Development of a novel binder system for manufacture of ceramic heart valve prostheses

Heart valve prostheses have become common since their introduction in the 1 960s. Although prostheses work well in situ at the physiological site they are not designed for other applications such as conduits. Research at Notti ngham Trent University has led to the design of a conduit valve prosthesis to allow for correct arterial and valvular flow. Requirements are to have a porous internal structure to incur tissue in-growth, improve heamodynamic performance and longevity of the prosthesis. Powder reaction moulding techn ology has been implemented to create such a prosthesis from medical grade a luminium oxide. Methyl methacrylate and cyanoacrylates were investigated as binders with aluminium oxide as the powder constituent. The production of samples with a small L/D ratio and analysis of reaction kinetics provided v aluable evidence to support the role of these binders. It was found that me thyl methacrylate can only mix to a powder volume fraction of 0.33, whilst cyanoacrylate can bind with alumina to a higher volume fraction of 0.45. Wi th cyanoacrylate binding the largest fraction, samples were moulded from cy anoacrylate/alumina utilising a hand extrusion unit. The mould design repre sented the conduit heart valve and was manufactured from polytetraflouroeth ylene (PTFE). Investigation of the moulded bodies leads to two observations . Firstly, cyanoacrylate requires a surface initiation to polymerise within a mould cavity and secondly, mould release agents are needed to extract th e part. Preliminary investigation into thermal de-binding of cyanoacrylate from alumina has been completed with promising results, proving that cyanoa crylate is a useful constituent for reaction moulding. (C) 2001 Elsevier Sc ience B.V. All rights reserved.