How Is Rheology Involved in 3D Printing of Phase-Separated PVC-Acrylate Copolymers Obtained by Free Radical Polymerization

Abstract

New auto-plasticised copolymers of poly(vinyl chloride)-r-(acrylate) and polyvinylchloride, obtained by radical polymerization, are investigated to analyse their capacity to be processed by 3D printing. The specific microstructure of the copolymers gives rise to a phase-separated morphology constituted by poly(vinyl chloride) (PVC) domains dispersed in a continuous phase of acrylate-vinyl chloride copolymer. The analysis of the rheological results allows the suitability of these copolymers to be assessed for use in a screw-driven 3D printer, but not by the fused filament fabrication method. This is due to the high melt elasticity of the copolymers, caused by interfacial tension between phases. A relationship between the relaxation modulus of the copolymers and the interlayer adhesion is established. Under adequate 3D-printing conditions, flexible and ductile samples with good dimensional stability and cohesion are obtained, as is proven by scanning electron microscopy (SEM) and tensile stress-strain tests.

Importance of Polymer Rheology on Material Extrusion Additive Manufacturing: Correlating Process Physics to Print Properties

“…However, molecular interpretation of the results in terms of chain stretch and extent of disentanglement was not provided. Along similar lines, Peñas et al investigated the extrusion based AM of PVC/acrylate copolymers and found filament buckling to be a serious issue in FFF of the material . However, the polymer was still printable using a screw-based extrusion system and the associated viscoelastic and rheological characteristics to ensure interlayer welding was studied.…”

Rheology of Polymer Processing in Spain (1995–2020)

“…In the last 25 years, a number of Spanish papers [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ] have dealt with viscosity results of polymer melts related to their aptness for extrusion moulding. The article of Vega et al [ 7 ], the result of the collaboration between the University of the Basque Country and REPSOL, is the most cited among the Spanish papers properly focused on the rheology applied to polymer processing, according to the Web of Science.…”

“…Spanish rheologists have worked on the melt fracture of polypropylene [ 22 ], poly(styrene-ethylene/buthylene-styrene) triblock copolymers [ 24 ], and poly(vinyl chloride) (PVC) [ 31 ]. As a matter of fact, research on the rheology of PVC processing has gained a certain reputation thanks to the collaboration between the Spanish company ERCROS and the Rheology group of the University of the Basque Country [ 14 , 15 , 19 , 32 , 33 , 34 , 35 ]. The most recent of these papers focuses on the rheology applied to additive manufacturing, which is treated in Section 2.3 .…”

“…The collaboration between the University of the Basque Country (UPV/EHU) and the Spanish company ERCROS has given rise to a series of papers on the rheological aspects of the printability of PVC and PVC copolymers [ 32 , 34 , 35 ]. A rheological analysis for adequate printing, considering the pressure and printing velocities ranges of the printing device, is shown in the paper of Calafell et al [ 32 ].…”

“…The allowable printing conditions are delimited through viscosity measurements in the laboratory. Additionally, in the field of PVC derivates, Peñas et al [ 34 ] have proposed a rheological model to face the issue of buckling of the filament during the feeding process of the EAM devices.…”