Analysis of the damage resistance of car coating film by external force
paint protection film is born for protection, and it is generally valued by car owners to prevent external damage such as scratches, gravel impact, and puncture damage. How to identify the ability of invisible car clothing to resist external damage? What kind of car coating film has higher resistance to scratches, punctures and stone impacts?
01 Performance test methods and data
Although scratches, gravel impact, and puncture damage are all external force damage, which tests the mechanical performance of the invisible car clothing, each invisible car clothing will undergo precise, strict and detailed performance tests before leaving the factory, including scratch resistance test, puncture resistance test and gravel impact resistance test.
● Scratch resistance test
The scratch tester in accordance with the provisions of 4.39.2 in GB/T 17657-2013 was used to test in accordance with the test procedures specified in 4.39.5 in GB/T 17657-2013, the load was 5.0N, and the score was 1 full turn, and the surface of the sample should be free of continuous scratches or obvious damage after the test.
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● Puncture resistance test
The universal testing machine with an accuracy of not less than 0.5 is used for testing, and the puncture resistance should not be less than 130N in the case of TPU automotive paint protection film.
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● Impact resistance test of gravel impact
The gravel impact machine specially designed for the anti-gravel impact test of automotive materials and surface coatings is specially designed to carry out continuous gravel impact for 10s under a certain air pressure, and the paint protective film should have no traces of penetration.
02 What kind of car coating film is more protective?
01
PVC material VS TPU material
Hardness reflects a material's resistance to deformation, nicking, and scratches, but that doesn't mean that a harder material is better suited for invisible livery. Take PVC and TPU as examples:
The film made of PVC is highly hard, and it is able to protect the paint surface by relying on its hard physical properties. However, PVC is a heat-sensitive material, and the decrease in temperature will make the PVC car coating film hard and brittle, which is prone to brittleness; In addition, PVC material is thick, poor ductility, poor fit with car paint, and difficult to build; PVC does not have a scratch repair function, and once scratched, it cannot be restored, which results in the car paint being protected, but the car still looks scarred.
TPU material has higher toughness, fission elongation is greater than 300%, and it is a polymer material with very good resilience after external force removal, so even if the TPU car coating film is ruptured by external force, once the external force is withdrawn, the TPU molecule can be fissioned and stretched, and it can gradually return to its original state (heating can accelerate its healing), leaving no traces. Moreover, compared with PVC, TPU has superior yellowing resistance and longer service life, so TPU invisible car clothing has become the mainstream.
02
Polyether type VS polyester type VS polycaprolactone type
However, it is also a TPU material car coating film, and the wrong choice will greatly reduce the protection effect. This has to start with the molecular structure of TPU.
TPU is composed of alternating soft and hard segments, which bring softness and rigidity to the material respectively, so TPU has both plastic plasticity and mechanical strength, and rubber elasticity. Through the application of different raw materials and the adjustment of the ratio, the TPU film can have excellent resilience and physical properties.
In short, polyether TPU has excellent low temperature flexibility, good product feel, but low cohesion energy, relatively poor peel strength and breaking strength, and poor high temperature resistance compared with polyester; Polyester TPU has excellent mechanical properties, abrasion resistance and tear resistance, but poor hydrolysis resistance. The polycaprolactone type not only has the mechanical strength and high-temperature properties of polyester TPU, but also has the hydrolysis resistance and low temperature resistance of polyether TPU, and has good resilience, so it is more suitable for car coating film.
This is one of the reasons why we have always emphasized that we must look for polycaprolactone TPU when buying invisible car coatings.
The SMM301TPU base film produced by Kaiyang New Materials is made of polycaprolactone TPU particles for Lubrizol car clothing, which has excellent mechanical properties and can protect the car from scratching, gravel damage and puncture damage.
In addition, polycaprolactone TPU also outperforms other types of TPU in terms of weather resistance and hydrolysis resistance, which can be found here.
03 Effect of film thickness on the same material
In the case of the same material, the thicker and stronger the TPU film, the better the impact and puncture resistance, and the less likely it is to be damaged, but at the same time, it will inevitably lead to an increase in hardness, which is not conducive to construction and difficult to wrap the edge. Therefore, only when the TPU film has an appropriate thickness and balanced performance, can its application performance be fully utilized. (We mentioned the TPU thickness selection in the previous article, click here for details).
