the top layer and the bottom layer further the coating and wood board used in the tests can be prepared according to fig2 a wood board 4 is plywood particle board high or middle density fiberboard or some other pressed and glued board containing wood or other plant fibers if the signalling layer is not a polyolefin layer it must be so sparse that enough melt polymer material from the top layer can join to the bottom layer or it must be reactive with the maleated groups polyolefins here are polyethylene pe or polypropylene pp maleated polyolefin mape or mapp can be also used so that the top layers composition is pe pe pe mape or pp pp pe mape or pp tie pe mape when dissimilar polymers are co extruded a compatibiliser material is required in the signalling layer to join the dissimilar materials this layer is often referred to as a tie layer the maleated polyolefin contains normally 2 15 maleic acid of the amount of polyolefin at extrusion the maleic acid is converted to maleic anhydride partially or totally the polymer film can also be cross linkable if it in any case improves the use of the products the maleated films are pressed at temperature 120 170 u00b0 c to the wood surface and to the other films and layers it is important in order to include plastic melt flow that the hot pressing temperature is set to a temperature 20 50 u00b0 c above the melting temperature of the polymer the top layer can be cross linked by vinyl silane hydrolysis method or electron beam eb radiation.