Discussion on the Significance of Surface Modification of Polyolefin PE Stretch Film

1. Structure of PE stretch film

Materials are widely used. The improvement of people's living standards, the country's industrial construction and national defense construction are inseparable from materials. In particular, the rapid development of polymer materials is mainly due to their wide molecular weight distribution, light weight, low density, excellent mechanical properties, insulation properties and other characteristics and changeable structures. However, a large number of surface and interface problems, especially the surface wettability problem, limit its application in some aspects. In order to meet the needs of the society for materials, it is necessary to modify the wettability of the surface of the polymer. Polyethylene is a thermoplastic resin made by ethylene polymerization, referred to as PE. Polyethylene is a crystalline high polymer, which is widely used in various fields such as hygiene products, packaging, daily necessities, and electrical appliances due to its advantages such as light weight, low price, non-toxic, odorless, corrosion resistance, and low dielectric constant. However, polyolefins (PP, PE, PS, PVC, PTFE, PMMA) are non-polar polymers, and surface and interface problems make them non-wetting, poor dyeability, abrasion resistance and printability, which hinder the development of such materials. promote.

2. The surface of PE stretch film has the following characteristics

A) Low surface energy, the critical surface tension is generally only (31~34)x105N/cm, so the contact angle is large, and the ink and adhesive cannot fully wet the substrate, resulting in poor adhesion to the substrate.

B) smooth surface. The surface of polyolefin polymer materials generally has small pores, which prevents the adhesive from penetrating into the material and forming a firm mechanical connection.

C) The surface boundary layer is weak. Polyolefin polymer materials have a wide relative molecular weight distribution, in which molecular chains with smaller molecular weights tend to migrate to the surface, and various additives added during processing also weaken the surface boundary layer.

D) High crystallinity, so swelling or dissolution is difficult. When printing ink, adhesive, and finishing agent are on the surface of the polymer, it is difficult for the molecular chains of the polymer to diffuse or entangle with each other, resulting in poor adhesion.

E) Non-polar polymer materials, which make it impossible to form strong bonds with adhesives containing polar substances such as oxygen atoms, nitrogen atoms and other electron-rich atoms.

Based on the above reasons, the surface modification of polyolefin films has far-reaching significance in broadening its application range.