Citation
Rusli, Rafeadah
(2001)
Graft Copolymerisation of 2-Hydroxyethyl Methacrylate onto Sago Starch.
Masters thesis, Universiti Putra Malaysia.
Abstract
Studies on the preparation of 2-hydroxyethyl methacrylate (HEMA) grafted sago
starch were conducted using eerie ammonium nitrate (CAN) and potassium
persulphate (PPS) as the free radical initiators under a nitrogen atmosphere. The effect
of various parameters on the grafting process was determined. The optimum
conditions obtained for the grafting of HEMA onto sago starch using CAN as the
initiator were as follows: reaction period, 3 h; reaction temperature, 40°C; I-IEMA
amount, 0.17 mol and CAN amount, 1.0 x 10-3 mol. Meanwhile the optimum
conditions for the copolymer preparation using PPS as the initiator were as follows;
reaction period, 2 h; temperature, 40°C; amount of PPS, 5.0 x 10-3 mol and amount of
HEMA, 0.05 mol. The percentage of grafting and grafting efficiency under optimum
conditions for CAN initiation were 200% and 46%, respectively whereas for PPS
initiation were 406% and 63%, respectively. Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA)
and scanning electron microscopy (S12M) were used to characterise the graft
copolymer. The infrared spectra of grafted copolymer in contrast to starch showed an
additional peak at 1726 cm-l, indicating the presence of ester carbonyl of the
monomer. TGA studies revealed that the decomposition temperatures of starch were
different from poly(HEMA) grafted sago starch. SEM studies indicated that HEMA
was homogeneously grafted onto starch. The biodegradability study by using aamylase
revealed that the hydrolysis rate of the polysaccharide chains by a-amylase
was strongly dependent on the percentage of grafting where the hydrolysis rate
increased with the decrease in percentage of grafting. The highest hydrolysis rate was
obtained by using 50 ppm of a-amylase concentration. The swelling behaviour of
poly(HEMA) grafted sago starch in water and salt ions showed that the percentage of
swelling at equilibrium increased as the percentage of grafting increased. The
percentage of swelling at equilibrium and the swelling rate coefficient decreased in the
order of water> NaCI > KCI > MgCh > CaCho The water diffusion of the grafted
polymer in water and cationic salt solutions was a Fickian character. The study of
metal chelating properties indicated that Cibacron Blue-attached grafted polymer
particles have higher affinity towards Cd(II) and Pb(II) as compared to Fe(III) and
CU(ll). The dye-attached grafted polymer also showed high affinity for these metal
ions between pH 4 and 7.
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