Soda Lime glasses

Question 1

What characterizes soda lime glasses?

Answer 1

~ additions of CaO to Na2O-SiO2 glass

Question 2

What effects does adding CaO to Na2O-SiO2 have?

Answer 2

~ increased viscosity and chemical durability

Question 3

What happens chemically in soda lime glasses?

Answer 3

~ Ca2+ is more polarizing to O2- (more covalent) and charge compensates 2 NBO’s

~ the Ca2+~O2- bond is harder to shear than the Na+~O2- bond

~ electrical conductivity decreases as Ca2+ is LESS MOBILE and blocks migration of Na+

Question 4

What are the effects of Al2O3 additions to soda lime glass?

Answer 4

~ increase durability
~ reduce NBO’s (increase index of refraction) by reverting the role of Na+ to CHARGE COMPENSATOR for AlO4- tetrahedra