Silicone Resins : Silicone resins contain ring structures and have an much higher cross link density than silicon elastomers.
What is Silicone Resins and Types
The preparation of silicone resins is as much an art as a science. The resins are prepared by hydrolysing and condensing (or polymerising) mixtures of bifunctional
or trifunctional alkyln chlorosilanes under carefully controlled conditions.
The properties of the resins can be varied by controlling the relative amounts of bifunctional and trifunctional units, the type of organic units attached to silicon, the polymer size or configuration, and
the addition of other organic resins.
It is usually necessary to cure the silicone resinnat a temperature somewhat higher than that at which it is likely to be used.
Copolymeric resins of desired properties can be obtained by condensing two polymers.
The silicon resins can be co-polymerized with phenolic polyester, epoxy cellulosic or other functional resins. The properties of these copolymeric resins depend upon the nature of the condensing polymers and the degree of condensation
The silicone resins can be broadly classified into six categories, although there is overlapping because some can be applied in more than one way.
Silicone Resins Types
(i) Coating resins
These resins have got distinctive properties of heat resistance, water repellency and resistance to most of the aqueous chemicals and corrosive gases.
The pure silicone (unmodified) films are useful on hot stocks, exhausts, electric motors and turbines, stoves, boilers, steam pipes, and other places
where conditions are too severe for the usual type of protective coatings.
Silicone coating resin formulations with aluminium flask or zinc dust and with or without the addition of organic resin can withstand temperatures of the order of 500°C and can be applied on high temperature processing equipments.
(ii) Laminating resins :
They possess high temperatures stability and good electrical properties and can be prepared in the form of sheets or tubes.
Resin laminated structures are widely used in electrical industry in the form of insulated board, coil former, rods, tubes and slotwedges in motors operating at high temperature.
They can be used in aircraft instruments such as radomes.
(iii) Release resins :
The release resins are widely applied to bread pans, waffle irons, cooky sheets, candy pans as well as to “Smoke sticks” used in smoking of metals.
(iv) Water repellent resins :
These resins applied as dilute solution coat the pores (but do not fill them) in masonry and concrete.
They do not allow water to enter the pores because of their water repellent character and as a result keep the
(v) Electrical resins :
They can be used with advantage where conditions are too severe for conventional insulators and also used in the treatment of capacitor insulations, transformer coils, motor windings and similar equipment demanding excellent chemical, mechanical and dielectric stability.
(vi) Foamed resins :
Silicone resins may be formed in situ or may be formed and then modulated to the desired shape by the use of blowing agents. They can be advantageously used for thermal and electrical insulation, firewall structures, buoyancy applications and high temperature vibration dampers.