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sediment figures from the two methods is usually between 1 to 1, and 3 to 1. Figure 2 also indicates that the tn-o methods do not rate oils in the same order.
Practical Applications of Hot Filtration IIethod The hot filtration method determines the content uf material capable of settling when fuel oil is stored. It does not. of course, indicate the rate of settling and it in\-olre: a sornewhat higher temperature than those normally existing in storage tanks. It has been developed primarily as a practical means of obviating the fundamental deficiencies of the benzene extraction method, and has already been put into routine operation for this purpose. The authors believe that it possesses a much wider field of usefulness and are using it in their investigations of the problem of heater fouling. It is planned to report the results of this study in another paper.
Acknowledgment Acknowledgment is due to E. W. Dean of the Standard Inspection Laboratory, Standard Oil Development Company, for constructive criticism of the method and for assistance with the manuscript.
Literature Cited (1) Batchelder, d. H., Refiner, Natural Gesoline J f f y . , 15, 185-98 (1936). ( 2 ) Federal Standard Stock Catalog, Section I V (part 5) Specification UV-L-79la, Method 300.2, pp. 84-5 (October 2, 1934). “Tentative Method of Test for Sediment in Fuel Oil by Extraotion,” 8 . 9. T. M. Designation D473-38T. (3) Voskuil, J., and Robu. I., J. Inst. Petroleum. Tech., 24, 174, 181906 (1938). RECEIVEDAugust 11. 1938.
Plastometrv of Synthetic Resins R . HOUWIKK
%NDPH.
N. HEINZE
’ I .V. Philips’ Gloeilampenfabrieken, Eiiidhoten. IIollaud
When testing the value of resins, especially of hardening synthetic resins, the two properties to be given most consideration are the hardness (weakening point) and the hardening velocity. New apparatus to measure these properties, particularly the Schopper-Houwinli plastometer, is described. Experimental results are discussed with their technical and scientific applications.
W
M
/
K
H E S using resins for molding purposes, and also in
many cases in varnishes and lacquers, the purely chemical testing methods ( 5 ) are of little use. The chief points to be investigated are their weakening point, theii chemical reactivity, and the properties of the molded pioduct. The weakening point is important, because generally the resins have to be melted in order to mix them with fillers and other substances. Mass production is possible only when a constant weakening point can be guaranteed. The weakening point for a certain resin is dependent on its degree of polymerization. The same holds for more physical properties: Hardness, viscosity, and yield value (if present) all increase on polymerizing. This means that, as a matter of principle, for control purposes one is free to determine any of these properties he likes to. It has been pro\-ed to be practical to measure n.hat may be called the plastometer hardness, this being (by definition) the height, h30 (12, 16, 17), of a resin specimen, originally 10 mm. in diameter and 5 mm. in height, after 30 minutes’ compression by a 5-kg. weight a t a fixed temperature between two parallel plates. Pure physical constants like viscoqity coefficient and yield value can be derived from this conventional compression procedure. There are many reasons for preferring this hardness to such other constants as the weakening point according to Kramer-Sarnow, the ring and ball ( 2 ) melting point, and the penetration ( I ) . I n many cases the resins have such a high weakening point that the Kramer-
FIGL-IW1. ~ ( , € ~ o P ~ E ~ - H PL.ts,rumTER (~~-~~-Is~ P , P‘.
G. M.
Plane-parallel plates Compressing weight Dial for leading off height of specimen
Sarnow and the ring and ball methods cannot be applied a t all as the resin does not flow under the conditions present in these
ANALI-TICAL EDITIOS
DECEMBER 15, 1938
h81
The plastonieter is fastened t o the oven by niean> of the metal strip, T . The lower part of the instrument is conducted through the roof and the footplate, P , is adjusted on the bottom. Plate PI contains a thermometer, Th, in order to be sure that the compression plates keep the right temperature. Experience has shown that this is essential, for in an air-heated oven there are often small differences in temperature. As the deformation process of a flowing resin is extremely sensitive t o temperature (the viscosity coefficient becomes ten times smaller per 1U" C . increase in temperature, 7 , p. 135), no reliable results can be obtained if this precaution is neglected. - ~ D J U S T I N GTHE APPARATUS. The weight, G (5 kg.), is mounted and with the aid of knob K plates P and P' are adjusted planeparallel t o each other. By means of the screws, s, care is taken that the footplate, F , "bears" on the bottom of the oven. CARRYISG OUT A MEASUREMEST.Two pieces of filter paper are laid between P and P' and the dial, 151, is adjusted at zero. Pis levered by means of K and now the resin cylinder-the height of which has been made exactly 5 mm. on a piece of sandpzper-is put between the filter papers. P is lowered until the dial indicates 5 mm. Then the time, to, is noted and K is quickly unscrewed so far that, if necessary, P and P' can touch each other. Now one can follow on the dial the change of height of the cylinder per unit, of time. When determining the hardness, h30, the success of the method depends wholly on the right preparation of the resin cylinder. For this purpose the specimen, H , is made as shown in Figure 3. One gram of the pulverized resin is put into A , after its wall has been covered n.ith a piece of thin parchment paper in order t o avoid sticking. The weight, B , is put on and the whole is heated in an oven at a temperature (sinter temperature, usually between 60" and 80" C.; it must not be taken too high, as the danger of polymerization will then arise), such that the powder sinters and a homogeneous cylinder is obtained; this can be pushed out of .4.
spparatus. RIoreorer, hardening resins must not be heated close to their melting point, as polymerization will go on The penetration method leads to erroneous results because of the gas bubbles which cannot be avoided when pouring out hardening resins. K i t h bitumens these bubbles can be driven out by heating for some hours, but this procedure is not permissible with a hardening resin. Still another reason makes the use of a plastometer extremely attractive. One can preheat the resin specimens a t a certain temperature during increasing periods. After each period the hardness can be determined, and the increase of hardness per unit of time is a measure of the hardening velocity of the resin (for the determination of the reaction velocity along more scientific lines, see 3, 4 , 8, 9, I S , 15). Working along more scientific lines (see Figure 10) one can calculate the viscosity after each period of preheating and in this way one can obtain a supposing that
d?
a will
dtl
curve.
As there are reasons for
be some function of the reaction
velocity constant K :
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-
c_-
-_ -. -~
FIGURE3. APPARATUS FOR hIAKING RESIXCYLINDERS ASD FOR POLYMERIZINGTHEM BELOW ABOUT80" C .
Schopper-Houwink Plastometer
Khen only a hardness determination is required, this cylinder can be used for that purpose. If, however, one wishes to determine the hardening velocity of the resin, a polymerization of the resin must be carried through. This can be done in two different ways.
The plastometer described here is based on the same principles as the well-linon-n Williams plastometer (7, 10, I?') but it has been modified to produce a n extremely simple and practical apparatus (available through Louis Schopper, Bayrische Strasse, Leipzig). Its chief characteristics are that those parts which must be handled during operation are outside of the heating oven. Figure 1 shows the apparatus and Figure 2 gives a picture of the instrument in use, mounted in the oven.
Before pushing the cylinder out of A , the apparatus of Figure 3 is put in a heated oil bath, the level of which is just' below D . This method can be used only when the reaction temperature is so low that no gas bubbles (foaming) are formed in the resin. When investigating a phenol- or cresol-formaldehyde resin of the resol type at a reaction temperature below about 80" C., for example, the conditions for this process are fulfilled. When reaction temperatures higher than about 80" C. are t o be used-for instance, when investigating a phenol-formaldehyde resin of the novolac type t o which hexamethylenetetramine has been a d d e d s o much gas will be produced that the resin cylinder
4 =f(K) dt
this may open in the future a way to determine K .
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683
gets spoiled. Then one can let the reaction take place first and afterward make the testing cylinder. For this purpose one gram of the resin is brought into tube R and this tube is fastened into holder H (Figure 4). A small hole, L, remains open, through which the gases to be produced can escape. H is then put into a bath (Figure 5 ) containing a boiling liquid (in the authors' case, butanol, chosen because it is not dangerous or poisonous and does not thicken on prolonged heating. B. p. is 117.5" C.), so that the polymerization is carried out at aconstant temperature. In the thermostat there is room for six holders, H . The gas developed makes the resin, which is first melted in the tube. start foamine and ' spreading all over the surface of 7s N the tube, so that an ideal way of heat transfer is guaranteed. This is essential as, because of the short polymerization time (usually between 2 and 10 minutes), the resin can be equally and thoroughly heated only in the form of a thinlayer. After polymerization the resin is scratched from tube R and the re.in test cylinder i. made according to the method shown in Figure 3.
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Figure 8 s h o w the influence of adding various proportions of hexamethylenetetramine, and proves that it is of no use to add more than about 14 per cent in this particular case. Figure 9 gives a comparison of the reaction velocities of three commercial types of resins, all of the noiolac type (16 per cent hexamethylenetetramine added). il special correction has been made here to eliminate the differences in hio a t the beginning. In order to do this the curves have been transported horizontally until they intersect the ordinate a t point h30 = 1.0 mm. By means of this artifice the resins are brought (at least on paper) into a comparable state of polymerisation, characterized by h30 = 1.0 mm. Kow the slope of the curves measures the velocity by which polymerization piocceds, starting from this fixed state. SCIEXTIFIC METHOD.The scientific method makes use of our knowledge (6)that the property which was expressed above by '.hardness" is dependent on two physical constants, the viscosity coefficient, 7, and the yield value, f. Of these two constants the yield value, in the case of resins in a state of polymerization as investigated here, is often zero or a t least doubtful [G, p. 3.57 (English ed.), p. 350 (German ed.)]. Under these circumstances it is possible to derive 7 from the dh
;zi ( h is sample height, t = time) observations on the plastometer.
Scott (14) and :Peek (11) have shown 'that under
It is possible to vary the reaction temperature at will by taking another boiling liquid in the thermostat. Experiments have shown, however, FIGURE 4. APPARATVS FOR POLYXERIZING RESINSAT TEMPERATURES ABOVE that the temperaABOUTSO" C. ture of 117.5" C. is sufficient for a classification of resins with regard to their molding properties. With higher temperatures the reaction time becomes still smaller, leading to relatively greater errors. Interpretation of Plastometer Results There are two ways of interpreting plastometer results. PRACTICAL METHOD. The merely practical method makes use of h3,,, the height of the cylinder, measured after 30 minutes' compression, a value which can be taken from Figure 6, being for these two different resins 3.1 and 0.6 mm., respectively. The reaction velocities of two resins can be compared according to this practical method by determining the increase of h30 on heating. Figure 7 shows the result for two resins, of which I is the softer, being more reactive, however. Some practical applications of this method are given later. B
FIGURE 5. THERMOSTAT FOR CARRYING OUT POLYMERIZATION ABOVE 80" C.
DECEMBER 15, 1938
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683
(acid cori~lensationwith 16 per cent hexametliylenetetramine added nitern-ard) leads to the qiiickest curing resin. Paracrew1 gives a c-ery low quality and phenol is intermediate with regard to its curing properties.
Literature Cited P”a
1 6 . V
lo4.
(1) Am. SOC. Testing Materials, D5-25, ( 2 ) d m . Soc. Testing Materials, D36-2G. (3) British Plastics >-‘earbook, p . 6 2 , 1936. (4) Dostal. IT., and N a r k , H., Trans. Faraday Soc., 32,54 (1036). (5) Fischer, E. J.. “Lahoratoriumsbuch fiir die organischen plastischeu Iiunstmasscn,” Halle ‘Salle, 1935.
