聚酯纤维光接枝丙烯酸聚合反应动力学研究

实验考察了聚酯纤维接枝丙烯酸体系聚合温度、引发剂浓度、单体浓度与初始接枝聚合速率的依赖关系,结果表明光敏剂浓度与接枝率呈1.08次方关系,与单体浓度呈1.37次方关系。基于聚酯纤维光接枝聚合的终止反应主要是自由基单基终止反应的假设提出了相应的接枝聚合机理,并建立了聚合速率模型。聚合温度服从Arrhenius关系,得出了聚酯纤维接枝丙烯酸聚合反应表观活化能为29.33kJ/mol。     

聚丙烯固相接枝丙烯酸聚合动力学及其接枝聚合速率模型

基于自由基固相接枝聚合的终止反应主要是自由基单基终止反应的假设提出了相应的聚合机理,并建立了聚合速率模型,聚合速率与引发剂浓度呈1次方、与单体浓度呈小于1次方关系,与聚合温度服从Arrhenius关系.实验考察了聚丙烯固相接枝丙烯酸体系聚合温度、引发剂浓度、单体浓度与初始接枝聚合速率的依赖关系,这一关系与上述速率模型十分吻合.采用无约束非线性优化方法得到了各参数的全局最优解：频率因子为6.868×10⁹,表观活化能为58.89 kJ•mol^-1,单体浓度的幂为0.78.     

反相乳液法mSt-g-AM接枝共聚反应的动力学模型

采用反相乳液法进行淀粉与丙烯酰胺接枝共聚反应的机理研究,考察以过硫酸铵引发机械活化淀粉(mSt)与丙烯酰胺(AM)接枝共聚反应速率Rg与引发剂浓度[I]、乳化剂浓度[E]、单体浓度[M]和淀粉浓度[mSt]的关系,推导并验证该反应体系的动力学模型及反应机理。结果表明,本实验得出的动力学关系式为:[][][][]1.24 0.76 1.54 0.33gR∞mSt I M E,与理论推导出的动力学关系式:[][][][]0.5~1 0.5~1 1~1.5 0.6pR∞mSt I M E基本一致,机械活化淀粉与丙烯酰胺在反相乳液中进行接枝共聚反应符合自由基聚合机理;在聚合过程中,引发剂分解副反应、诱导分解及"笼壁效应"导致引发效率降低,单基终止和双基终止反应同时存在;推导出共聚物消耗单体量与参加反应单体总量的比值(X):[][][][][][][]0.5 0.50.5 0.5 0.5 0.51 2 31/X=1+KM/mSt+KmSt I/M+KI/mSt,单体浓度、淀粉乳浓度和引发剂浓度对其有重要影响。     

聚丙烯固相接枝马来酸酐的研究

用固相接枝法在聚丙烯(PP)分子链上接枝马来酸酐(MAH),制备功能化聚丙烯。重点讨论了反应时间和反应温度以及单体浓度和引发剂浓度对接枝产物PP-g-MAH接枝率的影响。在其他条件不变的情况下,当反应时间为2h,反应温度为120℃,单体与PP的质量比为1∶1,引发剂用量为2.5%时,最大接枝率可达到1.6%。采用红外光谱表征了PP-g-MAH。     

淀粉接枝共聚动力学研究

以硝酸铈铵为引发剂,研究了MMA、BA、AA和MMA-BA混合单体在木薯淀粉上的接技共聚反应;考察了聚合温度、单体的浓度、种类和配比、引发剂用量等因素对转化率、聚合速率、接枝率和接枝效率的影响。结果表明,随着聚合温度和引发剂用量的上升,接枝效率均上升;单体浓度上升,接枝率、初始聚合速率和最终转化率也上升,但接枝效率则下降;接枝率和接枝效率依MMA>BA>AA的顺序递降,使用MMA—BA混合单体则介于二者之间。     

马来酸酐及苯乙烯同时接枝聚丙烯的研究

用过氧化二异丙苯(DCP)作为引发剂，采用双螺杆反应挤出的苯乙烯、马来酸酐2种单体同时接枝聚丙烯．研究了单体总浓度、单体比例、引发剂浓度对PP的接枝率、接枝效率和熔体流动速率的影响。通过实验发现苯乙烯的加入使接枝率和接枝效率比单独的马来酸酐接枝都有很大的提高。     

固相接枝双单体制备极性聚丙烯的研究

以马来酸酐(MAH)和甲基丙烯酸(MAA)为复合单体,采用固相接枝法,制备了具有高极性的接枝聚丙烯[PP-g-(MAA/MAH)]样品;并表征与分析了该接枝物结构,研究了反应时间、反应温度、复合单体用量和引发剂浓度对接枝率和润湿角的影响.结果表明:当反应时间为105 min,反应温度是125℃,复合单体用量8 g/100gPP,引发剂用量为0.4 g/100g PP时,能够制备出接枝率4.01%的PP-g-(MAA/MAH).     

苯乙烯/丙烯酸丁酯交联体系乳液聚合动力学研究

以十二烷基苯磺酸钠(SDBS)为乳化剂,过硫酸钾(KPS)引发苯乙烯/丙烯酸丁酯(St/BA)乳液共聚,加入二甲基丙烯酸乙二醇酯(EGDMA)、聚丁二烯生胶(PB)作为交联剂,研究了聚合温度、引发剂浓度、乳化剂浓度、单体配比对聚合速率的影响。实验结果表明,共聚体系的表观活化能为70.67kJ/mol,聚合初始速率与引发剂浓度的0.43次方、乳化剂浓度的0.56次方和单体BA的0.49次方成正比。     

淀粉与丙烯酰胺的接枝共聚

本文研究了在硝酸铈铵作用下，淀粉和丙烯酰胺接枝共聚合的反应规律，探讨了引发剂浓度、单体浓度、ｐＨ值、反应时间和反应温度对接枝聚合的影响，并对不同的引发体系引发淀粉—丙烯酰胺接枝聚合进行了比较，结果表明，以硝酸铈铵引发的淀粉—丙烯酰胺接枝聚合所产生的均聚物少，引发效率高。     

增容剂甲基丙烯酸丁酯接枝聚丙烯的研究*

以甲基丙烯酸丁酯(BMA)为接枝单体,过氧化苯甲酰(BPO)为引发剂,采用固相接枝技术对聚丙烯(PP)进行改性,制备了BMA接枝PP (PP-g-BMA)。研究了接枝反应工艺条件对接枝率的影响,采用傅立叶变换红外光谱表征与分析了PP-g-BMA,并对PP-g-BMA在PP/聚对苯二甲酸乙二酯(PET)共混物中的增容作用进行了验证。结果表明,当反应温度为130℃、引发剂的质量分数为6%、单体BMA质量分数为10%,接枝反应3 h,成功制得了接枝率为3.75%的PP-g-BMA;PP-g-BMA可明显改善PP/PET共混物的界面相容性,相对于PP-g-MAH,其增容的PP/PET共混物的力学性能和加工流变性能更好。     

Polymerization of methyl acrylate in the presence of ultrasound and peroxodisulfate

A systematic polymerization kinetic study of methyl acrylate with an added initiator, peroxodisulfate, in the presence of low‐power ultrasound was done. The polymerization experiments were conducted at various concentrations of monomer and initiator at different temperatures (303–323 K). The polymerization was found to proceed without an induction period, and the steady state was attained in a fairly short time. The rate of monomer disappearance showed a second‐order dependence on monomer concentration. The chain lengths of the polymer were calculated, and we found that the chain length increased with increasing monomer concentration and decreased with increasing initiator concentration. The reaction scheme proposed is based on the kinetic studies that indicated linear termination by sulfate‐ion‐radical‐incorporating direct reaction between the monomer and the initiator. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Radical polymerization of acrylonitrile initiated by α-picolinium p-chlorophenacylid

The radical polymerization of acrylonitrile (AN) with α-picolinium p-chlorophenacylid (α-PCPY) as initiator using carbon tetrachloride as inert solvent was investigated at 50°C. The polymerization follows ideal kinetics: the exponent values calculated for the initiator and monomer were found to be 0.5 and unity, respectively. A free radical mechanism with bimolecular termination was confirmed by the inhibiting effect of hydroquinone, a radical quencher. The rate of polymerization was a direct function of initiator (α-PCPY) concentraction, monomer (AN) concentration and temperature. The overall activation energy calculated was 56 kJ/mol. The polymerization was favoured by polar solvents and retarded by non-polar solvents.     

丙烯酸丁酯改性C_9石油树脂的研究

利用丙烯酸丁酯改性C9石油树脂,以AIBN为引发剂,以正庚烷为溶剂,采用自由基溶液聚合法合成了C9石油树脂/丙烯酸丁酯接枝共聚物。采用单因素实验和正交实验,考察了反应中单体的选择、单体用量、引发剂用量、反应温度、反应时间对接枝率以及单体转化率的影响。最佳反应条件为:反应温度为80℃,反应时间为4 h,引发剂用量为0.75 g,丙烯酸丁酯的用量为12%,在此条件下,产物的接枝率为27.03%。红外光谱分析证实了接枝产物的生成。     

Graft polymerization of vinyl acetate onto silica

The free‐radical graft polymerization of vinyl acetate onto nonporous silica particles was studied experimentally. The grafting procedure consisted of surface activation with vinyltrimethoxysilane, followed by free‐radical graft polymerization of vinyl acetate in ethyl acetate with 2,2′‐azobis(2,4‐dimethylpentanenitrile) initiator. Initial monomer concentration was varied from 10 to 40% by volume and the reaction was spanned from 50 to 70°C. The resulting grafted polymer, which was stable over a wide range of pH levels, consisted of polymer chains that are terminally and covalently bonded to the silica substrate. The experimental polymerization rate order, with respect to monomer concentration, ranged from 1.61 to 2.00, consistent with the kinetic order for the high polymerization regime. The corresponding rate order for polymer grafting varied from 1.24 to 1.43. The polymer graft yield increased with both initial monomer concentration and reaction temperature, and the polymer‐grafted surface became more hydrophobic with increasing polymer graft yield. The present study suggests that a denser grafted polymer phase of shorter chains was created upon increasing temperature. On the other hand, both polymer chain length and polymer graft density increased with initial monomer concentration. Atomic force microscopy–determined topology of the polymer‐grafted surface revealed a distribution of surface clusters and surface elevations consistent with the expected broad molecular‐weight distribution for free‐radical polymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 300–310, 2003     

Photoinitiated polymerization of 1-vinylimidazole

The polymerization of 1-vinylimidazole differs from that of 1-vinyl-2-methylimidazole in that degradative chain addition to the monomer is an important factor, as previously indicated by Bamford and Schofield. The consequence of this is a dependence of rate on monomer concentration, which starts with the first power but levels off to a constant rate or even decreases slightly as the initial monomer concentration rises to 1–4 mol/L. Thus, the mechanism proposed by Bamford and Schofield appears to be confirmed. Initiator dependence of rate is best correlated by using the light absorbed by the initiator rather than the initiator concentration as the independent variable. The 0.72 power dependence found may be higher than the expected 0.5 power because the rates were measured at a monomer concentration (0.25 mol/L) just beyond the linear region. Low values of activation energy are expected, since photoinitiation rate is independent of temperature. The measured value reflects only the propagation and termination steps. Even then, the value found of 1.5 kcal/mol is low compared to the value of 3.9 kcal/mol for 1-vinyl-2-methylimidazole.     

反相乳液五元体系淀粉接枝共聚反应动力学

研究了在淀粉/单体/乳化剂/油/水五元反相乳液体系中引发淀粉和丙烯酰胺接枝共聚反应的动力学,考察了引发剂和乳化剂浓度、单体和淀粉浓度、反应温度等因素对表观聚合速率的影响.结果表明：在本实验考察范围内单体浓度和淀粉浓度对聚合速率影响明显,聚合过程中快速链终止和慢速链终止反应同时存在,动力学关系式为：R_p∝［I］^0.93［M］^1.28［St］^1.47［E］^0.61,聚合速率随体系温度的升高而加快,在35～55℃范围内,聚合反应的表观活化能为82.01 kJ•mol^-1.     

“饥饿”反应器中自由基聚合动力学(Ⅱ)──甲基丙烯酸甲酯聚合动力学

对“饥饿”反应器中甲基丙烯酸甲酯（MMA）聚合行为进行详尽研究,建立了聚合动力学模型,模型中考虑了由于初级自由基与单体反应生成单体自由基时所消耗的单体量;考虑了PMMA的高温解聚作用;考虑了体系中的凝胶效应,并将链终止速率常数与凝胶效应联系起来,反映在模型中．通过实验,优化回归求取了模型参数．     

KINETICS OF RADICAL POLYMERIZATION IN A STARVED FEED REACTOR (Ⅱ)──KINETICS OF METHYLMETHACRYLATE POLYMERIZATION

对“饥饿”反应器中甲基丙烯酸甲酯（MMA）聚合行为进行详尽研究,建立了聚合动力学模型,模型中考虑了由于初级自由基与单体反应生成单体自由基时所消耗的单体量;考虑了PMMA的高温解聚作用;考虑了体系中的凝胶效应,并将链终止速率常数与凝胶效应联系起来,反映在模型中．通过实验,优化回归求取了模型参数．     

Ceric-induced grafting of ethyl-acrylate onto sodium alginate

Sodium alginate was graft-copolymerized with ethyl acrylate using ceric ammonium nitrate as an initiator. In order to optimize the conditions for grafting, the concentrations of nitric acid, initiator and monomer together with temperature, time and amount of substrate were varied. The kinetic scheme of free radical graft copolymerization has been proposed and the equations relating the values of rate of polymerization, rate of graft copolymerization and rate of homopolymerization are also suggested. The experimental results agree very well with the proposed kinetic scheme.