Regulating the mechanical properties and microporous structures of hydroxypropyl methylcellulose based microporous photophobic films by adjusting the l-ethyl-3-methylimidazolium acetate content

Abstract X-ray diffraction, small angel X-ray scattering, scanning electron microscopy, moisture determination, dynamic mechanical analysis, whiteness assay and mechanical testing were used to study the effects of different doses of [EMIM]Ac on the microstructures and physical properties of HPMC/MSP film. By adjusting the 1-ethyl-3-methylimidazolium acetate ([EMIM]Ac) content (0 %–8 %), the mechanical properties and microstructures could be regulated. The elongation of the film increased from 5.91 % to 12.83 % with the increasing [EMIM]Ac content from 0% to 8% without affecting the tensile strength and modulus significantly. The average pore area decreased from 0.82 μm2 to 0.05 μm2 and the pore number increased with the increasing [EMIM]Ac content from 0% to 8%. Moreover, with the increasing [EMIM]Ac content, Tg decreased. 6% and 8% [EMIM]Ac decreased the compactness and smoothness of the fractal structure of the film greatly. [EMIM]Ac improved the ductility of HPMC/MSP film, which was mainly due to the decreased pore size and Tg. The improved photophobic films are both flexible and with easily changeable porous structure, which can be used as controllable packaging to carry and control-release different functional agents for different light sensitive foods.