Effect of annealing on morphologies and performances of hydroxypropyl methylcellulose/hydroxypropyl starch blends

Abstract

AbstractThe morphologies and performances of the blends of hydroxypropyl methylcellulose (HPMC), which is a thermal gel, and hydroxypropyl starch (HPS), which is a cooling gel, provides a scientific model to understand the relationship between the microstructure and performance of the unique thermal/cooling gel system. The films based on these blends have been developed for various applications, such as food packaging and medicine capsules, mainly for improving processibility. The morphologies and performance of the blends strongly depend on annealing or storage conditions and time since they are neither miscible nor compatible. This work focuses on the effects of storage conditions and time on the morphologies and performance of the blend films. It was found that the morphologies of the blend system depend on temperature, moisture, and annealing time. Correspondently, the gas permeability and mechanical properties of the film were also environmentally and time dependent. When HPS is continuous phase, the annealing results in starch recrystallization, which increases rigidity. When HPMC is the continuous phase, the materials showed less moisture sensitivity. Starch recrystallization and phase separation, which resulted in microcracks on the surface of the films, are the main reasons for the reduction in gas barrier and elongation. This work will study these issues using scanning electron microscope, X‐ray diffraction, mechanical testing and establish their relationship.