Effect of content and types of crosslinking monomers in copolymers containing isobutanol modified unsaturated polyester on the properties of unsaturated polyester resins

W wyniku polimeryzacji rodnikowej poliestru nienasyconego uzyskano kopolimery ze zmienną zawartością styrenu i dimetakrylanu glikolu dietylenowego jako monomerów sieciujących. Poliester nienasycony syntezowany był dwuetapowo z łatwo dostępnych surowców: bezwodnika maleinowego, glikoli etylenowego i 1,2-propylenowego oraz alkoholu izobutylowego. Zbadano wpływ monomerów sieciujących na reaktywność i lepkość nienasyconych żywic poliestrowych (NŻP) oraz scharakteryzowano właściwości mechaniczne i termiczne produktów polimeryzacji.As a result of radical polymerization of the unsaturated polyester, copolymers with variable content of styrene and diethylene glycol dimethacrylate as crosslinking monomers were obtained. The unsaturated polyester was synthesized in two steps from readily available raw materials: maleic anhydride, ethylene glycol, propylene glycol and isobutyl alcohol. The influence of crosslinking monomers on reactivity and viscosity of unsaturated polyester resins (UPR’s) was investigated. The mechanical and thermal properties of the polymerization products were characterized

Dietary calcium and bone density in adolescent girls and young women in Europe

The objective of this study was to investigate the association between dietary calcium intake and radial bone density among young women, over the whole range of intake and at different levels of calcium intake. The study design was a cross-sectional, observational multicenter investigation in six European countries. One thousand one hundred and sixteen healthy Caucasian girls aged 11-15 years and 526 women aged 20-23 years participated, after having been selected from larger population samples to represent a large range in calcium intake. Bone mineral density (BMD) was measured with dual- energy X-ray absorptiometry at the ultradistal and middistal radius. Calcium intake was assessed with 3-day food records. Other potential determinants of BMD were measured by anthropometry or questionnaires. Mean calcium intake among the girls varied between 609 mg/day in Italy and 1267 mg/day in Finland; intakes for women were in a similar range. After adjustment for height, weight, and age at menarche for the women, and adjustment for age, height, weight, Tanner stage, and bone area for the girls, radial BMD at both sites did not significantly vary among quartiles of calcium intakes for both age groups. In multivariate linear regression, calcium was weakly positively associated with BMD at both sites in the girls (per 100 mg of calcium: β = 0.57 mg/cm2, p = 0.03 for middistal BMD and β = 0.56 mg/cm2, p = 0.01 for ultradistal BMD). For middistal BMD, the association was observed predominantly in premenarcheal girls. The associations were no longer statistically significant after full adjustment for all determinants of BMD, except again in pre-menarcheal girls. Radial BMD in the women was not associated with calcium intake, except after full adjustment for determinants of BMD, when ultradistal BMD became inversely associated with calcium intake (per 100 mg β = -1.02, p = 0.03); this finding was due to results in one of the countries and not found in other countries. There was no evidence for a different relation between calcium and BMD at different levels of intake; although there was a positive association at calcium intake levels <600 mg/day, the interaction was not significant and there was no consistent trend over intake categories. These results do not support the hypothesis that dietary calcium is a determinant of peak BMD in European women, for a wide range of intake. This study does not provide evidence that Recommended Dietary Allowances for calcium should be increased.Chemicals/CAS: Calcium, Dietar