Curing rheology

Selection of the proper viscosity and cure rheology are very important due to the occurrence of high shear and fast cures. 

An appropriate cure cycle was established based on the results obtained from the thermal analysis and cure rheology studies of the resin and cured BCB bar and dogbone shaped samples were fabricated for testing. Bar shaped specimens had the dimensions of 3.5 x 0.5 X 0.125 and were used to stake compact tension specimens for fracture toughness studies and for dynamic mechanical analysis of a torsion bar. Dogbone shaped specimens for tensile tests had a gauge area of 1 x 0.15 and were approximately 0.040 thick. 

Cook, W.D. Dean, K. Forsythe, J. Cure, rheology and properties of IPN thermosets for composite applications. Materials Forum 2001, 25, 30-59. 

Sun et al. (2006) examined the use of novel silica nanofillers in underfill for flip-chip applications, and showed that pre-cure rheology and post-cure values of Tg are effected by nanosilica surface treatment. 

Injection molding is increasingly used in the rubber industry and fluorocarbon elastomers are well suited for this technique. Viscosity and cure rheology are very important because of high shear and fast cures (50-54). Molding at 180-200°C allows operations of 5 min or less, depending on part size. 

Chemical State-of-cure Purity Glass transition transition State-of cure Rheology Glass Rheology... 

Figure 4.3 Influence of morphology on the showing the final morphologies of the cured rheological behavior of epoxy resins with differ- blends. Reproduced with permission from ent content of thermoplastics (polyetherimide). Ref. [49] 1999, American Chemical Society. Transmission electron microscopy images...

Adhesive Properties. Adhesive performance depends on its ability to flow, wet, and penetrate the fiber walls, and to cure within prescribed temperature and time limits. The cured adhesive must have enough cohesive strength to impart the desired physical strength properties to the composite. Insights into the effects of formulation variables on resin cure rheology are gained with the aid of state-of-the-art as well as simple instrumental and observational methods. 

Synthesis parameters are modified, as with the PFs, to alter resin properties. Molar ratio, catalyst system, raw material concentration and their rate of addition, target nonvolatiles, a dehydration step and additives may all be varied to modify and impart special properties to a resin. Properties monitored may include molecular weight, molecular weight distribution, functional groups, cure rheology, viscosity, and cure speed. 

Tests on raw or compounded but unvulcanized materials are chiefly concerned with rheological properties, that is, the response to the forces imposed during the operations of mixing, extmsion, calendering, and curing. 

Inks. Refined kaolin is a common ingredient in a large variety of printing inks (qv). In addition to extending the more expensive polymers present, ka olin also contributes to improved color strength, limits the penetration of the ink into the paper, controls rheology, and improves adhesion. Kaolin for this appHcation must usually be as white as possible and free from oversize particles. Surface treated clays are used to improve compatibiHty with oil-based ink. Clays can also be an ingredient in the newer water-based or uv-cured inks. 

Compound processibiUty is a key factor in the optimiza tion of new polychloroprene types. As a result, commercial compounds can be mixed, shaped, and cured by virtually all the methods used in the mbber industry. A typical polychloroprene compound includes a variety of additives designed to improve compound rheology, cure rate, and vulcanizate properties. 

Silicone adhesives are generally applied in a liquid and uncured state. It is therefore the physical and chemical properties of the polymers, or more precisely of the polymer formulation, that guide the various processes leading to the formation of the cured silicone network. The choice of the cure system can be guided by a variety of parameters that includes cure time and temperature, rheological properties in relation with the application process, substrates, the environment the adhesive joints will be subjected to and its subsequent durability, and of course, cost. 

The role played by the various ingredients in the composition of sealant, and in particular on the durability of adhesion has been discussed recently [77]. Inert plasticizers, such as trimethylsilyl-endblocked-PDMS, are typically added to silicone sealant compositions in order to adjust the rheology of the uncured sealant. They result in a reduction of the modulus and hardness of the cured sealant. Differences in the durability of silicone sealants are found to be due to differences in their cure chemistry, and more specifically to the nature and... 

When formulating a silicone adhesive, sealant, or coating, based on hydrosilylation addition cure, one must consider the following properties of the uncured product pot life, dispensing technique, rheology, extrusion rate, cure performance. These characteristics directly affect the processing properties of the polymer base or crosslinker parts. The degree of cure conversion at the temperature of interest is determined by properties such as tack free time, cure profile and cure time. Once... 

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

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