Development of improved characterisation and service prediction techniques
Over 40 test methods for cellulose insole boards, addressing 26 properties, have been reviewed. Key needs identified were procedures for measuring lateral water transmission, improved reliability of tests for biodeterioration resistance and improved procedures for determining binder content. A wicking test using a material strip has proved able to distinguish between materials, but a new procedure in which water is introduced to one surface and wicks from a circular zone more closely simulates wetting in wear. A moisture transfer test that has the advantage of wetting only from one surface has also been developed. The soil burial test for biodeterioration has been speeded up by using a standard compost of controlled moisture content, and a means of exposing materials on one side, as in the shoe, has been developed and found to correlate with service performance. A technique for binder content based on acid digestion of cellulose has been speeded up by increasing the temperature, and validated using raw materials and blends.
Identification of the key factors for improved resistance to microbial deterioration and enhanced comfort
A range of boards for various footwear applications, including examples with and without biocide, has been tested before and after soil burial. The results showed a marked variation in properties, and some boards were seriously weakened by soil burial with flexing and scuff resistance especially sensitive to change. Biocides were found to be beneficial. Electron microscopy and tensile tests have shown fibre-binder interactions to be important. Ageing tests have ruled out cellulose hydrolysis as a deterioration mechanism. The acid digestion technique for binder content has been adapted to handle small samples from deteriorated footwear or test pieces. This enables deterioration to be monitored, binder content increasing as cellulose is destroyed.
Initial examination of innovative approaches to enhancing the performance of cellulose board
The improved soil burial technique has been selected for screening laboratory samples, together with culture tests using microorganisms. A review of possible approaches to fibre/binder modification and the use of novel binders and biocides has been completed. Raw materials used in board production have been sourced for use in bench scale studies on the interactions of current and novel constituents, before trial production of boards from promising formulations.
Production of prototype cellulose board samples
Three batches of prototype boards have been produced, using the knowledge obtained of key factors. These provided further evidence for the benefit of biocides, at least under test conditions. Further samples have been prepared using promising innovations identified. These include novel types of biocides and application methods, which minimise environmental impacts, and the use of thermoplastic synthetic fibres in partial or complete substitution for latex as binder. Synthetic fibres have been satisfactorily incorporated into the wet-laying process for making boards on a laboratory scale. The process requires further development for full scale production.
Optimising of shoemaking procedures and footwear design
Examination of worn footwear has shown clear evidence that good support of the insole by the sole serves to minimise breakdown. Conversely, shoes with a poor design of ribbed coring on the sole can show severe breakdown, the insoles falling into the cavities thus creating micro-cracks from which biodeterioration can develop. Accumulation of moisture encourages microbiological activity and protecting the most vulnerable site, at the forepart of the shoe, with a coating has also been shown to enhance insole life significantly.
Confirmation of service performance of prototype cellulose insole boards and footwear innovations
To support the work on identifying characterisation techniques and key performance factors, service trials have been carried out three sets of the insole boards which had been tested. The boards were worn in shoes as loose in socks, to facilitate removal for inspection and testing. A further linking trial enabled normalisation of the data for all the boards. The damage and key property changes, which occurred reflected, those produced by soil burial, with a similar ranking of the boards. A service trial of insoles with and without a protective coating at the toe area confirmed the success of this measure in reducing deterioration. A series of service trials has validated test results on the most promising prototype boards. The trials have shown that the novel biocides are effective, and have also demonstrated that synthetic binder fibres can enhance the physical properties and deterioration resistance of the boards.
Cellulose board is derived mainly from renewable resources. It has become established as the most widely used shoe insole material. Cellulose board has generally good shoemaking and wear properties but is susceptible to biodeterioration leading to mechanical breakdown. The ability of cellulose insoles to absorb high levels of moisture is thought to be beneflcial for foot comfort. However, the tendency to retain the absorbed moisture creates conditions favourable to biodeterioration and, despite the use of biocidal agents as a counter measure, premature failure in service is a common occurrence. The use of antimicrobial agents to control biodeterioration has both cost and environmentally related drawbacks. The objective of this project is to investigate methods of enhancing the bioresistance and comfort of cellulose board insole materials through manipulation of their moisture management properties and optimisation of their composition to achieve greater inherent stability thereby reducing the need for biocidal agents. A number of novel methods will be developed for characterising insole boards, in-shoe moisture management, foot comfort and resistance to biodeterioration. The European Confederation of the Footwear Industry (CEC) in collaboration with the European Union of Research Institutes for Shoes has drawn up a Research Strategy for the European Footwear Industry. The proposed project complies with the strategy in that it aims to ,increase product differentiation, develop improved performance measurement and prediction techniques for ensuring quality of materials and products, and develop environmentally friendly materials as stated in Clauses 2, 3, 4 and 3.6 of the strategy document. The research will enable EU footwear manufacturers to provide innovative products with improved comfort, hygiene, service performance and, most importantly, customer acceptance using insole materials with minimum environmental impact.
Funding SchemeCRS - Cooperative research contracts
701 16 Örebro
BL1 2NP Bolton
NN16 9JH Kettering
60388 Frankfurt / Main
431 22 Mölndal