PET (polyethylene terephthalate) materials are widely used in packaging, electronics, automotive, medical and other fields due to their light weight, high transparency, chemical resistance and excellent mechanical properties. However, the low polarity and smoothness of the PET surface make it face the problem of insufficient adhesion when combined with other materials (such as resins). Especially in high value-added products such as optical devices, high-end packaging and electronic components, the combination of PET and resin requires not only high adhesion, but also high performance and functional requirements. This article will explore in depth the characteristics of PET materials, adhesion challenges, and how to achieve efficient bonding through specific resins and apply them to high value-added products.
1. Characteristics and Adhesion Challenges of PET Materials
PET materials have the following core characteristics:
High strength and toughness: excellent impact resistance, suitable for manufacturing films, bottles and other products.
Chemical corrosion resistance: good tolerance to solvents such as acids, alkalis, and oils.
Low surface energy: low surface polarity (surface tension of about 40-50 mN/m), making it difficult for resins, coatings or adhesives to adhere effectively.
Smooth surface: lack of microscopic roughness, further reducing the mechanical bite force.
Consequences of insufficient adhesion:
The coating or adhesive layer is easy to peel off, affecting the appearance and functionality of the product.
Low bonding strength leads to assembly failure or poor sealing.
Interface peeling is accelerated due to environmental factors (humidity, temperature) during long-term use.
2. Key technologies for improving the adhesion of PET materials
To overcome the adhesion problem of PET materials, it is necessary to start from three aspects: surface treatment, special resin selection and process optimization:
1. PET surface treatment technology
Corona treatment: Through high-frequency and high-voltage discharge, polar groups (such as hydroxyl and carboxyl) are introduced on the PET surface to significantly increase the surface energy and enhance the chemical bonding with the resin.
Plasma treatment: Use plasma to bombard the surface to form a microscopic rough structure and increase the active groups to enhance the mechanical bite and chemical bonding.
Chemical primer: Apply a primer containing silane coupling agent or polyurethane to form a "bridge" between PET and resin to improve interface compatibility.
2. Selection of special resins
The low surface energy characteristics of PET materials require the use of specific resins to achieve efficient adhesion, especially in high-value-added products, the resin must also have high performance and functionality:
Polyurethane resin (PU): It has excellent flexibility, weather resistance and bonding properties, and is suitable for automotive interiors, high-end packaging and other fields.
Epoxy resin: By adding adhesion promoters (such as silane coupling agents), the bonding strength with PET can be significantly improved, which is suitable for high-precision fields such as electronic component packaging.
UV curing resin: Rapidly cured by ultraviolet light, suitable for high value-added products such as optical devices and display screen protective layers.
Functional resin: Such as conductive resin and barrier resin, which can meet the special needs of electronics, packaging and other fields.
3. High value-added application scenarios of PET combined with special resins
Optical devices:
Display screen protective layer: PET film is coated with UV-curable resin to improve wear resistance and scratch resistance, suitable for high-end electronic products such as smartphones and tablets.
Optical film: Use highly transparent polyurethane resin to enhance the adhesion and functionality of PET optical film.
High-end packaging:
High barrier coating: Epoxy resin is coated on the surface of PET bottles or films to improve oxygen and moisture barrier properties and extend the shelf life of food and medicine.
Decorative coating: Use functional resins (such as metal texture coatings) to enhance the appearance and added value of packaging.
Electronic manufacturing:
Flexible circuit board: PET film is used as the substrate and coated with a polyimide resin layer. Plasma treatment is required to ensure the interlayer bonding strength.
Display screen encapsulation: The bonding of UV-curable resin and PET needs to take into account both transmittance and durability, which is suitable for high-end products such as OLED displays.
PET materials are difficult to adhere to, which requires a resin with extremely strong adhesion. Our resin is a tetrafunctional polyester modified acrylate UV resin with a very wide range of adhesion capabilities. It can be used on PET, nylon plus glass fiber, BMC, PBT, PPS, PMMA, and other organic polymer synthetic materials and inorganic material surfaces that are extremely difficult to adhere to. As the main resin of the free radical curing system, it is used in the fields of coatings, inks, and adhesives for special requirements of high value-added products.
