Curing, energy requirements

The mould consists of 3 or more parts. The mould cavity is made in a conventional manner, but, mounted above and connected to it by a series of holes or transfer ports, is another cavity. The prepared rubber is placed in this upper chamber, and an integral ram is used to transfer the rubber into the mould cavities under pressure. The energy required to force the rubber into the cavities increases the temperature of the rubber mass as it flows through the connecting holes. As a result, curing times are significantly reduced. 

This equation, along with Equation 8.4, constitutes a coupled set of a differential equations governing the flow of thermal energy in a composite part during cure. Two boundary conditions (for temperature) and two initial conditions (for temperature and degree of cure) are required. An analytic solution to these equations is usually not possible. Numerical techniques such as finite difference or finite element are commonly used. 

Processibility is dependent on the viscosity or plastic flow of the rubber compound,i.e., resistance to flow. Plasticity or viscosity determines the energy requirement of the rubber during milling, calendering or extrusion while the time to the onset of curing, i.e., scorch time, indicates the amount of heat history which can be tolerated before the rubber is converted from the plastic to the elastic state at which time processing becomes virtually impossible. 

Mechanical Properties of Cast Resins. The toughness of the cross-linked polymers was determined by the area under the stress-strain curve and by the energy required to fracture. The fracture or impact energy, expressed in inch-pounds, was measured by a simple but reliable test— the Gardner impact—which consists of striking cured specimens with a 2-lb round-nose rod, %-inch in diameter, from various distances the test specimens were discs 0.1 inch thick by 2.0 inches in diameter. 

Water is sometimes used as a solvent for water-soluble resins. Certain epoxy adhesives are available as water-based emulsion or latex formulations. In the early 1970s, during the time of the petroleum crisis, water-based adhesives were thought of as a possible replacement for solvent-based adhesives systems. However, water-based adhesives never met the lofty expectations primarily because of the time and energy required to remove water from the bond line, the corrosion that the water causes in drying ovens, and the poor moisture resistance of cured water-based adhesives. 

Pigments generally inhibit uv curing to some degree since the pigments absorb and/or scatter uv radiation. This interferes with the ability of the photoinitiator to absorb the light energy required to initiate the polymerization reactions. Thus, the majority of commercial radiation curable adhesives are clear or contain silica. 

The Importance of Curing Conditions in Overall Energy Requirements for Organic Coatings... 

In almost all cases a radiation curable polymer can be manufactured under the same conditions as conventional solvent based coatings except for special handling of possible toxic materials. Thus, differences in total energy requirements for both manufacturer and use (application and cure) are directly relatable to the energy consumed in application and curing. 

The heat energy required to elevate this mass of coil to the cure temperature of 425 F from the ambient 70 F can be readily calculated, based upon the specific heat for aluminum of 0.215 BTU/lb/F. This heat input figure is found to be 2.45 x 10° BTU/hr. 

Finally, the energy required to evaporate one pound of water from the coating at 70 F to vapor at 600 F is found to be 1296 BTU/lb. These basic parameters/relations for the curing system can now be used in analyzing the energy requirement of the curing oven. 

Powers, H. R., "Electron Beam Curing for Coil Coatings, A Study of The Energy Requirements". Sherwin-Williams Company, 1975. 

Through the years, improved paints have been developed because of competition from environmental and consumer activists. The objective of improving overall quality and reducing emissions of VOCs has led to a wider selection of paint types. The user, therefore, must select a coating type that meets the cost of required application, equipment, energy costs for using, pollution and waste collection expenses, and application and cured performance requirements of the coating. 

A further alternative for cutting down on solvents is to work with radiation curing of wire enamel systems [176-178]. A characteristic property of UV-cur-ing systems is their very low energy requirement for the curing process, but the thermal stability of the obtained films requires improvement. The handicap is the double bonds, acrylic or olefinic, necessary for the curing reaction, which... 

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