Fracture Toughness of Vinyl Ester Composites Reinforced with Sawdust and Postcured in Microwaves

H Ku,M Prajapati,M Trada

doi:10.1155/2012/152726

Abstract

A commercial vinyl ester resin supplied by Hetron Chemical Pty. was reinforced with varying percentages by weight of sawdust. The sawdust particles were sieved into 3 different sizes, which were <300 μm, 300–425 μm, and 425–1180 μm, respectively, with a view to increase its fracture toughness for civil and structural applications. The sawdust used varied from 0% w/t to 15% w/t in step of 5% w/t. For higher w/t% of sawdust, the mixture would be too sticky to be mixed and cast. The cast composites were cured in ambient conditions and then postcured in microwave irradiation. They were then tested for fracture toughness using short bar tests. The values of fracture toughness of the composites increased with increasing particulate size, and this is due to the size distribution of the filler. It was found that the optimum amount of sawdust (425–1180 μm) was 15% w/t, with which the increase in fracture toughness was 126% as compared to neat resin and the reduction in cost was 15%. Furthermore, the optimum amount of sawdust (300–425 μm) was also 15% w/t, with which the increase in fracture toughness was 28.3% as compared to neat resin and the reduction in cost was again 15%.

Highlights

The most commonly used thermosets as composite matrices are unsaturated polyesters, epoxies, and vinyl esters
The values of fracture toughness of the composites increased with increasing particulate size, and this is due to the size distribution of the filler
It was found that the optimum amount of sawdust (425–1180 μm) was 15% w/t, with which the increase in fracture toughness was 126% as compared to neat resin and the reduction in cost was 15%

Summary

Introduction

The most commonly used thermosets as composite matrices are unsaturated polyesters, epoxies, and vinyl esters. Where mechanical properties and temperature tolerance of unsaturated polyesters no longer suffice, the epoxy is often used due to their significant superiority in these respects. Vinyl esters (VE), as they are usually called, are closely chemically related to both unsaturated polyesters and epoxies and in most respects represent a compromise between the two They were developed in an attempt to combine the fast and simple crosslinking of unsaturated polyesters with the mechanical and thermal properties of epoxies [1]. This research project is aimed at, investigating the fracture toughness of a commercial resole vinyl ester resin reinforced with sawdust with a view to its International Journal of Microwave Science and Technology applications in civil and structural engineering. The sample σ is made by casting the mixture of the resin, initiator, and the sawdust into the moulds

Materials

Fracture Toughness

Short Bar Test and the Samples

Results and Discussion

Conclusion