Effect of Cure Temperature

If the phase separation proceeds much faster than the cure rate, then the morphology is controlled by the phase separation rate rather than by the cure rate. The diffusivity of the thermoplastic in the thermoset becomes the most important factor. The increase of the diffusivity with increasing cine temperature causes the increase in the particle size. 

On the other hand, if the cure rate is much faster than the phase separation, then the morphology is controlled by the cure rate through a chemical pinning process. In this system, phase separation is mainly controlled by the cure rate of the epoxy matrix. Faster curing rates and shorter gel times lead to smaller PEI-rich particles with an increasing cure temperature. The temperature effect on the viscosity of reaction mixture is relatively small (i.e., the complex viscosities measured by Physica are 7 and 4 Pa.s at curing temperatures of 150 and 190°C, respectively). 

In the composition range where the nodular morphology was shown, because the matrix (PEI phase) contained relatively small amount of epoxy, the temperature effect on the viscosity was larger than the reaction effect. Thus, the viscosity of the PEI matrix in the nodular morphology became reduced as the cure temperature was increased, which made epoxy nodules coalesce more easily with each other. As the cure temperature is increased, the viscosity of the PEI-rich matrix decreases from 210 Pa.s at 150°C to 50 Pa.s at 190°C. 

The dual-phase morphology of the PEI/epoxy blend was observed in the composition range of 13—18wt%, 14—20wt%, and 15-20wt% PEI when curing temperature was 150, 

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The difference in degree of cure of the blends by different curatives has also been explained on the basis of changes in curative distribution with accelerator types and the effect of cure temperature. The tensile properties of the blend cured by S/ZDEC at 170°C were significantly lower and modulus was higher than those cured by S/MET and S/DPG as shown in Table 11.17. Lowering of cure temperature by 20°C significantly improved these properties. However, the standard deviation in the results increased limiting the potential for any solid conclusion. 

The MRC cycle calls for a 182°C cure temperature. The effect of cure temperature on residual stress was investigated by curing specimens at four other cure temperatures (171, 165, 160, and 149°C) while holding the dwell time (4 hours) constant. In Figure 8.18 the dimensionless curvature for these specimens is plotted versus the cure temperature. The curvature is reduced as the cure temperature is decreased with significant reduction in curvature obtained for dwell temperatures of 165°C or less. The final curvature as predicted by the viscoelastic process model is overlaid with the experimental data in Figure 8.18 and is shown to capture the trend. 

Figure 8.18 Effect of cure temperature on dimensionless curvature [model and experimental results]...

Table 8.3 Effect of Cure Temperature on Degree of Cure and Transverse Mechanical Properties...

Figure 4. Effect of curing temperature on tensile characteristics of a typical PVC plastisol propellant (17)...

The effect of cure temperature is more difficult to analyze. An increase of cure temperature produces three different effects an increase of the reaction rate, a decrease of the viscosity, and an increase (UCST) or a decrease (LCST) of the initial miscibility. It has been observed that as the viscosity at the cloud point, r CP, decreases there is an increase in the average size of dispersed phase particles and a corresponding decrease in their concentration. 

Caravajal et al.22 discussed the effect of curing temperature on the silane conformation. APTS modified silica was cured at variable temperature and 2,Si CP MAS NMR spectra were subsequently recorded. Results for the modification of silica gel pretreated at 473 K are given in figure 9.20. Other reaction parameters were comparable to the study reported above. 

These aliphatic amines can also be cured at elevated temperatures to provide a more densely crosslinked structure with better mechanical properties, elevated-temperature performance, and chemical resistance. Table 5.3 illustrates the effect of curing temperature on the bond strength of DGEB A epoxy with two different aliphatic amines. 

TABLE 5.3 Effect of Curing Temperature on Bond Strength of DGEBA Epoxy Resin Cured with Two Different Aliphatic Polyamines6... 

D.Wilson, J.K. Wells, J.N. Hay, D. Lind, G.A. Owens F. Johnson (1987), SAMPE J., 23, 35-42. Preliminary investigations into the microcracking of PMR-15 graphite composites. 1 Effect of cure temperature. 

The kinetic hydration of cement is widely studied in the literature and some of these papers reported the chemical, physical and mechanical behaviour [2-5], Simplified models were used by Knudsen[6], Basma et al [7], Schindler and Folliard [8], Bentz [9]. The majority of these models are empirical, based on experimental observations of macroscopic phenomena, and they take into account the effects of curing temperature, water-cement ratio, fineness, particle size distribution and chemical composition of cement [5]. 

F. Lin and C.Meyer, Hydration kinetics modeling of Portland cement considering the effects of curing temperature and applied pressure. Cement and Concrete Research, Vol 39 (2009) p.255... 

Figure 3.2 Effect of cure temperature and sulfur level (pphr) on modulus...

Mohapatra P, Dung MX, Choi JK, Jeong S, Jeong HD (2011) Effects of curing temperature on the optical and charge trap properties of InP quantum dot thin films. BuU Korean Chem Soc 32 263... 

P. Rovnanik, Effect of curing temperature on the development of hard structure of metakaolin-based geopolymer, Constr. Build. Mater. 24 (2010) 1176-1183. 

The effects of cure temperature and amount of catalyst on the rheokinetical behavior of an MF resin can be followed using dynamical mechanical techniques (127), and time-temperature-transformation (TTT) cure diagrams can be constructed using the results of these methods (127-129) (see Dynamic Mechanical Analysis). 

The effect of cure temperature on the cure kinetics and cure state profile of a simple carbon black filled, sulfenamide/sulfur cured natural rubber compound is shown in Figure 6 (16). As shown in the growth of the cure state, an article which would require 110 min to cure to its maximum cure state at 125°C can be cured at 135°C in 50 min, at 150°C in 18 min, at 165°C in about 7 min, and at 182°C in about 3 min. However, the maximum state of cure achieved keeps dropping as cure temperature increases. 

Wang, K., Shah, S. P. Mishulovich, A. (2004). Effects of curing temperature and NaOH addition on hydration and strength development of clinker-free CKD-fly ash binders, Cem Conor Res, 34(2), 299-309. 

Details of the paste (P) and mortar (M) mixes investigated are given in Table 43. Mortars were made using a sand to binder ratio of 2.7 with different L/S ratios. The semi-dry paste investigated was similar to the mix used in the site tiial, i.e. Coventiy Binder (COV). Samples were cured at 20° C and 98% RH, though the paste and mortar mixes made with the Coventiy Binder were also placed at 40° C to investigate the effect of curing temperature on the expansion of this novel blended binder. 

TEOS-GPTMS Substrate deflection Effects of curing temperature on residual stress Robertson (2003)... 

Kokubu, K., Takahashi, S., and Anzai, H., Effect of Curing Temperature on the Hydration and Adiabatic Temperature Characteristics of Portland Cement - Blast Fnmace Slag Concrete, 3rd CANMET/ACI Int. Conf. Fly Ash, Silica Fume, Slag and Natural Pozzolans in Conor., (V. M. Malhotra, ed.), SP-114 1361-1376 (1989)... 

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