Processing of Teflon PETFE plastic raw material can be roughly broken down into four different types: roll molding, compression molding, injection molding, and secondary.
1. Fluoroplastic molding
Fluorine-based plastic molds can produce plates, tubes, sleeves and diaphragms as well as tapes, sealing rings and sealing rings.
There are three stages to compression molding: preforming (or sintering) and cooling. To preform, you add PTFE powder to the mould and pressurize the product at room temperature. Sintering involves heating the preform beyond its melting point. Finally, cooling refers to lowering the sintering temperature back to ambient.
Certain fluoroplastics may be pressured at temperatures above their melting points. This molding die is known as a hot compression, while the corresponding PTFE den is known as a cold compression.
It is important to consider how compression ratio and shrinkage rates affect the product when moulding.
It is preferable to use a suspension method for polymerizing the raw material. This allows you to choose a fine, soft powder that has granularities between 20-500 microns. The pressing pressure must be 17-35 MPa. The holding time is determined by the thickness of your blank. A blank 100 mm in thickness should be retained for at least 15 minutes.
Pay attention to the heat rate of sintering. It can vary from 20 to 120 BTU/hour. A slower heating rate is required for larger products. Suspension resin’s sintering temperatures are higher (370-380), while dispersion resin’s sintering temperatures are lower (360-370). The sintering temp is also high at 370. This causes shrinkage to increase and increases porosity. It is important to control the time of sintering.
The speed at which slow cooling is used to cool the system is usually between 15 and 25 degrees Celsius per hour. Extreme cases such as thin plates less than 5 mm thick or push-moulded thinwalled tubes can use rapid cooling.
Sometimes products may be annealed at 100 to 120 deg C for up to 4 hours.
2. Roll forming with fluoroplastic
The PTFE diaphragm can be roll-formed. You can choose between unidirectional or multi-directional roll forming. After being rolled, the PTFE diaphragm transforms from an opaque to a transparent crystal colour.
To reheat transparent film quickly and process it using two identically rotating rolling wheels of the calendar, one-way rolling can be used. Roller magnification ranges from 1.5 to 2.5. The general speed of the roller is 20 rpm.
Multi-directional Rolling is a form of moldmaking in which the quenched and sintered film is placed onto a calendar. This allows for multi-directional rolling. It gradually decreases the thickness. Rolling ratios range from 2-2.5 to 3-9. Controlling the temperature should take place between 150 to 200 deg C. The steam pressure when heated by steam can be 0.5 to 9 MPa. It is important to control the rolling ratio. Products that are too big or small may not be suitable. Sometimes, repeated rolling is required to press the product.
3. Fluoroplastic injection molding
It is a copolymer of perfluoroalkyl and tetrafluoroethylene, which means that meltable PTF can be injection molded. Its melting point is 425°C, while its temperature at decomposition is above 450°F, so it is easy to control. The temperature range for PTFE injection molding is typically 330-410°C.
PFA does not require drying due to its low hygroscopicity (0.03%). Preheat the insert to 140°C before injection. Cooling time ranges from 40 to 150 seconds.
4. Secondary processing technology in fluoroplastics
Some products may not be possible to form due to their processing characteristics. They must therefore be processed two times to make them usable. Second processing options include welding, cutting, lining, inflation and others.
Lathes, drill machines and planers are all used to cut metal. It is important to wait 24 hours for the body to be ready before you start cutting.
You can choose between hot-press or hot-air welding. You can rely on hot-press welding if it is heated to 327°C in special pliers. It can also be welded under high pressure.
PFA links PFA welds hot air welding rod to two pieces of metal under heat or pressure.
Lining: Most PTFE (written F4 or F46) are lined by ferrous metal pipe and fittings. This allows for corrosion and chemical resistance.
Inflation is a group of products that includes bellows as well shrinkable heat tube and heat-shrinkable material. This is broken down into two types: continuous and intermittent inflation.
Example: The F46 heat-shrinkable tube tube blank can be prepared using water-cooled vacuum setting. Also, there are F4 spiral tubes that can be blown.
PTFE machine-tool guide soft belt: Use suspension PTFE fine particle, crush, then pass through 20 mesh sieve. After crushing for five minutes, pressurize for 100 mmh rough for five minutes. Then, inflate the material three times at the center, and sinter. It should be warmed to 80°C before turning it. Then, heat preservation is done. Use sodium naphthalene to treat the soft tape. These include 51 g of sodium naphthalene; 100 ml tetrahydrofuran; a suitable amount of sodium metal and soft tape. After soaking the solution in sodium naphthalene (1-3 minutes), wash with hot water, at 90° C.
PTFE is a versatile material that can be used to make polyphenylene and polyimide. It also has the ability to be combined with molybdenum diulphide, graphite or bronze powder. Fluoroplastic 46 may be used to make corrosion-resistant valves. The molding temperature ranges from 320-335F, with a moulding pressure of 3-30MPa. Also, the setting temperature can be set at 120-175 F.
For reducing corrosion, the inner liner for the steel pipes is glass-fibre reinforced PTFE pipe. It is this:
PTFE resin: Mashed, sieved – Die-pressed molding – Sintering.
To make a polyvinylidenefluoride sealing ring, add one part of the acid absorber. After the template temperature has reached 195-250 degrees, slow pressurize it to 2.5-3 MPa. Once the mold temperature has reached 180-190°C, the cold press is used to quickly cool the product to 14MPa. At 50°C, it is removed and trimmed. Then, the mould can be placed into an oven at 130°C. You can inspect the packaging after it has been heated for 24 hours.
For optical communication, the fluorinated epoxy is a fluorinated resin that has been formulated from various fluoroplastics. For semiconducting device, perfluoro chemicals and thermoplastic fluoroelastomers for medical treatment. For high- and lower-temperature grease, there are perfluoropolymers Ether. Polyvinyl Fluoride can also be solvent-free processed. You only need nine parts of oil, four parts heat stabilizers and two pieces of additional additives.
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