scholarly journals Improving Mechanical Properties for Extrusion-Based Additive Manufacturing of Poly(Lactic Acid) by Annealing and Blending with Poly(3-Hydroxybutyrate)

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1529 ◽  
Author(s):  
Sisi Wang ◽  
Lode Daelemans ◽  
Rudinei Fiorio ◽  
Maling Gou ◽  
Dagmar R. D’hooge ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Additive Manufacturing ◽  
Mechanical Performance ◽  
Softening Temperature ◽  
Xrd Analysis ◽  
Sem Analysis ◽  
Poly Lactic Acid ◽  
Second Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry

Based on differential scanning calorimetry (DSC), X-ray diffraction (XRD) analysis, polarizing microscope (POM), and scanning electron microscopy (SEM) analysis, strategies to close the gap on applying conventional processing optimizations for the field of 3D printing and to specifically increase the mechanical performance of extrusion-based additive manufacturing of poly(lactic acid) (PLA) filaments by annealing and/or blending with poly(3-hydroxybutyrate) (PHB) were reported. For filament printing at 210 °C, the PLA crystallinity increased significantly upon annealing. Specifically, for 2 h of annealing at 100 °C, the fracture surface became sufficiently coarse such that the PLA notched impact strength increased significantly (15 kJ m−2). The Vicat softening temperature (VST) increased to 160 °C, starting from an annealing time of 0.5 h. Similar increases in VST were obtained by blending with PHB (20 wt.%) at a lower printing temperature of 190 °C due to crystallization control. For the blend, the strain at break increased due to the presence of a second phase, with annealing only relevant for enhancing the modulus.

scholarly journals Improving the Toughness and Thermal Resistance of Polyoxymethylene/Poly(lactic acid) Blends: Evaluation of Structure–Properties Correlation for Reactive Processing

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 307 ◽  
Author(s):  
Jacek Andrzejewski ◽  
Katarzyna Skórczewska ◽  
Arkadiusz Kloziński
Keyword(s):  
Lactic Acid ◽  
Thermal Resistance ◽  
High Efficiency ◽  
Mechanical Performance ◽  
Softening Temperature ◽  
Thermomechanical Properties ◽  
Poly Lactic Acid ◽  
Reactive Processing ◽  
Scanning Calorimetry ◽  
The Impact

The study focuses on the development of polyoxymethylene (POM)/poly(lactic acid) (PLA) blends with increased impact and thermal resistance. The study was conducted in two phases; in the first part, a series of unmodified blends with PLA content of 25, 50, and 75 wt.% was prepared, while the second part focused on the modification of the PLA/POM (50/50) blends. An ethylene/butyl acrylate/glycidyl methacrylate terpolymer (E/BA/GMA) elastomer (EBA) was used to improve the impact strength of the prepared blends, while reactive blending was used to improve interfacial interactions. We used a multifunctional epoxy chain extender (CE) as the compatibilizer. Static tensile tests and notched Izod measurement were used to evaluate the mechanical performance of the prepared samples. The thermomechanical properties were investigated using dynamic mechanical thermal analysis (DMTA) analysis and heat deflection temperature (HDT)/Vicat softening temperature (VST) methods. The crystallinity was measured using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXS) measurements, while the rheology was evaluated using a rotational rheometer. The paper also includes a structure analysis performed using the SEM method. The structural tests show partial miscibility of the POM/PLA systems, resulting in the perfect compatibility of both phases. The impact properties of the final blends modified by the EBA/CE system were found to be similar to pure POM resin, while the E modulus was visibly improved. Favorable changes were also noticeable in the case of the thermomechanical properties. The results of most of the conducted measurements and microscopic observations confirm the high efficiency of the reaction for PLA as well as for the modified POM/PLA mixtures.

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.

Crystallization Properties of Nucleated Poly(lactic acid)

2012 ◽  
Vol 549 ◽  
pp. 322-326 ◽  
Author(s):  
Yong Chen ◽  
Qiang Dou
Keyword(s):  
Lactic Acid ◽  
Crystallization Behavior ◽  
Polarized Light ◽  
Nucleating Agent ◽  
Poly Lactic Acid ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Crystallization Properties ◽  
Melting And Crystallization

The effect of a nucleating agent (NT-C) on the crystallization behavior of poly(lactic acid) (PLA) was studied. The melting and crystallization behavior and spherulitic morphology of the nucleated PLA were investigated by means of differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and polarized light microscopy (PLM). It is found that the crystallization temperature and crystallinity increase, the spherulitic size decrease for the nucleated PLA. But the crystal structure of the nucleated PLA is not changed.

scholarly journals Composites Based on Poly(Lactic Acid) (PLA) and SBA-15: Effect of Mesoporous Silica on Thermal Stability and on Isothermal Crystallization from Either Glass or Molten State

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2743
Author(s):  
Tamara M. Díez-Rodríguez ◽  
Enrique Blázquez-Blázquez ◽  
Ernesto Pérez ◽  
María L. Cerrada
Keyword(s):  
Lactic Acid ◽  
Mesoporous Silica ◽  
Isothermal Crystallization ◽  
Physical Aging ◽  
Glassy State ◽  
Poly Lactic Acid ◽  
Molten State ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray

Several composites based on an L-rich poly(lactic acid) (PLA) with different contents of mesoporous Santa Barbara Amorphous (SBA-15) silica were prepared in order to evaluate the effect of the mesoporous silica on the resultant PLA materials by examining morphological aspects, changes in PLA phases and their transitions, and, primarily, the influence on some final properties. Melt extrusion was chosen for the obtainment of the composites, followed by quenching from the melt to prepare films. Completely amorphous samples were then attained, as deduced from X-ray diffraction and differential scanning calorimetry (DSC) analyses. Thermogravimetric analysis (TGA) results demonstrated that the presence of SBA-15 particles in the PLA matrix did not exert any significant influence on the thermal decomposition of these composites. An important nucleation effect of the silica was found in PLA, especially under isothermal crystallization either from the melt or from its glassy state. As expected, isothermal crystallization from the glass was considerably faster than from the molten state, and these high differences were also responsible for a more considerable nucleating role of SBA-15 when crystallizing from the melt. It is remarkable that the PLA under analysis showed very close temperatures for cold crystallization and its subsequent melting. Moreover, the type of developed polymorphs did not accomplish the common rules previously described in the literature. Thus, all the isothermal experiments led to exclusive formation of the α modification, and the observation of the α’ crystals required the annealing for long times at temperatures below 80 °C, as ascertained by both DSC and X-ray diffraction experiments. Finally, microhardness (MH) measurements indicated a competition between the PLA physical aging and the silica reinforcement effect in the as-processed amorphous films. Physical aging in the neat PLA was much more important than in the PLA matrix that constituted the composites. Accordingly, the MH trend with SBA-15 content was strongly dependent on aging times.

scholarly journals The effect of beta-tricalcium phosphate on mechanical and thermal performances of poly(lactic acid)

2016 ◽  
Vol 50 (30) ◽  
pp. 4189-4198 ◽  
Author(s):  
JM Ferri ◽  
I Gisbert ◽  
D García-Sanoguera ◽  
MJ Reig ◽  
R Balart
Keyword(s):  
Thermal Analysis ◽  
Lactic Acid ◽  
Tricalcium Phosphate ◽  
Mechanical Performance ◽  
Poly Lactic Acid ◽  
Mechanical Resistance ◽  
Dynamical Response ◽  
Scanning Calorimetry ◽  
Base Materials ◽  
Beta Tricalcium Phosphate

Orthophosphates are bioactive crystals with similar structure, in terms of elemental composition and crystal nature, to human bone. In this work, biocomposite materials were prepared with poly(lactic acid) (PLA) as matrix, and beta-tricalcium phosphate (β-TCP) as osteoconductive filler by extrusion-compounding followed by conventional injection molding. The β-TCP load content was varied in the 10–40 wt% range and the influence of the β-TCP load on mechanical performance of PLA/β-TCP composites was evaluated. Mechanical properties of composites were obtained by standardized tensile, flexural, impact, and hardness tests. Thermal analysis of composites was carried out by means of differential scanning calorimetry; degradation at high temperatures was studied by thermogravimetric analysis; and the effect of the β-TCP load on dynamical response of composites was studied by mechanical thermal analysis in torsion mode. The best-balanced properties were obtained for PLA composites containing 30 wt% β-TCP with a remarkable increase in the Young’s modulus. These materials offer interesting properties to be used as base materials for medical applications such as interference screws due to high stiffness and mechanical resistance.

scholarly journals Heat Treatment Effects on the Mechanical Properties and Morphologies of Poly (Lactic Acid)/Poly (Butylene Adipate-co-terephthalate) Blends

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Hsien-Tang Chiu ◽  
Szu-Yuan Huang ◽  
Yan-Fu Chen ◽  
Ming-Tai Kuo ◽  
Tzong-Yiing Chiang ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Lactic Acid ◽  
Impact Strength ◽  
Sem Analysis ◽  
Poly Lactic Acid ◽  
Scanning Calorimetry ◽  
Two Phase ◽  
Degree Of Crystallization ◽  
High Degree ◽  
Lower Tensile Strength

In this study the relationships between mechanicals properties and morphology of the poly (lactic acid) (PLA)/poly (butylene adipate-co-terephthalate) (PBAT) blends with or without heat treatment were investigated. The differential scanning calorimetry (DSC) analysis showed that blends have a two-phase structure indicating that they are immiscible. On the other hand, the PLA/PBAT (30/70) blend achieved the best tensile and impact strength because of its sea-island morphology, except for high PBAT content. The PLA/PBAT (70/30) and PLA/PBAT (50/50) blends showed irregular and directive-layer morphologies, in scanning electron microscopy (SEM) analysis, producing a break cross-section with various fiber shapes. Both blends showed lower tensile strength and impact strength than the PLA/PBAT (30/70). After heat treatment, the PLA/PBAT blends showed high modulus of tensile and HDT because of a high degree of crystallization. The high degree of crystallization in the blends, which originated in the heat treatment, reduced their impact strength and elongation. However, the effect of high degree of crystallization on the PLA/PBAT (30/70) blend was small because of its sea-island morphology.

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 Material Extrusion-Based Additive Manufacturing of Poly(Lactic Acid) Antibacterial Filaments—A Case Study of Antimicrobial Properties

Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4337
Author(s):  
Piotr Gruber ◽  
Viktoria Hoppe ◽  
Emilia Grochowska ◽  
Justyna Paleczny ◽  
Adam Junka ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Additive Manufacturing ◽  
Methodological Approach ◽  
Antibacterial Properties ◽  
Antimicrobial Properties ◽  
Sem Analysis ◽  
Poly Lactic Acid ◽  
Fused Filament Fabrication ◽  
Personal Protection Equipment ◽  
Specific Species

In the era of the coronavirus pandemic, one of the most demanding areas was the supply of healthcare systems in essential Personal Protection Equipment (PPE), including face-shields and hands-free door openers. This need, impossible to fill by traditional manufacturing methods, was met by implementing of such emerging technologies as additive manufacturing (AM/3D printing). In this article, Poly(lactic acid) (PLA) filaments for Fused filament fabrication (FFF) technology in the context of the antibacterial properties of finished products were analyzed. The methodology included 2D radiography and scanning electron microscopy (SEM) analysis to determine the presence of antimicrobial additives in the material and their impact on such hospital pathogens as Staphylococcus aureus, Pseudomonas aeruginosa, and Clostridium difficile. The results show that not all tested materials displayed the expected antimicrobial properties after processing in FFF technology. The results showed that in the case of specific species of bacteria, the FFF samples, produced using the declared antibacterial materials, may even stimulate the microbial growth. The novelty of the results relies on methodological approach exceeding scope of ISO 22196 standard and is based on tests with three different species of bacteria in two types of media simulating common body fluids that can be found on frequently touched, nosocomial surfaces. The data presented in this article is of pivotal meaning taking under consideration the increasing interest in application of such products in the clinical setting.

Effect of low nanoclay content on the physico-mechanical properties of poly(lactic acid) nanocomposites

2018 ◽  
Vol 27 (2) ◽  
pp. 43-54 ◽  
Author(s):  
JR Robledo-Ortíz ◽  
AS Martín del Campo ◽  
EJ López-Naranjo ◽  
M Arellano ◽  
CF Jasso-Gastinel ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Impact Strength ◽  
Flexural Strength ◽  
Mechanical Performance ◽  
Flexural Modulus ◽  
Poly Lactic Acid ◽  
Scanning Calorimetry ◽  
Degradation Temperature ◽  
Nanoclay Content ◽  
The Impact

In this work, three different nanoclays (1.44P, 1.34MN, and Cloisite 15A) were used to reinforce an injection grade poly(lactic acid) (PLA). The nanocomposites (NCs) were prepared using three different nanoclay concentration levels (1, 3, and 5 wt%) in a twin-screw extruder. To evaluate their mechanical performance (static and dynamic tests) and thermal properties, the respective samples were obtained by injection molding. Results showed that the three nanoclays significantly increased the tensile and flexural modulus of the injection grade PLA. The 1.34MN NCs also showed improvement in the tensile strength. An increment in flexural strength was obtained with 1.34MN and 1.44P nanoclays, while with nanoclay 15A, the flexural strength decreased. Additionally, the use of 5 wt% of 1.44P nanoclay allowed an increase in impact strength while using 1.34MN and 15A nanoclays, the impact strength was similar to the one observed for pure PLA. In general, mechanodynamic analysis results showed that storage modulus increased with nanoclay content; while thermogravimetric analysis indicated that none of the nanoclays has a significant effect over the degradation temperature of pure PLA. Differential scanning calorimetry results showed that the crystallinity of PLA is enhanced with nanoclay inclusion. For 1.34MN NCs, X-ray diffraction observations exposed that the mineral clay relative intensity peaks disappeared indicating nanoclay exfoliation, which contributes to the increase in tensile and flexural strength in the NCs. Nevertheless for 1.44P and 15A nanoclays, an increase in the interlayer distance (intercalation) was detected.

scholarly journals High-Toughness Poly(lactic Acid)/Starch Blends Prepared through Reactive Blending Plasticization and Compatibilization

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5951
Author(s):  
Huan Hu ◽  
Ang Xu ◽  
Dianfeng Zhang ◽  
Weiyi Zhou ◽  
Shaoxian Peng ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Performance Test ◽  
Mechanical Performance ◽  
Raw Materials ◽  
Amorphous Region ◽  
Poly Lactic Acid ◽  
Esterification Reaction ◽  
Melt Blending ◽  
Scanning Calorimetry ◽  
Starch Blends

In this study, poly(lactic acid) (PLA)/starch blends were prepared through reactive melt blending by using PLA and starch as raw materials and vegetable oil polyols, polyethylene glycol (PEG), and citric acid (CA) as additives. The effects of CA and PEG on the toughness of PLA/starch blends were analyzed using a mechanical performance test, scanning electron microscope analysis, differential scanning calorimetry, Fourier-transform infrared spectroscopy, X-ray diffraction, rheological analysis, and hydrophilicity test. Results showed that the elongation at break and impact strength of the PLA/premixed starch (PSt)/PEG/CA blend were 140.51% and 3.56 kJ·m−2, which were 13.4 and 1.8 times higher than those of pure PLA, respectively. The essence of the improvement in the toughness of the PLA/PSt/PEG/CA blend was the esterification reaction among CA, PEG, and starch. During the melt-blending process, the CA with abundant carboxyl groups reacted in the amorphous region of the starch. The shape and crystal form of the starch did not change, but the surface activity of the starch improved and consequently increased the adhesion between starch and PLA. As a plasticizer for PLA and starch, PEG effectively enhanced the mobility of the molecular chains. After PEG was dispersed, it participated in the esterification reaction of CA and starch at the interface and formed a branched/crosslinked copolymer that was embedded in the interface of PLA and starch. This copolymer further improved the compatibility of the PLA/starch blends. PEGs with small molecules and CA were used as compatibilizers to reduce the effect on PLA biodegradability. The esterification reaction on the starch surface improved the compatibilization and toughness of the PLA/starch blend materials and broadens their application prospects in the fields of medicine and high-fill packaging.

Sign in / Sign up

Export Citation Format

Share Document