THERMAL AND MECHANICAL-PROPERTIES OF EGGSHELL UNDER DIFFERENT TREATMENTS

Modulus of elasticity, shear modulus, Poisson's ratio, and coefficient of linear thermal expansion of eggshell were measured for eggshells a s affected by egg weight, egg specific gravity, hens' age, hot washing , and hot washing followed by cooling. The mean measured values of lin ear thermal expansion coefficient in latitudinal and meridional direct ions were 4.4 x 10(-6)degrees C-1 and 4.2 x 10(-6)degrees C-1, respect ively. For 4 out of 24 treatments, differences in the coefficient of l inear thermal expansion were statistically significant(p < 0.05) for t he two different hens' age (34 vs. 51 weeks). The mean measured modulu s of elasticity in the latitudinal direction was 19 GPa. Differences i n modulus of elasticity were not statistically significant for differe nt hen's ages (p > 0.05), but were significant for different egg weigh ts and specific gravities (p < 0.05). The mean shear modulus in the la titudinal direction was 7.2 GPa and the Poisson's ratio values ranged from 0.3 to 0.4. Differences in these values related to egg weight, eg g specific gravity, thermal processing, and age of hens were not stati stically significant (p > 0.05). The mean measured modulus of elastici ty and shear modulus values in the meridional direction were 194 and 1 7 GPa, respectively. Variations due to egg weight, egg specific gravit y, thermal processing, and age of hens were not statistically signific ant (p > 0.05).