Evaluation of Relationship Between Crystallization Structure and Thermal‐Mechanical Performance of PLA with MCC Addition. Issue 34 (12th September 2019)

• Record Type: Journal Article
• Authors: Wen, Huiying; Wang, Yali; Wang, Di; de Claville Christiansen, Jesper; Yu, Donghong; Jiang, Shichun; Chen, Chunxia
• Is Part Of: ChemistrySelect. Volume 4:Issue 34(2019)
• Page Start: 10174
• Page End: 10180
• Publication Date: 2019-09-12
• Subjects: crystallinity -- crystallization dynamics -- crystal form -- dynamic-mechanical performance; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/slct.201902015
• Languages: English
• ISSNs: 2365-6549

Abstract

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 ( Xc ) 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 ( Tc ), and the stability of segments in crystal lattice was also enhanced at high Tc . 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 Tc of 125 °C, which is basically consistent with the condition of maximum Xc . DMA analysis supported that at high Tc, the addition of MCC greatly increased the crystallization ability of PLA and the elasticity and toughness were also improved. Abstract : MCC/PLA shows an expanded temperature range of interval 2 (105 to 145 °C) compared to pure PLA, indicating that the addition of MCC promotes the formation capability of α crystal in PLA. The two Tm s (169.8 and 177.4 °C) of MCC/PLA with Tc of 145 °C correspond to the melting of α′ crystal form resulting from the cold crystallization during DSC heating and α crystal form formed during annealing, respectively.