Improved hydroxypropyl methylcellulose films through incorporation of amylose-N-1-hexadecylammonium chloride inclusion complexes

In order to replace petroleum based films used in food packaging, improved biobased options are needed. Hydroxypropyl methylcellulose (HPMC) has value, but in terms of oxygen and water vapor permeability it is deficient. Blended films were produced using HPMC and amylose-N-1-hexadecylammonium chloride inclusion complex (HexAM) that required no plasticizer. The resulting blended films were clear, had little color and had increased product value relative to the control. With the addition of the HexAM, the crystallinity of the film increased as seen by x-ray diffraction spectra. By SEM the surfaces of the films were relatively smooth by scanning electron microscopy. However, atomic force microscopy demonstrated that the control films were smoother (roughness 1.2 nm rms), relative to the 50 % HexAM blend films (roughness 29.9 nm rms). In the infrared spectra (IR) certain peaks, such as the hydrated water and glycosidic bond peaks, either increased or decreased in a liner fashion with incorporation of HexAM. Using microscopic IR, it was shown that the surfaces of the films were chemically homogeneous on a 1.56 µm scale. Tensile strength and elongation decreased slightly with increasing HexAM. However, increasing the HexAM provided increased thermal durability as evidenced by a reduction in the loss of modulus with heating. This attribute will have value in the market. The addition of HexAM decreased the permeation of oxygen and water vapor through the films and made the film surface more hydrophobic. These characteristics will resolve deficiencies in HPMC and allow it to enter new markets. In limited testing, the HexAM containing films provided microbial and thermal resistance. For control HPMC films, gas permeability, water sensitivity and poor thermal stability limit the applications of HPMC.