Epoxy resins cross-linking

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). 

Cross-linked epoxy resin (thermoset of bisphenol A diglycidyl ether). 

Highly cross-linked epoxy resins combine high strength stiffness thermal, chemical, and environmental stability adhesion low weight processability excellent creep resistance and favorable economics. These resins are widely applied as coatings, casting resins, structural adhesives, and matrix resins of advanced composite materials. The broad spectrum of applications ranges from the automotive and aerospace industries to corrosion protection and microelectronics. 

The inhibitor should be capable of being transported through a cross-linked epoxy resin matrix. 

Other multiblock copolymers contain slloxanes as blocks, and others are based on cross-linked epoxy resin systems (35). 

In contrast to tertiary amine hardeners, which, as shown, cross-link epoxide resins by a catalytic mechanism, polyfunctional primary and secondary amines act as reactive hardeners and cross-link epoxy resins by bridging across epoxy molecules. 

To be suitable for powder coatings, resins should melt for pigmentation at temperatures well below that required for cross-linking, should be brittle and amenable to dry milling when cold, should be stable in the presence of cross-linker when stored at room temperature and, at stoving temperatures, should melt and fall rapidly in viscosity before cross-linking. Epoxy resins admirably meet these requirements. 

Anhydrides cross-link epoxy resins by reacting first with the hydroxyl groups. Carboxyl groups are produced in the process and these then react with the epoxy ring. Stoving is at 180-200° C. 

Journal of Polymer Science Polymer Physics Edition 32, No.3, Feb. 1994, p.395 08 TOUGHENING OF A HIGHLY CROSS-LINKED EPOXY RESIN BY REACTIVE BLENDING WITH BISPHENOL A POLYCARBONATE. I. 

Cross-linked epoxy resins are combustible and their burning is self-supporting. They require mainly reactive flame-retardants, such as tetrachloro- or tetrabromobisphenol-A and various halogenated epoxides. Even the cross-linking agent may be flame-retardant, as in the case of chlorendic anhydride, tetrabromo- or tetrachloro-phthalic anhydride, or possibly phosphorus compounds. Halogenated agents can be supplemented with antimony trioxide. 

Many different aliphatic and aromatic polyamines are available for cross-linking epoxy resins. Some of these are ethylenediamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, and many others. Among the aromatic polyamine are / -phenylene diamine, /n-phenylene diamine, 4,4 -diaminodiphenyl-methane, and diaminodiphenylsulfone. 

Many cyclic acid anhydrides are used industrially for cross-linking epoxy resins. These are mono and polyanhydrides. Following are some typical commercially used anhydrides ... 

Ester and ketone solvents, which react with amines, must not be present. The adduct is a polyamine and can therefore be used to cross-link epoxy resins. It has advantages in that it is odourless (simple amines are unpleasant to handle), part-reacted (which speeds up drying) and free from simple amines (which cause exudation and are toxic). It can be seen now why it is an advantage to age paints cured by simple amines amine adducts are formed during the aging. 

The package stability of alcohol-soluble resole resins and their compatibility with epoxy resins can be improved by partial conversion of the methylol groups to ethers. Allyl ethers have been used with epoxy resins in interior can coatings. Low molecular weight butyl ethers are used with acid catalysts to cross-link epoxy resins and other hydroxy-substituted resins, by etherification and transetherification reactions (148). 

Materials with highly cross-linked epoxy resin reinforced with woven fiber glass are the most common in use. Bromine is reacted with the epoxy matrix and is used to provide fire retar-dancy. Most epoxy-based materials satisfy the Underwriters Laboratories (UL) classification of V-0 for fire retardancy. The generic term for this family of epoxy resin materials is FR-4, with FR standing for flame retardant and 4 an assigned number indicating epoxy. Epoxyfiberglass materials are sold by many snpphers and have become a commodity material. 

Abbate M, Martuschelli E, Musto P, Ragosta G, Scarinzi G (1984) Toughening of a highly cross-linked epoxy resin by reactive blending with bisphenol A polycarbonate. I. FTIR spectroscopy. J Polym Sci Polym Phys Ed 32 395-408... 

The surface energy of v ater is not altered by pebbles in the latter hence, the y of polymers would be expected to be unaffected by inorganic fillers. In reality [41, incorporation of 1 part of silica in 1 part of cross-linked epoxy resin raised the "p by a factor of nearly 10. 

For cross-linked epoxy resins, a dependence on the mean cross-link distance D is evident from Figure 5 if at low temperatures D and Xd are on the same order of magnitude (13,27). 

Motivated by the differences observed in the DMA data of the un-aged and aged loosely cross-linked specimens, master curves for the systems under study were constructed. The tan 5 of the un-aged loosely cross-linked epoxy resin in the and / relaxation regions are shown in Figure 4 and Figure 5, respectively. The peak values in the region decrease as the temperature is... 

Furthermore, analyses of the un-aged and aged loosely cross-linked epoxy resins in the region (see... 

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