Cure, experimental procedures

The Impedance Analyzer was controlled by a 9836 Hewlett-Packard computer which also controlled the time-tempe ture of the press. Measurements at frequencies from 5 to 5 x 10 Hz were taken at regular Intervals during the cure cycle and converted to the complex permittivity. Further details of the experimental procedure has been given elsewhere [10]. 

Either for quality control purposes or to estimate degree of cure, a variety of non-standard experimental procedures have been reported. Generally, the intention is to simplify the test, speed up quality control or to use very small non-standard test pieces. An example which has gained acceptance as a... 

The purpose of this review is to summarize the baac features and utility of the TTT cure diagram, discuss the experimental procedures for obtaining a diagram, present experimentally-obtained diagrams for model systems, and describe recent models that have attempted to calculate the time to vitrification on isothermal polymerization. This review will concentrate on TTT diagrams of epoxy systems. 

Differential scanning calorimetry (DSC) was used in investigating the curing kinetics of the unsaturated polyester resin. For the study, we used a DuPont 1090 Thermal Analyzer, equipped with a 910 DSC Module. Indium was used for temperature and calorimetric calibrations, following the procedure described in the operating meinual of the instrximent. The experimental procedure employed is very similar to that described in the literature (8-13) cind we have discussed it elsewhere (14). 

The experimental and theoretical methods of measuring or calculating the kinetic and thermodynamic properties of reactions of thermal electrons are important to physical chemistry. The ECD method will be compared to other methods. The CURES-EC procedure can be applied to other energetic quantities. We present a method to consolidate diverse data into pseudo-two-dimensional potential energy curves for these reactions [9, 10]. 

It was possible to obtain better resolution for these compounds because there are three independent experimental methods for estimating the electron affinities that could be iterated to consistency. These were the ECD measurements, half-wave reduction potential measurements, and electronegativity values. In addition, these electron affinities had been calculated with the MINDO/3 procedure. We also calculated the values using the CURES-EC procedure and obtained estimates of the charge densities. These procedures were extended to a larger set of 80 compounds, some without gas phase Ea that will be discussed in Chapter 10. 

The linear acenes, benzene to pentacene, are used as examples of the CURES-EC procedure. The results obtained utilizing MINDO/3 and AMI are compared. In addition to calculating the Ea by subtracting the energies of the optimized form, the LUMO of the neutral is compared with the experimental Ea. The electron affinity of hexacene has been estimated from the electronegativity and experimental ionization potential. As a further example of the use of CURES-EC, both the ionization potential and electron affinity of heptacene are estimated. The Ea of octacene and nova-cene are calculated for comparison to values obtained by using Koopman s theorem and a semi-empirical method based on a variable-parameter modification of the Pariser Parr Pople (PPP) approximation to the Hartree Fock equation [10]. 

Speedy and accurate desktop computers and modern programs such as HYPERCHEM place quantum mechanical calculations within the reach of any experimental chemist. The CURES-EC procedure simulates equilibrium methods of measuring electron affinities by calculating the difference between the optimized forms of the anion and neutral. The READS-TCT determination of charge densities in anion complexes simulates thermal charge transfer experiments. The effect of... 

The TCT Ea of perfluoromethylcyclohexane is confirmed with NIMS data and the Ea of perfluoromethylcyclopentane is reported. The EDEA for the loss of the tertiary fluorine atom is determined for both these compounds. In many cases the NIST values for fluorinated hydrocarbons could be for excited states. In all but a few of the cases, there is only one experimental determination of the Ea so confirmation using the CURES-EC procedure is important. 

This pe r discusses the chaniced reactions involved in the curing of fluoroelastomers with bis- henols and with peroxides. The mechanism of enuring with peroxides is based on cxir work where bromine was introduced in the polymer by cxjpolymeriza-tion. The experimental procedures and materials have been described in detail in previous publiceticxis (5,6c). 

Measurement of C requires more sophisticated and expensive rheometers and more involved experimental procedures. It must be remembered that experiments have to he carried out below the critical strain value (see Sec II), or in [he region of linear viscoelastic behavior. This region is determined by measuring the complex modulus G as a function of the applied strain at a constant oscillation frequency (usually 1 Hz). Up to 7, G does not vary with the strain above Yr, G tends to drop. The evaluation of oscillatory parameters is more often restricted to product formulation studies and research. However, a controlled-fall penetrometer may be used to compare the degree of elasticity between different samples. Creep compliance and creep relaxation experiments may be obtained by means of this type of device. In fact, a penetrometer may be the only way to assess viscoeIa.sticity when the sample does not adhere to solid surfaces, or adheres too well, or cures to become a solid or semisolid. This is the case of many dental products such as fillings, impression putties, sealants, and cements. 

Adanur, S., Arumugham, Y. Characteristics of ultraviolet cured glass-epoxy textile composites. Part 1 experimental procedures and testing. J. Ind. Text. 32, 93-106 (2002)... 

The experimental technique used to obtain the cure curves and a detailed examination of the procedure used to generate the rate constants, an iterative procedure to determine the best values of and k based on the set of differential equations describing the cure process, for these systems will be discussed. 

Experimentally a cyanate ester precursor mixture consisting of BPEC, 1 wt % BPE, and 100 ppm cobaltacetylacetonate was prepared and subsequently mixed with the cyclohexane phase separating solvent [86]. Essentially the same procedure as for the epoxy is used for sample preparation with the difference that the curing was done at 80 °C and post drying at 240 °C. 

Extensive experimental testing was performed on IM6/3100 to obtain longitudinal and transverse stiffnesses and major Poisson s ratio as a function of degree of cure. A detailed explanation of the test procedure can be found in [5], The model predictions and experimental results for this material system are shown in Figures 8.11-8.13. From these relations the lamina stiffnesses Qy can be obtained from... 

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