The Importance of Applying Aluminum Profile Protective Film

Protective film serves as a crucial surface protection material, particularly within the realm of pressure-sensitive adhesives (PSA). Typically, it is composed of polyolefin plastic film as the base material and acrylic polymer as the base resin for the pressure-sensitive adhesive, processed using a coating machine.

Its primary function is to provide temporary protection against surface scratches during the storage, transportation, and circulation of goods, or between various processing steps of the substrate.

Widely utilized across various industries, protective film finds extensive application in safeguarding surfaces such as aluminum panels, aluminum-plastic composite panels, mirror-finish steel plates, colored panels, plexiglass panels, decorative panels, aluminum profiles, plastic steel profiles, stainless steel coils, marble materials, and display screens.

Protective films for aluminum profiles are typically crafted from a polyethylene (PE) film with a tailored formula. The main material for the pressure-sensitive adhesive is polyacrylic acid (ester) resin, which undergoes coating, slitting, and processing during packaging and other manufacturing stages.

These films boast a soft texture, excellent adhesion properties, and are simple to apply and remove. Moreover, the pressure-sensitive adhesive maintains stability and does not cause any adverse effects on the surface of the aluminum profile being filmed.

1. The structure and material characteristics of the protective film

1.1 Film

Films typically utilize low to high-density polyethylene (PE) and polyvinyl chloride (PVC) as raw materials. They can be manufactured through extrusion molding, injection molding, and blow molding techniques. Due to its cost-effectiveness and environmental friendliness, around 90% of films are made from polyethylene, primarily through blow molding. Polyethylene comes in various types with different melting points and densities.

1.2 Adhesive

The quality of aluminum profile protective films hinges on the characteristics of the adhesive. Two types of pressure-sensitive adhesives are commonly used: solvent-based polyacrylate glue and water-soluble polyacrylate glue, each with distinct features.

1.2.1 Solvent-based polyacrylate glue

Solvent-based polyacrylate glue employs organic solvents to dissolve acrylic monomers. This adhesive is highly transparent, possesses relatively low initial viscosity, and exhibits excellent resistance to aging. It can endure up to 10 years, gradually curing when exposed to ultraviolet rays. Corona treatment enables direct coating of polyacrylate glue without primer. However, its hardness and poor fluidity may lead to slower adhesion of the protective film. Even after pressure, complete contact between the glue and the surface may not be achieved immediately. Full adhesion typically occurs after 30 to 60 days, with final viscosity often 2 to 3 times higher than initial viscosity. If the film's viscosity is too high, end-users may encounter difficulty when tearing it off.

1.2.2 Water-soluble polyacrylate glue

Water-soluble polyacrylate glue dissolves acrylic monomers in water and shares similar characteristics with solvent-based polyacrylate glue. However, it should minimize contact with water and air to prevent residual glue. This type of glue is favored in developing countries due to its environmental friendliness and the absence of a solvent recovery device requirement.

2. Production of Protective Film

2.1 Production Process

In the production process, polyethylene particles are fed into a heated drum where they are pushed by a screw towards the round die head. Compressed air is then used to blow the molten liquid, which is subsequently air-cooled and rolled into a film.

The blown film exhibits different properties in the transverse and longitudinal directions. Typically, the elongation in the machine direction of the protective film exceeds 180%, while the elongation in the transverse direction is generally over 380%. However, elongation is inversely proportional to mechanical strength.

Excessive elongation, such as exceeding 500%, often results in very low mechanical strength of the film. This makes the protective film susceptible to damage during transportation and handling. Additionally, during unwinding, the protective film is prone to stretching, and after cutting, it may rebound and warp.

3. Application of Protective Film

Typically, the aluminum profile film application machine is equipped with a curved roll (Banana roll) to facilitate the opening of the protective film and prevent bubbles and wrinkles.

For low-viscosity protective films, it is essential to maintain low tension during unwinding to prevent edge warping.

The application temperature should be above 10°C, and the tearing temperature should also exceed 10°C.

The peeling force is influenced by the speed and angle of the film tear.

Insufficient temperature can harden the protective film and cause edge warping. To mitigate this, apply hot air or operate in an air-conditioned environment.

During rewinding, air may be trapped in the adhesive, resulting in slight unevenness on the rubber surface.

If the rubber pressure roller is too soft, it may fail to expel air bubbles and flatten the adhesive effectively.

Conversely, if the rubber pressure roller is too hard, it may not apply sufficient pressure for proper contact between the adhesive and aluminum profile, potentially causing edge cutting issues.

Since the rubber pressure roller tends to age and harden over time, it should be regularly inspected and replaced as needed.

4. Application of Protective Film in the Aluminum Industry

Protective film is a layer of plastic film applied to aluminum materials, serving to safeguard the surface of aluminum profiles during various processes like handling, storage, transportation, processing, and installation.

Once installation is complete, the engineering team removes the film, revealing a pristine surface, achieving the desired decorative effect.

Aluminum profiles come in various types, and surface treatment technologies for aluminum materials continually evolve. These treatments include mechanical polishing, chemical polishing, anodizing, electrophoretic painting, chemical coloring, fluorocarbon spraying, electrostatic powder coating, and wood grain effect sublimation treatment.

Different surfaces of aluminum profiles require different adhesive protective films. These films are categorized into low viscosity, medium viscosity, high viscosity, and extra high viscosity series, with colors ranging from transparent to milky white, blue, and black and white, and thicknesses from 30 to 200μm.

Selecting the appropriate protective film depends on factors like the surface treatment method and film pressure, with the viscosity rise speed varying accordingly. It is crucial to allow sufficient time for the protective film to set before peeling it off to ensure proper adhesion.

For subsequent processing steps like cutting, bending, drilling, and stamping, the choice of protective film viscosity is pivotal. Low-viscosity films suit smooth surfaces like mechanically polished or chemically polished aluminum profiles, while medium-viscosity films are suitable for moderately rough surfaces like anodized or powder-coated profiles. High-viscosity films are ideal for very rough surfaces like electrostatic powder-coated profiles, and super-high-viscosity films are necessary for laser cutting applications due to heat-induced shrinkage.

Apart from viscosity, users should also evaluate the tensile strength and elongation of the protective film to ensure it meets the flexibility and strength requirements for the intended application.

5. Conclusion

Throughout the transportation, storage, processing, and assembly stages of aluminum materials, safeguarding the surface of aluminum profiles is imperative to prevent damage from harmful gases, microbial corrosion, dust pollution, mechanical scratches, and abrasions. This preservation ensures that the product's surface maintains its original smoothness, thereby enhancing secondary processing yield. Additionally, protective films serve as temporary shields in electroplating, printing, coating, and dyeing processes.

The predominant method for safeguarding aluminum profiles is by applying a protective film onto the surface. Although protective films are auxiliary materials in the aluminum industry, their significance cannot be overstated. Improper usage or failure to meet requirements risks not only ineffective protection but also potential damage to the surface. Such lapses can result in tangible material loss and intangible brand image damage for users, ultimately impacting a product manufacturer's pricing strategy and sales performance.

Correct application of protective films not only elevates the appearance quality of aluminum profiles, streamlines material processing, increases material utilization rates, and reduces production costs but also enhances a company's brand image.