Effect of curing

Types of Latex Compounds. For comparison with dry-mbber compounds, some examples of various latex compounds and the physical properties of their vulcanizates are given in Table 23. Recipes of natural mbber latex compounds, including one without antioxidant, and data on tensile strength and elongation of sheets made from those, both before and after accelerated aging, are also Hsted. The effects of curing ingredients, accelerator, and antioxidant are also Hsted. Table 24 also includes similar data for an SBR latex compound. A phenoHc antioxidant was used in all cases. 

Table 5. Effect of Cure System on Processing Safety and Compression Set Resistance for FKM2260 ...

Figure 24.9. Effect of cure time on some properties of M-F mouldings. Cure temperature cellulose filled 295-308°F mineral filled 300-320°F O glass-filled material, asbestos-filled material, A cellulose-filled material (a) Cross-breaking strength (b) tensile strength (c) impact strength (d) impact strength (e) water absorption (rag), boiling water 30 min (f) cold water 24 h, 23°C ...

Table 6 Effect of Cure Inhibitor Concentration on the Charpy Notched Impact Strength (ak) at O C...

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. 

Burton HR, Bush LP, Hamilton JL (1983) Effect of curing on the chemical composition of burley tobacco. Recent Adv Tob Sci 9 91-153... 

Chamberlain WJ, Chortyk OT (1992) Effects of curing and fertilization on nitrosamine formation in bright and burley tobacco. Chemical composition of nonsmoking tobacco products, Beitr Tabakforsch 15 87-92... 

Fig. 3.10. Effect of curing cycle on the fraction of amine curing agent estimated to have diffused out of droplets as a function of their size. After Rao et al. (1991).

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 3. Effect of curing time on tensile strength of a PVC plastisol for various curing temperatures (17)...

Effects of Curing Agent Type. Epoxide-Cured Propellant. Carboxyl-terminated polybutadiene is a linear, difunctional molecule that requires the use of a polyfunctional crosslinker to achieve a gel. The crosslinkers used in most epoxide-cured propellants are summarized in Table IV and consist of Epon X-801, ERLA-0510, or Epotuf. DER-332, a high-purity diepoxide that exhibits a minimum of side reactions in the presence of the ammonium perchlorate oxidizer, can be used to provide chain extension for further modification of the mechanical properties. A typical study to adjust and optimize the crosslinker level and compensate for side reactions and achieve the best balance of uniaxial tensile properties for a CTPB propellant is shown in Table V. These results are characteristic of epoxide-cured propellants at this solids level and show the effects of curing agent type and plasticizer level on the mechanical properties of propellants. 

Figure 7. Effect of curing agent and plasticizer on the elongation of polybutadiene propellant...

Table XIV. Effect of Cure Time on the Useful Life of SD-851-2 Liner...

The effect of curing on the diffusion of polymer and the curing agent is studied for the system of hydroxyl-terminated polybutadiene (R-45-M)/isophorone disso-cyanate (IPDI). Both components contribute to the echo intensity and the plot of In P(x)/I(0)] vs (G5)2 (A — 5/3) consists of two exponentials (Eq. (22)) the fast component (the steep intial slope) is attributed to the IPDI, and the long component to the R-45-M. The dependence of both diffusion constants on the curing time is shown in Fig. 19. The accuracy for Dfast data is less pronounced than for the polymer D(Mn), because only the first few data points are relevant for its determination. Furthermore, the low tail of the R-45-M molecular weight distribution nearly coin-... 

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. 

TABLE 3.7 Effect of Curing Agents on the Shrinkage of Highly Filled Epoxy-Amine Systems during Cure16... 

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. 

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