Stereolithographic 3D Printing with Renewable Acrylates

Summary

A protocol for additive manufacturing with renewable photopolymer resins on a stereolithography apparatus is presented.

Abstract

The accessibility of cost-competitive renewable materials and their application in additive manufacturing is essential for an efficient biobased economy. We demonstrate the rapid prototyping of sustainable resins using a stereolithographic 3D printer. Resin formulation takes place by straightforward mixing of biobased acrylate monomers and oligomers with a photoinitiatior and optical absorber. Resin viscosity is controlled by the monomer to oligomer ratio and is determined as a function of shear rate by a rheometer with parallel plate geometry. A stereolithographic apparatus charged with the biobased resins is employed to produce complex shaped prototypes with high accuracy. The products require a post-treatment, including alcohol rinsing and UV irradiation, to ensure complete curing. The high feature resolution and excellent surface finishing of the prototypes is revealed by scanning electron microscopy.

Introduction

Rapid prototyping enables on-demand production and design freedom and allows the efficient manufacturing of 3D constructs in a layer-by-layer manner¹. As a result, 3D printing as a fabrication technique has developed rapidly in recent years². Various technologies are available, all relying on the translation of virtual models into physical objects, and applying processes such as extrusion, direct energy deposition, powder solidification, sheet lamination and photopolymerization. The latter involves stepwise UV curing of liquid photopolymer resins. In 1986, Hull and co-workers developed the stereolithography apparatus (SL....

Protocol

CAUTION: Please consult all relevant material safety data sheets (MSDS) before use.

1. Preparation of Photocurable Resin

NOTE: Please use personal protective equipment (safety glasses, gloves, lab coat) during the following procedure. See our previous work¹² for more details on this section.

1. Pour 50 g of 1,10-decanediol diacrylate (SA5201) in a 500 mL Erlenmeyer flask.
2. Add 1.0 g of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) and 0.40 g of 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene (BBOT) to the flask.
3. Equip the flask with a me....

Results

Four representative resin compositions are displayed in Table 1, along with their average biobased carbon content (BC) derived from the individual BC of the components. The resin viscosity (Figure 1) is influenced by the ratio of acrylate monomers and oligomers and typically demonstrates Newtonian behavior. The mechanical properties of parts manufactured from various resins were determined by stress-strain analysis. Figur.......

Discussion

Additive manufacturing is applied in fabrication of tailor-made prototypes and small series, when the higher production costs per part can compete with conventional processes since there is no need for production of molds and tools. In the last decade, the revenues from services and products related to additive manufacturing have grown exponentially¹³. The largest fraction of material sales is from photopolymers. The growth attracted attention and initiated the investments of major industries,

Materials

Name	Company	Catalog Number	Comments
Isobornyl acrylate	Sartomer	SA5102	Acrylate monomer
1,10-decanediol diacrylate	Sartomer	SA5201	Acrylate monomer
Pentaerythritol tetraacrylate	Sartomer	SA5400	Acrylate monomer
Multifunctional epoxy acrylate	Sartomer	SA7101	Acrylate oligomer
Diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO), 97%	Sigma Aldrich	415952	Photoinitiator
2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene (BBOT), 99%	Sigma Aldrich	223999	Optical absorber
Isopropyl alcohol (IPA), 99%	Bleko	1010500	For alcohol bath (applied in Form Wash)
Paar Physica MCR300	Anton Paar	-	Rheometer with parallel plate geometry
Form 2 Printer	Formlabs	-	Desktop SLA 3D printer
Form Wash	Formlabs	-	Washing station
Form Cure	Formlabs	-	UV oven
Instron 4301 1KN Series IX	Instron	-	Universal testing machine
Philips XL30 ESEM-FEG	Philips	-	Scanning electron microscope