Physico-chemical and mechanical properties of coir-coconut husk reinforced LDPE composites: influence of long term acid ageing

This work investigates the physical, chemical, and mechanical properties of coir-coconut husk powder reinforced low-density polyethylene composites exposed to an aggressive (acidic) environment. The composites were prepared by the melt mixing moulding method. The fabricated composites were immersed in an acidic environment of pH 2.2 for a period of 27, 54, and 81 days. Two variants of samples were prepared namely: unreinforced samples (C-1) and reinforced samples (C-2). The unreinforced polymer samples (C-1) were obtained before ageing (C-1-0d), and after ageing (C-1-27d, C-1-54d, and C-1-81d), and also, the reinforced polymer samples (C-2) were obtained before ageing (C-2-0d), and after ageing (C-2-27d, C-2-54d and C-2-81d). Hardness, X-ray diffraction (XRD), friction, wear, and water absorption studies were carried out on the samples. From the experimental results, after immersion in the acidic solution for 27, 54, and 81 days, the hardness values of samples C-1 (acid-aged variants) increased by 12.3, 19.4, and 31.5% with hardness values of 16.53 Hv, 18.0 Hv, and 21.7 Hv, respectively. For C-2 samples, the hardness value increased by 6.50% and 17.3% after immersion in the acidic solution for 27 and 54 days with increments from 35.47 Hv (hardness value for C-2-0d sample) to 37.93 Hv and 42.87 Hv, respectively. The crystallinity of the LDPE polymer- C-2-54d sample, indicates its increasing strength since the intermolecular bonding is more significant in the crystalline phase. The study concluded that acid ageing has a noticeable influence on the physico-chemical and mechanical properties of coir-coconut husk powder reinforced low-density LDPE composites.