Volumetric shrinkage (collapse) in freeze-dried carbohydrates above their glass transition temperature

1995 ◽  
Vol 28 (2) ◽  
pp. 145-151 ◽  
Author(s):  
Guy Levi ◽  
Marcus Karel
2012 ◽  
Vol 45 (16) ◽  
pp. 6648-6651 ◽  
Author(s):  
Chao Teng ◽  
Yun Gao ◽  
Xiaoliang Wang ◽  
Wei Jiang ◽  
Chen Zhang ◽  
...  

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 ◽  
...  

2012 ◽  
Vol 91 (12) ◽  
pp. 1178-1183 ◽  
Author(s):  
M. Dewaele ◽  
J.G. Leprince ◽  
I. Fallais ◽  
J. Devaux ◽  
G. Leloup

Volumetric shrinkage reduction is a constant challenge in the improvement of dental resins. The inclusion of hyperbranched polymers (HBPs) with modified functionalities (hydroxyl, propionate, and methacrylate) instead of conventional dimethacrylate monomers has the potential to reduce shrinkage, but can also affect other properties. The null hypothesis was that the addition of HBPs (from 5 to 40 mass%) to a 50/50 mass% Bis-GMA/TEGDMA mixture reduces shrinkage without affecting degree of conversion, elastic modulus, glass transition temperature, Wallace hardness (before/after ethanol storage), and viscosity. This hypothesis was rejected, since HBP incorporation significantly affected most properties either negatively or positively. When HBP amounts in the resin were increased, the following general trends were observed: Volumetric shrinkage decreased significantly (p < 0.0001), down to about one-third of the control value at 40% HBP; Wallace hardness (both before and after ethanol) and viscosity increased progressively, while elastic modulus showed a parabolic profile, with a maximum at 10% HBP; and finally, degree of conversion and glass transition temperature were relatively stable, regardless of the HBP content. These results indicate that HBPs with modified end groups might be interesting substitutes for Bis-GMA/TEGDMA.


2008 ◽  
Vol 22 (2) ◽  
pp. 255-262 ◽  
Author(s):  
C OHKUMA ◽  
K KAWAI ◽  
C VIRIYARATTANASAK ◽  
T MAHAWANICH ◽  
S TANTRATIAN ◽  
...  

Author(s):  
Syed Ammar Hussain ◽  
Ahsan Hameed ◽  
Yusuf Nazir ◽  
Tahira Naz ◽  
Yang Wu ◽  
...  

Microencapsulation of polyherbal formulation (PHF) extract was carried out by freeze drying method, by employing gum arabic (GA), gelatin (GE), and maltodextrin (MD) with their designated different combinations as encapsulating wall materials. Antioxidant components (i.e total phenolic contents (TPC),Total flavonoids contents (TFC), and total condensed contents (TCT)), antioxidant activity (i.e. DPPH, &beta;-carotene &amp; ABTS+ assays), moisture contents, water activity (aw), solubility, hygroscopicity, glass transition temperature (Tg), particle size, morphology, in vitro alpha-amylase and alpha-glucosidase inhibition and bioavailability ratios of the powders were investigated. Amongst all encapsulated products, TB (5% GA and 5% MD) and TC (10% GA) has proven to be the best treatments with respect to the highest preservation of antioxidant components and their antioxidant potential by DPPH and &beta;-carotene assays and noteworthy for an ABTS+ assays, in addition, the aforesaid treatments also demonstrated lower moisture content, aw, particle size and higher solubility, hygroscopicity and glass transition temperature (Tg). All freeze dried samples showed irregular (asymmetrical) microcrystalline structures. Furthermore, TB and TC also illustrated the highest in vitro anti-diabetic potential due to great potency for inhibiting alpha-amylase and alpha-glucosidase activities. In the perspective of bioavailability, TA, TB and TC demonstrated the excellent bioavailability ratios (%).Futhermore, the phytochemo-profiling of ethanolic extract of PHF was also revealed to find out the bioactive compounds.


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