Analytical method for determination of foam composite board
In principle, all methods sensitive to the phase structure of composite plates can determine the phase boundary, such as thermal analysis and dynamic mechanics; Or we can directly observe the phase structure and morphology, such as scanning electron microscope, transmission electron microscope and so on. An example of determining the phase boundary using the scattered light intensity I is given below.
For general multiphase blends, the size of dispersed phase usually ranges from hundreds of nanometers to tens of microns. The lower limit of this size is already equivalent to the wavelength of visible light. Therefore, when light passes through such materials, strong light scattering and turbidity will occur, while when it is single-phase, there will be no sudden change in the intensity of scattered light. Using this characteristic of light scattering, the phase boundary can be determined and a typical result is given. The temperature at which the scattered light intensity curve of Jinan foam composite plate changes suddenly with temperature is usually called "cloud point".
The phase boundary can be obtained by plotting the cloud point relative to the composition of the mixture of different composite plates. There are three limitations in the measurement of this method: the refractive index of polymer components should be quite different, and attention should be paid to the temperature coefficient of the refractive index. Otherwise, if the refractive index of two components is different and becomes equal when the temperature changes, the scattered light intensity will also decrease sharply, which may be mistaken for phase transition.
When the size of the dispersed phase is much smaller than the wavelength of visible light, for example, the microphase separation size of block copolymer is only a few nanometers to tens of nanometers, the method fails; The abrupt change of scattered light intensity is also affected by dynamic factors. Control, such as cooling or heating rate, change rate of phase area, etc., so the phase boundary measured by this method can not be called the solubility limit line of composite plate. Therefore, the combination method is usually used to determine the phase boundary of composite plates.
Application value analysis of foam composite board
When the ternary system of the composite plate is in a single-phase state, according to Gibbs' phase law, the degree of freedom can be calculated as f=4-1=3, including one temperature variable and two independent variables of phase components In the phase diagram, the single-phase region with three degrees of freedom occupies a certain temperature and composition range. Within this range, temperature and composition can change independently, and there is no mutual restriction between them. Its cross section can be of various shapes. Plan graphics.
In the ternary system, the degree of freedom in the two-phase equilibrium zone of Jinan foam composite plate is 2, which means that in addition to temperature, the composition of the coexisting two phases has an independent variable, that is, a component of a certain phase. Is an independent variable. The content of the other two components in this phase and the composition of the second phase are also determined accordingly and cannot be changed independently. In the ternary system, there is a conjugate relationship between the two equilibrium phases at a certain temperature. Both vertical and horizontal sections take a pair of curves as the boundary between them and the two single-phase zones.
The interface between two-phase region and three-phase region is composed of conjugate lines of two equilibrium phases at different temperatures. Therefore, in the horizontal section, the two-phase zone and the three-phase zone are separated by a straight line. This line is the temperature of the composite plate. A conjugate line.
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