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Continuous anionic polymerisation of catalysed E -caprolactam has been undertaken on an intermeshing co-rotating twin-screw extruder for the preparation of polyamide 6. An optimised extruder screw and barrel configuration was used during reactive extrusion process to permit necessary feeding, mixing, devolatilising and pumping requirements. Various screw speeds and barrel temperature profiles were also employed to influence the thermal and shear history of the reaction mixture. Differential scanning calorimetry and wide angle X-ray diffraction techniques were used to characterise the thermal properties and crystalline order of the polymerisation product. It was observed that the extent and form of the crystalline structure can be greatly influenced by the material composition, method of preparation and annealing procedures during and after the polymerisation stage. Molecular weight, molecular weight distribution and residual monomer content of the reactive polymerised PA6 samples as determined by solution viscometry, gel permeation chromatography and gas chromatography analysis revealed that these properties could be influenced by polymerisation conditions in the extruder, yielding values of Mw up to 100 kg.mol-1 and polydispersity index as high as 6 with monomer residue contents of 4-6%. Selected mechanical properties of the PA6 samples as measured using standard test procedures exhibited superior impact and elongational properties under tensile deformation but showed a slightly reduced tensile strength compared to commercial polymer. A reactive polymerised blend of PA6 with 10 wt% EPR copolymer has been successfully synthesised in a similar manner using the twin-screw extruder at a screw speed of 150 rpm. This elastomer modified blend material exhibits superior tensile and impact strength compared to the pure PA6. Enhancement of the mechanical properties is postulated to be attributed to the formation of a PA6-gPE graft copolymer which can possibly functioned as an emulsifying agent to lower the interfacial tension between the two phases thereby compatibilising the blend. Experimental evidence from FTIR and phase solubility studies have supported the formation of this graft copolymer. Characterisation studies by DSC, DMA and W AXD suggested structural modification of the EPR copolymer has occurred as a result of chain scission during the polymerisation/ blending process leading to the formation of a crystalline PP phase and an amorphous PE component. Macroradicals formed from this mechano-degradation reaction by chain scission of the reacting polymers are postulated to be responsible for the formation of this graft copolymer. Blends of reactive polymerised PA6 and a commercial grade isotactic PP homopolymer of compositions 10%, 30%, 50% and 70% PP were also prepared with and without the presence of another commercial grade functionalised PP compatibiliser. Results obtained from structural, morphological and mechanical studies obtained for the non-functionalised blend of 10% PP showed apparent "miscibility" of the phase components which is an unexpected observation since PA6 and PP are well known to be incompatible. It is postulated that a branched PP and a PA6-g-PP graft copolymer has been formed, as a result of mechano-degradation reaction during the extrusion/blending process. Reaction blends with higher PP compositions however, sbowed incompatibility behaviour with coarse blend morphology and poorer mechanical properties. Phase inversion phenomena for this reaction blend is observed at PA6 composition of 30% with evidence of interpenetrating polymer network structure in the blend mophology. The functionalised reaction PA6/PP blends with 5% compatibiliser showed phase separation of the polymer components in all compositions as evidenced from DSC, W AXD, DMA and SEM studies. No improvement of mechanical properties was observed as compared to the blends without compatibiliser. A PA6-g-PP-g-MA graft copolymer has postulated to have formed between the PA6 and the compatibiliser but this compatibisation effect is not efficient enough to enhance the mechanical behaviour of the blends.

A statistically based mixture design was used to plan experiments on plasticiser blends in PVC compounds. This work investigates compatibility, the extrusion characteristics at different shear rates and the properties of these compounds. Seventeen different plasticisers, spread over five binary and twelve ternary plasticiser systems, were screened for their compatibility. Standard methods such as the solid-gel transition temperature and the FloryHuggins interaction parameter were used. For the binary blends of different plasticiser families, the interactions correlate with increasing differences of the solid-gel transition temperature of the monomeric plasticisers used. If the blend contains a polymeric plasticiser, the interaction decreases with increasing differences in the solid-gel transition temperature. The mechanistic theory of Doolittle enables the interactions of ternary and higher plasticiser systems by using PVC in compositions of binary ones to be assessed. UNIFAC-FV was used to predict the F1ory-Huggins interaction parameter of single plasticisers and of the ternary plasticiser system DOP-DOA-DOS. For plasticisers under investigation, the same relative order of compatibility ranking was obtained using either the solid-gel transition temperature or UNlF AC-FV. The latter was also applied to predict the Gibbs free energy of mixing for a series of monomeric and polymeric plasticisers. For the various ternary systems, some physical properties such as heptane extraction showed an excellent correlation with the solid-gel transition temperature. For a selection of eight ternary plasticiser systems, the ease of fusion during processing on a Haake Rheometer was evaluated A clear relationship was found between the kneader data at the fusion peak and the solid~gel transition temperature, except for the ODPP and C911P containing systems. These systems showed a good correlation between the kneader data and the solid-gel transition temperature and shear viscosity of the compound or viscosity of the plasticiser. Finally, the extrusion characteristics of five ternary plasticiser mixtures were determined. These characteristics were also found to dependent on the solid-gel transition temperature. In some cases, however, the extrusion characteristics also depended on other variables, such as shear viscosity and bulk density of the compounds used.

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