VAc、St不同乳液聚合方式的研究

对水溶性引发剂、有乳化剂存在的常规乳液聚合,水溶性引发剂无皂乳液聚合及有乳化剂存在的油溶性引发剂乳液聚合三种聚合方式,选择了水溶性相差较大的醋酸乙烯酯(VAc)和苯乙烯(St)两种单体,对其聚合动力学进行了比较,讨论了其不同的成核机理及单体水溶性对聚合速率的影响,考察了乳液的反应稳定性。结果表明聚合方式的不同、单体水溶性的不同对聚合动力学具有显著的影响。     

丙烯酰胺聚合物自由基聚合引发体系研究进展

丙烯酰胺类聚合物是应用较为广泛的水溶性高分子化合物,自由基聚合是大规模生产聚丙烯酰胺的有效方法。文章对自由基聚合偶氮类引发剂、氧化还原引发体系、复合引发体系的特点和研究应用进行了讨论,认为采用水溶性偶氮引发剂、含胺的氧化还原引发体系、含胺基功能性单体类引发剂等新型引发剂能制备高分子量的聚合物,合理设计新型复合引发体系可利于聚丙烯酰胺相对分子质量的进一步提高。     

乳液聚合法合成高相对分子质量聚醋酸乙烯酯的研究

本文采用过硫酸铵/亚硫酸氢钠氧化还原体系低温引发醋酸乙烯酯乳液聚合,分别讨论了聚合温度、单体用量、十二烷基硫酸钠(SDS)用量、过硫酸铵用量、亚硫酸氢钠用量等因素对聚醋酸乙烯酯粘均相对分子质量的影响。通过调节单体浓度、SDS浓度、过硫酸铵浓度、亚硫酸氢钠浓度和聚合温度,合成出高相对分子质量的聚醋酸乙烯酯,用GPC法对其进行表征,粘均相对分子质量为1.07×106,相对分子质量分布为2.75。     

氧化还原引发丙烯酸酯乳液共聚物的合成研究

本文以丙烯酸丁酯－苯乙烯－丙烯酸－丙烯酸羟乙酯为聚合体系，以过硫酸铵／亚硫酸氢钠为氧化还原引发剂。考察了不同氧化剂／还原剂用量、不同反应温度、不同乳化剂用量对单体转化率、特性上度、乳液稳定性的影响，并与过硫酸铵单组分引发进行了比较，用红外光谱（IR）和差热分析（DSC）对共聚物进行了表征。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，过量的还原剂起阻聚或缓聚的作用，采用复合乳化剂体系可提高聚合反应速度和乳液的稳定性，合成的共聚物为无规共聚物。     

乳液聚合法合成高相对分子质量聚醋酸乙烯酯的研究

采用过硫酸铵/亚硫酸氢钠氧化还原体系低温引发醋酸乙烯酯乳液聚合,合成出分子量为1.07×106、分子量分布为2.75的聚醋酸乙烯酯。讨论了聚合温度、单体用量、十二烷基硫酸钠(SDS)用量、过硫酸铵用量、亚硫酸氢钠用量等因素对聚醋酸乙烯酯黏均分子量的影响,并用GPC法对其进行表征。     

氯乙烯/异丁基乙烯基醚乳液共聚物的合成

以(NH4)2S2O8／Na2SO3／CuSO4为氧化-还原引发体系、十二烷基硫酸钠(SDS)为乳化剂，采用间歇乳液聚合合成氯乙烯／异丁基乙烯基醚(VC／IBVE)共聚物。结果表明，当投料单体中IBVE质量分数增加时,相同聚合时间的聚合转化率和共聚物特性粘度明显降低。当转化率小于70％时，共聚物平均组成变化不大；聚合温度增加使聚合速率增加，但共聚物特性粘度减小；SDS浓度对聚合速率和共聚物特性粘度的影响很小；随引发体系浓度增加．聚合速率增加，共聚物特性粘度变化不大。     

聚醋酸乙烯酯乳液的中温合成

采用过硫酸铵/亚硫酸氢钠/甲醛合次硫酸氢钠氧化还原体系在中温条件下引发醋酸乙烯酯乳液聚合,分别讨论了引发剂用量、乳化剂用量、聚合温度等因素对聚醋酸乙烯酯中温合成的影响。乳化剂、引发剂用量分别为单体总量的0.15%和0.6%时,反应温度可降低到45℃,并得到粘度为5.8 Pa.s、固含量为50%的乳白色聚醋酸乙烯酯乳液。     

低温氧化还原引发体系的PU/MMA-BA超浓乳液共聚合

以十二烷基硫酸钠和十六烷醇为复合乳化体系，过硫酸铵／亚硫酸氢钠为氧化还原引发体系，在低温下引发PU／MMA-BA超浓乳液共聚合。研究了复合乳化剂质量浓度、氧化还原引发剂质量浓度、内相比、聚合温度等因素对聚合稳定性和聚合速率的影响，观察了聚合物胶乳粒子的形态，并测试了聚合物胶乳粒子粒径及其分布。结果表明，最佳聚合工艺是PU预聚体中-NCO／-OH(质量比)为1．5～2．0，PU／MMA-BA(质量比)为l／4～l／3，复合乳化剂质量浓度为0．06～0．15g／mL，氧化还原引发剂质量浓度为0．025g／mL，氧化剂／还原剂(摩尔比)为1／0．830～1／0．710，内相比为0．80，聚合温度为20～40℃；聚合反应5h后，单体转化率超过90％，制得了粒径为200nm左右、分散度为0．100～0．400的PU／MMA-RA脑乳粒子。     

自交联型聚醋酸乙烯酯乳液的室温制备

介绍了一种用氧化-还原体系引发醋酸乙烯酯室温聚合的新工艺。试验比较了氧化还原引发体系与热引发体系制备的两种类型乳液的性能,讨论了氧化还原引发剂的用量对聚合物性能的影响,确定了适宜的引发体系用量;并用N-羟甲基丙烯酰胺作为交联单体使聚合物分子通过官能团间反应而固化,形成网络结构,提高了胶粘剂的耐热性,耐水性、粘接性能和使用性能。从而得到生产成本低而性能优良的聚酪酸乙烯酯乳液胶粘剂。     

ACPDA／BPO引发苯乙烯聚合及其动力学

研究了4,4'-偶氮二[4-氰基戊酰(对-二甲基氨基)苯胺](ACPDA)/过氧化二苯甲酰(BPO)氧化还原引发体系在N,N-二甲基甲酰胺(DMF)中引发苯乙烯(St)的聚合及其动力学行为.考察了聚合反应温度、单体浓度、ACPDA浓度和BPO浓度对聚合物分子量和聚合反应速率的影响,测定了反应级数和聚合反应的活化能.实验结果表明:在一定范围内,聚合反应速率随单体浓度、ACPDA浓度、BPO浓度的增加和反应温度的升高而加快;聚合物分子量随单体浓度的增大而增大,随ACPDA浓度、BPO浓度的增大和反应温度的升高而降低.该体系具有氧化还原引发体系的特点,其聚合速率方程为Rp=K[St]1.52[ACPDA]0.56[BPO]0.49,聚合反应的表观活化能Ea =35.43 kJ/mol.     

微悬浮聚合法合成聚醋酸乙烯酯的动力学研究

采用微悬浮法合成聚醋酸乙烯酯,对其聚合反应的动力学进行了研究。考察了引发剂浓度、乳化剂浓度、单体浓度以及温度对聚合反应速率的影响。结果表明,聚合反应速率对引发剂浓度、乳化剂浓度和单体浓度的反应级数分别为0．45,0．28,1．90,单体浓度对聚合反应速率的影响最大,反应体系的表观活化能为105．96 kJ/mol。     

Preparation of copoly(vinyl alcohol–styrenesulfonic acid) resin and its catalytic activity on hydrolysis of carbohydrates. II. Two-step polymerization using tetraethylthiuram disulfide as an initiator

Copoly(vinyl alcohol–styrenesulfonic acid) resin was prepared by a two-step polymerization, consisting of a suspension polymerization of styrene containing divinylbenzene using tetraethylthiuram disulfide as an initiator and a subsequent block copolymerization of vinyl acetate to the crosslinked polystyrene obtained, followed by sulfonation and saponification. Some reaction conditions in the polymerization of styrene were investigated to obtain copolymer containing more vinyl alcohol units. The catalytic activity of the copolymer on the hydrolysis of dextrin was investigated and found to be increased with increasing amount of vinyl alcohol units and with a lowering degree of crosslinking of the copolymer. The maximum acceleration of rate obtained in the presence of the copolymer was about six times that in the presence of Amberlite 120B. Catalytic activity of the copolymer on hydrolysis of sucrose and methyl acetate were also investigated and found to be comparable each other and lower than that for dextrin. The difference between the activities for dextrin and for sucrose and methyl acetate increased with an increasing amount of vinyl alcohol units in the copolymer.     

星型高苯乙烯橡胶聚合及机理探讨

用阴离子聚合的方法合成了星型结构的高苯乙烯橡胶,对高苯乙烯橡胶的聚合反应动力学过程进行了研究,求得不同聚合温度、不同引发剂浓度下假一级表观增长反应速度常数kp"。并根据不同温度下的kp",求取了高苯乙烯橡胶聚合表观增长活化能Ep’=56.7 kJ/mol,高苯乙烯橡胶聚合反应动力学方程表明,聚合反应速率与单体浓度一次方、引发剂浓度1/2次方成正比关系。     

乳液聚合瞬时乳胶粒大小和分布及其控制策略

乳液聚合中瞬时乳胶粒大小及分布与乳胶粒的形成和增长紧密相关,本文在苯乙烯,醋酸乙烯酯乳液聚合中考察了瞬时乳胶粒大小及分布。结果表明,在成核和稳定期乳胶粒增长速率较高,是控制乳胶粒大小及分布的关键阶段,由此提出了对于单体不同水溶性体系控制乳胶粒大小分布的策略,并以实验考核这些策略的合理性。     

On the graft polymerization of styrene and acrylonitrile onto polybutadiene in the presence of vinyl acetate. I. Preparation of graft polymers

In order to modify the graft polymers of styrene and acrylonitrile onto polybutadiene (ABS polymers), the preparation of the graft products of styrene, acrylonitrile, and vinyl acetate onto polybutadiene rubber by emulsion polymerization was described and theoretically studied up to a high degree of conversion. Depending on the residual monomer content of the products, the polymer composition obtained in the experiment was compared with the theoretical one for the substitution of certain quantities of styrene, acrylonitrile, or styrene and acrylonitrile by vinyl acetate in the mass ratio of 3 : 1. Deviations were discussed. The specific viscosity of the polymers of styrene, acrylonitrile, and vinyl acetate separated from the elastomer phase, considerably decreases during the substitution of acrylonitrile by increased vinyl acetate quantities.     

On the graft polymerization of styrene and acrylonitrile onto polybutadiene in the presence of vinyl acetate. II. Properties of graft polymers

The properties of the graft polymers of styrene, acrylonitrile, and vinyl acetate onto polybutadiene rubber that were prepared for the modification of graft polymers of styrene and acrylonitrile onto polybutadiene (ABS polymers) by emulsion polymerization up to a high degree of conversion have been studied and discussed. Both the impact strength and notched impact strength of the graft polymers have been found to remarkably increase with a rising quantity of vinyl acetate, in particular, in the case of styrene substitution, whereas in the case of acrylonitrile substitution by vinyl acetate, the two characteristics become noticeably poorer. The effects of the vinyl acetate amount and the type of substituted monomers on bending strength, tensile strength, Vicat softening point, and glass transition temperature of the graft polymers are also clearly different. Furthermore, the properties of the above graft polymers blended with styrene/acrylonitrile copolymers have been studied.     

丁苯胶乳_苯乙烯_甲基丙烯酸甲酯核壳乳液接枝共聚的研究

以过氧化苯甲酰(BPO)-Fe~(2+)为引发体系,硬脂酸钾和歧化松香酸皂为乳化剂,硫醇为调节剂,于600mL釜内、70℃下进行丁苯胶乳-苯乙烯-甲基丙烯酸甲酯(SBR-S-MMA)的核壳乳液接枝共聚。研究认为本体系的反应机理为:Fe~(2+)与乳化剂结合为部分油溶性化合物,再与溶解在乳胶粒中的BPO反应,生成自由基与Fe~(3+),Fe~(3+)被雕白块还原为Fe~(2+)后完成一个循环。在乳胶粒相产生的自由基与单体反应或进攻橡胶链,从而引起链引发和链增长反应。S和MMA接枝聚合的初始速率(R_(PO))与[BPO]~(0.5)成正比,R_(PO)随反应温度的升高而增大,随硫醇用量的增加而减小。该体系S和MMA两步接枝反应的表观分解活化能分别为16.56kJ/mol和17.50kJ/mol。     

Effect of poly(vinyl acetate/vinyl alcohol) copolymer with a thiol end group as a steric stabilizer on dispersion polymerization of styrene

In dispersion polymerization of styrene in ethanol, effects of a reactive steric stabilizer, poly(vinyl acetate/vinyl alcohol) copolymer with a thiol end group (P(VAc/VA)-SH), were investigated. In the absence of the thiol end group, the dispersion coagulated at the middle stage of the polymerization, while in the presence of the thiol end group, the polymerization proceeded successfully to result in close to monodisperse particles. The reactive thiol group acts as a site of formation of the block copolymer, that is, polystyrene-b-P(VAc/VA), which is utilized as an effective dispersant. From the measurement on molecular weights during the course of polymerization, two polymerization loci were realized. Addition of butyl methacrylate to styrene affected markedly not only rate of polymerization but also particle size. © 1996 John Wiley & Sons, Inc.     

接枝聚合型纸塑复膜胶的研制

介绍了一种利用接枝聚合工艺制备水性复膜胶的方法。以丙烯酸丁酯、醋酸乙烯、苯乙烯为主要原料,首先进行丙烯酸丁酯、醋酸乙烯共聚,并在此基础上接枝聚合丙烯酸丁酯、苯乙烯的共聚物,重点讨论了单体、聚合工艺、乳化剂对水性复膜胶的聚合及性能的影响。     

Preparation of block copolymers with macro-azonitrile as an initiator

Macro-azonitriles were prepared by the reaction of azobis-alcohol with diisocyanate of polyalkylene oxide and were used as initiators for the polymerization of various vinyl monomers such as vinyl acetate, styrene, methyl methacrylate and vinyl chloride, yielding block-copolymers consisting of polyalkylene oxide and polyvinyl sequences. These block copolymers were characterized by their dynamic properties. The polymers were found to possess two transition points, one arising from the polyalkylene oxide blocks and the other from the polyvinyl sequences. A thermoplastic elastomer was obtained from the block polymerization of styrene with poly(oxytetramethylene)glycol, whose intrinsic viscosity was 2.3 dl/g and the styrene content was 33.2 wt. –%, the ultimate strength and elongation being 57 kg/cm² and 475%, respectively. The block copolymers of polystyrene and branched polyether were also synthesized and their viscoelastic properties were investigated.