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Zhejiang Newcastle · News Weekly | Issue 6: 315 Consumer Rights Day – How Harmful Are Low-Quality Films?
To understand the hazards of inferior films, we first need to look at the structure of paint protection film (PPF). A TPU paint protection film consists of five layers:
Layer 1: PET Protective Film
Serves to protect the coating of the paint protection film and will be peeled off during film cutting.
Layer 2: Self-Healing Scratch-Resistant Layer
Protects the base material, providing dirt resistance and stain resistance.
Layer 3: TPU Base Layer
Protects the car paint from scratches and abrasions.
Layer 4: Adhesive Layer
Used to attach the film to the vehicle body.
Layer 5: PET Protective Film
Protects the adhesive layer and will be peeled off during installation.
Why do inferior car paint protection films suffer from yellowing, hydrolysis, adhesive residue and bubbling?
Based on the molecular structure of TPU substrates, they can be classified into aromatic TPU and aliphatic TPU.
Aromatic TPU contains two benzene rings in its structure, one of which features an easily oxidized methylene bridge. This is the primary reason it is highly susceptible to yellowing when exposed to thermal oxidation and UV radiation during processing and use. Even with UV stabilizers added, long-term light exposure will still result in discoloration and yellowing. TPU of this material is mainly used in synthetic leather, construction films, and similar applications.
In contrast, aliphatic TPU contains no benzene rings, resulting in a more stable molecular structure. Additionally, the molecular density of aliphatic TPU is several times that of aromatic TPU. Therefore, paint protection films made from aliphatic TPU are resistant to delamination, bubbling, and edge lifting, while providing longer-lasting protection.
Depending on their chemical properties, aliphatic TPU can be further subdivided into: polyester-based, polycarbonate-based, polyether-based, and polycaprolactone-based types.
Polyester-based and polycarbonate-based TPUs contain easily hydrolyzable ester groups. When attacked by water molecules, their molecular chains break, and the acids produced by hydrolysis further catalyze additional hydrolysis. These raw material grades are lower in cost but exhibit poor water resistance.
Polyether-based TPU offers good flexibility because the ether groups in its soft segments are highly rotatable. Since polyether contains no ester groups that are susceptible to hydrolysis, it has better hydrolysis resistance than the aforementioned types. However, it exhibits inferior heat resistance, oil resistance, and tear strength.
Polycaprolactone TPU features a molecular structure intermediate between polyester and polyether, combining the advantages of both. Containing neither ester groups nor ether bonds, it delivers superior overall performance: excellent abrasion resistance and tear strength, as well as good elongation and hydrolysis resistance. TPU paint protection films manufactured from aliphatic polycaprolactone TPU pellets offer a warranty period of more than 8 years.
Adhesive residue is an issue with the adhesion between the TPU base layer, adhesive layer, and automotive paint surface.
Inferior car films generally use TPU base materials that tend to harden easily, which reduces the adhesion between the base layer and the adhesive layer. Meanwhile, the low-quality adhesive exhibits poor heat resistance and durability. Under long-term exposure to sunlight and rain, the adhesive layer will gradually separate from the TPU base. Eventually, the adhesion between the TPU base and the adhesive layer becomes weaker than the adhesion between the adhesive layer and the car paint, resulting in adhesive residue.
Therefore, if you choose a substandard paint protection film, various problems will arise soon after application. In severe cases, it may even peel off the original car paint, producing the opposite effect. The adhesive residue left after film removal will also cause damage to the car paint.
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