A new cross‐linked system of silicone rubber based on silicone‐polyurea block copolymer

Abstract

A new cross‐linked system of silicone rubber (SR) was obtained from silicone‐polyurea block copolymers that was synthesized with aminopropyl terminated polydimethylsiloxane and (4‐isocyanatocyclohexyl)‐methane. SR possessed self‐reinforced and physical cross‐linked structure. It had better mechanical properties that the hardness, the tensile strength, and the elongation at break could reach 65 Shore A, 3.78 MPa, and 458% with the polyurea segment content ranging from 2.01% to 9.13% by weight. The hydrogen bond that led to the physical cross‐linked structure was proved byFourier transform infrared spectroscopy. The microphase separated structure that caused the self‐reinforcement was illustrated by scanning electron microscopy, X‐ray diffraction analysis, and dynamic mechanical analysis. Fourier transform infrared spectroscopy results showed the hydrogen bond formation between the polyurea units. Scanning electron microscopy, dynamic mechanical analysis, and X‐ray diffraction analysis results proved the microphase separation existed between polyurea units and ―Si―O―Si― chains. The increase of polyurea contents enhanced the binding of hydrogen bond and improved the extent of microphase separation. Accordingly, it decreased the thermal properties and lowered the glass transition temperature (Tg) from −108°C to −114°C. Also, the increase of polyurea contents increased the hydrophobicity of SR that the surface free energy could reach to −24.81 mN/m.

Polyurea–Cellulose Composite Aerogel Fibers with Superior Strength, Hydrophobicity, and Thermal Insulation via a Secondary Molding Strategy

“…Besides, the N−H bending vibration (1400 cm −1 ) belonging to the urea group appeared in the CAFs, but its position was slightly shifted compared with the N−H bending vibration (1540 cm −1 ) on the urea group in polyurea. 45,46 Additionally, the O− H stretching vibration corresponding to the BC matrix at 3350 cm −1 , however, with the increase of polyurea content in CAFs, gradually disappeared. 47 Based on SEM image analysis of CAFs, it could be concluded that −NCO contained in polyurea could react with −OH in the BC matrix, leading to the tight coating of polyurea nanoparticles on BC nanofibers and contributing to the hydrophobicity of CAFs (Figure 1g).…”

A medical waste X-ray film based triboelectric nanogenerator for self-powered devices, sensors, and smart buildings

“…1(i), which matches the silicone rubber XRD pattern documented in the literature. 51–53 The diffraction maxima at 22.3° and 12.2° are attributed to the –Si–O–Si– amorphous phase and the polyurea units, respectively.…”

Polyurea for Blast and Impact Protection: A Review

“…The mechanical properties of polyurea can be tuned by choosing different variations of diamines and diisocyanates as well as by adding assorted nano-inclusions and micro-inclusions to create polyurea-based composites [5,66,67]. Nano-inclusions and micro-inclusions dispersed in the matrix can also improve the interfacial strength of the material, resulting in some enhancement [68].…”