Additive manufacturing, also known as 3D printing, has quickly become a widely used tool for rapid prototyping of complex parts. Most of the common filaments for the fused filament fabrication form of 3D printing are inherently flammable thermoplastics, which has led to numerous fires that pose a serious danger to lives and property. In an effort to improve the safety of these filaments, a unique composite of polylactic acid (PLA) and a flame-retardant polyelectrolyte complex, consisting of polyvinylamine and poly(sodium phosphate), was developed. This composite filament can be printed using an ordinary 3D printer under identical conditions to neat PLA. The filament and its printed parts are selfextinguishing in an open flame test and exhibit a 42% lower peak heat release rate, as measured by microscale combustion calorimetry. This unique filament concept solves a major safety problem for 3D printing and could be extended to other commonly used polymer filaments.

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The J750 PolyJet printer is the newest model of full-color, multi-material 3D printer from Stratasys. Currently, limited information is available about the effects of control factors on mechanical properties such as elastic modulus, ultimate tensile strength, and elongation. In this study, the effects of two control factors, orientation and layer thickness, on mechanical properties of samples printed by the Stratasys J750 printer are investigated. The results show that orientation significantly affects mechanical properties. Specifically, samples printed with its axial direction parallel to the direction of printing have the highest elastic modulus, and elongation, whereas samples printed with its axial direction perpendicular to the direction of printing have the highest ultimate tensile strength. Also, layer thickness makes a significant difference for mechanical properties, and larger layer thickness leads to higher ultimate tensile strength and elongation. These results would be valuable to researchers and practitioners who use J750.

Purpose This paper aims to investigate the printability of photocurable PDMS with digital light processing (DLP) in terms of dimensional accuracy, mechanical properties, isotropy and postcure shrinkage. Design/methodology/approach The photocurable PDMS was made from methacrylated PDMS-macromer and 2,4,6-Trimethylbenzoyldi-Phenylphosphinate (TPO-L) photoinitiator. The PDMS was printed using different orientations, sizes and post-exposure conditions and then evaluated by tensile test and microscope to determine the printability. Findings Printed parts show good accuracy and low shrinkage, but high directionality in modulus, ductility and strength. The dimensional error is less than 2% and the shrinkage rates are less than 0.52%. In contrast, the modulus varies between 0.87 and 0.96 MPa depending on print orientation, elongation varies from 34.7% to 66.4% and strength varies from 0.23 to 0.49 MPa. Originality/value This study quantitatively characterizes the printability of photo curable PDMS with DLP, which has not been reported elsewhere. This paper also discusses the challenges of PDMS printing for future advancement.

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