偏氯乙烯-丙烯腈悬浮共聚物的组成研究

研究了偏氯乙烯 丙烯腈 (VDC AN)悬浮共聚体系中AN的水溶性对单体相组成和树脂组成的影响 .结果表明 :由于AN部分地溶于水 ,使有机相AN的含量降低 ,导致共聚树脂的组成明显地不同于本体聚合模型的计算预测值 .为了准确地计算预测VDC AN共聚树脂的组成 ,本文假设溶于水的AN向有机相迁移的速度比聚合反应速度快得多 ,AN在两相的溶解分配近似为平衡态 .计算中先用描述AN在VDC/水系统中溶解分配的Marker式校正有机相AN的含量 ,然后根据校正后的AN含量用Mayo Lewis式计算预测VDC AN悬浮共聚物的组成 ,计算中有关的竞聚率值取自于文献中本体聚合的值 .计算结果与实验值一致     

St/AN乳液共聚合的表观竞聚率和恒比组成

<正> 共聚合中竞聚率的正确测算对于研究共聚物组成与单体配料比及转化率的关系、共聚物组成分布及链段分布和共聚合机理都有重要意义。对于大多数二元自由基共聚体系,聚合方法不同对竞聚率无影响,但对某些聚合体系,如苯乙烯/丙烯腈,不同的聚合方法测得的“竞聚率”会有所不同。一般文献报道,苯乙烯/丙烯腈自由基共聚合,60℃下的竞聚率分别为r_st=0.41±0.08,r_(AN)=0.04±0.04,均系本体聚合的实验结果。为此,     

(2-甲基丙烯酰氧乙基)三甲基氯化铵-丙烯酰胺双水相共聚合

将(2-甲基丙烯酰氧乙基)三甲基氯化铵(DMMC)与丙烯酰胺(AM)在聚乙二醇(PEG)水溶液中进行双水相共聚合(ATPC),并与DMMC/AM均相水溶液共聚合(HASC)进行比较.在均相水溶液共聚合体系中得到了DMMC/AM共聚体系的竞聚率分别为rDMMC=1.77、rAM=0.32,并给出了竞聚率的95%,99%联合置信区域.比较了两种共聚合体系的转化率-时间曲线和共聚组成,表明双水相共聚合体系初期反应速率高于均相水溶液共聚合体系,但最终转化率相似;两种共聚合体系得到的共聚物组成有较大差别.测得了DMMC、AM以及DMMC-AM共聚物(CPAM)在65℃、反应条件下的相分配系数为K1=0.035、K2=0.125和Kp=0.011.结合双水相聚合的本质以及单体和共聚物在两相的分配系数,提出了一个计算双水相共聚组成的新方法,用该方法计算的双水相共聚合体系的共聚组成与实验点吻合较好.     

在α-甲基苯乙烯二聚体调节作用下的苯乙烯-丙烯腈乳液共聚

<正> 由于苯乙烯(St)和丙烯腈(AN)竞聚率的差异,在乳液共聚中所得产物为组成不均匀的共聚物,因此一般在反应后期通过复杂计算和实验验证补加消耗快的单体,或采用回收大量单体等方法得到组成均匀的共聚物。St-AN乳液共聚物的分子量较大,产物不     

化学交联聚氯乙烯树脂的合成和结构

研究了氯乙烯/交联单体悬浮共聚时,交联单体种类、浓度和聚合温度对化学交联聚氯乙烯树脂结构的影响.对于氯乙烯/邻苯二甲酸二烯丙基酯(VC/DAP)悬浮共聚体系,凝胶含量和凝胶交联密度随DAP起始浓度的增加而增大;DAP浓度相同时,凝胶含量和凝胶交联密度随聚合温度上升而下降;当凝胶含量较高时,分子链物理缠结对凝胶交联密度有较大贡献,凝胶交联密度随凝胶含量增加而快速上升.在相同交联单体浓度下,氯乙烯/马来酸二烯丙基酯(VC/DAM)共聚物的凝胶含量最大,VC/DAP共聚物次之,氯乙烯/乙二醇二甲基丙烯酸酯(VC/EGDMA)共聚物最小,这是由于DAM单体的竞聚率小于1,且含有马来酸双键,EGDMA单体的竞聚率远大于1.     

乙烯基单体/N-苯基马来酰亚胺共聚物组成预测、控制和优化

采用递推方法成功地预测了乙烯基单体/N-苯基马来酰亚胺(PMI)共聚物组成随转化率的变化.选择共聚单体种类和用量,控制和优化共聚物组成.针对氯乙烯(VC)/PMI/丙烯腈(AN)三元悬浮共聚合特殊体系的聚合特点和工艺,得到该三元体系的单体选择范围.     

氯乙烯/N-苯基马来酰亚胺共聚物组成控制和优化

研究了氯乙烯 /N 苯基马来酰亚胺 (VC/PMI)共聚物组成随转化率的变化 ,体系中共聚物的累积组成偏差小于 0 0 5或 0 1的单体配比范围很小 ,采用加入第三单体丙烯腈 (AN)的方法进行改善 ,并以PMI在共聚物中的累积组成偏差作为控制参数 ,得到了PMI在共聚物中的累积组成偏差小于 0 0 5和 0 1的VC/PMIlAN较优的配比范围 .结合悬浮聚合工艺的特点 ,确定了VC/PMI/AN悬浮共聚的最佳单体配比范围为f1=0 72～ 0 84 ,f2 =0 0 2～ 0 0 4 ,f3 =0 1 2～ 0 2 4 .     

氢氧根对苯乙烯和甲基丙烯酸甲酯ATRP悬浮共聚的影响

在85℃下,以α-溴异丁酰溴为引发剂、氯化亚铜为催化剂、2,2′-联吡啶(bpy)为配体,研究了氢氧化钠(NaOH)含量对苯乙烯和甲基丙烯酸甲酯的原子转移自由基悬浮共聚合的影响。1H-NMR分析和共聚竞聚率(rSt=0.83,rMMA=0.82)表明St/MMA原子转移悬浮共聚容易形成恒比共聚。ATRP的悬浮聚合表现出较好的可控/活性特征。在试验水相中氢氧根浓度为0至3%的范围内,单体转化率、ln[M]0/[M]和表观反应速率常数kappp都随着氢氧根浓度增大而增大。氢氧根并不影响聚合反应的一级动力学特征,但具有加速St/MMA原子转移悬浮共聚反应的作用。探讨了氢氧根在St/MMA原子转移悬浮共聚反应中的作用机理。     

丙烯腈──苯乙烯/聚丙烯接枝共聚合

丙烯腈（AN）—苯乙烯（St）与聚丙烯（PP）非均相接枝共聚，得杨梅形树脂。研究了AN／St摩尔比对接枝聚合的影响，发现苯乙烯相对含量增大时，非接枝物产量增加，接枝率和接枝效率相应下降。从接枝物的C、H、N分析可计算出聚丙烯、丙烯腈和苯乙烯的组成比例。此外，用二乙烯基苯（DVB）作交联剂，制备了PP－g－（AN－co－St－co－DVB）接枝共聚物—交联型薄壳树脂，交联剂的存在使单体转化率和接枝效率高达100％。     

SAN共聚物组成对PVC/ABS共混物相容性的影响

采用乳液聚合技术通过改变共聚单体的投料比(St/AN)合成了一系列不同AN结合量的ABS接枝共聚物粉料和SAN共聚物.将其与聚氯乙烯(PVC)和邻苯二甲酸二辛酯(DOP)熔融共混分别制得了PVC/ABS、PVC/SAN、PVC/ABS/DOP和PVC/SAN/DOP共混物,利用SEM、TEM和动态力学粘弹谱仪(DMA)对共混物的相容性和相结构进行了表征.结果发现,在PVC/ABS共混体系中,尽管改变接枝SAN共聚物的AN结合量,PVC和SAN共聚物均为不相容体系;在该共混物中引入增塑剂DOP后,虽然当SAN共聚物AN结合量小于23.4 wt%时,共混物在室温以上只存在一个tanδ峰,但形态结构研究结果表明共混物仍为不相容体系,共混物的相区尺寸明显地依赖于SAN共聚物中的AN结合量,当AN结合量为23.4 wt%时相区尺寸最小.     

Effects of acrylonitrile water solubility on limiting conversion and copolymer composition in suspension polymerization

The effects of acrylonitrile (AN) water solubility on the limiting conversion and copolymer composition of the AN and AN/vinylidene chloride (VDC) suspension polymerization were investigated. It was found that AN dissolved in aqueous phase does not transfer back to oil phase in AN suspension homopolymerization but partially does in AN/VDC suspension copolymerization, and thus the limiting conversion is lowered and decreases with water/oil ratio increasing in both AN and AN/VDC suspension polymerization. For the continuous transport of AN in aqueous phase to oil phase during suspension polymerization, the composition distribution of AN/VDC copolymer prepared by suspension polymerization is narrower than that by bulk polymerization. The calculated composition of AN/VDC suspension copolymer with considering AN water solubility is consistent with the experimental data.     

甲基丙烯酸甲酯水溶性对其悬浮均聚动力学的影响

通过比较在大水油比下的甲基丙烯酸甲酯 (MMA)悬浮均聚的实验数据以及本体聚合实验结果 ,发现单体的水溶性对其聚合动力学有影响 ,不能用本体聚合动力学代替其悬浮聚合动力学 .为了能更好了解单体的水溶性对其悬浮聚合动力学的影响以及影响动力学的原因 ,在MMA本体聚合动力学模型基础上 ,进一步提出 3个假设 :扣除溶于水相部分的单体量、增长和终止速率参数降低、少部分的油溶性引发剂被带到水相中 ,得到改进的悬浮聚合动力学模型 .运用该模型能很好预测水油比、聚合温度、引发剂浓度等对MMA悬浮聚合动力学的影响 ,且与实验数据能较好吻合     

Core-shell emulsion copolymerization of styrene and acrylonitrile on polystyrene seed particles

Seeded emulsion copolymerization of an azeotropic composition of styrene (St) and an acrylinitrile (AN) comonomer mixture in polystyrene (PS) seed at different polymerization temperature of 55–75°C were investigated. The kinetic data showed a transition temperature at 65°C, above which the activation energy of polymerization is low, 6.1 Kcal/mol, compared with 9.8 Kcal/mol below it. The particle-size results and thin layer chromatographic (TLC) data showed two types of particle of different composition and morphology in the final latex system: a smaller size of (St–AN) copolymer and a larger size of core-PS and (St–AN) copolymer shell, with a zone of PS grafted (St–AN) copolymer in between. Various polymerization parameters, that is emulsifier concentration, type of seed particle and its size, and monomer/polymer ratio, were studied and their effects on particle size and particle morphology were examined. The percent of grafted core-PS was 10% below a polymerization temperature of 65°C and 40% above that temperature. By adjusting the size and number of the seed particles, monomer-polymer ratio, and emulsifier concentration conditions were established in which a final copolymer latex with “perfect” core-shell morphology was achieved.     

Effect of reaction medium on copolymerization of acrylonitrile and methyl acrylate

The copolymerization of acrylonitrile (AN) with methyl acrylate (MEA) has been investigated in three types of polymerization, i.e., emulsion polymerization in water with a water-soluble initiator, suspension polymerization in water with an oil-soluble and water-insoluble initiator, and solution polymerization in dimethyl sulfoxide (DMSO). Monomer reactivity ratios at 50°C. for AN and MEA are found to be r₁ = 0.78 ± 0.02, r₂ = 1.04 ± 0.02 in emulsion polymerization; r₁ = 1.02 ± 0.02, r₂ = 0.70 ± 0.02 in DMSO solution polymerization; r₁ = 0.75 ± 0.05, r₂ = 1.54 ± 0.05 in suspension polymerization. The large differences found in the reactivity ratios may be attributed to the different ratio of concentration of two monomers in the loci of polymerization. Chemically, AN is somewhat more reactive than MEA as shown by the reactivity ratios in DMSO. In the case of the suspension polymerization, the MEA/AN ratio in the polymer particles in which polymerization occurs may be higher than that in the total phase. Experimental results of the emulsion polymerization show that the emulsion polymerization of AN occurs both in the particles and in water. In addition, rates of the copolymerization of AN with MEA have also been investigated.     

Copolymerization kinetics of methyl methacrylate-styrene obtained by PLP-MALDI-ToF-MS

The combination of MALDI-ToF-MS and pulsed laser polymerization has been used to study the propagation rate coefficients for the copolymer system styrene-methyl methacrylate. For the first time, complete information regarding mode of termination, reactivity of photoinitiator-derived radicals, copolymer molecular mass, chemical composition, and copolymerization rates is obtained interrelated. The polymerizations were carried out in bulk with varying styrene concentrations at a temperature of 15.2 degrees C by an excimer pulsed laser with varying frequencies. Both chemical composition distributions and molecular weight distributions were determined by MALDI-ToF-MS. The data were fitted to the implicit penultimate unit model and have resulted in new point estimates of the monomer and radical reactivity ratios for the copolymer system styrene-methyl methacrylate: r(St) = 0.517, r(MMA) = 0.420, s(St) = 0.296, s(MMA) = 0.262. Comparison between Monte Carlo simulations and the obtained results further confirmed the very successful combination of pulsed laser copolymerization experiments with MALDI-ToF-MS. The obtained results are believed to be the most accurate and complete set of copolymerization parameters to date.     

Estimating Reactivity Ratios From Triad Fraction Data

Reactivity ratio estimation is a non-linear estimation problem. Typically, reactivity ratios are estimated using the instantaneous copolymer composition equation, otherwise known as the Mayo-Lewis model, based on low conversion (<5%) copolymer composition data. However, there are other instantaneous models, which can be used to estimate reactivity ratios, such as the instantaneous triad fraction equations. The aim of this paper is to determine the potential improvement in reactivity ratio estimates when triad fraction data is used in place of and in combination with copolymer composition data. The interest in using triad fraction data in parameter estimation, stems from the fact that there are a greater number of responses measured (six triad fractions) compared to composition leading to data with theoretically more information content. In principle this should lead to reactivity ratio estimates having less uncertainty. In this study, the parameter estimates are obtained by employing the error in variables model (EVM), assuming a multiplicative error structure. Several case studies involving published literature data for different copolymer systems are presented. As the case studies demonstrate in general more precise estimates can be obtained from triad fraction data. Combining the triad fraction with composition data leads to little additional improvement. However, discrepancies arise between reactivity ratios estimated from composition data compared with those obtained from triad fraction data depending upon the copolymer system. Those copolymer systems exhibiting more heterogeneity due to phase separation during polymerization may be showing more discrepancy.