Chemorheology of photopolymerizable acrylates using a modified Boltzmann sigmoidal model

Abstract

Experiments were conducted to evaluate the influence of ambient photoconversion on rheology for a range of photopolymerizable urethane dimethacrylate (UDMA) resins containing varying amounts of three comonomers including 1,6 hexane diol-dimethacrylate (HDDMA), an alkoxylated cyclohexane dimethanol diacrylate monomer (CD-582), and hydroxyethyl methacrylate (HEMA). Experiments were performed both as a function of composition and time-dependent dose varying the intensity using a photorheometer. A semilog-based sigmoidal model allowed the determination of four physical model parameters to define the relationship between reaction kinetics and its dynamic influence on viscosity. We have observed induction times and viscosity changes associated with the model that shows a trend in reaction kinetics in the following order from most to least reactive: UDMA [ CD582 [ HDDMA [ HEMA. With increasing amounts of reactive diluent included in the formulation, the kinetics of reaction was more sluggish. The value of this sigmoidal model is that it could help define formulation and process conditions most likely to control crosslinking to maximize dimensional stability or other thermophysical properties.

Tailored setting times with high compressive strengths in bassanite calcium sulfoaluminate eco-cements

“…Many authors have used a Boltzmann sigmoidal model to describe viscous fluids undergoing a setting reaction including starch, photopolymerizable acrylates and gels [46,47,48]. In our case, the Boltzmann sigmoidal model represents successfully the dynamics of the hydration of the three pastes with R 2 correlation factors higher than 0.999.…”

MMA bulk polymerization and its influence on in situ resin viscosity comparing several chemorheological models

“…The other kinetic parameter, Dt, correlates to the inverse of the slope of the viscosity rise. 26 Increasing temperature results in a faster response in dynamic viscosity due to cure conversion and can be observed by the changes mostly in the time constants of the model. Theoretically, the sigmoidal model would predict an initial induction period of nearly constant viscosity followed by a transient period the slope of which is related to the reaction dynamics as advancement occurs.…”

“…(4)] that captures not only the nonlinear trend in polymerization but also can be adjusted using form fitting parameters to include an initial viscosity and an end-point asymptotic viscosity limit [24][25][26] as shown in Eq. (4).…”

Stoichiometry Calculation in BaxSr1−xTiO3 Solid Solution Thin Films, Prepared by RF Cosputtering, Using X-Ray Diffraction Peak Positions and Boltzmann Sigmoidal Modelling

“…Diffraction peaks corresponding to (100), (111), (210), (211), (220), and (222) planes of the cubic BTO and STO phases were identified [21]. Diffraction peaks from (032) and (031) of the orthorhombic phase Ba 1.91 Sr 0.09 TiO 4 (marked with * ) [22], planes of (221) and (321), planes of the BTO tetragonal phase, and those of (211), (221), (310), (311), and (321) planes (marked with * * ) of the BST-SS tetragonal phase [8,18,23] were also identified. As STO sputtering power increases a shift of the BTO cubic phase reflections at higher diffraction angles is observed, indicating a lattice contraction due to the higher Sr composition in the films.…”

“…Figure 1 depicts a scheme of the Boltzmann sigmoidal equation, where before and after of the exponential growth there are two zones of stabilization distinguished by a central turning point, 1, 2, and ( 0, ( 1 + 2)/2), respectively. This function has also been used to describe other phenomena such as phase transition in smart gels [17], the relationship between reaction kinetics and its dynamic influence on viscosity in the chemorheology behavior of photopolymerizable acrylates [18], and the stem and rosebud growth in roses [19], among others.…”