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This study addresses the influence of build orientation and loading direction on the static and dynamic mechanical properties of three-dimensional-printed thermoplastic polyurethane-based lattice s...

The effect of technological conditions of the process and zirconia (ZrO(2)) nanoparticles on the properties of fine-fibrous filter materials (FMs) obtained by matrix polymer extraction from a microfibrillar composite formed using the material extrusion-based additive manufacturing method from a polypropylene (PP)/copolyamide blend is studied. Different processing schemes were used for obtaining filaments for material extrusion: scheme I—the use of a single-screw extruder at the stage of compounding; scheme II—the use of a single-screw extruder at the stage of compounding and orientational stretching in the course of strand formation; scheme III—the use of a twin-screw extruder at the stage of compounding, scheme IV—the addition of ZrO(2) nanoparticles and use of a twin-screw extruder. It has been shown the possibility of reducing the diameters of the formed in situ PP microfibrils by using the twin-screw extruder, as well as additional orientation drawing. The introduction into the melt of ZrO(2) nanoparticles provides further improvement of the microstructure—the average diameter of the microfibrils is reduced by 1.4 times compared with the initial blend. Developed FMs are characterized by high efficiency of air purification from solid particles with a size of 0.3 μm. At the same time, the use of nanoadditives is the most effective—a two-layer FM with nanoparticles provides cleaning efficiency at the level of four- to six-layer materials without filler.

This study addresses the mechanical behavior of lattice materials based on flexible thermoplastic polyurethane (TPU) with honeycomb and gyroid architecture fabricated by 3D printing. Tensile, compression, and three-point bending tests were chosen as mechanical testing methods. The honeycomb architecture was found to provide higher values of rigidity (by 30%), strength (by 25%), plasticity (by 18%), and energy absorption (by 42%) of the flexible TPU lattice compared to the gyroid architecture. The strain recovery is better in the case of gyroid architecture (residual strain of 46% vs. 31%). TPUs with honeycomb architecture are characterized by anisotropy of mechanical properties in tensile and three-point bending tests. The obtained results are explained by the peculiarities of the lattice structure at meso- and macroscopic level and by the role of the pore space.

This study addresses a new approach to production of multi-layer fine-fibrous filter material by application of material extrusion–based additive manufacturing (MEB-AM). By the example of polypropylene/copolyamide (PP/CPA), the ability of a fibrous composite structure formation in the initial strands is demonstrated. It is shown that a change in the size of filter grid cells and the extrusion pressure allows control of the diameter of PP fibrils. It is found that multi-layered composite films formed by MEB-AM of the strands retain the structure inherent in the strands. A polypropylene precision filter material has been produced by extraction of a matrix polymer from composite films. The achieved filter retention is about 100% (for the particles of 0.3–1.0 μm in size).

This study addresses the new approach into production of fiber-based hybrid composites, that is in-situ formation of polуmer fiber net out of polymeric matrix combined with simultaneous orientation of the foreign filler fibers. Such hybrid composite can consist of three and more components, including filler fibers, polуmer fibers and a non-oriented polymer matrix. This possibility is demonstrated with using the system of linear low-density polyethylene – basalt fibers (LLDPE/BFs). The hybrid effect (double Young's modulus, yield stress higher by the factor of 1.3, triple impact strength of LLDPE) is achieved owing to self-reinforcing process and enhancing of the interfacial interaction as a result of fiber orientation and formation of effective physical entanglements between the BFs and the net of interwoven LLDPE fibers.

The effect of orientation of the layers of the original structure of polymers produced by fused deposition modeling (FDM) on the reinforcing effect caused by succeeding equal channel multiple angular extrusion (ECMAE) is studied. As test objects, glassy acrylonitrile butadiene styrene copolymer (ABS), glycol-modified poly(ethylene terephthalate) (PET-G) and semicrystalline PET are selected, as well as layered composites ABS/PET and ABS/PET-G. It is demonstrated that ECMAE results in enhancement of microhardness, storage modulus, impact strength. The density, the glass transition temperature, the melting temperature are increased, too. The crystallinity degree of extrudates is enhanced. It is shown that an increment in the mechanical characteristics is better in the case of longitudinal position of the melt layers, as compared to the transversal one. The achieved effects are related to the pore healing, formation of orientation ordering, and enhanced interphase interaction and homogenization of the system in the course of production of layered composites of thermodynamically incompatible polymers. A physical model is suggested that describes the behavior of the layered materials under ECMAE. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45727.