The use of Modified and Unmodified Pig Hair Powder in Natural Rubber Compounding
Natural rubber (NR) in its raw gum state is tacky and fairly elastic but suffers some limitations such as poor resistance to weathering condition, low tensile strength and poor solvent resistance. These limitations are usually addressed by using chemical and natural additives on the NR. Pig hair was investigated as a natural additive and was subjected to various modifications such as acetylation, hydroxylation, sulphonation and carbonisation. Unmodified Pig Hair Powder (UPHP), Acetylated Pig Hair Powder (APHP), Hydrolyzed Pig Hair Powder (HPHP), Sulphonated Pig Hair Powder (SPHP) and Carbonized Pig Hair Powder (CPHP) were used as substitute for calcium carbonate due to their availability and cheaper cost to improve the mechanical properties of NR. The CaCO3, UPHP, CPHP, APHP, SPHP and HPHP were used for compounding and the physico-mechanical properties of the vulcanisates were evaluated. The X-ray fluorescence and Fourier Transform Infra-red Spectroscopy (FT-IR)were used to determine the elemental compositionsand functional groups of the unmodified and modified pig hair respectively. The XRF analysis showed that CPHP has the highest calcium content while O-H vibrational stretch was observed only in UPHPfrom the FT-IR result. The pH values of 5.64 and 5.90 for UPHP and CPHP at 27.4oCwere found to be weak acids respectively while SPHP was a strong acid with pH value of 1.65. However, HPHP and APHP were strong bases with pH values of 7.88 and 7.20 respectively. For the tensile strength and abrasion test, CPHV had the highest value while SPHV had the lowest value. Elongation at break showed that APHV had the highest value of 1436.60 %, which was lower than the value of CaCO3-vulcanizate (1632.00 %). The study showed that CPHP, APHP, HPHP and UPHP were good additives (reinforcement) and they could be substituted in parts for calcium carbonate filler in NR vulcanizates.
Keywords - CaCO3; compounding; fillers; rubber; pig hair powder.