Reentanglement Kinetics of Freeze-Dried Polymers above the Glass Transition Temperature

2012 ◽  
Vol 45 (16) ◽  
pp. 6648-6651 ◽  
Author(s):  
Chao Teng ◽  
Yun Gao ◽  
Xiaoliang Wang ◽  
Wei Jiang ◽  
Chen Zhang ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Freeze Dried ◽  
Kinetics Of

Cure Kinetics of Nanocomposites Prepared From Aqueous Dispersion of Nanoclay

2006 ◽  
Author(s):  
Levent Aktas ◽  
M. Cengiz Altan
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Storage Modulus ◽  
Glass Fibers ◽  
Aqueous Dispersion ◽  
Cure Kinetics ◽  
Temperature Cycle ◽  
Waterborne Epoxy ◽  
Kinetics Of

The effect of nanoclay on the cure kinetics of glass/waterborne epoxy nanocomposites is investigated. First step in sample preparation involves dispersing Cloisite® Na+, a natural montmorillonite, in distilled water at 70°C with the aid of a sonicator. Then, desired amounts of dicyandiamide and 2-methyl imidazole, serving as cross-linkers, are mixed to the aqueous nanoclay solution. As the mixing continues, Epi-Rez 3522-W-60 waterborne epoxy resin is introduced to the solution and the compound is mixed for an additional 30 minutes. The nanoclay content of this batch is adjusted to be at 2wt%. An identical second batch, which does not comprise nanoclay, is also prepared to serve as the baseline data. Glass/waterborne epoxy prepregs containing 30% glass fibers are prepared from these batches and used to characterize the effects of nanoclay. The evolution of viscoelastic properties during curing are characterized by the APA2000 rheometer. Using the storage and loss moduli profiles during curing, gel time and maximum storage modulus are characterized. Effect of nanoclay on the glass transition temperature is determined by applying an additional temperature cycle following the cure cycle. In addition, mechanical performances of the samples are characterized by three point bending tests. Nanoclay is observed to yield 2-fold higher storage modulus during curing. Rate of curing is measured to be substantially slower for the samples comprising nanoclay. In addition, glass transition temperature improved by 5% to 99°C with the addition of nanoclay compared to 94.5°C for the samples without nanoclay. Flexural stiffness of the samples containing nanoclay is measured to be 20% higher than the samples without nanoclay while the strength remained virtually unaffected.

Water sorption isotherm and glass transition temperature of freeze-dried Syzygium cumini fruit (jambolan)

2014 ◽  
Vol 120 (1) ◽  
pp. 519-524 ◽  
Author(s):  
Roneval Felix de Santana ◽  
Eliseu Ribeiro de Oliveira Neto ◽  
Alysson Vieira Santos ◽  
Cleide Mara Faria Soares ◽  
Álvaro Silva Lima ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Sorption Isotherm ◽  
Water Sorption ◽  
Syzygium Cumini ◽  
Water Sorption Isotherm ◽  
Freeze Dried
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