Effect of ultraviolet‐A radiation on surface structure, thermal, and mechanical and electrical properties of liquid silicone rubber

Abstract

Liquid silicone rubber (LSR) products outdoors are often subjected to high intensity of ultraviolet (UV)-A radiation. However, the influence of UV-A radiation on LSR is rarely studied. To study the influence of UV-A radiation on LSR, the surface of LSR with UV-A aging time was characterized by tests at different detection depths [X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR)]. The operation properties (thermal stability and mechanical and electrical properties) for outdoor insulators were also analyzed. It was found that the porous surface and the loose layer of LSR increased, but the growth rate of them decreased as UV-A aging time increased. SiO 2 fillers were lost in the surface. C H bonds in CH 3 and CH 3 in Si CH 3 increased with aging time. The increased crosslinking density increased the thermal stability, hardness, dielectric loss tangent, relative dielectric constant, and volume resistivity and decreased elongation-at-break. The mechanical strength initially increased and then decreased. Based on the proposed aging mechanism, the UV-A resistance of LSR can be improved by reducing the amount of hydrogencontaining silicone oil and by increasing the molecular weight of raw rubber.

Different Organic Peroxides that Cure Low‐k 1,2‐PB/SBS/EPDM Composites for High‐Frequency Substrate

“…Two approaches can scale down the value of D k and D f , namely the relatively high cross‐link density that hinders the movement of polar groups, and the reduction in the polarizability by forming a new C─C bond by cross‐linking reaction to replace the C═C double bond. [3,20,21] The change in the D k and D f value confirmed that the BIPB system is more reactive and can stimulate a relatively high degree of crosslink density compared with DCP. In summary, the 1,2‐PB/SBS/EPDM with 4 pbw BIPB showed excellent electrical properties, thereby indicating its feasibility as a high‐frequency substrate material.…”

“…Decreasing the polarizability[3,18,19] and increasing the cross‐link density[20–22] can reduce the dielectric constant and loss. Adding organic peroxide initiators to produce low polarity functional groups, such as C─C and C─H bonds, decreases D k and dielectric loss ( D f ).…”

A review of liquid silicone rubber injection molding: Process variables and process modeling

“…[ 3–5 ] Chemical reactions on the surface of LSR parts reduce the impact of UV radiation over time. [ 6 ] Silicone materials formulated for food [ 7 ] and medical [ 8 ] applications typically have relatively low volatile and leachable content. Silicone materials have been reported to cause a less significant foreign body response compared to many other soft implantable polymers.…”

Investigation of Hydrothermally Stressed Silicone Rubber/Silica Micro and Nanocomposite for the Coating High Voltage Insulation Applications

“…Despite these characteristics, SiR suffers from degradation in outdoor environments that needs to be addressed. The main drawback of polymeric insulators is their organic nature, which causes degradation of the structure under different environmental stresses such as UV light, fog, humidity, temperature, and acid rain [10][11][12][13]. The synergistic effect of these environmental stresses contributes to the deterioration of the physiochemical and thermomechanical properties of polymeric insulators.…”