Effect of Deproteinized Natural Rubber to Vynil Monomer Ratio on Thermoplastic Natural Rubber Characteristics

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Chemical modification of natural rubber latex by emulsion graft copolymerization with thermoplastic monomer produces thermoplastic natural rubber (TPNR). Ratio composition of natural rubber to thermoplastic monomer determines the TPNR properties. TPNR has good mechanical properties of natural rubber and high processability of plastic material thus enhancing its application in industry. The research, which was conducted at research laboratory of Indonesian Rubber Research Institute, from June to December 2014, aimed to study the effect of the ratio of deproteinized natural rubber (DPNR) latex to vinyl monomer (VM: methyl methacrylate and styrene) on physical and mechanical properties of TPNR produced from batch graft copolymerization. Batch graft copolymerization was conducted at certain ratios of DPNR latex with methyl methacrylate and styrene (70:30; 60:40; and 50:50) at (65°C, 5 hours), and subsequently at (70°C, 1 hour). The result showed that batch technique tend to cause the formation of homopolymer vinyl which also affected the TPNR properties. Visually, the TPNR had white color, hard and brittle texture yet easier to process as shown by low time and energy consumption during compounding. The ratio of DPNR to VM at 70:30 was regarded as the optimum ratio for its balanced properties between elastomeric material of DPNR and thermoplastic material of VM.
Modifikasi kimiawi lateks karet alam secara kopolimerisasi cangkok emulsi dengan monomer termoplastik menghasilkan karet alam termoplastik (thermoplastic natural rubber = TPNR). Rasio komposisi karet alam terhadap monomer termoplastik menentukan sifat TPNR. TPNR memiliki perpaduan keunggulan sifat mekanik dari karet alam dan kemudahan pemrosesan dari material plastik sehingga dapat memperluas aplikasi karet alam di industri. Tujuan penelitian adalah mempelajari pengaruh rasio karet alam terdeproteinisasi (deproteinized natural rubber = DPNR) dengan monomer vinil (metil metakrilat dan stirena) terhadap karakteristik fisik-mekanik karet alam termoplastik melalui reaksi kopolimerisasi cangkok emulsi secara batch. Penelitian dilaksanakan di Laboratorium Pusat Penelitian Karet, Bogor, mulai bulan Juni sampai Desember 2014. Reaksi kopolimerisasi cangkok dijalankan pada berbagai rasio lateks DPNR terhadap metil metakrilat dan stirena (70:30; 60:40; dan 50:50) pada suhu (65oC; 5 jam), dilanjutkan suhu (70oC; 1 jam). Hasil penelitian menunjukkan teknik batch pada reaksi kopolimerisasi cangkok emulsi cenderung menyebabkan terbentuknya homopolimer vinil yang turut berpengaruh terhadap karakteristik TPNR. Secara visual, TPNR berwarna putih, bertekstur keras dan kaku, namun lebih mudah diolah karena memerlukan waktu dan energi pengkomponan yang rendah dibandingkan dengan karet alam yang tidak dimodifikasi. Rasio DPNR terhadap monomer vinil (MV) sebesar 70:30 dinilai optimum karena mampu menghasilkan TPNR yang memiliki kombinasi sifat elastomer dari DPNR dan termoplastik dari MV yang berimbang.Kata kunci: Karet alam, termoplastik, kopolimerisasi cangkok emulsi, vinil, batch 
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