Browsing by Author "Liiri, Maija"

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  • Mikroaaltomittaus puutuoteteollisuudessa
    (2008) Liiri, Maija
     Kemian ja materiaalitieteiden tiedekunta | Bachelor's thesis
  • Properties of a new thermoplastic plywood product
    (2013-12-03) Liiri, Maija
     Kemian tekniikan korkeakoulu | Master's thesis
    Environmental aspects are more and more appreciated, which in one hand amplifies the attraction of wood products and in the other hand pushes the wood industry to develop more refined products to reduce the flaws of wood material. Grada appeared to be a new, innovative and intriguing product in wood industry. The aim of this study was to better understand the behaviour of the thermoplastic bonded plywood product by investigating its stability and strength properties through several distinctive tests. Tests were conducted to Grada in both stages, prior and after the forming process, with a comparison of the conventional products: urea formaldehyde bonded flat birch plywood and formed beech plywood. The moisture penetration through faces and edges was studied, in line with the dimensional changes. Furthermore, the strength properties of Grada were analysed through both static and impact tests. Grada proved to have improved moisture resistance especially in the flat stage, before forming. The formed Grada seemed to have slightly lower MC resistance. There were also indications of tensions and microscopic cracks in the product, induced by the forming process. Grada also appeared to be more reactive to the surrounding conditions, but solely in short-term, which was mainly due to its lower moisture content. The strength test showed interesting outcomes as well. Even though Grada did not attain higher strength values than the conventional plywood, there was seemingly less divergence among the values compared with the conventional plywood. The thermoplastic acted as a fader of the defects of wood, forging a uniform wood composite with the appearance of beautiful plywood. The amount of test specimens was low, due to the variety of the tests. Thus, to scientifically prove the validity of the results, it is recommended to repeat the test with higher amount of specimens.