HEAT-TRANSFER MODEL FOR THE COOLING OF HOT-MELT ADHESIVES

Results concerning the crystallization of a hot melt adhesive are pres ented. This adhesive was a liquid at high temperature (160 degrees C) and was deposited on a wood slab kept at ambient temperature. Cooling can be enhanced by circulating air above the adhesive. The temperature within the adhesive and the wood were measured versus time under thre e conditions: when the cooling of the upper external part of the adhes ive was due to free convection; when it was due to forced conviction ( to simulate the moving of the assembly line), and in the case where a second wood slab was placed to simulate a joint. It was observed that for a sufficiently thick: adhesive film the cooling was slowed down by hear transfer to the wood. A model combining the heat conduction and the kinetic law of crystallization is presented. This model permits th e prediction of the evolution of temperature at each point in the adhe sive or in the wood for different geometries. The beginning of the cry stallization at each point in the adhesive is also predicted. By knowi ng the rheological properties of the adhesive versus temperature, usin g the model giving the variation of temperature versus time, one can d etermine the variation of storage and loss moduli versus time.