Investigation the effect of processing condition and dispersed phase content on rheology–morphology relationship in polypropylene/polyethylene terephthalate microfibrillar composite

Abstract

Morphological evolutions during the production of microfibrillar composites can be investigated by considering two main steps: (1) the melt blending in the extruder and (2) the drawing process. Deformation, coalescence and break‐up of dispersed phase droplets under shear and elongational flow fields applied in these two main steps lead to the formation of fibrillar morphology. Therefore, it can be stated that the fibrillar morphology is controlled by dispersed phase content, rheological and interfacial properties of the components as well as dispersed phase domains relaxation. In this study, the effect of dispersed phase content on the morphology of the polypropylene/polyethylene terephthalate microfibrillar composite was investigated. Also, three following processing parameters were considered to evaluate the kinetics of in‐situ formation of the microfibrils: Extruder die temperature, water bath temperature and the drawing path length. Linear and nonlinear rheological tests were used as an efficient tool to investigate the rheology–morphology relationship. Among the processing parameters studied, the drawing path length and die temperature had the most and least effect on microfibrillar morphology, respectively. By increasing the drawing path length from 20 to 30 cm, the break‐up of the fibrils and non‐uniformity in the cross section of the fibrils caused a weaker strain recovery after stress removal and also a rapid reduction of stress after cessation of steady shear flow field. Increasing the die temperature has a similar but weaker effect on the final morphology. The rheological results in the linear viscoelastic range all indicated the formation of a physical network of microfibrils within the matrix.

In‐situ generation of biodegradable poly(lactic acid)/poly(butylene succinate) nanofibrillar composites via a facile and cost‐effective strategy of pressure‐induced flow processing

“…Currently, it has been reached a consensus that the formation of unique microfibril or nanofibrill structures using processing flow fields is one of the effective and eco-friendly methods to achieve expected macro-performance. 7 Several new-type polymer processing techniques, including slit die extrusion-hot stretching-quenching (SDEHSQ), [8][9][10][11] oscillation shear injection molding (OSIM), [12][13][14] multistage stretching extrusion (MSE), [15][16][17][18][19] and loop oscillating push-pull molding (LOPPM), [20][21][22][23] have successfully produced in-situ fibrillation reinforced composites. The reported literature showed that the existence of a fibrillated phase in in-situ composites not only endows higher specific interfacial area but also plays a heterogeneous nucleation effect to induce the formation of hybrid shish-kebab superstructure.…”