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Relationship between pore structure with residual pore and mechanical properties of expanded graphite nanocomposites at varying molding pressures
Author(s) -
Goudarzi Rahimeh,
Hashemi Motlagh Ghodratollah
Publication year - 2021
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.50994
Subject(s) - materials science , composite material , molding (decorative) , flexural strength , scanning electron microscope , compression molding , porosity , exfoliation joint , graphite , bar (unit) , flexural modulus , nanocomposite , graphene , mold , physics , meteorology , nanotechnology
Abstract The main challenges of developing expanded graphite (EG) composites are to improve the diffusion of polymer chains into EG pores and consequently to reduce the residual pore as defects in the final composites. In this paper, composites of unsaturated polyester (UP) resin containing 0.75 wt% EG are prepared at varying molding pressures of 1, 10, 20, and 30 bar. The EG particles are prepared at different exfoliation temperatures in the range of 700 to 900°C to have EGs with different porous structures. The scanning electron microscopy (SEM) micrographs show that residual pores are observed in the composites prepared at a low pressure of 1 bar. However, when the molding pressure increases, the number of the residual pores decreases and consequently the flexural properties improve. The highlighted improvements achieved by increasing the molding pressure from 1 to 30 bar are a decrease in the value of the residual pore from 23% to 3%, an increase in the flexural modulus from 1523 to 1744 MPa, and an increase in the flexural strength from 30.6 to 54.5 MPa. Interestingly, applying higher molding pressure affects the composites containing EGs with the highest degree of porosity, or rather larger pores, more remarkably.