Improved adhesion of silicone rubber to polyurethane by surface grafting

Abstract

Polyurethane (PU) has widespread applications in implantable devices because of its excellent mechanical and biocompatible properties, whereas weak biostability limits its long-term implantation. The introduction of silicone rubber (SR) onto the PU surface is an effective method for improving the biostability of PU, but the adhesion of these two polymers is unsatisfactory. In this study, the surface modification of PU via grafting through the introduction of vinyl and SiAH groups onto the PU surface was attempted to improve the adhesion of PU to SR. Fourier transform infrared, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy were employed to investigate the graft reaction on the PU surface.The interfacial and surface morphology was characterized with scanning electron microscopy. Different PU/SR interfaces after oscillation and shear were compared as well. The results indicated that the PU surface was activated by diisocyanate, which generated free isocyanate groups for the further grafting of vinyl and SiAH groups. When additiontype, room-temperature-vulcanized SR was poured onto the PU surface, the vinyl and SiAH groups on the PU surface underwent an addition reaction, which improved the adhesion of PU and SR by connecting them with chemical bonds.

Effect of different polyethers on surface and thermal properties of poly(urethane-siloxane) copolymers modified with side-chain siloxane

“…The formation of polyurethane was confirmed by the presence of chemical shift at 8.00 ppm in 1 H NMR spectrum Owens-Wendt model van Oss-Good model and 155 ppm in 13 C NMR spectrum which are attributed to proton 10 (-NHCOO-) and carbon 11 (-NHCOO-) in urethane bond respectively. There were no peaks at 124 ppm characteristic for the C atom in an isocyanate group which confirms that diisocyanate was completely reacted.…”

“…Chemical shifts derived from BD occur at 1.56-1.68 ppm assigned to protons (7) in -CH 2 -and at 4.06-4.19 ppm assigned to protons (6) in -CH 2 -OCONH-group. The shifts for carbons in above-mentioned groups are also reflected in 13 C NMR spectra. Especially, the signals at d = 25.72-28.06 and 70.61-75.37 ppm assigned to carbon (7) in -CH 2 -and (6) in -CH 2 -OCONH-groups, respectively, which are derived from BD.…”

“…Other characteristic IR bands present both in PU as well as PU-PDMS can be seen at around 1,035 and 1,097 cm -1 (-Si-O-Si-and/or -C-O-C-bending) and 2,795-2,968 cm -1 (C-H stretching). Interpretation of 1 H and 13 C NMR spectra of all poly(urethane-siloxane) copolymer is presented in Table 4, where the protons and carbons signals were assigned to the particular structural parts of the polyurethane chain [25]. The numbers of particular atoms were provided in Fig.…”

“…The cross-linked PU-Si revealed lowered water absorption. Wang et al [13] synthesized PU-PDMS copolymers by modification of PU surface via grafting through the introduction of vinyl and Si-H groups onto the PU surface to improve the adhesion of PU to silicone rubber.…”

Modelling the surface free energy parameters of polyurethane coats—part 1. Solvent-based coats obtained from linear polyurethane elastomers

“…However, bio-stability places limitations on the long-term use of such implants. Those applications are strictly controlled by the surface properties of the polymer material, inclusive of possible modifications of the surface free energy (SFE) value towards its reduction [1, 2]. The polyurethane material itself is a polar polymer with the SFE value exceeding 50 kJ/m 2 in many cases which makes it biodegradable and completely immiscible in practice with polyolefins, i.e.…”