Influence of the temperature profile in the interface on the bond strength of polyamide–polyurethane two‐component tensile bars

Two‐component tensile bars with polyamide 6 (PA) and thermoplastic polyurethane (TPU) unmodified and modified with 4,4′‐diphenylmethane diisocyanate (MDI) have been investigated. It is known that the bond strength of PA/TPU tensile bars can increase by about 50% if MDI‐modified polyurethane is applied. The subject of these studies is the analysis of the influence of the mass temperatures on the bond strength. The mass temperatures of the first and second injection process and the delay time between the first and second injection processes determine the temperature gradient in the interface at the moment of the second injection. There is an increase in the bond strength when there is an increasing temperature gradient; therefore, the mass temperature of the first component at the delay time has to be lower than the mass temperature of the second component. The temperature gradient can be used as a measure of the thermal annealing of the first component near the interface during the heat transfer from the second component. It can be concluded that effective thermal annealing causes an increase in the bond strength. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4297–4305, 2006