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摘要
Scanning probe thermal analysis was utilized to investigate poly(L-lactic acid) (PLA)/exfoliated graphite nanoplatelets (xGnP (TM)) nanocomposites. The technique was employed together with conventional thermomechanical analyses to offer insight on the effect of xGnP on the crystallization behavior of PLA, and to explore the relationship between the polymer's molecular weight and the dispersion of xGnP in the matrix. Specifically, the technique was used to monitor cold crystallization phenomena, and to assess the dispersion of nano-sized fillers in the polymer matrix. Exfoliated graphite nanoplatelets having an average diameter of 1 mu m (xGnP-1) were shown to nucleate PLA, affecting both the cold crystallization and the crystallization from the melt of the polymer. Dynamic mechanical analysis (DMA) revealed that xGnP-1 have a reinforcing effect on PLA, leading to composites with improved mechanical properties. The reinforcing effect of xGnP-1 appeared to be dependent on the molecular weight of the polymer matrix. The same amount of xGnP-1 led to composites with higher modulus (up to 60% improvement for 3% wt xGnP-1) when incorporated into higher molecular weight PLA, and did not generate significant improvement in the case of a lower molecular weight matrix. Differences in the dispersion of xGnP-1 in the polymer matrices were suspected to be the essential cause for the differences in composites' properties. Differential scanning calorimetry (DSC) revealed differences in the crystallization behavior depending on the molecular weight of PLA, but the results of this classical thermal analysis method could not be directly related to polymer's morphology and to the dispersion of xGnP. Scanning probe thermal analysis measurements successfully detected different cold crystallization behavior of PLA in the presence of xGnP, depending on the molecular weight of the polymer.
- 出版日期2008-3
