How does fluorination improve the chemical resistance of round bottles?

Basic principles of fluorination treatment
Fluorination treatment refers to the introduction of fluorine gas or fluoride into the plastic surface under certain conditions to react with the molecules in the substrate, thereby changing the chemical structure of the material surface. Taking HDPE as an example, its molecular chain is mainly composed of carbon-hydrogen bonds. During the fluorination process, some hydrogen atoms on the surface are replaced by fluorine atoms to form stable carbon-fluorine bonds.
*Strong stability of carbon-fluorine bonds: The bond energy of carbon-fluorine bonds is much higher than that of carbon-hydrogen bonds, and is not easily destroyed by most chemicals.
*Enhanced surface polarity: The fluorine element has extremely high electronegativity, which changes the surface of the material from hydrophobic and oleophobic to relatively inert and more resistant to chemical erosion.
*Reduced permeability: After fluorination treatment, the gap between molecular chains is reduced, which reduces the penetration and diffusion of small molecule chemicals (such as solvents).
This change at the molecular level has significantly improved the ability of fluorinated plastic bottles to resist solvents, oils, organic acids, alkaline liquids, etc.

Methods and processes of fluorination treatment
Fluorination treatment is mainly divided into two methods: external fluorination and internal fluorination. Different processes have slightly different focuses on performance improvement.
External fluorination treatment
In a closed reaction chamber, the bottle is exposed to a mixture of fluorine and nitrogen, and the fluorine molecules react with the surface of the bottle at a certain temperature and pressure. This treatment method is suitable for products with high requirements for external impermeability, such as chemical barrels and oil bottles.
Internal fluorination treatment
By filling the bottle with low concentration of fluorine gas, a carbon-fluorine bond film layer is formed on the inner wall surface. It is often used for packaging with high requirements for the chemical stability of the contents, such as pesticide bottles and reagent bottles.
Process variables
* Reaction time: affects the degree of fluorine atom replacement. The longer the time, the thicker the surface treatment layer.
* Fluorine gas concentration: The concentration must be controlled within a safe range and affects the uniformity of the treatment.
* Temperature control: High temperature helps accelerate the reaction, but it is necessary to prevent material deformation.
Different combinations of fluorination depth and treatment process will directly affect the final chemical resistance performance of the bottle and the types of liquids that can be applied.

Effect of fluorination on chemical tolerance
The fluorinated plastic round bottles show improvements in chemical adaptability in many aspects, as follows:
*Stronger solvent resistance
The fluorinated surface structure has a stronger barrier effect on non-polar and partially polar solvents (such as acetone, toluene, and diesel), reducing the swelling, softening, and even cracking of the bottle body by the solvent.
*Lower permeability
Untreated HDPE bottles will have slow gas or liquid penetration due to the large gap in their molecular structure, while fluorination can significantly reduce the permeability and extend the shelf life of the contents.
*Improved anti-aging performance
Many chemicals will promote plastic oxidation and brittleness in long-term contact. The fluorinated carbon fluorine structure is more stable and has enhanced resistance to oxidation reactions, which helps the bottle maintain physical strength.
*Enhanced corrosion resistance
The surface inertness is improved after fluorination, and it is not easy to react with strong acid and strong alkali liquids, reducing the risk of corrosion of the contents to the bottle body, and is suitable for more types of industrial chemicals.

Application value of fluorination treatment
In practical applications, fluorinated round bottles are widely used in the following scenarios:
*Chemical industry
Used to store highly volatile or corrosive liquids such as gasoline, diluents, inks, pesticides, etc. Fluorination treatment can reduce the volatile loss of contents and improve packaging safety.
*Pesticide packaging
Many pesticide concentrates have strong solubility or corrosiveness. The use of fluorinated bottles can improve packaging stability and prevent the bottle from softening, cracking or leaking.
*Medicine and laboratory supplies
Some drugs and chemical reagents have special requirements for packaging materials. Fluorinated round bottles are suitable for storing highly sensitive or active substances due to their inert surface.
*Industrial lubricants and additives
Suitable for storing solvent-containing lubricant products to prevent structural deformation or leakage of containers after long-term use.

Limitations and precautions
Although fluorination treatment can significantly enhance the chemical resistance of plastic bottles, there are also certain limitations:
*Increased cost: Fluorination treatment is a secondary process, which increases the manufacturing process and cost. It is suitable for occasions with clear requirements for chemical resistance.
* Limited repeatability: Once the bottle is damaged or aged, it cannot be reprocessed or recycled, and environmentally friendly recycling needs to be classified separately.
* High requirements for environment and operation: Fluorine gas is corrosive and toxic, and equipment sealing and safety measures must be strictly controlled during the processing.
In actual selection, factors such as content characteristics, storage cycle, transportation environment and economic cost should be comprehensively considered to determine whether fluorination treatment should be used.