Back SearchTitle: WATER-BLOWN EXPANDABLE POLYSTYRENE. IMPROVEMENT OF THE COMPATIBILITY OF THE WATER CARRIER WITH THE POLYSTYRENE MATRIX BY IN SITU GRAFTING. I. MECHANISM OF FREE RADICAL GRAFTING
Page Range: p.1-18
Author(s): Pallay J; Berghmans H
File size: 149K
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Issue Year: cp
Volume: 21
Issue No: No. 1
Abstract
In the synthesis of water-blown expandable PS, granular starch as a carrier of water, the blowing agent, is grafted with PS by radical initiated polymerisation. Organic peroxides, such as tert-butyl perbenzoate or dibenzoyl peroxide, are used as free radical initiators. The graft polymerisation reaction is confirmed by FT-IR spectroscopy and SEM. The reaction leads to low level grafted starch. However, the amount of grafted polymer can be significantly increased using maleic anhydride in the monomer feed. The effect of concentration of maleic anhydride is studied. A reaction mechanism is proposed. 20 refs.
Title: WATER-BLOWN EXPANDABLE POLYSTYRENE. IMPROVEMENT OF THE COMPATIBILITY OF THE WATER CARRIER WITH THE POLYSTYRENE MATRIX BY IN SITU GRAFTING. II. INFLUENCE OF COMPATIBILISATION ON THE FOAM QUALITY
Page Range: p.19-33
Author(s): Pallay J; Berghmans H
File size: 215K
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Issue Year: cp
Volume: 21
Issue No: No. 1
Abstract
The compatibility of starch with the PS matrix in the synthesis of water-blown expandable PS is improved by making use of maleic anhydride. The foam morphology, on the contrary, is significantly changed after pre-expansion as the content of maleic anhydride is increased. It is found that starch is grafted during the polymerisation with styrene-maleic anhydride copolymer. Partial immiscibility of PS matrix and styrene-maleic anhydride grafts formed at higher concentrations of maleic anhydride causes the agglomeration of starch. Consequently, water, as the blowing agent, cannot be finely dispersed in the matrix, which is the reason of the irregular foam morphology. Different methods for the improvement of the compatibilisation are discussed. 4 refs.
Title: RHEOLOGICAL BEHAVIOUR OF ETHYLENE-OCTENE COPOLYMER VULCANISATES: EFFECT OF BLOWING AGENT AND PRECIPITATED ALUMINIUM SILICATE FILLER
Page Range: p.35-52
Author(s): Nayak N C; Bhattachariya A K; Tripathy D K
File size: 268K
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Issue Year: cp
Volume: 21
Issue No: No. 1
Abstract
The rheological behaviour of aluminium silicate filled ethylene-octene copolymer vulcanisates in extrusion containing blowing agent is studied. Cell morphology development is studied through scanning electron microscopy. Rheological properties of unfilled and aluminium silicate filled systems with variation of blowing agent, extrusion temperature and shear rate are studied using Monsanto processability testing (MPT). The total extrusion pressure, apparent shear stress, apparent viscosity and die swell of the unfilled and aluminium silicate filled compounds are determined using MPT. It is found that there is a reduction in stress and viscosity with blowing agent loading. It is observed that incorporation of blowing agent leads to decreased shear thinning behaviour, resulting in an increase in power law index. The viscosity reduction factor (VRF) of unfilled vulcanisates is found to be dependent on concentration of blowing agent, shear rate and temperature, whereas VRF of aluminium silicate filled vulcanisates is found to be independent of shear rate and temperature but dependent on blowing agent concentration. 32 refs.