Curing conditions optimization

The use of simulation tools (e.g., computer programs) to calculate curing conditions is an area of great interest and is increasingly used to optimize cure for several processes including LCM [32,35] however, there are some obstacles to the use of this advanced route, such as the need of ... 

Polyurethanes Polyurethanes appear to be promising and are regarded as compatible with explosives and propellants. However, some research is required to optimize satisfactory cure conditions. 

The amount of curing agent selected should be fine-tuned for the specific application. This can be done by varying the concentration over a narrow range and then testing performance to find which concentration is optimal. The optimized concentration should then be tested in the actual product and under end-use conditions since there may be other variables that affect performance (i.e., the mass and geometry of the joint, cure conditions, combinations of environmental conditions). 

Optimization of Cure Conditions During Processing of Acrylic Latex Coatings... 

Though sufficient experimental evidence is not presently available, the optimization of curing conditions should also play an important role in achieving maximum coherence in the network. 

Some of the problems seen with the commercially available polyimides such as limited shelf life,gelation and high ionic contamination are traceable to the raw materials themselves. A zone refining technique has been perfected for use with organic materials and these precursors have been used to synthesize ultrapure polyamic acids for IC device applications. The key feature of the synthesis is the use of solid ingots of the dianhydrides. Materials prepared by this technique show low metallic impurities and have been shown to be excellent film formers for a variety of applications. In particular a polyimide derived from PMDA-ODA has been used to passivate magnetic bubble devices. IR techniques coupled with electrical measurements have been used to optimize the cure conditions and a simple resist process has been defined to passivate these devices. Device performance compares well with conventional inorganic insulators. 

The cure times are determined via an Eekon Rheometer. An uncured sample is placed between two heated discs (150°C). As the sample cures, the viscosity increases. The cure condition, e.g. T90, is determined by the time required for the viscosity to increase to 90% of the difference between the minimum and maximum values. Samples cured at T60 and T75 represent various degrees of under curing. Samples cured at T90 and T90+1 (T90 plus one minute) represent optimal curing. To make an adequate matrix of conditions, each of the four portions was cured at two conditions, either T60 and T90, or T75 and T90+1. Current production would be represented by 100% T90+1 , as a bold X in Table I. 

Matrices for high-performance epoxy composites should exhibit a sufficiently high modulus, strength, temperature resistance and toughness. Also the flow properties during cure should be programmable in order to optimize the curing conditions. 

Figure 6.1 Adhesive strength of epoxy-aluminum joints as a function of the applied etching pretreatments (a) abrasion, (b) alkaline, (c) optimized FPL, and (d) P2 (adhesives Ceys, 2MI, PAMS, and DDS are based on diglycidyl ether of bisphenol A, Diglycidyl ether of bisphenol-A(DGEBA), and differ in composition and/or cure conditions). ...

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. 

Accelerators are added to thermosets and rubbers to speed-up the curing or vulcanisation process to such an extent that an end product can be formed under optimal conditions. 

An optimization of the cure schedules and processing parameters consists of exploring the most favorable conditions, judged under specified criteria, that will lead to a product... 

The modeling of residual stress development during cure can be used to optimize the processing conditions to reduce or control residual stresses. The current process model is used next to assess the effects of several processing conditions on residual stresses. Reduced cure temperature, longer dwell times, slower cool down rate, and the use of novel cure cycles are all feasible for the reduction of residual stresses. 

In process design, the main objective is to optimize the cured properties of the finished product. To that end, the following conditions have to be established and quantified ... 

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