PP: Polypropylene or polymerized propylene is a very light, strong,flexible plastic. Used commonly for coatings, plastic pipe, fibers for clothing fabrics and packaging materials.
METAL: Most metal closures are made from tin plate and steel, but aluminum is used for those products which require anticorrosive closures with superior safeguarding properties. Metal closures can be used on both glass and plastic bottles.
LLDPE: Linear low-density polyethylene has higher tensile strengthand higher impact and puncture resistance than does LDPE. It is very flexible andelongates under stress. It can be used to make thinner films, with better environmental stress cracking resistance. It has good resistance to chemicals. However, it is not as easy to process as LDPE and has a lower gloss. Most commonly used for plastic bags, stretch wrap, pouches and covers or lids.
The plastic surrounding the opening of a bottle shaped to accommodate a specific closure. It's the portion of the neck that carries the threads or lugs to which the closure is applied and includes the sealing surface and sealing bead. Most common neck finishes include: continuous thread necks for twist-on caps and tamper evident necks for snap-on caps.