Etching Process of PTFE and the Preservation and Use of PTFE Etching Tube
PTFE is a remarkable non stick material. Due to its chemical inertness and low surface energy, PTFE is difficult to adhere to other materials, which limits its application. What should you do when you need to stick it to the surface of another material? In order to bond standard PTFE to another surface (such as stainless steel), a process called etching is required. So sometimes surface treatment is needed in applications. In order to improve the adhesion between PTFE and different materials, solve the problem of material surface etching, and meet the needs of production and production, it can be achieved by modifying the adhesive method, improving the surface activity of PTFE, or applying both methods simultaneously. There are various methods for treating the surface of PTFE, such as wet chemical method, mechanochemical method, melting, radiation, plasma treatment, laser treatment, etc.
1： Typical Applications of Etched PTFE
Typical applications include lining chemical treatment tanks or other equipment used in harsh environments. When bonding is required, ammonia sodium etching is usually the most economical choice. This method uses a mixture of sodium and ammonia, which can be quickly and effectively prepared to produce a cohesive surface. Sodium/ammonia etching services comply with all applicable commercial, military, and federal specifications for surface treatment of all fluorinated polymers, including PTFE, PFA, FEP, ETFE, PCTFE, PVDF, PVF, and ECTFE.
From microchips to full-size coils, fluorinated polymers of any shape or complexity, including tapes, sheets, pipes, molded shapes, and any configured machined components, can be etched and bonded. This treatment can be completed on one or more surfaces, or selectively within a tolerance range.
Attention: The surface after etching will change color to a brown appearance.
Can be single-sided (EOS) (standard) or double-sided (E2S) etched
2： Surface modification method and plasma etching of polytetrafluoroethylene
The first type is to use surface activation technology, which can continuously defluorinate its surface through radiation, and then fluorinate and graft with other materials under specific conditions. It can also be treated with inert gas to break some of the main bonds it covers and form many free radicals, thereby increasing the surface free energy it covers. Ultimately optimize its wettability. In addition, PTFE can be treated by corona discharge, which can produce an adhesive activated layer.
The second type is modified through chemical corrosion. This method can optimize its surface activity, and there are various reagents available for selection. Representative solutions include ammonia solution, pentacarbonyl iron solution, etc.
The third type is through surface deposition modification, specifically by immersing PTFE in a specific colloidal solution, allowing colloidal particles to continuously deposit on its surface and improve its wettability, ultimately optimizing its surface activity so that it does not encounter too many obstacles when composite with other materials.
Dry etching method using surface activation technology: Plasma etching is one of the most rapidly developing technologies for PTFE surface modification in recent years.
AOkeray’s PTFE plasma treatment method is as follows:
Introduction to PTFE Plasma Etching Principle: Plasma etching is the most common form of dry etching. Its principle is that gas exposed to the electron region forms a plasma, which generates ionized gas and releases high-energy electrons to form plasma or ions. When ionized gas atoms accelerate through an electric field, they release enough force to tightly adhere to the material or etch the surface.
The essence and process of PTFE plasma treatment technology is to place the sample in a specific plasma treatment device, and through ion bombardment or injection into the surface of the polymer, break bonds or introduce functional groups, making the surface active to achieve the purpose of modification. Ions can be inert gases, chemically active gases, or metallic elements. The bombardment of inert gases can alter the surface structure of polymers. There are studies reporting that under high pressure (6.7 × 10 * Pa), the vacuum ultraviolet (UVU) radiation source generated by He and Ar plasma is used for surface photolithography treatment of PTFE. The surface oxygen atom content increases, while the fluorine atom content decreases, resulting in a decrease in its water contact angle from 110 ° to 43 °. Metal ion implantation plays a role in surface doping. Except for the high dosage of metal ion implantation to improve the wear and corrosion resistance of polymers, the amount of ion implantation is generally very small. Meanwhile, the long process required for metal ion implantation also limits its application in industrial production. When active gases such as hydrogen, oxygen, ammonia, argon, etc. generate plasma to bombard the surface of polymers, functional groups containing active gas elements are introduced on the surface of polymers to improve surface inertness and increase surface free energy.
Overall, the durability of polymer surfaces treated with plasma is unstable. Therefore, surface applications such as coating and bonding after plasma treatment should be carried out as soon as possible. Meanwhile, due to the restructuring of the surface structure, it is impossible to maintain the hydrophilicity of the treated surface for a long time without decreasing. However, the advantages of plasma etching are also very obvious. For example, ① the materials are vast: from microchips to full-size coils, any shape or complexity of substrate, such as tape, sheets, pipes, molded shapes, and any configuration of machined parts, can be etched and bonded. ② It belongs to dry etching, which utilizes chemical active atomic groups in the plasma to undergo chemical reactions with the etched material. The entire process does not require the participation of water and chemical solvents, making it more environmentally friendly Process Health: Plasma production only requires electricity and process gas, and will not produce harmful substances, without causing harm to the operator’s body; The device operation is also very simple, with an intelligent operation screen that is easy to get started with.
In summary, various surface treatment methods of PTFE are achieved through various physical methods or chemical reactions, introducing surface functional groups or changing the chemical structure of the surface to improve its surface roughness, ultimately achieving the goal of reducing contact angle, improving surface energy, and enhancing adhesive performance. The research on surface modification of PTFE has made it widely used in various fields. Only by systematically mastering and flexibly applying various modification methods can the application range of PIFE become more extensive.
3： Key points for the use and preservation of PTFE etching tubes
PTFE is a very stable material that is almost difficult to chemically react and bond with other materials. It is also a material that is quite easy to preserve. Usually, PTFE pipes appear transparent or milky white, with the majority of PTFE pipes being milky white.
However, after etching, PTFE pipes will exhibit almost completely different characteristics from ordinary PTFE, becoming particularly sensitive and vulnerable, and the color will also appear brown.
The etching layer of PTFE is very susceptible to the influence of water vapor in the air, UV light in daily environments (including fluorescent lamps), and heat. Therefore, its preservation should pay great attention to the isolation of the above three factors, and try to store it in a dark and constant temperature and humidity place. The key points are:
- It is recommended to place it in the middle of the shelf or near the bottom to avoid direct sunlight and fluorescent lamps. Do not use only dark packaging bags for long-term storage. Placing it in a cardboard box or having an object covering it is a more recommended method
- It is recommended to store for a long time for no more than 1 year. If the packaging bag is opened and the etching tube is removed, it should be used within 4 hours as much as possible. Unused etching tubes should be immediately sealed back in packaging and placed in the warehouse. If the etching tube has already been unpacked and is temporarily stored in the production line area, it is recommended to use it up within a week after the packaging is sealed. (All the above time values are recommended by experience. When moisture, ultraviolet light, and heat are isolated, there is a possibility of prolonging these times.)
The only reliable indirect indicator to characterize the surface etching ability of PTFE is the contact angle, and the factory standard of international leading companies is<75 °. Da Ying pen can only be used for indirect comparison of contact angles to distinguish the size relationship of indirect contact angles between two samples. Can only be used as a quick inspection method. For formal testing, please use the Contact Angle/Water Drop Angle Tester
- Stretching and heating the etching tube can reduce the integrity of the etching layer, and the impact of stretching is often much greater than that of heating. Shanghai Jinfu Chemical recommends a maximum tensile strength of no more than 15% (including overall and local)
For example, using 5% stretch as the standard value:
a. When stretched by 10%, the bonding force of the PTFE etching layer decreases to 80%,
b. When stretched by 20%, the bonding force of the PTFE etching layer decreases to 40%,
c. When stretched by 30%, the bonding force of the PTFE etching layer decreases to 20%,
The PTFE inner liner with core rod also solves the problem of etching layer damage caused by stretching to a certain extent; The PTFE inner lining tube with adhesive layer to some extent solves the problem of etching layer storage. If you need to know about PTFE inner lining pipes with core rods or PTFE inner lining pipes with adhesive layers, please contact sale@medicalptfe.com
