HPMC reinforced with different cellulose nano-particles

Three different types of cellulose nanoparticles: (i) nano-fibrils cellulose (NFC), (ii) nano-fibrils cellulose oxidized using the tempo reaction (NFCt) and (iii) cellulose whiskers, were incorporated into HPMC edible films at different concentrations. The films were examined for mechanical and moisture barrier properties verifying how the addition of cellulose nano-particles affected the water affinities (water adsorption/desorption isotherms) and the diffusion coefficients. In general, addition of NFC or NFCt negatively affected the performance of the HPMC films. However the reinforcing effect of the cellulose particles was observed when whiskers were used as the filling material; an increase of 22% in tensile strength and 55% in Youngʹs modulus were achieved while the elongation at break of the films was preserved. Addition of whiskers also improved the water barrier properties of the composite films. This effect was attributed to the lower water affinity of the composite films, as compared with the HPMC films, since the water diffusivity values were not affected by the addition of whiskers. Furthermore, the whiskers only decreased 3–6% the transparency of the HPMC films showing 86–89% visible light transmission values, allowing application as edible barrier and transparent film.