Influence of twin-screw elements on dispersion of nano-clay in vinyl ester polymer composites using Taguchi’s orthogonal array technique

Abstract

This work aims to experimentally investigate the influence of screw elements on the dispersion of Cloisite-15A in vinyl ester based on the design of experiments using MINITAB-V16 software. Experiments were designed considering two main factors such as Cloisite-15A loading (1, 2, 3, and 4 wt%) and type of screw elements with a varying number of kneading elements (type 1 with 55 mm, kneading elements and type 2 with 90 mm, kneading elements). The dispersion procedure of Cloisite-15A in vinyl ester was carried out by a combination of both ultrasonication and then twin-screw extrusion. The influence of these factors on the tensile strength and hardness was studied using an experimental layout possessing Taguchi’s L8 Orthogonal Array technique. ANOVA of the experimental results revealed the dispersion of Cloisite-15A with vinyl ester proved to be better when processed with type 2 screw elements having more kneading screws. The S/N ratio study showed that the Cloisite-15A loading had the greatest impact on the type 2 screw's tensile and hardness values for the Cloisite-15A/vinyl ester gel coats when treated at 230 rpm with 10 passes. The probability graphs led to the conclusion that, with a 95% confidence interval, all response values were distributed equally along the normal probability plot's trend. In order to achieve the best response in terms of mechanical strength, the Grey Relational Analysis (GRA) helped identify the best combination of process variables. This combination was known to be 4 wt% Cloisite-15A loading, with type 2 screw processed at 230 rpm with 10 passes. The SEM and XRD showed the absence of agglomeration and better exfoliation of Cloisite-15A in the gel coats with 4 wt% of clay loading.