Effects of monomer and oligomer content in polyamide 6 pellets on their properties
Monomers and oligomers from polyamide 6(PA6)were extracted by dissolution/precipitation method,a combination of liquid chromatography/time flight mass spectrometry/photodiode array detector(LC-TOF-MS-PDA)and a polymer chromatography/multi-angle laser-light-scattering/refractive index detector(APC-MALLS-RID)was used to measure the monomer and oligomer content and oligomer composition of PA6,PA6 molecular weight and its distribution in PA6.The effects of the monomer and oligomer content on the thermal and crystallization properties of PA6 pellets were analyzed by thermogravimetric analyzer,differential scanning calorimeter and two-dimensional wide-angle X-ray diffractometer.The results indicate that the monomer and cyclic oligomer contents in physically recycled PA6(pr-PA6)and chemically recycled PA6(cr-PA6)pellets were 2.079％and 1.578％,respectively,0.683％and 0.182％higher than those in the original PA6(PA6)pellets,while the monomer,cyclic dimer and cyclic trimer contents in the recycled PA6 pellets were higher than those of the original PA6 pellets.The molecular weights of PA6,pr-PA6 and cr-PA6 were 19620 g/mol,20840 g/mol and 22210 g/mol,respectively,with the molecular weight distribution coefficients of PA6,pr-PA6 and cr-PA6 being 1.47,1.56 and 1.49,respectively.The maximum decomposition temperatures of the three PA6 pellets did not change significantly.Compared with the original PA6 pellets,the crystallization peak temperature of regenerated PA6 pellets shifted to the high temperature region,and the crystallization temperature increased from 176 ℃ for PA6 to 185 ℃ for pr-PA6,and the relative content of a crystalline forms in pr-PA6 and cr-PA6 pellets increased.This study can provide a theoretical basis for improving the thermal and crystallization properties of PA6 materials.
PA6 pelletsmonomersoligomersliquid chromatography/time flight mass spectrometry/photodiode array detector(LC-TOF-MS-PDA)crystallization
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