International Conference on Agriculture, Chemical And Environmental Sciences 2012, Dubai, United Arab Emirates. Abstract— In this study, polylactic acid (PLA) was melt blended with polypropylene (PP) and liquid natural rubber (LNR) with the ratio of PLA/PP (90/10) and PLA/PP/LNR (90/10/10) in the Haake Rheomix internal mixer. The mechanical properties of such as stress- strain, flexural and impact were studied. It was found that the elongation at break, flexural and notched impact strength increased significantly for the LNR compatibilized PLA/PP blend. The DSC and FTIR showed the PLA/PP and PLA/PP/LNR were not miscible. Keywords—PLA, PP, blend, liquid natural rubber. I. INTRODUCTION olylactic acid (PLA) is gaining popularity due to its biodegradable, renewability and comparable properties with petroleum-based polymers. One of the major concerns of using non-biodegradable polymer is disposal after end the product life cycle. The emergence of biodegradable plastics promises an alternative solution for this disposal problem. PLA possesses the tensile strength and stiffness similar to polyethylene terephtalate and processing characteristics of polystyrene, but it suffers low impact resistance. The poor toughness limits its use in the applications that need plastic deformation at higher stress level [1]. Blends of PLA with other polymer is the most attractive and practical route towards modifying its physical properties. Polypropylene (PP) is an excellent polymer with a combination of outstanding physical, chemical, mechanical, thermal and electrical properties. It was therefore not surprising that PP has been blended with other polymers such as polyethylene (PE) and natural rubber (NR) for physical property modification. This work reports the melt blend of PLA/PP and PLA/PP with liquid natural rubber (LNR) compatibilizer. II. MATERIALS AND METHOD Polylactic acid of Natureworks Ingeo TM Biopolymer 2002D grade supplied by Unic Technology Ltd, China was a thermoplastic resin used in this study. It has a density of 1.24 g/cm 3 and melt flow index of 5-7 g / 10 min. (190°C / 2.16 kg) and melting temperature between 160-170 o C. As for the PP, an Mohd Bijarimi is with the 1 Universiti Malaysia Pahang, Kuantan Pahang Malaysia, (corresponding author phone:6095492918 ; fax: 6095492889 ; e-mail: bijarimi@ump.edu.my). Sahrim Ahmad & Rozaidi Rasid are with 2 Universiti Kebangsaan Malaysia, Bangi, Malaysia. (e-mail; sharim@ukm.my, rozaidi@ukm.my) injection molding grade with a melt flow index of 7.5 g / 10 min was used. Natural rubber of SMR L type with a density of 0.91 g/cm 3 was a product from Malaysia Rubber Board. Liquid natural rubber (LNR) was synthesized using a photochemical oxidation technique on SMR L in our laboratory [2, 3]. Other chemicals were used as received. All melt blends prepared in a laboratory mixer (Haake Rheomix 600p) at 180 o C with a capacity of 60 g. Blending was carried out with a rotor speed of 50 rpm for 15 min. The PLA was initially melted for 120 s and subsequently LNR (if applicable) and PP were incorporated after 20 seconds. The blend was removed from the internal mixer and then molded at 180 o C under 45MPa of pressure for 13 minutes using a hot press into thin sample sheets (150 mm x 150 mm) for test specimens. All compositions of blend were tested and compared in terms of their mechanical properties. Tensile test was carried out according to ASTM D638 using a Testometric under ambient conditions with crosshead speeds of 50 mm min -1 . The flexural strength and modulus were also measured on the same tensile machine according to ASTM D790 with a 3mm/min strain rate. The Izod impact properties of the blends were determined by the Ray-Ran Impact tester on notched specimens. The glass transition temperature (T g ) and melting temperature (T m ) of the blend components were characterized with a Mettler Toledo DSC 822 on compression molded specimens. As for thermal stability of PLA and blends, a Mettler Toledo TGA/SDTA 851 apparatus was used. The chemical changes after blending were monitored by FT-IR spectroscopy. The IR spectra were recorded using a Shimadzu 8400 M FT-IR spectrometer with 4 cm −1 resolution and 10 scans. All spectra were recorded in the absorbance mode in the 3500–600 cm −1 region. III. RESULTS AND DISCUSSION A. Mechanical Properties The tensile properties of the PLA matrix and PLA/PP blends are shown in the Table 1. It is shown that the neat PLA with tensile strength of 69.91 MPa, Young’s modulus of 1968 MPa and elongation at break at 3.8%. In general, the incorporation of PP has reduced the tensile strength and Young’s modulus of the PLA matrix but with improved elongation at break. This can be explained by incompatibility of PP and PLA due to the difference in polarity. However, in the LNR compatibilized system, i.e. PLA/PP/LNR (90/10/10), the Young’s modulus is comparable to PLA/PP (90/10) Mechanical, Thermal and Morphological Properties of PLA/PP Melt Blends Mohd Bijarimi 1,2 , Sahrim Ahmad 2 , Rozaidi Rasid 2 P