Compósitos Híbridos Condutivos de PLA para Manufatura Aditiva e Moldagem por Injeção

Heliyon 8 2022 e10287 Contents lists available at ScienceDirect Heliyon journal homepage wwwcellcomheliyon Research article Development of electrically conductive hybrid composites with a polylactic acid matrix with enhanced toughness for injection molding and material extrusionbased additive manufacturing Roland Petrény Csenge Tóth Aurél Horváth László Mészáros a Department of Polymer Engineering Faculty of Mechanical Engineering Budapest University of Technology and Economics Műegyetem rkp 3 H1111 Budapest Hungary b ELKHBME Research Group for Composite Science and Technology Műegyetem rkp 3 H1111 Budapest Hungary ARTICLE INFO Keywords Nanocomposite Hybrid composite Carbon nanotubes Conductive composite Fused filament fabrication ABSTRACT In this study we developed electrically conductive nano and hybrid composites with a polylactic acid PLA matrix for different melt processing technologies We used short carbon fiber and multiwalled carbon nanotube reinforcements to enhance electric conductivity We prepared the composite compounds with twinscrew extrusion then the compounds were processed via injection molding and fused filament fabrication We showed that electric conductivity only slightly increased by when only carbon nanotubes were added to the PLA matrix However when carbon fibers were added to the nanocomposites the higher shear during melt mixing helped the uniform dispersion of the carbon nanotubes resulting in a highly conductive reinforcement network in the composite On the other hand the hybrid reinforcement resulted in higher viscosity making melt processing difficult and the material also became more brittle Therefore we added an oligomeric lactic acid plasticizer to the hybrid composites and produced specimens by injection molding and 3D printing The tensile strength increased by 140 and the elongation at break increased by 56 and at the same time the electrical conductivity of the material remained at a high level 1 Introduction The interest in electrically conductive polymers has constantly been growing in recent decades Dynamically developing sectors such as sensor manufacturing biomedical applications and the electronic industry sees their potential which justifies further research of these materials Although conductive polymers such as polyacetylene polypyrrole and poly34ethylene dioxythiophene have long been known it is difficult to process them with massproducing technologies This justifies the production of conductive polymer composites CPCs that can be processed with conventional technologies like melt compounding and injection molding In this case conductive particles are dispersed in the insulating polymer matrix These can form electrically conductive paths called percolations thereby increasing the electrical conductivity of the composite In addition to the electrically conductive polymer composites there is also a growing interest in biopolymers that can be produced from renewable resources or are biodegradable These offer a possible alternative to conventional petroleumbased polymers Most popular biopolymers is polylactic acid PLA whose monomer can be produced by the fermentation of renewable sources such as cellulose or other materials containing polysaccharide Due to its biocompatibility there is a growing interest in its medical applications in medical implants tissue engineering orthopedic devices etc PLA has poor electrical conductivity 332 10 Scm similarly to other unfilled polymers therefore the use of conductive fillers and reinforcements is intensively researched Due to their excellent electrical conductivity 10 Scm carbon nanotubes CNTs are recently used as conductive fillers Furthermore due to their excellent mechanical physical and chemical properties CNT is one of the most researched nanoparticles in recent decades However carbon nanotubes should be uniformly dispersed in the matrix to improve conductivity considerably If they are not dispersed properly the increment in conductivity is minimal For example Wang et al used polyethylene oxide as a binder for CNTs which helped them to prepare welldispersed PLACNT composites They showed that the electrical conductivity of the composites improved by two orders of magnitude in case of better dispersion The importance of dispersion for electrical Corresponding author Email address meszarosptbmehu L Mészáros httpsdoiorg101016jheliyon2022e10287 Received 18 July 2022 Received in revised form 2 August 2022 Accepted 10 August 2022 24058440 2022 The Authors Published by Elsevier Ltd This is an open access article under the CC BY license httpcreativecommonsorglicensesby40 R Petrény et al Heliyon 8 2022 e10287 Table 1 Reinforcement content of the composite samples Name PLA wt CNT wt CF wt OLA2 wt PLA 10000 000 000 000 PLA025CNT 9975 025 000 000 PLA05CNT 9950 050 000 000 PLA075CNT 9925 075 000 000 PLA1CNT 9900 100 000 000 PLA30CF 7000 000 3000 000 PLA30CF025CNT 6975 025 3000 000 PLA30CF05CNT 6950 050 3000 000 PLA30CF075CNT 6925 075 3000 000 PLA30CF1CNT 6900 100 3000 000 PLA30CF075CNT10OLA 5900 100 3000 1000 conductivity is also emphasized in the work of Wang et al in which an outstanding 722 Sm electrical conductivity have been achieved for PLACNT composites We investigated the effect of nanoparticles such as carbon black CB and multiwalled carbon nanotubes MWCNTs in the PLA matrix They increased the conductivity of the composites in different degrees 113 Scm for MWCNTPLA and 01 Scm for CBPLA prepared by material extrusionbased additive manufacturing and 0125 Scm for CBPLA prepared by hot pressing Graphene nanoplatelets have also been used for PLA matrix in literature with varying results 67 10 Scm to 242 Scm When the nanoparticles are dispersed well they also increase tensile strength and modulus However elongation decreases as the amount of nanoparticles increases which is not desirable for the inherently brittle PLA Based on our previous studies the dispersion of CNT can be significantly improved with the addition of a microsized conductive filler eg carbon fiber CF during compounding In this case other shear forces are formed in the melt due to the presence of CF which help to disperse the fillers uniformly In addition to the fact that nanoscale percolations of properly distributed CNTs already significantly increase electrical conductivity additional microscale percolations are formed through the carbon fibers Also there is a synergistic effect between nanoscale percolations produced by CNTs and microscale percolations produced by carbon fibers Since microscale conductive paths form connections between nanoscale percolations nanoscale paths form connections between the microsized carbon fibers thereby increasing electrical conductivity The high viscosity requires higher injection pressure and may lead to a lower degree of mold filling in injection molding or may lead to melt flow instability in the case of extrusion As there is a growing demand for customizable products fused filament fabrication has come to the fore where melt viscosity has an even more important role due to the very narrow printing nozzle A commonly encountered defect of composite 3D printing is the clogging of the nozzle which is often experienced above 20 wt fiber content Therefore the melt viscosity of hybrid composites should be kept at a low level so that the material is melt processable Figure 1 Preparation of the hybrid electrically conductive composites and plasticization for processability Figure 2 Production of tensile samples by injection molding and fused filament fabrication R Petrény et al Heliyon 8 2022 e10287 Figure 3 Melt flow index MFI of the nano and the hybrid composites Figure 4 Electrical conductivity of the nano and the hybrid composites In the past few years oligomeric lactic acid OLA has been found to be an effective and environmentallyfriendly plasticizer and lubricant for PLA materials OLA plasticizers help the melt processing of the materials and increase the toughness and elongation at the break of the brittle PLA composites In this study we produced electrically conductive polymer composites with a biopolymer matrix using PLA CF and CNT The hybrid reinforcement has beneficial effects on the dispersion of the nanotubes and leads to an increase in electric conductivity However it makes the PLA matrix even more brittle and increases melt viscosity which makes the melt processing of the material difficult For this we use oligomeric lactic acid as a plasticizer and as a result the composite should be well processable via injection molding and fused filament fabrication The goal is to produce an easytoprocess electrically conductive material for injection molding and material extrusionbased additive manufacturing with enhanced toughness 2 Materials and methods PLA 4060D amorphous polylactic acid granules manufactured by NatureWorks LLC were used as a matrix material for the composites The multiwall CNT used as a nanoscale reinforcement is Nanocyl NC7000 by Nanocyl S A with a diameter of 95 nm a length of 15 μm and a specific surface area of 250300 m2g Panex 35 Chopped Pellet 95 of Zoltek Zrt was used as a fibrous reinforcement As a plasticizer Condensia Glyplast OLA2 was used The fibers had a diameter of 83 μm a length of 6 mm and a density of 181 gcm3 It was necessary to dry the PLA granules before processing A Faithful WGLL125 BE drying oven was used to dry the PLA granules for 4 h at 45 C The granules and the reinforcing materials were first dry mixed then compounded with an LTE 2644 twinscrew extruder manufactured by Labtech Engineering Co Ltd Screw speed was 25 rpm and zone temperatures were 180 C 190 C 190 C 190 C 190 C 200 C 200 C 200 C 200 C 200 C and 190 C The composition of the materials is shown in Table 1 The fibers formed during the continuous extrusion were passed through a cooling conveyor belt to an LZ120VS type granulator which produced 4 mm long granules Before injection molding the granules were dried as described above Specimens according to the EN ISO 5272 1999 standard were injection molded on an Arburg Allrounder Advance 270S 400170 injection molding machine with zone temperatures of 185 C 190 C 195 C 200 C 200 C a mold temperature of 25 C and an injection pressure of 1500 bar After determining the optimal mixture for conductivity processability was improved with an oligomeric lactic acid plasticizer OLA2 The PLA30CF075CNT composite was plasticized with 10 wt OLA2 based on a previous study To mix the OLA2 with the composite we fed the PLA30CF075CNT material into an LTE 2644 twinscrew extruder and preheated the OLA2 to 80 C and dosed it with a Labtech Figure 6 a tensile strength b elongation at break and c tensile modulus of the nano and hybrid composites LDF16 liquid dosing system The zone temperatures in the extruder were 180 C 190 C 190 C 190 C 190 C 200 C 200 C 200 C 200 C 200 C and 190 C and screw speed was 10 rpm Figure 1 shows a schematic summary of the preparation of the composites The filament forming during the extrusion had a diameter of 16518 mm and was directly applicable for 3D printing Samples were produced on a Craftbot desktop material extrusion printer with a nozzle temperature of 220 C a layer height of 04 mm and an infill rate of 100 To investigate the orientation dependence of electrical conductivity and tensile properties we manufactured two types of specimens with the printing orientation parallel to the longitudinal axis 0 and perpendicular to it 90 For the injection molding of the composite plasticized with OLA2 the extruded filament was used after granulating It was injection molded on an Arburg Allrounder Advance 270S 400170 injection molding machine with zone temperatures of 185 C 190 C 195 C 200 C 200 C a mold temperature of 25 C and an injection pressure of 1500 bar Figure 2 shows the equipment used and the samples prepared The melt flow index MFI of the materials was measured on a CEAST 7027000 capillary plastometer at 200 C and with a load of 216 N The granules made from the extruded filaments were used for the measurements A fourpin resistance meter with an Agilent 34970A data logger was used to measure electrical conductivity The specific resistance of the composite specimens was determined using Eqs 1 and 2 ρ πcln2R Ωcm 1 G 1ρ Scm 2 where ρ is the resistivity measured c is the thickness of the sample in cm R is the measured resistivity and G is electrical conductivity Tensile tests were carried out on at least five specimens for each material on a Zwick Z005 universal testing machine Germany according to EN ISO 527 The tensile moduli were determined with the linear regression line between the 005 and 025 displacement values Tensile speed was 2 mmmin and gauge length was 110 mm Density was measured with a Sartorius Quintix 125D type semimicro scale At least five samples for each material were tested in water at 226 C For the scanning electron microscope SEM images the samples were etched in a 5 moll NaOH solution for 1 h at 25 C and then sputtered with gold The images were made with a JEOL JSM6380LA scanning electron microscope 3 Results and discussion 31 Development of electrically conductive hybrid composites 311 MFI The melt flow index of the materials has a key role in their processability Figure 3 shows that adding only nanotubes to the PLA did not influence its viscosity However when 30 wt carbon fiber was added to it increasing nanotube content decreased MFI and increased viscosity If the carbon nanotubes are well dispersed in the matrix more polymer chains can entangle around them blocking their movement during melt processing However a large MFI makes melt processing difficult or even impossible especially where low viscosity is required injection molding 3D printing Figure 7 SEM images of ac the injectionmolded pure PLA de the injectionmolded PLA05CNT nanocomposite fi the injectionmolded PLA30CF composite jl the injectionmolded PLA30CF05CNT hybrid composite 312 Electrical conductivity The results of the electrical conductivity test are illustrated in Figure 4 The conductivity of the composites reinforced only with CNT remained approximately unchanged It is due to the aggregation of CNTs which reduces the number of CNTs involved in the formation of conductive pathways The conductivity of the hybrid composites reinforced with CNT and CF was already significantly higher than that of the CNTonly composites due to the presence of 30 wt CF With the addition of 05 and 075 wt CNT conductivity increased significantly reaching twice the conductivity of the CFonly composite 0355 Scm In addition to the nanoscale conductive paths formed by the contact of welldispersed CNTs Figure 8 Schematics of the microstructure of the composites and the direction of the measurement of electrical conductivity Table 2 Electrical conductivity of the plasticized composite Name Processing technology Electrical conductivity Scm PLA30CF075CNT100LA Injection molding 0229 Fused Filament Fabrication 0 0154 Fused Filament Fabrication 90 0046 Table 3 Tensile mechanical properties Manufacturing technology Specific tensile strength Nmkg Tensile modulus Nmkg Elongation at break Injection molding 820 28 81070 7415 121 0110 Additive manufacturing 0 351 46 107210 14126 047 0510 Additive manufacturing 90 235 17 65304 4917 037 0001 additional microscale tracks are created by the contact of CFs The two types of reinforcing materials thus help each others the conductivity as CFs help to connect the different nanoscale conductive pathways formed by the CNTs Figure 5 illustrates the development of conductive paths in the hybrid composites 313 Tensile properties The tensile properties of conducting polymers are very important These properties might vary depending on the chosen processing technology as different technologies in our case injection molding and 3D printing produce different microstructures Figure 6 shows the tensile test results for each composite The tensile strength of the nanocomposites increased up to a CNT content of 075 wt and then began to decrease Tensile modulus and elongation at break remained almost constant regardless of reinforcement content The reason for these phenomena is the aggregation tendency of CNTs075 wt of CNT was still able to disperse in the PLA matrix properly during compounding but above this dispersion was not sufficient CNTs were then unable to produce their reinforcing effect and the aggregates which acted as stress concentrating centers contributed to failure For composites reinforced with 30 wt CF and CNT tensile strength and modulus and elongation at break decreased with increasing CNT Figure 9 SEM images of ac the injection molded and of df the 3D printed PLA30CF075CNT hybrid composite Printing direction CNTs connecting the carbon fibers content This means that an increased CNT content makes the composite brittle As a result even smaller defect sites and aggregates were sufficient for the appearance of cracks leading to failure This may be the reason for the decrease in tensile strength and elongation at break 314 SEM investigation Figure 7 shows the SEM images of the injection molded samples Large aggregates are visible on the SEM images of the PLA05CNT nanocomposite and between the large aggregates the few dispersed CNTs are not enough for good electrical connection In the PLA30CF composite the carbon fibers are well dispersed and randomly oriented causing them to cross each other making electrically conductive pathways In the hybrid composites the welldispersed nanotubes electrically contact the carbon fibers increasing electric conductivity 32 Increasing processability with OLA When the OLA plasticizer was added to the hybrid composite reinforced with 30 wt CF and 075 wt CNT MFI increased from 655 07 to 192 17 g10 min which is more than three times as much It means that the plasticizer decreased the viscosity and acted as a slip additive inside the material which facilitated the movement of the nano and microparticles in the melt The easier melt processability made it possible to process the composite via 3D printing The OLA plasticizer was added in a second extrusion step to the hybrid composite as the plasticizing effect of the OLA could have prevented the dispersion of the nanotubes 321 Electrical conductivity We performed conductivity tests again to investigate the effects of plasticization The plasticized hybrid composite was formed into a filament and was processable via 3D printing therefore we were able to examine the effects of printing orientation In material extrusionbased additive manufacturing the direction of melt deposition aligns the fibers thus the conductive paths as well which is expected to cause changes in conductivity as a function of printing direction Schematics of the hypothetical conductive paths can be seen in Figure 8 This also means that electrical conductivity can be tailored to demand within a single layer The results in Table 2 show that in the case of the 3D printed samples the electrical conductivity measured parallel to the printing direction 0 is more than three times the conductivity measured perpendicular to it 90 which meets our expectations and also aligns with the literature 30 The difference in electrical conductivity between the injection molded and the 3D printed samples may be due to voids in the 3D printed structures 322 Tensile properties Table 3 shows the tensile mechanical properties of the plasticized hybrid composites As the void content of the 3Dprinted samples have a significant effect on mechanical behavior we provide densityspecific values 31 When OLA2 was added to the PLA30CF075CNT composite tensile strength elongation at break and tensile modulus became nearly the same as those of the 30CF only composite This means that in the PLA30CF075CNT100LA composite the plasticizer counteracted the embrittling effect of the carbon nanotubes while not reducing electric conductivity compared to PLA30CF075CNT This is of great importance as the embrittling effect of conductive additives have rarely been addressed in literature where most often the elongation at break is reduced to about twothirds 12 323 SEM investigation In the injectionmolded samples Figure 9 ac the fibers are randomly oriented and intersect at several points creating an electrically conductive pathway Similarly to the unplasticized sample the carbon nanotubes are well dispersed increasing the electric conductivity by making more electric connections between the carbon fibers In the 3D printed samples Figure 9 df the carbon fibers are oriented in the printing direction so that they intersect at far fewer points and are less able to form a conductive network The electrical connection caused by the dispersed CNTs between the carbon fibers provides good electrical conductivity even in highly oriented composites 4 Conclusions In this study we developed electrically conductive nano and hybrid composites with a polylactic acid PLA matrix for different melt processing technologies Electric conductivity only slightly increased when carbon nanotubes were added to the PLA matrix When carbon fibers were added to the nanocomposites the higher shear during melt mixing helped the uniform dispersion of the carbon nanotubes which greatly increased the conductivity of the composite On the other hand the micro and nanoscale hybrid reinforcement greatly increased viscosity making melt processing difficult The hybrid composite also became brittle and the cracks in it propagated faster under a smaller load This decreased tensile strength and elongation at break Viscosity decreased when an oligomeric lactic acid plasticizer was added to the hybrid composites resulting in easier processability either by injection molding or 3D printing In addition the composite became more ductile the tensile strength and the elongation at break increased while the electrical conductivity decreased only slightly Declarations Author contribution statement Roland Petrény Conceived and designed the experiments Performed the experiments Analyzed and interpreted the data Contributed reagents materials analysis tools or data Wrote the paper Csenge Tóth Performed the experiments Analyzed and interpreted the data Wrote the paper Aurél Horváth Performed the experiments Analyzed and interpreted the data László Mészáros Conceived and designed the experiments Wrote the paper Funding statement This work was supported by the National Research Development and Innovation Office Hungary 2018131VKE201800001 and OTKA FK134336 and by the ItalianHungarian bilateral agreement grant number NKM732019 of the Hungarian Academy of Sciences The research reported in this paper is part of project no BMENVA02 implemented with the support provided by the Ministry of Innovation and Technology of Hungary from the National Research Development and Innovation Fund financed under the TKP2021 funding scheme László Mészáros is thankful for János Bolyai Research Scholarship of the Hungarian Academy of Sciences and for the ÚNKP215 New National Excellence Program of the Ministry for Innovation and Technology Data availability statement Data included in articlesupplementary materialreferenced in article Declaration of interests statement The authors declare no conflict of interest Additional information No additional information is available for this paper 7 References 1 D Kumar R Sharma Advances in conductive polymers Eur Polym J EUR POLYM J 34 1998 10531060 2 J Chen Y Zhu J Huang J Zhang D Pan J Zhou JE Ryu A Umar Z Guo Advances in responsively conductive polymer composites and sensing applications Polym Rev 61 2021 157193 3 G Kaur R Adhikari P Cass M Bown P Gunatillake Electrically conductive polymers and composites for biomedical applications RSC Adv 5 2015 3755337567 4 APB Silva LS Montagna FR Passador MC Rezende AP Lemes Biodegradable nanocomposites based on PLAPHBV blend reinforced with carbon nanotubes with potential for electrical and electromagnetic applications Express Polym Lett 15 2021 9871003 5 M Murariu P Dubois PLA composites from production to properties Adv Drug Deliv Rev 107 2016 1746 6 JM Raquez Y Habibi M Murariu P Dubois Polylactide PLAbased nanocomposites Prog Polym Sci 38 2013 15041542 7 MA Elsawy KH Kim JW Park A Deep Hydrolytic degradation of polylactic acid PLA and its composites Renew Sustain Energy Rev 79 2017 13461352 8 TF da Silva F Menezes LS Montagna AP Lemes FR Passador Preparation and characterization of antistatic packaging for electronic components based on polylactic acidcarbon black composites J Appl Polym Sci 136 2019 47273 9 B Earp D Dunn J Phillips R Agrawal T Ansell P Aceves I De Rosa W Xin C Luhrs Enhancement of electrical conductivity of carbon nanotube sheets through copper addition using reduction expansion synthesis Mater Res Bull 131 2020 110969 10 A Alipour T Giffney R Lin K Jayaraman Effects of matrix viscosity on morphological and rheological properties and the electrical percolation threshold in grapheneepoxy nanocomposites Express Polym Lett 15 2021 541553 11 Y Wang P Wang Z Du C Liu C Shen Y Wang Electromagnetic interference shielding enhancement of polylactic acidbased carbonaceous nanocomposites by polyethylene oxideassisted segregated structure a comparative study of carbon nanotubes and graphene nanoplatelets Adv Compos Hybrid Mater 5 2022 209219 12 Y Wang C Yang Z Xin Y Luo B Wang X Feng Z Mao X Sui Polylactic acid carbon nanotube composites with enhanced electrical conductivity via a twostep dispersion strategy Compos Commun 30 2022 101087 13 RH Sanatgar A Cayla C Campagne V Nierstrasz Morphological and electrical characterization of conductive polylactic acid based nanocomposite before and after FDM 3D printing J Appl Polym Sci 136 2019 47040 14 J Guo CH Tsou Y Yu CS Wu X Zhang Z Chen T Yang F Ge P Liu MR De Guzman Conductivity and mechanical properties of carbon blackreinforced polylactic acid PLACB composites Iran Polym J 30 2021 12511262 15 A Paydayesh SR Mousavi S Estaji HA Khonakdar MA Nozarinya Functionalized graphene nanoplateletspoly lactic acidchitosan nanocomposites mechanical biodegradability and electrical conductivity properties Polym Compos 43 2022 411421 16 N Wang X Zhang X Ma J Fang Influence of carbon black on the properties of plasticized polylactic acid composites Polym Degrad Stabil 93 2008 10441052 17 R Petrény L Mészáros Moisture dependent tensile and creep behaviour of multiwall carbon nanotube and carbon fibre reinforced injection moulded polyamide 6 matrix multiscale composites J Mater Res Technol 16 2022 689699 18 L Mészáros R Petrény The effect of microstructure on the dynamic mechanical properties of carbon fiber and carbon nanotube reinforced multiscale composites with a polyamide 6 matrix IOP Conf Ser Mater Sci Eng 2020 903 19 R Petrény L Almásy L Mészáros Investigation of the interphase structure in polyamide 6matrix multiscale composites Compos Sci Technol 225 2022 109489 20 W Thongruang RJ Spontak CM Balik Bridged double percolation in conductive polymer composites an electrical conductivity morphology and mechanical property study Polymer 43 2002 37173725 21 G Pal S Kumar Multiscale modeling of effective electrical conductivity of short carbon fibercarbon nanotubepolymer matrix hybrid composites Mater Des 89 2016 129136 22 L Satin J Bílik Impact of viscosity on filling the injection mould cavity Res Pap Fac Mater Sci Technol Slovak Univ Technol 24 2016 23 S Krizsma NK Kovács JG Kovács A Suplicz Insitu monitoring of deformation in rapid prototyped injection molds Addit Manuf 42 2021 102001 24 J Sang S Han Z Li X Yang W Hou Development of short basalt fiber reinforced polylactic composites and their feasible evaluation for 3D printing applications Compos B Eng 164 2019 629639 25 HL Tekinalp V Kunc GM VelezGarcia CE Duty LJ Love AK Naskar CA Blue S Ozcan Highly oriented carbon fiberpolymer composites via additive manufacturing Compos Sci Technol 105 2014 144150 26 PA Kumar Jain S Sattar D Mulqueen D Pedrazzoli SG Kravchenko OG Kravchenko Role of annealing and isostatic compaction on mechanical properties of 3D printed short glass fiber nylon composites Addit Manuf 51 2022 102599 27 D Lascano G Moraga J IvorraMartinez S RojasLema S TorresGiner R Balart T Boronat L QuilesCarrillo Development of injectionmolded polylactide pieces with high toughness by the addition of lactic acid oligomer and characterization of their shape memory behavior Polymers 11 2019 28 R Avolio R Castaldo G Gentile V Ambrogi S Fiori M Avella M Cocca ME Errico Plasticization of polylactic acid through blending with oligomers of lactic acid effect of the physical aging on properties Eur Polym J 66 2015 533542 29 T Tábi T Ageyeva JG Kovács Improving the ductility and heat deflection temperature of injection molded Polylactic acid products a comprehensive review Polym Test 101 2021 107282 30 I TiradoGarcia D GarciaGonzalez S GarzonHernandez A Rusinek G Robles JM MartinezTarifa A Arias Conductive 3D printed PLA composites on the interplay of mechanical electrical and thermal behaviours Compos Struct 265 2021 113744 31 MM Hanon R Marczis L Zsidai Influence of the 3D printing process settings on tensile strength of PLA and HTPLA Period Polytech Mech Eng 65 2021 3846 8 Título da postagem centralizado em negrito fonte Arial e tamanho 11 Sumário O resumo deverá conter uma breve introdução de no máximo 3 linhas com aspectos gerais sobre o tema com formatação justificada fonte Arial e tamanho 11 Texto O texto deverá ser escrito com fonte Arial justificado e tamanho 11 Imagens poderão ser adicionadas com as devidas referências Referência As referências deverão seguir o seguinte padrão A Lee A R Hudson D J Shiwarski J W Tashman T J Hinton S Yerneni J M Bliley P G Campbell A W Feinberg 3D bioprinting of collagen to rebuild components of the human heart Science 2019 365 6452 482 DOI 101126scienceaav9051 Redação Inserir o nome de quem 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