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In this research, three different techniques for melt impregnation of glass fiber bundles with polyamide 12 are assessed with the aim of creating a high strength and modulus material suitable for extrusion based additive manufacturing. Impregnation quality of three production techniques: “Pultrusion”, “PassivePin”, and “ActivePin” were analyzed using three methods: matrix material mass fraction (Mm) determination, scanning electron microscopy of composite fracture surfaces and optical microscopy of polished composite cross sections. Pultrusion material has an overall poor impregnation degree (Di) and fiber distribution and dispersion, the specimens lack mechanical strength and show fiber pull‐out due to the excessive voids in the matrix. The PassivePin material has a significantly higher Di and a better fiber distribution, which results in less voids in the matrix and limited fiber pull‐out. Finally, the ActivePin material scores significantly higher in Di and shows an excellent fiber distribution. As a consequence, very limited voids are observed and an even fracture surface without fiber pull‐out is obtained. It is concluded that the ActivePin technique would be a great choice for application in an extrusion‐based AM process, this method could allow for production of high strength and stiffness objects. POLYM. ENG. SCI., 58:601–608, 2018. © 2017 Society of Plastics Engineers

Purpose This study aims to evaluate and compare the macroscopic properties of commercial acrylonitrile-butadiene-styrene (ABS) processed by two different types of additive manufacturing (AM) machines. The focus is also on the effect of multiple closed-loop recycling of ABS. Design/methodology/approach A conventional direct-drive, Cartesian-type machine and a Bowden, Delta-type machine with an infrared radiant heating system are used to manufacture test specimens molded in ABS. Afterward, multiple closed-loop recycling cycles are conducted, involving consecutive AM (four times) and recycling (three times). The rheological, mechanical, morphological and physicochemical properties are investigated. Findings The type of machine affects the quality of the produced parts. The machine containing an infrared radiant system in a temperature-controlled chamber produces parts showing higher mechanical properties and filling fraction, although it increases the yellowing. Closed-loop recycling of ABS for AM is applicable for at least two cycles, inducing a slight increase in tensile modulus (ca. 5%) and in tensile strength (ca. 13%) and a decrease in the impact strength (ca. 14%) and melt viscosity. An increase in the filling fraction of the AM parts promotes an increase in tensile strength and tensile modulus, although it does not influence the impact strength. Furthermore, multiple closed-loop recycling does not affect the overall chemical structure of ABS. Practical implications Controlling the environmental temperature and using infrared radiant heating during AM of ABS improves the quality of the produced parts. Closed-loop recycling of ABS used in AM is feasible up to at least two recycling steps, supporting the implementation of a circular economy for polymer-based AM. Originality/value This study shows original results regarding the assessment of the effect of different types of AM machines on the main end-use properties of ABS parts and the influence of multiple closed-loop recycling on the characteristics of ABS fabricated by the most suited AM machine with an infrared radiant heating system and a temperature-controlled environment.