Adding hydrophilicity to resins Development Department of Company L, a Resin and Plastic Manufacturer
Impart hydrophilicity to molded parts
PVP polymerization achieves hydrophilic surface
Company L manufactures a wide range of molded parts using thermoplastic resins. One day, a client contacted them with a question: Is it possible to give the surfaces of parts used in their products hydrophilic properties? Company L immediately began work, but the development process was extremely difficult.
Challenges
There is a demand for hydrophilic surfaces for thermoplastic resin molded parts, but technological development to achieve the desired performance has not progressed...
When we interviewed the customer, we learned that they wanted to make the surfaces of molded parts hydrophilic in order to improve functions such as preventing dirt from adhering to the surface of the parts, preventing static electricity, and preventing fogging.
Mr. K from the development department, who was in charge of this project, described the situation at the time as follows:
"Thermoplastic resins are generally hydrophobic, meaning their surfaces have weak interactions with water and are not compatible with water. To make the surface of a molded part hydrophilic, we need to change the properties of the part's surface."
Mr. K first tried corona treatment and plasma treatment, which he was familiar with, on the surface of resin parts. However, these treatments were difficult to apply to molded parts, and he was unable to impart sufficient hydrophilicity.
Next, we investigated methods of spraying or painting a coating agent containing a hydrophilic agent such as a surfactant. Immediately after spraying the coating agent, the surface of the part was able to be made hydrophilic. However, the hydrophilic agent was removed by wiping or washing, and the hydrophilicity could not be maintained.
Furthermore, we investigated a method of melt-kneading water-soluble polymers such as PVA (polyvinyl alcohol) and PEG (polyethylene glycol) into the resin. However, at the temperatures required to melt the thermoplastic resin, these water-soluble polymers decompose, causing foaming and discoloration, which not only impaired the appearance but also prevented the expected hydrophilicity from being achieved.
We tried making prototypes repeatedly, changing the type of additive and the compounding method, but the results were always disappointing and the performance was far from satisfactory.
With customers urging him to complete the parts, Mr. K was at a loss as to what to do.
Key Challenges
We wanted to give hydrophilicity to the surface of a thermoplastic resin molded part, but we were unable to achieve the desired hydrophilicity despite trying various methods.
We investigated a method of melt-kneading a water-soluble polymer, but foaming and discoloration occurred at the temperature required to melt the thermoplastic resin, making it impossible to impart hydrophilicity.