Adhesive technology for automotive color changing film: in-depth analysis of adhesive formula and construction process

Adhesive technology is one of the core processes of color changing film, and its performance directly determines the adhesion, durability, and removability of the film material. This article will analyze from three dimensions: adhesive chemistry, coating technology, and construction techniques.

1. Adhesive Chemistry and Formula Design

The adhesive used for color changing film needs to balance initial adhesion, holding adhesion, and cohesion. The mainstream types include:

Acrylic pressure sensitive adhesive (PSA): It is prepared by lotion polymerization, and polar groups such as carboxyl group and hydroxyl group are introduced into the molecular chain to improve adhesion. In the formula of a certain brand of adhesive, the copolymerization ratio of butyl acrylate and methyl methacrylate is 7:3, which balances flexibility and weather resistance.

Polyurethane adhesive: Using isocyanates and polyols as raw materials, a three-dimensional network structure is formed through addition reactions. Its peel strength can reach 25N/25mm, suitable for body parts with large curvature.

Organic silicone adhesive: with siloxane as the main chain, it has excellent temperature resistance and hydrophobicity. In a certain case, the organic silicon modified film did not peel off during temperature cycling from -40 ℃ to 120 ℃.

2. Coating process and equipment

The coating accuracy of glue directly affects the performance of color changing film, and key technologies include:

Micro gravure coating: The adhesive is transferred through a roller engraved with micrometer sized grooves, and the coating thickness can be controlled to 5-15 μ m. A certain factory uses 200 thread/inch gravure rollers, and the uniformity CV value of the adhesive layer is ≤ 3%.

Comma scraper coating: using adjustable gap scrapers to control the amount of glue, suitable for high viscosity adhesives. A certain device can achieve a coating speed of 30m/min and a glue layer thickness error of ± 1 μ m.

Two component coating: Mix the main agent and curing agent online before coating to enhance reaction activity. In a certain process, the curing time of glue at 60 ℃ is shortened to 30 seconds, resulting in a 40% increase in production efficiency.

3. Construction techniques and skills

The construction of the color changing film needs to be combined with the characteristics of the adhesive and the body structure, and the core steps include:

Surface pretreatment: Clean the vehicle body with isopropanol to remove grease and silicone residue. An experiment showed that unclean surfaces can cause a 60% decrease in adhesive peel strength.

Positioning and bonding: When using the "wet bonding method", it is necessary to control the concentration of the wetting solution (usually a 0.5% detergent solution) to avoid excessive dilution of the adhesive layer.

Exhaust and compaction: Use a rubber scraper to exhaust from the center to the edge at a 45 ° angle, with pressure controlled between 0.3-0.5MPa. In a certain case, bubbles appeared in the area that was not adequately ventilated after 3 months.

Edge and corner treatment: The door handle, lettering, and other parts are cut using a "hot knife cutting" process, using an art knife heated to 150 ℃ to cut along the edges to prevent glue from overflowing.

Technical bottlenecks and breakthroughs

The current bonding technology faces two major challenges: one is the creep problem of adhesives in high temperature and high humidity environments, and the other is the restriction of solvent based adhesives by environmental regulations. The solution includes:

Development of water-based adhesive: By introducing water-based polyurethane dispersion, VOC emissions are reduced to below 50g/L.

Nanoenhancement technology: Adding layered silicate nanoparticles to the adhesive to enhance cohesion and heat resistance.

Removable glue: Design a glue system with a "weak interface layer" to achieve no residual glue peeling after 3-5 years.