Four processing parameters, layer thickness, printing speed, raster angle, and building orientation were investigated in terms of their effects on mechanical properties, surface quality, and microstructure of acrylonitrilebutadiene-styrene (ABS) samples in fused deposition modeling (FDM) by orthogonal experiments. The results show that both the building orientation and the printing layer thickness have a great influence on the mechanical properties of ABS specimens. When the layer thickness is 0.1 mm, samples printed in horizontal direction have the best mechanical performance. The vertical-direction-built parts generally have the worst tensile strength and impact resistance. Moreover, the layer surface quality of the products becomes worse with the increasing of layer thickness and printing speed. The influence of layer thickness on the roughness of FDM samples is still very significant. These researches are of great significance to explore the FDM molding mechanism and optimize processing parameters to meet the performance demands. POLYM. ENG. SCI., 00:000-000, 2018. FIG. 7. SEM images of ABS tensile specimens fractured surfaces (The number indicates the group number in the orthogonal experiments.).

Fused deposition modeling (FDM) is one of the trendiest three-dimensional printing (3DP) technologies. However, FDM products based on virgin polyamide-6 (PA6) are seriously warped due to the accumulation of shrinkage stress generated from the crystallization of PA6. To solve this problem, maleic anhydride grafted poly(ethylene 1-octene) (POE-g-MAH) is added into PA6 to disturb the crystallization and reduce the shrinkage stress. Besides, rigid polystyrene (PS) with good flowability is further introduced to PA6/POE-g-MAH blend because too much addition of POE-g-MAH will weaken the PA6/POE-g-MAH, which will interrupt the printing process. The POE-g-MAH and PS both act as amorphous phase in the blends, which will reduce the shrinkage stress and is helpful to the shape stability of the printed products. Finally, a new kind of PA6-based filament with good toughness for FDM is prepared via this facile method.

Acrylonitrile-butadiene-styrene (ABS) nanocomposite filaments with different inorganic nanofillers for fused deposition modeling (FDM) were prepared by melting extrusion and printed via a commercial FDM three-dimensional printer. The effects of the nanoparticles on the mechanical strength, anisotropy, and thermal properties of the ABS specimens were evaluated. The performances of the virgin ABS samples manufactured by FDM and injection molding were also studied. The results show that the tensile strength (TS) of the pure ABS made by FDM was just up to 70% of the value obtained from the injection-molded specimens. The mechanical anisotropy of the pure ABS samples was very evident when the building orientation was changed. However, we found that the addition of nanofillers significantly reduced the mechanical anisotropy and improved the mechanical strength and thermostability of the ABS samples fabricated by FDM technology. The TS and flexural strength of the ABS samples increased by 25.7 and 17.1%, respectively, with the introduction of nanomontmorillonite. The addition of nano calcium carbonate lowered the mechanical anisotropy of ABS from 42.1 to 23.9%.

High thermally stable cellulose nanocrystals (CNCs), prepared by acid hydrolysis, were obtained by combination of alkali treatment (label as CNCs) and mixing with poly(ethylene oxide) (PEO). Dry mixture of PEO/CNCs (oCNCs) was subsequently introduced into poly(lactic acid) (PLA) matrix by melt extrusion and then compatibilizing with maleated PLA. The effects of compatibilization with maleated PLA (PLA-g-MAH) on the structure and properties of PLA/PEO/ CNCs nanocomposites were investigated. PLA/PEO/ CNCs/PLA-g-MAH nanocomposites displayed improved interfacial adhesion as compared to PLA/PEO/CNCs composites. Differential scanning calorimetry analysis showed enhanced crystallization ability for the resulting nanocomposites. The significant enhancement of thermal stability and tensile parameters, as strength and elongation at break were observed for the composites, which was primarily attributed to strong interfacial adhesion between filler and matrix and the uniform dispersion of CNCs. POLYM. marily attributed to strong interfacial adhesion between filler and matrix and the uniform dispersion of CNCs. POLYM. COMPOS., 39:3092-3101, 2018.

The preparation of 3D printed products with excellent comprehensive performance is still receiving much attention. Cellulose, the most abundant and green natural polymer, was used in this study to fabricate polymeric composites used for 3D printing. Specifically, novel cellulose nanocrystals/silica nanohybrids (CSNs) were synthesized via the sol-gel method using cellulose nanocrystals (CNCs) obtained by hydrolysis of sulfuric acid as raw materials, and the thermostability was significantly improved due to the adsorption of silica (SiO 2 ) on the surface of the CNCs via hydrogen bonding and covalent bonds. Subsequently, the CSNs were used in fused deposition modeling (FDM) with acrylonitrile-butadiene-styrene (ABS) as the matrix. Unlike ABS/CNC product which shows obvious yellowing, the ABS/CSN product shows a smooth undefiled surface, demonstrating their excellent applicability to high temperature FDM molding. Further, the effect of different silane coupling agents on the mechanical properties was compared and organically modified CSNs (oCSNs) were prepared using KH570 to optimize the dispersion of the filler and the interaction with the matrix. Satisfactorily, the addition of organically modified oCSNs not only does not degrade the fluidity but it also eliminates the warpage of FDM products and improves both layer adhesion and mechanical properties. This study provides a pioneering strategy for the thermal processing applications of CNCs and the modification of FDM products. RESULTS AND DISCUSSION Characterization of the CSNs Morphology and elemental analysis of the CSNsThe morphology and elemental analysis of the CNCs and the CSNs are shown in Fig. 2. Figure 2(a) demonstrates rod-like structures of the CNCs. Most of the CNCs possessed a length range of 100-500 nm and the diameters were a few nanometers, indicating that they had a large aspect ratio. Besides, the CNCs agglomerated together to form a bundle. CNCs are hydrophilic carbohydrate polymers with numerous hydroxyl groups and the strong Polym Int 2019; 68: 1351-1360