop new polymeric materials with synergistic properties. Particular attention must be paid to the formation of graft copolymer relative to the formation of homopolymer, since the final properties are dependent both on the dispersion of the new polymer into the iPP matrix, which is controlled by the degree of grafting, as well as on the chemical nature of the in‐situ formed polymer chains. In the present work the grafting reaction of styrene on atactic PP (aPP), considered as good model system for the more studied solid‐state modification of isotactic PP (iPP), has been investigated in the presence of two different radical initiators in order to get a first insight into the grafting reactions onto PP. Several grafting reactions were carried out by changing the chemical compositions of the starting polymerization mixture, whose homogeneity was accurately investigated by Raman spectroscopy. Infrared‐spectroscopy (FT‐IR) was used for qualitative and quantitative characterization of the reaction product. A quantitative separation procedure, based on the concept of selective solvent extraction, has been established which enables the determination of the grafting efficiency (Φ) as well as the exact chemical composition of the final product. Finally, all products were characterized by means of Differential Scanning Calorimetry (DSC) in order to study their thermal behaviour.     

1,6-己二醇二丙烯酸酯和苯乙烯多单体熔融接枝制备长支链聚丙烯研究

采用哈克转矩流变仪制备了1,6-己二醇二丙烯酸酯(HDDA)和苯乙烯(St)多单体熔融接枝聚丙烯(PP)体系.红外测试结果表明St的加入能够促进HDDA接枝到PP主链,提高接枝率.动态流变行为研究结果也表明采用多单体熔融接枝PP更有利于体系在熔融接枝中生成长支链(LCB).随着St单体添加量的增加,HDDA的接枝率增大...     

Reactive compatibilization of blends of PET and PP modified by GMA grafting

The melt radical grafting of glycidyl methacrylate (GMA) onto isotactic polypropylene (PP) was carried out in Brabender internal mixer and the influence of reaction procedure, radical initiator concentration and addition of co-monomer (styrene) on the grafting efficiency was examined. The viscosity, the thermal behaviour and melt rheology of PP-g-GMA samples was then analysed as a function of grafted GMA content. Blends of poly(ethylene terephthalate) (PET) with PP and PP-g-GMA (5.2 wt% GMA), prepared in internal mixer, were characterised by SEM, DSC and melt viscosimetry. The morphological analysis of PET/PP-g-GMA blends (80/20, 50/50 w/w) pointed out a marked improvement of phase dispersion (with particle size of about 0.6 μm for 80/20 blend) and interfacial adhesion, as compared to non-compatibilized PET/PP blend. The results of mixing torque and thermal analysis supported the occurrence of in-situ compatibilization reaction between epoxy groups of GMA modified PP and carboxyl end-groups of PET in the melt.     

Exchange and free radical grafting reactions in reactive extrusion

The potential of two types of reactions for reactive extrusion was evaluated in our laboratory: exchange reactions of copolyesters and free radical grafting of monomers onto polyolefins. Specifically, the alcoholysis of ethylene and vinyl acetate copolymers, the transesterification of ethylene and alkyl acrylate copolymers (EAA) and the aminolysis of alkyl acrylate copolymers were investigated as the exchange reactions while the grafting of maleic anhydride (MA) onto polypropylene (PP) as the free radical reactions. The exchange reactions are very slow without catalysts. Tin derivatives, such as dibutyl tin dilaurate (DBTDL) and dibutyl tin oxide (DBTO), are good catalysts for the alcoholysis and the transesterification, but not for the aminolysis. For the latter, tautomeric compounds, such as 2-pyridone and 2-mercaptopyridone, are efficient. Comparative kinetic studies showed that, for all the three exchange reactions, the reacting medium (solution or the homogeneous melt) does not affect their reaction mechanisms nor their intrinsic rate constants. Additionally, mechanical mixing does not contribute to the overall reactions. As for the free radical grafting of MA, the presence of electron-donating monomers and styrene (ST) in particular was shown to be very effective in improving the grafting yield while minimising the degradation of PP. This was proven to be due to the formation of a charge transfer complex between MA and such a monomer.     

颗粒内受限聚合法制备PP/POE/PS合金

以等规聚丙烯/乙烯-辛烯共聚物(PP/POE)合金颗粒为扩散基体, 苯乙烯(St)为扩散单体, 利用颗粒内受限聚合法制备了PP/POE/PS三元合金. 结果表明, 对于POE质量分数为20%~40%的PP/POE合金颗粒, St均可扩散至直径为4 mm的颗粒中心部位, 在POE非晶相中生成相尺寸为几十至几百纳米的PS球. 在PP/POE合金颗粒的不同部位, 因POE相尺寸及单体的吸附量不同, 生成的PS相尺寸也不同, 在颗粒中心部位生成的PS球最小. 研究了St在PP/POE(质量比80: 20)颗粒中的扩散-聚合行为, 结果表明, St在合金颗粒中的扩散速率和扩散饱和值远大于在纯PP颗粒中的扩散速率和饱和值, 这主要是因为PP/POE合金颗粒中的非晶POE相有利于扩散. 改变单体投料量可以获得具有不同PS含量的PP/POE/PS三元合金. 结晶性能研究结果表明, PS在非晶POE相中的优先分布会使POE相体积增大, 从而使PP的结晶温度和熔融温度降低. 随着PS量的进一步增大, 分布在PP中的PS对PP有结晶成核作用.     

Graft Copolymerization of Poly(ethyl Acrylate) onto Wool in the Presence of Ceric Ammonium Nitrate as Redox Initiator

Poly(ethyl acrylate) has been grafted onto Himachali wool in an aqueous medium by using ceric ammonium nitrate (CAN) as redox initiator. Copolymerization was studied at five different temperatures: 40, 45, 50, 55, and 60°C. Maximum grafting occurred at 45°C. Nitric acid was found to catalyze the graft copolymerization reactions. Percentage and efficiency of grafting were found to be dependent upon concentrations of CAN (initiator) and of monomer. Percentage of grafting has been determined as function of time, and from the slope of percent grafting versus time plot, the initial rate of graft copolymerization (R) has been determined.     

Graft copolymerization of ethyl acrylate onto gelatin using hydrogen peroxide and ascorbic acid in aqueous medium

Gelatin a derived protein from collagen can be modified at 60°C by allowing it to react with ethyl acrylate by use of a novel initiator technique. The polymeric ethyl acrylate side chain is chemically bonded to gelatin. The effects of synthetic variable in the graft copolymerization reactions have been discussed in the light of percent grafting, grafting efficiency, and the rate of polymerization.     

Influence of Monomer and Initiator Concentrations on the Simultaneous Grafting of Several Monomers onto Insoluble Collagen

Simultaneous grafting of 2-hydroxyethyl methacrylate and methyl methacrylate (3:1 and 3:2 mole ratios) onto insoluble collagen with ceric ammonium nitrate as initiator was attempted with a view to optimizing conditions for the preparation of hydrogels. The influence of monomer and initiator concentrations on the grafting reactions was investigated. The grafting results are discussed in the light of grafting efficiency and percentage of grafting. They were found to be lower when the 3:1 mole ratio of monomers was used.     

Polymerization in nonuniform latex particles. III. Kinetics of grafting in emulsion polymerization

The concept of nonuniform distribution of free radicals in polymerizing latex particles has been incorporated into the development of a kinetic model for grafting reactions. This theory permits prediction of grafting efficiency as a function of reaction conditions. It can also be used for evaluation of rate constants for grafting reactions. Experimental data for emulsion polymerization of styrene in the presence of polybutadiene seed latex have been used to assess the proposed grafting theory. The predominant grafting reaction appears to be the attack of growing polystyrene chains on the allyl hydrogen atoms of polybutadiene. The results further reinforce the hypothesis that the entering oligomeric free radicals do not distribute uniformly within the particle volume.     

Toughened polypropylene with balanced rigidity (I): preparation and chemical structure of toughening master batch

The title toughening master batch (TMB) was synthesized in a low‐viscosity reaction system by using dynamic vulcanization technique starting from polypropylene (PP) as the matrix resin and ethylene–propylene or butadiene–styrene elastomer as the toughening agent through a polymer–bridge conjunction derived from a monomer containing a carbonate group in the presence of a free radical initiator. The chemical structure of the TMBs and the effects of technological conditions on structural parameters were investigated using fractional extraction and infrared spectroscopy. The prepared TMBs consisted of unreacted PP, unreacted elastomers, graft copolymer of PP and/or elastomers containing branched chains formed by bridging agent, and crosslinked copolymer of PP and/or elastomers in conjunction with polymer bridge chains derived from bridging agent. Results showed that the PP existed in graft and crosslinked forms was in the range of 3–21 wt% and that of the elastomer toughening agent was in the range of 50–70 wt%, grafting and bridging efficiency of bridging agent was in the range of 62–88 wt%, graft copolymer content in the total TMB was in the range of 0.18–3.65 wt% and crosslinked copolymer content was in the range of 22–42 wt%. Copyright © 2000 John Wiley & Sons, Ltd.     

Crystalline structure of polypropylene in blends with thermoplastic elastomers after electron beam irradiation

Isotactic polypropylene (PP) was blended in extruder with 0–50% addition of styrene–ethylene/butylene–styrene (SEBS) and styrene–butadiene–styrene (SBS) block copolymers. Granulated blends were irradiated with electron beam (60 kGy) and 1 week later processed with injection molding machine. Properties of samples molded from irradiated and non-irradiated granulates were investigated using DSC, WAXS, MFR, SEM and mechanical and solubility tests. It was found that the SEBS based systems are more resistant to irradiation in comparison to similar blends with SBS copolymer. Such behavior can be explained by the presence of double bonds in elastic SBS block. Irradiation of PP-SBS blends leads to considerable structure changes of crystalline and amorphous PP phases and elastic SBS phase. It indicates creation of new (inter)phase consisting of products of grafting and cross-linking reactions. Irradiated PP-SBS blends show significant improvement of impact strength at low temperatures.     

Fundamental studies of grafting reactions in free radical copolymerization. III. Grafting of styrene,acrylate, and methacrylate monomers onto cis-polybutadiene using benzoyl peroxide initiator in solution polymerization

Benzoyl peroxide (BPO), due to its higher radical reactivity as compared to AIBN, is known to promote grafting onto cis-polybutadiene. Switching from AIBN to BPO initiator made a dramatic difference in the extent of grafting for styrene and methacrylate monomers, but only a modest difference for acrylate monomer. For styrene and methacrylate monomers, graft site formation is due to BPO initiator radical attack onto the backbone via allylic hydrogen abstraction. Significant levels of grafting are achieved and depend upon the relative concentrations of monomer and backbone polymer but not upon the level of initiator. For acrylic monomer, graft site formation was found to be due to polymer radical attack at the double bond in the backbone. Abstraction of allylic hydrogen also occurs but results in retardation of the overall reaction rate. Graft level was dependent upon initiator and back-bone polymer concentrations but not upon monomer concentration. The effective role of the initiator is only to produce polymer radicals; the BPO has no direct role in the formation of effective graft sites. © 1995 John Wiley & Sons, Inc.     

马来酸酐-苯乙烯熔融接枝聚丙烯的影响因素及其性能研究

用单螺杆挤出机制备了马来酸酐 (MAH) 苯乙烯 (St)对聚丙烯 (PP)的多组分单体自由基熔融接枝体系 .研究证实了当两种单体物质的量比约为 1∶1时 ,接枝物的接枝率最高 ,而熔体流动速率 (MFR)最大 .对反应体系影响因素的研究表明单体用量和引发剂用量对不同单体用量比的系列接枝物的接枝率会产生不同的影响 ;另外 ,单体用量增加 ,接枝物的MFR减小 ,过氧化二异丙苯 (DCP)用量增加 ,接枝物的MFR增加 .对多单体熔融接枝聚丙烯PP g (MAH co St)的力学性能研究发现 ,选用合适的单体用量比、单体用量和DCP用量时 ,所制备的接枝物可具有与纯PP相当或更佳的力学性能     

Improved Graft Copolymerization of Some Modified Cellulose Polymers with Vinyl Monomers Using Dibenzoyl Peroxide (DBPO) as Initiator

An improved efficient method for grafting of mercerized cellulose with acrylonitrile, acylamide, 4-vinylpyridine and styrene monomers using dibenzoyl peroxide (DBPO) as an initiator was studied. The results show that the order of the reactivity of the monomers is styrene > 4- vinyl pyridine > acrylonitrile >acrylamide. Under optimal conditions, the extent of graft copolymerization of styrene onto cellulose has shown a substantial increasing trend. The percentages of grafting yield (G.Y.%), grafting efficiency (G.E.%), IR spectra, and X-ray diffraction were measured. The I t was shown that X-ray diffraction spectra of grafted cellulose increases one more peak than that of pure cellulose with a noticeable decrease in crystallinity.     

GMA/苯乙烯多组分单体接枝聚丙烯结晶行为研究

使用差示扫描量热计 (DSC)研究了甲基丙烯酸缩水甘油酯 苯乙烯 (GMA St)多单体熔融接枝聚丙烯[PP g (GMA co St) ]的等温和非等温结晶行为 ,用偏光显微镜观察了结晶的形态 ,并利用Avrami方程对其结晶动力学进行了分析 .研究发现接枝聚丙烯的结晶模式与PP相似 ,属于异相成核控制的球晶三维生长 ;但接枝聚丙烯的结晶温度 (Tc)显著提高 ,幅度高达 16～ 19℃ ,总结晶速率与纯PP相比明显加快 .接枝聚丙烯上GMA co St支链的存在 ,降低了成核界面自由能 ,促进了聚丙烯结晶的异相成核 .在接枝率不太高的情况下 ,随着接枝率的提高 ,接枝聚丙烯的结晶温度升高 ,总结晶速率加快 .在高接枝率范围内 ,随着接枝率的提高 ,接枝PP的Tc 不再升高 ,且由于接枝链的增长严重阻碍了球晶生长 ,导致接枝PP的总结晶速率反而随接枝率的升高而下降     

Radiation-induced grafting of styrene vapor to polyethylene

The radiation-induced grafting of styrene vapor to low-density polyethylene film of 0.063 mm thickness was studied at 23°C at a dose rate of 1.98 × 10⁴ rad/hr. The concentration C of monomer in the film was measured as a function of pre-irradiation exposure time to monomer vapor. The concentration-dependent diffusion coefficient of styrene in polyethylene was calculated to be 4.9 × 10^?9 exp {2.0C/C₀} cm²/sec, where C₀ is the saturation concentration of styrene in the film, and a linear boundary diffusion coefficient for styrene vapor into polyethylene film was found to be 2.0 × 10^?7 cm/sec. The rate of grafting was determined as a function of the concentration of styrene absorbed in the film. The maximum graft yield was obtained with an initial styrene concentration in the film of 4 wt-%. Under conditions of low initial monomer concentration, the grafting rate increases with irradiation time. The results are compared with previously published data on grafting of polyethylene from methanol–styrene solutions. They are explained in terms of the viscosity of the amorphous region as a function of styrene content and the resistance to the diffusion of monomer at the film–vapor interface.