The liner is made of a vinyl coating applied to high density polyethylene coated paper and then it is laminated to pulpboard. Pulp/Vinyl Lined Caps: Perfect for general use. Available in Thermoset and Phenolic caps. The color green easily identifies the Teflon® liner system. Uses include: Analytical lab samples, high purity chemicals, strong acids, solvents, environmental samples, pharmaceuticals, and diagnostic reagents. F217 has a low density foam core between two solid layers of LDPE. Choosing the Best Cap Liner Materialsį217 & Teflon® Lined Caps with Foam backed Teflon® PTFE liners resist attack from virtually all chemicals at room temperature and provides resilience for a tight seal with a low moisture transmission rate. A metal closure is manufactured from either steel (coated with anti-corrosive coating of either chromeplate or tinplate) or aluminum. Metal Closures offer the widest range of temperature tolerances and are very resistant to fracture from impact. The melting point for polyethylene is 115–135 ☌ and it is best for option freezing temperatures. Polypropylene can withstand high temperatures (it's melting point is 130☌), but is less suitable for freezing temperatures where it can become brittle. Polypropylene is autoclavable and polyethylene is not. Polypropylene caps are known for good impact strength, cost effectiveness, and pliability. Thermoplastics can be remelted after initially formed. Thermoplastic closures (Polypropylene, Polyethylene, etc.)
They're very tough when used in the correct temperature range. However, due to their non-chemically reactive nature, when exposed to corrosive or harmful chemicals over time, phenolic caps will not give out the way other polymers might. At 220☌ (428☏) or above, Phenolic caps will start to decompose.
Phenolic is short for Phenol Formaldehyde Resin (PF). Because thermoset closures are rigid, they provide the most consistent adherence to close dimensional tolerances. They provide the widest range of chemical compatibility and they exhibit the most tolerance to temperature of all plastic closures. Thermoset closures cannot be remelted after they are formed. Thermoset closures (urea, phenolic, melamine, etc.) There are two basic types of plastic closures used for scientific applications: Thermoset (Bakelite) and thermoplastic (polypropylene).
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