Malaysian Journal of Analytical Sciences Vol 18 No 2 (2014): 405 – 414

 

 

 

EFFECT OF REAGENTS CONCENTRATION AND RATIO ON DEGRADATION OF NATURAL RUBBER LATEX IN ACIDIC MEDIUM

 

(Kesan Kepekatan dan Nisbah Reagen ke Atas Pendegradasian Lateks Getah Asli dalam Media Berasid)

 

Suhawati Ibrahim^*, Asrul Mustafa

 

Fine Chemicals and Biomaterials Programme,

 Bahagian Teknologi dan Kejuruteraan,

Lembaga Getah Malaysia, 47000 Sungai Buloh, Selangor, Malaysia

 

*Corresponding author: suhawati@lgm.gov.my

 

 

Abstract

The molecular weight of natural rubber (NR) was reduced via degradation to liquid natural rubber (LNR) using hydrogen peroxide and sodium nitrite as reagents in latex solution. In this study, the reaction was carried out in an acidic medium at 70^oC at various ratio and concentration of reagents. Results showed that the properties of degraded product i.e. LNR depends on the concentration and ratio of the reagents added into reaction mixtures. Increasing the concentration of hydrogen peroxide and sodium nitrite as reagents at 1 to 1 ratio efficiently reduced the molecular weight of LNR, but the gel content increased when reagents were added more than 0.2 mol. Hydrogen peroxide was found to have greater effect on degradation reaction compared to sodium nitrite when excessive amount of hydrogen peroxide showed further reduction in molecular weight of LNR. The degradation reaction also resulted in the formation of certain functional groups such as hydroxyl and carbonyl as shown from spectroscopy microstructure analysis.

 

Keywords: Liquid natural rubber (LNR), OH radical, redox reaction

 

Abstrak

Berat molekul getah asli (NR) telah diturunkan secara pendegradasian kepada getah asli cecair (LNR) menggunakan hidrogen peroksida dan natrium nitrit sebagai reagen-reagen dalam lateks. Dalam kajian ini, tindak balas dilakukan dalam media berasid pada suhu 70^oC pada nisbah dan kepekatan reagen yang berbeza. Keputusan menunjukkan bahawa sifat hasil pendegradasian iaitu LNR bergantung kepada kepekatan dan nisbah reagen yang digunakan semasa tindak balas. Penambahan kepekatan reagen pada nisbah 1:1 menurunkan berat molekul LNR dengan berkesan, tetapi kandungan gel meningkat bila kepekatan reagen lebih dari 0.2 mol digunakan. Hidrogen peroksida didapati memberikan pengaruh yang lebih besar ke atas tindak balas pendegradasian berbanding natrium nitrit bila berat molekul LNR terus menunjukkan penurunan bila jumlah berlebihan digunakan. Tindak balas pendegradasian juga menghasilkan kumpulan berfungsi yang tertentu seperti hidroksi dan karbonil seperti ditunjukkan dari analisa spektroskopi.

 

Kata kunci: Getah asli cecair (LNR), radikal OH, tindak balas redoks

 

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