May 1, 1916.] 



THE INDIA RUBBER WORLD 



The Manufacture of Balloon Fabrics in Europe. 



^filial Correspondcnc 



nadc that eacli of the fabrics 

 coaled separately, one suffi- 



Ll.XED or -doubled" fabric is 

 which are brought together 

 ciently to be gas-proof, the other but lightly gummed. After 

 being prepared in this manner the fabrics are passed together 

 through a "doubler, " and vulcanized. 



.A buffing calender is used in lining balloon fabrics, this calen- 

 der being composed of two hardened steel cylinders. The 

 under cylinder is geared, while the upper one is free and 

 presses on the lower one. The pressure between the cylinders 

 is adjusted by weights and springs. It must be perfectly regu- 

 lated, as excessive pressure causes wrinkles to form in the fabric, 

 while insufficient pressure causes the cylinders to draw the fabrics 

 at varying speeds and the finished material has a tendency to 

 separate. 



The sheet of fabric coated with the thick gas-proof solution 

 must pass over the upper cylinder of the calender, while the sheet 

 coated with the thin solution passes over the lower one. In 

 Germany they prefer to line or double their balloon material 

 with diagonal warp fabrics. In France, on the contrary, straight- 

 thread fabrics are usually employed for this purpose ; in the 

 latter case, the warp as well as the weft threads of both plies 

 of fabric are parallel to each other. Great care must be exer- 

 cised in calendering straight-thread combinations. The threads 

 of both layers must be perfectly parallel and the tension on the 

 fabrics must be even, for should some threads be tighter than 

 others they will be subjected to a greater strain when in use 

 and their tensile strength will be impaired. They also will 

 warp and endanger the rubber connection between the layers 

 of fabric. The 

 total tensile 

 strength of a 

 doubled fabric is 

 never equal to 

 the sum of the 

 tensile strengths 

 of each layer ; 

 and diagonally- 

 lined fabrics are 

 not as strong as 

 fabrics lined par- 

 allel, because of 

 the fact that it is 

 almost impossible 

 to obtain even 

 tension through- 

 out. By tearing 

 a sample of diag- 

 onally lined fab- 

 ric it is quite evi- 

 dent how irregu- 

 lar this fabric 

 really is. But 

 diagonal or cross- 

 thread linings 

 have their advantages. For instance, these will not allow a rent 

 to spread so easily as in the case of parallel-thread f;ibrii>. and 

 are more perfectly gas-proof. 



VULC.\.\IZ.\TIOX. 



Heat-cured balloon fabrics are vulcanized in steam or in a 

 steam-jacketed vulcanizer in hot air under pressure. The latter 

 method is employed when colors used are sensitive to the effects 

 of steam, also for silk and flax fabrics which cannot stand 

 steam. When ready for steam vulcanization the balloon fabric is 

 wound on a hollow iron drum, about 5 vards in circumference, and 



A L.ATE Type of Zeppelin i 



open at both ends. This drum is first covered with several layers 

 of thick, ruliber-coated fabric, which are vulcanized at the same 

 time with the balloon fabric. The object of these extra layers is 

 to protect the balloon fabric from any steam that might find its 

 way through the rivet holes of the drum and also prevent 

 over-vulcanization of the lower layers of balloon fabric. Pre- 

 vious to wrapping, the rubberized surfaces are thoroughly 

 powdered with talc. In fabric colored with chrome yellow it 

 is essential that it l)e w-ound so that yellow comes upon yellow, 

 even if the material only has one intermediary coat of rub- 

 ber. Wrapped in this manner, fabrics colored with lead 

 chromate give better colors than if the yellow surface had 

 coiTie in contact with the layer of rublier while being vul- 

 canized. 



Should the color of the rubber-coated inner surface be damaged, 

 it is of but little consequence, but for the outer side, which ul- 

 timately will be the outside of the balloon, it is essential that 

 the material be perfectly uniform and yellow in color. Several 

 layers of fabric rubberized on one side, or several plies of ma- 

 terial rubberized on both sides, are wound with the balloon fabric 

 so that the rubberized surfaces of the latter are wound against 

 rubberized surfaces. Talc prevents sticking. Several layers of 

 material, rubberized on one side only, are also wound over the 

 whole, to prevent steam reaching the balloon fabric. When dry air 

 vulcanization is used the rubberized coverings are not necessary 

 and a few layers of ordinary material afford suflScient protection, 

 except in cases where chrome yellow is used for coloring, 

 when it is preferable to retain the gummed wrappings, for the 

 least humidity that might penetrate to the fabric during vulcan- 

 ization would de- 

 compose the lead 

 chromate. 



Once wound 

 on the hollow- 

 iron drum, the 

 whole is run into 

 the vulcanizer on 

 a truck and the 

 door is closed. 

 The length of 

 time necessary 

 for \ ulcanization 

 varies with the 

 thickness of the 

 materials and the 

 thickness of the 

 rubber coating, 

 as well as with 

 the length of the 

 liiece, I. e., the 

 number of plies 

 wound around 

 the drum. Dry 

 steam vulcaniza- 



Flight (Rigid). stean 



tion may require 

 from 50 to 90 minutes and the temperature should never be allowed 

 to exceed 133 degrees C. (342 degrees F.). When vulcaniza- 

 tion is finished the drum is run out and allowed to stand un- 

 til the fabric is completely cool. Upon being removed from 

 the vulcanizing drum the fabric should be thoroughly powdered 

 w^ith talc and then carefully brushed. Fine paraffined talc 

 should be used. Dry vulcanization in a jacketed heater is difficult, 

 as the heat often fails to penetrate all the layers of fabric. If vul- 



article has just come to hand, having 



