UV Surface Treatment of Polycarbonate for Ad-hesion Improvement to Liquid Silicone Rubber (LSR)

Abstract

The adhesion of self-adhesive liquid silicone rubbers to thermoplasts is only possible for a few selected material combinations without a surface pretreatment. A UV pretreatment is effective for polycarbonate and short irradiation periods are sufficient. To clarify the required irradiation conditions that result in an improvement of adhesion, the varying irradiation conditions were assessed. FTIR-ATR spectroscopy was used for surface analysis to characterize the change in the polymer surface.

MC-Injection Molding with Liquid Silicone Rubber (LSR) and Acrylonitrile Butadiene Styrene (ABS) for Medical Technology

“…Similar to other activation methods, the degradation of the crosslinker in silicone components during artificial aging also plays a role in diminishing adhesive properties [23,24]. Additionally, it could be postulated that the radicals generated from UVC irradiation form more robust bonds with the silicone components, resulting in more stable properties against temperature and humidity [18]. As a result of sterilization, the values for both thermoplastics also dropped (Figur 9).…”

“…Simultaneously, a decrease in the region corresponding to the two unsaturated bonds, trans-1,4 (967 cm −1 ) and vinyl-1,2 (911 cm −1 ) C=C, was evident as the UVC irradiation time increased [15][16][17]. The nitrile, aromatic, and aliphatic groups appeared to be less impacted due to the higher binding energy of the C≡N bond, which exceeds the energy of UVC irradiation [18].…”

UVC Irradiation as a Surface Treatment of Polycarbonate to Generate Adhesion to Liquid Silicone Rubber in an Overmolding Process

“…In general, high-energy electromagnetic radiation can generate new functional groups on the surface of the polycarbonate, which have a positive effect on wettability and adhesion [ 10 , 11 , 12 , 13 ]. Our studies [ 14 ] showed that UVC irradiation of polycarbonate can generate a strong adhesion to standard self-adhesive LSR where initially there is none. It was found that the effect of adhesion promotion when using ozone-generating UVC lamps depends on the irradiation dose, which must be slightly higher with increasing irradiation distance.…”