Effect of MgO whiskers on thermal behavior and mechanical properties of injection molded poly(L‐lactide)

Abstract

Poly(L‐lactide) (PLLA) composites containing various content of MgO whiskers (MgO‐Ws) and surface grafted MgO whiskers (g‐MgO‐Ws) were prepared by injection molding technique. The g‐MgO‐Ws showed better dispersion in the matrix and improved interface compatibility with the matrix compared with the MgO‐Ws, which was confirmed by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The results of differential scanning calorimeter (DSC) and polarized optical microscopy (POM) of the MgO‐Ws/PLLA and g‐MgO‐Ws/PLLA composites revealed that the crystallization rate and crystallinity of PLLA were improved by the introduction of MgO‐Ws and g‐MgO‐Ws, but the thermogravimetric measurements showed that the thermal stability of the PLLA matrix decreased by the addition of the whiskers. The tensile, flexural, and impact properties of the resulting composites were systematically studied, and the g‐MgO‐Ws/PLLA composite exhibited remarkably higher tensile strength, modulus, and toughness than those of the pure PLLA and MgO‐Ws/PLLA composite. The highest tensile strength of 62.9 ± 3.2 MPa, tensile modulus of 1,222.3 ± 25.2 MPa, and fracture energy of 459.1 ± 24.3 J/m2 were obtained for the g‐MgO‐Ws/PLLA composite with 2.5% whiskers content, which were 30.8%, 13.7%, and 105.5% higher than those of PLLA matrix, respectively. Loading the whiskers with appropriate content can also improve the flexural and impact properties of the PLLA matrix. The highest impact strength, flexural modulus, and flexural strength were obtained for the g‐MgO‐Ws/PLLA composite with 1% whiskers content. POLYM. COMPOS., 39:E1807–E1820, 2018. © 2018 Society of Plastics Engineers

In vitro degradation of self‐reinforced poly(lactic acid) with beta‐tricalcium phosphate composite prepared by equal channel angular pressing

“…In the previous study, various self‐reinforcement methods such as forging, solid‐state extrusion, die drawing, and injection molding have been developed for improving mechanical properties of polymers. [ 16–19 ] Contrary to some traditional reinforcement techniques (such as forging and die drawing) involving continuous specimen cross‐sectional reduction, the equal channel angular pressing (ECAP) method can keep the cross section of the sample unchanged, so as to perform multiple extrusions and produce large plastic deformation in the specimen. [ 20 ] The ECAP has been applied to several thermoplastic polymers such as polycarbonate, polytetrafluorethylene, high‐density polyethylene, polypropylene, polyoxymethylene, and glass fiber/polyacetal.…”