Engineering Chemistry S Datta

472 ENGINEERING CHEMISTRY
• It should be inert.
• It should be non-toxic.
Characteristics of an ideal paint
• It should be chemically inert.
• It should be weather resistant.
• It should be non-toxic.
• It should have a suitable consistency which is generally determined by PVC.
Special types of paints
(i) Fire resistant paints
(ii) Chemical resistant paints
(iii) Luminous paints.
(iv) Marine paints.
(v) Emulsion paints or latex paints.
(vi) Metal paints.
Importance of emulsion paints (Latex paints)
(i) It can be employed on both interior and exterior surfaces.
(ii) Application of emulsion paint over a surface is an easy task.
(iii) It does not have any disagreeable product. And above all,
(iv) It is non-inflammable.
PVC (Pigment Volume Concentration)
PVC is defined as :
PVC =
Volume of pigment in paint
Volume of pigment in the paint + volume of non-volatile vehicle in the paint
The concept of PVC is very much important in case of paints as PVC controls—gloss,
rheological properties, washabilities and durability of a paint.
The concept of PVC is extremely useful to a paint formulator for determination of different
pigment or vehicle combination i.e., a range of PVC shown in the table below:
Table 21.1: Range of PVC in a given paint
Name
%PVC
(i) Flat paints 50–75
(ii) Semi gloss paints 35-45
(iii) Gloss paints 25-35
(iv) Exterior house paints 28-36
(v) Metal primers 25-40
(vi) Wood primers 35-40