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Dilatometers, dilatometry

The kinetics were studied by adiabatic calorimetry [18] and high vacuum isothermal dilatometry [21, 22]. The calorimeter and the dilatometers were fitted with electrodes [21] for measuring the conductivity of the reaction mixtures. [Pg.676]

Dilatometry and Dilatometers, P.H. Plesch, International Laboratory, October 1986, p.18-29. [Pg.780]

The decomposition of initiator can be followed by usual analytical methods and k can be determined. The efficiency factor/can be obtained by comparing the amount of initiator [I] decomposed with the number of polymer chain formed. The rate of polymerization can be determined by monitoring the change in a physical or chemical property of the system. Generally, dilatometry technique is used for determination of the rate of polymerization. Let the extent of polymerization be small and concentration of initiator be constant. Let r0, rt and r be the readings on dilatometer initially, at time t and at the completion of reaction, respectively. If reaction is first order in [M],... [Pg.129]

Dilatometric methods. This can be a sensitive method and relies on the different phases taking part in the phase transformation having different coefficients of thermal expansion. The expansion/contraction of a sample is then measured by a dilatometer. Cahn et al. (1987) used dilatometry to examine the order-disorder transformation in a number of alloys in the Ni-Al-Fe system. Figure 4.9 shows an expansion vs temperature plot for a (Ni79.9Al2o.i)o.s7Feo.i3 alloy where a transition from an ordered LI2 compound (7 ) to a two-phase mixture of 7 and a Ni-rich f c.c. Al phase (7) occurs. The method was then used to determine the 7 /(7 + 7O phase boundary as a function of Fe content, at a constant Ni/Al ratio, and the results are shown in Fig. 4.10. The technique has been used on numerous other occasions,... [Pg.95]

A dilatometer consists essentially of a glass tube (the body ), containing the reaction mixture, to which a straight capillary tube is attached (usually, but not always, vertical). The movement of the meniscus of the reaction mixture in the capillary amplifies changes in the volume of the reaction mixture and is measured, as a function of time, with a cathetometer or by some automatic device. Dilatometry has been used for a very long time because it is simple, cheap, convenient and can be made very accurate. [Pg.85]

Dilatometry is a convenient method for measuring polymerization rate. The method is based on a decreasing volume of the examined system along with conversion of monomer to polymer. For simple polymerization, usually carried out in solution in capillary dilatometer, the decrease in volume, Av, is calculated from measurements of the decrease in the level of reacting mixture ho - h = Ah in capillary with radius, r. Using equation ... [Pg.135]

In dilatometry, specific volumes V or densities of materials are measured by use of a pycnometer, dilatometer, or density-gradient column. The data obtained are then interpreted through the equation... [Pg.37]

An interferometer can be used to very accurately measure the thermal expansion of solids. Although not utilized commercially to the level of dilatometry, NIST standard materials, which are in turn used to calibrate dilatometers, have had their expansion characteristics determined using interferometry. In fact, the formal definition of the meter is based on interferometric measurements. The operation of the device is based on the principle of interference of monochromatic light. The fundamental relations between wavelength and distance will first... [Pg.186]

Dilatometry is one of the older classic methods for the determination of transition points between solids (Drucker 1925). The dilatometer usually consists of a large bulb connected to a capillary and filled with an inert liquid. Volume changes as a function of temperature or resulting from a solid-solid transition may be determined by changes in the volume of the inert liquid. The recent advances in the miniaturization of chemical instrumentation (e.g. Jakeway ef a/. 2000 Krishnanefa/. 2001), and the high precision associated with that miniaturization may lead to a renaissance of the use of some of these classic techniques and their applications to the study of polymorphism. [Pg.147]

When composite resins undergo polymerization they shrink slightly [21,58]. This is because, in an addition polymerization, the free volume occupied by the double bonded end of a monomer molecule is greater than that occupied by the equivalent single bond in the polymer molecule. This effect classically allows addition polymerization to be studied by the technique of dilatometry, whereby the reduction in volume of a substance such as methyl methacrylate is followed by observing the contraction in a narrow-bore tube of a device known as a dilatometer [59]. [Pg.45]

Indirect methods for investigating polymerizations, which do not require isolation of the polymer, allow the polymerizations to be followed continuously. Dilatometry is particularly accurate. It measures the contraction of a polymerizing mixture. A dilatometer consists of precision tubing, 3 mm in diameter, to which a reaction vessel of 4-8 cm in volume is glass blown or joined. First, the initiator is added. The monomer is then distilled in from the monomer reservoir, preferably under nitrogen, and the dilatometer is placed in a thermostatted water bath. The yield u is determined from the observed volumes Vo at time zero and Vt at time /, of the monomer/polymer mixture and the partial specific volumes, Vmon of the monomer and Vpoi of the polymer ... [Pg.70]

Polymerization rates were determined by recording capacitance dilatometry . In these experiments S (1.90 g), AN (1.1 g), and the appropriate solvent (50 ml) were heated in the dilatometer with tBPP (0.06 g) and ZnCla (0.22 g) when required. [Pg.108]

Sample density can be measured using a variety of methods density-gradient column, dilatometry, pycnometry, and flotation or buoyancy. The density-gradient column approach is probably used most frequently to determine sample densities for crystallinity measurements. When thermostated and appropriately calibrated with floats, this approach permits measurements to accuracies of 0.2 mg/cm or better. Dilatometers are well suited for measuring specific volumes and following crystallization, as a function of temperature. [Pg.1994]

The problem here was to obtain samples for particle size and conversion analysis from the same reaction mixture during a single run in order to avoid errors in reproducibility which are rather high in flocculating systems. A dilatometer described earlier was modified so that two chambers were provided which contained initially the same reaction mixture, one for electron microscope (e.m.) samples and the other for dilatometry. The two chambers are connected at the start of the reaction but are separ-... [Pg.75]

The techniques discussed may be viewed as a fonn of dilatometry, and a glass dilatometer was, in fact, used by Laita (23) to study the polymerization of etl lene in benzene at pressures which were not recOTded, but must have been as h%h as about 50 atm in some cases. Here, too, recourse had to be taken to gravimetric calibration of the volume change of polymerization, particularly, since a liquid and a gas phase must have coexisted. [Pg.402]

This equation then allows the crystallization process to be monitored by measuring how the specimen volume changes with time. In practice this is normally done by dilatometry. The crystallizing polymer sample is enclosed in a dilatometer and the change in volume is monitored from the change in height of a liquid which is proportional to the specimen volume. In terms of heights measured in the dilatometer Equation (4.24) can be expressed as... [Pg.280]

Unfortunately, classical dilatometers cannot be operated at high cooling rates because of the temperature gradient occurring within the sample. This problem can be solved by modeling the dilatometry experiment [28] or by designing novel setups [29, 30] special injection mold [29], miniaturized dilatometer [30], and so on. [Pg.436]

Dilatometry. A vitreous silica dilatometer is the basis of ASTM method D696 (27). A specimen with flat, parallel ends is placed in the bottom of an outer dilatometer tube with an inner tube resting on its upper end. A linear variable differential transformer (Ivdt) is attached to the outer tube and is in contact with the top of the inner tube. To prevent indentation of the specimen by the inner tube, thin metal plates are attached or glued to the ends of the specimen. The lower part of the dilatometer containing the specimen is allowed to equilibrate alternately in constant-temperature baths maintained at -30 and at 30°C. By measuring precisely the temperatures of the baths and the change in dimension of the specimen from the output of the calibrated Ivdt, the linear thermal expansivity may be calculated with the help of equation 6. [Pg.1173]


See other pages where Dilatometers, dilatometry is mentioned: [Pg.329]    [Pg.323]    [Pg.85]    [Pg.85]    [Pg.311]    [Pg.29]    [Pg.74]    [Pg.47]    [Pg.36]    [Pg.50]    [Pg.3027]    [Pg.448]    [Pg.77]    [Pg.135]    [Pg.407]    [Pg.133]    [Pg.767]    [Pg.26]    [Pg.782]    [Pg.6991]    [Pg.170]    [Pg.215]    [Pg.71]    [Pg.338]    [Pg.77]    [Pg.439]   
See also in sourсe #XX -- [ Pg.85 , Pg.86 , Pg.87 , Pg.88 , Pg.89 , Pg.90 , Pg.91 , Pg.92 ]




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