Thermal cure shrinkage

Epoxies show superior adhesion to metals and glass, and have limited shrinkage during cure. They are used for surface coatings, as adhesives and rc>r laminating to produce plastic tanks, pipe, and aircraft parts, etc (Ref 3, p 445-R). They also have been used in manuf of plastics (Ref 1), construction of rockets St missiles (Ref 2) and in manuf of explosive compositions of improved mechanical and thermal stability (Ref 4)... 

A 60 durometer EPDM rubber for a pure bleach will not produce black speck contamination. It has the same excellent bleach and water resistance with the added feature of having food grade FDA compliance. All linings are to be designed for minimal shrinkage in cure and should have good thermal flexibility. 

All rubber products exhibit shrinkage after cure, mainly due to the thermal expansion which occurs at vulcanization temperature. Moulded rubber goods are never as big as the moulds in which they are cured. The difference between the dimensions at room temperature of the finished goods and of the mould expressed as a percentage is called the shrinkage from mould dimensions. 

Reduced shrinkage on curing Increased water absorption Increased thermal and... 

Thermal conductivity also helps to improve heat transfer during cure. This reduces exothermic temperatures and extends pot life, particularly at high filler loadings. Shrinkage during cure is also reduced, as explained in the sections above. 

To be considered a promising candidate for high-temperature applications, an adhesive must provide all the usual functions necessary for good adhesion (wettability, low shrinkage on cure, thermal expansion coefficient similar to that of the substrate, toughness, etc.), and it must also possess... 

Sometimes filled adhesives will show better resistance to moisture resistance than unfilled adhesives simply because incorporating inert fillers into the adhesive lowers the organic volume that can be affected by moisture. Aluminum powder seems to be particularly effective, especially on aluminum substrates. The filler can provide a reduction of shrinkage on cure, a reduction of the thermal expansion coefficient, and a reduction of the permeability to water and other penetrants. However, fillers do not always produce more durable bonds. 

HeUmann [4] prepared a dental material from the co-ohgomerization of i-octyl acrylate and methacryloyloxyethylcarbamoyl-ethyhnethylketonoxime, (IV). The copolymer had a Mn of roughly 21,000 daltons and a shrinkage of less than 2% after thermal curing. 

The fillers are added so that the adhesives are sag-free, motionless and form shapes that suit the components to be bonded, reduce shrinkage during cure, increase thermal conductivity, improve corrosion resistance and reduce costs. The concentration of these curatives, fillers and conducting agents is usually monitored using ICP-OES. 

Although unmodified phenolic novolac adhesives (particularly for tyre-cord bonding) can give bonds that exhibit both excellent thermal and environmental durability, they are also inherently brittle. To reduce the shrinkage on cure and to provide stress relief within the joint, novolacs can be co-cured with, particularly, acrylonitrile butadiene elastomers. 

Although unmodified phenolic resole adhesives can give bonded structures that will exhibit excellent durability - both thermal oxidative resistauce aud resistance to harsh environments such as oil, sea water, natural weathering - they are inherently brittle. Much research work has been carried out over the years to impart some degree of toughness into these systems and at the same time to reduce the shrinkage on cure and, thus, provide some stress relief. However, toughening, in the sense understood with epoxy adhesives, is not really possible with these resins. 

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