遥爪丁腈共聚物的增韧环氧－聚氨酯IPN及PVC共混物的合成与表征

Ⅰ. 增韧环氧／聚氨酯互穿网络聚合物的合成与表征 用部分环氧树脂与丁腈羧反应，进行端基转化，制得端环氧基丁腈－环氧共聚物与环氧树脂的混合物，经叔胺固化后，得到增韧环氧（TEpx）。制备了两种IPN体系，体系1为增韧环氧／蓖麻油聚氨酯IPN，体系2为增韧环氧／聚醚聚氨酯IPN。用红外光谱研究了动力学，研究结果是，对于体系1，－OH基与－NCO基的反应速度大于环氧基的聚合速度，因此，IPN体系中，PU网络的形成比环氧网络快。环氧上的－OH基与蓖麻油上的羟基相似。同属伸羟基，它也会与－NCO基反应，因此，所形成的IPN的两网络间，存在着一定程度的化学交联。在增韧环氧的分子结构中，含有丁腈羧低聚物链段，使得增韧环氧与蓖麻油聚氨酯的相容性较好，该因素对这种IPN形态结构的形成，是很重要的，从动态力学性能的测试结果，能说明这个问题，即玻璃化转变峰很宽，在一定组成时，半峰宽几乎达100 ℃。对于体系2，聚氨酯相起反应的羟基是伯羟基，它与－NCO基的反应速度比环氧中的羟基与－NCO基的反应速度大得多。此外，体系中的两组分，即增韧环氧与聚醚聚氨酯的相容性不好，反应速度的差别与相容性的差别，均将导致反应体系中相分离程度的增大。这在tanZ-T曲线上表现得很明显，出现了两个相距甚远的玻璃化转变峰。利用透射电子显微镜对两个IPN体系进行了形态观察，这些IPN具有特殊的结构，既有增韧环氧所存在的两相结构，又有IPN的两相结构。Ⅱ. 聚氯乙烯－丁腈羟低聚物共混物的合成与表征 制备了高聚物（PVC）－低聚物（HTBN）共混物，研究了该共混物的力学性能，阻尼性能及形态结构。研究结果表明，在HTBN中，丙烯腈含量较高时，随着HTBN加入量的增加，PVC的阻尼峰均有不同程度的加宽加高。在力学性能方面，共混物的抗张强度、伸长率也随低聚物中丙烯腈含量的高低而变化，丙烯腈含量较高时（25％，36％），随HTBN加入量的增加，性能变化不大，而丙烯腈含量较低时（15％，5％），当HTBN的加入达一定量时，性能发生突降。这些现象的出现，主要与相容性有关，HTBN中丙烯腈含量高，极性大，与PVC混溶性好，因而阻尼性能、力学性能均好。而HTBN中丙烯腈含量低，与PVC之间的粘合力不好，即混溶性不好，因而共混物性能不好。由TEM照片看，该共混体系的形态结构为细胞状结构，细胞内存在着界面模糊的两相结构，在低丙烯腈含量（15％）时，存在着部分界面清晰的两相结构，形态观察的结果与性能测定的结果一致。

The study on a PVC membrane electrode for gemfibrozil

In this paper, a poly(vinyl chloride) (PVC) membrane electrode is prepared for gemfibrozil, 2, 2-dimethyl-5(2,5-xylyloxy) valeric acid, based on its ion pair complexes with hexadecyltrioctyl ammonium iodide (HTOA). The membrane composition of the electrode was optimized by using the sequential level elimination method for orthogonal experimental design. The electrode has a Nernstian response range from 2.5 X 10(-5) to 0.1 mol/l with an average slope of 55.3 mV/decade. The limit of detection is 7.1 X 10(-6) mol/l. The electrode responses were not affected by pH in the range 10.0-12.3. A Na2B4O7-Na2CO3 buffer of pH = 11.0 was selected as the background electrolyte solution for potentiometric measurements. The electrode was used for determining gemfibrozil in pharmaceutical preparations with satisfactory results.

Mercury(II) ion sensing with PVC-matrix based membrane sensors

Thiosemicarbazone derivatives have been used as ion carriers for the preparation of PVC-matrix based mercury(II)-selective membrane sensors. The electrodes give near-Nernstian responses in the linear concentration range of 1.0×10-1-5.0×10-6 M with detection limits of the order of 10-6 M. The stable potentiometric signals are obtained within a short time period of 20-25s. The effect of different plasticizers has been studied and dioctylsebacate (DOS) found to give a better response in comparison to other plasticizers. Selectivity coefficient values (log KPotHg,M) have been evaluated using fixed interference method. Better selectivity for mercury(II) ions is observed over many of the monovalent (Na+, K+ and NH4+) and divalent ions (Mg2+, Ca2+, Zn2+, Pb2+, Ni2+, Co2+, etc.). The sensors have also been used as indicator electrodes in potentiometric titration of mercury(II) ions with EDTA and its determination in synthetic water samples.

PVC/ABS共混系统力学性能的研究

用冲击试验机、材料试验机和另外一些相关的仪器对PVC/ABS共混体系的力学性能进行了测试、研究,结果发现,PVC/ABS共混体系的性能是组分的函数.ABS的加入改善了PVC/ABS共混体系的力学性能,随着ABS的增加,体系的冲击强度和断裂伸长率明显地提高,而体系的拉伸强度、拉伸模量几乎是随ABS含量的增加而单调地下降.

The influence of arrangement of St in MBS on the properties of PVC/MBS blends

Three series of MBS core-shell impact modifiers were prepared by grafting styrene and methyl methacrylate onto PB or SBR seed latex in emulsion polymerization. All the MBS modifiers were designed to have the same total chemical composition, and MMA/Bd/St equals 30/42/28, which is a prerequisite for producing transparent blends with PVC. Under this composition, there were three different ways of arrangement for styrene in MBS, which led to the different structure of MBS modifier. The concentration of MBS in PVC/MBS blends was kept at a constant value of 20 wt.%. The effects of arrangement of St in MBS on the mechanical and optical properties of PVC/MBS blends were studied. The notched Izod impact test results showed that the MBS with a PB homopolymer core grafted with St had a lowest brittle-ductile transition (BDT) temperature and BDT temperature increased with the amount of St copolymerized with Bd in the core of MBS. The transparency of blends also increased with the amount of St copolymerized with Bd in the core. TEM results showed that the arrangement of St in MBS influenced the deformation behavior. Two deformation modes were observed in the blends: cavitation and shear yielding.

Transition from crazing to shear deformation in ABS/PVC blends

ABS/PVC blends were prepared over a range of compositions by mixing PVC, SAN, and PB-g-SAN. All samples were designed to have a constant rubber level of 12 wt % and the ratio of total-SAN to PVC in the matrix of the blends varied from 70.5/17.5 to 18/80. Transmission electron microscope and scanning electron microscope have been used to study deformation mechanisms in the ABS/PVC blends. Several different types of microscopic deformation mechanisms, depending on the composition of blends, were observed for the ABS/PVC blends. When the blend is a SAN-rich system, the main deformation mechanisms were crazing of the matrix. When the blend is a PVC-rich system, crazing could no longer be detected, while shear yielding of the matrix and cavitation of the rubber particles were the main mechanisms of deformation. When the composition of blend is in the intermediate state, both crazing and shear yielding of matrix were observed. This suggests that there is a transition of deformation mechanism in ABS/PVC blends with the change in composition, which is from crazing to shear deformation.

PB-g-PMMA核壳粒子的合成及其在PVC中的分散

聚丁二烯(PB)橡胶粒子与聚氯乙烯(PVC)不相容。采用乳液聚合手段,在聚丁二烯乳胶粒表层接枝与聚氯乙烯相容的聚甲基丙烯酸甲酯(PMMA)充当增容剂制备了聚丁二烯接枝聚甲基丙烯酸甲酯(PB g PMMA ,MB)核壳粒子。用熔融共混法制备了PVC/MB共混物。SEM照片表明,这种核壳结构的粒子在聚氯乙烯中的分散情况随着核壳比的不同而改变,当核壳质量比小于93/7时能够完全均匀地分散在PVC基体中,核壳质量比大于94/6时根本不能分散在PVC基体中,核壳质量比为93/7是粒子能否分散开的转折点。共混物的力学性能数据表明,当MB加入量改变时,共混物也存在脆韧转变点,但受MB粒子的核壳比影响。