THERMOCHEMICAL CURE

EB irradiation (like the other ionizing radiation techniques) can bring about the vulcanization of saturated chemically inert polymers which cannot be achieved in the conventional thermochemical curing methods [44]. 

Thermochemical submodel The thermochemical submodel provides temperature, viscosity, degree of cure (for thermosets), crystallinity (for thermoplastics), and the time required to complete the cure process. 

The energy equation, with temperature varying as a function of radial, circumferential, and axial position and time, is the basis of the thermochemical submodel. The energy absorbed or released during the cure or crystallization of the matrix is included in the energy balance. The appropriate multidimensional energy equation is Equation 13.1,... 

Thermoplastic elastomers based on polyolefins (TPO) are blends of PE or PP wifh EPDM elastomers wherein the elastomer is often cross-linked using thermochemical systems. TPOs more suitable for medical producfs with no chemical residuals can be made using EB processing to cross-link the elastomer portion in such an elastomer-plastic blend. The thermoplastic governs the melt transition, and thus the extrusion properties of TPOs. The radiahon response of these materials is also governed by the choice of fhe thermoplastic. An example of an EB cured blend of EPDM and polyefhylene used is for fluid transmission tubing and electrical insulation. ... 

Li, M. Tucker, C.L. Optimal curing of thermoset matrix composites thermochemical and consolidation consideration. Polym. Compos. 2002, 23, 739-757. 

Ti02 to obtain enhanced response for decomposition in the visible region [81], Because photocatalyhc reactions are not thermochemical, it is not necessary to supply heat. They proceed at temperatures available in the ambient environment. The required UV light intensity is not more than about 0.1 mW cm , which corresponds to the intensity level of outdoor sunlight that can be found on a cloudy winter day. Outdoor experiments have confirmed that photocatalyhc effects can be observed from sunrise to sunset. Photocatalysts, however, are by no means a cure-all. Further efforts are necessary to use fully their special characteristics. 

Carlone and Palazzo (2008) developed a computational modelling of microwave assisted pultrusion. This model is based on an electromagnetic submodel, meant to evaluate the electric field distribution and the heat generation rate due to the microwave source and on a thermochemical submodel, used to determine the temperature and degree of cure distributions. The performed simulations revealed the relevance of design of the microwave cavity, the curing die, and the importance of the dielectric properties of the materials in microwave pultrusion process. 

Thermochemical module predicts internal temperature in the structure and tooling and the resin degree of cure in composite structural components. 

The boundary conditions that may be used with the thermochemical module include specified boundary temperature, convective heat transfer or no heat transfer (adiabatic). Different conditions (e.g., different HTCs) can be applied to each element as desired. Either explicit or implicit techniques may be chosen to solve the heat transfer (Eq. [13.1]) and cure rate equations. Using either technique, these two equations are uncoupled during each solution time-step. This approach facilitates a simplified and modular solution procedure and is sufficiently accurate if small time steps are used. 

This is particularly significant since it showed that the composite continued to cure after the curing light was extinguished. This is direct evidence that a dark reaction is occurring and that two separate chemical reactions take place. The first is the photochemical reaction which initiates the polymerization of the monomers and the second is the thermochemical reaction which continues this polymerization. 

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