Effect of calcinated halloysite on structure and properties of rigid poly(vinyl chloride) composites

Halloysite is a filler which may be used to produce composites with thermoplastic polymer matrix. This work summarized the results of investigations of processing, structural, mechanical, and thermal properties of the composites with poly(vinyl chloride) (PVC) matrix and raw halloysite (HA) as well as its calcined product (KHA). The effectiveness of calcination was confirmed with X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and nitrogen adsorption method. The PVC composites with HA as well as KHA were processed in the molten state in the Brabender mixer chamber. The reduction of gelation time and simultaneous increase in maximum torque with filler content were found based on the results of plastographometric analysis. SEM images of PVC/halloysite composites showed a homogeneous distribution of the filler in the polymer matrix. The introduction of halloysite leads to a slight increase in Young’s modulus and tensile strength compared to neat PVC, where the increase of both parameters is greater when KHA is used. The incorporation of 1% KHA led to an increase in impact strength, an effect which may be attributed to toughening of the polymer. A slight improvement of the Vicat softening temperature of 2.7 degrees C for PVC/HA and heat deflection temperature of 2.4 C for PVC/KHA was also ascertained for PVC modified with 10 wt% of filler.