Epoxies curing

Because the heat distortion temperature of cured epoxy resins (qv) increases with the functionality of the curing agents, pyromellitic dianhydride is used to cross-link epoxy resins for elevated temperature service. The dianhydride may be added as a dispersion of micropulverized powder in liquid epoxy resin or as a glycol adduct (158). Such epoxies may be used as an insulating layer in printed circuit boards to improve heat resistance (159). Other uses include inhibition of corrosion (160,161), hot melt traffic paints (162), azo pigments (163), adhesives (164), and photoresist compounds (165). 

Fig. I. Comparison of unprimed and eleetroprimed single lap-shear adhesive joint strengths for steel coupons bonded with imidazole-cured epoxy [43].

Redux was soon extended to other aircraft including the DeHavilland civilian airliner Dove and the jetliner Comet [202]. In the Fokkcr F27/F50 Friendship , it accounted for about 70% of stmctural bonds (about 550 parts). Over 1000 F27/F50 aircraft were constructed and were in service for over 30 years, indicating high fatigue resistance and durability ([198], pp. 80-81). When attempts were used to substitute low-temperature curing epoxies for PVF, joint corrosion due to salt spray exposure required expensive repairs. 

EB processing and rheological properties of EB-cured epoxy adhesives... 

Lap shear strengths (MPa) of selected EB-cured epoxy adhesives at various temperatures... 

Effects on lap shear strength of EB-cured epoxy adhesives from different surface preparations on aluminum and composite adherends... 

Primers are required to be resistant to all of the same fluids and environments as the adhesive, and are in addition expected to be compatible with secondary finishes such as corrosion and fluid resistant primers applied to cured bond assemblies. The most commonly used primers for 250°F cured epoxy adhesives also have active corrosion inhibitors themselves to combat corrosion at bondlines. This last requirement is somewhat dated, evolving from the severe corrosion and delamination problems experienced before U.S. airframe manufacturers adopted durable surface treatments. 

For resistance to acid conditions alone, traditional filled and unfilled bituminous solutions (which have economic advantages), chlorinated rubber and shellac have been used. Crosslinking coatings, e.g. amine-cured epoxy resins, often blended with coal-tar which develops resistance to oils and solvents, have obvious advantages on chemical plant. 

Kamon, T., Furukawa, H. Curing Mechanisms and Mechanical Properties of Cured Epoxy Resins. Vol. 80, pp. 173 — 202. 

Materials. The single films and multilayered materials examined are listed in Tables I and II, respectively. The adhesive (10thick) between any two layers was a two-component curing, epoxy—polyester adhesive, Adcote 503A, Morton Chemical Co. Pouches (11.5 X 17.8 cm) were made from the multilayered materials by heat sealing the sides and bottom under the optimum heat sealing conditions (3). 

Epoxy (Anhydride-Cured) Epoxy resins may be crosslinked with various anhydrides by using a tertiary amine accelerator and heat. These cured polymers generally have good chemical resistance especially to acids. 

RPLC-PDA is frequently used for quality control, such as the determination of free Irganox 1098 in PA4.6 (at 278 nm after dissolution/precipitation), of free Irganox 1010/1076 in PP (at 278 nm after extraction with MTBE, thus avoiding dissolution of polymer waxes), of Luperco 802 in PP (at 218 nm, after extraction with HCC13), and of Tinuvin 122 in HDPE (at 225 nm as diol). The advantages of the use of HSLC over conventional LC in QC of plastics and additives have been demonstrated, e.g. for AOs in PE, mixed phthalate esters and residual terephthalic acid in PET and partially cured epoxy resins [557],... 

Figure 9. UV-visible absorption spectra of a stabilized PVC plate, with or without a 70 yin UV cured epoxy-acrylate coating, before and after QUV aging at 40°C...

S02-cured epoxy resin. Modified epoxy/acrylic resins (1.2 to 1.4% of sand weight) are mixed with organic peroxide (26 to 60% of resin weight), the mixture is blown into the core box and a hardening mechanism similar to the S02 process takes place. 

Fig. 23. Master curve obtained by time cure superposition of data on curing epoxy (a) before the LST and (b) after the LST [15]...

A Kinetic Study of an Anhydride-Cured Epoxy Polymerization... 

The resin system selected to initiate these studies is a step-growth anhydride cured epoxy. The approach to the kinetic analysis is that which is prevalent in the chemical engineering literature on reactor design and analysis. Numerical simulations of oligomeric population density distributions approximate experimental data during the early stages of the cure. Future research will... 

Tanaka and Kakiuchi (6) proposed catalyst activation via a hydrogen donor such as an alcohol as a refinement to the mechanism discussed by Fischer (7) for anhydride cured epoxies in the presence of a tertiary amine. The basic catalyst eliminates esterification reactions (8). Shechter and Wynstra ( ) further observed that at reaction conditions BDMA does not produce a homopolymerization of oxiranes. 

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