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 as affected by egg weight, egg specific gravity, hens' age, hot washing, and hot washing followed by cooling. The mean measured values of linear thermal expansion coefficient in latitudinal and meridional directions were 4.4 x 10^-6°C^-1 and 4.2 x 10^-6C^-1, respectively. For 4 out of 24 treatments, differences in the coefficient of linear thermal expansion were statistically significant (p < 0.05) for the two different hens' age (34 vs. 51 weeks). The mean measured modulus of elasticity in the latitudinal direction was 19 GPa. Differences in modulus of elasticity were not statistically significant for different hen's ages (p > 0.05), but were significant for different egg weights and specific gravities (p < 0.05). The mean shear modulus in the latitudinal 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, egg specific gravity, thermal processing, and age of hens were not statistically significant (p > 0.05). The mean measured modulus of elasticity and shear modulus values in the meridional direction were 194 and 17 GPa, respectively. Variations due to egg weight, egg specific gravity, thermal processing, and age of hens were not statistically significant (p > 0.05).