what is the difference between ETFE and PVDF?

ETFE and PVDF belong to the same fluorine resin, they have similar structure, so what are the similarities and differences?

Performance comparison

Appearance properties: PVDF and ETFE are not much different in appearance properties, ETFE is generally translucent particles or white powder, PVDF is generally translucent or white powder or particles.

Melting point: the high degree of alternation of molecular structure makes ETFE has high molecular rigidity and crystallinity, its glass transition temperature, melting point are higher than PVDF. PVDF melting point is generally between 150 ℃ ~ 185 ℃, while most of the melting point of the pure resin of ETFE is between 260 ~ 280 ℃, the high degree of alternation of the melting point of the ETFE resin can be up to 310 ℃.

Glass transition temperature: the high degree of alternation of molecular structure makes ETFE have high molecular rigidity and crystallinity, and its glass transition temperature is higher than that of PVDF.

Thermal stability: PVDF and ETFE will decompose at higher temperatures, the difference between the two decomposition temperature is about 40 ° C. ETFE will decompose at 340 ° C or more, the main product is oligomer, PVDF will decompose at 300 ° C or more, the decomposition product is mainly HF, fluorine-carbon organic compounds, and so on.

Long-term use temperature: ETFE long-term use temperature of -70 ~ 150 ℃, lower than most of the fluorine resin (PTFE, FEP, etc.), PVDF long-term use temperature between -40 ℃ ~ 150 ℃.

Flame retardant: PVDF and ETFE are non-combustible in air, but PVDF has better flame retardant than ETFE, and the ultimate oxygen index of PVDF is 44, while that of ETFE is 30~31.

Solubility: At room temperature, PVDF can be dissolved in polar organic solvents such as acetone, tetrahydrofuran and many esters, while ETFE is only dissolved in a few solvents (e.g. diisobutyl adipate) at a higher temperature.

Dielectric properties: ETFE is a good dielectric material, dielectric constant is relatively low, basically unaffected by frequency, between 2.5-2.6, in 10GHz frequency dielectric constant is still close to 2.3, dielectric loss is very low, but will increase with the rise in frequency, PVDF dielectric constant is relatively high, can reach 6 ~ 8, dielectric loss angle tangent is also relatively large, in the range of 0.04 ~ 0.2 Between, volume resistivity is low, with piezoelectricity and thermoelectricity.

Mechanical properties: PVDF at a certain temperature and pressure can still maintain good strength, high tensile strength, good impact resistance, good toughness, hardness, abrasion resistance is particularly good, creep resistance is one of the best of the fluorine resin; ETFE is the most tough fluorine plastics, mechanical toughness, modulus, tensile strength, creep resistance is better than PTFE, FEP, PFA, creep resistance due to FEP and PTFE, room temperature at the same time, the resistance to creep is better than FEP, FEP and PTFE. and PTFE, the tensile strength at room temperature can reach 46MPa, tensile strength at break can reach 300%, overall ETFE impact strength and elongation is higher than PVDF.

Comparison of application areas

Due to the nature of the differences, PVDF and ETFE application areas are different. ETFE, PVDF can be used in construction, energy, chemical, electronics, pharmaceutical, food and other industries.

Typical applications for ETFE are in construction and wire and cable. Compared with glass and other common transparent building materials, ETFE film has a higher light transmittance, thinner thickness, better deformation absorption capacity and stronger impact resistance and self-cleaning ability, so that its application in the field of building roofs and walls continue to expand the scene; ETFE superior overall performance, but the long-term use of the temperature is only 150 ℃, in the high-speed electronic irradiation, the ETFE molecules can be formed to cross-linking, high temperature, mechanical properties greatly improved, continuous use temperature of 150 ℃, the ETFE film can be used for the construction of the building. Mechanical properties significantly improve the continuous use of temperature up to 200 ℃, but also very light, the density is significantly smaller than PTFE, PFA and FEP, coupled with the higher strength of X-ETFE, its insulation thickness can be appropriately reduced a little so that compared to other materials in the same quality, the weight of the cable is much lighter than the same product, so X-ETFE in wire and cable is widely used.

The most prominent application of PVDF is in the field of lithium batteries and coatings. As PVDF has excellent chemical stability and corrosion resistance, it can effectively resist the erosion of polar organic solvent electrolyte, and at the same time, it has good bonding properties, so it is widely used in lithium battery positive binder, and there is no suitable alternative, and currently accounts for up to 90% of the total; coatings is the second largest application area of PVDF, the coatings made of PVDF are resistant to oxidation and optical degradation, and do not fade, can be Withstand air, water, mold, acid and alkali, salt spray and other erosion, service life of more than 30 years, without maintenance, has a high cost-effective, is the ideal decorative material for the exterior walls of buildings, roofs and a variety of building materials.