Morphology, Tensile Strength and Oil Resistance of Gum Rubber Sheets Prepared from Lignin Modified Natural Rubber

M Asrul,M Othman,M Zakaria,K Ahmad-Nazir,S Karuppanan,M Ovinis,A Tesfamichael Baheta,Z A Abdul Karim

doi:10.1051/matecconf/20141304001

M Asrul, M Othman + Show 6 more

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https://doi.org/10.1051/matecconf/20141304001

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Abstract

The paper describes the preparation of lignin filled natural rubber latex composite and its subsequent use to obtain lignin modified rubber. Two types of lignin i.e.: rubber wood and commercial alkali lignin were used as rubber filler. Gum rubber sheets were prepared from the lignin modified rubber and their properties were compared to Standard Malaysian Rubber (SMR 20) and a type of rubber obtained from the coagulation of high ammonia latex. Rubber morphology was investigated using Scanning Electron Microscope on the cross-sectional area of cryo-fractured samples. Oil resistance of the rubber sheets was determined by measuring the mass change before and after ASTM IRM 903 oil immersion, while the tensile strengths were determined according to ASTM D412 standard. Low values of tensile strength obtained for the commercial alkali lignin modified rubber sheet relative to the rest of the rubber samples was attributed to poor lignin dispersion. This occurrence was substantiated by the SEM analysis of cryo- fractured samples where crazes and inhomogeneity was observed. Nonetheless, both lignin modified rubbers exhibited higher level of oil resistance compared to SMR 20. This is due to the nature of lignin as a hydrophilic component and its presence in the rubber matrix complicates the oil diffusion process into rubber.

Highlights

Lignin is a complex polymer which is one the one of the major component in the structure of plants
The morphology of cryo-fracture sample examined under Scanning Electron Microscope (SEM) is a common method to determine phase structure and compatibility of polymer blends [10,11,12]
The presence of hydrophilic lignin would induce agglomeration and crazes in the rubber matrix contributing to more stress concentration site [14]. This SEM observation further supported the results of the tensile strength shown in the subsequent section where alkali lignin (AL) lignin modified rubber sheet exhibited the lowest tensile strength which corresponded to the presence of crazes and cracks

Summary

Introduction

Lignin is a complex polymer which is one the one of the major component in the structure of plants. In terms of material sustainability, lignin can be considered as a renewable raw material or sustainable chemical compound. The utilization of lignin in rubber can be traced back to the post World War era with the purpose of replacing carbon black as rubber filler after the 2nd World War. This research approach was encompassed in the US Government Synthetic Rubber Program [1] in 1941 due to the scarcity of rubber and other raw materials during the World War. In addition, the utilisation of lignin was motivated by its potential availability from the annual production of lignin amounting to more than a million tons from the pulp mills in the United States in the post war era.

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