Tailoring compatibilization potential of maleic anhydride–grafted polypropylene by sequential rheochemical processing of polypropylene and polyamide 66 blends
Reactive compatibilization of immiscible polymer blends using a preferred compatibilizer leaves the following question: How much loading of a compatibilizer is good enough and what maximum properties can be achieved? A good understanding of the process can help solve the reutilization of mixed waste plastics. Here, the reactive compatibilization of polypropylene-graft-maleic anhydride (PP-g-MAH) on polypropylene/polyamide 66 (PP/PA66) blends is quantitatively assessed using thermorheological, microoptical, spectroscopic, and x-ray scattering-based characterization tools. The overall compositions of all PP(60%)/PA66(30%)/PP-g-MAH(10%) blends are kept constant while systematically controlling the degree of the chemical reaction by varying the sequential addition of PP-g-MAH to the melt mixture. The first feeding of PP-g-MAH (x%, 0 ≤ x ≤ 10) is conducted at 280°C and the second feeding of (10–x)% is at 200°C. During the first step, a larger amount of chemical activity is observed up to 4%–6% addition of PP-g-MAH. Furthermore, the constant chemical composition allows a systematic comparison of the compatibilizer-dependent thermal, rheological, morphological, and mechanical properties. With an increased degree of interfacial reaction, the size of dispersed PA66 domains decreases to register improved interfacial adhesion with the PP matrix, yielding enhanced Young's modulus and absolute failure strength of the isotropic matrix.