HOT-MELT ADHESIVES HAVE PROCESS ADVANTAGES OF RAPID PLACEMENT AND FAST HARDENING. THEY CAN BE USEFUL AS HEADLAMP ADHESIVE/SEALANTS WHERE THE MELT TEMPERATURE IS MATCHED TO HEADLAMP TEMPERATURE. SUPERIOR HOT-MELT ADHESIVES HAVE BEEN DEVELOPED FOR ASSEMBLY OF POLYCARBONATE LENSES TO POLYPROPYLENE REFLECTORS. THE UNSTICKABLE POLYPROPYLENE WAS BONDED WELL. BOTH BOND STRENGTH AND HIGH-TEMPERATURE PERFORMANCE (120 DEGREES C) WERE SATISFACTORY FOR THIS APPLICATION. WEATHEROMETER TESTS FOR 1000 HOURS HAD LITTLE EFFECT. BOND STRENGTH (ASTM D1002) WAS IN THE REGION OF 200 TO 360 PSI (1.3 TO 2.5 MPA) AND SHEAR STRETCH OF 0.010 BOND LINES WAS UP TO 0.3 DEFLECTION. CROSSLINKING DURING AGING AT 120 DEGREES C WAS APPARENT IN SOME FORMULATIONS.
