Paper and film are two kinds of materials used in in mould labels. The advantage of paper is that there is no electrostatic interference, which reduces the loss of label absorption when blowing bottles. However, paper is easy to deform when it is exposed to water or damp, and the surface smoothness of common synthetic paper is low, so its strength and elasticity make it unsuitable for high-grade color printing.
At present, film is generally selected as the preferred material for in mould labels at home and abroad. Thin film materials have good expansion and contraction properties, especially those that can stretch and shrink, such as Primax and FasClear. In practical application, the material can be deformed with the change of bottle shape, and the label wrinkling phenomenon will not appear on the bottle surface. In addition, the ink absorption of film materials is much lower than that of paper, so labels printed with film materials are bright in color, strong in stereoscopic impression and color effect. Moreover, the film material and the plastic bottle body are homogeneous materials with reusability.
The material structure of in mould labels consists of three parts, namely, printing surface, intermediate layer and adhesive layer. The main function of printing surface is to carry ink and form corresponding color pictures and texts. There are three kinds of printing materials: PE, BOPP and PE+PP. At present, most plastic containers use PE materials, so it is more beneficial to recycle the labels in mold.