Biaxially oriented polypropylene (BOPP) film is a type of flexible packaging film. Biaxially oriented polypropylene overwrap film is stretched in machine and transverse directions. This results in a molecular chain orientation in both directions.

This type of flexible packaging film is created via a tubular production process. A tube-shaped film bubble is inflated and heated to its softening point (this is different from the melting point) and is stretched with machinery. The film stretches between 300% - 400%.

Alternatively, the film can also be stretched by a process known as tenter-frame film manufacturing. With this technique, the polymers are extruded onto a cooled cast roll (also known as a base sheet) and drawn along the machine direction. Tenter-frame film manufacturing uses several sets of rolls to create this film.

The tenter-frame process generally stretches the film 4.5:1 in the machine direction and 8.0:1 in the transverse direction. That being said, the ratios are fully adjustable.

The tenter-frame process is more common than the tubular variant. It produces a highly glossy, clear film. Biaxial orientation increases strength and results in superior stiffness, enhanced transparency, and high resistance to oil and grease.

BOPP film also boasts increased barrier properties to vapor and oxygen. Impact resistance and flexcrack resistance are substantially better with BOPP versus polypropylene shrink film.

Biaxially oriented polypropylene overwrap films are most commonly used for food packaging. They are fast replacing cellophane for applications including snack food and tobacco packaging. This is primarily due to their superior properties and lower cost.

Many companies choose to use BOPP in place of traditional shrink films as they feature enhanced properties and capabilities that are superior to those of standard flexible packaging films.

It should be noted that heat sealing is difficult for BOPP films. However, this can be made easier by coating the film after processing with a heat-sealable material or co-extruding with a co-polymer before processing. This will result in a multi-layer film.