The study on microstructure and mechanical properties of multi-component composite based on HDPE.

The basalt fiber (BF) and polyamide 6 (PA6) reinforced HDPE composite were prepared; the effects of adding fiber, organic filler, and polar component maleic anhydride (MA) on the microstructural characteristics of composites were investigated. Microstructural characterization evidenced the binary-dispersed phase (PA6/BF) is of a core-shell structure in which the component PA6 encapsulates component BF, and the extent of encapsulates would decline with the MA adding. It is confirmed that the microstructure is related to the interfacial tension of components by the SEM observation and theoretical calculation. The effect of multi-component on the crystallization behavior of composites was investigated. Differential scanning calorimeter (DSC) analyses showed a significant change in the HDPE microstructure. It demonstrated PA6 and BF as a nucleation agent accelerated the crystallization rate under the cooling process. The corresponding crystallization kinetics and activation energy were further analyzed using the Jeziorny method, Avrami-Ozawa method, Kissinger method. The results showed MA markedly changed the crystal growth mechanism of the HDPE matrix to heterogeneous nucleation for acicular and tabular crystal growth during the annealing step. The lowest crystallinity energy and crystallinity were observed for BF/PA6/HDPE composites with 3 wt % MA. Furthermore, a clear improvement of mechanical properties (by 61%) were observed, which mechanism is discussed in detail. The mechanism of toughening is not only one, but the result of a variety of mechanisms together.