聚丙烯腈高分子半导体纤维的研究——聚丙烯腈高分子半导纤维的制备及其半导体特性

经四氯化锡处理的聚丙烯腈纤维,在进一步热处理过程中可以成为一种高分子半导纤维。它具有如下四个特点:1.纤维电阻率在10~3—10~(12)欧姆·厘米范围内可以控制热处理温度而随意调节。2.水解处理干燥后纤维的电阻值基本不变。3.有足够的机械强度可以进行多种形式的加工。4.纤维的电阻-温度、电导率-频率依赖关系,直流伏-安特性的试验结果表明它具有有机半导体特性,是一种兼有良好电性能和力学性能的高分子半导纤维。     

MECHANICAL BEHAVIORS OF POLYURETHANE-UREA ELASTOMERIC FIBERS UNDER STATIC STRETCHING DEFORMATION

The mechanical behaviors of polyether (ET) and polyester (ES) soft segment urethane-ureaelastomeric fibers constrained at different levels of elongation have been investigated by means ofdynamic mechanical tests and force-temperature measurements. The dynamjc mechanical re-sponse of the ET urethane-urea showed some difference from that of the ES as a function of exten-sion ratio. For force-temperature measuring the existence of a low temperature transition corre-sponding to the glass transition (T_(g's)) of the ester or ether soft segments, stress-softening tempera-ture (T_s) and initial melting temperature (T_(mh)) of hard segment crystallites was observed. The resultof cyclic testing of a constrained sample as a function of temperature indicated that the irreversibledecrease in stress implied a permanent change in sample microstructure.     

导电复合材料

导电复合材料是一种功能复合材料,它对电子工业及新技术的发展具有重大的意义。本文就导电复合材料的分类、性能、应用及最近的发展进行了简要的评述。     

ENHANCEMENT OF COMPATIBILITY OF POLYPROPYLENE AND NYLON-66 BY MALEATED POLYPROPYLENE

The compatibility of PP/N-66 blending system modified with maleated polypropylene was studied by means of SEM, DMA and other mechanical testing. It was found that when proper amount of modifier was applied, the compatibility was greatly enhanced and the impact toughness was significantly improved. An important direct evidence of the formation of the interfacial copolymer was also found. However, when excessive amount of modifier was used, the modification effect was not conspicuous. The phenomena were interpreted from a view of molecular motion that the interfacial block copolymer forced the two components to 'compatibilize' and many flexible PP molecules were set free from the restraint of the crystallites of plain PP so as to absorb much more impact energy.     

STUDIES ON PAN MACROMOLECULAR SEMICONDUCTING FIBER 1. PREPARATION OF PAN CONDUCTING FIBER TREATED BY STANNIC CHLORIDE AND ITS SEMICONDUCTING BEHAVIOUR

The PAN fiber treated by Lewis acid (e.g. stannic chloride) could be transformed into a macromolecular conducting fiber by further thermal treatment. Depending on thermal treatment condition the resistance of the fiber varied from 10~3 to 10~(12) Ωand kept stable after hydrolysis. The fiber has enough strength to be processed by various means. This is a new kind of macromolecular semiconducting fiber having some characteristics similar to those of organic semiconductors.     

MULTIPLE MELTING TRANSITIONS IN POLYURETHANE-UREA ELASTOMERS UNDER EXTENSION

Two melting transitions were observed in linear segmented polyurethane-urea elastomers underextension using thermal, mechanical and X-ray diffraction techniques, and the results are compared.These data indicate both strain-induced and temperature-induced crystallization in the stretchedclastomers, which may result from two different types of crystallites with different melting tempera-tures. These have been assigned as type 1 appearing around 60℃, and type 2 around 30℃. Thetype 1 crystallization can be induced by stretching at room temperature to large strain, and is mechani-cally reversible, but the type 2 crystallization is mainly induced by cooling below its crystallizationtemperature. These two crystalline structures are interchangeable under suitable conditions. Atelongations greater than 300%, the low temperature peak observed on fusion thermograms disappearsor combines with the high temperature peak. When the temperature of the sample is over the meltingpoint of the type 1 crystal, irreversible melting occurs and only the type 2 crystal develops on cooling.The results of stress-strain and stress hysteresis experiments at different temperatures indicate therelative importance of strain-induced and temperature-induced crystallization on the mechanicalproperties of these materials.