Gas transport properties of poly(n-alkyl acrylate) blends and modeling of modified atmosphere storage using selective and non-selective membranes

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Title: Gas transport properties of poly(n-alkyl acrylate) blends and modeling of modified atmosphere storage using selective and non-selective membranes
Author: Kirkland, Bertha Shontae, 1976-
Abstract: The gas transport properties of side -chain crystalline poly (n -alkyl acrylate ) and poly (m -alkyl acrylate ) blends are determined as a function of temperature for varying side -chain lengths , n and m , and blend compositions . The side chains of poly (n -alkyl acrylate )s crystallize independently of the main chain for n [is greater than or equal to] 10 which leads to an extraordinary increase in the permeability at the melting temperature of the crystallites . The compatibility of these polymers are examined and macroscopic homogeneity is observed for a small range of n and m when the difference /n - m / is between 2 - 4 methylene units . Thermal analysis shows that the blend components crystallize independently of one another ; at the same time , the crystallization of each component is hindered by the presence the other component . The permeation responses of these blends show two distinct permeation jumps as the crystallites from each component melt at their respective melting temperatures . Blends with continuous permeation responses are found to have higher effective activation energies than observed for common polymers . Thermal analysis proved to be a useful tool to help predict the permeation response for poly (alkyl acrylates ) ; thus the thermal behavior of poly (n -alkyl acrylate ) blended with n -aliphatic materials and random copolymers of poly (n -alkyl acrylates ) are briefly examined . A bulk modified atmospheric storage design is proposed where produce is stored in a rigid chamber that is equipped with both selective and non -selective membrane modules that help regulate the oxygen entering and the carbon dioxide leaving the produce compartment . The design enables control of the atmosphere inside the chamber by modulating gas flow , i .e . the gas flow rate and composition , through the non -selective membrane by delivering fresh air upstream of the non -selective membrane . The model shows that the choice of materials for the selective and non -selective membranes dictate the range of concentrations achievable ; however , the air flow rate allows the control between these ranges . The method to design a practical chamber from this model is also described .
URI: http : / /hdl .handle .net /2152 /3801
Date: 2008-08-29

Citation

Gas transport properties of poly(n-alkyl acrylate) blends and modeling of modified atmosphere storage using selective and non-selective membranes. Doctoral dissertation, The University of Texas at Austin. Available electronically from http : / /hdl .handle .net /2152 /3801 .

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