Creation of a controlled advanced biodegradable composite system

The use of poly(vinyl alcohol) PVA as a biodegradable polymer has been confined to low technology applications such as paper coatings and fibre sizing, which rely upon its inherently poor resistance to moisture to initiate degradation and ultimate disposal. Despite low-tech application of the material to date, PVA exhibits properties that are compatible with more sophisticated applications. The inclusion of natural fibres and fillers gives further improvements in mechanical properties without compromising overall degradability. However the potential of this material as an engineering polymer cannot be realised because of its limited moisture resistance which naturally limits the number of practical applications, particularly those that are exposed to diverse environmental conditions. Warwick Manufacturing Group has developed a waterproofing method that can be tailored to deliver a time-delayed degradation mechanism or even stop water ingress completely. Most importantly the biodegradability and mechanical properties of the PVA are not affected, just the time-scale. This tailoring is achieved through the inclusion of a biodegradable additive (that degrades via a different mechanism) that creates an advanced multifunctional sandwich structure, during the single-shot injection moulding process (i.e. not multi-component moulding), encapsulating the PVA. Onset of biodegradation can be initiated by compromising the integrity of the structure.