PRODUCTION • Platformer operating and mainte nance expenses axe lower, due to less severe operaungi-coti^^ And refiners could save on the cost of a new Platfbrmer, Belden indicated, if they install the Penex process, because the Platformer could be designed to op erate at lower severity.
Determining Resin Content New NBS method eliminates error caused by calcium car bonate filler in plastic lami nates JL HE National Bureau of Standards has developed a fast and accurate method for determining resin in glass fiber-polyester laminates ΛνηβΓβ calcium carbonate is a filler. S. D . Toner of the Bureau's plastics laboratory has dem onstrated that high, resio-decomposing temperatures used in t h e usual test cause calcium carbonate to decompose, producing errors in the results. The new method, developed for the Air Force, restores the decomposed calcium carbonate t o the residue so that resin content can be more precisely calcu lated. Normally, the resin content of a glass fiber-polyester laminate is determined by igniting the specimen at 565° dt27.5° C , until the resin is vaporized and driven off. The difference in weight between the original specimen and the ignition residue is equal to the resin content. In the Bureau's method the laminate specimen is ignited until no weight changes occur. The ignition residue is then treated with excess saturated am monium carbonate solution, which re acts with calcium oxide t o form calcium carbonate. Treated residue is then placed in a constant temperature oven at 80° C , to decompose and remove any unreacted ammonium carbonate. The ignition residue theon contains the same amount of calcium carbonate as the original specimen, and the resin content can be calculated by the differ ence. To test tbe method, t h e Bureau de termined the effect of ignition at high temperatures on three control groups of plastic-laminate specimens. Group A specimens contained resin and glass fiber only; groups Β an«d G contained resin, glass fiber, and calcium carbo nate. The specimens im group A con tained equal parts of resin and glass fiber, by weight. Those in groups Β and C contained four parts resin, three parts glass fiber, and one part filler, by 3606
C&EN
JULY
23,
1956
weight. AU specimens weighed 3 grams. The specimens were ignited at 5 0 5 * C , for one and a half hours» After values were corrected for volatile fiber finish on glass fibers, ignition loss values were 50.01%, 53.48%, and 53.83%, re spectively. Group Β residues were then treated with ammonium carbonate as were those in group A. Group A speci mens (containing no calcium carbo nate) showed little change in weight. Group Β showed a 3.4% increase. Group C was treated no further. When end weights of all three groups were compared to the original weights, the differences between resin contents as determined by test and known original contents were —0.05% for group A; 0.01% for group B; 3.75% for group C.
The Forgotten Effect Tennessee engineers design horizontal thermal diffusion column that minimizes density gradients JLF YOU can't solve it, eliminate it. With this philosophy, University of Tennessee chemical engineers hope to rid themselves of the "forgotten ef fects—a phenomenon that makes oper ation of conventional (vertical) thermal diffusion columns difficult to predict. The "forgotten effect" plagues en gineers. It always pops up when con centration changes take place to cause density gradients, because these density gradients have an effect on separation. Especially when solution density varies appreciably with concentration, the convective velocity distribution in the column becomes an extremely compli cated function of plate spacing (dis tance between the hot and cold walls.
When density gradients are present, they only cloud up time study engineers are trying to make of the effect of tem perature gradients «on «concentration changes. So S. 3î. Jury conceived a horizontal column that minimizes ^density gradients for separation of mixtures tough or impossible t o handle in thermogravitational columrms. Jury's column has other important advantages: • It circulates true working -fluid countercurrently by external pumps rather than by natural convection. • A permeable membrane, through which separation takes place, has !>een introduced to define dhestreams flowing*" countercurrently vitlain rJhe apparatus. • Zig-Zag Path, IThe column's flow channel, a zig-zag pasth, is machined in a resin of low theE-mal conductivity which is sandwiched fcetween the metal heat transfer surfaces. "With zig-zag flow, Jury geës a total flow of 75 feet in a small installations He says his coLiimm increases the efficiency of separation- Convective mixing takes place withrin tihe individual streams, allowing gresater heat transfer for the sanje teonpeiratiire differential present in conventional equipment. (Since theory prédicats that separation is an exponential function of the amount of heat transferred, it should be possible to achieve substantially greater separations.) With external puirmps, Jury gets better control of process variables. This should lead to greater- flexibility of operation and further economic optimization of the process. Armed with a $38C0 grant froro Du Pont, Jury has one o £ his graduate students, Edward Von Halle, on an experimental program likehy to turn up some very interesting results in the near future.
