Optimization Of Fiber Content And Alkali Treatment On Sound Damping Performances Of Kenaf Core/Unsaturated Polyester Composites

Kenaf core/unsaturated polyester (KC/UP) composites are prepared by mechanical stirrer followed by compression molding. Effect of fiber percentage as well as alkali treatment (NaOH concentration and immersion time) on sound damping performance are analyzed and optimized using three factors and three levels of Box-Behnken experimental design. Flexural properties, heat deflection temperature (HDT), density, lignin content, and morphology are investigated on selected samples. The results show that the optimum condition to produce KC/UP composites is predicted at 54.5% of fiber, 8.1% of NaOH used on alkali treatment, and 2 h fiber immersion on NaOH, giving 5.6% of sound damping/mm. Verifying the model results in 5.1% of sound damping/mm. Despite lower value of verification sample than predicted, this is still between 95% of predicting interval (4.1-7.1%), which is still higher than control sample (3.8%), suggesting model capability to predict the result. Further analysis on selected samples with the highest, mid and lowest sound damping property results in the change of flexural modulus at 38%, -9%, and 28%, respectively, and improvement in HDT (23%, 12%, and 22%). However, the flexural strengths of all selected samples are lower than that of control (-37%, -67%, and -44%). Morphology analysis shows that sample with 45% fiber content is more compact than 30% fiber content, which improves sound damping.