جستجوی مقالات مرتبط با کلیدواژه "پلی پروپیلن گلیکول" در نشریات گروه "مواد و متالورژی"

For improving the mechanical and thermal properties of polyurethanes based on glycidyl azide polymer (GAP), a series of polyurethane elastomers with two soft segments were prepared from hexamethylene diisocyanate (HDI) / (GAP) / (PPG) /TMP and isophorone diisocyanate (IPDI) / GAP/ PPG/ TMP formulation. The weight ratio of soft segments GAP/PPG in polyurethane samples is changed as following order: 0:100, 30:70 and 50:50. For the study the structure – property relationships of polyurethane samples, the average molecular weight between cross-link junctions and effective cross-link density (νe) of samples were calculated from swelling and dynamic mechanical analysis tests. Both tests have shown that, as the GAP contents of copolyurethane samples are increased, molecular weight between cross-links (Mc) is increased. Also, dynamic mechanical analysis results of polyurethane samples have shown that by increasing of GAP ratio in the soft segment of polyurethane, the storage modulus at elastic region decreased and the glass transition temperature (Tg) have increased. As well as, hardness of samples is measured and indicated that by increasing the GAP extent of polyurethane samples, the migration of soft segment to the surface of polyurethane is improved and causes the dropping of the sample hardness.