“There is simply not enough weatherproof timber about. This is why we need a natural material with a long service life that feels like wood and also looks like it, can be produced in an environmentally friendly way and is readily processable“, stipulates Bernd Duna, currently Managing Director of Resysta International. More than 15 years ago the company developed a material that amounts to a real alternative to threatened tropical timber and is particularly suitable for use in outdoor furniture and shipbuilding as well as a floor covering or cladding for a façade. Since 2012 the company has also been offering Resysta in compound form.
The aim of the product developers at Resysta was to optimise the deficiencies of timber in terms of watertight properties, resistance to rupturing and UV and to create an alternative to timber. What the company was looking for was a material that is to a major extent sustainable and which would make a definite contribution towards protecting tropical timber stocks. In order to conserve resources long-term, renewable raw materials would be used to manufacture the material Resysta.
Consisting of around 60% rice husks, approximately 22% rock salts and around 18% mineral oil, the items that go to make up the material are mainly natural raw materials. In association with polyvinyl chloride (PVC) the material is said to be up to 100% watertight. The rice husk assumes particular importance here. Designed by nature solely to protect the grain of rice from the ingress of water or attack by vermin, the scientists have transferred these capabilities to the quality of the Resysta surface. By recourse to an elaborate procedure using the custom-made “prior treated rice husk” (PTRH) technology the main ingredient, rice, is treated in such a way as to create a complete bond between it and the polymer. This enables the positive characteristics of the silicates contained in the husk to be retained.
Resysta is bipolar, that is to say, surface cross-linkage occurs in association with water, but the water is not allowed to penetrate the material. In addition to being weatherproof its positive characteristics also provide protection against insects and fungal infestation as well as resistance to rupturing. The use of rice husks means that any CO2 is absorbed and emission thus reduced. The thermoplastic material is fully recyclable and can be returned to the manufacturer for subsequent re-introduction into the production cycle and re-processing to form a new Resysta product.
Active Resysta Filler – ARF
For the first time a natural fibre has been successfully incorporated in a PVC compound that improves the characteristics in a number of areas. For this reason the master batch is also known as ARF (Active Resysta Filler). It incorporates the processed rice husk as well as all other additives and is supplied to the processing industry.
The material is produced in the form of powder or granulate ready for extrusion. At the moment three types are supplied: Resysta Standard, Resysta Modified Impact Resistance and Resysta Flame-Retardant (Class B1). The material is extruded and forced under pressure into a forming mould at the end of the production process, thereby making a range of different profiles possible. This opens the door to a wide range of different application possibilities using Resysta. After many years of trial installations all over the world, in the summer of 2007 furniture manufacturers MBM presented a collection of garden furniture made from Resysta for the first time and with this found a market waiting for them.
Building project with formable material
A new project undertaken by the architect Nguyen Lam Dihn in Vietnam shows above all the mouldability of the material and its high level of resistance to moisture and direct sunlight. Both of these are present to an enormous degree in Vietnam and the materials used must be able to withstand the resulting high levels of stress.
The fact that the material is infinitely mouldable using the extrusion process has been responsible for the pronounced curves on the external façade. The sub-structure is fabricated from steel; the façade elements have been directly screwed on to this and cemented in position.
As regards the floor configuration, the villa planners have opted for Resysta both inside and out. Resysta flooring has been laid both in the sauna area and on the terrace. In addition to being water-resistant, the use of the material is to be recommended due to its resistance to splintering and rupturing which makes the flooring suitable for walking on with bare feet. In total 300m2 of flooring and 300m2 of façade have been installed in the house.
The private villa Thuy Hang in H? Chí Minh City is intended to radiate modern naturalness and generate inspiration through the language of unconventional design. The construction project, originally planned to feature timber, ground to a halt here because it proved impossible to find a designer who worked with timber and was able to realise the planned façade with its distinctive curved shape along the lines indicated in the drawings. By way of an alternative, the composite material Resysta was suggested to the people responsible for the project and this turned out to be the convincing factor as far as the builders and the architect were concerned. The material is infinitely mouldable and this factor has made the pronounced curvatures on the external façade a reality. The sub-structure is made from steel and the façade elements are directly screwed on to it and cemented in position.
As regards the floor configuration, the villa’s planners have also opted for Resysta both internally and externally. Resysta flooring has been laid both in the sauna area and on the terrace. In addition to its water resistant properties, the use of the material is recommended due to its resistance to splintering and rupturing, factors which make the flooring suitable for walking on barefoot.
For Nguyen Lam Dihn, alongside all the practical aspects there was one particular consideration that tipped the scales as far as he was concerned: ”This timber-free material is sustainable and conserves resources. By using Resysta instead of timber the architect can do something to help preserve the tropical forests. And the long service life of this material leaves me convinced that I have constructed a house that meets modern ecological standards.”
A first at Bau 2013 was Resysta International's presentation of products manufactured in Resysta using the flat press process instead of the traditional extrusion process. This provides the added advantage of being able to launch on the market large-format as well as very thin sheets made from this material. Sheets are obtainable in 1.50mm thickness, up to a width of more than 2m and in variable lengths. In so doing the intention with the sheet material is primarily to implement lightweight construction solutions more easily and more effectively, because its density is said to be around 50% less than that of aluminium. According to the manufacturer, in addition to solid sheets made from solid material, sandwich structures with glass fibre, non-woven material, honeycomb or a hard foam core are possible.