Effects of Alkaline Treatment on the Mechanical Properties of Costus Afer-LDPE Composite

The use of Bush cane (Costus afer) stem fibre as a filler in low density polyethylene (LDPE) matrix was studied at filler sizes (FS) of 150, 300, 600 and 2000 μm. The study utilized NaOH-treated and untreated samples obtained by melt-mixing to test for the mechanical properties of the composite. The composites were tested for tensile strength, flexural strength and hardness with respect to variations of component weight ratio and filler sizes. The study was carried out at 20 – 50% filler weight (FW) ratio. Tensile strength for the treated and untreated samples increased to maximum filler size at 18.52 and 15.93 N/m2 respectively. Percent enhancement of tensile strength in treated samples by filler size was 17.22% on average from 150 to 2000 μm and by filler weight on average was 20.4% from 20 – 50%. Experimental flexural strength increased with increase in filler size from 126.8 to 161.72 MPa for the treated samples and 125.33 to 132.49 MPa for the untreated samples at 150 and 2000 μm respectively. Calculated flexural strength increased from 650 MPa at 20 % FW and 150 FS to a maximum of 1768 MPa at 50% FW and 2000 FS for the treated samples, while that for the untreated samples was 531 MPa at 20% FW and 150 FS to 1323 MPa at 50% FW and 2000 μm FS. Calculated hardness decreased with filler size, while experimental hardness increased with filler size to a maximum. Treated composites showed better mechanical properties than the untreated indicating that the treatment or modification offers improvement of mechanical properties.