Thermal stability and mechanical properties of room temperature vulcanized silicone rubbers

Based on much of the importance of RTV on the field of self-cleaning application for its nontoxic, tasteless, and thermal stability, the effects of D₄-SiO₂ on mechanical properties, Al(OH)₃ and decabromodiphenyl oxide ethyl(DBDPE) on flame retardant property of RTV matrix were investigated firstly. Then, a new kind of complex fire retardants was compounded. The morphology of additives and fracture appearance of composites were demonstrated by SEM. The hot property of RTV-based composites was outlined by TG. It is found that D₄-SiO₂/Al(OH)₃/DBDPE/Sb₂O₃/RTV composites were of better comprehensive performances in mechanical property, hot property, fire resistance property, and insulating property, which presented tear 26.73 kN/m of strength, 279.8% of elongation at break, 2.81 MPa of tensile strength, FV-0 at the level of flame retardant property, 46 of Oxygen index (OI) 3.03 × 10¹⁵ Ωm of Volume electric resistivity, the range of decomposition temperature was 370°C to 650°C, and the percentage of remain weight was 26.4%. Those properties was acquired on the condition of 11 wt % D₄-SiO₂ + 20 wt % Al(OH)₃ + 15 wt % DBDPE+ Sb₂O₃ at the amount of 3.0 wt % to 3.7 wt %. This investigation leads the authors to a conclusion that D₄-SiO₂/Al(OH)₃/DBDPE/Sb₂O₃ is a kind of better combination modifier than anyone kind of which in comprehensive properties for RTV. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Improved protein resistance of silicone hydrogels by grafting short peptides for ophthalmological application

A simple and facile approach to impart the antifouling properties of silicone hydrogels was developed in this report. Short peptides were first tethered to silicone hydrogels through terminal amino group-induced epoxy ring-opening click reaction. The modified silicone hydrogels have improved hydrophilicity and protein adsorption resistance because of the formation of zwitterionic structure of the grafted peptides. Furthermore, glycylglycine and diglycyl glycine-modified silicone hydrogel contact lenses were fabricated. They exhibited favorable antifouling property and no damage to rabbits’ eyes after continuous wearing. The short peptide modified silicone hydrogel contact lenses have potential application in ophthalmology.     

超顺排碳纳米管/硅橡胶复合材料各向异性的电学性能和力学性能

采用直接浸润法制备了具有不同层数的超顺排碳纳米管(SACNT)薄膜与硅橡胶的复合材料,使碳纳米管薄膜能够在硅橡胶基体表面均匀分散。测量了SACNT薄膜/硅橡胶复合材料在各个方向的导电性能和力学性能,研究了影响复合材料导电性和力学性能的因素。实验结果表明:SACNT薄膜/硅橡胶复合材料的导电性和杨氏模量都随着碳纳米管薄膜厚度的增加而增加,且具有显著的各向异性。垂直于碳纳米管排列方向的电阻率平均比平行方向的大一个数量级。当碳纳米管层数为240层时,平行于碳纳米管排列方向的杨氏模量为116.9 MPa(比纯硅橡胶基体增加了142倍),而垂直方向的杨氏模量仅为1.23 MPa(比纯硅橡胶基体增加50%),两者之间相差近100倍。结果表明,可以通过选择不同的参数,获得具有特定导电性和杨氏模量的SACNT薄膜/硅橡胶复合材料,并在实际中加以应用。     

Peroxidation of Polymethylhydrogensiloxane and Cellulose by γ-Irradiation in Air and Grafting Induced by Their Decomposition

The peroxides of polymethylhydrogensiloxane, cellulose and a mixture of both were determined by ferrous ion method. The relation between the decomposition of the peroxide and the degree of grafting by standing at an elevated temperature after irradiation was examined.

The G-value for the peroxide formation of polymethylhydrogensiloxane was found to be 8.7, and the activation energy for the peroxide decomposition was determined from calculation to be 43 kcal/mol. The ratio of G-values of silicone between those terminated by methyl radical and by methyl radical is estimated to be about 2/1. It would thus appear certain that the rate of peroxidation is affected by the end group. The peroxidation is not a chain reaction at room temperature, and the peroxide is produced by the recombination of the peroxy radical. At least two types of peroxide are produced by irradiation in air, and one is decomposed at 80°C but the other is relatively stable.

On the other hand, the G-value for the peroxide formation of cellulose is equal to 5.6.

The tendency seen for the decrease of the peroxide corresponds to that of increasing degree of grafting, and it may be concluded that only 1/10 of the peroxides formed in the cellulose–silicone system results in grafting, since it has been calculated that the G-value for the grafting through the peroxide is about 1.0.     

Examination of Interpenetrating Polymer Networks of Polyurea in Silicone Molds Arising during Vacuum Casting Processes

We present an in-depth investigation of the aging effects in silicone molds for vacuum casting processes. Their lifetime is limited to a few production cycles due to contamination with the diisocyanate component of polyurethane casting materials. Using thermogravimetric analysis measurements, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and helium-ion-microscopy the chemical and physical mechanisms of the aging process have been identified. It has been shown that a diffusion process of diisocyanate into the cavity surface leads to the formation of interpenetrating polymer networks of polyurea derivatives in silicone rubber. This has been proven by extracting and analyzing polyurea of low molecular weights from the silicone.     

Influence of the microstructure of gums on the mechanical properties of silicone high consistency rubbers

This paper is devoted to the characterization and processing of high molar mass vinyl‐bearing polysiloxanes in high consistency silicone rubber (HCR) formulations. The molar masses of five different polydimethylsiloxane gums, bearing vinyl groups at the ends and along their chains, were evaluated by size exclusion chromatography and rheometry. ²⁹Si and ¹H NMR spectroscopy allowed the precise determination of the vinyl content and of the distribution in the different polymers. Typical HCRs formulated from these gums were heat‐cured to process silicone rubber materials that were then tested mechanically. The macromolecular properties were correlated to the final material network structure. The amount of reactive vinyl moieties, rather than their distribution along or at the end of chains, is a key parameter to tailor the material mechanical properties. © 2016 Society of Chemical Industry     

一种含硅阻燃剂的合成及在PC中的应用

通过苯酚改性含氢硅油合成出一种新型聚碳酸酯用含硅阻燃剂(HSOP)。阻燃及力学性能测试结果表明加入HSOP可以有效地提高聚碳酸酯(PC)的阻燃性,当阻燃剂质量分数5%时,氧指数由纯PC的26.5%提高到32.5%,UL-94阻燃级别由V-2级提高到V-0级,冲击强度和断裂伸长率增加48.9%和37.6%。通过样品的TGA测试和SEM对残炭表面结构分析考察了HSOP对PC的阻燃机理,结果证实,阻燃剂在燃烧时能和PC发生交联反应,导致燃烧后形成致密炭层是材料阻燃性能提高的关键因素。     

有机硅共聚改性环氧树脂研究进展

利用有机硅改性环氧树脂是提高环氧树脂综合性能的有效途径,着重阐述了有机硅改性环氧树脂的化学共聚改性方法,并对有机硅改性环氧树脂的发展方向进行了展望。