Question

1) There are two reaction mechanism for polymerization __________ and__________.

2) Stress relaxation in polymer is ________________.

3) Define HIP in ceramics processing and the advantage of the technique:_____________________________________________.

4) Common soda-lime-silica glass is made by melting together Na2CO3, CaCO3 and SiO2. Carbon dioxide will release from the process. For 1000 kg of glass with the composition of 15 wt% Na2O, 10 wt% CaO and 75% wt% SiO2, the amount Na2CO3 needed in kg is _____________ and the wt% of CaCO3 in the raw material is _____________.

Answer 1

1) There are two reaction mechanisms for polymerization, referred to as chain-growth and step-growth polymerization. In chain-growth polymerization (also called addition polymerization) reaction occurs by successive addition of monomer molecules to the reactive end (e.g. a radical end) of a growing polymer chain. Step-growth polymerization involves the reaction between the functional groups (HO-, HOOC- , etc.) of any two molecules (either monomers or polymers).

2) Stress relaxation in polymer is the process how polymers relieve stress under constant strain. Because they are viscoelastic, polymers behave in a nonlinear, non-Hookean fashion. This nonlinearity is described by both stress relaxation and a phenomenon known as creep, which describes how polymers strain under constant stress.

3) Hot isostatic pressing (HIP) is a manufacturing process, used to reduce the porosity of metals and increase the density of many ceramic materials. This improves the material's mechanical properties and workability.

4)Total weight of the glass = 1000 kg

Then weight of Na₂O = 15 wt % = 150 kg = 150000 g

weight of CaO = 10 wt % = 100 kg = 100000 g

wt. Na₂O = (wt Na₂CO₃)/[(mol. wt. Na₂CO₃)/( mol. wt. N₂O)]

or 150000 g = (wt Na₂CO₃)/[106 g/mol/62 g/mol] = (wt Na₂CO₃)/ 1.71

or Wt of Na₂CO₃ = 150000 g X 1.71 = 256500 g = 256.5 kg

wt. CaO = (wt CaCO₃)/[(mol. wt. CaCO₃)/( mol. wt. CaO)]

or, 100000 g = (wt CaCO₃)/[(100 g/mol)/( 56 g/mol)] = (wt CaCO₃)/1.79

or, wt CaCO₃ = 100000 g X 1.79 = 179000 g = 179 kg