Evaluation of Relationship Between Crystallization Structure and Thermal‐Mechanical Performance of PLA with MCC Addition

Abstract

Poly(lactic acid) (PLA) biocomposite with 1 wt % microcrystalline cellulose (MCC) addition were prepared by melt-mixed method using torque rheometer and annealed under different isothermal conditions. The morphology, crystallization behaviors, thermal and dynamic-mechanical properties were evaluated by techniques of polarized optical microscopy (POM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and dynamic mechanical analysis (DMA). Nucleus density, crystallization rate and crystallinity (X c ) of PLA matrix were significantly increased by addition of MCC. It was found that MCC could improve the activity of PLA segments at low crystallization temperature (T c ), and the stability of segments in crystal lattice was also enhanced at high T c . DSC and XRD analysis supported that MCC contributed to the transformation of α' form into α form in PLA during annealing. The temperature range in which α crystal form appeared for pure PLA was 125 to 135°C and it was enlarged from 105 to 145°C for PLA with MCC addition. The Avrami exponent (n) and crystallization rate constant (k) for MCC/PLA decreased and increased respectively, supporting that the time dimension in nucleation mode was inhibited and crystallization kinetics was improved. MCC/PLA showed an increased stiffness and the highest value of storage modulus (E') was 52 GPa at T c of 125°C, which is basically consistent with the condition of maximum X c . DMA analysis supported that at high T c , the addition of MCC greatly increased the crystallization ability of PLA and the elasticity and toughness were also improved.[a] Dr.

Crystallization of Polylactic Acid with Organic Nucleating Agents under Quiescent Conditions

“…The Avrami index for all tested samples was between 1.7 and 2.4, indicating that major crystalline structures were either disc-shaped crystals or spherulites. This observation is also supported by other research [30,56] and following SEM imaging analysis.…”

Bio-composites for fused filament fabrication: effects of maleic anhydride grafting on poly(lactic acid) and microcellulose

“…Micro cellulose and nanocellulose have been promising evaluated as reinforcing filler for various composites [32]. Specific composition in PLA have been produced either by solution casting up to 20% of nanocellulose [33], or by melt compounding with 5% of nanocellulose crystals [34] and with 1% of microcrystalline cellulose [35]. Moreover, some researchers recently suggested the application of cellulose based composite for 3D printing [9,36].…”