Corona Treatment of Pure PP Hollow Sheets: Technical Principles, Necessity, Applications, and Industrial Value

Pure polypropylene (PP) hollow sheets, also known as PP twin-wall sheets or corrugated PP boards, are widely used in packaging, logistics, protective panels, signage, and industrial turnover systems. Compared with composite materials, pure PP hollow sheets offer advantages such as excellent recyclability, strong chemical resistance, and cost efficiency. However, polypropylene is a typical non-polar polyolefin with inherently low surface energy, which creates significant limitations in printing, coating, and adhesion processes. As a result, corona treatment has become a critical surface modification technology in industrial production lines.

Corona treatment is a high-frequency, high-voltage electrical discharge process applied to the surface of PP hollow sheets. When the material passes through an electrode system, surrounding air is ionized under a strong electric field, generating plasma composed of ions, electrons, and reactive oxygen species. These active species interact with the PP surface by introducing polar functional groups such as hydroxyl (-OH), carbonyl (-C=O), and carboxyl (-COOH), while also creating microscale surface etching that increases roughness and improves mechanical interlocking. At the same time, the surface energy of the material is significantly enhanced, improving wettability and adhesion performance. After treatment, the surface energy of PP hollow sheets typically rises from about 30 dynes/cm to 38–52 dynes/cm depending on process parameters such as power, electrode design, and line speed.

Due to the non-polar molecular structure of polypropylene, untreated PP hollow sheets generally exhibit poor ink adhesion in offset, UV, and flexographic printing, weak bonding strength with adhesives and laminating films, delamination risks in multi-layer structures, and reduced durability of printed graphics under outdoor conditions. Therefore, in most industrial applications, corona treatment is not an optional enhancement but a mandatory pre-treatment process required to ensure stable downstream processing performance.

Corona-treated pure PP hollow sheets are widely used in packaging and logistics applications such as reusable transport boxes, automotive parts packaging, and industrial partition systems, where improved surface energy enables high-quality printing of barcodes, logos, and handling instructions. In advertising and visual communication, they are used for corrugated signage boards, display panels, and exhibition materials, benefiting from improved ink adhesion and long-term outdoor stability. In construction protection, they are applied as floor protection sheets and surface shielding materials, where enhanced surface properties support lamination and coating durability. In agricultural and industrial fields, they are used in plant protection panels and separation systems, enabling functional coating, labeling, and customization.

From an industrial perspective, corona treatment significantly increases the value of PP hollow sheet products by transforming inert polymer sheets into functional materials capable of printing, bonding, and surface processing. When integrated inline with extrusion production systems, corona treatment improves manufacturing efficiency by eliminating secondary handling steps and enabling continuous processing. It also supports sustainability by extending product lifecycle through reusable packaging systems, aligning with circular economy requirements. In addition, modern corona equipment ensures stable and uniform treatment across wide-format sheets, improving consistency and quality control in mass production. As a result, manufacturers gain stronger competitiveness in OEM markets, export packaging systems, and customized industrial applications.

Overall, corona treatment is a key surface engineering technology that overcomes the fundamental limitation of low surface energy in pure PP hollow sheets. By improving adhesion, printability, and coating compatibility, it enables polypropylene hollow sheets to function as high-performance industrial materials rather than basic structural plastics. With the continued growth of lightweight, recyclable, and multifunctional material demand, corona-treated PP hollow sheets will play an increasingly important role in packaging systems, logistics infrastructure, and sustainable industrial material development.