Influence of temperature on the adsorption of water vapor by collagen and leather

Abstract

The adsorption of water vapor by co ll agen, commercial hide powder, and severa l leathe rs was determined at various relative humidities ranging from about 0 to 96 percent, at 28°, 50°, and 70° C. Determi nations were also made on chestnut a nd quebracho tann ins at 28° C at vari o us re lative humi dities. The results indicate that at 50-percent relative humidity the vari ation of moisture conte nt for 1 degree change in temperat ure is e quivale nt to t hat for 1 perce nt cha nge in relative hum id ity. A specia ll y pu rifi ed co llagen h as higher affinity for wate r tha n does hi de powder, showing that t he pr evio us chemi cal treatment in fluences adsor ption. The res ults obtain ed from t he exp eriments 011 t he tan nin s a nd t he h ide powder show that tanning does not decrease water vapor adsorptio n at relative humiditie below 70 percent. F rom t he resu lts of t he adso rption measureme nts, heats of adsorption we re calcul ated by m eans of t he Cla usius-Clapey ron and Brunauer, Emmett, and Teller eq uations. The leathe rs sh ow hi g her heats of adsorp tion for low moist ure regains th an does co llage n, indi cati ng that they co ntain so me g roups t hat a re more highly act ive' towa rd wate r tha n t hose in coll agen. F ree e ne rgy and e nt ropy values for the adsorption at 50° C are given. The efi'ect of hi g h temperat ures o n moisture adsorption is studi ed by su bjecting specimens to elevated temperatures and t he n determ ining th e adsorption at 28° C. Methods are give n for estim ating m oist ure eo ntent for conditions t hat have not been st udied expe rimentall y. T he change of wate r adso rption wit ll tempe rat ure can be expressed by a simple relation involving th e log of the perce ntage of water adso rbed and t he inverse of the absolu te tempe ratu re.