Cure compatibility

A description is given of a comparative study of the glycolysis of PETP waste soft drinks bottles by various mixtures of EG and DEG with subsequent polyesterification of the glycolysed products by maleic anhydride in order to obtain unsaturated polyesters suitable for the production of varnishes. The processing characteristics such as viscosity, exotherm temperatures of curing, compatibility of resins with monomers was investigated with respect to the type and amount of reactive monomers. The mechanical properties of varnishes produced were analysed. 13 refs. 

For the EPDM/NR joint, the modification of the EPDM rubber increases its cure compatibility with NR. This, thus, increases with radiation dose up to 50 kGy beyond which a drop in the absorbance values due to predominant chain scission of the rubber also lowers the bond strength. Besides, interdiffusion of the mbber molecules across the interface also contributes to the formation of the bond. 

Chlorobutyl (CIIR) and bromobutyl (BIIR) are modified types containing 1.2% wt of chlorine or bromine, the isoprene unit being the site of halogenation. Introduction of the halogen gives greater cure flexibility, and enhanced cure compatibility in blends with other diene rubbers. It also confers increased adhesion to other rubbers and metals. 

Some, like trisomy 13 and 15, produce gross deformities and lead to death in infancy or early childhood. Others, such as trisomy 21, lead to mental retardation and a number of anatomic abnormalities, but cure compatible with long life. The social burden of such conditions may be large, not only for the individual, but for the family and for the public if institutional care is required. 

The halogenated products improve the mixing and cure compatibility with the more common unsaturated rubbers such as natural or styrene-butadiene rubber. 

Features Highly reactive optimum absorp. 250-350 nm fast cure response go< torough-cure compat. with resins Properties Wh. cryst. powd. taint char, odor sol. in most common org. soivs., monomers, prepolymers sol. (g/100 ml) 116 g ethyl acetate, 115 g toluene, 113 g styrene, 80 g acetone insol. in water m.w. 256 sp.gr. 1.176 (20 C) m.p. 63-66 C... 

Manufecturers Comments RT cure. Compatible with rocket propellants. Qualifications SEP, SNPE. 

Butyl rubber is one of the older synthetic rubbers, having been developed in 1937. Because of the saturated nature of a polyolefin elastomer, the commercial polymer is actually a copolymer of isobutylene and isoprene. The isoprene is added to provide cure sites. In addition, halogenated (bromo or chloro) derivatives are available. The halogenated products improve the mixing and cure compatibility with the more common unsaturated rubbers such as natural or styrene-butadiene rubber. 

Comparing Zinc Oxide Cure Compatible and Zinc Peroxide Compatible XNBR... 

This modified BR contains about 1.2 wt% of chlorine and has greater vulcanization flexibility and enhanced cure compatibility than other general-purpose elastomers. ... 

Erequendy, the curing equipment available, ie, presses, autoclaves, LCM lines, etc, do not allow the curing conditions to be varied as desired, so the compounder must design a cure system compatible with the existing equipment while also meeting the compound performance requirements. 

Cured hides must be properly soaked to obtain satisfactory rehydration and removal of unwanted material. InterfibnUar proteins should be degraded in order to increase water uptake. Bacterial proteases and pancreatic proteases are normally preferred, and are compatible with most tannery chemicals used in soaking, ie, most surfactants and preservatives containing sodium chlorite. 

Nitrile rubber is compatible with phenol-formaldehyde resins, resorcinol-formaldehyde resins, vinyl chloride resins, alkyd resins, coumarone-indene resins, chlorinated rubber, epoxies and other resins, forming compositions which can be cured providing excellent adhesives of high strength, high oil resistance and high resilience. On the other hand, NBR adhesives are compatible with polar adherends such as fibres, textiles, paper and wood. Specific formulations of NBR adhesives can be found in [12]. 

The PVF is made by acidic reaction between poly(vinyl alcohol) (PVA) and formaldehyde. The poly(vinyl alcohol) is, in turn, made by hydrolysis of poly(vinyl acetate) or transesterification of poly(vinyl acetate). Thus, residual alcohol and ester functionality is usually present. Cure reportedly occurs through reaction of phenolic polymer hydroxyls with the residual hydroxyls of the PVA [199]. The ester residues are observed to reduce bond strength in PVF-based systems [199]. This does not necessarily extend to PVF-P adhesives. PVF is stable in strong alkali, so participation of the acetals in curing is probably unimportant in most situations involving resoles. PVF is physically compatible with many phenolic resins. 

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. 

S.2.2.2. Composite adherends. Composite adherends are bonded in both the cured and uncured states. Wherever possible the adhesive and all adherends are cured simultaneously to avoid the added cost of additional autoclave cure cycles. In many cases this is not practical due to part size and complexity. Cured parts can be bonded to uncured parts, which is known as cobonding, and fully cured parts can be bonded together, which is known as secondary bonding. Adhesives for composites are formulated to be compatible with matrix resins in either cured or uncured states. 

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