Improvement of Thermal and Mechanical Properties of Vietnam Deproteinized Natural Rubber via Graft Copolymerization with Methyl Methacrylate

Abstract

In this study, we investigated the improvement of the thermal and mechanical properties of Vietnam deproteinized natural rubber (DPNR) via graft copolymerization of methyl methacrylate (MMA). The graft copolymerization was achieved successfully in latex stage using tert-butyl hydroperoxide (TBHPO) and tetra-ethylenepentamine (TEPA) as radical initiators at 30°C. By grafting with various MMA feeds and initiator concentration of 6.6×10−5 mol/g-rubber, the highest grafting efficiency and conversion were achieved at MMA of 15 wt.% per kg of rubber, 68% and 90%, respectively. The structure of grafted copolymers was characterized by 1H NMR, FTIR-ATR, and GPC, and thermal properties were investigated through DSC and TGA measurements. These showed that graft copolymers were more stable and rigid than DPNR. Storage modulus (G′) of graft copolymer was found to double that of DPNR, which contributed to the formation of graft copolymer. After sulfur vulcanization, the mechanical properties of DPNR-graft-PMMA, such as tensile strength, tear strength, and hardness, were improved significantly. Curing behaviors of the graft copolymers were found to be remarkably better than virgin DPNR.

Emulsion Polymerization of PMMA onto Natural Rubber

“…Based on Table , the maximum degradation temperatures of NR-PMMA DBP and NR-PMMA AIBN were 383 °C, higher than NR about 2 °C. This scenario indicated that the grafting of PMMA could improve the thermal resistance of NR due to the decreasing level of the reactive unsaturated backbone of the isoprene . The C–C single bond is more stable in contrast with C=C double bonds when it comes to thermal resistance.…”

“…However, the mixing of NR with PMMA is highly incompatible and immiscible due to the dissimilar polarity and hydrophilicity . Thus, the grafting technique is one of the well-liked approaches to ameliorate the compatibility of PMMA-NR copolymers …”

“…To date, different initiators have been used for graft copolymerization of vinyl monomers onto NR. Early work on this topic was performed using the bipolar redox initiator system [ tert -butyl hydroperoxide ( tert -BuHP)] and [tetraethylenepentamine (TEPA)] ,, or using cumene hydroperoxide (CHP) and TEPA. , Other studies examined the effect of different redox systems such as CHP/TEPA, tert -BuHP/TEPA, and potassium persulfate (K 2 S 2 O 8 )/sodium thiosulfate (Na 2 S 2 O 3 ). ,, To the best of our knowledge, none of the studies achieved a high grafting degree.…”

“…14 Thus, the grafting technique is one of the well-liked approaches to ameliorate the compatibility of PMMA-NR copolymers. 15 In this work, grafting of MMA onto NR via emulsion polymerization and RAFT in emulsion polymerization was utilized. Emulsion polymerization is well known for the production of ultrahigh-molecular-weight polymers in a short period of time, and the final product can be used directly.…”

Properties of Emulsion Paint with Modified Natural Rubber Latex/Polyvinyl Acetate Blend Binder

“…The oxidation process in the emulsion paint layer will not stop until the binder layer dries [17]. A suitable emulsion paint binder must also pay attention to the material's oxidation ability, chemical resistance, and mechanical properties [18]. Emulsion paint with a binder NRL-g-(MMA-co-St) has resistance to more extreme temperatures.…”