Epoxy resins laminates

TBBA, a brominated flame retardant, is used in the epoxy resin laminate in printed circuit boards in most manufacturers products. In 1997, a phosphorus-based alternative to TBBA was developed by the German engineering giant, Siemens,... 

Figure 3.41. A system for remote fibre-optic fluorescence monitoring of viscosity changes during processing of a carbon-flbre-epoxy-resin laminate. Adapted from Levy and Schwab (1987).

Specimen geometry independence of the experimental measurement.s has been examined by, for instance, conducting DCB (mode I) and ENF (mode II) tests on specimens with different thicknesses [162. The values are virtually independent of thickness for CF epoxy resin laminates. A magnitude of increase comparable with the standard deviation... 

Figure 1.10 Effect of various particulate fillers on the interlaminar shear strength of glass fabric reinforced epoxy resin laminates (23]. A, no filler B, BOixm glass beads, untreated C, same but silane treated D, 7 i,m glass beads, untreated E, same but silane treated F, 15p.m glass flakes G, 8 i,m calcium carbonate H, 15p.m quartz I, 15p.m alumina trihydrate, fire retardant J, 20p.m mica K, 60p.m thin-walled hollow-glass microspheres...

Karasek et al. [66] conducted drop-weight impact tests on IM7 carbon fibre/ epoxy resin laminates after sea water exposure. Four resin systems (Table 7.2) were used, three of them being based on the same Shell Epikote 828 with different hardeners and/or impact modifiers. The volume fractions were in the range 60-69% fibre and the lay-up was [0/ 45/90°]js. Samples were about 6.35 mm thick for all materials (different cured ply thicknesses necessitated the use of differing numbers of plies) and cut to 100 x 100 mm squares for testing. The samples were saturated with ASTM D1141-52 Formula A synthetic sea water at 95°C, and then conditioned at ambient... 

Uses Reactive diluent in epoxy resins, laminating, flooring, elec, casting and encapsulants and highly filled coatings epoxy modifier Manuf/Distrib. Aldrich Alemark Amber Syn. Ashland CPS Ciba Spec. Chems./Water Treatment Fluka Monomer-Polymer Dajac Labs ... 

Epoxy cresol novolac epoxy resin, food-contact coatings Epoxy cresol novolac epoxy resin, high performance aircraft bodies/components p,p, p"-Tri (2,3-epoxypropoxy) triphenylmethane epoxy resin, high-temp, adhesives Epoxy cresol novolac epoxy resin, laminating prods. 

Figure 20.26 Variation of longitudinal compressive strength of carbon fiber epoxy resin laminate with temperature showing transition from shear mode to buckling mode failure. Failure depends on the shear modulus of the matrix and shear strength of the fibers and a similar effect is observed with the uptake of water. Source Reprinted with permission from Ewins PD, Potter RT, Phil Trans R Soc London, A294, 507-517, 1980. Copyright 1980, The Royal Society of Chemistry.

Figure 22.4 Interlaminar shear stress as a function of ply angle for Type I high modulus carbon fiber epoxy resin laminate tested in uniaxial tension in x-direction. The maximum interlaminar shear strength occurs at 0 = 35° and the stresses are zero at 0, 60 and 90°. Source Reprinted with permission from Pipes RB, Pagano NJ, Interlaminar shear stress in composite laminates under axial tension, J Composite Mater Sci, 13, 2131-2136, 1978. Copyright 1978, Sage Publications.

As a result some computer manufacturers, such as Hewlett-Packard, have shifted to phosphorus-based FRs in housings for computer monitors. Siemens has developed a phosphoms-based alternative to the TBBA used in the epoxy resin laminates that are the basis of all circuit boards. 

The polyester resin may be modified with methyl methacrylate resins for better clarity and transparency. Recent developments involve the use of acrylates or polyvinyl flnoride as surface coatings bonded to the laminate for longer gloss retention. The prodnct is cnred at ambient temperatures, although heat will accelerate the cure and ensure a more satisfactory laminate. The same procedures are also followed in producing epoxy-resin laminates, although these are not as widely used in the construction industry. 

Haug, T., New laminating resins with improved thermal, mechanical and chemical properties. Paper WCl 11-53, nted Circuit World Convention III, Washington DC, May 1984 Azuma, K., Epoxy resin laminates based... 

Figure 5.277 shows an example of acceptable tensile strength as a function of outer fiber strain for a mat and a non-woven laminate with UP and EP matrix. Laminates with a polyester resin matrix and an epoxy resin matrix are also provided for comparison. The acceptable residual strength continuously decreases with increasing outer fiber strain. This is more pronounced in epoxy resin laminates than in polyester resin laminates. Sulfuric acid penetrates relatively easily into epoxy resins. The activation energy of penetration depends on the acid concentration and is higher for weakly concentrated acids than for highly concentrated acids. It is over-... 

It should be noted that epoxy resin-laminates are the materials of choice in aerospace applications, where influences of moisture absorption and desorption on mechanical properties play a large role. Corresponding epoxy resin systems have been developed for these particular applications. The polarity in crosslinked materials should be kept as low as possible in order to limit moisture equilibrium. 

Most of the construction of the Boeing 787 Dreamliner uses low-density composite materials (i.e., honeycomb structures and continuous carbon fiber-epoxy resin laminates). 

High performance composites may be laminates wherein veils of carbon fiber ate treated with an epoxy resin, stacked up to the desired final product thickness, and then laminated together under heat and pressure (see Composite materials Carbon and graphite fibers). Simply mixing together carbon or glass fibers and polymeric resins to form a reinforced plastic leads to a composite material, but this is not a laminate if not constmcted from discrete phes. 

Some high performance laminates consisting of carbon fiber webs and epoxy resins are cured in autoclaves. An autoclave is a pressure chamber in which the pressure is appHed hydrostatically. 

Composite-Based Laminates. Grade CEM-1 are laminates with continuous-filament glass cloth surfaces and a cellulose core, all with a flame-resistant epoxy resin binder. With good punching practice, sheets up to and including 2.4 mm (0.094 in.) in thickness may be punched at temperatures not less than 23°C (73°F). These laminates meet UL94 V-0 when tested in accordance with UL94. 

Aqueous dispersions are used in fiber bonding, paper coating, friction and abrasive appHcations, and laminates and wood bonding. PhenoHc dispersions improve the strength of latex-contact adhesive appHcations. Epoxy-modified phenoHc dispersions are prepared by dispersion of the phenoHc epoxy resin. The systems are used for baked primer appHcations and bonding requirements. Minimum baking conditions are 20 min at 150°C (25). 

This low viscosity resin permits cure at low (70°C) temperatures and rapidly develops excellent elevated temperature properties. Used to increase heat resistance and cure speed of bisphenol A epoxy resins, it has utihty in such diverse appHcations as adhesives, tooling compounds, and laminating systems. A moleculady distilled version is used as a binder for soHd propellants (see Explosives and propellants) and for military flares (see Pyrotechnics). Its chief uses depend on properties of low viscosity and low temperature reactivity, particularly with carboxy-terminated mbbers. 

Electrical Laminates. A significant use for epoxy resins is in the manufacture of copper-clad epoxy-glass printed circuit boards. Systems are available that meet the National Electrical Manufacturers Association (NEMA), GIO, Gil, FR3, FR4, FR5 specifications. Currently the majority of boards are manufactured to the fiame-retardant FR4 specification. The flame retardance is achieved by the use of a soHd epoxy resin based on... 

This includes wire enamels on a base of polyvinyl formal, polyurethane or epoxy resins as well as moulding powder plastics on phenol-formaldehyde and similar binders, with cellulose fillers, laminated plastics on paper and cotton cloth base, triacetate cellulose films, films and fibres of polyethylene terephthalate. 

Polymer systems are now available which may be cured by reaction of epoxy resin compounds with the phenolic hydroxyl groups. Such reactions do not evolve volatile by-products. These materials are showing promise in the area of heat-resisting electrical insulation laminates. 

Elevated temperatures are necessary for cure and the chemical resistance of the laminates is inferior to those from unmodified resins. Because of problems in handling, the polyamides have found only limited use with epoxy resins, mainly for coating and adhesive applications. 

Shear-stress-shear-strain curves typical of fiber-reinforced epoxy resins are quite nonlinear, but all other stress-strain curves are essentially linear. Hahn and Tsai [6-48] analyzed lamina behavior with this nonlinear deformation behavior. Hahn [6-49] extended the analysis to laminate behavior. Inelastic effects in micromechanics analyses were examined by Adams [6-50]. Jones and Morgan [6-51] developed an approach to treat nonlinearities in all stress-strain curves for a lamina of a metal-matrix or carbon-carbon composite material. Morgan and Jones extended the lamina analysis to laminate deformation analysis [6-52] and then to buckling of laminated plates [6-53]. 

---