Preheating -

Preheat definition, to heat before using or before subjecting to some further process:

a process of giving heat to an object, essential for the actual process which is to be takes place just after.

Stretching -

Biaxially oriented polypropylene (BOPP) film is film stretched in both machine and transverse directions, producing molecular chain orientation in two directions.

Annealing -

In metallurgy and materials science, annealing is a heat treatment that alters the physical and sometimes chemical properties of a material to increase its ductility and reduce its hardness, making it more workable.
Annealing is used to reduce hardness, increase ductility and help eliminate internal stresses.

Lubrication -

Lubrication is the process or technique of using a lubricant to reduce friction and wear and tear in a contact between two surfaces. The study of lubrication is a discipline in the field of tribology. Lubricants can be solids, solid/liquid dispersions, liquids, liquid-liquid dispersions or gases

What is shrinkage for Bopp?
For example, the biaxially oriented polypropylene (BOPP) film has a thermal shrinkage measured after 5 min at 120 °C in transverse direction (TD) in the range from 0.05 to 0.3 %, like from 0.05 to 0.2 %. Additionally, the biaxially oriented polypropylene (BOPP) film can have a low shrinkage in machine direction (MD).

Surface Tension -

Surface tension is the tendency of liquid surfaces to shrink into the minimum surface area possible. Surface tension is what allows heavier than water i.e., denser than water objects such as razor blades, insects, to float and slide on a water surface without becoming even partly submerged.

Ductility -

Ductility is a mechanical property commonly described as a material's amenability to drawing. In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stress before failure.

Brittleness -

A material is brittle if, when subjected to stress, it fractures with little elastic deformation and without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Breaking is often accompanied by a sharp snapping sound

The main measurements the end product is subject to are the following:

• Thickness, grammage, density
• Tensile strength, elongation at break and elastic modulus
• Haze (opacity) and Gloss (sparkling appearance)
• Coefficient of friction between film-film and film-metal
• Sealing threshold and sealing strength °C
• Thermic stability (heat shrinkage)