Tensile test under quasi-static loads conditions is usually used to determine the mechanical strength of thermoplastic starch films. This kind of test does not fully illustrate the load conditions for packaging films, which, under the conditions of use, are succumb to dynamic loads. Thus, the aim of the study was to present the possibilities of using a patented soft tissues measurement testing station to analyze the mechanical strength of thermoplastic starch (TPS) films under impact loading conditions. Two groups of film specimens containing the addition of psyllium husks (TPS/PH) and psyllium flour (TPS/PF) were used for the measurements. The casting method was applied, and glycerol was used as a plasticizer. Microstructure of the specimen surface was analyzed by stereoscopic microscopy. Specimens with the addition of psyllium flour had a more uniform microstructure. The maximum breaking forces obtained during impact tests for these films were 5 times higher than specimens containing psyllium seed husk. The same behaviour was found with respect to stresses with average values of 48.6 MPa for TPS/PF and 20.2 MPa for TPS/PH. Moreover, research confirms usefulness of patented soft tissues measurement testing station to analyse the mechanical strength of thermoplastic starch films.
The aim of the study was to investigate the influence of kaolinite (KA) and beeswax (BW) addition on the structural and physical properties of thermoplastic starch (TPS) films. The casting method was applied and glycerol was used as a plasticizer. Microstructure analyzes were made by a stereoscopic and a scanning electron microscope. Tensile tests were carried out under static load conditions at three different deformation velocities of V=0.0001, 0.001, and 0.01 m/s. The studies of surfaces characteristic were performed using water contact angle and water vapor isotherm measurements. The most homogeneous structure of the surface with higher mean values of failure stress and elasticity modulus was observed for thermoplastic starch films with kaolinite addition. The significant reduction in dynamics changes of water contact angle (10%) of BW films in the time 0-20s as well as tensile strength decrease was noted (compared to pure TPS films). The research results suggest the validity of using BW and KA to improve the barrier and mechanical properties of TPS films. Further research should focus on to improve the starch-beeswax-kaolinite combination and increase the homogeneity of the structure of films in order to upswing their simultaneous impact on barrier and mechanical properties.
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