Microgel formation and thermo‐mechanical properties of UV‐curing unsaturated polyester acrylates

Abstract

The effect of internal and terminal unsaturation on the properties of the acrylated polyester films was investigated. Four types of acrylated polyester resin were prepared using adipic acid, maleic anhydride, neopentyl glycol, trimethylolpropane, and acrylic acid. Terminal and internal double bond content as well as branching was adjusted by the molar quantities of trimethylolpropane and maleic anhydride, respectively. A reactive diluent, trimethylolpropane triacrylate (TMPTA), was also used. A three-factor, three-level Box-Behnken design was used to investigate complex nonlinear relationships. Dynamic mechanical, fracture toughness, and tensile properties were evaluated with respect to the amount of terminal and internal unsaturation, and reactive diluent concentration. It was found that microgel formation extensively affects the final UV-cured film properties. Small quantities of microgels function as micro-support units, whereas high extent of microgelation causes phase separation through cluster formation and hence, decreases the mechanical properties. It is essential to control the extent of microgelation and phase separation to optimize product performance.

Phase distribution changes of neat unsaturated polyester resin and their effects on both thermal stability and dynamic‐mechanical properties

“…The morphology was heterogeneous, composed by a phase rich in crosslinked UP (UP rich ) embedded in a less crosslinked phase rich in PS (ST rich ) 34 . The UP rich domains can be assigned to microgels generated by nanophase separation during the curing reaction 25,35 …”

“…It was calculated using Equation where R is the universal gas constant, E' is equilibrium storage modulus in the rubber zone achieved using dynamic‐mechanical analysis (DMA) measurements, and is the absolute temperature in the rubber zone calculated as 40°C in order to ensure the plateau zone 16,25 …”

Influence of Branching on Network Formation and the Thermomechanical Properties of UV-Curable Polyester Powder Coating Resins

“…The breadth of the α-relaxation is closely related to the heterogeneity of a polymer network . Previous studies have shown that polyfunctional crosslinkers and highly branched systems tend to afford more heterogeneous networks due to the formation of microgels and phase separation. − These densely crosslinked regions are undesirable because they can act as defect sites that negatively impact the mechanical properties of the film. Here, no significant changes were observed in the height or the breadth of the α-relaxation, suggesting that homogeneous crosslinked networks were obtained, regardless of the extent of branching.…”

The potential of unsaturated polyesters in biomedicine and tissue engineering: Synthesis, structure-properties relationships and additive manufacturing

“…In a subsequent work, the authors [46] used the same type of UPs to obtain UV-cured films and studied how the extent of microgelation affected the viscoelastic, fracture and tensile properties of the films. The results demonstrated that when the microgelation occurred in a low extent, the microgels acted as micro-support units enhancing the mechanical properties.…”