Investigation on effect of PVP on morphological changes and crystallization behavior of nylon 6 in PVP/Nylon 6 blends by FTIR spectroscopy

Temperature-dependent FF 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 result 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 VN-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 v (C=O) 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 v (C=O) and VN 11 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 imperfecti 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.