01753nas a2200241 4500008004100000022001400041245006800055210006600123260000800189300001400197490000600211520100700217653003801224653001801262653001801280653001201298100002001310700002201330700001601352700001801368700002701386856009801413 2019 eng d a2637-610500aThree-dimensional printing with waste high-density polyethylene0 aThreedimensional printing with waste highdensity polyethylene cNOV a3157-31640 v13 a

Fused filament fabrication (FFF) three-dimensional (3D) printing of semicrystalline polymers such as high density polyethylene (HDPE) is challenging because crystallization-induced shrinkage of the filament, as it cools, results in stresses that warp the printed part and debond it from the print substrate. Here, we demonstrate that waste-derived HDPE can be successfully 3D printed by (i) blending with a small fraction (<0.5% by weight) of dimethyl dibenzylidene sorbitol (DMDBS) and (similar to 10%) linear low density polyethylene (LLDPE) and (ii) printing the object with a thin ``brim'' around it that is adhered to the print substrate using common polyvinyl acetate-based glue. We match our experimental results with FEM simulations that provide insight into the origin of the stresses developed during printing. Because HDPE forms a significant fraction of the plastic waste stream, conversion of waste-derived HDPE to 3D printing filament has important technological implications.

10a3d printing polyethylene printing10apolymer blend10aRecyclability10awarpage1 aGudadhe, Aniket1 aBachhar, Nirmalya1 aKumar, Anil1 aAndrade, Prem1 aKumaraswamy, Guruswamy uhttps://library.ncl.res.in/content/three-dimensional-printing-waste-high-density-polyethylene02470nas a2200229 4500008004100000022001400041245009700055210006900152260000800221300000800229490000700237520171300244653001601957653002701973653001202000100002202012700002002034700001602054700001802070700002702088856012502115 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 uhttps://library.ncl.res.in/content/3d-printing-semicrystalline-polypropylene-towards-eliminating-warpage-printed-objects02069nas a2200289 4500008004100000022001400041245013000055210006900185260000800254300001400262490000600276520112500282653001401407653001401421653001801435653001301453653001101466653001401477100001501491700002001506700002701526700002101553700001801574700003001592700003101622856012601653 2020 eng d a2637-610500aNanocellulose reinforced flexible composite nanogenerators with enhanced vibrational energy harvesting and sensing properties0 aNanocellulose reinforced flexible composite nanogenerators with  cJUL a2550-25620 v23 a

We report here enhanced vibration and pressure sensing properties of nanocellulose reinforced flexible composite piezoelectric nanogenerators (PENGs). Surface fluorinated nanocellulose crystals (FNC) were incorporated into poly(vinylidene fluoride) (PVDF) and electrospun into composite nanofibers. Incorporation of only 2 wt % FNC in PVDF resulted in a significant enhancement in pressure sensitivity with a very low detectable pressure limit of 10 Pa and a sensitivity of up to 18 mV/kPa. The composite PENGs also demonstrated very high sensitivity for forced continuous vibrations. 2FNC/PVDF composites resulted in an order of magnitude higher voltage response over neat PVDF for a given strain. When PENGs were mounted on a vacuum pump for transduction of mechanical vibrations into electrical energy, 2FNC/PVDF composite devices manifested similar to 3.8 times enhanced voltage output over neat PVDF and faster charging of a capacitor. The enhanced piezoelectric properties of PVDF/FNC nanocomposites could be attributed to the tailored interface between PVDF and nanocellulose and enhanced polarizability.

10aComposite10aNanofiber10apiezoelectric10apressure10aSensor10avibration1 aRam, Farsa1 aGudadhe, Aniket1 aVijayakanth, Thangavel1 aAherrao, Swapnil1 aBorkar, Vivek1 aBoomishankar, Ramamoorthy1 aShanmuganathan, Kadhiravan uhttps://library.ncl.res.in/content/nanocellulose-reinforced-flexible-composite-nanogenerators-enhanced-vibrational-energy