Cure paths

Data from experiments with the flash lamp exposure demonstrate that the radiation cure path may be highly affected by the temperature. These results are presented In Figure 4, where three major regions of density levels can be observed A, of the maximum density (Dmax) B, where densities are below Dmax and C, 1n which dye transfer Is not detectable. 

Specific diffusion control concerns translational diffusion of individual species (or reactive groups) and is characteristic for dilute solutions (e.g. free radical (co)polymerisation with the monomer as diluent). The diffusion rate of the active centres then depends on the molecular weight of the molecules to which they are attached, on their symmetry, on the composition and on the interactions. For example, in free radical polymerisations, a large difference between the size of polymer and monomer molecules (which remains the case along the entire cure path) is found and so a large difference in their diffusion coefficients is observed. 

The CHT diagram for the epoxy-amine system is given in Figure 2.32. The experimental points (symbols) in Figures 2.30-2.32 are data obtained with MTDSC and djmamic rheometry. The thick lines are the gelation lines, the vitrification contour (similar to the line of DF% f) and the isodiflfusion contours DF% g and DF. The thin lines display the Tg evolution as a function of time for selected isothermal (TTT) or non-isothermal cure paths (CHT). 

An ongoing effort of the consortium is the development of simulation software for offline light path development and analysis. This will permit car makers to develop and fine mne curing paths without interrupting production. 

Figure 8. The model is used with robot path simulation software to generate a proposed cure path for the entire part.

Polymerization. Thermal polymerization or curing of an ink film at elevated temperatures can foUow many different chemical paths. Condensation and cross-linking reactions may be accompHshed with or without the use of catalysts. However, this method of drying generally has not been widely used for printing inks, except those used for metal and glass decoration, and some clear coatings. 

V,/V dipheny1ethy1enediamine. The cure mechanism probably involves an amine-catalyzed decomposition of the sulfonyl chloride group or a path of radical anions. The cross-link probably involves the HVA-2. Calcium hydroxide or other SO2 absorbers must be included for development of good mechanical properties. 

The 2,6-DHMP condensation produced only one dimer and a significant amount of trimer as depicted in Scheme 8. The structure of the trimer was not reported. The reaction path is analogous to that of 2-HMP, but occurred at a faster rate. 2,6-DHMP was the only derivative to form a significant amount of trimer under the reaction conditions studied. This supports the idea that ortho-linked PF polymers should have a faster cure than others. It also points out the futility of attempting to manufacture an ortho-Ymkcd polymer under alkaline conditions. Extension of the polymerization process as depicted in Scheme 8 leads to a continual reduction in the amount of para functionality available for condensation as shown in Table 7. 

Tracers. To a mixt of 34 parts of Laminae resin, 4 of benzyl ale, 2 of Co naphthenate, and 4 of me et ketone peroxide is added an equal wt of a mixt of 1 part of powd Mg and 2 of K perchlorate, The mixt is formed and cured to give a tracer for following visibly the path of rockets (Ref 24). In Ref 16, p 275 are given formulations for mixts contg K perchlorate which is used in tracer ammo for automatic small arms. Tracer compns contg powd Zr which are suitable for modem HV small arms are discussed in Ref 30... 

It is possible to calculate a number of different kinds of "effective" crosslink densities. Bauer et al have used a quantity they termed the "elastically effective crosslink density " (Cel) correlate cure with solvent resistance and other physical properties of coatings (7-10). The correlation was basically empirical. Formally, the is a calculation of the number of functional groups attached to the infinite network for which there are at least two other paths out to the network on the given polymer or crosslinker. Thus, chains with only one or two paths to the infinite network are excluded. The following expression can be written for... 

Small cell lung cancer typically presents as extensive disease (approximately 60% to 70% of new cases) and progresses very quickly. Small cell carcinomas are very responsive to chemotherapy and radiation. Radiotherapy became the standard in 1969, when a randomized trial showed that it offered the potential for cure, whereas surgery did not.20 For the vast majority of patients, chemotherapy with or without radiotherapy is the treatment of choice. Even after a complete response to therapy, the cancer usually recurs within 6 to 8 months, and survival time following recurrence is typically short ( 4 months). This yields a typical survival rate of 14 to 20 months for limited disease and 8 to 13 months for extensive disease.33 Table 87-6 illustrates the general treatment path of SCLC. 

Ehnholt et al.8 produced a broad paper covering raw materials, and in-process and final-product measurements. While the uses are primarily in the food industry, the rancidity was often caused by microorganisms. One case involved off-flavor materials being produced in drying and curing ovens. Marker compounds (concomitant) released during the breakdown process (of saturated and unsaturated compounds) were nonenal, decenal, and octenone for the unsaturated aldehydes and ketones, and nonanal, decanal, and octanone for the saturated molecules. A 10-m folded path gas cell was used with an FT-IR for measurements down to 1 Lig/m3. 

Figure 3.19 Reaction paths undergoing phase separation during isothermal cure...

Part heat-up rate during autoclave processing can dramatically influence final part quality. At least three variables can affect the autoclave heat-up rate for composite parts (1) tool material and design, (2) the actual placement of the tool within the autoclave, and (3) the autoclave cure cycle used. Recommendations for the design of an individual tool are fairly obvious and well understood in industry (e.g., thin tools heat faster than thick tools materials with a high thermal conductivity heat faster than those with lower thermal conductivity and tools with well-designed gas flow paths heat-up faster than those with restricted flow paths [e.g., tools... 

If regulatory control is used, the cure cycles should be developed as efficiently and effectively as possible. The cost of cure cycle development is open-ended because there is no limit on the number of possible variations to cure cycles. There is no guarantee either that the results will be transferable to other processing equipment or materials because the relationship between primary and secondary variables is unpredictable in such complex, path-dependent processes. 

Other factors may also influence the path of the curing reaction, such as the presence of a catalyst, or of an initiator (see Sec. 2.3.4). 

The use of model compounds is a convenient starting point to determine the reaction path, particularly for stepwise polymerizations. For epoxy-amine systems, a monofunctional epoxide such as phenyl glycidyl ether (PGE) is often used for these studies (Verchere et al., 1990 Mijovic and Wijaya, 1994). Figure 5.10 shows the reaction scheme for the curing of a monoepoxide with a diamine. 

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