FILM FORMATION IN COATINGS PROVIDED BY : EMAD BEHDAD
THE MOST IMPOTRANT STEP IN ANY COATING PROCESS THIS IS THE CONVERSION OF THE COATING FROM LIQUID TO SOLID FILM FORMATION BEHAVIOUR AND POLYMER GLASS TRANSITION TEMP PLAY A SIGNIFICANT CHANGE IN THE PROPERTIES OF A POLYMER
THERMOPLASTIC COATINGS What are the thermoplastics?• Commonly referred to as “plastics”.• Melt on heating and re-solidify on cooling.• Common plastics are polyethylene, polypropylene, nylon, PVC etc.• Used mostly for moulding into articles such as bottles, caps and components or by extrusion into packaging, carrier bags, pipes and fibers etc.
Polymers Cross-Linking Polymers Natural rubber isBonds formed too soft and between chemicallypolymer chains reactive to make make the a usefulpolymer stiffer. material.By vulcanizing the rubber Rubber is(cross-linking usually cross- the polymer linked withchains) useful sulfur.materials are made.
Thermal Behavior of PolymersGlass Transition Temperature (Tg)At low temperatures, all amorphous polymers are stiff and glassy, sometimescalled as the Vitreous State, especially for inorganic polymers.• On Warming, polymers soften in a characteristic temperature range knownas theglass-rubber transition region.• The glass transition temperature (Tg), is the temperature at which theamorphousphase of the polymer is converted between rubbery and glassy states.• Tg constitutes the most important mechanical property for all polymers. Infact,
Glass transition The temperature above which the glass becomes soft and viscous enough to work is related to the glass transition temperature, Tg. Below the glass transition temperature, the material is relatively hard and stiff; above it, it becomes more viscous. This shows up in the volume/temperature curve.