Rubber toughened poly(lactic acid) (PLA) was prepared by blending with natural rubber (NR)-based polymers. The blends contained 10 wt % of rubber and melt blended with a twin screw extruder. Enhancement of impact strength of PLA was primarily concernced. This study was focused on the effect of rubber polarity, rubber viscosity and molecular weight on mechanical properties of the blends. Three types of rubbers were used: NR, epoxidized natural rubber (ENR25 and ENR50), and natural rubber grafted with poly(methyl methacrylate) (NR-g-PMMA). Effect of viscosity and molecular weight of NR, rubber mastication with a two-roll mill was investigated.It was found that all blends showed higher impact strength than PLA and NR became the best toughening agent. Viscosity and molecular weight of NR decreased with increasing number of mastication. Impact strength of PLA/NR blends increased after applying NR mastication due to appropriate particle size. DMTA and DSC characterization were determined as well.

Linear and crosslinked polyhydroxyurethanes (PHUs) based on natural rubber (NR) were synthesized by a polyaddition reaction without a solvent or catalyst to exploit the reactivity of diamines or triamines with dicyclic carbonate groups. Oligoisoprenes were obtained from the controlled oxidative degradation of NR and successive modifications of the chain ends. The syntheses of linear PHU were carried out with two approaches. The first one consisted of a reaction between amino telechelic oligoisoprenes and aromatic or aliphatic dicyclic carbonates. The second approach proceeded through a reaction between oligo-isoprenes bearing cyclic carbonate chain ends and difunctional or trifunctional amines. The evolution of these reactions was studied by Fourier transform infrared spectrometry. The influence of the carbonate-to-amine molar ratio, the chain length of the oligo-isoprenes, and the reaction temperatures were investigated. The thermal properties of the PHUs were studied by differential scanning calorimetry and thermogravimetric analysis.

As environment friendly polymers are required to reduce the green‐house gas emissions and global warming, bio‐based polyurethane foam (PUF) is attracting interest from the industrial sector and researchers. Bio‐based polyols for PUF have been synthesized from various renewable resources, mostly plant oils. The present study explored a novel bio‐based PUF produced from a mixture of bio‐based polyols synthesized from palm oil and natural rubber. Palm oil‐based polyol (POP) was synthesized via an epoxidation reaction of double bonds of palm oil followed by complete oxirane ring‐opening. Hydroxy telechelic natural rubber (HTNR) was synthesized by oxidative degradation using periodic acid and sodium borohydride. For comparison, two diisocyanates were used: toluene‐2,4‐diisocyanate and polymeric methylene diphenyl diisocyanate. POP and HTNR were miscible and all PUFs showed polyhedral semi‐closed cells and hardness was in the flexible foam range. One possible application of the novel PUF could be thermal insulation.

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Natural rubber (NR) grafted with poly(vinyl propionate) (NR‐g‐PVP) was prepared by emulsion polymerization. The monomer content was set at 5, 10, 20, and 30 wt%. The chemical structure of NR‐g‐PVP was confirmed by 1H‐NMR and FTIR techniques. The grafting parameters of purified NR‐g‐PVP were evaluated. Binary (PLA/NR and PLA/NR‐g‐PVP) and ternary (PLA/NR/NR‐g‐PVP) blends were prepared by melt blending using a twin‐screw extruder. The percentage of grafted PVP on NR affected morphology, thermal and mechanical properties of the blends. In binary blends, 5% grafting showed the greatest improvement of toughness and ductility with PLA, whereas there was no improvement in the mechanical properties of PLA/NR blend from using NR‐g‐PVP as a compatibilizer. The mechanical properties of the blends are related to mutual compatibility of the components. Good interfacial adhesion and proper particle size of NR were the key factors contributing to mechanical properties.