This study evaluates the effects of ethylene-propylene-diene-monomer grafted maleic anhydride (EPDM-g-MAH) and internal mixer melt compounding processing parameters on the properties of natural rubber/ethylene-propylene-diene rubber (NR/ EPDM) blends. Using Response Surface Methodology (RSM) of 2 5 two-level fractional factorial, we studied the effects of NR/EPDM ratio, mixing temperature, Banbury rotor speed, mixing period, and EPDM-g-MAH contents in NR/EPDM blends. The study found that the presence of EPDM-g-MAH in NR/EPDM blends had a predominant role as a compatibilizing agent, which affected the processability and properties of the final material. We also determined the model fitting with constant determination, R 2 of 99.60% for tensile strength (TS) response with a suggested combination of mixing process input parameters. The reproducibility of the proposed mixing strategy was then confirmed through model validation with a minor deviation at 12.303% and higher desirability of 0.960. This study is essential in providing a process design reference for NR/EPDM blends preparation by melt-blending and the role of a compatibilizer from the systematic Design of Experiment (DOE) approach. The experimental findings were further supported with swelling and cross-link density measurements, differential scanning calorimetry analysis, and observation of fracture morphology using a scanning electron microscope.

The facile approach of non-covalent surface treatment utilizing poly(ethyleneimine) (PEI) polymer was applied to modify graphene nanoplatelets (GNPs). The effects of surface modification and various GNPs-PEI loadings to cure characteristic, mechanical, physical, and morphological properties of natural rubber (NR)/ethylenepropylene-diene-monomer (EPDM) blend nanocomposites were studied and compared to the unfilled NR/EPDM blend and blends filled with unmodified GNPs at similar loadings. We found that the modification of GNPs surface significantly influences the properties of NR/EPDM blends. The addition of GNPs significantly improved the blend's processability, offering approximately a 104.30 % increase in tensile strength obtained with the addition of 5.00 wt% GNPs-PEI. A reduced swelling index of Q f /Q g in parallel with an increase in modified GNPs-PEI content revealed enhancements in terms of rubber-filler interactions between the NR/EPDM matrix and GNPs. These findings were further supported by X-ray diffraction, differential scanning calorimetry, thermogravimetry analysis, and fracture morphology by scanning electron microscope.

Abstract

Abstract. Fractional 25 two-level factorial design of experiment (DOE) was applied to systematically prepare the NR/EPDM blend using Haake internal mixer set-up. The process model of rubber blend preparation that correlates the relationships between the mixer process input parameters and the output response of blend compatibility was developed. Model analysis of variance (ANOVA) and model fitting through curve evaluation finalized the R 2 of 99.60% with proposed parametric combination of A = 30/70 NR/EPDM blend ratio; B = 70°C mixing temperature; C = 70 rpm of rotor speed; D = 5 minutes of mixing period and E = 1.30 phr EPDM-g-MAH compatibilizer addition, with overall 0.966 desirability. Model validation with small deviation at +2.09% confirmed the repeatability of the mixing strategy with valid maximum tensile strength output representing the blend miscibility. Theoretical calculation of NR/EPDM blend compatibility is also included and compared. In short, this study provides a brief insight on the utilization of DOE for experimental simplification and parameter inter-correlation studies, especially when dealing with multiple variables during elastomeric rubber blend preparation.

A statistical model was developed in this study to describe cure characteristic, rebound resilience and tensile strength of natural rubber/starch composites which was prepared by using a Haake internal mixer. Response surface methodology (RSM) based on central composite centered design (CCD) was employed to statistically evaluate and optimize the conditions for maximum cure characteristic, rebound resilience and tensile strength and study the significance and interaction of carbon black and glycerol on rebound resilience and tensile strength yield. The experimental runs were carried out according to a 22 full factorial design for the two identified design independent variables, namely, carbon black (X1) and glycerol (X2). With the use of the developed quadratic model equation, a maximum rebound resilience 71% was obtained to be a carbon black loading of 50 phr and glycerol loading of 7 %.