Macromolecules · 2001 · 60 citations · 16 references
Natural SciencesMaterials EngineeringMaterials SciencePolymer ChemistryPolymer EngineeringPolymer MaterialsAcrylic Resin MaterialsDegree Of ConversionPolymer DegradationPolymerization KineticsPolymerization StressPost-cure PolymerizationLight-curing MechanismsMonomer FunctionalityPolymerization-induced StressStress Development KineticsStress GrowthStress Growth BehaviorVitrificationVitrification Behavior
Polymerization kinetics and stress development were measured during UV curing of multifunctional acrylate and methacrylate coatings using photodifferential scanning calorimetry and a cantilever deflection method. Higher light intensity increases double‑bond conversion but also raises stress, higher monomer functionality and methacrylate substitution lower conversion and raise stress, whereas longer chains and more plasticizer increase conversion and lower stress, and stress only begins to develop late at vitrification and then rises monotonically with conversion, with the growth rate higher for more rigid networks, reflecting an increase in elastic modulus.
Polymerization kinetics and stress development were measured during the UV curing of multifunctional acrylate and methacrylate coatings by photodifferential scanning calorimetry and a cantilever deflection method. Higher light intensity leads to higher double-bond conversion but unfortunately also to higher stress. Higher monomer functionality unfortunately leads both to lower conversion and to higher stress; substituting methacrylate for acrylate does likewise. Longer monomer chain length and more plasticizer, though, lead both to higher conversion and to lower stress. In all cases, it is shown that significant stress starts to develop only late in reactionat the vitrification conversion. The vitrification conversion falls as more rigid networks are formed (with higher functionality, shorter monomer chain length, lower plasticizer concentration, or methacrylate rather than acrylate), but it is not affected by the light intensity. After vitrificationin the vitrified statethe stress rises monotonically with conversion. The rate of stress growth with conversion in the vitrified state rises with higher monomer functionality, shorter monomer chain length, or lower plasticizer concentration. It also rises when methacrylate is substituted for acrylate. These trends of stress growth in the vitrified state are consistent with an increase in the elastic modulus as more rigid networks are formed.
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