36 at the opposite side 38 thereof the web of material 40 passes through the housing 30 from inlet to outlet the web may proceed from a pile of plaited web material 42 over the tensioning roller assembly 44 and the rollers 46 47 and 48 into the inlet 32 as this apparatus may be applied in combination with a printing machine such as that illustrated in fig4 the web material may come directly from a printing machine or from a dryer and may come plaited or straight or may arrive in batches inside the housing 30 nearer the top thereof is the web heating up zone in this zone the web 40 moves over the stationary tray 52 and onto the endless conveyor belt 54 which passes about the rollers 56 and 58 which stretch the belt 54 taut the web is brought to the desired temperature in the course of its two passes through the heating up zone one along the upper run of the belt 54 and one along the lower run of the belt 54 the web is immediately thereafter fed over the redirecting roller 60 from which the web then travels to the polymerization zone described.