Aging properties and hydrophilicity of maize starch plasticized by hyperbranched poly(citrate glyceride)

Abstract

Hyperbranched poly(citrate glyceride)s (HBPETs) as plasticizers were mixed with maize starch (S) via cooking and film formation. The structure, aging properties, and hydrophilicity of the plasticized starches were studied by means of Fourier transform infrared spectroscopy, X‐ray diffraction, tension testing, contact angle testing, solubility measurements, moisture absorption, and water vapor permeability (WVP). Compared with a glycerol–S plasticized film, the HBPET–S composite films had better mechanical properties in terms of both strength and elongation at break, better aging resistance, less moisture absorption, less WVP, and more hydrophobicity on the film surface. The mechanisms behind the performances resulted from stronger and more stable H bonds between the abundant active end groups of HBPET and hydroxyls of starch and the high branching degree of the HBPETs; this was helpful for effectively inhibiting the recrystallization of starch. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46899.

Effect of hyperbranched poly(citric polyethylene glycol) with various polyethylene glycol chain lengths on starch plasticization and retrogradation

“…The water peak in the PCPEG/MS spectra is weaker than that in the PEG/MS spectra. This might be due to the stronger combination of PCPEG with starch than that of PEG with starch, which could shield the hydrophilic hydroxyl groups of starch away from water …”

“…XRD patterns of MS, CA/MS, PEG/MS and PCPEG/MS films stored for 3 and 45 days were recorded with a Philips X' Pert Pro MPD system (Netherlands) using a scanning range of 2 θ from 5° to 40° with a step of 0.03°. The crystallinities of starch films were calculated according to our previous report …”

“…In addition, HBPET has better compatibility with resins or starch and resistance to migration in a polymer matrix than small polar molecules . Our group found that hyperbranched poly(citrate glyceride) not only had good plasticizing effect and resistance to migration in starch, but also could inhibit the moisture absorption of starch …”

“…An ideal plasticizer should reduce the intermolecular forces and recrystallization of starch, increase the mobility of starch chains, decrease the moisture absorption and be compatible with starch . So far, the most used starch plasticizers are small molecules with polar groups, such as OH, COOH and NH 2 , which tend to migrate and aggregate in starch materials, leading to starch retrogradation after several days of storage …”

“…In our previous study, several kinds of CHP were proved to be good plasticizers of starch, but the mechanism remains unknown . The random structure and low functional group accessibility of CHPs lead to great difficulty in the structure–performance study of hyperbranched polymer plasticizers.…”