聚甲基丙烯酸甲酯/聚(苯乙烯-丙烯腈)共混体系相分离的特征动态流变响应

采用动态流变学方法,结合小角激光光散射(SALLS)测定,对聚甲基丙烯酸甲酯(PMMA)/聚(苯乙烯－丙烯腈)(SAN)共混体系的动态流变行为与相分离的关系进行了研究.发现在低频区域,时温叠加失效与共混物体系发生相分离有关,时温叠加失效温度T_b与用SALLS测定的浊点温度T_c一致,用低频区域动态储能模量G'与频率的关系[1gG'～lg(α_T)]偏离线性粘弹模型或时温叠加失效温度表征PMMA/SAN共混体系的相分离是有效的.     

Re‐Gradation of Photo‐Oxidized Post‐Consumer Greenhouse Films

Summary: The degradation undergone by the polymers during their use and because of the thermo‐mechanical degradation undergone during the reprocessing operations provokes, among other effects, the decrease of the molecular weight. The change of the molecular architecture is responsible for the deterioration of all the properties. In order to restore the properties of post‐consumer recycled plastics, some rebuilding of the molecular structure is necessary. In this work, photo‐oxidized films for greenhouses were reprocessed in presence of additives able to react with the polyethylene in order to form branching and cross‐linking, improving the properties of these post‐consumer plastic.

Pressure as a function of time in the mini twin‐screw extruder, processing speed 70 rpm.     

高压处理后大豆分离蛋白溶解性和流变特性的变化及其机理

 对高压处理后大豆分离蛋白溶解性和流变特性的变化及其机理进行了研究。经400 MPa、15 min高压处理使低浓度大豆分离蛋白溶液中蛋白质溶解性的提高最为显著。高压处理使大豆分离蛋白溶液的表观粘度增加,其贮藏模量G'和损耗模量G'也随着处理压力的提高而增大。扫描电镜观察和凝胶电泳的结果都显示,在低于400 MPa高压处理后大豆分离蛋白分子发生一定程度的解聚和伸展,蛋白质颗粒减小,溶液中蛋白质的体积分数增加。而红外光谱分析表明,高压处理后蛋白质电荷分布加强。高压处理后大豆分离蛋白分子结构上的改变是导致其有关理化性质变化的原因。     

Weak flocculation of aqueous kaolin suspensions initiating by NaCMC with different molecular weights

The present work is an investigation of the effect of NaCMC with different viscosities (molecular weights) on the stability of aqueous kaolin suspensions at pH 5-6. The stabilizing effect of polymers was characterized by measuring the sedimentation volumes (for 2.5% kaolin suspensions) and some important rheological parameters (for 40% and 50% kaolin suspensions). In certain cases the stability of suspensions was also studied in the presence of 0.5-1.0% NaCl. The additives were incorporated into the suspensions separately and simultaneously, as well. In certain cases the effect of mixing order of NaCMCs was also studied. The lower viscosity NaCMC was found to be a better stabilizing agent than its medium viscosity counterpart at the studied polymer concentrations (0.005-1.0%). This was manifested in smaller sedimentation volumes and lower rheological parameters (viscosity, yield stress, degree of thixotropy and elasticity). The lower and the medium viscosity polymer were simultaneously and consecutively added in a mass ratio of 50:1 and 10:1. The resulted observation of low viscosity and yield stress, and more importantly thixotropy and elasticity, can be interpreted in terms of a “site-blocking” type flocculation.     

Cure behavior of diglycidylether of bisphenol A/trimethylolpropane triglycidylether epoxy blends initiated by thermal latent catalyst

Cure behaviors of diglycidylether of bisphenol A (DGEBA)/trimethylolpropane triglycidylether (TMP) epoxy blends initiated by 1 wt % N‐benzylpyrazinium hexafluoroantimonate (BPH) as a cationic latent catalyst were investigated using DSC and rheometer. This system showed more than one type of reaction and BPH could be excellent thermal latent catalyst without any co‐initiator. The cure activation energy (E_a) obtained from Kissinger method using dynamic DSC data was higher in DGEBA/TMP mixtures than in pure DGEBA. Rheological properties of the blend system were investigated under isothermal condition using a rheometer. The gel time was obtained from the analysis of storage modulus (G′), loss modulus (G″) and damping factor (tanδ). The crosslinking activation energy (E_c) was also determined from the Arrhenius equation based on the gel time and curing temperature. As a result, the crosslinking activation energy showed a similar behavior with that obtained from Kissinger method. And the gel time decreased with increasing TMP content, which could be resulted from increasing the activated sites by trifunctional epoxide groups and decreasing the viscosity of DGEBA/TMP epoxy blend in the presence of TMP. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2114–2123, 2000     

The role of interfacial modifier in toughening of nylon 6 with a core‐shell toughener

The effects of nylon 6 matrix viscosity and a multifunctional epoxy interfacial modifier on the notched impact strength of the blends of nylon 6 with a maleic anhydride modified polyethylene‐octene elastomer/semi‐crystalline polyolefin blend (TPEg) were studied by means of morphological observation, and mechanical and rheological tests. Because the viscosity of the TPEg is much higher than that of nylon 6, an increase in the viscosity of nylon 6 reduces the viscosity mismatch between the dispersed phase and the matrix, and increases notched impact strength of the blends. Moreover, addition of 0.3 to 0.9 phr of the interfacial modifier leads to a finer dispersion of the TPEg and greatly improves the notched impact strength of the nylon 6/TPEg blends. This is because the multi‐epoxy interfacial modifier can react with nylon 6 and the maleated TPEg. The reaction with nylon 6 increases the viscosity of the matrix while the coupling reaction at the interface between nylon 6 and the maleated TPEg leads to better compatibilization. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2664–2672, 1999     

Interface,morphology, and the rheological properties of polymethylmethacrylate/impact modifier blends

Impact modifiers with grafted PMMA shell are used to modify polymethylmethacrylate matrix. The composition of the shell is chosen to enhance the interactions at the modifier/matrix interface and to obtain good dispersion of the impact modifier in order to optimize impact strength of the blend. The degree of interactions at the interface is characterized by the interfacial region where the chains of the matrix mix with those of the shell of the modifier. The deviation of the measured viscoelastic behavior of these blends from that predicted by the emulsion models has been attributed to the formation of the network structure due to the association of matrix chains with the shell of the modifier. It is expected that the network structure will decrease with increasing frequency and, as such, the effective volume of the particle is frequency dependent. This study uses the emulsion models to estimate the larger effective volume of the particle and, therefore, the extent of interaction at the interface. In the blends of this study it can be shown that at low modifier levels the solvent swelling of the modifier shell results in stronger interactions with the matrix; this effect is negated by the aggregation of particles at higher modifier loadings. The interaction of core modifier with the PMMA matrix seems to be similar to that of the core-shell modifier. This would not be expected from the calculated interfacial thickness of approximately 4 nm. It is, therefore, proposed that during melt-processing the core modifier surface was altered due to grafting of the matrix PMMA chains during melt-blending to (BA/St) copolymer of the core modifier thus reducing the interfacial tension. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2623–2634, 1998     

Turbulent Drag Reduction with an Ultra-High-Molecular-Weight Water-Soluble Polymer in Slick-Water Hydrofracking

Water-soluble polymers as drag reducers have been widely utilized in slick-water for fracturing shale oil and gas reservoirs. However, the low viscosity characteristics, high operating costs, and freshwater consumption of conventional friction reducers limit their practical use in deeper oil and gas reservoirs. Therefore, a high viscosity water-soluble friction reducer (HVFR), poly-(acrylamide-co-acrylic acid-co-2-acrylamido-2-methylpropanesulphonic acid), was synthesized via free radical polymerization in aqueous solution. The molecular weight, solubility, rheological behavior, and drag reduction performance of HVFR were thoroughly investigated. The results showed that the viscosity-average molecular weight of HVFR is 23.2 × 10⁶ g⋅mol⁻¹. The HVFR powder could be quickly dissolved in water within 240 s under 700 rpm. The storage modulus (G′) and loss modulus (G″) as well as viscosity of the solutions increased with an increase in polymer concentration. At a concentration of 1700 mg⋅L⁻¹, HVFR solution shows 67% viscosity retention rate after heating from 30 to 90 °C, and the viscosity retention rate of HVFR solution when increasing C_NaCl to 21,000 mg⋅L⁻¹ is 66%. HVFR exhibits significant drag reduction performance for both low viscosity and high viscosity. A maximum drag reduction of 80.2% is attained from HVFR at 400 mg⋅L⁻¹ with 5.0 mPa⋅s, and drag reduction of HVFR is 75.1% at 1700 mg⋅L⁻¹ with 30.2 mPa⋅s. These findings not only indicate the prospective use of HVFR in slick-water hydrofracking, but also shed light on the design of novel friction reducers utilized in the oil and gas industry.     

A real‐time Mooney‐viscosity prediction model of the mixed rubber based on the Independent Component Regression‐Gaussian Process algorithm

With the rapid development of rubber industry, it becomes more and more important to improve the performance of the quality control system of rubber mixing process. Unfortunately, the large measurement time delay of Mooney viscosity, one of the most important quality parameters of mixed rubber, badly blocks the further development of the issue. The independent component regression‐Gaussian process (ICR‐GP) algorithm is used to solve such typical nonlinear “black‐box” regression problem for the first time to predict Mooney viscosity. In the ICR‐GP method, the non‐Gaussian information is extracted by the independent component regression method firstly, and then the residual Gaussian information is extracted by the Gaussian process method. Meanwhile, both the linear and nonlinear relationships between the input and output variables can be extracted through the ICR‐GP method. With the fact that there is no need to optimize parameters, the ICR‐GP method is especially suitable for “black‐box” regression problems. The highest prediction accuracy was achieved at M = 0.8765 (the root mean square error), which was high enough considering the measuring accuracy (M = ±0.5) of the Mooney viscometer. It is by using the online‐measured rheological parameters as the input variables that the measurement time delay of Mooney viscosity could be dramatically decreased from about 240 to 2 min. Consequently, such Mooney‐viscosity prediction model is very helpful for the development of the rubber mixing process, especially of the emerging one‐step rubber mixing technique. The practical applications performed on the rubber mixing process in a large‐scale tire factory strongly proved the outstanding regression performance of this ICR‐GP Mooney‐viscosity prediction model. Copyright © 2012 John Wiley & Sons, Ltd.