Chemical modification of polyurethane for two-component injection molding

• Published in: Polymer engineering and science Vol. 42; no. 4; pp. 859 - 869
• Main Authors: Bräuer, M., Hupfer, B., Nagel, J., Lehmann, D.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.04.2002; Wiley Subscription Services; Society of Plastics Engineers, Inc; Blackwell Publishing Ltd
• Subjects: Applied sciences; Exact sciences and technology; Injection molding; Machinery and processing; Moulding; Plastics; Polymer industry, paints, wood; Polyurethanes; Technology of polymers; Thermoplastics; Viscosity; Polymer blends; Mechanical properties; Tensile property; Experimental study; Adhesion; Heterogeneous mixture; Polyurethane elastomer; Interface properties; Amide 6 polymer; Chemical modification; Organic diisocyanate; Injection molding; Compatibility; Rheological properties
• ISSN: 0032-3888; 1548-2634
• DOI: 10.1002/pen.10997

A thermoplastic polyurethane (TPU) was modified by reactive processing with 4,4′‐diphenylmethane diisocyanate (MDI). The use of this modified polyurethane was investigated for improved adhesion in composites with polyamide 6 (PA 6). Specimens were prepared by two‐component injection molding. With the modified polyurethane the tensile bond strength could be increased by about 50%. An insoluble and inseparable polyurethane residue on the PA 6 fracture surface found by ATR‐FTIR spectroscopy gave evidence of chemical bonding between PA 6 and TPU. Allophanate bonds were formed by the chemical modification. These groups functioned as an inert source of highly reactive isocyanate groups. Urea groups, the polyurethane chain were formed by the modification, too. These groups may improve the compatibility between the two components. A change in the morphology of the polyurethane was observed, which was caused by the change in molecular structure by the chemical modification. The high level of bond strength may be due to a combination of these phenomena.