DCP引发的熔融POE偶合反应的流变动力学

通过研究小振幅振动剪切流场对POE大分子偶合反应的影响,发现在线性粘弹区内增大振幅能够加速反应.由流变学方法计算反应相对转化率,研究了转化率、偶合反应速率系数和应变之间的定量关系,得到了反应速率系数与复数黏度形如经典Ahhenius方程的关联式.     

Chemorheology and ultimate behavior of epoxy‐amine mixtures modified with a liquid oligomer

Rubber toughening of epoxy resins has been actively studied since the 1960s with clear progress in understanding of the ultimate properties: microstructure relationships. The morphology, obtained after curing of the modified thermosetting matrix, is a function of the process conditions as well as of the materials used because both influence the thermodynamics and the kinetics of phase separation. In this work several amounts of poly(oxypropylentriamine) (POPTA), have been added as modifier to a diglycidyl ether of bisphenol‐A (DGEBA)‐based epoxy matrix cured with a cycloaliphatic amine. Molecular weight of the neat resin and amine/epoxy stoichiometric ratio have also been used as variables. This investigation has focused upon the importance of cure chemorheology for microstructure formation by using both physicochemical (isothermal and dynamic calorimetry) and rheological techniques. In the second part of this study, the influence of the molecular weight of the epoxy resin in the ultimate properties of 15 wt % POPTA‐modified epoxy matrices is also analyzed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1269–1279, 2000     

化学反应中聚合物流变动力学的研究进展

化学反应中聚合物流变动力学是联系化学反应动力学与聚合物流变学的交叉学科中的一类重要科学问题。文中从单体聚合、树脂固化、聚合物之间的反应以及聚合物接枝反应四方面综述了近年来聚合物流变动力学的研究进展,分析了尚存在的难点,并展望了其发展方向。     

基于流变动力学的UV体系固化速度表征方法研究

为了更好地表征UV体系固化速度,研究引发剂的种类与含量对聚酯丙烯酸酯固化过程中的影响,实验采用装有UV固化组件的流变仪,实时监测含有不同种类和浓度光引发剂的UV光油体系固化过程中的动态流变参数（弹性模量G＇）的变化,再通过曲线拟合、求导,来表征该UV体系固化速度。研究结果表明,含光引发剂DETX的UV固化体系在固化过程中,弹性模量G＇值达到平衡的时间短且平衡值较高,固化速度快、固化程度高;引发剂含量影响UV体系固化反应速率,引发剂含量过高反而会导致UV体系固化速率下降。     

4,4'/2,4'-二苯基甲烷二异氰酸酯/多元醇本体聚合流变动力学

采用转矩流变仪模拟双螺杆挤出反应条件,分别在无催化剂和铋/锌复合催化剂作用下进行4,4'/2,4'-二苯基甲烷二异氰酸酯/聚四氢呋喃醚二醇/1,4-丁二醇本体聚合,结合二维流动简化假设、黏度/分子量关联式和Arrhenius方程,建立了热塑性聚氨酯(TPU)重均分子量与反应体系转矩、温度的流变动力学方程,分别拟合得到无催化剂和催化剂作用时体系转矩与重均分子量的关联式;发现采用流变动力学方程模拟的TPU平均分子量与实时取样后采用凝胶渗透色谱法测定的结果吻合良好,采用流变动力学方法测量方便迅速,能提供整个反应过程中TPU平均分子量的变化情况。     

A low‐energy emulsification batch mixer for concentrated oil‐in‐water emulsions

This work shows the formation of a high internal phase ratio oil‐in‐water (O/W) emulsion using a new type of a two‐rod batch mixer. The mixture components have sharply different viscosities [1/3400 for water‐in‐oil (W/O)], similar densities (1/0.974 for W/O), and an O/W ratio of 91% (wt/wt). The simple design of this mixer leads to a low‐energy process (10⁶ < energy density [J m^?3] < 10⁷), characterized by low rotational speed and laminar flow. The droplet size distribution during the emulsification was investigated according to different physical and formulation parameters such as stirring time (few minutes < t < 1 h), rotational speed (60 < Ω < 120 rpm), surfactant type (Triton X‐405 and X‐100), concentration (from 1 to 15.9 wt % in water), and salt addition (30 g/L). We show that all studied parameters allow a precise control of the droplet size distribution and the rheology. The resulting emulsions are unimodal and the mean droplet diameter is between 30 μm and 8 μm. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Rheokinetics of free-radical polymerization

The authors elaborate theoretical concepts and obtain mathematical relations describing the increase in viscosity of reactive masses during bulk free-radical polymerization. The results obtained are confirmed experimentally for free-radical polymerization of alkyl methacrylates and styrene.     

Kinetics of glycidyl azide polymer‐based urethane network formation

Reactions between hydroxyl‐terminated glycidyl azide polymer (GAP) and different isocyanate curatives such as toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), and methylene diicyclohexyl isocyanate (MDCI) at various temperatures viz. 30, 40, 50, and 60°C were followed by Fourier transform infra red spectroscopy. The reactions were found to follow second‐order kinetics. With TDI and IPDI at 30°C, a two‐stage reaction was observed. For GAP‐TDI system, the second stage was slower than the first while for GAP‐IPDI system, the second stage was faster than the first indicating dominance of autocatalytic effect. The stage separation occurred due to the difference in reactivity of the isocyanate groups and was found to narrow down with increase in temperature. The viscosity build up due to the curing reaction was followed for GAP‐TDI system for comparison. The stage separation was evident in the viscosity build up also. Rheokinetic analysis done based on data generated showed a linear correlation between viscosity build up and fractional conversion. The kinetic and activation parameters evaluated from the data showed the relative difference in reactivity of the three diisocyanates with GAP. Both the approaches suggested that the reactivity of the isocyanates employed for the present study could be arranged as TDI > IPDI ? MDCI. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008