Polyacrylonitrile distribution in grafted starch granules determined by scanning electron microscopy
1973
Fanta, G.F. | Baker, F.L. | Burr, R.C. | Doane, W.M. | Russell, C.R.
The location of polyacrylonitrile (PAN) within the starch granule matrix was determined for two wheat starch-PAN graft copolymers which contained 22 % and 44 % grafted PAN. Granules of graft copolymer (which closely resembled ungrafted starch in appearance) were fractured by ballmilling. The milled copolymer was then heated under reflux in dilute hydrochloric acid to remove the starch moiety, and the fracture surfaces in the remaining PAN (which was inert to these conditions) were examined with a scanning electron microscope. Areas in the grafted granules which contained little or no PAN thus appeared as voids in the fracture surfaces. Micrographs suggested that granules of low add-on graft copolymer were largely surface grafted. In the higher add-on product, grafting had taken place throughout most of the granule interior; however, small areas in the centers of some granules still contained little or no PAN.
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