Investigating Alternatives in Unsaturated Polyester Resins with Raman Spectroscopy due to Stricter Regulations
Stricter environmental and occupational health expectations are increasingly forcing markets to evaluate alternatives to established reactive diluents. During formulation testing, products prepared with alternative reactive diluents can exhibit poorer physical properties compared with the reference system, despite appearing fully cured at a macroscopic level. Raman spectroscopy can be applied to investigate curing chemistry at the molecular level and to identify possible structural reasons for the observed loss in material performance.
As expectations around emissions, exposure, and sustainability continue to evolve, companies developing coatings, composites and resins are increasingly required to evaluate alternative reactive diluents. Well established diluents are classified as reproduction toxic by ECHA and must be replaced in gel-coats for trains, busses, pools, etc. Formulations with alternative reactive diluents can lead to cured products that no longer exhibit the same mechanical or thermal properties, even when curing appears successful at a macroscopic level. Such deviations are difficult to resolve without understanding the underlying chemistry as it cannot be explained with established methods like rheometer and DSC alone. Alternative diluents may change the balance between copolymerization with the underlying backbone and self-reaction, leading to variations in crosslink density, network homogeneity, and residual unsaturation. By enabling bond-specific monitoring of polymerizable C=C double-bond consumption during cure, Raman analysis allows scientists to compare how conventional and alternative diluents interact with the unsaturated polyester resin.
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