8342937117

Pertanika 14(1). 65-67 (1991)

Determination of Dry Rubber Content (DRC) of Hevea Rubber Latex

by Microwave Drying

KAI DA BIN KHAUD

Department oj Physics

Family of Science and Enuiron men tal Studies Uniuersiti Pertanian Malaysia 43400 UPM, Selangor Darni Ehsan, Malaysia.

Key words: Microwave drying; Hevea rubber latex, Dry Rubber Content (DRC).

ABSTRAK

Kaedahpiawai bagi menentukan kandungangetahkering(KGK) adalah melibalkanpengeńngan kepingangetah. beku dałam ketuhar biasa padasuhu 70°C selama 12 jam. Prosedurpengeńngan yanglama ini boleli digantikan dengan pengeńngan mikrogelombangyanglebih cepat, seragamdanpada kejitua n yang setara. Dałam kertas iniprestasi teknik ini akan ditunjukkan menerusi aspek kesan ku asa mikrogelombang dan jisim awal latex ke atas jumlah masa pengeńngan. Menggunakan kaedah beban air bagi menentukan paras tenaga mikrogelombang, masa pengeńngan optimum bagi jisim awal tertentu adalah dicadangkan. Keputusan ekspeńmen menunjukkan bahawa jumlah masa pengeńngan untuk sampel berjisim awal 10gpada paras kuasa 743 u/att adalah kurangdańpada 10 minii. Tidak banyak perbezaan bagi jumlah masa pengeńngan untuk sampel bagi jisim awal antara 5 - 30 g.

ABSTRACT

l'he standard method for DRC determination involves drying oj the sheeted coagulum in a corwentional oven at 70°C forabout 12 hours. This lengthy drying procedurę can be replaced by microwaue drying which is fast_y uniform and with comparable accuracy. In this paper the perfonnance oj this technu/ue will be shoum particulary the effect of microwave power and initial mass of the latex to the finał drying limę. By using the water load technique for microwaue power leuel determination, the optimum drying time is proposed for a specific mass oflatex. The expeńmental results show that the finał drying time jor 10 gof initial mass offresh latex and at a power leuel of about 743 watt is less tłum 10 minutes. There is not much difference in finał drying time for samples with initial mass between 5-30g.

INTRODUCTION

I he standard method for the determination of DRC of latex is based on the British Standard (1972). Bricfly, the method involves acid coagulation ofa known weightof latcx and heating over a steam bath umil a elear serum is obtained. I he coagulum is thoroughly washed and placed in an oven at 70°C overnight before reweighing. The method gives good reproducibility of results and is accurate. This technique, however, is not suitable for field use as the test results can not be obtained on thedayof operation.Therefore transaction with the tapper can not be madę on the day of tapping.

A possible way to solve this problem is by reducing the time of drying by using a microwave oven. I he use of microwave power for total solid

Key to author’s name : K.B. Khalid content (TSC) ol Hevea rubber latex, bas been successfully carried out (Khalid et al. 1988). The experimental results showed that the finał drying time for 5 to 15 g !atex with a TSC of 39.2% was approximately 4 minutes.

In this paper the impact of microwave drying on sheeted coagulum is studied including the effect of level of microwave power and initial mass of the latex. Optimization in the efficiency of the drying process is also discussed.

MATERIALS AND METHODS

The fresh I levea latex used in the investigation was obtained from the university farm (RRIM - 600 clone).

Microwave drying was carried out in a Sharp Model R 8580 inicrowave oven, operating at a fre-