Device for measuring the deformation of a material under the influence of heat and its application to the determination of the wetting power of pitches

A method and apparatus for optically making physical measurements of materials which deform upon application of heat thereto. The device comprises a source of light, an at least partly transparent chamber having a heating source which can be programmed to operate as a function of time, and with a porous support designed to support a deformable material within the chamber. A photo-electric receiver 5 and an optical lens 7 are also provided for imaging of the material during deformation on the photo-electric receiver. In order to perform the imaging, the source of light, the porous support, the photo-electric receiver and the optical lens 7 are optically aligned. In a specific application, the apparatus can be used to determine the wetting power of pitches.

BACKGROUND OF THE INVENTION 
This invention relates to an apparatus for measuring the deformation of a 
material under the influence of heat, and to a method of use of the 
apparatus for determining the wetting power of materials which deform 
under the influence of heat. More particularly, the invention has special 
application for measuring the deformation of pitches under the influence 
of heat and for determining the wetting power thereof. 
These are prior art methods known for measuring the temperature at which a 
material, when heated, passes from the solid state to the viscous state 
and then to the liquid state. By these methods, the ball and ring 
softening point or the Durran melting point, or the Kraemer-Sarnow (KS) 
softening point can be determined for thermoplastic materials. However, 
the prior art methods do not provide information on the behavior of the 
materials throughout the entire interval during which they are heated. 
It is often useful and necessary to know the nature of the change in the 
shape of a material being heated, and particularly, the changes occuring 
in the material in relation to a porous support, with which it is 
combined, and which support is not very sensitive to the action of heat, 
i.e., does not undergo significant structural changes. In the particular 
field of use of pitch binders for electrodes, it is useful to know the 
wetting power of the pitch because it provides an estimate of the utility 
of the pitch in the manufacture of electrodes. It should be noted at this 
point that by the term "pitches" is meant black or dark-brown solid 
cementitious materials which gradually liquify when heated and which are 
generally obtained as residua in the partial evaporation or fractional 
distillation of tar. Furthermore, by the term "wetting power" is meant the 
ability of the material, e.g., pitches, to wet or penetrate into the pores 
of the support upon which it is being liquified. More specifically, it is 
the ability of the material to be respectively adsorbed and absorbed on a 
porous support. In particular, it is useful to know the temperature, at 
which a pitch is completely absorbed in a coke support. In addition, it is 
useful to know how this absorption occurs, i.e., how the molten pitch 
penetrates the pores of the coke support. It is also appropriate to point 
out that by the term " coke" is generally meant a bituminous coal material 
from which the volatile constituents have been driven off by heat. The 
type of "coke" formed varies depending on temperature, position or the 
particles of coal from which it is formed, and although commonly 
artificially made can occur naturally and will generally be porous. 
SUMMARY OF THE INVENTION 
It is thus an object of the invention to provide a device for measuring the 
deformation of a material under the influence of heat. 
It is another object of the invention to provide a device for measuring the 
deformation of pitches under the influence of heat and to determine the 
wetting power thereof. 
It is still another object of the invention to provide a method for 
measuring the deformation of a material under the influence of heat, and 
more particularly, to measure the deformation of pitches to determine the 
wetting power thereof. 
It is yet still another object of the invention to provide a method of 
selecting pitches for use in manufacturing of electrodes according to the 
measured wetting power thereof. 
Upon further study of the specification and appended claims, further 
objects and advantages of this invention will become apparent to those 
skilled in the art. 
In accordance with the invention, a device is provided for measuring the 
deformation of a material under influence of heat. The device generally 
comprises a source of light, an at least partly transparent chamber for 
allowing light to travel therethrough equipped with a heating device which 
can be programmed to operate as a function of time, and having a porous 
support in the chamber designed to receive the material thereon, a 
photo-electric receiver, and an optical lens for enabling an image of the 
material to be formed on the photo-electric receiver. In the device of the 
invention, the source of light, the porous support, the photo-electric 
receiver and the optical lens are optically aligned with the porous 
support located between the light source, and the lens and receiver. 
In a further embodiment it is convenient to insert a diaphragm and/or an 
optical lens between the source of light and the chamber for creating a 
beam of parallel light rays from the light source. The porous support can 
rest on a base, which either rests on the bottom of the chamber or can be 
suspended from the top of the chamber. The material upon which 
measurements are performed is solid at ambient temperature. Advantageously 
the material is shaped, preferably like a cylinder, or as a 
parallelepiped. 
The nature of the light source employed depends on the particular type of 
photo-electric receiver used. More specifically, if the photo-electric 
receiver comprises a photomultiplier tube, provided with a vertical slit 
on which the image of the material 6, produced by the lens 7, is focused, 
it is necessary that the light source have constant intensity and that the 
light emitted have a wave-length compatible with the operational 
characteristics of the photomultiplier tube. In this case, it will 
therefore be possible to use a conventional light source, i.e., a filament 
lamp supplied with a stable voltage i.e., non-fluctuating voltage, or 
alternatively, the light source can comprise a laser source. These 
elements are generally conventional in nature and will not be elaborated 
on in greater detail. 
If the photo-electric receiver comprises an array of microphotodiodes 
arranged in the form of a vertical bar, the light source need not have a 
constant intensity nor need it be monochromatic because the 
microphotodiodes will then operate on the "all or nothing" principle, as 
will be clarified below. It is necessary, however, in this case that the 
intensity of light emitted by the source be sufficient for saturating the 
microphotodiodes. By the term "all or nothing" it is intended that each of 
the microphotodiodes in the array will have an output of a fixed value 
once a minimum intensity of light strikes it, and the output will not vary 
in accordance with increased or decreased (but not lower than the minimum 
intensity) intensity of light striking the microphotodiodes. The output 
will be zero when an opaque sample will intercept the light beam. 
As previously discussed, the chamber has to be at least partly transparent 
in a manner so as to allow transmission of the light beam originating from 
the source therethrough. The chamber may be completely transparent and 
comprise for example, a glass cylinder, the axis of which is at right 
angles to the light beam, and also at right angles to a plane defined by 
the top surface of the porous support in the chamber. The chamber may also 
alternatively be partly transparent and comprise for example, a hollow 
structure in the shape of a parallelepiped with the two walls parallel to 
the light beam being opaque, and the two walls at right angles to the 
light beam being transparent. The transparent walls of the chamber which 
are thus located spaced opposite each other, are preferably made of a 
material that is not deformable by heat. For instance, the walls may be 
made of glass, for example Pyrex grade glass. 
Alternatively, the light source can be situated inside or outside the 
chamber. If it is situated inside the chamber, the chamber need be only 
transparent on one side for the passage of the light beam to the 
photo-electric receiver.

DETAILED DISCUSSION OF THE INVENTION 
According to one embodiment of the invention as shown in FIG. 1, the light 
source 1, a porous support 4, a photo-electric receiver 5 and an optical 
lens 7 are both optically and linearly aligned. Alternatively these 
elements need not be linearly aligned, however, in this case the device 
will then require in addition, a reflective element, situated in the path 
of the light beam originating from the source 1, before or after its 
screening by the material 6 to ensure that the beam intercepted by the 
material 6 on the porous support and is directed to the photo-electric 
receiver 5. The reflective element can be a mirror or a total reflective 
prism, situated, for example, inside the chamber and will be conventional 
in nature. The device may further comprise an optical lens 8 inserted 
between the source of light 1 and the chamber 2. 
The porous support 4, will generally have a porosity of between 0.1 and 
0.9,--ratio of pore volume to total volume, preferably 0.2 to 0.7, and 
more preferably 0.3 to 0.5. Furthermore, the porous support will be, for 
example, a powder bed, contained in a boat, or a pellet of sintered 
material. The powder, contained in a boat, has, for example, a particle 
size distribution of between 10 and 1000 .mu.m, preferably 20 to 200 
.mu.m, and more preferably 40 to 70 .mu.m. The pellet of sintered material 
has, for example, a pore diameter of between 10 and 200 .mu.m, preferably 
20 to 150 .mu.m, and more preferably 40 to 90 .mu.m. 
In FIG. 4 the chamber 2 is shown with transparent walls 2' and 2" with the 
porous support supported suspended from the top of the chamber 2 by means 
of a suspended base 9. This base 9 can, as previously described, merely 
rest on the bottom of the chamber 2. 
In FIG. 5 the chamber 2 is shown with only one transparent wall 2'" and 
with a total reflection prism 10 ensuring the optically alignment of the 
source of light 1, the porous support 4, the photoelectric receiver 5 and 
the optical lens 7 which are not linearly aligned. Alternatively the 
device comprises an optical lens 8 providing from the source 1 a parallel 
light beam. 
The device according to the invention will operate in the following manner. 
The material 6 is placed on the porous support 4, in the chamber 2 which 
at that time is at a lower temperature than the temperature at which the 
material 6 begins to deform. The light source 1 is activated by supporting 
power thereto, and the optical lens 7 is adjusted so as to form an image 
of the material 6 on the photo-electric receiver 5. The position of the 
porous support is checked to ensure that the porous support 4 at least 
partially intercepts the light beam. In this instance, when the 
photo-electric receiver 5 comprises a bar of microphotodiodes, a fine 
adjustment is made on the device, with the aid of a counter, to determine 
the number of non-illustrated diodes. 
The chamber 2 is then heated according to a known equation, T=f(t): 
wherein, T represents the temperature and (t) the time. At a given 
temperature, depending on the material, the material 6 begins to deform 
and the amount of light, received by the photo-electric receiver 5, 
increases in proportion to the lowering of the height h of the material 6 
as it deforms on the porous support 4. The photo-electric receiver 5 then 
emits a voltage proportional to this lowering of the height, i.e., an 
increase in light is perceived. This voltage is converted by means of a 
recorder, into a graphical representation, i.e., a curve on a graph 
corresponding to h=(f(t),--for a predetermined heating law or, if the 
recorder is coupled to the temperature programmer of the chamber, to a 
curve corresponding to h=f(T). 
In a refinement of the device, the contour of the material 6 in the course 
of deformation can be traced at any moment in time. To accomplish this, 
the photo-electric receiver 5 is mounted so as to be transversely movable 
with respect to the light beam and is thus capable at any instant in time 
to scan the zone, on which the image of the material 6 is formed. The 
means for scanning is conventional as will be evident to one skilled in 
the art. 
The scanning movement has to be sufficiently rapid to enable an almost 
instantaneous imaging of the contours of the material 6 in the course of 
deformation at a given temperature. In this embodiment the measurements 
will supply additional useful information regarding the angle formed 
between the base of the material 6 and the porous support 4 during 
deformation, which is a measure of the mutual wettability or 
non-wettability, as well as the reduction in height (h) of the material as 
a function of temperature. Thus, a first recorder can be simultaneously 
used for tracing the changing contour of the sample, and a second recorder 
for tracing the height (h) of the material as a function of temperature. 
The device according to the invention makes it possible to carry out 
reliable and reproducible measurements, without requiring continuous 
control by an operator. 
Furthermore, the invention is applicable to measure the deformation of any 
material, which deforms under the influence of heat, such as, e.g., 
novolac resins such as phenol-formaldehyde resin, pitches and other 
thermoplastic materials sufficiently opaque to block the passage of light 
therethrough. The invention is also applicable to the determination of the 
wetting power of pitches which is a direct function of its deformation 
over time on a porous support such as coke. In this application, the 
porous support 4 can be, for example, a bed of coke powder contained in a 
boat, or a sintered glass pellet. According to the procedure described 
above, measurement of the deformation is interrupted when the pitch sample 
has been completely absorbed into the porous support 4 and thus the 
wetting power can be determined. 
Without further elaboration, it is believed that one skilled in the art 
can, using the preceding description, utilize the present invention to its 
fullest extent. The following preferred specifie embodiments are, 
therefore, to be construed as merely illustrative, and not limitative of 
the remainder of the disclosure in any way whatsoever. In the following 
examples, all temperatures are set forth uncorrected in degrees Celsius; 
unless otherwise indicated, all parts and percentages are by weight. 
EXAMPLE 1 
The porous support 4 used was a bed of coke powder, having a particle size 
distribution of 40-400 micron, with 88% of the particles having a size 
between 80 and 125 microns, and the deformable materials 6 used were two 
pitch pellets, having approximately the same physicochemical 
characteristics, but having different behavior in the manufacture of 
electrodes. With the pitch No. 2 it is necessary, when manufacturing an 
electrode, to heat the mixture of pitch and coke at a higher level than 
with pitch No. 1 to ensure a correct homogenization of the mixture. 
Of the samples, sample No. 2 has a poor behavior with respect to wetting 
power relative to sample No. 1. With the aid of the device according to 
the invention, the curves of FIG. 2 were obtained, showing the height of 
the pitch pellets as a function of temperature. Thus, it can be observed 
that the curve, representing pitch sample No. 2, shows a pattern of 
deformation and absorption on the coke indicating that certain of its 
components are absorbed with greater difficulty by the bed of coke powder. 
EXAMPLE 2 
The porous support 4 used was a sintered glass pellet, the pore diameter of 
which lies between 90 and 150 .mu.m, and the material 6 used was a pellet 
of phenol-formaldehyde resin of the novolac type, generally obtained by 
condensation of phenol and formaldehyde in an acid medium. This resin has 
a Durran softening point of 85.degree. C. 
FIG. 3 shows the curve, h=f(T), obtained with the aid of the device 
according to the invention. The first plateau corresponds to the 
transformation of the resin pellet into a drop, i.e., the melting. The 
temperature at the center of this plateau corresponds to the melting 
temperature. The following part of the curve shows the absorption of the 
sample into the porous support 4. 
The preceding examples can be repeated with similar success by substituting 
the generically or specifically described reactants and/or operating 
conditions of this invention for those used in the preceding examples. 
From the foregoing description, one skilled in the art can easily 
ascertain the essential characteristics of this invention, and without 
departing from the spirit and scope thereof, can make various changes and 
modifications of the invention to adapt it to various usages and 
conditions.