164
Vol. 17, No. 2
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Rubber Latex Particles’,’ By E. P. Wightman and A. P. If. Triveili EASTMAN KODARCo.. R ~ C B S S T N. E ~Y. .
impact causing the particle to spin. If this rotational motion is strong enough, the particle will elongate until the surface tension is not sufficiently strong to draw it back into spherical shape or even to hold i t together. Thus, new particles Rill be formed. A particle moving rapidly for any reason will tend to take the pear shape. Here again i t is easy to split offa section of the particle. Two particles will join each other if they come together with sufficient momentum. The larger the particle the easier it is to deform or break up. According to Hauser’s illustrations (Figures 1and 2) of fresh latex and latex from new branches, leaf stems, and leaves, the HEYEA BRJASILIENSIS particles are on the average smaller and more nearly spheriedl. The larger particles, which are most common in normal tappings (Figures 4, 5, and 6) and in old trees or after certain treatment of the latex (Figure 7), are more frequently deformed as would be expected. ,. 2. 3. 4. 5 6 7. FigureXgivesafewpicturesof the particlesmadefromevery r,,us-isr(b”gdi.mete~) ili-000imm- 1/25.000ofan inch. fourth consecutive motion picture. The rulings help to show size the degree of motion (in one plane) of the particles. Some are G8*. 15.6mOrt r*mrnon in “0m“aI +ap”he ale. F , p 1.2 mort e~rn-n m new branches, lacf -9h- aod l e a v e seen to move out of focus while others move in. This is due Fg. 7rnc,+ (ound on? io dd t r e e or a H v cartaintrulkment to the small depth of the focus of the objective necessary to oF the ktcx show the particles, and the dficulty of getting a sufficiently Hauser’s 1uustrarion Of some Later Partielea slide and covered with an ordinary micro cover glass, also well thin coating of the rubber latex. Although the writers may not go further into the study of cleaned, and well pressed down, on ex‘mination under 2500 magnification with transmitted light it was found that the rubber latex by means of motion pictures, they feel that i t is particles appeared to range in size from about 0.2 to about 41r a fruitful method of attack particularly for such processes as in diameter, averaging around 0.7 to 0.8 &. They were not the peptization or coagulation of the particles, and recommend solid, but liquid, as Hauser claims for several types of rubber. i t to those more intimately associated with such problems. They had strong Brownian motion and easily became de- Motion photography of the particles illuminated by intense formed from the normal spherical shape, owing to their light in a dark field (ultramicroscopy) might also show up bombardment by the molecules of liauid which cause their particles too small to he seen by transmitted light. A brief description of motion, to their-own im.. . . . the microscopical system . pacts, and to local surface used may be of interest. tension differences at the A Zciss microscope with I interface between particle Leitz 1/22 inch, N. h.1.32, and surrounding liquid. oil immersion objective, The pear shape, similar Zciss “Homal IV” or negato the Hevca latex partitive projection lens, and a cles, desctibed by IIauser, Zeiss a p p l a n a t i c coilappears to be quite frequent, but the particles do denser, N. A. 1.4, were used. The source of illunot remain in this shape. They may change more or mination was a G. E. less quickly to another “Tungsarc” lamp. Some of themotion pictures were shape, split off a new particle, or add on a made with a Gin6 Kodak Figure $-Rubber Latex Particles Photomlcrographed on Cine Kodak Film without lens, standing on smaller particle. a t x 200 Magnification. Present Magnification x 600 To explain the forma- The rulings in the reproduction make it possible to show the motion m ~ r eagily. a tripod separate from the e tion of an ellipsoidal partimicroscopical bench. Conaecutive frames here correspond to every fourth frame in the CinC film. cle and the sulittine This latter N ~ Sfound ” offof a section of particle6 is quite simple if we imagine a tangential ordinary 32-mm. motion prevent vibration. The necessary in order to picture camera was also used. In the former 1 Presented before the Division of Rubber Chemistry at the 68th Meetinsof the American Chemical Sociefy.Ithrca, N.Y.,Sepiember8to 13,1924. case t.he picture was taken on 16mm. Cine positive film and 8 Communication No. 215 from the Research Laboratoryof the Eiistman this was reversed chemically to give a positive. In the Kodak Compsny. latter case the 32-mm. negative film on which the picture Indin Rubbn J.,68, 7 (1924): Sfbidrowit=. Isid.. 68, 3 (7924). was taken was developed t.o a negative, and reduced onto a Obtained through the U.S. Rubber Company. The slide was first cleaned with eoneentrnied nitric acid and then rith 16-mm. positive film. 20 percent sodium hydroxide and finally waarhed with dintilied water. When Acknowledgment these pxecautions =re not taken the pmticler stick to the slide badly. Hatrhek. T m n e Farodoj Sor.. 11, 17 (1916): Darwin, Tranr. R o y The writers wish to thank A. van Rossem, Delft, Holland, SOC.London, 198, 301 (1902); 200, 251 (1903): 106, 161 (1906): 308. 1 for some helpful suggestions received in a private communi(1908): Pror. Roy. Soi. (London). =A8 188 (1900);Linp~unoff,A c o d . Si;.. S1. Pdariburgh, M m . . I? 1 (1905). , cation from him. HERE appeared recently an account of an interview with and some interesting remarlis by E. A. &userS on the subject of rubber latex particles. In the present note the writers wish to add afew observations to thisalreadyvaluable investigation. Hauser’s work, however, was apparently done on rubber particles in a fixed or static condition-i. e., attached to the micro slide-whcreas that desrribed herein, as will be seen, was a “motion picture” study of the particles. When a slightly diluted sample of latex‘ in 5 per cent ammonium hydroxide was placed on a very cleans microscopic
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