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On improving the cost-effective dispersion of calcium carbonate in polypropylene for impact resistance

Jones, Paul Glyn (2011)
Eng.D. thesis, University of Birmingham.

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The potential to improve the performance of polymer composites cost-effectively has been researched across various aspects of development and manufacture. Each endeavour fell broadly into one of three categories; the principal ingredients and their required properties, the methods with which they were transformed into products and the means by which they were observed. It was determined that the ingredients with the highest potential as defined, each shared simplicity and abundance as material traits. The use of bespoke functionalised ingredients proved costly to implement, providing only modest property benefits compared to a standard formulation comprising polypropylene, 10 – 30 % w/w of 2 μm calcium carbonate with 0.5 – 1.0 % w/w stearic acid surface treatment. It was found that an apparent deterioration in impact resistance that was encountered on reducing the filler particle size was in each case observed, attributable to a coarsening of these fine particles that resulted from the mixing process. Finer particles could not be implemented more cost-effectively than standard formulations; an effect which was attributed to the tendency of the finest particles to form aggregates that could not be decomposed by mixing under high shear. However, the favourability of particle dispersion in standard formulations was used to implement a production method of polymer composites that required significantly less energy across the entire production stage and held other significant advantages. Concentrates comprising minerals in wax were produced and made to successfully re-disperse from loadings approaching those allowed by their theoretical packing maxima, in some cases up to 90 % w/w. Furthermore, a single injection moulding cycle with minimal back-mixing was used to combine concentrates and neat polymers to make commercially-competitive composite specimens, at final concentrations as low as 10 % w/w. A principal method to obtain in situ visual particle data from thin composite films was developed along with several derivative analyses. The techniques allowed rapid and representative data collection for high particle proportions at resolutions of 6 – 8 μm, accounting for particles most relevant to impact-resistance in standard formulations. As a whole, significant and realistic saving opportunities were identified in the expenditure of unnecessary resources, such as; processing energy, capital investment, transportation, labour and time. These findings were supported by experimental data.

Type of Work:Eng.D. thesis.
Supervisor(s):Rowson, Neil
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Chemical Engineering
Subjects:TP Chemical technology
Institution:University of Birmingham
ID Code:3168
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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