scholarly journals Evaluation of the Technical Viability of Distributed Mechanical Recycling of PLA 3D Printing Wastes

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1247
Author(s):  
Freddys R. Beltrán ◽  
Marina P. Arrieta ◽  
Eduardo Moreno ◽  
Gerald Gaspar ◽  
Luisa M. Muneta ◽  
...  
Keyword(s):  
3D Printing ◽  
Intrinsic Viscosity ◽  
Polymer Chains ◽  
Polymerization Process ◽  
Recycling Process ◽  
Mechanical Recycling ◽  
Recycled Materials ◽  
Industrial Processing ◽  
Overall Performance ◽  
Different Sources

3D printing PLA wastes were recovered from a well-known reference grade and from different sources. The recovered wastes were subjected to an energic washing step and then reprocessed into films by melt-extrusion, followed by compression molding to simulate the industrial processing conditions. The obtained materials were characterized and the optical, structural, thermal and crystallization behavior are reported. The mechanical recycling process leads to an increase of the crystallinity and a decrease of the intrinsic viscosity of the formulations, particularly in the sample based on blends of different 3D-PLA wastes. Moreover, the obtained films were disintegrated under composting conditions in less than one month and it was observed that recycled materials degrade somewhat faster than the starting 3D-PLA filament, as a consequence of the presence of shorter polymer chains. Finally, to increase the molecular weight of the recycled materials, the 3D-PLA wastes were submitted to a solid-state polymerization process at 110, 120, and 130 °C, observing that the recycled 3D-wastes materials based on a well-known reference grade experiences an improvement of the intrinsic viscosity, while that coming from different sources showed no significant changes. Thus, the results show that 3D printing PLA products provides an ideal environment for the implementation of distributed recycling program, in which wastes coming from well-known PLA grades can successfully be processed in films with good overall performance.

Influence of Constructive and Technological Parameters at Generated Spiral Parts with DLP 3D Printing Process

2019 ◽  
Vol 56 (4) ◽  
pp. 801-811
Author(s):  
Mircea Dorin Vasilescu
Keyword(s):  
3D Printing ◽  
Great Influence ◽  
Polymerization Process ◽  
Generation Process ◽  
Technological Parameters ◽  
Printing Process ◽  
The Third ◽  
Solid Models ◽  
Specific Factors ◽  
Printing Processes

This work are made for determine the possibility of generating the specific parts of a threaded assembly. If aspects of CAD generating specific elements was analysed over time in several works, the technological aspects of making components by printing processes 3D through optical polymerization process is less studied. Generating the threaded appeared as a necessity for the reconditioning technology or made components of the processing machines. To determine the technological aspects of 3D printing are arranged to achieve specific factors of the technological process, but also from the specific elements of a trapezoidal thread or spiral for translate granular material in supply process are determined experimentally. In the first part analyses the constructive generation process of a spiral element. In the second part are identified the specific aspects that can generation influence on the process of realization by 3D DLP printing of the two studied elements. The third part is affected to printing and determining the dimensions of the analysed components. We will determine the specific value that can influence the process of making them in rapport with printing process. The last part is affected by the conclusions. It can be noticed that both the orientation and the precision of generating solid models have a great influence on the made parts.

Electrogeneration of Conducting Poly(α-tetrathiophene). Effect of Solution Stirring and Detection of Linear Oligomers

2003 ◽  
Vol 68 (7) ◽  
pp. 1326-1344 ◽  
Author(s):  
Francesc Estrany ◽  
Ramon Oliver ◽  
Esther García ◽  
Esther Gualba ◽  
Pere-Lluís Cabot ◽  
...  
Keyword(s):  
Ion Pairs ◽  
Polymer Chains ◽  
Polymerization Process ◽  
Anodic Process ◽  
Cathodic Peak ◽  
Linear Chains ◽  
Monomer Solution ◽  
Ir Analysis ◽  
Microscopy Images ◽  
Tof Ms

The anodic oxidation of α-tetrathiophene on Pt was studied in a 1.0 mM monomer solution in 0.1 M LiClO4 in 45:35:20 acetonitrile/ethanol/DMF. Three consecutive oxidation peaks were detected by cyclic voltammetry, along with a cathodic peak related to the reduction of electroactive polarons formed during the first anodic process. Uniform, adherent, insoluble and black polymer films were obtained by chronoamperometry at 1.000 V vs Ag|AgCl corresponding to the first oxidation-polymerization process. Stirring of monomer solution promotes the production of polymer, favoring the oxidation of polymer chains with the incorporation of more doping ClO4- ions and ion pairs of Li+ClO4- in their monomeric units. The conductivity of the polymer obtained under stirring was three orders of magnitude higher than that synthesized from a quiescent solution. The scanning electron microscopy images also showed much more uniform films under stirring. This behavior points to the existence of less crosslinking in the polymer and the production of longer linear chains when the solution is stirred. IR analysis of these materials confirmed the formation of crosslinked chains with predominance of β-β linkages. Short linear oligomers such as the dimer, trimer and tetramer were detected in all polymers by MALDI-TOF-MS, thus showing a radical polycondensation as initial electropolymerization mechanism. A larger proportion of linear oligomers is formed under solution stirring.

The Influence of Recycling On Thermotropic Liquid Crystalline Polymer and Glass Fiber Composites

2021 ◽  
Author(s):  
Tianran Chen
Keyword(s):  
High Performance ◽  
Liquid Crystalline ◽  
Tensile Modulus ◽  
Crystalline Polymer ◽  
Fiber Composites ◽  
Reinforced Composites ◽  
Recycling Process ◽  
Mechanical Recycling ◽  
Glass Fiber Composites ◽  
Pp Composites

In this paper, high-performance thermotropic liquidcrystalline polymer (TLCP)/polypropylene (PP) and glassfiber (GF)/PP composites were prepared by the injectionmolding process. Mechanical recycling of TLCP/PP andGF/PP composites consisted of grinding of the injectionmolded specimens and further injection molding of thegranules. The influence of mechanical recycling onmechanical and thermal properties was investigated. In situTLCP/PP maintains tensile modulus and strength duringthe recycling process, indicating the regeneration ofpolymeric fibrils at each reprocessing stage. GF/PPcomposite exhibits deterioration of mechanical propertiesafter recycling because of fiber breakage during processing,which is a very common issue on reusing glass or carbonfiber reinforced composites. The experimental resultsreveal that the TLCP/PP composite has better recyclabilitythan GF/PP.

scholarly journals Printable Alginate Hydrogels with Embedded Network of Halloysite Nanotubes: Effect of Polymer Cross-Linking on Rheological Properties and Microstructure

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4130
Author(s):  
Svetlana A. Glukhova ◽  
Vyacheslav S. Molchanov ◽  
Boris V. Lokshin ◽  
Andrei V. Rogachev ◽  
Alexey A. Tsarenko ◽  
...  
Keyword(s):  
3D Printing ◽  
Rheological Properties ◽  
Shear Thinning ◽  
Halloysite Nanotubes ◽  
Polymer Chains ◽  
Cross Linking ◽  
Saxs Data ◽  
Nanocomposite Hydrogels ◽  
Embedded Network ◽  
The Cross

Rapidly growing 3D printing of hydrogels requires network materials which combine enhanced mechanical properties and printability. One of the most promising approaches to strengthen the hydrogels consists of the incorporation of inorganic fillers. In this paper, the rheological properties important for 3D printability were studied for nanocomposite hydrogels based on a rigid network of percolating halloysite nanotubes embedded in a soft alginate network cross-linked by calcium ions. Particular attention was paid to the effect of polymer cross-linking on these properties. It was revealed that the system possessed a pronounced shear-thinning behavior accompanied by a viscosity drop of 4–5 orders of magnitude. The polymer cross-links enhanced the shear-thinning properties and accelerated the viscosity recovery at rest so that the system could regain 96% of viscosity in only 18 s. Increasing the cross-linking of the soft network also enhanced the storage modulus of the nanocomposite system by up to 2 kPa. Through SAXS data, it was shown that at cross-linking, the junction zones consisting of fragments of two laterally aligned polymer chains were formed, which should have provided additional strength to the hydrogel. At the same time, the cross-linking of the soft network only slightly affected the yield stress, which seemed to be mainly determined by the rigid percolation network of nanotubes and reached 327 Pa. These properties make the alginate/halloysite hydrogels very promising for 3D printing, in particular, for biomedical purposes taking into account the natural origin, low toxicity, and good biocompatibility of both components.

scholarly journals Homogeneous Distribution of Polymerizable Coumarin Dyes for Active Few Mode POF

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1975
Author(s):  
Florian Jakobs ◽  
Kristoffer Harms ◽  
Jana Kielhorn ◽  
Daniel Zaremba ◽  
Pen Yiao Ang ◽  
...  
Keyword(s):  
Methyl Methacrylate ◽  
Optical Fibers ◽  
High Performance ◽  
Polymer Chains ◽  
Size Exclusion ◽  
Polymerization Process ◽  
Homogeneous Distribution ◽  
Exclusion Chromatography ◽  
Polymer Optical Fibers ◽  
Coumarin Dyes

For most kinds of active polymer optical fibers, a homogeneous distribution of dye molecules over the entire fiber length and cross section is required. In this study, chemical bonding of dyes to poly(methyl methacrylate) (PMMA) by copolymerization is achieved within the polymerization process instead of dissolving the dyes in the monomers. In combination with an improved fabrication mechanism, this leads to homogeneous dye distribution within the preforms. A method for proving the integration of the dyes into the polymer chains has been developed using high-performance liquid chromatography (HPLC) and size exclusion chromatography (SEC). Prestructured core-cladding preforms with dye-doped poly(cylohexyl methacrylate-co-methyl methacrylate)-core have been prepared with the Teflon string technique and were heat-drawn to few mode fibers.

scholarly journals Synthesis and Characterization of a Lignin-Styrene-Butyl Acrylate Based Composite

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1080
Author(s):  
Daniel López Serna ◽  
Perla Elizondo Martínez ◽  
Miguel Ángel Reyes González ◽  
Antonio Alberto Zaldívar Cadena ◽  
Erasto Armando Zaragoza Contreras ◽  
...  
Keyword(s):  
Contact Angle ◽  
Butyl Acrylate ◽  
Raw Materials ◽  
Positive Influence ◽  
Polymer Chains ◽  
Polymer Materials ◽  
Polymerization Process ◽  
Oh Groups ◽  
Water Measurement

In recent years, the pursuit of new polymer materials based on renewable raw materials has been intensified with the aim of reusing waste materials in sustainable processes. The synthesis of a lignin, styrene, and butyl acrylate based composite was carried out by a mass polymerization process. A series of four composites were prepared by varying the amount of lignin in 5, 10, 15, and 20 wt.% keeping the content of butyl acrylate constant (14 wt.%). FTIR and SEM revealed that the –OH functional groups of lignin reacted with styrene, which was observed by the incorporation of lignin in the copolymer. Additionally, DSC analysis showed that the increment in lignin loading in the composite had a positive influence on thermal stability. Likewise, Shore D hardness assays exhibited an increase from 25 to 69 when 5 and 20 wt.% lignin was used respectively. In this same sense, the contact angle (water) measurement showed that the LEBA15 and LEBA20 composites presented hydrophobic properties (whit contact angle above 90°) despite having the highest amount of lignin, demonstrating that the interaction of the polymer chains with the –OH groups of lignin was the main mechanism in the composites interaction.

Axial Control of Two-Photon Polymerization With Femtosecond Bessel Beam

2017 ◽  
Author(s):  
Xiaoming Yu ◽  
Meng Zhang ◽  
Shuting Lei
Keyword(s):  
3D Printing ◽  
Bessel Beam ◽  
Average Diameter ◽  
Axial Direction ◽  
Polymerization Process ◽  
Layer By Layer ◽  
Light Modulator ◽  
Simultaneous Generation ◽  
Two Photon ◽  
Two Photon Polymerization

Stereolithography of three-dimensional, arbitrarily-shaped objects is achieved by successively curing photopolymer on multiple 2D planes and then stacking these 2D slices into 3D objects. Often as a bottleneck for speeding up the fabrication process, this layer-by-layer approach originates from the lack of axial control of photopolymerization. In this paper, we present a novel stereolithography technology with which two-photon polymerization can be dynamically controlled in the axial direction using Bessel beam generated from a spatial light modulator (SLM) and an axicon. First, we use unmodulated Bessel beam to fabricate micro-wires with an average diameter of 100 μm and a length exceeding 10 mm, resulting in an aspect ratio > 100:1. A study on the polymerization process shows that a fabrication speed of 2 mm/s can be achieved. Defect and deformation are observed, and the micro-wires consist of multiple narrow fibers which indicate the existence of the self-writing effect. A test case is presented to demonstrate fast 3D printing of a hollow tube within one second. Next, we modulate the Bessel beam with an SLM and demonstrate the simultaneous generation of multiple focal spots along the laser propagation direction. These spots can be dynamically controlled by loading an image sequence on the SLM. The theoretical foundation of this technology is outlined, and computer simulation is conducted to verify the experimental results. The presented technology extends current stereolithography into the third dimension, and has the potential to significantly increase 3D printing speed.

Cis-Trans Isomerization of Natural Rubber under the Influence of Organo-Aluminum Compounds and Titanium Tetrachloride

1959 ◽  
Vol 32 (4) ◽  
pp. 1036-1038 ◽  
Author(s):  
B. A. Dolgoplosk ◽  
E. N. Kropacheva ◽  
K. V. Nelson
Keyword(s):  
Natural Rubber ◽  
Ultraviolet Light ◽  
Titanium Tetrachloride ◽  
Chemical Properties ◽  
Regular Structure ◽  
Polymer Chains ◽  
Polymerization Process ◽  
Aluminum Compounds ◽  
Physical And Chemical ◽  
First Time

Abstract Ziegler catalysts have become of prime importance for synthesis of polymers with regular structure, particularly cis-polyisoprene. The disruption of the structure of the chain by the formation of trans units was, until now, connected only with the influence of the physical and chemical properties of the catalyst on the nature of the addition of the diene monomers during the polymerization process. In the present work it is shown that destruction of regularity of structure can be caused by isomerization of cis units in complete polymer chains into trans units under the influence of the compounds used for initiating the polymerization process. Attempts to isomerize natural rubber by means of ultraviolet light and iodine did not give the expected effect. Ferri established for the first time that under the influence of zinc chloride and titanium tetrachloride natural rubber undergoes changes accompanied by disappearence of crystallization on stretching as shown by x-ray structure analysis. On the basis of these results the authors presumed that under the influence of these agents isomerization of cis units to trans units occurs in the natural rubber chain. The isomerization of cis-1,4 units to trans units in polybutadiene by means of ultraviolet light in the presence of organic bromine or sulfur compounds was first accomplished and proved by Golub. The formation of trans units in natural rubber under similar conditions was not observed. The study of the isomerizing effect of TiCl4 and organo-aluminum compounds was conducted by us on solutions of milled natural rubber (NK) in benzene in sealed glass ampoules. The benzene used was dried and distilled over sodium. All work was conducted in an atmosphere of dry argon. Unsaturation and microstructure of the chain was determined on each sample. The study of microstructure of polyisoprenes was carried out by means of infrared spectra, the relative content of the different configurations of the polymer chain being determined by the absorption in the 800–1000 cm−1 region. The method previously developed by one of us was used for this purpose.

Synthesis and characterization of novel organosoluble aromatic copolyimides

e-Polymers ◽  
2005 ◽  
Vol 5 (1) ◽  
Author(s):  
Jintian Yang ◽  
Wei Huang ◽  
Yongfeng Zhou ◽  
Deyue Yan ◽  
Xiaohang Wang
Keyword(s):  
Gel Permeation Chromatography ◽  
Polymer Chains ◽  
Polymerization Process ◽  
Synthesis And Characterization ◽  
Aprotic Solvents ◽  
Solution Casting ◽  
Molecular Weights ◽  
Gel Permeation ◽  
Dipolar Aprotic Solvents

AbstractA series of novel aromatic copolyimides was synthesized from pyromellitic dianhydride with the commercial diamine 4,4’-methylenebisaniline (MBA) and the diamine 4,4’-methylenebis(2-tert-butylaniline) (MBTBA) specially designed by ourselves. The solubility of the copolyimides in conventional solvents decreased with the mole ratio of MBTBA to MBA. When MBTBA/MBA was larger than 8/2, the copolyimides are soluble in low boiling point solvents (such as chloroform and tetrahydrofuran) and can form a transparent, flexible, tough film by solution casting. When MBTBA/MBA was between 7/3 and 5/5, the copolyimides are only soluble in dipolar aprotic solvents (such as dimethylformamide and N-methyl-2-pyrrolidone) and form films, too. The copolyimide was precipitated in m-cresol in the polymerization process when MBTBA/MBA was lower than 5/5. The number-average molecular weights of the soluble copolyimides measured by gel permeation chromatography were larger than 5.0·104 and the polydispersity index was higher than 1.5. Only one glass transition of these copolyimides was detected at around 350°C. The copolyimides did not show appreciable decomposition up to 400°C under air and 550°C under nitrogen, and their thermal stability increased a little with the introduction of MBA into the polymer chains.

Sign in / Sign up

Export Citation Format

Share Document