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Hideki Sakai Takahiko Kodani Atsuko Takayama Mamoru Nomura 《Journal of Polymer Science.Polymer Physics》2002,40(10):939-947
Changes in minimum film‐formation temperature (MFFT) during storage of latexes prepared from 91:9 wt % vinylidene chloride (VDC)‐methyl methacrylate (MMA) monomer mixture by seeded batch and seeded semicontinuous emulsion polymerization were investigated, with attention centered on polymer‐crystallization behavior during storage in the dispersed state. MFFT of latex prepared by the seeded batch process rose to 47 °C, whereas that of latex prepared by seeded semicontinuous process remained below 14 °C with storage at 20 °C for 12 weeks. Infrared absorption of latexes in the dispersed state and wide‐angle X‐ray diffraction of powder polymers obtained by lyophilization of fresh and stored latexes both indicated a much greater increase in polymer crystallinity during storage with latex prepared by the seeded batch process than with that prepared by the seeded semicontinuous process. Analysis of the copolymer composition drift calculated from reactivity ratios and 1H NMR analysis indicated a wider sequence distribution and longer VDC sequences in polymer prepared by the seeded batch process than in polymer prepared by the seeded semicontinuous process. This explained the higher rate of crystallization during storage with latex prepared by the seeded batch process than with that prepared by the seeded semicontinuous process. Rising crystallinity during storage in the dispersed state is believed to have caused the MFFT rise. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 939–947, 2002 相似文献
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The permeability coefficients of a series of copolymers of vinylidene chloride (VDC)with methyl acrylate (MA), butyl acrylate (BA) or vinyl chloride (VC) (as comonomer)to oxygen and carbon dioxide have been measured at 1.0 MPa and 30℃, while those towater vapor have been measured at 30℃ and 100% relative humidity All the copolymersare semicrystalline. VDC/MA copolymers have lower melting temperature compared withVDC/BA copolymers, while that melting temperature of VDC/VC copolymer is higherthan that of VDC/acrylate copolymers with the same VDC content. The barrier propertyof the copolymers is predominantly controlled by crystallite, free volume fraction, andcohesive energy The permeability coefficients of VDC/MA copolymers to oxygen, carbondioxide, and water vapor were successfully correlated with the ratio of free volume tocohesive energy. 相似文献
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M. Nomura H. Sakai Y. Kihara K. Fujita 《Journal of polymer science. Part A, Polymer chemistry》2002,40(9):1275-1284
The effects of operating variables on the kinetic behavior of the emulsion copolymerization of vinylidene chloride (VDC) and methyl methacrylate (MMA) were examined at 50 °C with sodium lauryl sulfate as an emulsifier and potassium persulfate as an initiator, respectively. The number of polymer particles produced increased in proportion to the 1.0 power of the initial emulsifier concentration and to the 0.3 power of the initial initiator concentration and decreased with an increasing content of MMA in the initial monomer charge. The rate of copolymerization was proportional to the 0.4 power of the initial emulsifier concentration and to the 0.5 power of the initial initiator concentration and increased with an increasing content of MMA in the initial monomer charge. The molecular weight of copolymer produced decreased drastically with an increasing content of VDC in the initial monomer charge. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1275–1284, 2002 相似文献
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Hideki Sakai Takahiko Kodani Atsuko Takayama Mamoru Nomura 《Journal of Polymer Science.Polymer Physics》2002,40(10):948-953
Changes in the minimum film‐formation temperature (MFFT) of 91:9 wt % vinylidene chloride (VDC)‐methyl methacrylate (MMA) latex prepared by the seeded batch process during storage at 5, 20, and 40 °C were investigated. MFFT of the latex rose the fastest at 20 °C. Infrared absorption of fresh and stored latexes and wide‐angle X‐ray diffraction of powder polymers obtained by lyophilization of fresh and stored latexes indicated a much greater increase in polymer crystallinity during latex storage at 20 °C than at 5 and 40 °C. Observed increases in MFFT during latex storage correlated with increases in polymer crystallinity. Infrared absorption of polymer stored at 5–60 °C in the dry state, such as lyophilized polymer and coating film, indicated that a polymer crystallinity increase was greater during storage at higher temperatures. These results showed that crystallization behavior of 91:9 wt% VDC‐MMA copolymer latex differed from that of VDC‐MMA copolymer in the dry state. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 948–953, 2002 相似文献
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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. 相似文献
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Rui Wang Yingwu Luo Bogeng Li Xiaoying Sun Shiping Zhu 《Macromolecular theory and simulations》2006,15(4):356-368
Summary: Although controlled/living radical copolymerization has been extensively studied, the control of copolymer composition distribution receives little attention. In this paper, taking RAFT copolymerization as an example, we develop a mathematical model and simulate copolymerization systems with various reactivity ratios. It is demonstrated that through semi‐batch operations with programmed profiles of slow monomer feeding rate, precise control over copolymer composition distribution (uniform and designed gradient distributions) along polymer chain can be achieved. It is also found that the semi‐batch operations have lower rates of polymerization than their batch counterparts. The reason for this difference is analyzed, and the magnitude depends on the reactivity ratios and targeted copolymer composition. The improvement of the semi‐batch rate by distributing a part of the initiator amount to the monomer feeding tank is found to be minor.
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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 相似文献
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Antonio C.S.M. Carvalho Dennis Chicoma Claudia Sayer Reinaldo Giudici 《Macromolecular Symposia》2006,243(1):147-158
In this work, vinyl acetate/butyl acrylate emulsion copolymerizations carried out in a continuous tubular reactor (pulsed sieve plate column, PSPC) were compared to those conducted in a semibatch stirred tank reactor under similar operational conditions. In order to minimize the compositional drift along the PSPC, reactions were carried out with different numbers (2, 3 and 4) of lateral feed streams of the more reactive monomer (butyl acrylate). For comparison, fed batch reactions were conducted with the same number of intermittent shot additions of butyl acrylate, at the corresponding batch times. Both systems (tubular and semibatch) with distributed feeding of more reactive monomer are able to reduce composition drift thus providing more uniformity in copolymer composition. In addition, the tubular reactor presents much better control of temperature than the tank reactor, which is important to achieve higher productivity. 相似文献
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Synthesis of large-sized monodisperse polystyrene microspheres by dispersion polymerization with dropwise monomer feeding procedure 总被引:1,自引:0,他引:1
Hongfei Qi Weichang Hao Huaizhe Xu Junying Zhang Tianmin Wang 《Colloid and polymer science》2009,287(2):243-248
Highly monodisperse polystyrene (PS) microspheres in the size range of 3.75–7.09 μm were synthesized by dispersion polymerization
with dropwise monomer feeding procedure. The morphology, size, and particle size distribution (PSD) of the PS microspheres
obtained by different monomer feeding modes, including batch polymerization and various feeding rates, were investigated.
The PSD of particles showed a close dependence on feeding rate. The PS microspheres with low coefficient of variation (CV)
values all less than 4.8% obtained by the optimum feeding rates revealed better uniformity than those by batch polymerization
(CV values all more than 8.2%). According to the time courses of monomer conversion and particle numbers, the effects of monomer
feeding modes on the polymerization reaction of the large-sized PS microspheres were clarified. It is found that the dropwise
monomer feeding procedure is promising for the synthesis of large-sized monodisperse PS particles in 3.75–7.09 μm. 相似文献
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含氨基、羟基丙烯酸乳液聚合的稳定性 总被引:12,自引:1,他引:11
采用间歇及半连续乳液聚合方式,以过硫酸铵/亚硫酸钠为引发体系,合成了甲基丙烯酸甲酯/丙烯酸丁酯/甲基丙烯酸羟乙酯/甲基丙烯酸二氨基乙酯四元共聚物胶乳.系统研究了乳化剂种类和浓度、聚合温度、乳化单体进料方式及进料速率对聚合过程稳定性的影响.聚合温度降低,乳化单体进料速度减慢有利于聚合过程的稳定,采用种子半连续聚合方式比间歇聚合过程更稳定,乳化剂浓度的增加有利于聚合稳定性的提高和乳胶粒子的均匀化. 相似文献
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《International Journal of Radiation Applications and Instrumentation. Part C. Radiation Physics and Chemistry》1988,31(5):657-660
The gelation dose of a vinylidene chloride (VDC)/acrylonitrile (AN) random copolymer irradiated with γ-rays in vacuum is first determined by conventional techniques, such as viscometry and solubility. The onset of gelation was determined to be 5.8 Mrad for this copolymer of composition 20% AN/80% VDC. The same gelation dose is also determined by a spectrophotometric method which is based on the recording of u.v.-vis spectra of solutions of this copolymer in THF. The advantages of this new technique for determination of gelation dose over the conventional methods are discussed. 相似文献
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Fei Zhao Ye Yin Dongqiao Zhang Ping Ning Manhua Fu Daai Yao 《International Journal of Polymer Analysis and Characterization》2017,22(4):338-347
A novel copolymer was synthesized by vinylidene chloride (VDC)/methyl acrylate (MA)/glycidyl methacrylate (GMA). The Fourier transform infrared (FTIR) and 1H-nuclear magnetic resonance analyses indicated that the copolymer of VDC/MA/GMA (PVMG) was synthesized successfully. The influences of GMA on the molecular weight, melting point, and thermal stability of copolymer were investigated by gel permeation chromatograph, differential scanning calorimeter, thermogravimetric analysis–FTIR, respectively. The copolymerization eliminated the phenomenon of “double melting peaks” for poly(vinylidene chloride), and the melting point was reduced to 165°C. The GMA also enhanced the thermal stability of copolymer, which was proved by the increased decomposition temperature of copolymer. The existence of GMA caused the cross-linking of the copolymer, which contributed to the improvement of barrier performance of PVMG. 相似文献
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M. G. Pérez‐García E. V. Torres I. Ceja L. A. Pérez‐Carrillo Raúl G. López F. López‐Serrano E. Mendizábal J. E. Puig 《Journal of polymer science. Part A, Polymer chemistry》2012,50(16):3332-3339
The synthesis of styrene‐acrylonitrile copolymers by semicontinuous heterophase polymerization is reported here. The effect of feed composition at a fixed addition rate of monomer mixture on kinetics, particle size, polymer content, and molar masses, was studied. This process permits the synthesis of nanolatexes containing narrow size‐distribution particles with number‐average diameter (Dn) of about 18 nm, polymer content as high as 23 wt %, and copolymer‐to‐surfactant weight ratios between 23 and 25, depending on monomer feeding rate, which are larger than those reported for microemulsion copolymerization of several comonomers. Copolymers with homogeneous composition similar to the feeding monomers composition were obtained thorough the reaction, which is difficult to achieve by batch polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
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F. Joseph Schork 《大分子反应工程》2020,14(3)
The equations for predicting molecular weight distribution, copolymer composition distribution, and copolymer sequence distribution for three polymerization mechanisms (monomer linkage with termination, monomer linkage without termination, and polymer linkage), and three reactor types (batch/plug flow, homogenous continuous stirred tank, and segregated continuous stirred tank) are assembled from various sources and compared and contrasted. 相似文献