Fei Cheng

Structure and properties of urea-plasticized starch films with different urea contents

Films of thermoplastic starch (TPS) plasticized with different contents of urea were prepared by using a solution casting method. Scanning electron microscopy, X-ray diffraction and IR spectroscopy were used to characterize structures of the TPS films, respectively. Water vapor sorption isotherms and tensile properties of the films were determined. TPS films showed more smooth and transparent in appearance and less B-type crystallinity than the starch film without urea. The effect of urea content on the structure and behavior of the TPS film could be divided in three stages: (1) below urea 10% where urea interacted with starch via H-bonding and the films showed an antiplasticization effect, (2) from urea 10% to 30% where an apparent plasticization effect appeared on the starch because of free urea molecules as the effective plasticizer, and (3) a macroscopic phase separation occurred due to supersaturation of urea when urea content was more than 30%.

Effect of Hyperbranched Poly(trimellitic glyceride) with Different Molecular Weight on Starch Plasticization and Compatibility with Polyester

Hyperbranched poly(trimellitic glyceride) (PTG) plasticizers for starch were prepared by using trimellitic anhydride and glycerol as raw materials in a simple one-step synthesis. The structure and branching degree of PTGs were confirmed by Fourier transformed infrared, gel permeation chromatography and 1H nuclear magnetic resonance. The PTGs as plasticizers were composited with maize starch (S) via cooking and film formation. The structure and mechanical, thermal properties of the plasticized starch composites, and its adhesion to cotton and polyester yarns were studied in details. Results indicated that the PTG/S composites had better mechanical property and thermal stability, and lower moisture absorption than glycerol/starch (GLY/S) with the same content (w/w). With the increase in PTG molecular weight, elongation at break of PTG/S film decreased and tensile strength increased, and moisture absorption of PTGs/S reduced. In addition, PTGs/S had a better effect on adhesion to cotton and polyester yarns than GLY/S.

Preparation of triethylene glycol maleate and its effect on plasticization of oxidized starch

A plasticizer triethylene glycol maleate (TEG-MA) was synthesized. The dominated monoester of moderate hydrophobicity with apparent oil-water partition coefficient of 0.042 in the product was confirmed by acid value determination, HPLC and FTIR. Its plasticizing effect on oxidized starch was manifested by crystallization, aging behaviour, moisture absorption, and mechanical performance. X-ray diffraction data showed that the relative crystallinity of the plasticized starch decreased. Both the crystal and the crystallinity of starch films were rarely changed in aging. Moisture absorption relied on the ester content and relative humidity. The elongation at break increased significantly with plasticizer content more than 10% in the matrix.