Cost-effective recycled resin for digital light processing 3D printing

Abstract

In this study, a new method was established to repeatedly recycle/reuse photocured acrylic resins in 3D printed products. Discarded 3D-printed dental models were ground into micrometer-size recycled powder by the ball milling process. The recycled resin prepared through planetary mixing can be printed into accurate models under low solid content (<30 per hundred kilograms of resin, phr), yet the poor reflowing property of higher solid content limits the amount of recovery. Further blending and de-aggregation by a high-shear-force three roller mill make the recycled resins exhibit great suspension stability over 3 days and in addition to low viscosity (<5 Pa s) for fine DLP printing. The recycled-resin-printed samples showed excellent accuracy (variation: x-y direction<1%, thickness<3%) with low roughness (<1 μm). In Comparing with printed objects from pristine resin, objects from 50 phr recycled resin possess a similar tensile strength of 30 MPa and a better compressive strength performance of 153 MPa. Moreover, the products from recycling studies using 50 phr resin retained great printing accuracy and preserved the same mechanical properties. The prepared recycled resin can also be directly used for the production of customized, detailed, and low-roughness dental models, demonstrating the potential of this recycling method for practical applications.