کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5190985 | 1381223 | 2006 | 12 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
The phase diagram of poly(4-hydroxybenzoic acid) and poly(2,6-hydroxynaphthoic acid) and their copolymers from X-ray diffraction and thermal analysis
دانلود مقاله + سفارش ترجمه
دانلود مقاله ISI انگلیسی
رایگان برای ایرانیان
کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی آلی
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
Homopolymers and copolymers of 4-hydroxybenzoic acid (HBA) and 2,6-hydroxynaphthoic acid (HNA) have been studied with differential scanning calorimetry and temperature-resolved wide angle X-ray diffraction. All polymers have more than one disordering transition between the glass transition (between 400 and 430Â K) and decomposition (between 710 and 750Â K). The first transition in PHBA at 616-633Â K is from orthorhombic rigid crystals to a conformationally disordered pseudo-hexagonal phase (condis phase). The two higher transitions are first, a further disordering process to a hexagonal condis crystal, and then a change to an anisotropic melt (liquid crystal) at about 800Â K, with increasing decomposition above 750Â K. In PHNA, orthorhombic crystals change above 600Â K to an orthorhombic condis crystal structure, which go to an anisotropic melt at 750Â K, and subsequent decomposition. In addition, using empirical entropy rules that account for the changes during the transitions from the crystal to the disordered mobile phases, an effort is made to understand the disorder and mobility, and to arrive at a non-equilibrium phase diagram of the copolymer system. The existence of a single, but up to 200Â K wide, glass transition and remaining high crystallinity of the copolyesters, indicate partial solubility of the repeating units in all phases. The new data are compared to and brought into agreement with the large number of prior measurements and often unclear interpretations.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Polymer - Volume 47, Issue 7, 22 March 2006, Pages 2369-2380
Journal: Polymer - Volume 47, Issue 7, 22 March 2006, Pages 2369-2380
نویسندگان
Anton Habenschuss, Manika Varma-Nair, Yong Ku Kwon, Jisheng Ma, Bernhard Wunderlich,