Rigid PVC Nanocomposites - Influence of Processing and Montmorillonite Treatment
Doctoral thesis, 2010
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
KC-salen, Kemigården 4, Chalmers University of Technology
Opponent: Prof. Marianne Gilbert, Department of Materials, Loughborough University, United Kingdom