Curing optimization

VANDERHAEGHE L, Bouic p J D (2000) The Immune System Cure Optimize Your Immune System in 30 days - the Natural Way. New York Kensington Publishing Corp. 

We can, however, write a list of parameters for cure optimization. To limit the possible combinations, we assume that the composite composition is known (i.e., resin, fibers, geometry, etc., are given, and the mold design and mold material is known). This reduces the number of buttons for control of cure to the following ... 

A vacuum is then drawn inside the cover membrane (to remove volatiles and porosity) while the pressure and temperature inside the autoclave are separately controlled (to provide even control of pressure across the surface, and thermal control of cure). Optimization of the application of pressure and vacuum will prevent the formation of dry laminates (which typically occurs when pressure is applied too early and low-viscosity resin is forced out) and porous laminates (when pressure is applied too late with high-viscosity cured resins). In general, consistent mouldings of high quality can be produced, but the process is slow and capital-intensive. 

Carlone, P., Palazzo, G. S. and Pasquino, R. (2007), Pultrusion manufacturing process development Cure optimization by hybrid computational methods . Computers ... 

Joshi, S. C., Lam, Y. C. and Tun, U. W. (2003), Improved cure optimization in pultrusion with pre-heating and die-cooler temperature . Composites Part A Applied Science and Manufacturing, 34(12), 1151-1159. 

Palazzo G S and Carlone P (2006) Cure optimization in pultrusion process by a heuristic-analytical approach, Proc IMECE-Conf, Nov 5-10, paper 14468. 

Epoxidized phenol novolak and cresol novolak are the most common curing agents. The composition of the resin and hardener system is optimized for each specific appHcation eg, incorporating phenol novolaks in the matrix resin can iacrease cure speed. 

One of the conveniences afforded by curing PPS is that a single uncured feedstock can give rise to an entire family of cured polymers. The flow rates, ie, the extent of cure, of the cured polymers are optimized for specific appHcations. Table 1 shows typical melt flow values of cured PPS polymers for various types of appHcations. 

Whereas polyisobutylene and butyl mbber exhibit chain cleavage on free-radical attack, halobutyls, particulady bromobutyl and CDB, are capable of being cross-linked with organic peroxides. The best cure rate and optimal properties are achieved using a suitable co-agent, such as y -phenjiene bismaleimide. This cure is used where high temperature and steam resistance is required. 

The resistance to heat and aging of optimized EPM/EPDM vulcanizates is better than that of SBR and NR. Peroxide-cured EPM can, for instance, be exposed for 1000 h at 150°C without significant hardening. Particularly noteworthy is the ozone resistance of EPM/EPDM vulcanizates. Even after exposure for many months to ozone-rich air of 100 pphm, the vulcanizates will not be seriously harmed. EPM/EPDM vulcanizates have an excellent resistance to chemicals, such as dilute acids, alkaUes, alcohol, etc. This is in contrast to the resistance to aUphatic, aromatic, or chlorinated hydrocarbons. EPM/EPDM vulcanizates swell considerably in these nonpolar media. 

In order to optimize each embedding material property, complete cure of the material is essential. Various analytical methods are used to determine the complete cure of each material. Differential scanning calorimetry, Fourier transform-iafrared (ftir), and microdielectrometry provide quantitative curing processiag of each material. Their methods are described below. 

Press control is critical it is essential that the elastomeric compound reaches the required cure state to optimize product performance yet remains in the press the shortest time period to maximize productivity. To meet this objective, both compression and injection presses now use microprocessor controls, which enable variations in platen temperatures and compound cure characteristics to be accommodated without sacrificing product performance or productivity. 

Determination of mechanical properties like tensile strength, tear strength, modulus, and elongation at break are the most common methods adopted to determine the cured properties of short fiber-mbber composites. Murty and De [133] discussed the technical properties of short fiber-mbber composites whereas Abrate [8] reviewed the mechanism of short fiber reinforcement of mbber. Fiber concentration in the matrix plays an important role in the optimization of the required... 

Minimizing the cycle time in filament wound composites can be critical to the economic success of the process. The process parameters that influence the cycle time are winding speed, molding temperature and polymer formulation. To optimize the process, a finite element analysis (FEA) was used to characterize the effect of each process parameter on the cycle time. The FEA simultaneously solved equations of mass and energy which were coupled through the temperature and conversion dependent reaction rate. The rate expression accounting for polymer cure rate was derived from a mechanistic kinetic model. 

In order to understand the effect of each process variable, a fundamental understanding of the heat transfer and polymer curing kinetics is needed. A systematic experimental approach to optimize the process would be expensive and time consuming. This motivated the authors to use a mathematical model of the filament winding process to optimize processing conditions. 

At an A/E ratio of 1.05, wind time of 3.8 minutes and molding temperature of llO C, the curing profiles of the part were simulated varying the press temperature until the maximum exotherm temperature occurred at the center of the part. This condition was achieved at a press temperature of 135 C. The minimal cycle time at the optimal processing conditions was simulated to be eight minutes. 

Curing of Polyimlde Resin. Thermoset processing involves a large number of simultaneous and interacting phenomena, notably transient and coupled heat and mass transfer. This makes an empirical approach to process optimization difficult. For instance, it is often difficult to ascertain the time at which pressure should be applied to consolidate the laminate. If the pressure is applied too early, the low resin viscosity will lead to excessive bleed and flash. But if the pressure is applied too late, the diluent vapor pressure will be too high or the resin molecular mobility too low to prevent void formation. This example will outline the utility of our finite element code in providing an analytical model for these cure processes. 

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