We have developed photocurable bio-derived isosorbide (meth)acrylates for use in photoinitiated additive manufacturing (AM). We have shown that the viscosity of isosorbide-based resins obeyed logarithmic rule of mixtures, and the viscosity values were significantly lower than that of commercial stereolithography (SLA) resins as well as various other urethane (meth)acrylates and
Vat photopolymerization additive manufacturing (Vat AM) technologies have found niche industrial use being able to produce personalized parts in moderate quantity. However, Vat AM lacks in its ability to produce parts of satisfactory thermal and mechanical properties for structural applications. The purpose of this investigation was to develop high-performance resins with glass transition temperatures (Tg) above 200 °C for Vat AM, evaluate the properties of the produced thermosets and establish a structure–property relationship of the thermosets produced. Herein, we have developed SLA-type resins that feature bio-derived monomer hesperetin trimethacrylate (HTM) synthesized from the flavonone hesperetin. Diluents 4-acryloyl morpholine, styrene, 4-methyl styrene and 4-tert butylstyrene (tbutylsty) were photocured with HTM as the monomer and all produced thermosets with Tg values above 200 °C. Investigations of suitable crosslinkers urethane dimethacrylate, the vinyl ester CN 151 and Ebecryl 4859 (Eb4859) showed that each crosslinker displayed different benefits when formulated with HTM as the monomer and tbutylSty as the diluent (HTM:crosslinker:tbutylSty with mass ratio 2:1:2). The crosslinker CN 151 produced the thermoset of greatest onset of thermal decomposition temperature (T0) of 352 °C. Eb4859 produced the thermoset of highest tensile strength, 19 ± 7 MPa, amongst the set of varied crosslinkers. The formulation featuring UDM (HTM:UDM:tbutysty) offered ease of processing and was seemingly the easiest to print. Investigations of reactive diluent showed that styrene produced the thermoset of the highest extent of cure and the overall highest tensile strength, 25 ± 5 MPa, while tbutylSty produced the thermoset with the greatest Tan-δ Tg, 231 °C. HTM was synthesized, formulated with diluents, crosslinkers and initiators. The HTM resins were then 3D printed to produce thermosets of Tg values greater than 200 °C. The polymer properties were evaluated and a structure–reactivity relationship was discussed.
Hesperetin based monomers substituted to varying degrees of methacrylate functionality were synthesized namely trimethacrylate, dimethacrylate and monomethacrylated hesperetin monomers, HTM, HDM and HMM respectively.Resins employing reactive diluents 4-acryloylmorpholine (4AM) and styrene (Sty) were formulated. Resin formulations were determined to be Newtonian fluids with viscosities below 800 cP. Thermosets of hesperetin monomers were produced with glass transition temperature (T g ) values up to 225 C. Ultimate strength up to 20 MPa and tensile modulus of 5.0 GPa were also observed. Additionally, thermosets with char yield near 30% were measured. Char yield, ultimate strength and tensile modulus of hesperetin based thermosets were superior to those derived from the petrochemical bisphenol A dimethacrylate (BPAM). However, thermosets that employed hesperetin derived monomers displayed properties that were less than expected compared to Bicerano model predictions.Also, select HTM:Sty thermosets displayed a noticeable holographic type morphology. Reactivity ratios, spectroscopy, microscopy and structure property relationships indicated that poor copolymerization behavior during cure and high degrees of crosslinking during postcure were responsible for the microcrack formation in the material. This also caused the observed morphology and resulted in reduced properties relative to Bicerano predictions.
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