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.     

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     

用辐射交联方法测定含氟聚合物分子量FEP分子量的测定

本文提出并研究了用辐射交联方法测定难溶高聚物的分子量问题。不同熔融指数FEP共聚物,辐射交联后,其凝胶化剂量随熔融指数增大而增高。由高温弹模测得FEP的交联G值为1.2。由交联G值和凝胶化剂量计算得FEP的,它与熔融指数的关系为log∞3.5log(1/Ml)·该结果与一般高聚物的本体粘度与分子量关系相一致。     

THE EFFECT OF MONOMERS FEEDING METHODS ON EMULSION COPOLYMERIZATION OF VINYLIDENE CHLORIDE AND ACRYLATES

The emulsion copolymerization of vinylidene chloride (VDC) with methyl-methacrylate(MMA) and acrylonitrile (AN) was carried out by batch, seeded batch and semicontinuous pro-cesses,respectively. Significant differences were found in the physical and mechanical propertiesof the latexes and films, depending on the methods of monomer feeding. The results both intheory and experiments demonstrated that the copolymer composition and the length of the VDC sequences in the copolymer could be controlled by the modes of monomer feeding process.     

偏氯乙烯-丙烯腈-苯乙烯共聚物颗粒发泡行为研究

用显微镜实时监测实验方法研究了偏氯乙烯 (VDC) 丙烯腈 (AN) 苯乙烯 (St)共聚物颗粒的发泡行为 ,考察的影响因素包括共聚物组成、发泡剂浓度、颗粒粒径、发泡温度等 .实验发现 ,共聚物中AN或St单元含量提高 ,发泡速率降低 .提高发泡温度或增加发泡剂浓度 ,均加快发泡速率 .由于在聚合物颗粒发泡时存在发泡剂损失 ,小粒径的VDC AN St共聚物颗粒发泡速率快 .当颗粒发泡生长较快时 ,发现有生长过头现象 ,这可能是由惯性生长造成的     

Polymerization and characterization of novel poly(acrylonitrile‐co‐styrene/pyrrole) nanoparticles: A comparison between microwave and conventional method

In this study, poly(acrylonitrile‐co‐styrene/pyrrole) or poly(AN‐co‐ST/Py) copolymer was successfully synthesized using microwave preparation technique, and its comparison with the conventional heating method is investigated. Different polymerization factors affecting on the preparation conditions and conversion yield such as monomer concentration, comonomers ratio, initiator concentration, cosolvent ratio, cosolvent type, polymerization temperature, and polymerization time have a considerable effect on the conversion yield %, functional groups, and molecular weight. The copolymerization process was approved by Fourier transform infrared, thermogravimetric analysis, ¹H NMR spectroscopy, and gel permeation chromatography. The formation of poly(AN‐co‐ST/Py) nanoparticles was confirmed by SEM, and their possible formation mechanisms were also proposed. The SEM images of poly(AN‐co‐ST/Py) prepared by the microwave method showed that the synthesized copolymer had spikes or rods with spherical structure of the produced copolymers than the poly(AN‐co‐ST/Py) nanoparticles prepared by the conventional heating method. Microwave method showed advantages for the produced copolymers compared to that prepared by conventional method, where it can offer a copolymer in short time, high yield, and more thermally stable copolymers, rather than conventional method.     

偏氯乙烯-氯乙烯悬浮共聚物的结晶与熔融性能

研究了聚合温度、共聚物组成、低分子助剂用量等对偏氯乙烯 (VDC) 氯乙烯 (VC)悬浮共聚树脂的结晶度、熔融峰温度的影响 ,并用Florry的聚合物熔点降低理论预测共聚树脂熔点随共聚组成、低分子助剂用量的变化规律 ,为VDC VC悬浮共聚树脂的合成工艺条件和加工性能的改善提供理论基础 .     

Study of the polymer concentration and polymer/crosslinker ratio effect on gelation time of a novel grafted polymer gel for water shutoff using a central composite design method

In this research article, a hydrogel was prepared by crosslinking of carboxymethyl cellulose‐g‐polyacrylamide copolymer aqueous solution with chromium(III) acetate for the purpose of a water shutoff job in the oil reservoir. The experiments were conducted to investigate the main effects of copolymer concentration and crosslinker/copolymer ratio on gelation time of the hydrogel system. Then the effects of these two factors and their interactions on the gelation time were determined by using a central composite design (CCD) of the response surface method. CCD was used to generate the quadratic mathematical model for the gelation time response as a function of copolymer concentration, crosslinker/copolymer ratio, and their interaction. Furthermore, the analysis of variance (ANOVA) was used to evaluate the quality of the quadratic model. The ANOVA result of the developed model showed that the model was highly significant. The result also showed that the crosslinker/polymer ratio had more effects on the gelation time than did the polymer concentration and their interaction. A response surface method provides an optimum gel formulation. Core flooding experiments reveal that a significant permeability reduction on the sand pack cores can be achieved at reservoir conditions, when it is treated with an optimum gel formulation. Hence, this gel system may be suitable in the water shutoff job required for enhanced oil recovery from the oil fields. Copyright © 2015 John Wiley & Sons, Ltd.     

高阻隔材料—偏氯乙烯共聚胶乳

本文对高阻隔材料——偏氯乙烯共聚胶乳的合成、特征及改善胶乳性能的方法进行了详细的介绍。     

无卤阻燃丙烯腈共聚物的制备及性能

以K₂S₂O₈-NaHSO₃ 氧化还原体系为引发剂, 采用水相沉淀自由基聚合法合成丙烯腈(AN)-醋酸乙烯酯(VAc)无规共聚物[P(AN-co-VAc)], 然后在KOH水溶液中进行P(AN-co-VAc)中VAc单元的选择性水解, 再与磷酸和尿素进行磷酰化反应, 制备无卤阻燃丙烯腈共聚物. 用核磁共振氢谱(¹H NMR)、傅里叶变换红外光谱(FTIR)、差示扫描量热(DSC)和热重分析(TGA)对聚合物结构及热性能进行表征, 用凝胶渗透色谱(GPC)测定了P(AN-co-VAc)的分子量及其分布, 并利用FTIR和扫描电子显微镜(SEM)对无卤阻燃丙烯腈共聚物的炭残渣进行分析. 结果表明, VAc与AN发生共聚反应, 制得了P(AN-co-VAc), 随着KOH水溶液pH值的增大, P(AN-co-VAc)中VAc单元迅速水解; DSC分析结果表明, 随着共聚物中VAc单元含量的增大, 共聚物的环化放热分解峰值温度(T_p)增大, 当VAc单元的质量分数为25%时, T_p最大值高达328 ℃, 而阻燃丙烯腈共聚物的T_p高达340 ℃; TGA分析结果表明, 阻燃共聚物在800 ℃时的炭残渣量高达55%以上, 远高于P(AN-co-VAc)的41%, 具有良好的成炭性; 炭残渣的FTIR及SEM结果表明, 阻燃丙烯腈共聚物的阻燃属于凝聚相阻燃.     

Ultrasonic Degradation and Copolymerization of Poly (Vinyl Alcohol) with Acrylonitrile

The ultrasonic degradation of poly(vinyl alcohol) (PVA) in aqueous solution and copolymerization of PVA with acrylonitrile (AN) were studied. It is confirmed that the rate of degradation of PVA follows the kinetic equation suggested by Baramboim. Both water-soluble and water-insoluble copolymer can be obtained by changing the irradiation time or the amount of AN added to the aqueous solution of PVA. The structure of the copolymer was identified by IR, MS, PGC, and x-ray diffraction. The copolymer prepared is mainly a block one. By irradiating 2% PVA/AN (1/1.6, w/w) at 20 ± 1°C and 21. 5 kHz with 490 W for 28 min, the yield of water-soluble copolymer is 25.49%, the AN content in which is 13.98%. After 100 min, with the weight ratio between PVA and AN 1/4, the yield of the water-insoluble copolymer amounted to 296.01%, the AN content in which is 75.56%.     

Core–shell morphology as a model for the study of gas permeation in composite systems

Structured latex particles prepared by emulsion polymerization were used as a model to simulate the interphase region between two phases. Multiphase polymer films comprised of high and low permeability polymers of various compositions were used. The model system consisted of a poly(n-butyl methacrylate) (PBMA) matrix and a discontinuous phase with core and shell morphology. The structured particle had a PBMA core and a vinylidene chloride – n-butyl methacrylate (VDC–BMA) copolymer shell. The shell transport characteristics wer altered by changing the (VDC–BMA) copolymer molar ratio. The physical and transport properties for each individual component were measured. Nitrogen was the probe gas. Films used for permeation experiments were prepared by latex casting. The results showed that the morphology of a heterogeneous polymeric system and the transport characteristics of their components had a considerable effect on the magnitude of the transport properties. Experimental data also showed the dependence of the gas global permeability coefficient on the nature of the simulated interphase region, the shell, and the weight percentage of such interphase in the heterogeneous polymeric films. Upon increasing the VDC content in the VDC–BMA copolymer, the gas permeability decreased. The data were fitted to the electrical analogs of conductivity in composite systems. For the matrix filled with structured particles the overall permeability coefficient could best be described when the individual permeabilities were considered as the inverse resistances in parallel.     

Ion gels by self-assembly of a triblock copolymer in an ionic liquid

We report a new way of developing ion gels through the self-assembly of a triblock copolymer in a room-temperature ionic liquid. Transparent ion gels were achieved by gelation of a poly(styrene-block-ethylene oxide-block-styrene) (SOS) triblock copolymer in 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) with as low as 5 wt % SOS triblock copolymer. The gelation behavior, ionic conductivity, rheological properties, and microstructure of the ion gels were investigated. The ionic conductivity of the ion gels is only modestly affected by the triblock copolymer network. Its temperature dependence nearly tracks that of the bulk ionic liquid viscosity. The ion gels are thermally stable up to at least 100 degrees C and possess significant mechanical strength. The results presented here suggest that triblock copolymer gelation is a promising way to develop highly conductive ion gels and provides many advantages in terms of variety and processing.     

Composition of vinylidene chloride/phenylacetylene (VDC/PA) copolymers and vinylidene chloride/methyl acrylate/phenylacetylene (VDC/MA/PA) terpolymers from analysis by 13C-NMR spectroscopy

¹³C-NMR spectroscopy has been utilized to characterize Saran polymers containing polyene segments generated by incorporating phenylacetylene (PA) units into either poly(vinylidene chloride) (PVDC) or a typical Saran copolymer of 91% vinylidene chloride (VDC) and 9% methyl acrylate (MA). The incorporation of PA could not be defined in the usual statistical way because the presence of the PA double bond in the polymer backbone appeared to cause the dehydrohalogenation of units next to it. Thus, sequences of PA next to VDC were not observed. Rather, sequences of olefinic units next to VDC units were present at a level equal to the level of PA incorporation. The level of unsaturation in the PA copolymers is approximately four times the level of PA incorporation. These observations are consistent with the random incorporation into the copolymer of PA which then initiates the dehydrohalogenation in adjacent VDC units. This dehydrohalogenation reaction appears to propagate from one unit to the next along the backbone of the polymer such that polyene segments containing the PA unit are formed.     

BARRIER PROPERTIES OF VINYLIDENE CHLORIDE COPOLYMERS

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.     

Transition from miscibility to immiscibility in blends of poly(methyl methacrylate) and styrene-acrylonitrile copolymers with varying copolymer composition: a DSC study

The glass transition and the structural relaxation processes have been studied in blends of poly(methyl methacrylate) (PMMA) and styrene-acrylonitrile (SAN) copolymers with different acrylonitrile (AN) contents. The 50/50 wt.% blend of PMMA with the SAN copolymer containing 30 wt.% of AN is immiscible, while blends with copolymers containing between 13 and 26 wt.% of AN are miscible. Thus the upper limit of miscibility is between 26 and 30 wt.% of AN. The temperature dependence of the relaxation times of the conformational rearrangements of polymer chains around the glass transition have been determined in the blends and pure components by modelling DSC thermograms obtained after different thermal histories in each sample. The slope in the Arrhenius diagram logτ vs 1/T around the glass transition temperature is significantly smaller in the blend which is closer to the upper limit of miscibility than in the other miscible blends in which SAN copolymer contains less AN. The change of slope can be ascribed to a distribution in the glass transition temperatures of the different rearranging regions, reflecting the appearance of a microheterogeneity in the blend that cannot be detected as a double glass transition in the blend.     

Synthesis and electrical response of acrylic acid/vinyl sulfonic acid hydrogels prepared by γ-irradiation

The electro-active acrylic acid/vinyl sulfonic acid copolymer (AAc/VS) was prepared using γ-radiation. The effect of preparation conditions such as comonomer composition and irradiation dose on copolymer gelation degree, and swelling property of the prepared copolymer in water and different electrolytes of various concentrations was studied. The degree of gelation decreases by increasing the VS content in the feed solution and increases by increasing the irradiation dose. The swelling degree decreases by increasing the irradiation dose and ionic strength. The electro-activity of the prepared AAc/VS copolymer was investigated to find out that it greatly affected by polymer composition and crosslinking density as well as the hydrogel counter ion. The electrical sensitivity increases by the increase of VS content and crosslinking density in the copolymer. AAc/VS copolymers showed various degrees of bending behavior depending on the counter ion. The presence of potassium as counter ion maximized the electrical response of the polymer.     

Preparation and characterization of novel thermal-stable vinylidene chloride–methyl acrylate–glycidyl methacrylate copolymer

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.     

Preparation and characterization of vinylidene chloride‐co‐vinyl chloride copolymer/fluorinated synthetic mica nanocomposites I thermal and mechanical properties studies

Poly(vinylidene chloride‐co‐vinylchloride)/organically modified fluorinated synthetic mica (MEE) (VDC‐VC/MEE) nanocomposites were prepared by melt blending of VDC‐VC copolymer with MEE, in the presence of dioctyl phthalate (DOP) which acted as a plasticizer and a cointercalating agent. The nanostructure, thermal, and dynamic mechanical properties of the VDC‐VC/MEE nanocomposites were studied by wide angle X‐ray diffractometer (WAXD), scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analyzer (TGA), and dynamic mechanical analyzer (DMA). It was found that partially intercalated and partially exfoliated structures coexisted in VDC‐VC/MEE nanocomposities. Below 8 wt % MEE content, the intercalation effect of nanocomposites decreased with increasing the MEE content. Under a nitrogen atmosphere, VDC‐VC/MEE nanocomposites exhibited a single step thermal degradation behavior. The nanostructure of VDC‐VC/MEE can effectively prevent volatile gases from being released, and thus enhances its thermal stability. The thermal stability of VDC‐VC/MEE nanocomposites is strongly related to the morphology of nanocomposites and the degraded composites structure. DMA revealed a significant improvement in the storage modulus within the testing temperature range. The increase in storage modulus depends on the MEE content, which is attributed to the dispersed phase morphology. The glass transition temperature of VDC‐VC/MEE nanocomposites is affected by the chain mobility in the nanocomposites rather than the aggregative morphology. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1214–1225, 2008     

Sorption kinetics of 1-fluoro-1,1-dichloroethane in vinylidene chloride-acrylonitrile-styrene terpolymer

The sorption kinetics of liquid 1-fluoro-1,1-dichloroethane (HCFC-141b) and its vapor in vinylidene chloride (VDC)-acrylonitrile (AN)-styrene (St) terpolymers were investigated by weight gain method. It was found that the sequence of the effect of monomer unit on the barrier property for HCFC-141b is AN>VDC>St at the same molar content. The diffusion mechanism of HCFC-141b in VDC-AN-St terpolymer depends on the glass transition temperature (T_g) of VDC terpolymers, sorption temperature, vapor pressure and so on. For Fickian diffusion, the diffusivity (D) is exponential function of vapor pressure at the same temperature. A quantitative relationship between D in terms of HCFC-141b in VDC-AN-St terpolymer with composition VDC/AN/St=55.7/12.9/31.4 (wt), temperature and activity was obtained, and the activation energy of diffusion is 37.68 KJ/mol.