کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5204585 | 1381965 | 2006 | 6 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Gamma irradiation effects on poly(hydroxybutyrate)
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موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی آلی
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چکیده انگلیسی
Brazilian poly(hydroxybutyrate), PHB, as well as its copolymer, poly(hydroxybutyrate-co-valerate), P(HB-co-HV), containing 6.3 mol% of valerate, were irradiated with γ radiation (60Co) at ambient temperature and in the presence of oxygen. The viscosity-average molar mass (Mv) was analyzed by the viscosity technique using an Ostwald-type capillary viscometer. The polymers showed a decrease in molar mass with the increase in dose, reflecting the scissions that occurred at random in the main chain. The value G (scissions/100 eV of energy transferred to the system) and the parameter α (scissions per original molecule) were also obtained by the viscosity technique. The melting temperature (Tm) was determined by differential scanning calorimetry (DSC) and showed a decrease with increasing irradiation dose. Analyses of DSC also revealed double endothermic peaks, associated with the polymorphic transitions, which became a single peak with increased dose. Thermogravimetry analysis (TGA) revealed small differences between the decomposition temperatures of the irradiated and non-irradiated samples. The degree of crystallinity of PHB samples, on the other hand, which were obtained by the DSC and X-ray diffraction techniques, increased with the irradiation dose. Changes in the lattice parameter of the irradiated samples and in the size of the crystallites were also observed by X-ray diffraction. The samples used in this work did not pass through any purification process and were analyzed in powder form, exactly as they arrived from the factory.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Polymer Degradation and Stability - Volume 91, Issue 9, September 2006, Pages 2157-2162
Journal: Polymer Degradation and Stability - Volume 91, Issue 9, September 2006, Pages 2157-2162
نویسندگان
LetÃcia M. Oliveira, Elmo S. Araújo, Selma M.L. Guedes,