PTFE, PFA, FEP, PVDF Fluoroplastic products industry experts
Raw materials for PTFE products
Classification:
Industry dynamics
Author:
PFA tube little sister
Source:
Dankai
Release time:
2022-11-26
Visits:
Imported brands of PTFE raw materials generally include DuPont, 3M, Daikin, Juhua, etc., while domestic materials mainly include three farmers, Dongyue and so on. PTFE suspension resin due to its extremely high melt viscosity to melt also does not flow
Only about 25% of the volume expansion occurs and melts together, and the melt is easily broken under the action of shear force. Therefore, the molding process of PTFE suspension resin is first cold pressed into a preform, burned
Knots and cools into products with a certain strength. Then the secondary processing, become the final product.
Figure 1: PTFE raw material source: Dankai
Physical performance indicators related to processing
Particle size: The average particle size of PTFE suspension resin is roughly divided into 50 ~ 60µm and 400 ~ 500µm. The former is fine and easy to be compacted, can obtain less voids, denser molded products, but its material.
The fluidity of the material is poor, and the resin in the mold cavity must be evenly distributed during operation; the latter has large particle size, coarse particles, automatic flow characteristics, suitable for automatic molding, hydraulic molding and plunger extrusion molding,
However, the compactness of its products is poor and the electrical insulation performance is poor.
Shape: Irregular particle shape is easy to compact.
Hardness: Soft and fine resin powder is easy to compact.
The apparent density of the suspended resin is 0.43 to 0.45g/cm3, and the apparent density of the preform after pressing is 1.85 to 1.90g/cm3. The melt density after sintering is 1.46 to 1.48g/cm3.
The density after cooling was 2.15 to 2.17g/cm3.
Compression ratio is generally 4~5,
porosity,
The shrinkage rate is generally 3% to 4%.
PTFE molding methods are: molding, hydraulic molding, automatic molding, plunger extrusion molding, molding, feeding compression.
The PTFE suspension resin that has been sieved and placed at 25°C for 24h can be loaded into the mold cavity and pressed into a preform in an environment of 25°C and 30°C. During compression, 23 times of bleeding are required. Increase the temperature
to reduce the pressure. Excessive pressure will produce greater elastic deformation and anti-cracking of the product, and appropriate increase in pressure can reduce porosity and shrinkage. Before sintering, it is necessary to exhaust the empty space in the preform as much as possible.
Gas, so there is parking time, this time is related to the wall thickness.
Sintered. The pressed PTFE preform has only the raw strength due to the accumulation between the resin particles. When the temperature rises to 342 ° C. or higher, the PTFE crystal phase disappears and becomes amorphous. 360°C to 380°C
When the PTFE particles are expanded and fused, the pores between the particles are eliminated. If the holding time is too long, the molecular chain will degrade and reduce the strength of the product. Sintering due to poor thermal conductivity of PTFE resin, so
There is a large temperature difference along the wall thickness of the preform, so it is necessary to keep the temperature for a period of time to make the temperature uniform. The longer the time, the better the compactness. Cooling. The slower the cooling rate, the higher the crystallinity. Annealing
It can reduce the temperature difference and avoid stress cracking of thick-walled products. Quenching can reduce the crystallinity, make the product soft and improve the bending fatigue life, but it can only be used for products with a wall thickness of no more than 5mm.
This article is originally created by Teflon's little sister. Welcome to pay attention and take you to grow knowledge together!
Key words:
Raw materials, molding, ptfe, resin, products, suspension, molding, density, granules
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