Abstract:
Polybutyrolactam (PA4) was thermoplastic modified by melt blending extrusion with lithium chloride (LiCl) as the plasticizer. The thermodynamic, crystalline and mechanical properties of LiCl plasticized PA4(LiCl/PA4) were investigated by means of differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and tensile test. XPS results showed that the O atom binding energy of unplasticized PA4 was 531.40 eV. Compared with the unplasticized sample, the binding energy of O atom in LiCl/PA4 system increased by 0.25 eV, while that of N atom was almost unchanged. Therefore, Li
+ was mainly complexed with oxygen rather than N atomin in amide bond. Such complexation destroyed the intermolecular hydrogen bonds of PA4 and restrained the crystallization. With the increment of LiCl content, the melting point and crystallinity of PA4 gradually decreased. When
m(LiCl)∶
m(PA4) was 5%, the melting point of LiCl/PA4 decreased to 223.9 ℃ and was 41.6 ℃ lower than that of unplasticized sample. Meanwhile, the crystallinity of plasticized PA4 decreased to 37.88%. In addition, LiCl/PA4 still maintained good mechanical properties. The elongation at break of LiCl/PA4 increased with the addition of LiCl. The maximum elongation at break of LiCl/PA4 was 233% when
m(LiCl)∶
m(PA4) was 5%, which increased by 155% compared with that of the unplasticized sample. The tensile strength of plasticized PA4 was higher than that of the unplasticized sample, which increased first and then decreased with the increment of LiCl content. The maximum tensile strength reached 57.90 MPa when
m(LiCl)∶
m(PA4) was 1%.