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Title: Investigation of methods to manufacture multilayered and reinforced composites in rotational moulding
Author: Chang, Wai Chow
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2013
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Full text unavailable from EThOS. Thesis embargoed until 01 Oct 2018
This work forms part of a large EU funded project, RotoFlex, which aims to develop an automated filling system for the rotational moulding process. As part of that project it was necessary to (i) assess how material may sag or flow during the filling stage of the multilayer moulding process (ii) investigate methods to reinforce mouldings using glass fibres (iii) investigate methods to reinforce mouldings using layered silicate nanoclays. As a means of characterising material sagging, a test method based on rotational rheometry and actual sagging measurements has been developed. The data from these tests was used to formulate a simple model to predict flow or material sag with time. A comparison with experimental results shows that the prediction is under estimated by about 18%. It found that the extent of sagging is proportional to the initial layer thickness, time of holding mould stationary, and temperature, whereas it is inversely correlated with the viscosity of polymer. Guidelines for designing sag-free moulding and a method for recovery of the sagged material have also been developed. In the second part of the work the effect of different glass fibres (treated and untreated), compatibiliser (different MFI and MAH level) and composite preparation methods (with or without pre-compounding) on the performance of the rotationally moulded composites was investigated and results are repOlied in term of morphology, rheological and mechanical properties; The composites made with pre-compounded composite powder have superior tensile and impact properties to those made with pellets. A single layer composite moulding with 35 wt% of glass fibre exhibited a 160 to 170% increase in flexural modulus, and 158 to 176% in tensile modulus compared with the unfilled polyethylene. In the third section of the work to determine how layered silicate nanoclays can be introduced into rotationally moulded parts to improve mechanical performance different clays (Cloisite 20A and Somasif MTE) ~---- --- and base resins (high and low viscosity polyethylene, nylon 11) were examined. The incorporation of nanoclays into the resins has the effect of increasing the zero shear viscosity of the molten material. This had a detrimental effect on the ability of the polymer to sinter properly and for bubble dissolution and hence reduced mechanical properties. Increasing compatibiliser:clay ratio in the polyethylene matrix increases exfoliation but also increased the zero shear viscosity and results in lower performance compared with the lower compatibiliser:clay ratios. The nylon 111nanoclay system exhibited the best enhancement in tensile modulus with a maximum 140% increase at a nanoclay loading of 10 wt% compared with a maximum increase of 39% for the polyethylene/nanoclay system at 5 wt% nanoclay. The Halpin-Tsai model predictions for the modulus were in good agreement with experimental results for nylon/clay system up to 10 wt% of clay concentration. In all cases, the impact performance decreased as reinforcing agent was added
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available