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 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.

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.

Effect of Poly(Hexamethylene Succinamide) on Crystallization of Poly(L-Lactic Acid)

2017 ◽  
Vol 751 ◽  
pp. 302-307
Author(s):  
Panadda Yueagyen ◽  
Amornrat Lertworasirikul
Keyword(s):  
Mechanical Properties ◽  
Lactic Acid ◽  
Crystallization Temperature ◽  
Crystallization Rate ◽  
Weight Percent ◽  
Degree Of Crystallinity ◽  
Nucleating Agents ◽  
Melt Polymerization ◽  
The Degree Of Crystallinity ◽  
Aliphatic Amide

Poly(L-lactic acid) (PLA) has good mechanical properties and is biodegradable. However, its crystallization rate is slow, crystallization period long, and its crystallization temperature high at 116 °C. Consequently, long processing cycles are required for the production of high crystallinity poly (L-lactic acid). Addition of nucleating agents is an efficient way to solve this problem. Aliphatic amide such as N,N-ethylenebis(12-hydroxystearamide) and ethylenebis-stearamide are reported as nucleating agents for poly (L-lactic acid). In this study, the effect of the aliphatic polyamide, poly (hexamethylene succinamide) on the crystallization behavior of PLA was investigated. Poly (hexamethylene succinamide) was synthesized by melt polymerization. Between one and ten weight percent poly (hexamethylene succinamide) was blended with poly (L-lactic acid) by melt extrusion. The crystallization temperature and crystallization period decreased with increasing poly (hexamethylene succinamide) content. The degree of crystallinity increased with the addition of poly (hexamethylene succinamide). A poly (hexamethylene succinamide) content of 5%wt provides optimum conditions for production of poly (L-lactic acid)-poly (hexamethylene succinamide) blend with good mechanical properties. The polymers obtained are entirely from renewable resources.

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.

The Effect of Methylene Diphenyl Diisocyanate on the Nonisothermal Properties of Polylactic Acid/Elaeis guineensis Fibres Biocomposites

2013 ◽  
Vol 594-595 ◽  
pp. 823-827
Author(s):  
Luqman Hakim Ahmad Subri ◽  
Sakinah Mohd Alauddin ◽  
Senawi Rosman
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Polylactic Acid ◽  
Elaeis Guineensis ◽  
Fibre Surface ◽  
Degree Of Crystallinity ◽  
Chain Mobility ◽  
Methylene Diphenyl Diisocyanate ◽  
The Degree Of Crystallinity

Biocomposites demands are significantly rising due to environmental regulations and concerns. However, incompatibility between the fibre and matrix is a major setback that diminishes the biocompostie properties. Therefore in this work, methylene diphenyl diisocynate (MDI) compatibilizers were used together with fibre surface treatment in order to increase compatibility between polylactic acid (PLA) and Elaeis Guineensis Fibres (EGF) biocomposite. Nonisothermal properties were investigated and it was found that, MDI increased compatibility of the PLA and EGF which led to the restriction of chain movements in the biocomposite. This restriction in chain mobility caused an increase the glass transition temperature and crystallization temperature and also reduced the degree of crystallinity.

scholarly journals Crystallization Kinetics of Poly(lactic acid)–Graphene Nanoscroll Nanocomposites: Role of Tubular, Planar, and Scrolled Carbon Nanoparticles

2021 ◽  
Vol 7 (4) ◽  
pp. 75
Author(s):  
Oluwakemi Ajala ◽  
Caroline Werther ◽  
Rauf Mahmudzade ◽  
Peyman Nikaeen ◽  
Dilip Depan
Keyword(s):  
Mechanical Properties ◽  
Lactic Acid ◽  
Crystallization Kinetics ◽  
Crystallization Rate ◽  
Melting Behavior ◽  
Degree Of Crystallinity ◽  
Poly Lactic Acid ◽  
Avrami Model ◽  
Superior Mechanical Properties ◽  
Kinetics Of

Graphene nanoscrolls (GNS) are 1D carbon-based nanoparticles. In this study, they were investigated as a heterogeneous nucleating agent in the poly(lactic acid) (PLA) matrix. The isothermal and non-isothermal melting behavior and crystallization kinetics of PLA-GNS nanocomposites were investigated using a differential scanning calorimeter (DSC). Low GNS content not only accelerated the crystallization rate, but also the degree of crystallinity of PLA. The Avrami model was used to fit raw experimental data, and to evaluate the crystallization kinetics for both isothermal and non-isothermal runs through the nucleation and growth rate. Additionally, the effect of the dimensionality and structure of the nanoparticle on the crystallization behavior and kinetics of PLA is discussed. GNS, having a similar fundamental unit as CNT and GNP, were observed to possess superior mechanical properties when analyzed by the nanoindentation technique. The scrolled architecture of GNS facilitated a better interface and increased energy absorption with PLA compared to CNTs and GNPs, resulting in superior mechanical properties.

scholarly journals Improving the shape stability and enhancing the properties of layer dependent material extruded biodegradable polylactic acid for thin implants

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Alper Ekinci ◽  
Xiaoxiao Han ◽  
Andrew Gleadall ◽  
Andrew Allan Johnson
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Polylactic Acid ◽  
Testing Machine ◽  
Degree Of Crystallinity ◽  
Annealed Specimen ◽  
Future Research ◽  
Shape Stability ◽  
Tensile Testing Machine ◽  
Content Type

Purpose This paper aims to establish an appropriate annealing method, which is necessary for shape stability and to evaluate their potential degradation performance of 1-, 3- and 5-layer material extruded polylactic-acid specimens by enhancing their thermal and mechanical properties. Design/methodology/approach The distortion of each layered printed specimen subjected to degradation was calculated in x- and y-direction. Each layered specimen was subjected to annealing at 70°C, 80°C and 90°C for 2 h and at 80°C for 1, 4, 8 and 16 h. Thermal, molecular weight and mechanical properties were calculated using, differential scanning calorimetry, gel permeation chromatography and tensile testing machine, respectively. Findings In the x-direction, distortion was 16.08 mm for one-layer non-annealed printed specimens and decreased by 73% and 83% for 3- and 5-layer, respectively, while each layered non-annealed specimen subjected to degradation at 37°C for one month. Within the outlined study, annealing treatment enhances properties such as the degree of crystallinity (%χ) up to 34%, Young’s modulus (E) by 30% and ultimate tensile strength by 20% compared to the non-annealed specimens. Practical implications The future research accomplishments will be concentrated on the design, development and optimisation of degraded biomedical implants using material extrusion thin films including drug delivery system and fixation plates. Originality/value The printed thin specimens subjected to degradation were investigated. This research developed a new understanding of the effect of the annealing temperature and time on the mechanical, thermal and molecular weight properties for each layered specimen.

scholarly journals LMPP Effects on Morphology, Crystallization, Thermal and Mechanical Properties of iPP/LMPP Blend Fibres

2018 ◽  
Vol 26 (2(128)) ◽  
pp. 26-31 ◽  
Author(s):  
Munir Hussain ◽  
Feichao Zhu ◽  
Feichao Zhu ◽  
Bin Yu ◽  
Bin Yu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Properties ◽  
Elastic Modulus ◽  
Isotactic Polypropylene ◽  
Degree Of Crystallinity ◽  
Thermal And Mechanical Properties ◽  
Elongation At Break ◽  
Breaking Elongation ◽  
Low Modulus ◽  
The Degree Of Crystallinity

The thermal properties and morphological characterisation of isotactic polypropylene (iPP) homopolymer and its blends with low molecular low modulus polypropylene (LMPP) were studied. Firstly blends were prepared with variant LMPP contents, and their properties were characterised using SEM, DSC, XRD, and DMA. Later the mechanical properties of iPP/LMPP blend fibres were investigated. SEM results showed that the iPP/LMPP blends produced smoother surfaces when the LMPP content was increased, as well as the miscibility. All the Tg values with different LMPP percentages were in-between pure iPP and LMPP. The XRD results indicated the LMPP percentage decreased along with the degree of crystallinity of the iPP/LMPP blends (5% to 15%), which increased and then decreased as compared to pure iPP. The elongation at break increased when the LMPP content increased, with the maximum breaking elongation of the LMPP 25% blend reaching 12.95%, which showed great stretch-ability, whereas the elastic modulus of iPP/LMPP blends decreased.

scholarly journals The Structure and Mechanical Properties of the UHMWPE Films Modified by the Mixture of Graphene Nanoplates with Polyaniline

Polymers ◽  
2018 ◽  
Vol 11 (1) ◽  
pp. 23 ◽  
Author(s):  
Tarek Dayyoub ◽  
Aleksey Maksimkin ◽  
Sergey Kaloshkin ◽  
Evgeniy Kolesnikov ◽  
Dilus Chukov ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Mechanical Properties ◽  
Filler Content ◽  
Dynamic Mechanical Properties ◽  
Degree Of Crystallinity ◽  
Functionalized Graphene ◽  
Lamellar Crystal ◽  
The Degree Of Crystallinity ◽  
Heterogeneous Crystallization ◽  
Graphene Nanoplates

Highly oriented UHMWPE films were reinforced with functionalized graphene nanoplates (GNP). GNP was functionalized by deposition of polyaniline (PANI) on the GNP surface. The structure of GNP/PANI was studied by Raman spectroscopy, and the structure of xerogels and films based on UHMWPE was studied by DSC and SEM. PANI promotes the reduction of the GNP aggregation in the UHMWPE matrix and increases the degree of crystallinity due to heterogeneous crystallization. The new lamellar crystal structure has a high drawability. The highest value of the tensile strength 1330 MPa (an increase of 45%) was obtained with a filler content of 2 wt % GNP/PANI, and the highest value of Young’s modulus 41 GPa (an increase of 32%) was obtained with a filler content of 1 wt % GNP/PANI. The effect of GNP with PANI fillers on the dynamic mechanical properties of the UHMWPE films was discussed.

Study on Mechanical Property of Polylactic Acid Toughened by Polyacrylate Microsphere

2013 ◽  
Vol 781-784 ◽  
pp. 390-394
Author(s):  
Xiao Li Song ◽  
Ying Chen ◽  
Yu Zhi Xu ◽  
Chun Peng Wang
Keyword(s):  
Mechanical Properties ◽  
Impact Strength ◽  
Polylactic Acid ◽  
Strength Loss ◽  
Core Shell ◽  
Mass Ratio ◽  
Elongation At Break ◽  
Emulsion Copolymerization ◽  
The Impact ◽  
Toughening Agent

Polyacrylate microsphere with different core/shell ratio (mass ratio) were prepared by semi-continuous seed emulsion copolymerization using butyl acrylate (BA) and methyl methacrylate (MMA) as main monomers，which were used to toughen polylactic acid (PLA) after drying. The effect of core/shell ratio of polyacrylate toughening agent (ACR) on mechanical properties of PLA was studied. The results showed that when adding 8wt%ACR, the impact strength and elongation at break of PLA were both first increased and then decreased as increasing of core/shell ratio, while the tensile strength loss of PLA was little changed. It is found that the impact strength was increased about 24% than that of neat PLA as well as the elongation at break was increased from 2% to 12% when the ratio was 7/3, which was the best ratio.

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