Modeling and optimizing  toughness and rigidity of PA6/SBR: Using compatibilizer and response surface methodology

The improvement of miscibility between toughened Polyamide-6 (PA6) and Styrene-Butadiene Rubber (SBR) was carried out using grafted Glycidyl Methacrylate (SBR-g-GMA). At first, the compatibilizers were prepared using different comonomers, Styrene, and N-vinyl pyrrolidone. Central composited design (CCD) was distinctly applied to study the influence of Glycidyl Methacrylate (GMA) content and comonomer/GMA on the process of compatibilizer preparation. Four models were developed for Gel content and Degree of grafting for both comonomers using Design-expert software. The models were used to calculate the optimum operating conditions and according to the Flory-Huggins parameter and obtained results, SBR-co-NVP-g-GMA was chosen as an effective compatibilizer. Afterward, another CCD was employed to scrutinize the effect of various amounts and grafting degree of compatibilizer on morphology and mechanical properties of PA6/SBR. The Interparticle distance and polydispersity were studied using a Scanning electron microscope (SEM) and also the Izod impact test inspected in order to evaluate the mechanical properties. Finally, modulus and impact strength were optimized to minimize the former and maximize the latter. Also, the most practical terms in the fitted model are statistically specified using F-value. The root causes for the improvement of blend properties were attributed to a chemical reaction between epoxy groups in SBR-g-GMA and both the carboxylic and amine groups in PA6. Impact strength (539.8 J/m) and modulus (2017.2 N/mm2) of the optimum blend indicate an excellent agreement with the amounts predicted by the models. [Display omitted] •The effect of two types of comonomer was experimentally compared and the main reason for choosing NVP was theoretically investigated by Flory-Huggins parameter.•The influence of each parameter of fitted models were identified using ANOVA table and F-value.•The main causes for the emergence of gel in compatibilizers were inaugurated.•Optimization of operational conditions for preparing the compatibilizers was carried out using response surface methodology and desirable function.•The detrimental effect of gel formation on the cavitation and mechanical properties of the blends was explained using the Dompas model.