BOPP and OPP are one letter short, but what is the actual difference between them?
The difference between BOPP and OPP is that one is longitudinal stretching, the other is both longitudinal and transverse stretching.
This is related to the molecular structure, polymer generally does not exist anisotropy, so there is no difference in the use of materials.
There are some differences between uniaxial and biaxial stretching. In the process of unidirectional drawing, the injected film material enters into the drawing unit composed of many rolls through the nozzle after forming, and the roll speed is different. As a result, the thickness of the film can be changed with the change of the length. The tear resistance of the film can be improved by uniaxial tension, so the braided wire of rope, packing tape or bag is produced by this process. The thickness of the film is between 25 and 800 μ M.
In biaxial stretching, the film pre stretched in meridional direction is stretched in orthogonal direction with the same length as extrusion direction. With the development of linear motors, the above drawing processes can be flexibly connected together and the efficient forming of longitudinal and transverse biaxial drawing becomes possible. This is called "synchronous" biaxial stretching, without complex transmission and chain structure. The manufacturer of this kind of synchronous tensile equipment thinks that the higher the uniformity of polymer stress, the higher the elastic coefficient, tear resistance and tensile strength can be given to the product.
