Controllable Growth of Gradient Structures for Biomedical Applications
0
Citation
0
Reference
10
Related Paper
Abstract:
Co-continuous phase structures of immiscible polymers can be developed under appropriate melt-blending conditions. Because of the presence of interfacial tension, such co-continuous structures start to coarsen when heated to a temperature higher than the melting/softening temperature of both phases. In this article, a systemic study of controllable growth of gradient porous structures utilizing variable coarsening rates in either a gradient temperature field or a gradient shear field is presented. Based on experimental results, the gradient of shear viscosity is identified as the mechanism for generating variable coarsening rates inside a co-continuous blend. By controllable variation of the shear viscosity distribution in a blend, a spatially varied and controllable gradient in phase structure is created. After dissolution of one of the two phases, the desired porous structure of the remaining polymer is obtained. A poly (lactic acid) (PLA)/polystyrene (PS) 50/50 wt% blend was used as a model system. By designing proper thermal and/or dynamic boundary conditions and introducing different thermal/shear rate gradients during annealing, several gradient porous structures of PLA were created.Keywords:
Temperature Gradient
Polystyrene
Both polystyrene films and polystyrene films filled with fullerenes (C60) were fabricated by the solution cast method. Mechanism of fullerene-polystyrene interaction, the structural characteristics of films, and their antimicrobial activity were researched. We found that the polystyrene/fullerene composite films manifest bacteriostatic and fungistatic effect.
Polystyrene
Expanded polystyrene
Cite
Citations (16)
Cell structure
Cell size
Cite
Citations (7)
Thermal gravimetric analysis (TG) and differential thermal analysis (DTA) experiments were used to investigate the thermal decomposition characteristics and kinetics of polystyrene and polystyrene/fir, which are of potential interests for the development of renewable energy. The results show polystyrene takes place only one step weight loss, while polystyrene/fir takes place two-step weight loss. The thermal decomposition peak temperature of polystyrene shifts to higher temperature in the presence of fir, but the main reaction temperature range of polystyrene becomes narrow. The kinetic behaviors were investigated under different heating rates by using Kissinger method and Flynn-Wall-Ozawa method. The activation energy of polystyrene is larger than that of polystyrene/fir. This can explain that fir promotes the decomposition of polystyrene. The experimental results and kinetic parameters may provide useful data for the design of co-pyrolytic processing of polystyrene/fir.
Polystyrene
Thermogravimetric analysis
Pyrolytic carbon
Cite
Citations (2)
Abstract The softening rates of ‘Rome’ apples ( Malus domestica Borkh.) from 10 West Virginia orchards stored at two temperatures were compared in 1974, 1976, and 1978. The rate of softening at 20°C declined with time after harvest, and delaying harvest reduced the rate of softening at 20° but had little effect on softening at 0°. Site had little effect on rate of softening. In two of the three years, the rate of softening at 0° was found to be correlated with firmness at harvest and softening at 20°. Regression analysis provided formulas that can be used to predict softening rate in refrigerated air storage at 0° from firmness data at harvest.
Malus
Cite
Citations (9)
Softening of the flesh is one of the most dramatic changes accompanying the ripening of many fruits. Although other parameters of quality are important, the peak of fruit ripeness is usually associated with a fairly narrow range of firmness. Furthermore, texture that is considered optimal for fruit consumed fresh may not be best for fruit that is processed. Softening undoubtedly reflects changes in cell walls of fruit tissues as the fruit progresses through ripening into senescence. Once the process is initiated in mature fruit, the period of acceptable texture may be short, even with refrigeration and controlled atmosphere storage. A prerequisite to improved methods of controlling softening, whether to initiate and accelerate it or to prevent softening beyond the optimum stage, is an understanding of cell wall structure, its changes, and the enzymes involved in its degradation. I. Histology of Fleshy Fruits. Appreciation of the biochemical aspects of fruit softening
Ripeness
Flesh
Texture (cosmology)
Cite
Citations (51)
Polystyrene
Cite
Citations (14)
Flesh
Cite
Citations (12)
Polystyrene
Degradation
Expanded polystyrene
Cite
Citations (158)
Reduced viscosity
Atmospheric temperature range
Inherent viscosity
Apparent viscosity
Cite
Citations (5)
The changes of cell wall structure,composition and hydrolytic enzymes in fruit softening process are summarized in the present paper.In most cases,the occurrence of fruit softening is due to the degradation caused by polygalacturonase,cellulase,pectinmethylesterase,β-galactosidase.The degradation will lead to the changes of cell wall structure and composition,and in the end the fruit softening occurs.The other research results show that the other factors are also involved in the fruit softening process,and thus it is very important to intensify the physiology and biochemical study referring to fruit softening.
Degradation
Cite
Citations (0)