Research on Polyethylene Oxide Modified Polyformaldehyde
|School||Northeast University of Petroleum|
|Keywords||Polyoxymethylene Poly oxide ethylene crystallize heat treatment|
Polyoxymethylene (POM) is a kind of high crystalline linear chain thermoplastic polymer. Its regular conformation causes POM to crystallize easily and to get large spherical crystals and high crystallinity (60～80%) in the melting process. POM is widely used in machinery, electronics, automotive, instrumentation and other fields because that it owned of self-lubricating, wear-resistance and excellent mechanical properties. However, its applications are highly limited because of poor impact strength and low thermo-degradation temperature. At present thermoplastic polyurethane elastomer (TPU) is primarily used to modify POM. POM modified by adding TPU has lower rigid and wear performance, crystallization instability. Therefore, in this thesis, we added thermo-stabilizers to POM, and then the toughness properties of POM were modified by Polyethylene Oxide (PEO) to resolve these two problems.The effects of thermo-stabilizers systems in the compounded POM were studied in order to improve to poor thermal stability of POM by using of balance torque, isothermal weight loss analysis and isothermal weight loss rate analysis. The results showed, when the contents of the antioxidant was0.3wt%(main antioxidant245/assistant antioxidant168=4) and content of triethanolamine was0.1%, the best thermal stability was obtained.Small amount of PEO was added into POM. Crystallizing process of POM is affected by crystalline state of PEO. The influence of molecular weight and content of PEO on the crystallization behavior and properties of POM were studied by means of differential scanning calorimeter (DSC)、wide angle X-ray diffraction (WAXD)、polarized light microscopy (PLM)、mechanical properties test、balance torque and melt index test. The results showed that PEO did not change the nucleating way of POM in POM/PEO blends, the spherulites became larger. When increasing PEO content or molecular weight, PEO crystallized and PEO penetrated in the spherulites of POM. The impact strength of POM/PEO blends were increased with the addition of PEO. when the composition was POM/PEO=95/5, POM/PEO blends got the maximum impact strength, further increasing of PEO content resulted a slight weakening of their impact strength, but it was always higher than that of pure POM; Meanwhile, the balance torque became larger and MFR became smaller with increasing the content of PEO, because there was a intermolecular force in POM and PEO.Heat treatment methods on crystallization behaviors and mechanical properties of POM/PEO blends in processing machinery were studied. It was showed that the blends were treated for2hours at crystallization temperature of POM, and then2hours at crystallization temperature of PEO. POM had crystallinity well and PEO did not have crystallinity in POM/PEO blends. Because POM and PEO had stronger force, the energy can be absorted and toughness can be increased.