1. State Key Laboratory of Polymer Physics and Chemistry, Joint Laboratory of Polymer Science and Materials, Beijing NationalLaboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China 2. State Key Laboratory of Rare Earth Material Chemistry and Application，College of Chemistry and Molecular Engineering, Peking University，Beijing 100871, China 3. Key Lab of Organosilicon Chemistry and Matorial Technology Ministry of Education, Hangzhou Normal University, Hangzhou 310012, China 4. Graduate School of Chinese Academy of Sciences, Beijing 100039, China
Abstract：Temperature-dependent FT IR, DSC and POM were used to investigate the interaction between PVPK90 and nylon 6 molecules and its effect on the thermal behavior and morphology of nylon 6. DSC results suggest that the melting and crystallization behavior of nylon 6 are obviously influenced by the introduction of PVP. With the PVP content increasing, the crystallization temperature, melting temperature and the crystallinity of nylon 6 decreased, and eventually, both the exothermal and endothermic peaks could not be observed when the PVP content reached 80%, implying that the aggregation structure of nylon 6 changes from the crystalline state to the amorphous state. FTIR provided the evidence of the interaction between PVP and nylon 6 molecules. With the increase in PVP content, the peak position of νN—H of nylon 6 gradually shifts from 3 311 to 3 300 cm-1 with 90% content of PVP, and the half height peak width is broadened correspondingly. Three peaks were obtained in the carbonyl group absorption band for PVPK90/Nylon 6(50/50) and PVPK90/Nylon 6(80/20) blends from the curve-fitting results. With the addition of PVP molecules, the νCO of nylon 6 shifts to higher wave number and a new peak located at about 1 620 cm-1 appears and its peak area increases with the content of PVP. The above spectral variation of νCO and νN—H in the PVPK90/Nylon 6 blend indicates that the carbonyl group of PVP could form H-bonding with N—H group of nylon 6 molecule, and partially destroy the hydrogen bonding between the nylon 6 molecules. POM results showed that the spherulitic size of nylon 6 decreases with the increment of the PVP and becomes more imperfect, and when the PVP content reaches 80%, no spherulites could be observed. This phenomenon is attributed to the molecular interactions between the PVP and the nylon 6 molecules, which weakens the free mobility of nylon 6 chains to form regular packing and eventually induces the change in the spherulitic morphology of nylon 6. In summary, the molecular interactions between the carbonyl group of PVP molecules and N—H group of nylon 6 molecules account for the above changes in the crystalline structure and the morphology of nylon 6 in the blends.
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