Processing optimization of starch-talc nanocomposites by injection moulding at laboratory scale

F. OTAOLA; L.A. CASTILLO; O.V. LÓPEZ; M.A. GARCÍA; M.A. VILLAR; S.E. BARBOSA

Buenos Aires

Conferencia; 6th International Conference on Science and Technology of Composite Materials ? COMAT 2015.; 2015

Processing of starch based materials by melt-mixing present certain difficulties mainly due to the presence of water that produces vapor generation which leads to foamy starch. This final product is not appropriated to be used in injection or thermo-compression process. In this sense, the aim of this work is to optimize formulations, as well as, processing conditions by injection moulding of composite materials based on thermoplastic starch and talc nanoparticles. A design for mixtures of four components, with three replicates in the central point, was employed. Dependent variables were concentrations of native corn starch (S), glycerol (G), water (W) and talc (T). Maximum and minimum concentrations of each component in the mixtures were established to delimit the study zone and to make feasible this investigation. These limits were proposed based on preliminary tests being 45-70, 30-40, 0-10 and 0-5 % w/w for S, G, W and T, respectively. They were determined using the Statistica software version 6.0, (Statsoft, USA). Mixtures were processed by injection moulding in a mini-mixer. Operational conditions (temperature, rotor speed and time) were optimized, being the most appropriated 150 ºC, 100 rpm and 30 min. All formulations were able to be injected as circular (25 mm diameter) and rectangular (13 x 76 mm) probes. All specimens resulted homogeneous without bubbles presence. By Scanning Electronic Microscopy, it was detected that talc particles were well-distributed within the matrix and a good interfacial adhesion was evidenced. Composites FTIR spectra presented the characteristics bands of the functional groups corresponding to starch, glycerol and talc. Particles presence influence on starch crystallites fusion was studied by Differential Scanning Calorimetry. Rheological behaviour of injected specimens was evaluated by frequency sweeps (0.05 to 500 Hz) at 150 ºC, determining elastic and storage modulus, as well as, apparent viscosity.