Fibers, radiation curing

Ra.dia.tlon. Use of radiation to affect fixation of some flame retardants is being investigated (110). Electron-beam fixation requires the selection of compounds that can be insolubilized inside or outside of the fiber with high yield in a short time. Polyunsaturated compounds, eg, Fyrol 76, have shown promise (see Radiation curing). 

The main potential for expansion of UV/EB into aerospace and certain commercial applications is by developing radiation curing of polymeric fiber-reinforced composites. The initial work on composite skin repairs involve applying the UV curing technology with bisacryl phosphine oxide to ensure the cure of relatively thick layers. A total of ten layers were used at a time. The UV cured composites closely matched those produced by heating. ... 

Vapor deposition has been used to prepare fibers such as woven and nonwoven synthetic and natural fibers having hydrophobic/oleophobic and biocide properties. This process entails flash evaporation of a perfluoroacrylate monomer and its radiation curing in a vacuum chamber onto a selected fiber surface. 

Okamura and co-workers (18) have taken air-cured PCS polymer and, through pyrolysis in the presence of ammonia, prepared essentially carbon-free silicon oxynitride fibers (equation 13). However, if the PCS polymer fiber is cured by electron beam radiation (to prevent oxygen addition), the same ammonia pyrolysis conditions provide nearly stoichiometric quantities of silicon nitride fibers (equation 14). 

While most of these films are clearly low-modulus materials, they possess properties useful for such radiation-cure coating applications as conformal coatings, electronic encapsulent gels, or fiber optic coatings, particularly where such applications demand silicones broad operational temperature range,... 

Uses Crosslinking agent in casting compds., glass fiber-reinforced plastics, adhesives, coatings, ion-exchange resins, textile prods., plasti-sols, dental polymers, rubber compding. reactive diluent for radiation-cured inks, lacquers crosslinked acrylic resin comonomer Trade Names SR 239... 

Uses Monomer for creating and modifying polymers, acrylic resins, urethane methacryiates marine antifouling paint resin comonomer reactive comonomer for acryiic and S/B resins rubber modifier binder for textiies/paper adhesives, nonwoven fabrics, enamels, adhesives grafting of textiie fibers scaie inhibitors adhesion promoter for polymers hydrophilic polymers It.-curing polymer systems reactive thinner for radiation curing food-pkg. adhesives, polymers Manuf./Distrib. Acros Org. Aldrich Allchem Ind. Ashland BP Amoco Electron Microscopy Sciences Fluka ICN Biomed. Research Prods. Kessler Lancaster Synthesis Laporte Perf. Chems. Monomer-Polymer Dajac Labs Pfaltz Bauer Rohm Haas Rohm Tech San Esters Scientific Polymer Prods. Sigma TCI Am. Ubichem pic Whyte Chems. Ltd... 

Narisawa, M., Idesaki, A., Kitano, S., Okamura, K., Sugimoto, M., Seguchi, T., Itoh, M., Use of blended precursors of poly(vinylsilane) in polycarbosilane for silicon carbide fiber synthesis with radiation curing. Journal of the American Ceramic Society 1999,82(4), 1045-1051. 

Continuous scans of modulus versus temperature utilizing the DuPont Dynamic Mechanical Analyzer (DMA) has provided a comparison of the high temperature service capabilities of radiation-cured experimental formulations of a vinyl-modified epoxy resin. Shell Epocryl-12. These scans were compared to data obtained when the same materials were applied as adhesives on aluminum test panels, radiation-cured with an electron beam, and lap shear strength tested at discrete temperatures. The DMA instrument utilizes a thin rectangular specimen for the analysis, so specimens can be cut from blocks or from flat sheets. In this case the specimens were cured as sheets of resin-saturated graphite-fibers. The same order of high temperature stability was obtained by each method. However, the DMA method provided a more complete characterization of temperature performance in a much shorter test time and thus, it can be very useful for quick analyses of formulation and processing variables in many types of materials optimization studies. The paper will present details of this study with illustrations of the comparisons. 

Figure 11. Variations of the room temperature tensile properties of SiC-based fibers as a function of the temperature. The pyrolysis temperature for Si-C-0 fibers deriv from PCS and Si-C fibers derived from radiation-cured PCS with 0.4 wt.% of oxygen [77] reproduced with permission from the Woodhead Publishing Ltd.

T. Seguchi, M. Sugimoto and K. Okamura, Heat resistant SiC fiber synthesis and reaction mechanisms from radiation-cured polycarbosilane fiber, in High Temperature Ceramic Matrix Composites, R. Naslain, J. Lamon, D. Doumeingts, eds., Woodhead Pubi. Ltd., Abington-Cambridge, UK, 51-57 (1993). 

T. Shimoo, T. Hayatsu, M. Takeda, H. Ichikawa, T. Seguchi and K. Okamura, Mechanism of oxidation of low-oxygen SiC fiber prepared by electron radiation curing method, J. Ceram. Soc. Japan, 102 [7], 617-622 (1994). 

Si-C-N-0 and Si-C-N(O) fibers exhibit linear elastic tensile behavior up to failure. At room temperature HPZ based fibers have tensile strengths ranging from 1.9 GPa [22] to 3.1 GPa [21], and elastic moduli ranging from 200 GPa [22] to 260 GPa [21]. PCSZ based fibers have similar mechanical properties. Oxygen cured Si-C-N-0 ceramic fibers and radiation cured Si-C-N(O) fibers have moduli of 175 GPa and 215 GPa, respectively, and tensile strengths of 1.8 GPa and 2.4 GPa, respectively [10-11]. 

S. Kamimura, K. Watanabe, N. Kasai, T. Seguchl and K. Okamura, Silicon nitride fiber synthesis from polycarbosilane fiber by radiation curing and pyrolysis under ammonia, Ceram. Transactions, 58, 281-286 (1995). 

Pressure sensitive tapes and labels are offered with a variety of backing materials such as crepe paper, aluminum foil, fabric, cellophane, kraft paper, cellulose acetate, polyester film, polyethylene, polypropylene, plasticized poly (vinyl chloride), woven glass fiber cloth, or other flexible materials. Pressure sensitive adhesives may be applied from solvent, latex, hot melt, or radiation cured 100% solids systems. A wide variety of coating methods are utilized such as roll coating, calendering, slot die, and transfer coating. 

Experimental results are presented that show that high doses of electron radiation combined with thermal cycling can significantly change the mechanical and physical properties of graphite fiber-reinforced polymer-matrix composites. Polymeric materials examined have included 121 °C and 177°C cure epoxies, polyimide, amorphous thermoplastic, and semicrystalline thermoplastics. Composite panels fabricated and tested included four-ply unidirectional, four-ply [0,90, 90,0] and eight-ply quasi-isotropic [0/ 45/90]s. Test specimens with fiber orientations of [10] and [45] were cut from the unidirectional panels to determine shear properties. Mechanical and physical property tests were conducted at cold (-157°C), room (24°C) and elevated (121°C) temperatures. 

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