Electron-beam processing of destructurized allylurea-starch blends: Immobilization of plasticizer by grafting

• Published in: Journal of applied polymer science Vol. 73; no. 3; pp. 409 - 417
• Main Authors: Ruckert, Danielle, Cazaux, Frédéric, Coqueret, Xavier
• Format: Journal Article
• Language: English
• Published: New York John Wiley & Sons, Inc 18.07.1999; Wiley
• Subjects: allylurea; Applied sciences; EB grafting; Exact sciences and technology; Grafting and modifications; Physicochemistry of polymers; Polymers and radiations; starch; starch grafting; starch plasticization; Thermoplastics; Electron beam; Immobilization; Experimental study; Property processing relationship; Allylic compound; Chemical coupling; Radiation dose; Chemical modification; Humidity effect; Plasticizer; Dynamic mechanical properties; Potato starch; Radiochemical reaction; Ureas; Starch derivative
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/(SICI)1097-4628(19990718)73:3<409::AID-APP12>3.0.CO;2-Z

Allylurea (AU) was used as a reactive additive with poor aptitude to homopolymerization for obtaining grafted plasticized starch films with stabilized physical properties. Potato starch was mixed with AU (30–50 parts per hundred/pph) in a mixer operating at 125°C. Upon storage in well‐defined hygrothermal conditions, the resulting thermoplastic material shows strong plasticizer migration revealed by AU crystals blooming at the samples surface and exhibits strong opacity assigned to phase separation of the organic additive inside the material. Freshly prepared thermoplastic films of appropriate thickness were exposed to a 175‐kV electron beam (EB) radiation for inducing covalent grafting of AU by a free radical process. FTIR monitoring of the resulting chemical changes in thin films of AU–starch blends indicates unambiguously the transformation of AU allylic bond. High irradiation doses are required for achieving complete conversion of AU in the blend. However, no detectable AU migration was observed for intermediate AU conversion, probably as a consequence of higher plasticizer solubility in the grafted polysaccharide. Examination of the viscoelastic properties by dynamic mechanical thermal analysis shows that artificial aging by placing the films alternatively in high and low relative humidity (RH) atmosphere does not significantly alter the thermomechanical spectrum of the material reconditioned in a cell at 58% RH. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 409–417, 1999