The Effect of Wheat Hay on Carbon Black Loaded EPDM Composite Studied by Positron Annihilation Lifetime Spectroscopy

Abstract

Abstract. The positron annihilation lifetime (PAL) technique has been applied to investigate the behavior of free volume hole in carbon black loaded ethylene propylene diene monomer (EPDM) composite as a function of the wheat hay concentration from 10 to 50 phr. The macroscopic studies including stress-strain, hardness and swelling behavior were measured too. An attempt is done to establish a correlation between the macroscopic measurements and the microscopic properties of the free volume holes. The ortho-positronium (o-Ps) parameters show a compact phase around 20 phr concentration of wheat hay. Such a phase is thought to be responsible for the maximum values of hardness, rupture stress, rupture strain and the minimum in the degree of swelling. Introduction Today, a renaissance in the use of natural fibers as reinforcements in technical applications is taking place mainly in the automobile and packaging industries [1, 2]. The availability of large qualities of such fibers with well-defined mechanical properties is a general prerequisite for the successful use of these materials. Coupled with the growing concern for disposal of agricultural and industrial waste and low cost fillers, considerable studies have been carried out on the utilization of some of these materials as fillers with elastomers and plastics as well as with thermoplastic elastomers. The PAL technique has been used to study the microstructure change in polymers and gives direct information about the free volume size and concentration [3, 4]. It was applied to investigate the behavior of the free volume (size and concentration) in carbon black loaded EPDM composites as a function of the concentration of wheat hay. Macroscopic studies including stress-strain behavior, hardness and swelling behavior were performed as an attempt to find a correlation between the positron annihilation parameters and the macroscopic results.