D. Trimnell et al., GRAFT-POLYMERIZATION OF METHYL ACRYLATE ONTO GRANULAR STARCH - COMPARISON OF THE FE+2 H2O2 AND CERIC INITIATING SYSTEMS/, Journal of applied polymer science, 60(3), 1996, pp. 285-292
Graft polymerizations of methyl acrylate (MA) onto granular cornstarch
were carried out in water with both ferrous ammonium sulfate/hydrogen
peroxide (FAS/H2O2) and eerie ammonium nitrate (CAN) initiation. Star
ch concentrations were 10, 20, and 30% in water, and the amount of MA
used was either 0.5, 1, or 2 mol per AGU of starch. Two concentrations
of FAS/H2O2 were used: 1 mol each of FAS and H2O2 per 100 AGU of star
ch, and 1 mol per 1000 AGU. Significant amounts of acetone-extractable
PMA homopolymer were produced, and homopolymer formation was especial
ly high at the 1 : 100 ratio. Sharp exotherms were observed, and react
ion mixtures reached maximum temperature within 2 min or less. Total c
onversions of MA to PMA were higher at the 1 : 100 ratio, and conversi
ons in some polymerizations were nearly quantitative. CAN-initiated po
lymerizations were run under the same conditions used for FAS/H2O2; ho
wever, the amount of CAN used was limited to 1 mol per 100 AGU because
of low conversions at the 1 : 1000 ratio. Compared with FAS/H2O2, CAN
gave more moderate exotherms; and longer time periods were required f
or reaction mixtures to reach maximum temperature. CAN gave quantitati
ve conversions of MA to PMA, but only low percentages of PMA homopolym
er were observed. Differences between FAS/H2O2 and CAN initiation are
consistent with differences in the two initiation mechanisms. High lev
els of homopolymer produced on starch granule surfaces with FAS/H2O2 c
ould be seen in scanning electron micrographs and were also apparent i
n infrared spectra obtained with an attenuated total reflectance (ATR)
cell. ATR spectra of acetone-extracted products indicated that the am
ount of PMA actually grafted to starch granule surfaces was similar wi
th both initiating systems. Tensile properties of extruded ribbons pre
pared from these polymers did not vary greatly with the initiator used
. (C) 1996 John Wiley & Sons, Inc.(dagger)