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

Thi Nhan Nguyen,Thu Ha Nguyen,Thuy Tran Thi,Nam Nguyen Van,Dung Tran Anh,Tung Nguyen Huy,Tung Tran Quang,Thuong Nghiem Thi,Hieu Nguyen Duy

doi:10.1155/2020/9037827

Thi Nhan Nguyen, Thu Ha Nguyen + Show 7 more

Open Access

https://doi.org/10.1155/2020/9037827

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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.

Highlights

In recent years, environmental issues have become more important
Thermal and mechanical properties of natural rubber are very important for its applications, since Natural rubber (NR) products are often exposed under real environmental conditions, including sunlight, UV irradiation, and high temperature
Hardness testing machines TFCLOCKGS 709 N (Japan) were used to measure the hardness of deproteinized natural rubber (DPNR) and DPNR-graft-PMMA according to ASTM D2240-15

Summary

Introduction

Environmental issues have become more important. As a result, the use and development of renewable materials as natural polymers are becoming a new trend in society. The recent rise of the global NR consumption has encouraged Vietnam as the main NR producing country to expand its expertise with rubber trees into a multipurpose crop for the national economic development This will improve the social conditions of rural areas and lead to regreening bare land towards environmental protection. Thermal and mechanical properties of natural rubber are very important for its applications, since NR products are often exposed under real environmental conditions, including sunlight, UV irradiation, and high temperature. Chemical modification of NR using MMA through graft copolymerization is promising for improving the mechanical and thermal properties of NR. Graft copolymerization of MMA onto Vietnam DPNR has been studied to obtain high conversion and high grafting efficiency using TBHPO-TEPA as radical initiators at room temperature. The grafted NR was afterward vulcanized with sulfur in order to examine the curing and mechanical properties of this copolymer as a commercial material

Chemicals

Results and Discussion

Conclusions