Preparation and properties of POM / PTFE
DATE：2021/6/25 9:03:02 / READ： / SOURCE：This station
Preparation and properties of POM / PTFE
The wear resistance of POM can be greatly improved by blending polytetrafluoroethylene (PTFE) with POM, and self-lubricating materials can be prepared. The surface free energy of PTFE is very low, so it is difficult to be compatible with POM. This will lead to poor interfacial adhesion of POM / PTFE blends, easy to occur macro phase separation, and directly affect the polymer properties. Moreover, PTFE particles are easy to agglomerate, and it is difficult to disperse uniformly in high viscosity POM melt by screw extruder alone. Therefore, special surface treatment must be carried out on PTFE to improve its compatibility with OM. There are chemical treatment and physical treatment. Tetrahydrofuran (THF) sodium solution is a better method for chemical treatment of PTFE. Weigh a certain amount of pre dried Pt Fe suspension fine powder, completely immerse it in the frozen THF sodium naphthalene solution for 3 ~ 5min, wash it with acetone for 2 ~ times after the reaction, pump and filter it, and put it into 70 ~ 80 ℃ vacuum oven to dry to constant weight. Poe special embossing film production line www.handern.comThe treated PTFE changed the surface characteristics of PTFE, the solubility parameters were close to that of POM, and showed good compatibility with POM. However, due to the great difference of melting temperature between PTFE and POM, the melt blending of PTFE and POM is essentially a process of dispersion of solid particles of PTFE in POM. Therefore, the mechanical properties of POM blends with treated PTFE decrease greatly. The mechanical properties of POM / treated PTFE alloy are listed and compared with those of POM / PTFE and pure POM. It can be seen that the tensile strength and bending strength of POM / PTFE alloy are lower than that of POM, but the decrease of POM / PTFE alloy is smaller than that of POM / PTFE alloy. This is because NaF is produced during the surface treatment of PTFE, and NaF is adsorbed on the surface of PTFE. When treated PTFE and POM were blended, NaF acted as a coupling agent to increase the compatibility of treated PTFE and POM; At the same time, PTFE particles are soft and the specific surface area is increased after air flow crushing, so the dispersion in POM melt is more uniform. Poe special embossing film production line www.handern.com
When the content of PTFE is 10%, the mechanical properties of the alloy are the best. The reason is that NaF adsorbed on the surface of treated PTFE acts as a coupling agent between POM and the segments of treated PTFE, which improves the two-phase binding force. If the amount of PTFE is too small, the coupling effect of NaF is too weak; If the amount of PTFE is too much, the mechanical properties of the alloy will decrease with the increase of the amount of PTFE. Poe special embossing film production line www.handern.com
The friction coefficient and wear loss of POM / treated PTFE blends were compared with those of POM and POM / PTFE. The results showed that the friction coefficient and wear loss of POM / treated PTFE blends decreased after adding PTFE to POM, which was due to the formation of PTFE transfer film in the friction process, which effectively reduced the friction coefficient and wear loss of POM / PTFE blends. The friction coefficient of POM / PTFE alloy is smaller than that of POM / PTFE alloy, which is due to the better dispersion effect of treated PTFE in POM and the easier formation of transfer film in the friction process. The wear resistance of POM / PTFE alloy is obviously better than that of POM / PTFE alloy, which is due to the weak adhesion between POM and PTFE, and the PTFE film is easy to fall off. However, the affinity between PTFE and POM is good, and the binding force between the two phases is strong. Poe special embossing film production line www.handern.com
The friction coefficient of the alloy decreases with the increase of PTFE content. When the PTFE content is less than 10%, the friction coefficient decreases rapidly; When the content of PTFE is more than 20%, the friction coefficient of the material is basically unchanged. With the addition of treated PTFE, the friction coefficient of the material is reduced. The formation rate of PTFE transfer film is related to the content of PTFE. When the PTFE content is 10% ~ 20%, the transfer film becomes more and more complete and the friction coefficient decreases slowly with the increase of PTFE content; When the PTFE content exceeds 20%, the friction coefficient remains unchanged. When the PTFE content is less than 20%, the wear loss decreases with the increase of PTFE content; When the content of treated PTFE is more than 20%, the wear loss of the alloy increases with the increase of treated PTFE. This is due to the acceleration of the transfer film formation rate to the dual (friction parts are steel) surface. Considering the mechanical properties and economic benefits, the best content of PTFE is 10% (the price of PTFE is much higher than POM). Poe special embossing film production line www.handern.com
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