Acrylic foam pressure-sensitive adhesive is widely used in automobiles due to its excellent adhesive strength, sealing performance, and cushioning performance. The door sealing strip is assembled on the car door and used in conjunction with the door frame sealing strip on the side of the vehicle, mainly for sound insulation, dust prevention, and cushioning, while also affecting the opening and closing force of the car door. At present, the mid to high end models in the automotive market generally adopt this adhesive structural design.

This type of car door sealing strip, which uses elastic foam as the base material and is internally impregnated with acrylic adhesive material, has great flexibility in bonding and can fill the surface differences between parts and the body, meeting the bonding requirements of complex shaped surfaces of car door sheet metal. However, in the actual production process, the adhesive process often fails due to various factors, leading to the opening of the door sealing strip. Therefore, plasma surface treatment technology can be used to improve the surface energy of the car door sealing strip, thereby enhancing its adhesive performance and ultimately solving and controlling such adhesive problems from a process perspective.

Pressure sensitive adhesive is a viscoelastic material that possesses both liquid viscosity and solid elasticity. The main component of pressure-sensitive adhesive is polymer, and when the polymer material is in a semi-solid state at the operating temperature range, it exhibits unique viscoelastic properties. The adhesive forms a good wetting on the surface of the bonded object and relies on the generated molecular polarity to form adhesive force. Therefore, for pressure-sensitive adhesives, in order to form a good adhesive force, in addition to providing sufficient pressure, it is also required that the adhesive forms a good wetting on the surface of the bonded object, and good wetting depends on high surface energy.

Plasma surface treatment

Plasma is the fourth state of matter, which contains the same number of free electrons and positive ions, thus exhibiting overall electrical neutrality. Plasma surface treatment technology generates plasma by injecting additional energy (usually electrical energy) into a gas. The following steps describe the formation process of chemical bonds when plasma comes into contact with the material surface:

1) Activate gas molecules. By applying an external electric field, gas molecules (such as argon, oxygen, or nitrogen) are excited into a plasma state, which contains high-energy electrons, ions, and free radicals.

2) Surface cleaning. High energy particles bombard the surface of materials to remove surface pollutants such as grease, dust, and oxides, a process commonly referred to as sputtering or etching effect.

3) Surface activation. High energy particles in plasma break the chemical bonds on the surface of materials, creating new active sites. These sites have high chemical reactivity because they contain unpaired electrons.

4) Functionalization. Free radicals in plasma react chemically with newly formed active sites on the material surface, forming new chemical functional groups. For example, the surface of a material may be oxidized or introduce other chemical groups, altering its surface energy and chemical properties.

5) Chemical bond formation. Functionalized surface chemical functional groups can react with other substances (such as adhesives) to form strong chemical bonds. This enhances the adhesion between the adhesive and the material surface, thereby improving the bonding effect.