Improving Stiffness, Strength, and Toughness of Poly(ω-pentadecalactone) Fibers through in Situ Reinforcement with a Vanillic Acid-Based Thermotropic Liquid Crystalline Polyester

Abstract

We report on the morphology and performance of meltdrawn poly(ω-pentadecalactone) (PPDL) fibers reinforced with a vanillic acid-based thermotropic liquid crystalline polyester (LCP). The in situ reinforced PPDL/LCP fibers developed in this work are considered to be renewable in nature, given the fact that the feedstock for both polymers can be obtained from natural resources. To prepare these fibers, the polymers were mixed in a small scale twin-screw extruder, followed by melt-drawing of the extrudate. It is demonstrated that the tensile modulus and tensile strength of the fibers increase with increasing LCP orientation and concentration. Despite the brittle nature of the pure LCP component, melt-spun PPDL/LCP fibers maintain their ductile deformation for fibers containing up to 30 wt % LCP. The improved stiffness and strength of these PPDL/LCP fibers in combination with their ductile nature ensure improved energy absorption during deformation and effectively increases their toughness compared to the pure PPDL material. A further increase of the LCP content to 40 wt % and higher results in a poor control over the blend morphology, and brittle failure of the fibers is observed after the application of 2−3% strain. Smallangle X-ray scattering data indicate that after processing transcrystallization of PPDL occurs on the surface of the oriented LCP phase. According to DSC analysis, this transcrystallization on the oriented LCP fibrils is accompanied by an increase in the crystallization temperature. These findings have been confirmed through morphological analysis using transmission electron microscopy. It is anticipated that this interfacial crystallization strengthens the PPDL/LCP interface and allows delocalization of stress during deformation.

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

“…Such behavior has been observed earlier for a similar LCP dispersion in poly(ω-pentadecalactone), and is expected to originate from surface effects resulting from the very fine LCP morphology. 19 In general, LCP-A seems to be an efficient reinforcing filler for injection molding, as the modulus and the stress at break increase greatly with increasing LCP content. This is not the case for dogbones containing LCP-B; although the modulus and stress at break are enhanced for the 10 wt % samples, higher LCP content leads to a decrease in mechanical properties.…”

“…14−16 Given the lower thermal requirements of these LCPs, they are useable for the generation of thermoplastic composites based on renewable and thermally labile polymers, including Poly( l -lactide) (PLLA), poly(butylene succinate), and poly(ω-pentadecalactone). 17−19…”

Polymeric Complex Nanoparticles Enable the Fabrication of Mechanically Superstrong and Recyclable Poly(aryl ether sulfone)-based Polymer Composites

“…4,7,10,[11][12][13] Meanwhile, superstrong thermoplastic polymers are usually difficult to dissolve in proper solvents and to process. 3,5,14,15 A conventional and widely employed strategy for reinforcement of thermoplastic polymers is homogeneously dispersing stiff nanofillers, such as silica, 9,16 clays, 10,17,18 carbon nanotubes, [19][20][21] graphene oxides, 20,[22][23][24] cellulose nanocrystals, 25,26 metal nanoparticles, 27,28 and other nanofillers 3,[29][30][31] within them. Uniform nanofiller dispersion and strong interfacial interactions between nanofillers and polymer matrices are the most crucial factors that enhance the mechanical strength of the resulting polymer composites.…”

Effect of Shear Rate on the Orientation and Relaxation of a Vanillic Acid Based Liquid Crystalline Polymer

“…In addition, draw ratio, temperature, block formation (rearrangements along the backbone at high temperatures), and flow history can influence the orientation in the fiber, and therefore yield a direct response in fiber mechanical properties. The degree of orientation is not only an important factor regarding the mechanical response of thermotropic LCP fibers, but has proven to be critical in their composites with thermoplastics as well [17,18,19,20].…”

“…Recently, we have reported on the synthesis and processing of a series of thermotropic LCPs based on vanillic acid [17,35,36]. By choosing the right monomers, high-end polymer materials can be obtained, either fully or in large part from bio-based sources.…”