Synthesis of tetramethyl-p-silphenylenesiloxanedimethylsiloxane triblock copolymer by employing living anionic polymerization

Dimethylsiloxane-tetramethyl-p-silphenylenesiloxane-dimethylsiloxane (DMS-TMPS-DMS) triblock copolymer was synthesized by employing living anionic polymerization of hexamethylcyclotrisiloxane (D₃). Two synthetic methods were carried out for the polymerization. One of those methods was the anionic polymerization of D₃ initiated at the silanolate anion which was prepared from the terminal hydroxyl group of silanol-terminated TMPS prepolymer by reaction with n-butyllithium (method 1). The other was the coupling reaction of vinyl-terminated TMPS prepolymer with hydrosilyl-terminated DMS prepolymer obtained from the anionic polymerization of D₃ by using diphenylmethylsilanolate anion as initiator (method 2). In method 1, DMS contents of the copolymers ranged from 25.8 to 72.5 wt% and the values agreed with the ratio of D₃ to TMPS prepolymer. The weight-average molecular weights ranged from 1.36×10⁴ to 19.4×10⁴ and were close to the predicted values calculated from the $\text{M}\text{?}{}_{\mathrm{v}}$ of the TMPS prepolymer and the amount of D₃ added. In the case of method 2, weight-average molecular weights ranged from 19.5×10⁴ to 24.2×10⁴. The high molecular weight copolymer could thus be obtained by method 2. Intrinsic viscosity values of the triblock copolymers agreed with calculated values obtained by considering the copolymer as a binary mixture of these homopolymers. Differential scanning calorimetry and thermogravimetry were carried out on the triblock copolymers. The equilibrium melting temperatures of each of the copolymers were very close to that of poly-TMPS (160°C). The glass transition temperature and heat of fusion were decreased as the DMS content was increased. The thermogravimetric curves for the copolymers indicated that the thermal stability of the triblock copolymer was intermediate between the DMS and TMPS homopolymers.     

Shear rate dependence of viscosity and first normal stress difference of LCP/PET blends at solid and molten states of LCP

The liquid crystalline polymer (LCP) and polyethylene terephthalate (PET) were blended in an elastic melt extruder to make samples having 20, 40, 60, 80, and 100 wt % of LCP. Morphology of these samples was studied using scanning electron microscopy. The steady state shear viscosity (η), dynamic complex viscosity (η*) and first normal stress difference (N₁) were evaluated and compared at two temperatures: 265°C, at which LCP was in solid state, and 285°C, at which LCP was in molten state. The PET was in molten state at both the temperatures. The shear viscosity of the studied blends displayed its dependence on composition and shear rate. A maxima was observed in viscosity versus composition plot corresponding to 80/20 LCP/PET blend. The N₁ increased with LCP loading in PET and with the increased asymmetry of LCP droplets. The N₁ also varied with the shear stress in two stages; the first stage demonstrated elastic deformation, whereas second stage displayed dominant plastic deformation of LCP droplets. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2212–2218, 2007     

EFFECT OF NONSOLVENT ADDITIVES ON THE PORE SIZE AND THE PORE SIZE DISTRIBUTION OF AROMATIC POLYAMIDE RO MEMBRANES

In this paper discussions are made on the effect of nonsolvent swelling agents on the average pore size and pore size distributions at the surface of polyamide membranes which result from casting solutions involving above nonsolvent swelling agents.

The size of the polymer aggregate in the film casting solution and the size of polymer network pores are correlated to physicochemical data of ions which constitute the electrolytes used as nonsolvent swelling agents. As such ionic properties the charge density and the free energy of transition of ions from polyamide phase to water phase were considered. The validity of the correlation is limited in a range of casting solution composition where the polymer concentration in the casting solution is close to the limiting concentration of polymer at the phase boundary and the molar ratio of the nonsolvent swelling agent to the amide group involved in the polyamide polymer is equal to or slightly more than 0.7.     

乳化剂对醋苯丙核壳乳液性能的影响

简要叙述了乳化剂对聚合物乳液的影响。详细地讨论了AES、OP-10两种乳化剂对聚合物乳液最低成膜温度(MFT)、粘度、乳胶粒核壳结构等性能的影响。     

Influence of structure and counterions on physicochemical properties of linear alkylbenzene sulfonates

The effects of different inorganic and organic counterions on the physicochemical behavior of three commercial linear alkylbenzene sulfonates (LAS) have been studied. It has been found that the counterion hydration radius of the corresponding commercial linear alkylbenzene sulfonates has great influence on solubility, viscosity, surface tension and critical micelle concentration (CMC). The counterion has no influence on the detergency performance of the finished formulation. The alkyl chain length and the presence of tetralines have an important influence on solubility, viscosity and surface tension.     

毛细管动态挤出下聚合物熔体非线性流变行为的研究

采用毛细管动态流变仪,选用PELD、PP、PS和PA等典型物料,研究了毛细管动态挤出下各聚合物熔体的非线性流变行为。结果表明,不同物料的流变行为对振动力场的响应特性有较大差异,只有在一定的振幅和频率下振动力场才能有效降低熔体的黏度。实验首次发现,PP、PS和PA存在窄的振动参数区域,在此区域内,熔体的动态表观黏度值大于相应的稳态值,出现“加振变黏”现象。这一新的发现表明,并非“只要引入振动就一定有利于聚合物材料的成型加工”,必须考虑不同分子结构的聚合物材料对振动的不同响应规律。     

河工模型量测控制系统设计与应用——以赣江下游尾闾整治工程为例

赣江下游尾闾综合整治工程物理模型建于室外,且模拟河流多级分叉,对整个模型测控系统运行的可靠性以及室外的防雷性能提出了更高的要求。在分析现场情况的基础上,提出了一套较为先进的模型量测控制系统总体设计方案,控制系统由平水塔供水系统、流量控制系统、水位与流速测量系统、尾门控制系统、防雷接地系统、地形测量系统等量测子系统组成。简要介绍了各测量子系统工作原理,设计方案及实际应用情况,系统应用现代网络技术及高性能自动化测量仪器,可实现模型试验中各种参数的实时采集、控制和数据处理。试验结果表明,该测控系统可满足模型试验的测控需求。     

超支化聚酯树脂在涂料中的应用

超支化聚合物具有高度支化的分子结构,及大量官能端基,在合成工艺上易于工业化生产。简介了超支化聚酯的特性,及其在高固低黏涂料、UV固化和粉末涂料中的应用。     

Improvement in processability of metallocene polyethylene by ultrasound and binary processing aid

The effect of ultrasonic vibration and binary processing aid in improving the processability of metallocene linear low‐density polyethylene (mLLDPE) was investigated. During extrusion, ultrasonic vibration clearly reduced the die pressure and apparent viscosity of mLLDPE but had only a slight effect on its melt fracture. The effect of diatomite/PEG binary processing aid (BPA) was excellent in reducing the viscosity and eliminating the sharkskin fracture of mLLDPE. The effect of ultrasonic vibration and binary processing aid in improving the processability of mLLDPE was synergetic. With a combination of ultrasonic vibration and a small amount of processing aid, the flowability of mLLDPE was further improved, and the critical shear rate for the onset of sharkskin fracture was increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1927–1935, 2007     

吡咯烷基-N-甲酸,丙烯酸乙二醇酯的合成及其光聚合动力学的研究

合成了不含氢键的低粘度的吡咯烷基-N-甲酸-丙烯酸乙二醇酯(PLW),并采用实时红外光谱法检测了光强和光引发剂浓度对光聚合动力学的影响。随着光强的增加光聚合的最终转化率基本不变,但是光聚合速率有明显的增加,并且达到最大聚合速率的时间也缩短。随着光引发剂浓度的增加,最终转化率和最大聚合速率都有了显著的增加。所合成单体的转化率在30 s内能达到90%以上。