Performance | Homopolymerized POM | Copolymerized POM | 25%GF POM |
Relative Density | 1.43 | 1.41 | 1.61 |
Water Absorption/% | 0.25 | 0.21 | – |
Molding Shrinkage/% | 1.5~3 | 1.5~3.5 | – |
Tensile strength/MPa | 70 | 62 | 130 |
Elongation at Break/% | 40 | 60 | – |
Tensile Modulus/MPa | 3160 | 2830 | 8300 |
Bending Strength/MPa | 90 | 98 | 182 |
Flexural Modulus/MPa | 2880 | 2600 | 7600 |
Compressive Strength/MPa | 127 | 110 | – |
Shear Strength/MPa | 67 | 54 | – |
Notched Impact Strength/(J/m) | 76 | 65 | 86 |
Rockwell Hardness | M94 | M80 | – |
Friction Factor | – | 0.15 | – |
Fatigue Limit/MPa | 35 | 31 | – |
Heat Distortion Temperature (1.82MPa)/℃ | 110 | 124 | 163 |
Long-term Use Temperature/℃ | 80 | 100 | – |
Linear Expansion Coefficient/(X10-5K-1) | 7.5 | 8.5 | 2.6 |
Thermal Conductivity/[W/(m·K)] | 0.23 | 0.23 | – |
Volume Resistivity/Ω·cm | 1015 | 1015 | 3.8X1014 |
Dielectric Constant(106Hz) | 3.8 | 2.7 | – |
Dielectric Loss Tangent(106Hz) | 0.005 | 0.007 | – |
Dielectric Strength/(kV/mm) | 20 | 20 | – |
Arc Resistance/s | 220 | 240 | – |
(1) General performance
The appearance of POM is light yellow or white translucent or opaque powder or pellets, hard and dense, similar to ivory, the surface of the product is smooth and shiny, and the molding shrinkage rate can reach up to 3.5%. POM is flammable, its oxygen index is only 14%-16%, the upper end of the flame is yellow and the lower end is blue, similar to the flame of PP, there are molten drops when burning, and it has a pungent formaldehyde and fishy smell. The air permeability of POM is small, only a fraction of that of PE.
(2) Mechanical properties
The mechanical properties of POM are excellent, the specific strength can reach 50.5MPa, and the specific stiffness can reach 2650MPa, which is very close to metal. The mechanical properties of POM change slightly with temperature, and the change of copolymerized POM is slightly larger than that of homopolymerized POM. The impact strength of POM is higher, but the conventional impact is not as good as that of ABS and PC; POM is sensitive to the gap, and the impact strength can be reduced by as much as 90% if there is a gap. The fatigue strength of POM is very prominent. After 104 alternating loads, the fatigue strength can reach 35MPa, while PA and PC are only 28MPa. The creep resistance of POM is similar to that of PA, which is only 2.3% at 20°C, 21MPa, and 3000h, and is little affected by temperature. POM has small friction coefficient, good wear resistance (POM>PA66>PA6>ABS>HPVC>PS>PC), high limit PV value, good self-lubrication, and is suitable for the production of frictional products such as gears and bearings. However, when POM products are rubbed against each other, it is easy to produce squealing noise under high load.
(3) thermal properties
The long-term heat resistance of POM is not high, but it can reach 160°C in the short term. The short-term heat resistance of homopolymerized POM is more than 10°C higher than that of copolymerized POM, but the long-term heat resistance of copolymerized POM is about 10°C higher than that of homopolymerized POM.
(4) Electrical properties
POM has good electrical insulation and is hardly affected by temperature and humidity; the dielectric constant and dielectric loss change little in a wide range of temperature, humidity and frequency; it has excellent arc resistance and can be used at high temperatures. Keep. The dielectric strength of POM is related to the thickness, which is 82.7kV/mm when the thickness is 0.127mm, and 23.6kV/mm when the thickness is 1.88mm.
(5) Environmental performance
POM is not resistant to strong acids and oxidants, and has certain stability to dilute acids and weak acids. POM has good solvent resistance, can resist hydrocarbons, alcohols, aldehydes, ethers, gasoline, lubricating oil and weak alkali, etc., and can maintain considerable chemical stability at high temperatures.
The weather resistance of POM is not good. Under the action of ultraviolet light for a long time, the mechanical properties will decrease and the surface will be chalked and cracked.
