Withdrawal strength of fasteners in rice straw fibre-thermoplastic composites under dry and wet conditions

The withdrawal strength of nail and screw fasteners has been studied in rice straw fibre-thermoplastic composites. Two types of thermoplastic, virgin polyethylene (PE) and polypropylene (PP), were selected as separate composite matrices. Three levels of dry rice straw fibre, 45%, 60% and 75%, based on the composition by weight and passed through a 40-mesh size screen was mixed with the polymeric matrices without and with 2% (based on weight) maleic anhydride grafted polypropylene (MAPP) as coupling agent. A dry-blending method was used for compounding the materials. The 12 formulations for the polymer composites were used to prepare samples with dimensions 25 cm by 15 cm by 1 cm. The final composites were made by pressing the prepared mats between the hot plates of a compression press by employing combinations of temperature and pressure in three stages. After keeping the composites at room temperature for 15 days, the withdrawal strengths of nails and screws were measured according to BS Standard (CEN/TS 15534-1:2007) for dry composites. Withdrawal strengths were also measured after immersion of the composites for 24 h in distilled water (wet condition). The results showed that the withdrawal strength of screws is more than that of nails. Also, irrespective of the type of polymer, the percentage of rice straw fibre may significantly influence the withdrawal strength of fasteners, especially at the higher fibre to polymer ratios. Furthermore, it was found that in the wet condition the withdrawal strengths of the nail fasteners are reduced more (73.66%) than for the screws (28.9%).