Vulcanization of an IR/BR-copolymer using a CO2-laser as inline-curing method for additive manufacturing of rubber-based parts

The successful development of the Additive Manufacturing of Elastomers- (AME)-process for rubber-based elastomers also leads to new requirements for vulcanization. Until now, vulcanization of additively manufactured components has taken place separately from the 3D printer in an autoclave. However, since the component is not geometrically stable until it is vulcanized, the inline-vulcanization during printing appears to be a logical further step.

The aim is to integrate a CO2 laser into the printer. Previously, lasers have not been suitable for vulcanizing rubber because they only have a low penetration depth of less than 1 mm into rubber. However, since components are manufactured in layers with a thickness of currently 0.4 mm, vulcanization, or at least partly vulcanization, by laser seems possible, if the laser energy used does not cause polymer degradation. In the past, components had to be secured against flowing by a thermoplastic shell, this should be abandoned in future. Therefore, a sup-port structure as in the Fused Filament Fabrication- (FFF)-process will only be used for over-hangs.

The paper shows that crosslinking of an IR/BR-based sulphur-cured copolymer using a CO2 laser is possible. Therefore, thin squeegeed uncured rubber samples were laser treated and then exposed to the solvent toluene. Afterwards the solvent was filtered and the filtrate was examined thermogravimetrically. Cured elastomers were identified in the filtrate. In addition, it was possible to generate thin coherent elastomer films by repeated laser treatment of the samples. It was thus possible to demonstrate that integrating a CO2 laser into the 3D printer is technically feasible.