Silica reinforcement epoxy resins

The traditional TPS for launcher fairings and re-entry capsules consists of an external ablative insulation, fixed or bonded onto a metallic primary structure. Ablative materials are based on thermosets (phenolic and epoxy resins) or elastomers (ethylene-propylene and silicone rubbers) usually filled and reinforced with cork, cotton, glass, silica, quartz, carbon, silicon carbide, nylon and aramid in the form of powders, fibres, fabrics and felt (Table 2). 

Compared to a common thixotrope such as fumed silica, pulp provides equivalent viscosity at less than one tenth the weight in a typical epoxy resin. In addition, fluid viscosity is unaffected by further processing (agitation) or aging—in contrast to fumed silica modified resin where viscosity drops and is not fully recovered under similar conditions. Pulp can also provide reinforcement in an adhesive matrix as shown by the significant increase in tensile strength, modulus, and tear strength of both a PVC plastisol adhesive and a silicone sealant on the addition of pulp [137,140]. 

Ros Rosso, P., Ye, L., Friedrich, K., Sprenger, S. A toughened epoxy resin by silica nanoparticle reinforcement. J. Appl. Polym. Sci. 100 (2006) 1849-1855. 

As discussed in Chapter 6, the incorporation of reinforcing agents or fillers into plastic formulations can, in some but not all cases, lead to variations in the molecular stability of plastics and also their thermal and thermooxidation stability. Thus, it has been observed that the addition of silica to polytetrafluoroethylene did not adversely affect polymer stability, while the incorporation of 25% of organically modified silica into polyethylene led to a decrease in weight loss of the plastic from 80% to 33.7%. The incorporation of carbon nanotubes in epoxy resins unproved their mechanical and thermal properties. It is fair to say that the effect of reinforcing agents on the thermal and thermooxidative stability of polymers must always be bom in mind when selecting polymer formulations for a particular application. 

The incorporation of silica into epoxy resins has little effect on tensile strength. The tensile strength of reinforced epoxy resin is 30-84 MPa, compared to values of 68-72 MPa for silica-reinforced polymer. The flexnral modulus falls from 80 GPa for the unreinforced polymer to 15 GPa for the reinforced polymerm while elongation at break remains virtually unchanged. 

The reasons described above lead to a conclusion that the interface may be the weakest element in the repair work, and as such, a source of future destruction. That is why there are many practical methods available to reinforce the interface and to ensure its high quality. Among the various known measures, special interface layers of the Portland cement paste, neat or reinforced with thin grids of steel or textile wires may be mentioned. Careful preparation of the surface of old concrete is always needed by cleaning and moistening. Intermediary layers may be prepared with increased Portland cement content, admixtures of polymeric materials or silica fume, or composed with epoxy resins. 

In addition, the good compatibility between m-HNTs and the epoxy matrix may also play an important role in the reinforcing effect where the good compatibihty is due to the interaction between the silica modified HNT and the epoxy resin. Therefore, the nanocomposites exhibit higher modulus even at the elevated temperatures [25]. 

Sreekala M S and Eger C (2005) Property improvements of an epoxy resin by nano-silica particle reinforcement, in Polymer Composites from Nano- to Macroscale (Eds. Friedrich K, Fakirov S and Zhang Z) Springer, Berlin, Ch. 6, pp. 91-105. 

Mahrholz, T., Stangle, J., Sinapius, M., 2009. Quantification of the reinforcement effect of silica nanoparticles in epoxy resins used in liquid composite molding processes. Composites Part A 40, 235-243. 

Sprenger, S., 2014. Fiber-reinforced composites based on epoxy resins modified with elastomers and surface-modified silica nanoparticles. Journal of Materials Science 49, 2391—2402. 

Composites used in Dentistry were developed in 1962 by combining dimethacrylates (epoxy resin and methacrylic acid) with silanized quartz powder [49]. Modem restorative composites are comprised of synthetic monomers, typically dimethacrylates, reinforcing fillers, typically made from radiopaque glass, quartz or silica, chemicals which promote or modify the polymerization reaction, and silane coupling agents which bond the reinforcing fillers to the polymer matrix [26]. 

Other recent applications of ToF-SIMS without XPS include the examination of PS [6, 17-19], polyethylene (PE) [20], carbon fibre reinforced epoxy resins [21], polyalkyl methacrylates [22], alkylketene dimers [23], perfluorinated polymers [24], perflnorinated ethers [25], polyethylene glycol (PEG) oligomers [15, 25-29], rubber [30], ethylene-tetrafluoroethylene copolymer [30], Nylon-6 [31], PC [32,33], PDMS [34], polypyrrole coated PS [35], poly-p-phenylene vinylene [36], butyl rubber [37], poly(4-vinyl phenol)/poly(4-vinyl pyridine blends) [38], polypyrrole-silica gel composites [39], y-glycidoxypropyl trimethoxy silane [40], triblock copolymer poly(ethylene glycol)- 3 poly(phenylene ethylene)- 3 poly(ethylene glycol) [41], ethylene-terephthalate-hydroxybenzoate copolymer [42], PS-polyvinyl methyl ether, polycarbonate - PS blends [43] and PDMS-urethane [44],... 

The presence of silica NPs assembled to fibrous clays could be of interest for their use as nanofillers in polymers reinforcement Preliminary attempts in the use of silica-sepiolite nanoarchitectures, as well as the intermediate silica-organosepiolite materials, as nanofillers of epoxy resins show a moderate mechanical improvement [57,74], Further modifications of the silica NPs assembled to sepiolite could produce organic-inorganic hybrids that can be considered as promising new functional materials for diverse applications, from sensing devices to polymer reinforcement. 

Thermosetting plactics are often reinforced by as much as 100 phr of various fillers, for example, wood flour, cotton flock asbestos and synthetic fibre used with phenolic thermosets, and silica flour, mica or talc with epoxies. Glass fibre reinforcement of polyester resins for structural, automotive, aerospace and marine applications is too well known to require comment. 

Epoxies are adhesive systems made by a complex chemical reaction. Various resins are made synthetically by reacting two or more chemicals. The resultant resin can then be reacted or cured by the addition of another chemical called a hardener or catalyst. The basic epoxy resin systems are further modified to change their physical properties by the addition of such things as flexihilizers for impact resistance and flexibility, diluents or solvents to reduce the viscosity fillers, and reinforcements hke glass fiber, alumina, silica sand, clay, metal powders, and flakes to change properties such as heat and electrical resistance, fire retardance, strength, and adhesion to certain substrates or materials. 

Epoxy, polyester, phenolic and other resins are used as coatings and linings with or without reinforcement. Glass fiber, silica, carbon and many other materials can be used as filters or reinforcement to produce materials with specific properties of strength, flexibility, wear resistance and electrical conductivity. 

Phenolic resin with an organic (nylon), inorganic (silica), or refractory (carbon) reinforcement Precharred epoxy impregnated with a noncharring resin... 

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