Fig. 12 and 13 show the effects of the rice hull content on the texture, the visual appearance and the coloration of the rice hull filled PVC at 250 μm. As indicated in Fig. 12, it was evident that the color of the composites changed from light to dark brown as the rice hull content increased. The whiteness L* was lowered with the increase in the contents of the milled rice hull filler from 98.86 observed in the unfilled PVC to 57.43 observed in the PVC filled with 80 phr of rice hull particles. In terms of the redness, the value of a* increased with increasing the rice hull content.
5 Conclusion
Rice hull is an effective filler for PVC/rice hull WPC in terms of mechanical properties and visual appearances. The impact strength of the composites increases with the rice hull particle size and decreases as the rice hull loading increases. The particle size of the milled rice hull has a slight effect on the modulus of the PVC/rice hull WPC, but they rise rapidly with the content of the hard, stiff and silica-rich rice hull filler. However, both the modulus and the strength of the PVC filled with high content of milled rice hull at 80 phr drop due to the formation of agglomerations of rice hull and cavities formed at the PVC-rice hull interface. The smaller particles of the milled rice hull tend to act as the pigment to form a darker shade composite close to the color of the rice hull’s filled within the WPC. The milled rice hull particles with average sizes 106 μm and beyond are simply embedded in the white PVC matrix.
Acknowledgments
The authors acknowledge the partial research funding provided by the 90th Year Anniversary of chulalongkorn University (Ratchadaphiseksomphot) Endowment fund. Generous provision of processing facilities at Nawaplastic Industries Company Limited is greatly appreciated. Thanks are extended to the Center of Excellent in Particle Technology and Dr. Sujinda Jitjaicham, from the faculty of Agricultural Product Innovation and Technology, Srinakharinwirot University for facilitating the grinding equipment and the color meter respectively