Properties Of Silicone Rubber Research Articles

Preparation and Property Study of Organosilicon Antisticking Coatings

In this article, an organosilicon antisticking coating was synthesized from vinyl silicone oil, hydrogen‐containing silicone oil, and platinum catalyst. Firstly, the methyl vinyl MQ (mono and quad) silicone resin was added. When the silicone content was 30 wt.%, the shore hardness and tensile strength increased to about 27.4% and 115.9%, respectively. Furthermore, nano‐SiO2 powder was added to further improve its antisticking property. This was due to the change of the surface roughness, which could greatly improve the antisticking performance. When the nano‐SiO2 powder content was 2 wt.%, the surface free energy and antisticking force were the lowest and the antisticking effect was the best as well and the mechanical properties of silicone rubber had been improved.

Engineered Chemical Nanotopographies: Reversible Addition-Fragmentation Chain-Transfer Mediated Grafting of Anisotropic Poly(acrylamide) Patterns on Poly(dimethylsiloxane) To Modulate Marine Biofouling.

Effectively negating the deleterious impact of marine biofouling on the world's maritime fleet in an environmentally conscientious manner presents a difficult challenge due to a variety of factors including the complexity and diversity of fouling species and the differing surface adhesion strategies. Understanding how surface properties relate to biofouling can inform and guide the development of new antibiofouling coatings to address this challenge. Herein, we report on the development of a living photopolymerization strategy used to tailor the surface properties of silicone rubber using controlled anisotropic poly(acrylamide) patterns and the resulting antibiofouling efficacy of these surfaces against zoospores of the model marine fouling organism, Ulva linza. Chemical patterns were fabricated using reversible addition-fragmentation chain-transfer (RAFT) livingpolymerization in conjunction with photolithography.Pattern geometries wereinspired by the physical (i.e., nonchemical) Sharklet engineered microtopography system that has been shown to be effective against the same model organism. Sharklet chemical patterns and analogous parallel channels were fabricated in sizes ranging from 2 to 10 μm in the lateral dimension with tailorable feature heights ranging from tens to hundreds of nanometers. Nonpatterned, chemically grafted poly(acrylamide) silicone surfaces inhibited algal spore attachment density by 59% compared to the silicone control; however, attachment density onchemical nanotopographies was not statistically different from the control. While these results indicate that the chemical nanotopographies chosen do not represent an effective antibiofouling coating, it was found that the Sharklet pattern geometry, when sized below the 5 μm critical attachment size of the spores, significantly reduced the algal spore density compared to the equally sized channel geometry. These results indicate that specific chemical geometry of the proper sizing can impact the behavior of the algal spores and could be used to further study the mechanistic behavior of biofouling organisms.

Wear-Resistant Graphene–Silicone Rubber Composites

Both the mechanical properties and friction characterization of graphene–silicone rubber composites were investigated systemically. Graphene–silicone rubber composites were prepared by means of solution and flocculation process to improve the processing performance and avoid agglomeration. It was found that the tensile strength, elongation at break, and tear strength of graphene–silicone rubber composites with 2.0% graphene were respectively 32.8, 21.1, and 23.5% higher than those for pure rubber. Both the friction coefficient and the abrasion loss of silicone rubber composites of 0.75 wt% graphene were 50.6 and 72.8% lower than those for the pure specimen. The microscopic fracture and friction mechanism of graphene–silicone rubber composites were analyzed, which indicated that both the wear resistance and mechanical properties of silicone rubber were influenced by the lubrication, reinforcement, and agglomeration of graphene. These results will play an important role in the design and evaluation of the friction and wear properties of graphene–silicone rubber composites.

Computational Simulation on Facial Expressions Using Finite Element Analysis

The purposes of this research are to identify mechanical properties of silicone rubber used as artificial skin and perform computational simulation on facial expressions using Finite Element Analysis (FEA). The tensile test was carried out to find mechanical properties of silicone rubber. Calculations on facial expressions were carried out using the mechanical properties of artificial skin of silicone rubber identified by the tensile test.

팽윤에 의한 실리콘 고무 특성 변화에 관한 연구

팽윤에 의한 실리콘 고무 특성 변화에 관한 연구

Improving mechanical properties of silicone rubber for use as outdoor insulator sheds by manipulating matrix-filler interfacial compatibility

Interfacial compatibility and particles dispersion are two vital influences for improving mechanical properties of silicone rubber (SR) nanocomposites. To achieve a high level of compatibility with SR-matrix, a series of dispersible nanosilica (denoted as DNS) surface modified with hexamethyldisilazane (HMDS) as well as aluminum hydroxide modified with stearic acid (denoted as m-ATH) were synthesized and used as reinforcement fillers of SR-matrix nanocomposites. Results indicate that the compatibility can be obviously improved by modification of fillers. DNS surface-capped with 0.1 mol l−1 HMDS and m-ATH surface-modified with 0.1 wt% stearic acid exhibit excellent reinforcement effect. Compared with unmodified samples, the tear strength and elongation at break have been improved by 68.5% and 171.2%, respectively. Moreover, the as-fabricated DNS/m-ATH nanocomposite exhibits a tracking-erosion resistance of 1 A 4.5–0.83, a volume resistivity of 1.0 × 1015 Ω·cm and a dielectric constant of up to 3.51, which are all much higher than the standards of high voltage insulator sheds. This indicates that the as-fabricated SR-matrix nanocomposite could be a qualified candidate material for high voltage insulator sheds.

Using α-Pinene-Modified Triethoxysilane as the New Cross-Linking Agent To Improve the Silicone Rubber Properties.

α-Pinene-modified triethoxysilane (α-PTES) was synthesized by hydrosilylation in the presence of Karstedt’s catalyst. The structure of α-PTES was determined by Fourier transform infrared spectroscopy and nuclear magnetic resonance. Under the catalysis of an organotin catalyst, α-PTES, which was the cross-linking agent, and the hydroxy-terminated poly(dimethylsiloxane) matrix were utilized to prepare the room-temperature vulcanized silicone rubber. Morphology, thermal performance, and mechanical properties of the modified silicone rubber were investigated by scanning electron microscopy, thermal gravimetric analysis, dynamic mechanical analysis, and a universal testing machine. Because of the strong rigidity of the ring structure of α-pinene, the thermal and mechanical properties of modified silicone rubber were improved greatly than those of the silicone rubber, and the cross-linking agent of which was methyltriethoxysilane. Results showed that the tensile strength and the break at elongation increased by 69.2 and 125%, respectively, and they are nearly doubled compared to the unmodified silicone rubber.

Acidic-Thermal Ageing Effect on Compression Stress Relaxation of Silicone Rubber

The compression properties of silicone rubbers used as gaskets in PEM fuel cells are studied. The specimens are aged under different test conditions, viz, high temperature, humid air, and acidic solutions, prepared to match real PEM fuel cell operation conditions. The compression and stress relaxation tests are conducted. Temperature, humid air and acidic solution exert a serious effects on the mechanical performance of silicone rubbers. All the three factors can cause an increase in the stress relaxation modulus and permanent compression deformation. The effects of high temperature and an acidic solution are more pronounced. This can accelerate the deterioration of mechanical properties and decrease the sealing efficiency of gaskets, which would influence the durability of PEM fuel cells. It creates the basis for life prediction of silicone rubbers under appropriate accelerated durability test conditions.

Nonlinear conductivity and charge transport characteristics of silicone rubber/SiC composites under impulse superimposed on DC voltage

Nonlinear conductivity composites can be applied to modify the local electric field distribution and accelerate the surface and space charge dissipation in HVDC cables. This paper focuses on the effect of the nonlinear conductivity on the charge transportation under impulse superimposed on DC voltage. The surface-charge-accumulation property of silicone rubber (SiR)/SiC composites under impulse superimposed on DC voltage is studied. The surface potential decay (SPD) is measured after the sample is stressed by impulse superimposed on DC voltage. The effect of nonlinear conductivity on carrier mobility is analyzed. The results show that under DC voltage, the decay rate increases for the rise in the initial surface potential (ISP). Higher surface potential caused by higher impulse voltage leads to a larger nonlinear conductivity, which immediately dissipates the surface charge. The increase in DC voltage is shown to be more effective in accumulating surface charge than impulse. The vertical movement to the ground and the horizontal movement of surface charges are two factors affecting the ISP and SPD, which are both affected by the nonlinear conductivity of SiR/SiC composites.

Preparation of a novel type of flame retardant diatomite and its application in silicone rubber composites

A novel strategy was used for preparation of flame retardant based on biomass debris to improve the flame retardant property of silicone rubber (SR). [(6-oxido-6H-dibenz[c,e][1,2]oxaphosphorin-6-yl)methyl]butanedioic acid (DDP) was used to modify diatomite by esterification method, and DDP@diatomite was obtained. The structure and morphology of this novel additive was identified using Fourier transform infrared spectroscopy (FTIR), Brunner-Emmet-Teller (BET) measurements, and X-ray photoelectron spectroscopy (XPS) together with scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS) techniques. Thermogravimetric (TG) analysis was performed to evaluate the thermal degradation behaviors of diatomite and DDP@diatomite. This novel additive was applied into silicone rubber (SR) composites. Combustion parameters, including heat release rate (HRR), total heat release (THR), smoke production rate (SPR), carbon monoxide (CO), peak smoke production rate (PSPR), peak carbon monoxide (PCO) and vertical burning time, were characterized by cone calorimeter and vertical burning tests. Results indicated that this flame retardant can reduce fire risk and toxicity effectively. TG and X-ray diffraction (XRD) patterns of SR and its composites were also investigated. The inexpensive property of modified diatomite could also expand its fire safe applications.

Radiation synthesis of polysilane‐modified graphene oxide for improving thermal conductivity and mechanical properties of silicone rubber

ABSTRACTFunctionalized graphene oxide (named GO‐Si) was synthesized with graphene oxide and triethoxyvinylsilane (TEVS) using tetrahydrofuran solution by γ‐ray irradiation. TEVS was successfully covered onto GO sheets, and the polysilane content on GO‐Si was increased upon increasing the absorbed dose. The structures of GO‐Si were verified by atomic force microscopy, Fourier transform infrared spectroscopy, and X‐ray photoelectron spectroscopy. The resultant GO‐Si was dispersed into α,ω‐dihydroxypolydimethylsiloxane to prepare room temperature vulcanized silicone rubber composites (named SR/GO‐Si) by solution casting. The dispersion of GO‐Si was more uniform than that of GO. Compared to that of pure SR, the thermal conductivity of SR/GO‐Si‐1.95 composites was increased 1.5‐fold, and its tensile strength and elongation at break increased 78.6 and 71.4%, respectively. It was expected that SR/GO‐Si would have potential application as the thermal interface material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47776.

Globally reinforced mechanical, electrical, and thermal properties of nonlinear conductivity composites by surface treatment of varistor microspheres

The composite filled with zinc oxide (ZnO) varistor microspheres display promising nonlinear conductivity properties and can be used for grading electric field in electrical equipment. However, the mechanical properties of composites containing ZnO varistor microspheres are seriously degraded, so how to balance the mechanical and electrical performances of electric field grading materials is a key issue for practical applications. In this work, concurrent reinforcement effect of surface-treated ZnO varistor microspheres on the mechanical, electrical, and thermal properties of silicone rubber (SR) composites are studied. 3-Aminopropyltriethoxysilane, a silane coupling agent, is used for surface functionalization of ZnO varistor microspheres, which are then used as a filler in SR to prepare an electric field grading material. Mechanical tensile tests reveal that the tensile strength and initial modulus of the composite incorporated with surface-treated filler are markedly improved and the thermal conductivity of this composite is also increased compared with a composite with untreated filler. Meanwhile, the composites with surface-treated filler displays more stable nonlinear electrical properties under mechanical deformation than those with untreated filler. This method would lead to electric field grading composite materials with excellent comprehensive properties towards practical applications in cable insulation, insulators, terminal accessories, etc.

Rhodium(I)-catalysed cross-linking of polysiloxanes conducted at room temperature

Acetylacetonate and 4-arylimino-2-pentanonate carbonyl complexes of rhodium(I) [Rh(RC(O)C(R')C(O)R“)(CO)2] (1: R = Me, R' = H, R'' = Me; 2: R = Me, R' = Cl, R'' = Me; 3: R = Me, R' = H, R'' = CO2Me; 4: R = Ph, R' = H, R'' = Me; 5: R = Ph, R' = H, R'' = Ph) and [Rh(MeC(NR''')CHC(O)Me)(CO)2] (6: R''' = Ph; 7: R''' = 2,6-Me2C6H3) were examined as hydrosilylation cross-linking catalysts at RT for the reaction of poly(dimethylsiloxane-co-ethylhydrosiloxane) copolymer with vinyl terminated poly(dimethylsiloxane) or vinyl terminated poly(dimethylsiloxane-co-styrene) copolymer. All complexes allow cross-linking of vinyl- and hydride-containing polysiloxanes and copolymers at RT without inhibitor addition. Complexes 1–7 possess catalytic activity comparable to the industrially used complex of Pt0 and divinyltetramethyldisiloxane (Karstedt’s catalyst). 1 is the most active among the studied rhodium complexes at 1.0 × 10−4 mol⋅L−1 and 1.0 × 10−5 mol⋅L−1. Silicone rubbers obtained with the rhodium catalysts compared to Karstedt’s catalyst possess no visible defects (bubbles or cracks), and differed by improved elastic properties (the elongation at break increased from 160 to 255%) The activity and improved silicone rubber properties using 1 renders it one of the suitable alternatives to Karstedt’s catalyst.

Swelling behaviour and morphological analysis of Arenga pinnata–silicone biocomposite

Swelling behaviour and morphological characteristics of Arenga pinnata–silicone biocomposite (APSil) after swelling test were investigated and compared to pure silicone rubber (0 wt%). Results indicate that the highest filler addition (16 wt%) possess the lowest swelling rate followed by 8 wt% and 0 wt% specimens. The nature of fibre/matrix interface of the swelled samples was examined through scanning electron microscope. Addition of Arenga pinnata (AP) filler in silicone rubber shows less crack propagation in comparison to without filler. Thus, it can be concluded that the addition of AP filler improves the swelling properties of silicone rubber which makes it a good candidate for sealing application.

Characterization of Silicone Rubber Degradation Under Salt-Fog Environment With AC Test Voltage

In recent years, some composite insulators operating in coastal foggy areas have shown different levels of degradation phenomena. This paper presents several performances and properties of silicone rubber under the salt-fog environment with AC voltage. Analysis conducted after salt-fog treatment by techniques, such as static contact angle, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), dielectric parameter, and flashover voltage show a significant degradation of samples. The absorption peak of the hydrophobic groups (Si-(CH3)2 and Si-CH3) decreased, the surface of the material became rough, and the dielectric and electrical properties were also deteriorated. Due to the thermal effects and impact of high-energy particles, the molecular chains on the surface of silicone rubber were broken, and the smooth surface structure was destroyed, resulting in the formation of hydrophilic chemical bonds and precipitation of inorganic substances. The intrusion of moisture further reduces the dielectric parameters and the electrical strength of the material. In addition, the samples in the salt-fog environment with a greater conductivity are more degraded, indicating that the salt-fog has an aggravating effect on the aging of the silicone rubber. Thus, it is recommended to pay attention to the monitoring and examining the work of composite insulators operating in a foggy and high humidity environment.

Effect and mechanism of hepta-phenyl vinyl polyhedral oligomeric silsesquioxane on the flame retardancy of silicone rubber

It is challenging to simultaneously improve the flame retardancy and mechanical properties of silicone rubber. We herein proposed an efficient method to address this issue by incorporating hepta-phenyl vinyl polyhedral oligomeric silsesquioxane (HPVPOSS) into addition-cure liquid silicone rubber (ALSR). HPVPOSS meanwhile enhanced the flame retardancy and thermal stability of ALSR. With the addition of 10 phr HPVPOSS, ALSR passed the V-0 rating in the vertical burning test (UL-94) and had a limiting oxygen index (LOI) value as high as 31.0%. Moreover, compared with ALSR, the peak heat release rate and total heat release were decreased by 31.8% and 28.7%, respectively. Besides, the ALSR/HPVPOSS nanocomposites were demonstrated to have excellent mechanical properties. The possible flame retardant mechanism of HPVPOSS, which was attributed to the free-radical quenching effect and the catalysis effect on the crosslinking charring of ALSR, was further revealed. By generating the rigid core free-radicals and phenyl free-radicals, HPVPOSS suppressed the thermal degradation of ALSR in the condensed phase and quenched the active free-radicals in the gas phase. Moreover, HPVPOSS promoted the crosslinking charring of ALSR and the formation of a compact ceramic protection layer on the ALSR surface, effectively hindering the heat transfer and oxygen diffusion. Our findings provided a new way to fabricate silicone rubber with prominent flame retardancy and outstanding mechanical properties.

Measurement of a Nearly Friction-Free Stress–Strain Curve of Silicone Rubber up to a Large Strain in Compression Testing

Nominal stress–strain curves of a silicone rubber specimen with a range of length-to-diameter (L/D) ratios have been measured via compression testing. The curves are highly dependent on the L/D ratio. The contact area has been measured using stamp ink applied to the sidewall of the specimen to determine the optimal L/D ratio which yields the stress–strain curve closest to the curve of the friction-free specimen. Traces of ink appear on the platen after the compression test, indicating that the phenomenon of rollover takes place. When the L/D ratio is less than 1.0, the contact area is less than that of the friction-free specimen although the phenomenon of rollover supplements the contact area. When the L/D ratio increases up to 1.0, the contact area increases toward that of the ideal specimen that deforms uniformly under the friction-free condition; the stress–strain curve of the specimen with the L/D ratio of 1.0 can be regarded as the nearly friction-free property of silicone rubber.

Study on artificial multi‐stress ageing characteristics of composite insulators

In recent years, abnormal heating of composite insulators has become a serious problem, especially in the coastal areas of southern China. In this paper, an improved multi-stress aging test for composite insulators was proposed based on the environment of the coastal areas in southern China, and 5000 h aging test was carried out. The test results showed that the wet flash-over voltage decreased linearly, while the hydrophobicity of the shed showed a nonlinear aging characteristics, whose change rate increased gradually. The multi-stress aging condition had little influence on shed hardness for the change of the shed hardness remained within 1%. The aged composite insulator showed significant temperature rise and the temperature rise concentrated on the high voltage end at high humidity, while it showed little temperature rise at low humidity. The dielectric loss of silicone rubber after moisture absorption was tested. It could effectively reflect the moisture absorption characteristics and the dielectric properties of silicone rubber after moisture absorption, and was closely related to the wet flash-over voltage and temperature rise of the composite insulator. The dielectric loss of silicone rubber after moisture absorption could be used as a new method to evaluate the operating state of composite insulators.

Characteristics of Silicone Composites for High Voltage Insulations

AbstractSilicone rubber (SiR) composites have been widely used for high voltage (HV) electrical and non-electrical applications for the last three decades. To increase the long-term performance of SiR composites under diverse environmental, mechanical and electrical stresses; detailed characterization and aging analysis is required. This review article presents a comprehensive survey on SiR composites that are used in HV applications. Particular emphasis is on silicon (Si) applications, chemistry, polymerization, silicone rubber properties enhancement by addition of fillers, composite materials, engineering requirements of polymer insulants, overview of high voltage (HV) electrical insulators and their aging. In addition, this review article includes appropriate discussions concerning the influence of fillers (micro/nano-sized) on the physical, thermal, mechanical and electrical properties of base polymer. Tensile strength, elongation at break, hardness, thermal degradation, dielectric strength, surface resistivity, volume resistivity, tracking/erosion resistance, partial discharge and water immersion resistance of SiR composites are analyzed. Finally, it was inferred that in order to diversify the SiR blends with micro/nano fillers and optimize their properties for particular applications further research work must be conducted.

Amine-functionalized POSS as cross-linkers of polysiloxane containing γ-chloropropyl groups for preparing heat-curable silicone rubber

A series of heat-curable silicone rubber is designed and prepared through cross-linking reaction of two structurally similar amine-functionalized polyhedral oligosilsesquioxane (POSS), octa(aminophenyl)silsesquioxane, and N-phenylaminomethylsilsesquioxane, with polysiloxane containing γ-chloropropyl groups (CPPS). Curing characteristics measured with a rheometer show that the amine-functionalized POSS can participate in chemical cross-linking during curing. Scanning electron micrographs illustrate that silicone rubber prepared by solution mixing exhibits a homogeneous morphology. Mechanical and thermal properties of silicone rubber are evaluated through mechanical testing, thermogravimetric analysis, and differential scanning calorimetry. The effect of POSS distribution in the polymer matrix on vulcanizate properties is discussed. Compared with that prepared through melt mixing, the methyl chloropropyl silicone rubber prepared through solution mixing exhibits excellent mechanical properties. Concentrative cross-linking occurs in this network, and the mechanical properties are improved. The sample exhibits a tensile strength of 9.9 MPa and tear strength of 48.1 kN/m. Thermogravimetric analytical results show that introducing POSS can enhance the thermal stability of silicone rubber.