Chiang Mai Journal of Science

We measured the effect of crosslinking with Ba²⁺, Ca²⁺ and Zn²⁺ ions to sodium alginate (SA) mixed with carboxymethyl cellulose (CMC) film, prepared by solution casting. Although heavy metal ion crosslinked films had higher tensile strengths than neat SA/CMC films, the elongation at break, light transmission and swelling had decreased. In crosslinked films, film thickness and thermal stability also increased. Crosslinking with Ca²⁺ ion showed the optimum film properties. The effect of Ca²⁺ ion concentration between 1 to 4% w/v of CaCl₂ to SA/CMC film properties were further investigated. The 2% w/v of CaCl₂ had dominated the highest tensile strength compared to 3% and 4% w/v of CaCl₂. Light transmission, thickness and thermal stability were not affected. In conclusion, the 2% w/v CaCl₂ is the appropriated concentration for film preparation in packaging industry.