PVP对Nylon 6形貌及结晶行为影响的研究

采用变温红外光谱、示差扫描量热（DSC）和偏光显微镜（POM）等方法研究了聚乙烯吡咯烷酮（PVP）与尼龙6（nylon 6）分子间的相互作用及其对nylon 6热行为及结晶形貌的影响。DSC结果表明PVP的加入明显影响了nylon 6的熔融和结晶行为：随着PVP含量增加，PVP/nylon 6共混物的结晶温度、熔融温度及结晶度均逐渐降低；POM观察显示：随着PVP含量增多，nylon 6的球晶尺寸变小、球晶逐渐变得不完善。变温红外光谱结果表明，无定形PVP分子的羰基能够与nylon 6分子的N—H基团形成新的氢键，部分破坏了nylon 6分子之间的氢键结构，从而阻碍了nylon 6分子的规整排列，使其结晶度降低并导致nylon 6结晶形貌的变化。

Investigation on Effect of PVP on Morphological Changes and Crystallization Behavior of Nylon 6 in PVP/Nylon 6 Blends by FTIR Spectroscopy

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 ν_N—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 ν_CO 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 ν_CO and ν_N—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.