02469nas a2200229 4500008004100000022001400041245009700055210006900152260000800221300000800229490000700237520171300244653001601957653002701973653001202000100002202012700002002034700001602054700001802070700002702088856012402115 2020 eng d a0250-470700a3D printing of semicrystalline polypropylene: towards eliminating warpage of printed objects0 a3D printing of semicrystalline polypropylene towards eliminating cJUL a1710 v433 a

Fused filament fabrication (FFF) is an extrusion-based 3D printing technique for thermoplastic polymers. In this technique, molten polymer is extruded through a print nozzle and is laid down layer by layer to build up the printed object. Currently, FFF is used primarily to print amorphous or low-crystallinity polymers, such as acrylonitrile butadiene styrene copolymer (ABS) or polylactic acid (PLA). Printing of semicrystalline polymers, such as polyethylene or polypropylene remains particularly challenging. During FFF of semicrystalline polymers, large thermomechanical stresses are generated when the polymer solidifies on cooling. These stresses result in warpage of the printed part. Here, we analyse the factors that influence stresses generated during FFF 3D printing of a commercial semicrystalline polymer, isotactic polypropylene. We investigate the effect of height of the printed object on part warpage, as well the effect of infilling during printing. We demonstrate that the stresses generated during FFF can be substantially decreased by incorporation of a `brim', viz. a thin layer at the base of the printed object, and by adhering the brim to the print substrate using common polyvinyl acetate-based glue. We systematically investigate the effect of the brim size on the warpage of the printed object. We support our experimental findings with finite element method (FEM) simulations that explain the mechanism of stress buildup during printing. The trend in stresses calculated in the FEM simulations parallel the warpage measured in the experiments. Thus, this work represents an important methodological advance towards warpage-free FFF printing of semicrystalline polymers.

10a3D printing10apolypropylene printing10awarpage1 aBachhar, Nirmalya1 aGudadhe, Aniket1 aKumar, Anil1 aAndrade, Prem1 aKumaraswamy, Guruswamy uhttp://library.ncl.res.in/content/3d-printing-semicrystalline-polypropylene-towards-eliminating-warpage-printed-objects02018nas a2200241 4500008004100000022001400041245009000055210006900145260000800214300001400222490000700236520121900243653001601462653001801478653001501496653003701511653001801548653002601566100001901592700001701611700003101628856011701659 2020 eng d a0032-388800aEnhancing the mechanical properties of 3D printed polylactic acid using nanocellulose0 aEnhancing the mechanical properties of 3D printed polylactic aci cAUG a1842-18550 v603 a

We report here a systematic investigation of the mechanical properties of polylactic acid (PLA) processed by fused filament fabrication (FFF) 3D printing vs PLA processed by compression molding. Our results show that the tensile strength and modulus of FFF-PLA is 49% and 41% lower, respectively, than compression molded samples of PLA. We also demonstrate here an approach to augment the mechanical properties of 3D printed PLA using nanocellulose. Incorporation of a small quantity (1 wt%) of cellulose nanofibers (CNF) was found to enhance the tensile strength and modulus of 3D printed PLA by 84% and 63%, respectively. X-ray microtomography was used to probe the morphology of 3D printed PLA and PLA/CNF composites. 3D printed PLA/CNF composites had significantly lesser voids as compared to neat 3D printed PLA. Differential scanning calorimetry study revealed that CNF can accelerate the nucleation and crystallization of 3D printed PLA leading to enhanced crystallinity. The thermal stability of 3D printed PLA/CNF composites was not compromised by the addition of CNF. The enhanced mechanical properties of 3D printed PLA/CNF composites can be ascribed to higher crystallinity and lesser defects.

10a3D printing10aBiocomposites10acomposites10afused filament fabrication (FFF)10aNanocellulose10apolylactic acid (PLA)1 aAmbone, Tushar1 aTorris, Arun1 aShanmuganathan, Kadhiravan uhttp://library.ncl.res.in/content/enhancing-mechanical-properties-3d-printed-polylactic-acid-using-nanocellulose01588nas a2200205 4500008004100000022001400041245010200055210006900157260000800226490000800234520086200242653001601104653002801120653002901148653001401177653002701191100001601218700001701234856013101251 2022 eng d a1022-135200aBiodegradable, solvent-free photocrosslinkable PLLA resin formulations for additive manufacturing0 aBiodegradable solventfree photocrosslinkable PLLA resin formulat cNOV0 v2233 a

Acrylate end-functionalized linear and star poly l-lactide (PLLA) based aliphatic, photocurable oligomeric crosslinkers are developed, which are formulated with hydroxyl (ethyl)methacrylate (HEMA) as a biodegradable reactive diluent to demonstrate successful application for solvent-less 3D printing using digital light processing (DLP) technique as well as a custom-designed direct ink writing 3D printer. The resin formulation for 3D printing is optimized using spot curing, photodifferential scanning calorimetry and cure depth analysis. The 3D printed parts exhibit promising mechanical property along with improved hydrophilicity and biodegradability. The development of new photocurable resin formulations are expected to meet the growing demand for raw materials that can be applied for developing custom designed bio implantable objects.

10a3D printing10abiodegradable materials10adigital light processing10aL-Lactide10aphotocurable materials1 aPal, Shibam1 aAsha, S., K. uhttp://library.ncl.res.in/content/biodegradable-solvent-free-photocrosslinkable-plla-resin-formulations-additive-manufacturing02602nas a2200229 4500008004100000022001400041245017500055210006900230260000900299300001100308490000800319520175500327653001602082653001602098653002802114653001802142653001702160100002302177700002802200700001702228856012702245 2023 eng d a0032-386100aDesign and synthesis of photocrosslinker and light blocker based on L-Amino acid polyester and their application in solvent-free resin formulation for DLP/SLA 3D printing0 aDesign and synthesis of photocrosslinker and light blocker based cMAR  a1257810 v2703 a

Customising material design for new technological applications like additive manufacturing (AM) is a challenging yet promising approach to create a palette of materials suitable for developing eco-friendly products. LGlutamic acid and L-aspartic acid based aliphatic, photocurable polyester crosslinkers were designed and developed and incorporated into a solvent-free photocurable resin formulation with hydroxyl (ethyl)methacrylate (HEMA). Proof-of-concept 3D printing of clear and transparent objects was demonstrated using digital light processing (DLP) and Stereolithography (SLA) techniques. Resolution of the 3D printed objects could be improved by incorporating a Dansyl labelled L-glutamic acid polyester, which not only aided in modulating the viscosity of the resin formulation but could also function as a light blocker, thereby avoiding polymerization of unwanted areas while 3D printing. The curing kinetics of the photocurable formulation was analyzed using photo differential Scanning Calorimetry. Enzymatic degradability studies of 3D printed films were undertaken in PBS buffer containing esterase enzyme and compared with 3D printed samples using HEMA and a commercial crosslinker (Trimethylolpropane triacrylate (TMPTA)). Scanning electron microscopy (SEM) was used to evaluate the morphology of the 3D printed films before and after enzymatic degradation in the PBS buffer for 60 days. The 3D printed amino acid crosslinked films of HEMA presented high degree of degradation in contrast to the near total absence of any degradation in the 3D printed film crosslinked using TMPTA. The availability of new photocurable formulations that are enzymatically degradable are highly sought after for 3D printing applications.

10a3D printing10aCrosslinker10aL -Amino acid Polyester10aLight blocker10aPhotocurable1 aKamble, Ganesh, N.1 aJoshi, Dheeraj, Chandra1 aAsha, S., K. uhttp://library.ncl.res.in/content/design-and-synthesis-photocrosslinker-and-light-blocker-based-l-amino-acid-polyester-and02308nas a2200313 4500008004100000022001400041245009600055210006900151260000800220300001400228490000700242520130500249653001601554653001401570653001701584653001801601653002201619653001401641100003101655700002001686700002601706700001701732700002301749700001901772700002001791700002901811700003101840856012301871 2023 eng d a0032-388800aLuminescent 3D printed poly(lactic acid) nanocomposites with enhanced mechanical properties0 aLuminescent 3D printed polylactic acid nanocomposites with enhan cJUL a2059-20720 v633 a

The three-dimensional (3D) printing of functional composite materials has gained tremendous interest in recent years. Nevertheless, research on 3D printing of luminescent composite materials is very limited, and the mechanical properties of such 3D-printed composites are poor. Herein, we report the preparation and characterization of a poly(lactic acid) (PLA) composite that, when 3D printed, exhibits enhanced toughness and high solid-state fluorescence quantum yield. Incorporation of only 1 wt% pyrene butyric acid modified cellulose nanofibers (PBA-m-CNF) and l0 wt% thermoplastic polyurethane (TPU) into PLA led to 223% increase in toughness and 21% increase in tensile modulus of PLA. Scanning electron microscopy (SEM) and X-ray microcomputed tomography (mu-CT) analysis of the fractured cross-sections of 3D printed composites revealed a ductile failure mode. The PLA/PBA-m-CNF1/TPU10 3D printed composite also exhibited a high solid-state fluorescence quantum yield of 38.35%. To the best of our knowledge, this is the first report to show both enhanced mechanical properties and high solid-state fluorescence emission for 3D printable PLA. Such functional PLA composites could have potential applications in the fabrication of complex-shaped sensors, optical light pipes, etc.

10a3D printing10aComposite10afluorescence10aNanocellulose10apoly(lactic acid)10atoughness1 aKothavade, Premkumar, Anil1 aYadav, Prashant1 aNidhankar, Aakash, D.1 aTorris, Arun1 aPol, Harshawardhan1 aKafi, Abdullah1 aBateman, Stuart1 aSukumaran, Santosh, Babu1 aShanmuganathan, Kadhiravan uhttp://library.ncl.res.in/content/luminescent-3d-printed-polylactic-acid-nanocomposites-enhanced-mechanical-properties02131nas a2200301 4500008004100000022001400041245011400055210006900169260000900238490000700247520111200254653001601366653002001382653000901402653002001411653000901431100002901440700001801469700002901487700002401516700002901540700002501569700001801594700002501612700003101637700003001668856013101698 2023 eng d a1861-472800aThermally activated delayed fluorescent solvent-free organic liquid hybrids for tunable emission applications0 aThermally activated delayed fluorescent solventfree organic liqu cJUL 0 v183 a

The synthetic feasibility and excellent luminescence features of organic molecules attracted much attention and were eventually found useful in lighting applications. In this context, a solvent-free organic liquid having attractive thermally activated delayed fluorescence features in bulk along with high processability has prime importance. Herein, we report a series of naphthalene monoimide-based solvent-free organic liquids exhibiting cyan to red thermally activated delayed fluorescence with luminescence quantum yields up to 80% and lifetimes between 10 to 45 mu s. An effective approach explored energy transfer between liquid donors with various emitters exhibiting tunable emission colors, including white. The high processability of liquid emitters improved the compatibility with polylactic acid and was used for developing multicolor emissive objects using 3D printing. Our demonstration of the thermally activated delayed fluorescence liquid will be much appreciated as a processable alternate emissive material suitable for large-area lighting, display, and related applications.

10a3D printing10aEnergy Transfer10aOLED10aOrganic Liquids10aTADF1 aNidhankar, Aakash, D. D.1 aGoudappagouda1 aKothavade, Premkumar, D.1 aDongre, Sangram, D.1 aVeer, Sairam, Dnyaneshwa1 aDash, Soumya, Ranjan1 aRajeev, Kavya1 aUnni, K., N. Narayan1 aShanmuganathan, Kadhiravan1 aBabu, Sukumaran, Santhosh uhttp://library.ncl.res.in/content/thermally-activated-delayed-fluorescent-solvent-free-organic-liquid-hybrids-tunable-emission