نتایج جستجو برای: glass transition temperature
تعداد نتایج: 742402 فیلتر نتایج به سال:
the glass transition temperature (tg) and the melting temperature (tm) of gelatin at water contents between 7 and 14% were measured using differential scanning calorimetry. the plasticisation of the polymer by water led to a decrease in tg and tm. the tg of partially crystalline gelatin was higher than that of the amorphous one obtained by quenching from the melt. the enthalpy relaxation occur...
the glass transition temperature of several pvac(1)-b-poly(ma-co-mma) (2) terpolymers with different fractions of methyl acrylate (ma) and methyl methacrylate (mma) repeating units in random copolymer (block 2) were calculated with barton, kwei and topological equations. the calculation was on the basis of the correlation between the fraction of repeating units in random copolymers and theoreti...
maleic anhydride (man) copolymers with methyl methacrylate(mma), ethyl methacrylate(ema), methyl acrylate(ma), ethyl acrylate (ea) and buthyl acrylate (ba) ( in a 1:1 mole ratio) were synthesized by free radical polymerizations method under vacuum -azobis(isobutironitrile)(aibn) as an initiator of reaction at 701c. the copolymer compositions were determined using related 1h nmr spectra techni...
In order to fabrication of transparent glass-ceramics with Li-mica nano crystals, the glasses with chemical composition of 94.9 mass% Li(1+x)Mg3AlSi3(1+x)F2 (x=0.5) with 5.1 mass% MgF2 were crystallized. The glasses were fabricated via the conventional melt-quenching technique. Mica crystals were precipitated in the glass phase by later heat treatment. Glass samples had glass transition tempera...
the thin gelatin films, prepared by casting of gelatin solutions at different drying temperatures, had different molecular morphologies as monitored, using wide angle x-ray diffraction (waxd) and differential scanning calorimetry (dsc) techniques. it was revealed that gelatin films dried at lower temperatures showed markedly higher crystalline or helical structure with slightly higher tg and lo...
بررسی راهکارهای بهبود خواص حرارتی و مکانیکی پلییورتانهای بر پایه گلایسیدیل آزید پلیمر(علمی-ترویجی)
Glycidyl azide polymer (GAP) is a unique elastomeric binder with high heat of formation and high density due to enhanced thermal and performance properties of composite solid propellants. However, GAP has high glass transition temperature and poor mechanical properties that are limited its application as a binder in a composite solid propellant. In this paper , the efforts carried out on modifi...
in order to fabrication of transparent glass-ceramics with li-mica nano crystals, the glasses with chemical composition of 94.9 mass% li(1+x)mg3alsi3(1+x)f2 (x=0.5) with 5.1 mass% mgf2 were crystallized. the glasses were fabricated via the conventional melt-quenching technique. mica crystals were precipitated in the glass phase by later heat treatment. glass samples had glass transition tempera...
Europium doped transparent lead fluorophosphate glass ceramics successfully were prepared with heat treatment of precourse glasses at temperature above glass transition (Tg). X-ray diffraction (XRD) experiment evidenced the formation of PbF2 nanocrystals in glassy matrix. The emission spectra investigation indicate that considerable amount of Eu3+ ions were trapped in crystalline phase, and the...
Glass is one of the oldest materials which have been used in human history. Till nowadays, glass has not lost its attraction. The macroscopically character of this object make it usable for many different applications. Whether its transparency or its opacity, this object is the most fascinating material. Indeed, the history of glass making goes back to the 3th Millennium BC in Near East and Lev...
Phosphate glasses have special applications, but tra,ditionally never have had both durability and a low glass transition temperature (making them hard to work with). A composition study was used to find a more durable, easily fabricated phosphate glass with a low glass transition temperature. Batching, melting, casting, annealing and fabrication of test parts were performed. Glasses were chara...
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