A novel rigid sound-absorbing material made from used palm oil-based polyurethane foam (PUF) and water hyacinth fiber (WHF) composite was developed in this research. The NCO index was set at 100, while the WHF content was set at 1%wt with mesh sizes ranging from 80 to 20. The mechanical properties, the morphology, the flammability, and the sound absorption coefficient (SAC) of the PUF composite were all investigated. When the WHF size was reduced from 80 to 20, the compression strength of the PUF increased from 0.33 to 0.47 N/mm². Furthermore, the use of small fiber size resulted in a smaller pore size of the PUF composite and improved the sound absorption and flammability. A feasible sound-absorbing material was a PUF composite with a WHF mesh size of 80 and an SAC value of 0.92. As a result, PUF derived from both water hyacinth and used palm oil could be a promising green alternative material for sound-absorbing applications.

The novel natural rubber based cationic waterborne polyurethanes (cWPUs) with having quaternary amine as an emulsifier were successfully synthesized by additional polymerization. These polyurethanes were synthesized by the reaction of hydroxyl the method of telechelic natural rubber. Molecular weight approximately of hydroxyl telechelic natural rubber (HTNR) for 3000 g.mole^-1, toluene-2,4-diisocyanate (TDI), and N-methyl diethanol amine (NMDEA) (used as an emulsifier) were prepared for cWPU. The concentrations of NMDEA were examined in range of 0 – 2.0 moles. From the results under the isocyanate index of 100, the study revealed that cWPU with well-distributing had to consist of emulsion concentration more than 1.50 moles. Zetasizer nanorange was used to identify the prepared cWPU particle size distribution. The results showed that the particle size of cWPU was decreased from 86.6 to 78 nm with increasing of NMDEA concentration. The smallest particle size was 2 moles with non-acetic acid odor, and very soft film. In addition, cWPU would be well-dispersed more than 4 months. The ¹H NMR spectroscopy and FT-IR confirmed that the cWPU has been successfully synthesized from natural rubber.