Aging time

Fig. 2. Loss tangent as a measure of gelation time for a siUca sol (27) (a) loss (A) and storage (B) modulus as a function of aging time for H2O/TEOS mol ratio of 20 and HNO /TEOS mol ratio of 0.01 and (b) loss tangent as a function of aging time. To convert mPa to mm Hg, multiply by 7.50 x 10 . ...

Much work has been reported and summarized ia the Hterature on the matufing of various whiskeys ia charred or uncharred white-oak barrels (4—7). The early Hterature iadicates that total acids, aldehydes, esters, soHds, and color iacreased with aging time and that their concentrations were iaversely proportional to proof. Thus aging at higher proofs (over 127°) yields less color and flavor. The maximum allowable entry proof for straight whiskeys was iacreased from 110° to 125° by the U.S. Treasury Department ia 1962. 

Resistance to cutting depends on a number of factors, of which the shearing resistance of the precipitate lattice is only one. In fact the cutting stress increases with ageing time (Fig. 10.7). 

Bowing is easier when the precipitates are far apart. During ageing the precipitate spacing increases from 10 nm to 1 /am and beyond (Fig. 10.9). The bowing stress therefore decreases with ageing time (Fig. 10.7). 

Fig. 10.9. The gradual increase of particle spacing with ageing time.

Fig. 10.10. Detailed TTT diagram for the Al-4 wt% Cu alloy. We get peak strength by ageing to give 8". The lower the ageing temperature, the longer the ageing time. Note that GP zones do not form above 1 80°C if we age above this temperature we will foil to get the peak value of yield strength.

Fig. 7. Voigt model analysis of (a) lateral contact stiffness and (b) the response time, t, for a silicon nitride tip vs. poly(vinylethylene) as a function of frequency and polymer aging times. Reprinted with permission from ref [71].

In conclusion, the different thermal histories imposed to PTEB have a minor effect on the /3 and y relaxations, while the a. transition is greatly dependent on the annealing of the samples, being considerably more intense and narrower for the specimen freshly quenched from the melt, which exhibits only a liquid crystalline order. The increase of the storage modulus produced by the aging process confirms the dynamic mechanical results obtained for PDEB [24], a polyester of the same series, as well as the micro-hardness increase [22] (a direct consequence of the modulus rise) with the aging time. 

Figure 6 (a) Carbonyl index (at 1740 cm and (b) hydroxyl index (at 3550 cm ) versus aging time for CTA films X-control O-DHBP D-HMEP A-HBBP -DHBP-F -HMBP-F and A-HBBP-F. 

Figure 14 Weight loss of PMMA films versus aging time ...

Figure 13 Percent weight loss versus oven aging time for...

Fig.3. Amount of plates of the AlZn78 alloy against the ageing time at 533K.

The influence of ageing time at 533 K on the form of phases was shown in Fig.3. 100 /o of the irregular and globular types was observed after 3 hours of ageing, which was stated in the quantitative image analysis examinations. 

Fig, 20.54 Curves of strength against the logarithm of the ageing time for a precipitationhardening aluminium alloy aged at different temperatures... 

Polymers need activating by rapid agitation before use. They are more readily activated in soft, warm water (35-40 °C maximum). Maximum viscosity is reached after an aging time of 2 to 4 hours. 

TABLE 1a Composition of CI3,410 Sulfonation Products as a Function of Aging Time at 35-40°C... 

An important feature of sulfation chemistry is the thermal instability of the acid sulfate, which breaks down to a mixture of products including the parent alcohol, the dialkyl sulfate (R0S020R), the dialkyl ether (ROR), isomeric alcohols, olefins (R CH=CH2), and esters (R0S03R). Because of the thermal instability of the acid sulfate it is necessary to avoid high sulfation temperatures and to neutralize the acid sulfation product soon after its formation. An aging time of about 1 min at 30-50°C is adequate for the second reaction whereby the desired alkyl hydrogen sulfate is formed. In practice the minimum sulfation feasible temperature is determined by the need for the feedstock and reaction mixture to be mobile liquids (Table 3). 

Long (minutes) organic acid aging times (direct function of temperature)... 

Me-ester sulfonation has to be carried out at relatively high temperatures as the initial reactions and the decomposition of intermediate products is relatively slow compared with sulfonation reaction rates for alkylbenzenes, primary alcohols, ethoxylated alcohols, and a-olefins. The required aging time for conversion of the intermediates to FAME sulfonation acid is long (about 45 min at 85°C). It is not possible to sulfonate Me-esters without an excess of S03. 

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