2026-09-23T00:00:30Zhttps://bura.brunel.ac.uk/oai/request

oai:bura.brunel.ac.uk:2438/52392014-11-01T12:29:38Zcom_2438_23com_2438_58col_2438_3672col_2438_231

Ess, John William 2011-06-07T14:31:29Z 2011-06-07T14:31:29Z 1989 http://bura.brunel.ac.uk/handle/2438/5239 This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University. A new design of closely intermeshing co-rotating twin-screw compounding extruder, developed at Brunel University, has been utilized in the development of quantitative techniques for characterization of dispersive and distributive mixing in thermoplastics materials prepared by extrusion compounding. Image analysis procedures were used to quantify mixing of polypropylene composites containing calcium carbonate filler using reflected light microscopy on polished surfaces, and transmitted light microscopy of microtomed pigmented sections. Stereological statistics have been applied to raw sample data; results are discussed in relation to mechanistic phenomena influencing particle agglomeration, dispersion and distribution of fillers in thermoplastics. Dispersive or intensive mixing determined from calcium carbonate filled polypropylene specimens showed that processing parameters had no significant influence except when filler was added midway along the machine although the melting zone was highlighted as having a marked effect on the rate of filler dispersion. Premixing of filler and polymer introduced additional agglomeration into the filler. A series of model experiments were undertaken to assess the influence of specific parameters. In this context moisture content emerged as having the single most important effect on filler compaction. Distributive or extensive mixing of carbon black pigmented specimens was very significantly affected by the presence of segmented disc elements at the end of the screws. These elements produced more than a six-fold increase in distributive mixing in the extrudate. Submitted by Otue Ekong (lbsrooe@brunel.ac.uk) on 2011-06-07T14:31:07Z No. of bitstreams: 1 FulltextThesis.pdf: 13631103 bytes, checksum: 0965e0f04a3c19fe20a70ad3318a9f92 (MD5) Approved for entry into archive by Otue Ekong(lbsrooe@brunel.ac.uk) on 2011-06-07T14:31:29Z (GMT) No. of bitstreams: 1 FulltextThesis.pdf: 13631103 bytes, checksum: 0965e0f04a3c19fe20a70ad3318a9f92 (MD5) Made available in DSpace on 2011-06-07T14:31:29Z (GMT). No. of bitstreams: 1 FulltextThesis.pdf: 13631103 bytes, checksum: 0965e0f04a3c19fe20a70ad3318a9f92 (MD5) Polymer Engineering Directorate of the Science and Engineering Research Council; Croxton and Garry Ltd. en Brunel University School of Engineering and Design PhD Theses http://bura.brunel.ac.uk/bitstream/2438/5239/1/FulltextThesis.pdf Thermoplastics materials Image analysis procedures Polypropylene composites Calcium carbonate filler Light microscopy Characterization of dispersive and distributive mixing in a co-rotating twin-screw compounding extruder Thesis