Controlling Processing, Morphology, and Mechanical Performance in Blends of Polylactide and Thermotropic Polyesters

Kort, Gijs W. de; Rastogi, Sanjay; Wilsens, Carolus H. R. M.

doi:10.1021/acs.macromol.9b01083

Cited by 20 publications

(25 citation statements)

References 69 publications

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“…The other is the processing conditions including TLCP content, processing mode, shear rate, and stretching conditions. [ 23–26 ] Here, we enhance TLCP by changing the external conditions. The fibril structure of TLCP gradually became more significant with increasing TLCP content in the composite fibers ( Figure a–f).…”

Section: Resultsmentioning

confidence: 99%

Fabrication of High Performance PET/TLCP Fibers through the Synergistic Interfacial Enhancement and Compatibilization of Functional 1D and 2D Carbon Nanomaterials

Gao

Wang

et al. 2021

Macro Materials & Eng

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The maleic anhydride functionalized graphene oxide (GO‐MA) is fabricated by an efficient and solvent‐free Diels–Alder reaction. Polyethylene terephthalate (PET)/thermotropic liquid crystal polyester (TLCP), PET/TLCP/GO‐MA, PET/TLCP/aminated multi‐walled carbon nanotubes (MWCNTs‐NH2), and PET/TLCP/GO‐MA/MWCNTs‐NH2 composite fibers are systematically melt‐spun. The structure and compatibilizing effects of GO‐MA and MWCNTs‐NH2 on the mechanical, thermal, and crystallization properties of the composite fibers are indicated. The non‐isothermal crystallization kinetics and X‐ray diffraction (XRD) data show that TLCP and nanofillers can change the crystalline morphology of PET. The mechanical properties of the fibers rise with increasing TLCP content. The tensile strength 929 MPa and modulus 17.5 GPa of the fibers with 7 wt% TLCP and 0.25 wt% nanofillers (0.1 wt% GO‐MA and 0.15 wt% MWCNTs‐NH2) are significantly higher than those with 7 wt% TLCP (tensile strength 622 MPa and modulus 16.1 GPa) and even higher than those with 15% TLCP (tensile strength 836 MPa, and modulus 18.0 GPa). When the GO‐MA and MWCNTs‐NH2 co‐exist, the anti‐dripping phenomenon is improved. Therefore, the TLCP, GO, and MWCNTs synergistically strengthens the mechanical properties. This is promising for the industrial fabrication of high‐strength fibers.

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Section: Resultsmentioning

confidence: 99%

Fabrication of High Performance PET/TLCP Fibers through the Synergistic Interfacial Enhancement and Compatibilization of Functional 1D and 2D Carbon Nanomaterials

Gao

Wang

et al. 2021

Macro Materials & Eng

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“…The performance of LCP reinforced thermoplastic composites is highly dependent on the LCP morphology which is in turn determined by the viscosity of the respective constituents of the blend and the processing conditions. ,,, A fibrillar LCP morphology ensures sufficient surface area to transfer stresses from the matrix to the LCP fibrils, which is a prerequisite for effective reinforcement. , During the formation of the fibrils, the initially spherical LCP droplets are stretched in a flow field and the LCP chains are oriented. The LCP-PLA composites are prepared via extrusion, where the LCP phase is dispersed in the PLLA matrix through droplet breakup resulting from the complex shear and extensional flow fields.…”

Section: Resultsmentioning

confidence: 99%

Importance of Viscosity Control for Recyclable Reinforced Thermoplastic Composites

et al. 2020

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Thermoplastic composites consisting of a liquid crystalline polymer (LCP) and poly(lactide) (PLA) have the potential to combine good mechanical performance with recyclability and are therefore interesting as strong and sustainable composite materials. The viscoelastic behavior of both the LCP and the PLA is of great importance for the performance of these composites, as they determine the LCP morphology in the composite and play a crucial role in preventing the loss of mechanical performance upon recycling. Though the effect of the matrix viscosity is well-documented in literature, well-controlled systems where the LCP viscosity is tailored are not reported. Therefore, four LCPs, with the same chemical backbone but different molecular weights, are used to produce reinforced LCP-PLA composites. The differences in viscosity of the LCPs and viscosity ratio between the dispersed phase and the matrix of the blends are evident in the resultant composite morphology: in all cases fibrils are formed; however, the diameter increases considerably as the viscosity ratio increases for the higher molar mass LCPs. The fibril diameter ranges from several hundred nanometer to a few micrometer. A typical layered structure in the injection molded composites is observed, where the layer-thickness is influenced by the LCP viscosity. The LCPs are found to effectively reinforce the PLLA matrix, increasing the Young’s modulus by 60% and the maximum stress by 40% for the composite containing 30 wt % of the most viscous LCP. Remarkably, this did not result in an increase in brittleness, effectively increasing the toughness of the composite compared to pure PLLA. The feasible reprocessability of this composite is confirmed, by subjecting it to three reprocessing cycles. The relaxation of the LCPs orientation upon heating is measured via in situ WAXD. We compare the relaxation in an amorphous PLA matrix and in a semicrystalline PLLA matrix with that of the pure LCPs. The matrix viscosity is found to strongly influence the relaxation. For example, in a low viscous amorphous matrix relaxation of the LCP fibrils into droplets dominates the process, whereas a semicrystalline matrix helps in maintaining the fibril morphology and intermolecular orientation of the LCP. In the latter case, the LCPs relax via contraction and coalescence of the polydomain texture and maintains a significant degree of orientation until the PLLA crystals melt and the matrix viscosity decreases. The insights gained in this study on the role of the LCP viscosity on the morphology and performance of thermoplastic composites, as well as the relaxation of LCPs in a matrix, will aid progression toward sustainable and reprocessable LCP reinforced thermoplastic composites.

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“…The increasing viscosity ratio upon cooling enhances this effect further although coalescence can still occur. For more in depth information on the topics of blend morphology and droplet deformation, the authors refer to our previous work, 22 work by Utracki and Shi, 25 and an expansive overview on the topic by Kamal. 32 …”

Section: Resultsmentioning

confidence: 99%

“…Thermotropic LCPs are a suitable reinforcing phase for such composites, as they are known to orient on a molecular level during flow, effectively enhancing their mechanical performance. , This class of materials was intensively studied during the later decades of the last century and has, due to its unique properties, received renewed interest due to its potential in 3D-printing, as strong bio-resorbable materials, and in sustainable composites . When dispersed in a thermoplastic matrix and upon the application of flow, LCPs can form elongated fibrils, effectively generating reinforced composites. , The dispersion and morphology of LCP particles and chain orientation are key parameters for the performance of LCP-reinforced composites.…”

Section: Introductionmentioning

confidence: 99%

Thermoplastic PLA-LCP Composites: A Route toward Sustainable, Reprocessable, and Recyclable Reinforced Materials

Kort

Bouvrie

Rastogi

et al. 2019

ACS Sustainable Chem. Eng.

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Reprocessing of reinforced composites is generally accompanied by loss of value and performance, as normally the reinforcing phase is damaged, or the matrix is lost in the process. In the search for more sustainable recyclable composite materials, we identify blends based on poly( l -lactide) (PLA) and thermotropic liquid crystalline polymers (LCP) as highly promising self-reinforced thermoplastic composites that can be recycled several times without loss in mechanical properties. For example, irrespective of the thermal history of the blend, injection molded bars of PLA containing 30 wt % LCP exhibit a tensile modulus of 6.4 GPa and tensile strength around 110 MPa, as long as the PLA matrix has a molecular weight of 170 kg mol –1 or higher. However, after several mechanical reprocessing steps, with the gradual decrease in the molecular weight of the PLA matrix, deterioration of the mechanical performance is observed. The origin of this behavior is found in the increasing LCP to PLA viscosity ratio: at a viscosity ratio below unity, the dispersed LCP droplets are effectively deformed into the desired fibrillar morphology during injection molding. However, deformation of LCP droplets becomes increasingly challenging when the viscosity ratio exceeds unity (i.e., when the PLA matrix viscosity decreases during consecutive reprocessing), eventually resulting in a nodular morphology, a poor molecular orientation of the LCP phase, and deterioration of the mechanical performance. This molecular weight dependency effectively places a limit on the maximum number of mechanical reprocessing steps before chemical upgrading of the PLA phase is required. Therefore, a feasible route to maintain or enhance the mechanical properties of the blend, independent of the number of reprocessing cycles, is proposed.

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Controlling Processing, Morphology, and Mechanical Performance in Blends of Polylactide and Thermotropic Polyesters

Cited by 20 publications

References 69 publications

Fabrication of High Performance PET/TLCP Fibers through the Synergistic Interfacial Enhancement and Compatibilization of Functional 1D and 2D Carbon Nanomaterials

Fabrication of High Performance PET/TLCP Fibers through the Synergistic Interfacial Enhancement and Compatibilization of Functional 1D and 2D Carbon Nanomaterials

Importance of Viscosity Control for Recyclable Reinforced Thermoplastic Composites

Thermoplastic PLA-LCP Composites: A Route toward Sustainable, Reprocessable, and Recyclable Reinforced Materials

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