Rigid PVC Nanocomposites - Influence of Processing and Montmorillonite Treatment

University dissertation from Chalmers University of Technology

Abstract: Poly(vinyl chloride) (PVC) is a material extensively used in various applications due to its low cost, durability, and chemical resistance. There are, however, still improvements that can be made to the material. The work in this thesis has been dedicated to develop a nanocomposite of rigid PVC with montmorillonite, a type of layered silicate clay, as the filler material. Polymer nanocomposites has grown into a major field within material science. Nanometer sized fillers provide unique properties at very low loading levels compared to conventional fillers. Despite the high activity, there are relatively few reports on PVC nanocomposites, and when it comes to rigid PVC matrixes, successful examples are still lacking. Much of this is due to complications with thermal stability and the particular processing characteristics for PVC. Two main issues have been addressed in this work; the first was to overcome the acceleration in dehydrochlorination caused by montmorillonite treated the conventional manner. The results show that by using non-ionic surfactants to modify the clay, this problem can be avoided and still produce nanocomposites with good dispersion. The second issue was to find a suitable processing technique to break down the clay particles, i.e. the clay sheet agglomerates, into small enough sizes. The work was limited to melt intercalation processes where it was shown that using a two-roll mill produced smaller particles size than the more extensively studied microcompounder, even though the latter resulted in the greatest improvement of 59% in Emodulus when a masterbatch process was used. However, the work also led to a new process which significantly reduced the particle size. The E-modulus was now improved by 17.4% compared to the reference, where the conventional method only resulted in improvements of about 6.5%.

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