Iranian Journal of Polymer Science and Technology
Year:2001 | Volume:14 | Issue:3 (ISSUE NO.53)|Papers Count:6

In polymerization, shortening of reaction time is always considered to be important. Although many methods can be used in order to decrease the reaction time but most of them have an adverse effect on product quality, for example, using too much initiator at high temperature, polymerization rate is increased but molecular weight decreases, so mechanical properties fall considerably. In this work, by using two initiators with different decomposition temperatures and selecting a proper heating rate a reduction in the length of time for polystyrene synthesis was observed while molecular weight remained constant.

In this research a product of triplet blend of polyvinyl chloride, acrylonitrile-butadiene-styrene, acrylonitrile butadiene rubber PVC/ABS/NBR) is obtained. The physical, mechanical and thermal behavior as well as morphology of the blend was studied.Results show that optimum properties in ratio PVC/ABS: 60/40 is obtained. For substituting the NBR by a portion of DOP to modify the migration to surface, a triplet blend of PVC/ABS/NBR was made. Experiments with constant amount of NBR and variable DOP and vice versa were carried out. For preparation of triplet blend from PVC/ABS, a ratio of 60/40 was used.The best results were obtained for a blend with NBR (10%) and PVC powder, 20% NBR and PVC granules containing 34% DOP and the thermoform ability of PVC/ABS/NBR blend was examined as well.

Polymer blends based on polyacetal (POM) and acrylomtrile butadiene rubber (NBR) were prepared by melt blending technique.The mixing parameters such as temperature, time and speed of mixing were varied to obtain a wide range of properties. The mixing parameters were optimized by evaluating the mechanical properties of the blend over a wide range of mixing conditions. The morphology of the blend indicated a two-phase structure. This study describes an attempt to improve the tensile strength of POM/NBR blends by means of compatibilization and dynamic vulcanization. A commercial compatibilizer, maleic anhydride (MA), has been used to control the phase morphology of the blend system. Dicumyl peroxide is used to dynamically vulcanize the NBR elastomer in the blend. The tensile strength of the compatibilized systems showed improvement. Dynamic vulcanization raises elastic recovery and tensile modulus of the blends, but the elongation at break decreases.

Particle size distribution is an important characteristic in suspension polymerization. Special condition must satisfy for achievement of an appropriate particle size distribution. This condition is studied for some systems. In this work the effect of parameters affecting the suspension polymerization system of styrene was studied and then the approximate optimum range was determined to obtain narrow particle size distribution mainly in the range of 200 to 400 microns. The studied parameters are: position of impeller, impeller type, impeller speed, baffles, stabilizer concentration, initiator concentration and divinylbenzene concentration as cross-linking agent.

Polydepsipeptides, copolymers of α - amino acids and α - hydroxy acids, could prove to be a valuable new class of synthetic biodegradable polymers. In this paper, steps in synthesis of poly (dl-lactide-co-3, 6-dimethylmorpholine-2,5-dione) from dl-Iactide and dl-3,6-dimethylmorpholine-2,5-dione was explained. dl -Lactide was synthesized from lactic acid. In the reaction of 2-bromopropionyl chloride and dl-alanine, N-(2-bromopropionyl)-dl-alanine was prepared and this material was converted to its salt and finally this salt was converted to 3, 6-dimethylmorpholine-2, 5-dione in a sublimer. These two monomers, that is, dl -lactide and dl-3, 6-dimethylmorpholine-2, 5-dione was polymerized by ring-opening polymerization. FT-IR, 1H NMR, 13C NMR Spectra were used for structure elucidation of all intermediate compounds and final product.  

Two types of polyurea and gelatin microcapsules were made, as these types of microcapsules are used in production of carbonless paper. The important parameters like: size distribution and types of microcapsules which affect the quality of carbonless paper were studied. For investigation of the effect of environmental parameters like humidity and temperature on quality of microcapsules and finally on quality of the image obtained from carbonless papers, from both types of microcapsules, CB papers with equal GSM (gram per square meter) were carried out. Samples of carbon less papers were subjected to different heat and humidity tests (aging test).The test results were investigated with quality of image obtained from these carbonless papers. Image quality reduction and deterioration of microcapsules in paper made by gelatin microcapsules and quality of image for papers made of polyurea microcapsules with respect to type of wall and also deterioration rate of microcapsules at different temperature and humidity conditions were studied.