Papers by Keyword: Polysiloxane

Abstract: One component room temperature vulcanized (RTV) silicone resin was prepared by combination of a kind of polydimethylsiloxane-b-phenylsilsesquioxane copolymer with crosslinker and catalyst. The effects of feeding order on properties of cured silicone resin were studied in detail. When hydroxyl terminated polydimethylsiloxane was added in three times and the D/T ratio was 2.0~2.3 during synthesis, the cured resin with the hardness over 20Shore D had the better elastic-plastic properties and heat resistance than the other two feeding orders. The tensile strength was over 3MPa and the elongation at break was above 75%. The T_d5% was 416.6°C.The silicone resin also had good radiation resistance. At the radiation dose of 1500kGy, there was no obvious defect observed in the material, and the tensile strength increased to 6.83MPa, while elongation at break decreased to 26%.

Abstract: The effect of fabrication methods on polysiloxane (POS) composites were studied by analysing both method of casting (CA) and compression (CO). The POS composites were reinforced with 2-12 wt% of natural derived silica from rice husk (RHA SiO₂) as a filler which incinerated at 700°C. The composites behaviour were analysed through tensile testing (ASTM D412). Through comparison study on both CA and CO composites’s tensile behaviour it shows that both composites strength keep increasing with 2wt% - 10wt% RHA SiO₂ addition but strength decreased at 12wt% due to agglomeration of RHA SiO₂. Moreover, it was found that the tensile strength of CO composites had offer 23.56% higher compared to CA composites. The difference were influenced by the distribution of RHA SiO₂ as filler. The surface morphology of CO composites had showed that the most of RHA SiO₂ were embedded and less agglomeration, compared to CA composites that had lots of agglomeration which lead to higher tendency of crack propagation. The arrangement of filler due to the CO method that helps RHA SiO₂ to distributed homogenously and embedded in a matrix of POS to avoid agglomeration and lead better adhesion respectively. Thus, CO method had potential to offer in enhancing tensile behaviour compared to CA method by influencing filler distribution arrangement for vibration absorber application.

Abstract: A series of aggregation-induced emission (AIE) active polysiloxanes (P7-1~P7-2, P29-1~P29-6) were prepared through hydrosilylation between polymethylhydrosiloxane (PMHS, DP=7 or 29) and AIE-active vinyl monomer 1-(4'-allyloxy-biphenyl)-2,5-diphenyl pyrrole (M-TPP), or with optical active monomer cholesteryl allyloxy ether (M-Chol^*). Monomer M-TPP and all of the polymers exhibits aggeragation-induced emission enhancement properties. The fluorescence intensity of M-TPP in THF/H₂O mixtures increases when the water fraction is higher than 60%, while is over 20% for polysiloxanes, which mainly because the entanglement of the flexible polysiloxane main-chain can restrict the molecular motion of triphenylpyrrole (TPP) derivates and induce the increasing of the fluorescence intensity. Moreover, the maximum relative fluorescence intensity (I/I₀) is equal to 4 for M-TPP and 1.4~4.9 for polysiloxanes, and the grafted degree of the TPP derivative has effect on the AIE properties of polymers. The specific optical rotations of the chiral polymers increase with increasing the content of chiral cholesteryl ether moieties. All the target polymers possess good thermal stabilities and their decomposition points (T_d) are greater than 320°C.

Abstract: One component room temperature vulcanized (RTV) silicone resin was prepared by combination of a kind of D-T polysiloxane block copolymer with crosslinker and catalyst. Transparent coating with good elastoplasticity without any inorganic filler could be obtained by exposing the RTV silicone to air at room temperature. The structure of D-T block copolymer played an important role in the properties of the cured products. It was synthesized by polycondensation of partially hydrolyzed phenyltrimethoxysilane (phenylsilsesquioxane, T units) with silanol end-capped polydimethylsiloxane (PDMS, D units). The effects of the viscosity of phenylsilsesquioxane and the D/T ratio on the properties of cured product were investigated. When phenylsilsesquioxane (10000cP at 80°C) was used and the D/T ratio was 2.0~2.3, cured products with tensile strength above 2.5MPa and elongation above 70% were prepared. RTV silicone resin composed of such kind of D-T block copolymer had good heat resistance because the existence of phenyl group and the highly cross-linked 3D structure. The T_onset was 387.6°C and the T_max was 518°C.

Abstract: A new generation of high performance polysiloxane white coating has been peeling off a large area after being applied on a special ship for 10 years, which has a great impact on the appearance of the hull. Based on the curing mechanism and physicochemical characteristics of acrylic polysiloxane coating, the reason of existing coating stripping was analyzed. Through a small range test, We can explore the method of coating repair.

Abstract: The pyrolysis process of polysiloxane resin conducted in the temperature range 400 – 700 °C results in hybrid materials owning some polymeric (thermosetting) behaviour. A certain level of elastic recovery and/or viscoelastic flow showed at various steps of pyrolytic transformation was monitored using the instrumented Vickers hardness method. Determined indentation force-indentation depth curves reflect the mechanical response and the level of the transformation; however, the relaxation behaviour is not covered by this method fully. An extensive indentation relaxation was revealed in the material partially pyrolysed at 400 °C, about 16 % and 8 % when the HV 0.1 and the HV 0.2 loading were applied, respectively. Materials pyrolysed from 500 to 650 °C which exhibited the indentation relaxation below 1 % and the mostly elastic response on the loading were observed. Above the pyrolysis temperature of 600 °C a rapid onset of mechanical properties, namely indentation elastic modulus and hardness, was observed. The short-term indentation relaxation was evaluated via the indentation force relaxation method in the regime of constant indentation depth obtained at the moment of reaching an initial force of 0.981 N or 1.962 N. The obtained indentation force relaxation curves were analysed on the basis of a logarithmic function. The significant effect of the pyrolysis temperature as well as the influence of loaded volume was described.

Abstract: The narrow particle size distribution of poly (vinyl silicone) microspheres were prepared by the hydrolysis-polycondensation method with vinyl silane (VTMS) as raw materials. And the influences of pH value, oil/water ratio on the morphology, particle size and distribution of the microspheres were studied. The results shows that the particle size of microspheres decrease with the increasing of the PH value of polymerization, and the particle size has no specific linear relationship with the PH value of hydrolysis reaction, while the oil-water ratio is smaller, single particle size distribution is more narrow, more uniform distribution.

Abstract: Polysiloxane resin copolymer was synthesized through acid catalyzed hydrolysis of methyl triethoxysilane (MTEOS) and diethoxytetramethyldisiloxane (DEOTMDS). The effect of reaction time on the properties of the polymer was studied and this copolymer was characterized by GPC, ²⁹Si NMR, IR, TGA, viscosity, refractive index, specific gravity and solid content. ²⁹Si NMR and IR showed characteristic signals of Si-O-Si linkage which confirmed the formation of the polymer. GPC and solid content analysis showed an increasing trend in molecular weight with reaction time. Thermo gravimetric analysis showed that the polymer was thermally stable upto ≈ 260°C and all the polymers gave a ceramic residue in the range of 77-80% at 900°C. Siloxane prepared inhouse and methyl phenyl silsequioxane (control) were used as coating materials and atomic oxygen (AO) resistance was evaluated on Al-Kapton, carbon polyimide composite and glass polyimide composite. The mass loss and surface morphology of the coated samples were measured at different time intervals. It is observed that mass loss of polysiloxane coated samples was very less, compared to coated control samples. The morphology of all the samples were studied using FESEM. Erosion kinetics and surface morphology investigation indicate that the polysiloxane coating possesses excellent AO resistance, and displays better cracking resistance on AO exposure.

Abstract: One of approaches to protect devices from unpleasant vibrating disturbances is by employing a vibration absorber. This paper explores the viability of polysiloxane as raw material, added with rice husk silica fillers to produce a vibration absorbent sheet. The polysiloxane reinforced with rice husk sheets were made using hot compression moulding technique. The samples were tested for its density and tensile tests according to related standards. As for vibration test, a portable hand grinder was used to estimate the vibration exposure experienced by the users. The polysiloxane sheets were strapped on the tool’s handle and the vibration exposure was measured. The result shows that by applying the polysiloxane sheets on the tool grinder reduces the vibration magnitude by a maximum value of 38 percents. The longest vibration time exposure was recorded for 6.42 hours, improved by 150 percents from the original vibration time exposure of 2.52 hours. The results also demonstrated that polysiloxane with 4 wt. % rice husk silica was the optimum combination for vibration application since it produced highest vibration magnitude reduction and longest vibration exposure time of grinder applications.

Abstract: Polyether-modified polysiloxane was synthesized by hydrosilylation, using allylic alcohol polyether and polysiloxane as materials, toluene as solvent and chloroplatinic as catalyst. The effect of technology conditions on conversion rate of hydrogenous silicone oil was discussed and chemical structure of product was characterized. The results show that the optimum technology is: the reaction temperature is 95°C, time is 5h, the molar ratio of polysiloxane to polyether is 1:1.2, the dosage of catalyst is 30ug/g and the mass fraction of the toluene is 25% of the system.