In the cosmetics industry, plastic cosmetic treatment pumps are highly favored for their superior convenience, durability and economy. However, the sealing of the pump head is one of the core indicators of its performance, which directly affects the stability of the product and the user experience.

Basic properties of materials
Choosing the right plastic material is the primary consideration to ensure the performance of the pump head, especially its physical and chemical properties. For example, polycarbonate (PC) is widely used in cosmetic pump heads due to its excellent strength, heat resistance and good transparency. However, PC is relatively weak in chemical corrosion resistance, and may swell or corrode for some strong acid or alkaline ingredients, thus affecting the sealing performance of the pump head.
In contrast, materials such as polypropylene (PP) and polyethylene (PE) show superior chemical corrosion resistance and can effectively resist the erosion of most cosmetic ingredients. In addition, these materials also have good processing performance and cost-effectiveness, making them ideal choices for cosmetic pump heads.

Key factors of sealing
In plastic cosmetic treatment pumps, the quality of sealing mainly depends on the tightness of the fit between the pump head and the bottle body and the sealing structure inside the pump head. The choice of materials plays a vital role in both aspects.
The tightness of fit between the pump head and the bottle body is affected by the thermal expansion coefficient and elastic modulus of the material. If the thermal expansion coefficient of the materials used for the pump head and the bottle body is too different, the fit clearance may change when the temperature changes, thus affecting the sealing effect. In addition, the elastic modulus of the material will also affect the tightness of the fit. Materials with a larger elastic modulus deform less when subjected to force, thus providing more stable sealing performance.
The sealing structure inside the pump head usually includes key components such as gaskets and sealing rings. The material selection of these components is also crucial. Taking O-rings as an example, they are usually made of materials such as nitrile rubber (NBR), fluororubber (FKM) or silicone rubber (VMQ). These materials not only have good elasticity, but also have strong chemical resistance, which can ensure that the pump head maintains stable sealing performance during long-term use.

Long-term impact of materials on sealing performance
In addition to short-term sealing performance, the long-term stability of materials is also an important factor affecting the sealing performance of plastic cosmetic treatment pumps. After long-term contact with cosmetic ingredients, some plastic materials may swell, age or degrade, resulting in reduced sealing performance.
To meet this challenge, some manufacturers choose materials with higher chemical resistance and stability, such as polytetrafluoroethylene (PTFE) or polyetheretherketone (PEEK). These materials can not only effectively resist the erosion of cosmetic ingredients, but also maintain their stable performance in harsh environments such as high temperature and high pressure, thus ensuring the long-term reliability of the pump head.