Evolution of material properties during free radical photopolymerization

Wu, Jiangtao; Zhao, Zeang; Hamel, Craig M.; Mu, Xiaoming; Xiao, Kun; Guo, Zhongning; Hu, Qi

doi:10.1016/j.jmps.2017.11.018

Cited by 141 publications

(139 citation statements)

References 71 publications

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“…A very recent work by [66] on the reaction-diffusion coupling in photoresponsive gels is also noteworthy. Recent works on coupled photochemical reaction-large deformation theory has also been published by several research groups [28,58,65].…”

mentioning

confidence: 99%

A thermodynamically consistent chemo-mechanically coupled large deformation model for polymer oxidation

Konica

Sain

2020

Journal of the Mechanics and Physics of Solids

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In this paper, we present a continuum-level thermodynamically consistent model for high temperature oxidation in polymers, that incorporates the coupling between diffusion, chemical reaction and large deformation behavior of polymers. The specific constitutive forms are derived based on the thermodynamic inequality conditions and the kinetics of the oxidative reactions are considered. Oxidative shrinkage has also been considered in the kinematics as an irreversible effect. Subsequently, the model is implemented in ABAQUS/Standard to analyze numerically the coupled diffusion-reaction behavior of polymers undergoing oxidation. Several numerical simulations are performed to understand the effect of various material parameters on the oxidative response. The model is capable of predicting the heterogeneous oxidation profile within a thick polymer sample. It can also track the growth of oxide layer in the case of a long-term thermo-oxidative aging process. The model can be used to simulate the oxidation process involving complex geometries (as fiber reinforced composites) fairly easily under various ambient conditions.

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mentioning

confidence: 99%

A thermodynamically consistent chemo-mechanically coupled large deformation model for polymer oxidation

Konica

Sain

2020

Journal of the Mechanics and Physics of Solids

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“…When the prepolymer starts to receive the transmitted light from the DMD, the photoinitiator absorbs the light at a specific wavelength till it reaches its molar excitation threshold, then an intermolecular photocleavage occurs, and the photoinitiator decomposes to its active radicals. These radicals attack the double bonds of the surrounding monomers and oligomers, starting a chain reaction and bonding of the active monomers and oligomers with the other unsaturated ones and form polymer chains [21]. Due to this, a state of coexistence of gel and liquid appears.…”

Section: Photopolymerizationmentioning

confidence: 99%

“…where β j is the photodecomposition coefficient of molecule j, which in this case can be either the photoinitiator or the photoblocker, and I is the irradiance. As the absorbed energy increases, the concentrations of both the photoinitiator and blocker decrease, which will increase the amount of the penetrating and non-absorbed energy [21,22]. As the degree of monomer conversion (DOC) increases, the number of prepolymer molecules decreases and the number of polymer molecules increases; usually polymer absorption, α P, is much higher than the prepolymer molecules absorption (α o ).…”

Section: Photopolymerizationmentioning

confidence: 99%

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Concurrent Modelling and Experimental Investigation of Material Properties and Geometries Produced by Projection Microstereolithography

et al. 2020

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Projection microstereolithography additive manufacturing (PµSLA-AM) systems utilize free radical photopolymerization to selectively transform liquid resins into accurate and complex, shaped, solid parts upon UV light exposure. The material properties are coupled with geometrical accuracy, implying that optimizing one response will affect the other. Material properties can be enhanced by the post-curing process, while geometry is controlled during manufacturing. This paper uses designed experiments and analytical curing models concurrently to investigate the effects of process parameters on the green material properties (after manufacturing and before applying post curing), and the geometrical accuracy of the manufactured parts. It also presents a novel accumulated energy model that considers the light absorbance of the liquid resin and solid polymer. An essential definition, named the irradiance affected zone (IAZ), is introduced to estimate the accumulated energy for each layer and to assess the feasibility of the geometries. Innovative methodologies are used to minimize the effect of irradiance irregularities on the responses and to characterize the light absorbance of liquid and cured resin. Analogous to the working curve, an empirical model is proposed to define the critical energies required to start developing the different material properties. The results of this study can be used to develop an appropriate curing scheme, to approximate an initial solution and to define constraints for projection microstereolithography geometry optimization algorithms.

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“…This study is a purely theoretical/numerical one and does not include an experimental investigation of the crosslinking reaction of photopolymers used in additive manufacturing. Wu et al investigate the evolution of mechanical properties during photopolymerisation and build up a model for the finite element analysis of residual stresses and bending strains, see [20]. The experimental investigation of different postcuring processes and their influence on the thermal and mechanical properties of a commercially available photopolymer is the main part of [21].…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation and modelling of the curing behaviour of photopolymers

et al. 2020

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This paper focuses on the experimental investigation and modelling of the crosslinking reaction of photopolymers used in additive manufacturing processes such as digital light processing and stereolithography. Starting with general mathematical concepts for the description of the material behaviour of polymeric materials, the importance of modelling the crosslinking reaction is emphasized. In order to characterise the crosslinking reaction experimentally, photocalorimetric measurements with varying isothermal temperature and light intensity are shown. From the exothermic heat flows measured during the crosslinking reaction, the degree of cure can be determined for each experimental scenario as a function of time. It is shown that the test temperature and light intensity have a significant influence on the crosslinking reaction. A modelling approach for the description of the crosslinking reaction incorporating temperature and light intensity is presented. Moreover, parameter identification and a comparison of the proposed model with the experiments are conducted. The indentified model has an excellent match with experimental data, resulting in a least square error smaller than 3 %. The proposed model and identification method opens up several extensions for the modelling of the material behaviour.

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Evolution of material properties during free radical photopolymerization

Cited by 141 publications

References 71 publications

A thermodynamically consistent chemo-mechanically coupled large deformation model for polymer oxidation

A thermodynamically consistent chemo-mechanically coupled large deformation model for polymer oxidation

Concurrent Modelling and Experimental Investigation of Material Properties and Geometries Produced by Projection Microstereolithography

Experimental investigation and modelling of the curing behaviour of photopolymers

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