UV‐sealant characterization for automotive applications

Abstract

This project is focused on acrylate derivative resins for automotive adhesives and sealants applications. The acrylic terpolymers are synthesized via an innovative process called SET‐LRP (Single Electron Transfer – Living Radical Polymerization). Adhesives and sealants manufacturers commonly employ just one single resin as the backbone of their formulations. The novelty is to experiment with blends of resins to improve the performances of the final commercial product. This work has studied the impact of the functionality (mono‐, di‐, tri‐), molecular weight (10K g/mol to 30K g/mol), and bimodality (MW and functionality mixture) on compression set, tensile strength and elongation at break, compressive stress relaxation, and storage modulus as well as the impact on glass transition temperature in well‐defined blends of acrylate polymers prepared by both ATRP (Atom Transfer Radical Polymerization) and SET‐LRP processes. It is well‐known that resins for automotive applications need an oil resistant monomer (ORM1) in their composition to protect the material from the attack of the lubricant oil during their work life. However, neither its role nor its efficiency is very well understood. In this project, the influence of the different proportions of this oil resistant monomer (0%, 2.5%, 5%, 7%) in single heteropolymers based on acrylate derivatives has also been studied. Compression set, tensile strength and elongation at break, oil resistance, storage modulus and glass transition temperature have been used to investigate the true role of this monomer in the resin composition. Analogous investigations were undertaken on blends of terpolymers based on acrylate derivatives varying the total amount of the ORM1 (3.5%, 5%) in the resin blends. The same experimental techniques were used to characterize the influence of this monomer in the resin blends. Attention was also paid to the type of capping in both resin blends. In one blend, the resin was capped with acrylate and the other contained both acrylate‐ and methacrylate‐capped resins. The fact is that the need for the ORM1 in the composition was not clear enough in light of its toxicity and irritant status. An idea was to replace this monomer by another oil resistant monomer (ORM2) which is an irritant but does not carry a “Toxic” label. Several experiments were performed using a single copolymer resin without ORM1 in the backbone, but introducing ORM2 as diluent/reactive monomer. A comparison with the same resin, but with dimethylacrylamide as a diluent monomer, which is habitual in the practice, was also done. Also in this experiment compression set, tensile strength and elongation at break, storage modulus as well as glass transition temperature were studied.