September 1, 1915. 



THE INDIA RUBBER WORLD 



651 



and cooled. The cylinders also arc cooled until thej can be 

 handled. The rubber is put back into the mixer and worked 

 up again; the paraffin is then added bj rubbing it on !<■ the 

 rear of the cylinder with the hand. When a perfect mixturi is 



obtained it is again removed and allowed I I Eoi a half hour. 



["he same process is followed in adding tin- sulphur ami the 

 magnesia. 



"For mixture B tin' process i- thi sami i ccepl that tin- mat; 

 nesia and tlu' magnesia carbonati ari added at tin- same time. 

 The magnesia must always he added before the sulphur, for it 

 is very light and -low in mixing and the mixture bed 

 and very hot. Were the 

 Sulphur added while the 

 mixture is hot it would he 



I — ible for vulcanization 

 to commence in the mix- 

 ing machine; the mixture 

 must therefore lie allowed 

 to cool for at least an 

 hour and a half before the 

 sulphur is added. 



"To spread the mass on 



the fabric it is of course 



necessarj to dilute it. 

 1 ithei benzol i >r benzene 

 may be used as a soh cut. 

 but the latter is preferable. 

 The solution of benzene 

 must be perfectly free of 

 water ami all the ingredi- 

 ents must 1"' handled in 

 perfectly clean \ es >els 

 Idle boiling point of the 

 i ne must not lie 1< iwer 

 than 70° Centigrade ( 174 

 Fahrenheit) nor higher 

 than 100 Centigrade (212 

 Fahrenheit I. The pai I i 

 the benzene thai doi - nol 

 1" iil al I < 



must not exceed 8 per 

 cent., for the table of the 

 spreading machine would 

 have to be to i highlj 

 hi ated and, even then, the 

 solvent might not be com- 

 pletely evaporated. This 

 evaporation is very im- 

 portant, for the slightest 

 1 u of benzene w< mid turn 

 to gas during the vulcani- 

 zation and make it impos- 

 sible to obtain a gas-proof 

 fabric. But the evapora- 

 tion of the solvent musl 

 not be too rapid, for bubbles would possibly form and the fin 

 material would not have sufficient strength to withstand the high 

 gas pressure to which ii i- necessarily subjected when in 

 The fabric must pass slowly over the heati d table of the spreader 

 to allow ..mple time for the complete evapoi ition ol the solvent. 

 "The rubber mixture should always be dissolved -lowly and 

 -hould not he allowed to stand, lest the suphur should crystallize. 

 The mixture is rolled into a thin -beet, which is shaken in the 

 solvent, a perfect pulp being thus obtained. It is advisabl 

 make two solutions of the same mixture — a 'long' or thin one 

 and a 'short' or thick solution. The first application of the 

 solution must penetrate the pores of the fabric as far as 

 sible. and for thi- purpose a thin solution is better than a thick 



on< I "i lining the fabric the thick solution is best. In prepar- 

 ing the mixture it must be borne in mind that rubber i- affi 

 bj the rolling it is subjected to; tile mo er is worked in 



the mixer the less it- elasticity and the greater it- adhi 

 qualities. Rubber i- also d bj solvents. Rub- 



1 al ha- been kneadei lo warm cylinders re- 



quires le-s benzene than ' 1 rubber. 



SPREADING. 

 "The spreading m iom well ventila 



i I he spreading machine must 

 ■ avy, firm foundation and driven i 



as to eliminate vibration 

 a- far - l< and to 



larity 

 in running. Spreading cyl- 

 ld bi pi rfectly 



th under the knife. 

 I he i nil i r coating must 

 • rtain hardness. 

 If it is too hard the fabric 

 is compressed and weak- 

 ened; on the other hand, 

 if it is too soft, the fabric 

 forces itself into the gum 

 and the layer is conse- 

 quently uneven in thick- 

 • 



"I he knife ■ if the spread- 

 ing machine must be per- 

 fectly sharp in order that 

 the layer of rubber may be 

 well spread. If the rubber 

 catches on the back of the 

 and forms clots, they 

 should ed with a 



wet knife. I his i- very 

 important. The table must 

 be sufficiently heated to 

 vaporize practically all the 

 solvent by the time the 

 fabric reaches the end of 

 able. Before spread- 

 ing is begun the fabric 

 must he perfectly dry. 

 Coatinj with the 



spreading of the thin 

 tion. The fabric is pre- 

 viously wo-.nd on a large 

 drum, from which it passes 

 mi to a drum cylinder on 

 the spreading knife 

 ding knife 

 is adjustable, so that one 

 'i obtain the desired 

 thickness of coating. A 

 weighing 90 grams to | , meter (3.086 ounces to 



0.764 sq. feet) will take from 8 to 10 grams of gum per 

 yard. The layers of rubber coating are applied so as to 

 follow each other in opposite directions. Longitudinal as well 

 lisxerse folds or wrinkles should be guarded against. The 

 spreader moves at . ■ ■ about 17 feet per minute. It is 



therefon easj to f How the work and correct mistakes. Bias 

 fabrics which have a tendency- to contract and shrink should be 

 passed through a smoothing calender before spreading is under- 

 taken. Fabric should also first be dried for 24 hours in a special 

 room and sprinkled with paraffined talcum powder which can 

 be rubbed into the fabric by a brushing machine. 

 (To be Continued.) 



1 ' v Military Captive I'.ai.loon. 



