The oxidised and HMT potato starch films had higher tensile strength when compared to native starch (Table 5). According to Zamudio-Flores, Vargas-Torres, Pérez-González, Bosquez-Molina, and Bello-Pérez (2006), the tensile strength of films increase with the degree of starch oxidation because this parameter is higher when the active chlorine concentration increases. The presence of carbonyl and carboxyl groups in the oxidised starch may produce hydrogen bridges with the OH− groups of the amylose and amylopectin molecules, and these linkages provide more structural integrity in the polymeric matrix, thereby, increasing tensile strength. These authors

also suggested that the increase in tensile strength with the increase in oxidation level in the starch used for film preparation may be due to the increased interactions among polymer chains, which affect LY2109761 nmr the crystallinity and flexibility of the film. Elongation at break is the increase of the sample length from its original length in the stress–strain experiment at the break point. The

percentage elongation Fluorouracil research buy at break of polymeric materials depends on the flexibility of the molecular chain. During the processing of potato starch film, the granular and crystal structures of starch are mostly destroyed by high temperatures and shear forces, and the resulting structures are considered to exist mainly in an amorphous phase (Hu et al., 2009). The elongation at break of the native starch film was reduced from 85.20% to 58.33% with the increase of the starch concentration

from 3% to 5%. The increase of starch concentration from 3% to 5% also decreased the elongation of the oxidised starch film. The oxidised potato starch films had lower elongation values compared to the native and HMT starches. The films with 4% and 5% HMT potato starch had higher elongation values compared to the films with 4% and 5% native starch (Table 5). According DAPT to Zhang et al. (2009), the tensile strength of thermoplastic oxidised corn starch with high carbonyl content decreases with the increase of glycerol content, whereas the elongation at break increases with the increase of glycerol content. Singh et al. (2009) studied the properties of starch films prepared from native and HMT chestnut starches, and they reported tensile strength values of 6.89 and 53.45 N, respectively. For comparison with other biopolymer films, Kim, Ko, and Park (2002) reported that the tensile strength of carboxymethylated starch films range from 9.7 to 15.3 MPa and that the elongation values of carboxymethylated starch films range from 2.6% to 7.7%. Araujo-Farro et al. (2010) produced films from quinoa starch (4.0 g/100 ml) under different conditions, and they reported the following mechanical properties under optimised conditions: tensile strength of 7.56 MPa and 58.14% elongation at break. They reported the optimised conditions for the quinoa starch-based films to be as follows: 21.