X-Ray-Studies of crystallization in swollen polyvinyl fluoride

Polyvinyl fluoride (PVF) shows a strong crystal interference caused by the lateral distances of the chains, and is highly crystalline. Over the temperature range 0—100°C the degree of crystallinity is about 86%. Gelation of PVF in γ-butyrolactone was studied over practically the whole range of concentrations (from pure PVF to 1% solution). Gel temperatures were found practically independent of concentration (174°C). Gelation is coupled with crystallization. The swollen samples showed no differences in degree of crystallinity and quality of the crystals compared with the pure polymer at the same temperature. Therefore the degree of crystallinity of the gels is solely a function of temperature. The crosslinks of the network are formed by crystalline regions. Only the amorphous regions in the gels can take up solvent. Caused by the high crystallinity the gels have a crumb-like nature.     

聚氟乙烯薄膜后处理工艺研究

考察了聚氟乙烯（PVF）薄膜干燥过程中溶剂初始含量、干燥温度对干燥前膜中溶剂含量和PVF膜的力学性能的影响。结果表明,干燥温度升高和溶剂初始含量减少会导致薄膜力学性能下降。当干燥温度为100℃时,采用配方4成型的PVF薄膜力学性能最佳。     

Structural changes in humic acids during the coalification process

Humic acids from four coals, varying in rank from peat to subbituminous coal, have been characterized by elemental analysis, acidic groups, molecular weight, electrophoresis and visible, FT-i.r. and CP/MAS ¹³C n.m.r. spectroscopy. The humic acids increase in carbon content, molecular weight, condensation degree and aromaticity (f_a) with increasing maturation of the parent coals, while the oxygen content decreases with a loss of oxygen functional groups. The presence of lignin-like polymers, poly-saccharides and peptidic materials in humic acids from peat was established using i.r. and ¹³C n.m.r. spectroscopy. The structural changes observed in humic acids are in agreement with the recognized coalification theory and tend to support the hypothesis of condensation of humic acids into insoluble humin of coal.     

Relaxation changes in polyacrylonitrile yarn during the heat-stretching process

Conclusions The stress in polyacrylonitrile yarns of various chemical structures and of various linear densities has been studied under isometric heat-treatment under static and dynamic conditions.Limits of the relaxation states have been determined over a wide range of temperature and rate (or duration) of yarn heating, in the contact and convective methods of heating.Translated from Khimicheskie Volokna, No. 6, pp. 29–30, November–December, 1989.     

Chemical changes during the mild air oxidation of pitch

The chemical changes occurring during mild oxidation of petroleum and coal tar pitch were studied by elementary analysis, solubility measurements, IR and nuclear magnetic resonance spectroscopy and chromatography. The oxidized pitches were compared with pitches which were distilled to give similar softening points. A mild oxidation was shown to induce dehydrogenative polymerization of the pitch components without introducing appreciable amounts of oxygen into the products. The greater reactivity of the petroleum pitch constituents to oxygen is attributed to the presence of alkyl substituents. Study of the mesophase formation and X-ray analysis of the derived graphites showed that mild air oxidation did not affect the subsequent graphitic development.     

Chemical and physical changes in cottonseed oil during deodorization

The effects of deodorization time and temperature on the physical and chemical properties of cottonseed oil were investigated. Higher temperatures and longer times lead to increases in free fatty acids, peroxide value, viscosity and refractive index while iodine value, unsaponifiable matter and induction period decreased.     

Chemical changes in the lipids of canola and flax seeds during storage

The changes in acid value (AV), peroxide value (PV), anisidine value (AnV), tocopherols and fatty acid composition in crushed flax, canola seeds or commercial poultry feed during a 60-day storage period in room temperature (RT) or cold room (CR) were examined. Storage at RT or CR increased AV, PV and AnV of flax and canola seeds. Regardless of storage condition, a 50% reduction in the content of tocopherols was observed in flax, canola and commercial feed samples at day-30 of storage. The changes in the content of polyunsaturated fatty acids were negligible during storage. These results may have implication in the storage and handling of animal feeds containing n-3-polyunsaturated fatty acid-rich oil seeds.     

聚醋酸乙烯酯乳液改性研究进展

综述了国内外对聚醋酸乙烯酯乳液的改性研究,如耐水性、稳定性等方面的研究进展,并对聚醋酸乙烯酯乳液的发展前景进行展望。     

氟化铵合成工艺进展

氟化铵是一种重要的无机氟化物,随着无机氟化工的发展,氟化铵越来越受到人们的重视。介绍了氟化铵的各种生产工艺,包括气相法、升华法、液相法,其中液相法又分为中和法和氨解法。着重介绍了磷肥副产氟硅酸生产氟化铵的工艺,并分析了其优缺点,指出今后氟化铵的研究发展方向。     

Structural performance of alkali/acid-ultrasound modified Agave fibers during the melt mixing process with polyvinyl alcohol

This study aims to investigate changes in the structural properties of alkali/acid-ultrasound modified Agave fibers and their performance immersed on a polyvinyl alcohol (PVA) matrix with plasticizer during melt mixing processing. Structural analysis revealed that ultrasound enhances the effectiveness of the conventional alkaline/acid treatments to modify fibers since the simultaneous treatment increased the partial removal of lignocellulosic components, water molecules, and amorphous regions which improved their processability on a PVA matrix. Specific energy consumption values indicated that during melt mixing the modified fibers required more energy to expose the chains of cellulose fraction to function as an interaction site for PVA chains. Once the mixture was homogenized, the fiber-matrix interactions promoted high viscosity, friction, and mechanical stress in the chamber. Therefore, the modified fibers restricted the interaction between plasticizer and PVA in the obtained films, resulting in a highly structured, and reinforced network, increasing the storage modulus as dynamic mechanical analysis indicated. These findings highlight a feasible way to valorize Agave fibers and allow the understanding of the matrix-fiber interactions during melt mixing processing, useful to predict the structural and mechanical properties of the films.     

聚乙烯醇缩丁醛合成新工艺研究

在不添加乳化剂的条件下,采用同时滴加盐酸(HCl)和聚乙烯醇(PVA)-正丁醛(BA)混合胶液,通过新型高效混合分散机制合成了聚乙烯醇缩丁醛(PVB)。研究结果表明:合成PVB的最佳工艺条件是m(BA)∶m(PVA)=0.60∶1、初始反应温度为30℃、pH为1.4左右、反应时间为2.5h和升温速率为10K/20min(最高至65℃);此时,BA利用率超过99%,并且PVB的透明度(超过96%)和雾度(低至0.2%)完全满足夹层安全玻璃的使用要求。     

高强高模聚乙烯醇纤维的生产工艺初探

采用凝胶纺丝,添加硼酸和助剂生产高强高模聚乙烯醇(PVA)纤维,探讨了其生产工艺。结果表明:控制纺丝原液PVA质量分数16%,添加硼酸质量分数1.0%～1.1%;采用Na_2SO_4/NaOH凝固浴体系,其中Na_2SO_4质量浓度为300g/L,NaOH质量浓度为80～100g/L,凝固浴温度45℃,凝固时间25s;选择4段拉伸,湿热拉伸倍数为6,总拉伸倍数为14;生产稳定,得到的高强高模PVA纤维断裂强度达15cN/dtex,模量达320cN/dtex。     

水相悬浮法氯化聚氯乙烯生产工艺

介绍了国内水相悬浮法氯化聚氯乙烯生产工艺的特点。     

Optimization of the spinning solution preparation process in the manufacture of polyvinyl chloride fibre

Conclusions The effect of spinning solution preparation parameters on the fibre preparation process and on the properties of polyvinyl chloride fibre have been studied using the experiment planning method.It has been found that the concentration and holding time of the spinning solution exert the greatest effect on the process of washing the fibre free of dimethylformamide.An optimization of the parameters of preparing a solution for polyvinyl chloride fibre production under manufacturing conditions has been carried out.Translated from Khimicheskie Volokna, No. 1, pp. 24–25, January–February, 1988.