Development of acrylate-based material using a multivariable approach: additive manufacturing applications

Abstract

Purpose -Over the last several years, the range of applications for the photopolymerisation process has been steadily increasing, especially in such areas as rapid prototyping, UV inks, UV coats and orthodontic applications. In spite of this increase, there are still several challenges to be overcome when the application concerns materials formulation and their mechanical properties. In this context, the main aim of this work is to outline the contribution of the formulation components for the parameters of the photopolymerisation process and the resultant mechanical properties of the material. Design/methodology/approach -For this research, the authors have applied multivariable analysis methods, which allow the identification of principal conclusions based on experimental results. For the experimental analysis, the authors applied design of experiment, while the material formulation was based on methyl methacrylate as a monomer, Omnrad 2500 as a photoinitiator and trimethylolpropane triacrylate as an oligomer. The authors analysed the photopolymerisation rate, viscosity, mechanical tensile strength, flexural stiffness and softening. These results comprise a multiobjective optimisation study to identify the ideal material formulation for additive manufacturing applications. The values chosen for the materials were the following: the initiator concentration was 2 and 5% wt., the monomer volume was 5 and 10 ml and the oligomer volume was 3 and 5 ml. To analyse the system kinetics and the photopolymerisation rate, the authors identified the polymer conversion rate through a photometric-cumgravimetric method with a wavelength of 390 nm at the peak intensity. For the softening test, the authors identified the stiffness of the material as a function of temperature, characterising the thermal-mechanical behaviour of the material and determining its degree of crystallinity (cross-linking). Additionally, the authors performed an optimisation to maximise the mechanical tensile strength, flexural stiffness, softening temperature and photopolymerisation rate while minimising the viscosity. Findings -Based on these studies, it was possible to identify the influence of the monomer/oligomer ratio and the initiator concentration as function of polymerisation rate, viscosity, mechanical tensile strength, stiffness and softening of the material. It was also possible to determine the photopolymerisation rate in addition to the constants of propagation and termination. As a result of these studies, the authors identified a material formulation that resulted in a softening temperature greater than 708C, while the viscosity of material remained lower than 3 cP. The mechanical ultimate tensile strength was between 10 and 50 MPa, and the stiffness was between 1.6 and 5.8 GPa. The effect of cross-linking on the process highlighted the interaction between the monomer/oligomer ratio and the initiator. The contribution of the initiator and the inhibitor to the polymerisation rate was identified via a numerical model, which allows the predi...

Toughening of photo-curable polymer networks: a review

“…8), Cunico and Carvalho found that photoinitiator (PI) concentration had a tremendous effect on both modulus and tensile strength. 154 Thus polymers cured for 20 minutes with 5 wt% PI (Omnirad 2500 from IGM) were on average 40% stiffer and half as strong as those cured with 2 wt% PI. Interestingly DBC for the polymer with 2 wt% PI was 90% after 60 seconds while the value was only 65% for the same polymer with 5 wt% PI.…”

Enhanced Mechanical and Thermal Properties of Stereolithography 3D Printed Structures by the Effects of Incorporated Controllably Annealed Anatase TiO2 Nanoparticles

“…Photopolymerization is the critical mechanism of SLA 3D printing technology, demonstrating superior performance in the manufacture of 3D objects with accuracy, rapid curing, and micro-nanoscale resolution [9][10][11]. Nowadays, the photopolymerization applications and their utilization among industries are striking as well as modest schemes involving polymer chemistry [12]. The working principle of SLA techniques has made it more conceivable to decrease the cost of the manufacturing processes with high-quality products [13].…”