scholarly journals Development of Poly(l-Lactic Acid)-Based Bending Actuators

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1187 ◽  
Author(s):  
Daniela M. Correia ◽  
Liliana C. Fernandes ◽  
Bárbara Cruz ◽  
Gabriela Botelho ◽  
Verónica de Zea Bermudez ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Room Temperature ◽  
Young Modulus ◽  
Degree Of Crystallinity ◽  
Thermal Treatments ◽  
Processing Conditions ◽  
Maximum Displacement ◽  
Mechanical And Electrical Properties ◽  
Soft Actuators ◽  
The Degree Of Crystallinity

This work reports on the development of bending actuators based on poly(l-lactic acid) (PLLA)/ionic liquid (IL) blends, through the incorporation of 40% wt. of the 1-ethyl-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][TFSI]) IL. The films, obtained by solvent casting at room temperature and 50 °C, were subjected to several post-thermal treatments at 70, 90, 120 and 140 °C, in order to modify the crystallinity of the films. The influence of the drying temperature and of [Emim][TFSI] blending on the morphological, structural, mechanical and electrical properties of the composite materials were studied. The IL induced the formation of a porous surface independently of the processing conditions. Moreover, the [Emim][TFSI] dopant and the post-thermal treatments at 70 °C promoted an increase of the degree of crystallinity of the samples. No significant changes were observed in the degree of crystallinity and Young Modulus for samples with thermal treatment between 70 and 140 °C. The viability of the developed high ionic conductive blends for applications as soft actuators was evaluated. A maximum displacement of 1.7 mm was achieved with the PLLA/[Emim][TFSI] composite prepared at 50 °C and thermally treated at 140 °C, for an applied voltage of 10 Vpp, at a frequency of 100 mHz. This work highlights interesting avenues for the use of PLLA in the field of actuators.

Rapid crystallization and mesophase formation of poly(L-lactic acid) during precipitation from a solution

e-Polymers ◽  
2018 ◽  
Vol 18 (4) ◽  
pp. 331-337 ◽  
Author(s):  
Muhammad Syazwan ◽  
Takashi Sasaki
Keyword(s):  
Lactic Acid ◽  
Crystalline Phase ◽  
Room Temperature ◽  
Chloroform Solution ◽  
Degree Of Crystallinity ◽  
Hydroxyl Group ◽  
Rapid Crystallization ◽  
Mesophase Formation ◽  
Enhanced Mobility ◽  
The Degree Of Crystallinity

AbstractVery rapid crystallization behaviors of poly(L-lactic acid) (PLLA) are observed at room temperature when it is precipitated from a chloroform solution into a large amount of alcohols (non-solvents). The resulting crystalline phase contains both a highly ordered (α) and less ordered (α′) modifications, and the fraction of these phases depends on the alcohols used as the non-solvents: methanol tends to produce the highly ordered phase. The degree of crystallinity tends to be high for lower alcohols. When the precipitation occurs in n-hexane, almost no crystalline phase is formed, but a mesomorphic phase is formed as a precursor to the crystalline phase. The results suggest that the hydroxyl group of alcohols tends to promote the crystallization of PLLA. However, it is found that the precipitation in methanol at lower temperatures, such as 0°C, does not yield any crystalline phase. It is suggested that the present rapid crystallization during precipitation originates from the enhanced mobility of PLLA molecules in a metastable (non-equilibrium) liquid state.

scholarly journals Formation of Stereocomplex Crystal and Its Effect on the Morphology and Property of PDLA/PLLA Blends

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2515
Author(s):  
Xiaolong Su ◽  
Lihua Feng ◽  
Demei Yu
Keyword(s):  
Mechanical Properties ◽  
Lactic Acid ◽  
Polylactic Acid ◽  
Dielectric Spectroscopy ◽  
Degree Of Crystallinity ◽  
Cross Linking ◽  
Processing Conditions ◽  
Mass Ratio ◽  
Mechanism Of Formation ◽  
The Degree Of Crystallinity

Stereocomplex-polylactic acid (SC-PLA) is obtained in poly(d-lactic) acid/poly(l-lactic) acid (PDLA/PLLA) blends under adjusting processing conditions. It is found that the degree of crystallinity of overall SC-PLA is up to 43.7% in PDLA/PLLA blends of 1:1 mass ratio. Formation of stereocomplex (SC) crystals forces molecular chains in the blends to be more closely arranged and further enhances interaction between molecular chains, thus forming a physical cross-linking network in the SC crystals, resulting in the blends having a special microstructure. The mechanism of formation of the SC crystal physical cross-linking network is elucidated by dielectric spectroscopy, and the relationships between homocomplex (HC) crystals, SC crystals, and amorphous regions in the blends are also analyzed. Interestingly, mechanical properties of the blends are significantly improved due to formation of an SC crystal cross-linking network.

scholarly journals Hemp Fibre Reinforced Poly(Lactic Acid) Composites

2007 ◽  
Vol 29-30 ◽  
pp. 337-340 ◽  
Author(s):  
M.A. Sawpan ◽  
K.L. Pickering ◽  
Alan Fernyhough
Keyword(s):  
Lactic Acid ◽  
Degree Of Crystallinity ◽  
Poly Lactic Acid ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Hemp Fibre ◽  
Reinforcing Material ◽  
Fibre Loading ◽  
The Degree Of Crystallinity

The potential of hemp fibre as a reinforcing material for Poly(lactic acid) (PLA) was investigated. Good interaction between hemp fibre and PLA resulted in increases of 100% for Young’s modulus and 30% for tensile strength of composites containing 30 wt% fibre. Different predictive ‘rule of mixtures’ models (e.g. Parallel, Series and Hirsch) were assessed regarding the dependence of tensile properties on fibre loading. Limited agreement with models was observed. Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) studies showed that hemp fibre increased the degree of crystallinity in PLA composites.

Morphology and Physical Properties of Thin Films of Thermoplastic Elastomers from Blends of Natural Rubber and Polyethylene

1988 ◽  
Vol 61 (4) ◽  
pp. 577-584 ◽  
Author(s):  
Sania Akhtar
Keyword(s):  
Thin Films ◽  
Room Temperature ◽  
Thermoplastic Elastomers ◽  
Degree Of Crystallinity ◽  
Elongation At Break ◽  
X Ray ◽  
Rubber Blends ◽  
The Press ◽  
High Plastic ◽  
The Degree Of Crystallinity

Abstract The morphology and properties of thin films prepared from NR-PE blends have been discussed. The present paper emphasizes the effect of method of preparation on the final properties. To this end, the films were quenched in ice (−10°C), cooled in water (25°C), cooled in air (30°C), and cooled in the press (from 160°C to room temperature) under a pressure of 0.34 MPa. The modulus, tensile and tear strengths, and elongation at break were found to vary considerably with the method of preparation. X-ray and DSC results confirmed the fact that the changes were related to the crystallite morphology rather than the degree of crystallinity. In addition, it was observed that the high rubber blends were less susceptible to the method of preparation than the high plastic blends and pure polyethylene.

scholarly journals Tailored Biodegradable and Electroactive Poly(hydroxybutyrate-co-hydroxyvalerate) Based Morphologies for Tissue Engineering Applications

2018 ◽  
Author(s):  
Luís Amaro ◽  
Daniela M. Correia ◽  
Teresa Marques-Almeida ◽  
Pedro M. Martins ◽  
Leyre Pérez ◽  
...  
Keyword(s):  
Tissue Engineering ◽  
Young Modulus ◽  
Degree Of Crystallinity ◽  
Engineering Applications ◽  
Cell Proliferation And Differentiation ◽  
Cobalt Ferrites ◽  
Physico Chemical ◽  
Proliferation And Differentiation ◽  
The Degree Of Crystallinity ◽  
Composite Samples

Polymer-based piezoelectric biomaterials have already proven their relevance for tissue engineering applications. Further, the morphology of the scaffolds plays also an important role in cell proliferation and differentiation. The present work reports on poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), a biocompatible, biodegradable and piezoelectric biopolymer that has been processed in different morphologies, including films, fibres, microspheres and 3D scaffolds. Further, the corresponding magnetically active PHBV-based composites were also produced. The effect of the morphology on physico-chemical, thermal, magnetic and mechanical properties of pristine and composites samples was evaluated, as well as their cytotoxicity. It was observed that the morphology does not strongly affect the properties of the pristine samples but the introduction of cobalt ferrites induces changes in the degree of crystallinity that could affect the applicability of prepared biomaterials. Young modulus is dependent of the morphology and also increases with the addition of cobalt ferrites. Both, pristine and PHBV/cobalt ferrite composite samples are no cytotoxic, indicating their suitability for tissue engineering applications.

Blending and plasticising effects on the behaviour of poly(lactic acid)/poly(ε-caprolactone)

2018 ◽  
Vol 26 (5-6) ◽  
pp. 337-345 ◽  
Author(s):  
Nesrine Khitas ◽  
Kamira Aouachria ◽  
Mohamed Tahar Benaniba
Keyword(s):  
Thermal Stability ◽  
Lactic Acid ◽  
Nucleating Agent ◽  
Degree Of Crystallinity ◽  
Poly Lactic Acid ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Triethyl Citrate ◽  
Acetyl Tributyl Citrate ◽  
The Degree Of Crystallinity

Polymer blending is one of the most convenient methods to be used to overcome the limitations of some single properties of polymers and to achieve the combinations required for specific applications. Another feasible common practice is the incorporation of additives of low molecular weight such as plasticisers to impart flexibility, improve toughness and lower the glass transition temperature ( Tg). This study focused on the effects of blending and plasticising on the crystallisation behaviour of poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL). PCL with longer degradation time compared with other polymers was blended with PLA to overcome the limitation of its brittleness and poor thermal stability. Acetyl tributyl citrate (ATBC) and acetyl triethyl citrate (TEC) were used as plasticiser in PLA/PCL blends. The rigid and plasticised blends at various ratios were analysed by differential scanning calorimetry, thermogravimetric analysis and X-ray diffraction. The results revealed a slight increase in the degree of crystallinity and a significant increase in the Tg of PLA due to the addition of PCL. The addition of ATBC has promoted a decrease in thermal stability of the blends. The slight increase in the degree of crystallinity suggested that PCL acted as a nucleating agent. The citrate plasticisers were shown to lower the Tg and have much more enhanced the crystallisation of PLA. Moreover, the rigid and plasticised blends were shown to be partially miscible.

scholarly journals Comparative Study of Crystallization, Mechanical Properties, and In Vitro Cytotoxicity of Nanocomposites at Low Filler Loadings of Hydroxyapatite for Bone-Tissue Engineering Based on Poly(l-lactic acid)/Cyclo Olefin Copolymer

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3865
Author(s):  
Farzana Nazir ◽  
Mudassir Iqbal
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Lactic Acid ◽  
Ternary System ◽  
Bone Tissue Engineering ◽  
Bone Tissue ◽  
Crystal Form ◽  
Degree Of Crystallinity ◽  
The Degree Of Crystallinity

A poly(l-lactic acid)/nanohydroxyapatite (PLLA/nHA) scaffold works as a bioactive, osteoconductive scaffold for bone-tissue engineering, but its low degradation rate limits embedded HA in PLLA to efficiently interact with body fluids. In this work, nano-hydroxyapatite (nHA) was added in lower filler loadings (1, 5, 10, and 20 wt%) in a poly(l-lactic acid)/cyclo olefin copolymer10 wt% (PLLA/COC10) blend to obtain novel poly(l-lactic acid)/cyclo olefin copolymer/nanohydroxyapatite (PLLA/COC10-nHA) scaffolds for bone-tissue regeneration and repair. Furthermore, the structure-activity relationship of PLLA/COC10-nHA (ternary system) nanocomposites in comparison with PLLA/nHA (binary system) nanocomposites was systematically studied. Nanocomposites were evaluated for structural (morphology, crystallization), thermomechanical properties, antibacterial potential, and cytocompatibility for bone-tissue engineering applications. Scanning electron microscope images revealed that PLLA/COC10-nHA had uniform morphology and dispersion of nanoparticles up to 10% of HA, and the overall nHA dispersion in matrix was better in PLLA/COC10-nHA as compared to PLLA/nHA. Fourier transformation infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), and differential scanning calorimetry (DSC) studies confirmed miscibility and transformation of the α-crystal form of PLLA to the ά-crystal form by the addition of nHA in all nanocomposites. The degree of crystallinity (%) in the case of PLLA/COC10-nHA 10 wt% was 114% higher than pure PLLA/COC10 and 128% higher than pristine PLLA, indicating COC and nHA are acting as nucleating agents in the PLLA/COC10-nHA nanocomposites, causing an increase in the degree of crystallinity (%). Moreover, PLLA/COC10-nHA exhibited 140 to 240% (1–20 wt% HA) enhanced mechanical properties in terms of ductility as compared to PLLA/nHA. Antibacterial activity results showed that 10 wt% HA in PLLA/COC10-nHA showed substantial activity against P. aeruginosa, S. aureus, and L. monocytogenes. In vitro cytocompatibility of PLLA/COC10 and PLLA nanocomposites with nHA osteoprogenitor cells (MC3T3-E1) and bone mesenchymal stem cells (BMSC) was evaluated. Both cell lines showed two- to three-fold enhancement in cell viability and 10- to 30-fold in proliferation upon culture on PLLA/COC10-nHA as compared to PLLA/nHA composites. It was observed that the ternary system PLLA/COC10-nHA had good dispersion and interfacial interaction resulting in improved thermomechanical and enhanced osteoconductive properties as compared to PLLA/nHA.

scholarly journals Effect of Graphite Nanosheets on Properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Larissa Stieven Montagna ◽  
Thaís Larissa do Amaral Montanheiro ◽  
João Paulo Barros Machado ◽  
Fábio Roberto Passador ◽  
Ana Paula Lemes ◽  
...  
Keyword(s):  
Degree Of Crystallinity ◽  
Thermal Treatments ◽  
X Ray Diffraction ◽  
Nucleation Agent ◽  
Physical Treatment ◽  
Graphite Nanosheets ◽  
Chemical Exfoliation ◽  
Solution Casting Method ◽  
Graphite Sheets ◽  
The Degree Of Crystallinity

The influence of different contents, 0.25, 0.50, and 1.00 wt%, of graphite nanosheets (GNS) on the properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanocomposites obtained by solution casting method has been studied. GNS were prepared by three steps: intercalation (chemical exfoliation), expansion (thermal treatment), and the GNS obtainment (physical treatment by ultrasonic exfoliation). X-ray diffraction (XRD), Raman spectroscopy, and field emission gun-scanning electron microscopy (FE-SEM) showed that the physical, chemical, and thermal treatments preserved the graphite sheets structure. XRD and Raman results also showed that GNS were dispersed in the PHBV matrix. The degree of crystallinity (Xc) of the nanocomposites did not change when the graphite nanosheets were added. However, the GNS acted as nucleation agent for crystallization; that is, in the second heating the samples containing GNS showed two melting peaks. The addition the GNS did not change the thermal stability of the PHBV.

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