氧化还原引发降解天然橡胶与丙烯酸酯共聚的研究

研究了降解天然橡胶胶乳与丙烯酸甲酯、丙烯酸丁酯的聚合，以过氧化苯甲酰—N，N—三甲基苯胺(BP0—DMA)为氧化还原引发剂，考察了不同反应温度、引发剂配比、乳化剂用量及加料方式对单体转化率和接枝率的影响；用红外光谱对共聚物进行了表征。结果表明，采用乳化还原引发剂可使聚合反应低温快速进行，过量还原剂起阻聚作用，采用复合乳化剂可提高聚合反应速度和乳液稳定性，补加料可提高接技率。     

Process variables and their effects on grafting reactions of styrene and methyl methacrylate onto natural rubber

The graft copolymerization of styrene and methyl methacrylate onto natural rubber latex was studied under various reaction conditions using a cumene hydroperoxide redox initiator. The monomer conversion, graft copolymer compositions, and grafting efficiency were determined. The synthesized graft copolymers were purified and then characterized by proton nuclear magnetic resonance (¹H‐NMR) analysis and differential scanning calorimetry (DSC). A 2 fractional factorial experimental design was applied to study the main effects on the grafting. The variables investigated in this work were the amount of the initiator and emulsifier, the presence or absence of a chain‐transfer agent, the styrene‐to‐methyl methacrylate ratio, the monomer‐to‐rubber ratio, and the reaction temperature. The measured response for the experimental design was the grafting efficiency. The analysis of the results from the design showed the sequence of the main effects on the observed response of the grafting of styrene and methyl methacrylate onto natural rubber, in ascending order. The amount of the chain‐transfer agent and the reaction temperature in the range of the test had significant effects and one marginally significant effect was the monomer‐to‐rubber ratio. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 63–74, 2003     

氯丁橡胶/苯乙烯/甲基丙烯酸甲酯/丙烯酸接枝共聚物的合成

以苯乙烯(St)、甲基丙烯酸甲酯(MMA)、丙烯酸(AA)为接枝单体,以过氧化二苯甲酰(BPO)为引发剂,在氯丁橡胶(CR)上进行接枝共聚,制备出CR／St／MMA／AA四元接枝共聚物。用红外光谱(IR)和差热分析(DSC)对接枝共聚物进行了表征,探讨了提取剂和提取时间对四元接枝共聚物的接枝率测定的影响,并讨论了St／MMA质量比、AA用量对接枝率和单体转化率的影响。结果表明,选用丙酮作提取剂。提取时间为48h,能达到最佳的萃取效果;BPO质量分数为CR的1．3％～1.6％。CR／St/MMA／AA四元接枝共聚物的质量比为100／30／30／15时,其接枝率和单体转化率最佳;与CR相比,四元接枝共聚物的结晶性降低,极性增强。     

Effects of redox initiator on graft copolymerization of methyl methacrylate onto natural rubber

Effects of cumene hydroperoxide (CHPO)/tetraethylene pentamine (TEPA), tert‐butyl hydroperoxide (TBHPO)/TEPA, and potassium persulfate (K₂S₂O₈)/sodium thiosulfate (Na₂S₂O₃) redox initiator on methyl methacrylate (MMA) grafted natural rubber by emulsion polymerization were investigated. The optimum reaction condition for each redox initiator on the grafting of natural rubber was studied. The grafted poly(methyl methacrylate) (PMMA) stays on the surface of rubber particles. CHPO dissolves very well in the oil phase and TBHPO dissolves moderately in the oil phase, and K₂S₂O₈ /Na₂S₂O₃ initiation is water‐soluble. Each can interact with TEPA in the aqueous phase. CHPO was found to give a higher grafting efficiency. To promote a greater grafting efficiency and yield a lower homopolymer content of PMMA, vinyl neo‐decanoate (VneoD) was added. Percentages of grafting of MMA on natural rubber latex initiated by CHPO/TEPA, TBHPO/TEPA, and K₂S₂O₈/K₂S₂O₃ of 84.4, 74.5, and 61.1, respectively, were in good agreement with percentages of PMMA in the aqueous phase as 7.2, 12.0, and 17.9 by CHPO, TBHPO, and K₂S₂O₈. VneoD produces allylic radicals on polyisoprene chains, favoring the grafting reaction with other vinyl monomers. CHPO/TEPA is thus a better redox system for grafting of MMA monomer on natural rubber latex. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2587–2601, 2006     

可接枝型氯丁橡胶与甲基丙烯酸甲酯接枝共聚工艺剖析

从反应系统残留氧的影响,搅拌强度及溶剂３个方面分析了可接枝型氯丁橡胶与甲基丙烯酸甲酯接枝共聚的工艺控制情况,提高了接枝共聚的重现性。     

国产氯丁胶和MMA的接枝共聚研究

研究了国产CR - 2 4 4可接枝氯丁胶 (CR)和甲基丙烯酸甲酯 (MMA)的接枝共聚反应 ,并成功地进行了 0 .1m3和 1 .0m3的扩试生产。     

苯乙烯、丙烯腈与降解天然胶乳的共聚研究

以BPO-FeSO4为氧化还原引发体系，采用种子乳液聚合技术，在降解天然胶乳DNR粒子上接枝共聚苯乙烯(St)和丙烯腈(AN)，用正交实验法研究了较佳反应条件，考察反应温度、反应时间及投料比对单体转化率、接枝率和接枝效率的影响，并用红外光谱对共聚物进行表征。     

CR/CPVC/MMA三元接枝共聚物

研究了高氯含量的氯化聚氯乙烯（CPVC）对氯丁橡胶／甲基丙烯酸甲酯接枝共聚合的影响,用红外光谱法和差热分析法对改性粘合剂进行了表征,结果表明,使用CPVC不仅明显提高粘合剂PVC材料的粘接强,而且还降低了成本。     

微波法接枝改性天然胶乳的制备与表征

采用微波辐射的方法对天然浓缩胶乳进行接枝改性,单体选用甲基丙烯酸甲酯,考察了微波温度、时间、引发剂和单体用量对接枝率、接枝效率的影响,用傅里叶变换红外光谱仪、核磁共振波谱仪来表征接枝产物。结果表明,微波法接枝改性天然胶乳的方法是可行的;适宜的反应条件为:采用过硫酸钾和亚硫酸钠作为引发剂,其用量为0.4%(占橡胶质量的百分数),微波温度为80℃,反应时间为1～2h,单体与胶乳质量比为1∶1。     

氧化还原引发木薯淀粉与丙烯酰胺接枝共聚的研究

以木薯淀粉和丙烯酰胺为原料,采用氧化还原引发体系合成淀粉-丙烯酰胺接枝共聚物,研究了温度、引发剂浓度、单体浓度以及反应时间对聚合反应的影响。结果表明：采用氧化还原引发剂可以使聚合反应低温快速进行。实验最佳条件：反应温度为40℃,引发剂浓度为4mmol／L,单体质量浓度为85mg／mL,反应时间为3h。     

Effect of Functionalization of Lignocellulosic Fibers on Their Physico-Chemical and Thermal Properties

In this paper Agave fiber has been functionalized through graft copolymerization and physico-chemical and thermal properties have been investigated. The graft copolymerization of methyl methacrylate and acrylonitrile onto Agave americana fibers was carried out under pressure using ceric ammonium nitrate as redox initiator. The chemical resistance studies were carried out in hydrochloric acid and sodium hydroxide. Water absorption studies were also carried out by exposing grafted fibers to accelerated weathering under different humidity levels ranging from 40 to 95%. Characterization of functionalized fibers was done through Fourier Transform Infra Red spectroscopy, scanning electron microscopy, and X-ray diffraction techniques.     

Studies on graft copolymerization of cyclohexyl methacrylate onto chloroprene rubber

Graft copolymerization of cyclohexyl methacrylate (CMA) onto chloroprene rubber (CR) was carried out in toluene using benzoyl peroxide as an initiator. The graft copolymer was isolated from the gross polymer by extracting it with a butanone solution. Infrared (IR) spectra of the graft copolymer showed the occurrence of grafting. Optimization of various parameters of the grafting, namely, time, temperature, and initiator concentrations, was performed. The mechanical adhesive properties of the graft copolymer, CR-g-CMA, were measured and compared with those of the graft copolymer of methyl methacrylate (MMA) onto CR, CR-g-MMA. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1733–1737, 1997     

Graft copolymerization of acrylonitrile and methyl methacrylate monomer mixtures on crumb natural rubber

Graft copolymerization of mixtures of acrylonitrile and methyl methacylate on crumb natural rubber was carried out in toluene at 60°C. The nitrogen content of the grafted copolymer was determined by elemental analysis and used to estimate the composition of the copolymer samples. It was found that the amount of acrylonitrile monomeric units incorporated into the polymer was disproportionately lower than the acylonitrile content of the feed and explanations in terms of the e‐value of the monomers and the inherent heterogenous nature of the polymerization mixture were offered. The miscibility of the natural rubber‐g‐polyacrylonitrile‐co‐poly(methyl methacrylate) with poly(vinyl chloride) was studied by viscometry, differential scanning calorimetry, and phase contrast microscopy. It was found that the natural rubber‐g‐polyacrylonitrile‐co‐poly(methyl methacrylate) formed semimiscible blends with poly(vinyl chloride). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1872–1877, 2002; DOI 10.1002/app.10474     

Graft copolymerization of methyl methacrylate onto sago starch using ceric ammonium nitrate and potassium persulfate as redox initiator systems

The graft copolymerization of methyl methacrylate (MMA) onto sago starch was carried out in aqueous media by different initiators of ceric ammonium nitrate (CAN) and potassium persulfate (PPS) and under a nitrogen gas atmosphere. Using CAN as an initiator, the maximum percentage of grafting (%G) was ascertained to be 246% at the following optimum conditions: a 70°C reaction temperature, a 2‐h reaction period, 2.0 mmol of CAN, 0.4 mmol of nitric acid, and 141 mmol of MMA. The maximum %G achieved with PPS as the initiator was 90%. The optimum conditions were a 50°C reaction temperature, a 1.5‐h reaction period, 47 mmol of monomer, and 1.82 mmol of PPS. The grafting of MMA onto sago starch was confirmed by the IR spectra of pure sago starch, MMA, and MMA grafted sago starch. This material may have application as a biodegradable plastic. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1375–1381, 2001     

Natural rubber‐g‐methyl methacrylate/poly(methyl methacrylate) blends

The grafting of the methyl methacrylate (MMA) monomer onto natural rubber using potassium persulfate as an initiator was carried out by emulsion polymerization. The rubber macroradicals reacted with MMA to form graft copolymers. The morphology of grafted natural rubber (GNR) was determined by transmission electron microscopy and it was confirmed that the graft copolymerization was a surface‐controlled process. The effects of the initiator concentration, reaction temperature, monomer concentration, and reaction time on the monomer conversion and grafting efficiency were investigated. The grafting efficiency of the GNR was determined by a solvent‐extraction technique. The natural rubber‐g‐methyl methacrylate/poly(methyl methacrylate) (NR‐g‐MMA/PMMA) blends were prepared by a melt‐mixing system. The mechanical properties and the fracture behavior of GNR/PMMA blends were evaluated as a function of the graft copolymer composition and the blend ratio. The tensile strength, tear strength, and hardness increased with an increase in PMMA content. The tensile fracture surface examined by scanning electron microscopy disclosed that the graft copolymer acted as an interfacial agent and gave a good adhesion between the two phases of the compatibilized blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 428–439, 2001     

Graft copolymerization of methyl methacrylate onto jute fiber initiated by cerium(IV)–DMSO redox initiator system

The kinetics of graft copolymerization of methyl methacrylate (MMA) onto chemically modified jute fibers initiated by the Ce(IV)–DMSO redox system was studied in the temperature range of 40–60°C. By studying the effects of the concentration of the monomer, Ce(IV), and DMSO on the rate of grafting, the optimum conditions for grafting were determined. Also, the effect of temperature, time, concentration of the acid, the amount of jute fiber, and some inorganic salts and organic solvents on the rate was investigated. A kinetic scheme was proposed on the basis of the experimental findings. Infrared spectra of chemically modified jute and grafted jute was investigated. More than 120% of grafting could be achieved with the present system. The characterization of MMA-grafted chemically modified jute by TGA and DTA studies was made. The thermal stability of the jute fibers was improved by grafting. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2569–2576, 1998     

Surface modification of natural rubber film by UV‐induced graft copolymerization with methyl methacrylate

Methyl methacrylate (MMA) was directly grafted on natural rubber (NR) or sulfur prevulcanized (SP) NR surface. The rubber sheet was primarily treated with argon plasma, followed by exposure to air for generating active functional groups. After immersing in a mixture of 30% hydrogen peroxide and MMA in ethanol and water (1 : 1), the MMA grafting took place after UV‐irradiation for 30–120 min. Results from the contact angle measurement and attenuated total reflection–Fourier transform infrared (ATR‐FTIR) spectroscopy showed that the highest amount of MMA grafting was achieved when using 13 wt % of MMA and UV irradiation time of 60 min. The tensile strength and percentage elongation at break of the modified SPNR sheet, having similar MMA grafting to that of NR, were in acceptable range as indicated in the standard glove's test (ASTM D3577). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2270–2276, 2007     

含丁二烯链段的不饱和合成橡胶的接枝改性研究进展

对含有丁二烯链段的3种不饱和合成橡胶,如丁苯橡胶、聚丁二烯橡胶和丁腈橡胶的接枝机理、接枝方法以及接枝产物的研究进展进行了综述,展望了不饱和合成橡胶接枝改性技术的前景。     

Grafting of butyl acrylate and methyl methacrylate on butyl rubber using electron beam radiation

Being nonpolar in nature, butyl rubber (IIR) has poor compatibility toward polar polymers and fillers. It can be improved by grafting polar substrates on the butyl elastomer. Radiation‐induced polymer processing is getting increasing interest, as it leads to new and improved polymers with desirable and interesting properties. In this investigation, electron beam radiation has been used to graft methyl methacrylate (MMA) and butyl acrylate (BA) on IIR. This process has several advantages over conventional grafting processes such as cationic polymerization (which needs very low temperature and stringent reaction conditions) and solution radical polymerization (which often needs solvent removal and recycling). The grafted polymers were characterized by using ¹H NMR, IR, TGA, and SEM analysis. The degree of grafting increases with a decrease in irradiation dose as well as with an increase in monomer concentration. It was observed that there was a decrease in intrinsic viscosity in irradiated IIR samples, indicating the chain scission. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1340–1346, 2006     

From a laboratory to a pilot scale production of natural rubber grafted with PMMA

Graft copolymers of natural rubber and poly (methyl methacrylate) (NR‐g‐PMMA) were prepared in a laboratory scale, and then extended to a pilot scale production. Reaction conditions were first assessed based on a preparation in the laboratory scale with a reactor capacity of 1.5 l. An optimum grafting efficiency was obtained when cumene hydroperoxide/tetraethylenepentamine (CHP/TEPA) redox initiator was used at the reaction temperature and time of 50°C and 3 h, respectively. MMA monomer was used without purification in the polymerization process comparing with the purified one by means of extraction. It was found that only a slight decrease of grafting efficiency was observed when the nonpurified monomer was used in the reaction. The nonpurified monomer was therefore used to prepare the NR‐g‐PMMA in a pilot scale production with a reactor capacity of 260 L. Various weight ratios of NR/MMA at 50/50, 60/40, 70/30, and 85/15 were studied. The resulting graft copolymers were characterized by FTIR and ¹H‐NMR techniques. It was found that increasing concentration of MMA caused an increase of free PMMA (i.e., homopolymer) but a decrease of free NR (i.e., ungrafted NR) and grafting efficiency. Quantity of grafted PMMA on the NR backbone was estimated using the integrated peak areas of ¹H‐NMR spectra and quantitative analysis by extraction method. The results were found to be in good agreement. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009