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Effect of filler content, size, aspect ratio and morphology on thermal, morphological and permeability properties of porous talc filled-Polypropylene obtained through MEAUS process

Membranes have gained an important place in chemical technology and are used in a broad range of applications. The most important property of membranes is their ability to control the rate of permeation of different species. The key property that is exploited is the ability of a membrane to control the permeation rate of a chemical species through the membrane. A vast number of investigations have so far been carried out on microporous separators as key materials of separation technology. From energy and process reliability points of view, they progressively compete for the conventional separation process such as distillation.[1] Polymeric membranes are made through various techniques such as phase separation, track etching, leaching, thermal precipitation, and stretching.[1–5] Phase separation is the most employed technology to produce polymeric membranes. Nevertheless, environmental concerns have to be taken into account, such as solvent contamination and costly solvent recovery, although some improvements have been made in the recent decade. In this study, we have employed a technology based on polymer stretching, called MEAUS (melt extrusion—annealing—uniaxial strain). This procedure is applicable to semicrystalline polymers, based on (a) the stretching of a thin film with a row nucleated lamellar structure (b) annealing of the film to thicken the lamellae, and (c) stretching of the film at low temperature to create voids and then stretching at high temperature to enlarge the pores. One of the main issues in this process is the generation of a proper initial row nucleated structure. The polymer type and applied extrusion conditions are key factors for this method. The extrusion and production of the precursor films is a delicate process as the samples should be produced under high draw ratio and cooling rates. Obtaining a very uniform film is a major concern as any nonuniformity and thickness variations cause irregularities in the stress distribution. Also, another way to overcome is to enhance the distribution of pores along the membrane face. This method is relatively less expensive and there is no solvent contamination. Several works are found in the literature, mainly the ones performed by the research group of Ajji,[6] Caihong et al.,[7] focused mainly on the use of neat polyolefins. However, Received: 19 October 2017 | Revised: 9 July 2018 | Accepted: 10 July 2018 DOI: 10.1002/adv.22116