USE OF TURKISH BENTONITE MINERAL AS AN ADDITIVE FOR POLY(LACTIC ACID) BASED BIO-COMPOSITE MATERIALS

Abstract

In this study, Turkish bentonite (BN) mineral is subjected to silane treatment in order to enhance its compatibility for poly(lactic acid) (PLA). Neat and surface silanized BN powders are compounded with PLA using melt blending process at the concentrations of 5, 10, 15 and 20 wt%. Surface characteristics of BN samples are examined by infrared spectroscopy. Mechanical, thermo-mechanical, water resistance, melt flow and morphological investigations of composites are performed by tensile and impact tests, dynamic mechanical analysis (DMA), water absorption test, melt flow rate test (MFR) and scanning electron microscopy (SEM) analysis, respectively. Mechanical test results show that BN additions lead to increase in tensile strength and modulus of PLA. The maximum improvement is obtained for 15 wt% of silanized BN containing composite. Silanized BN filled PLA displays higher impact performance compared to untreated BN sample. Impact energy values of composites increase with increase in loading ratio. Silanized BN containing composite with 20 wt% concentration gives the highest storage modulus according to the DMA study. Glass transition temperature of PLA is improved by the inclusions of all BN samples. Additions of BN make slight decreases on MFR value of PLA. However, these reductions are found to be negligible in terms of its effect on processing of material. Water uptakes of composites are found to be higher than that of PLA. Composites containing silanized BN have lower water absorption values than neat BN samples due to the hydrophobicity of silicon containing surface. SEM characterization reveals that more homogeneous dispersion in PLA matrix is observed for silane treated BN compared to neat BN particles thanks to improvement of interfacial adhesion between BN and PLA matrix.