Heat‐Resistant Strong Adhesive Consisting of Aromatic Polyamide With an Acid‐Removable <i>N</i>‐Protecting Group and a Thermal Acid Generator

ABSTRACT We present a heat‐resistant strong adhesive system consisting of aromatic polyamide substituted with N ‐ tert ‐butoxycarbonyl (Boc) groups, synthesized by polycondensation of bis(4‐Boc‐aminophenyl) ether ( 1 ) and isophthaloyl chloride ( 2 ), together with a thermal acid generator (TAG). Upon heating, the Boc groups are readily removed by the TAG‐generated acid, affording N ‐H polyamide. Adhesion was conducted at 150°C or 250°C under a pressure of 10 kgf/cm 2 for 7 h to eliminate voids due to Boc‐derived gaseous CO 2 and isobutene. For metal adherends treated at 150°C, the adhesion strength was 2–3 MPa. However, upon treatment at 250°C, above the T g of N ‐H polyamide (236°C), the adhesion strength reached 7.43–6.25 MPa for sandblasted steel plate, cold commercial (SPCC) and stainless steel. Next, we prepared copolyamides with lower T g values from 1 , bis(4‐methylaminophenyl) ether ( 3 ), and 2 . Upon treatment at 150°C, the adhesion strength of SPCC with copolyamide consisting of 30% 1 and 70% 3 reached 6.83 MPa. As regards heat resistance, SPCC treated with N ‐Boc polyamide/TAG at 250°C maintained an adhesion strength of 7.0–7.5 MPa from room temperature to 250°C, whereas SPCC treated with copolyamide/TAG at 150°C maintained an adhesion strength of 6.8–8.2 MPa up to 200°C.