Main Article Content
A toughening agent from natural rubber grafted with poly (lactic acid) (PLA-g-NR) was prepared through melt grafting technique. The weight ratio of natural rubber (NR) to poly (lactic acid) (PLA) was 2 : 1, with di-tert-butyl peroxide (DTBP) as an initiator at 0–0.5 parts per hundred parts of rubber (phr). The structure of PLA-g-NR characterized by FTIR and 1H-NMR confirmed that PLA was successfully grafted onto NR. The rheological properties of PLA-g-NR were also different from those of the unreacted PLA-NR blend, indicating the presence of grafted structures. It was also found that this grafted PLA-g-NR possessed higher resistance to thermal degradation. The blending of the synthesized toughening agents with PLA at the content of 15 wt% revealed that the use of PLA-g-NR with 0.4 phr DTBP provided better dispersion of NR with a smaller rubber domain size than that in the unmodified PLA/NR blend. This indicated better phase compatibility between NR and PLA, which also resulted in an improvement in impact strength of the blend.
 Drumright, R.E., Gruber, P.R. and Henton, D.E., 2000, Polylactic acid technology, Adv. Mater. 12: 1841-1846.
 Sangeetha, V.H., Deka, H., Varghese, T.O. and Nayak, S.K., 2018, State of the art and future prospectives of poly (lactic acid) based blends and composites, Polym. Compos. 39: 81-101.
 Wan, Y., Chen, W., Yang, J., Bei, J. and Wang, S., 2003, Biodegradable poly (L-lactide)-poly (ethylene glycol) multiblock copolymer: Synthesis and evaluation of cell affinity, Biomaterials 24: 2195-2203.
 Ebadi-Dehaghani, H., Khonakdar, H.A., Barikani, M. and Jafari, S.H., 2015, Experimental and theoretical analyses of mechanical properties of PP/PLA/clay nanocomposites, Compos. Part B Eng. 69: 133-144.
 Sungsanit, K., Kao, N. and Bhattacharya, S.N., 2012, Properties of linear poly (lactic acid)/polyethylene glycol blends, Polym. Eng. Sci. 52: 108-116.
 Ishida, S., Nagasaki, R., Chino, K., Dong, T. and Inoue, Y., 2009, Toughening of poly (L-lactide) by melt blending with rubbers, J. Appl. Polym. Sci. 113: 558-566.
 Xiong, Z., Yang, Y., Feng, J., Zhang, X., Zhang, C., Tang, Z. and Zhu, J., 2013, Preparation and characterization of poly (lactic acid)/starch composites toughened with epoxidized soybean oil, Carbohydr. Polym. 92: 810-816.
 Chee, W.K., Ibrahim, N.A., Zainuddin, N., Rahman, A.F.M. and Chieng, B.W., 2013, Impact toughness and ductility enhancement of biodegradable poly (lactic acid)/poly (ε-caprolactone) blends via addition of glycidyl methacrylate, Adv. Mater. Sci. Eng. 2013(4).
 Zhang, X. and Zhang, Y., 2016, Reinforcement effect of poly (butylene succinate) (PBS)-grafted cellulose nanocrystal on toughened PBS/polylactic acid blends, Carbohydr. Polym. 140: 374-382.
 Sirisinha, K. and Somboon, W., 2012, Melt characteristics, mechanical, and thermal properties of blown film from modified blends of poly (butylene adipate-co-terephthalate) and poly (lactide), J. Appl. Polym. Sci. 124: 4986-4992.
 Bitinis, N., Verdejo, R., Cassagnau, P. and Lopez-Manchado, M.A., 2011, Structure and properties of polylactide/natural rubber blends, Mater. Chem. Phys. 129: 823-831.
 Jaratrotkamjorn, R., Khaokong, C. and Tanrattanakul, V., 2012, Toughness enhancement of poly (lactic acid) by melt blending with natural rubber, J. Appl. Polym. Sci. 124: 5027-5036.
 Zhang, C., Huang, Y., Luo, C., Jiang, L. and Dan, Y., 2013, Enhanced ductility of polylactide materials: Reactive blending with pre-hot sheared natural rubber, J. Polym. Res. 20: 121/1-121/9.
 Pattamaprom, C., Chareonsalung, W., Teerawattananon, C., Ausopron, S., Prachayawasin, P. and van Puyvelde, P., 2016, Improvement in impact resistance of polylactic acid by masticated and compatibilized natural rubber, Iran. Polym. J. 25: 169-178.
 Kaeophimmueang, N., 2015, The Dynamic Vulcanization of Natural Rubber in the PLA/NR Blends, Master Thesis, Thammasat University, Pathum Thani, 118 p.
 Abdullah Sani, N.S., Arsad, A., Rahmat, A. R. and Mohammad, N.N.B., 2015, Effects of compatibilizer on thermal and mechanical properties of PLA/NR blends, Mater. Sci. Forum. 819: 241-245.
 Zhang, C., Man, C., Pan, Y., Wang, W., Jiang, L. and Dan, Y., 2011, Toughening of polylactide with natural rubber grafted with poly (butyl acrylate), Polym. Int. 60: 1548-1555.
 Juntuek, P., Ruksakulpiwat, C., Chumsam rong, P. and Ruksakulpiwat, Y., 2012, Effect of glycidyl methacrylate-grafted natural rubber on physical properties of polylactic acid and natural rubber blends, J. Appl. Polym. Sci. 125: 745-754.
 Chumeka, W., Tanrattanakul, V., Pilard, J. F. and Pasetto, P., 2013, Effect of poly (vinyl acetate) on mechanical properties and characteristics of poly (lactic acid)/natural rubber blends, J. Polym. Environ. 21: 450-460.
 Pongsathit, S. and Pattamaprom, C., 2018, Irradiation grafting of natural rubber latex with maleic anhydride and its compatibili zation of poly (lactic acid)/natural rubber blends, Radiat. Phys. Chem. 144: 13-20.
 Thepthawat, A. and Srikulkit, K., 2014, Improving the properties of polylactic acid by blending with low molecular weight polylactic acid-g-natural rubber, Polym. Eng. Sci. 54: 2770-2776.
 Sookprasert, P. and Hinchiranan, N., 2017, Morphology, mechanical and thermal properties of poly (lactic acid) (PLA)/natural rubber (NR) blends compatibilized by NR-graft-PLA, J. Mater. Res. 32: 788-800.
 Wongngam, Y. and Pattamaprom, C., 2018, Synthesis of PLA-grafted natural rubber by reactive melt-blending technique for impact modification of PLA, Thai Sci. Technol. J. 26: 866-879.
 Wongngam, Y., 2016, Synthesis of PLA-Grafted Natural Rubber by Reactive Melt-Blending Technique for Impact Modifica tion of PLA, Master Thesis, Thammasat University, Pathum Thani, 129 p. (in Thai)
 Huang, Y., Zhang, C., Pan, Y., Wang, W., Jiang, L. and Dan, Y., 2013, Study on the effect of dicumyl peroxide on structure and properties of poly (lactic acid)/natural rubber blend, J. Polym. Environ. 21: 375-387.
 Abdelwahab, M.A., Flynn, A., Chiou, B.S., Imam, S., Orts, W. and Chiellini, E, 2012, Thermal, mechanical and morphological characterization of plasticized PLA-PHB blends, Polym. Degrad. Stabil. 97: 1822-1828.
 Kurokawa, N. and Hotta, A., 2018, Thermomechanical properties of highly transparent self-reinforced polylactide composites with electrospun stereocom plex polylactide nanofibers, Polymer 153: 214-222.