Hiding power of pigmented (mostly white) plastic films. It is beneficial for packing materials sensitive to light (visible or ultraviolet).
OPP - Oriented PP (polypropylene) Film
A stiff, high clarity film, but not heat sealable. Usually combined with other films, (such as LDPE) for heat sealability. Can be coated with PVDC (polyvinylidene chloride), or metallised for much improved barrier properties.
OPS Shrink Film - Oriented Polystyrene Film
Very common alternative to PVC shrink films in Asia and Europe, but not readily available in the USA. Slightly higher priced than PVC films but more recyclable and has a greater shrink percentage.
OTR - Oxygen Transmission Rate
OTR of plastic materials varies considerably with humidity; therefore it needs to be specified. Standard conditions of testing are 0, 60 or 100% relative humidity. Units are cc./100 square inches/24 hours, (or cc/square meter/24 Hrs.) (cc = cubic centimetres)