In the present work, a lignin nanoparticle grafted on a PLLA copolymer (LNP-g-PLLA) was prepared via ring-open polymerization with L-lactide as the raw material and −OH of lignin as the initiator. Then, PDLA/PLLA-g-nanolignin composite films with various quantities of LNP-g-PLLA were fabricated by a solvent casting method. Results from differential scanning calorimetry and wide-angle X-ray diffraction evidenced the formation of SC at the interface between PDLA and the LNP-g-PLLA copolymer, which was helpful to improve the heat resistance. Dynamic mechanical analysis showed that the storage moduli of the PDLA/15g-LNP composite sample are 547 and 264 MPa at 80 and 140 °C, respectively, while they are only 12 and 4 MPa for pure PDLA. The tensile test results illustrated a significant improvement in the mechanical performance, which was supposed to be attributed to the interfacial compatibility between PDLA and the LNP-g-PLLA copolymer, resulting in the enhancement of the HC crystallization of PDLA. Furthermore, PDLA/PLLA-g-nanolignin composite films were found to have excellent UV resistance due to the inherent UV shielding property of lignin nanoparticles. When the LNP-g-PLLA amount was 9.0 wt %, the PDLA/9g-LNP film shielded nearly 100 wt % of UV-B irradiation, while only quite limited UV-A irradiation was transmitted. The excellent heat resistance and UV shielding properties endow the composite films with great potential application in some heatable and UV shielding packaging.
Casting infiltration technology was used to fabricate a high-chromium coating on the surface of parent ZG45 steel with different Ni content. SEM, EDS analysis, CALPHAD-type calculations, Rockwell hardness test and impact wear test were utilized to investigate the influence of Ni on the microstructure, hardness and impact wear resistance performance. The as-cast microstructure of the casting infiltration coatings with Ni content less than 2.82 wt.% was a pearlite matrix with reticular eutectic M7C3 carbide, while the matrix of the coatings with 5.53 wt.% Ni showed austenite. The content of Ni had little effect on both the solidification behavior and the amount of eutectic M7C3. After heat treatment, the transformation of the matrix to martensite occurred, and the Rockwell hardness significantly increased. The proportion of the retained austenite in the casting infiltration coatings increased from 6.4 vol.% to 27.5 vol.% with increasing Ni content, resulting in a decrease in the hardness. Due to a better balance of the hardness and toughness, the casting infiltration coating with 1.53 wt.% Ni showed the best impact wear resistance performance.
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