Acrylate System Research Articles

Bubble-Point Measurement of Binary Mixture for the CO2 + Caprolactone Acrylate System in High Pressure

Bubble-Point Measurement of Binary Mixture for the CO2 + Caprolactone Acrylate System in High Pressure

Thiol–Ene Photopolymerization: Scaling Law and Analytical Formulas for Conversion Based on Kinetic Rate and Thiol–Ene Molar Ratio

Kinetics and analytical formulas for radical-mediated thiol–ene photopolymerization were developed in this paper. The conversion efficacy of thiol–ene systems was studied for various propagation to chain transfer kinetic rate-ratio (RK), and thiol–ene concentration molar-ratio (RC). Numerical data were analyzed using analytical formulas and compared with the experimental data. We demonstrated that our model for a thiol–acrylate system with homopolymerization effects, and for a thiol–norbornene system with viscosity effects, fit much better with the measured data than a previous model excluding these effects. The general features for the roles of RK and RC on the conversion efficacy of thiol (CT) and ene (CV) are: (i) for RK = 1, CV and CT have the same temporal profiles, but have a reversed dependence on RC; (ii) for RK >> 1, CT are almost independent of RC; (iii) for RK << 1, CV and CT have the same profiles and both are decreasing functions of the homopolymerization effects defined by kCV; (iv) viscosity does not affect the efficacy in the case of RK >> 1, but reduces the efficacy of CV for other values of RK. For a fixed light dose, higher light intensity has a higher transient efficacy but a lower steady-state conversion, resulting from a bimolecular termination. In contrast, in type II unimolecular termination, the conversion is mainly governed by the light dose rather than its intensity. For optically thick polymers, the light intensity increases with time due to photoinitiator depletion, and thus the assumption of constant photoinitiator concentration (as in most previous models) suffers an error of 5% to 20% (underestimated) of the crosslink depth and the efficacy. Scaling law for the overall reaction order, defined by [A]m[B]n and governed by the types of ene and the rate ratio is discussed herein. The dual ratio (RK and RC) for various binary functional groups (thiol–vinyl, thiol–acrylate, and thiol–norbornene) may be tailored to minimize side effects for maximal monomer conversion or tunable degree of crosslinking.

Dynamic Imine Bond-Based Shape Memory Polymers with Permanent Shape Reconfigurability for 4D Printing.

Shape memory polymer (SMP)-based 4D printing combines the advantages of SMP and 3D printing to form active materials with delicate structure. Nowadays, studies of SMP-based 4D printing materials mainly focus on cross-linked (meth)acrylate of which the permanent shape cannot be changed for their covalent linkage, limiting the usage of 4D printing materials. In this paper, a novel (meth)acrylate monomer with an aldehyde group (2-(methacryloyloxy)ethyl 4-formylbenzoate, MEFB) and hyperbranched cross-linker (HPASi) are synthesized to build (meth)acrylate systems (IEMSis) with dynamic imine bonds for 4D printing. The flexible chain structure of HPASi significantly enhances the toughness of IEMSis, which is 33-97-fold higher than that of the one without HPASi (IEM). The addition of HPASi also endows IEMSis good shape memory properties, and the shape fixity and shape recovery ratios of them are 97.5-97.6 and 91.4-93.7%, respectively. At the same time, IEMSis can undergo a stress relaxation process by dynamic exchanges of imine bonds under relatively mild conditions without a catalyst to acquire an ability of permanent shape reconfiguration. The shape retention ratio of IEMSi3 is 84.3%. In addition, the 4D-printed structures displayed here indicate that these 4D printing systems have a myriad of potential applications including aerospace structures, soft robotic grippers, smart electron switches, and intelligent packaging, while the reconfigurability shown by IEMSi3 will expand the scope of application fields of 4D printing materials.

Structure–mechanical property relationships in acrylate networks

ABSTRACTThe objective of this work is to investigate the effect of the molecular mobility and resin formulation of UV‐curable acrylate systems on conversion and ultimate mechanical properties. Thin single‐layer films are produced from a series of nine mixtures of bisphenol A ethoxylate diacrylate, having different molecular weights (BisDAn = 2, BisDAn = 4, and a 50/50 mixture), with different amounts of tetraethylene glycol diacrylate (TEGDA) (0, 10, and 30 wt %). Fourier transform infrared analysis, tensile, and dynamic mechanical tests are carried out on UV post‐cured resins, and the results are correlated with the amount of TEGDA. A higher content of TEGDA gives rise to an increase in conversion and glass‐transition temperature. Tests on pure BisDAn = 2 and mixtures of BisDAn = 2 and BisDAn = 4 (BisDAn = 2 + 4) show that with increasing TEGDA content, the crosslink density increases. An increase in molecular weight of the acrylate monomer changes the final mechanical properties of UV‐cured products. A material having a rubber behavior is the result of this change. Next to UV post‐curing, the effect of thermal post‐curing is studied. The results show that thermal treatments affect the mechanical properties mainly if the polymer has a low crosslink density. Formulations highly loaded with TEGDA lead to polymers with high crosslink density, low network mobility, and consequently low mechanical properties if thermally treated. Correlations between, on the one hand, resin formulation and process conditions and, on the other hand, the final mechanical properties of UV‐cured systems are established allowing to optimize the structure–mechanical properties relationship in acrylate networks. © 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48498.

Synthesis of Mercapto-based MTQ Resin and Its Effect on Photocuring Properties of Acrylate System

Synthesis of Mercapto-based MTQ Resin and Its Effect on Photocuring Properties of Acrylate System

Modification of mechanical properties and resolution of printed stereolithographic objects through RAFT agent incorporation

Stereolithography (SL) is an additive manufacturing technique that uses light to cure liquid resins into thin layers and fabricate 3-dimensional objects layer by layer. SL is of high interest for small-volume manufacturing and rapid prototyping because of its ability to relatively quickly create objects with intricate 100 μm or smaller features. However, widespread adoption of SL faces a number of obstacles including unsuitable thermomechanical properties, anisotropic properties, and limited resolution and fidelity. In this work, we incorporate a reversible addition-fragmentation chain transfer (RAFT) agent into a glassy acrylate formulation to modify mechanical properties and improve resolution of objects printed using digital light processing (DLP) SL. Incorporating a small amount of a trithiocarbonate RAFT agent into the formulation leads to increased elongation and toughness accompanied by a small decrease in tensile modulus. To determine anisotropic properties of DLP SL, samples were printed in “horizontal” or “vertical” directions, where the long axis of the sample was printed in the x-axis or z-axis, respectively. RAFT samples printed in a vertical orientation exhibit a higher modulus than non-RAFT controls prior to post-cure in addition to a similar modulus with increased toughness upon UV post-cure due to the living/controlled nature of RAFT polymerization. Furthermore, incorporating a RAFT agent into the formulation allows significantly higher fidelity printing of a broad range of positive and negative features as small as 100 μm. The RAFT formulation allows objects to be printed with significantly better fidelity than non-RAFT formulations, even when a radical scavenger is incorporated to mimic reaction rates observed from the RAFT formulation. Additionally, the RAFT agent significantly increases the critical energy parameter determined from the SL working curve, indicating an increase in gel point conversion. This work demonstrates the benefits of using controlled/living polymerization in a highly cross-linked acrylate system to improve toughness, modify anisotropic properties, and print high-fidelity features with enhanced properties in 3D printed materials.

Air-Curable, High-Resolution Patternable Oxetane-Based Liquid Crystalline Photonic Films via Flexographic Printing.

The production of patterned photonic films on a large scale remains a challenge. Here, we report on a new class of photonic materials that are based on oxetane liquid crystals (LCs). Patterned reflective coatings can be produced from these materials on flexible substrates by using flexographic printing. This industrially relevant process allows for upscaling in future applications. Furthermore, the oxetane LCs used do not require an inert atmosphere for photopolymerization, unlike previously described acrylate systems. We show that the flexographic printing process results in excellent alignment, and that the patterns produced display a high resolution. Additionally, we demonstrate that free-standing photonic reflecting foils can also be produced from these materials. Our new oxetane-based patterned iridescent colored materials have potential application for both esthetic purposes as well as anticounterfeit labels.

Characterization of Coating Properties of UV-curable Fluorine-Containing Coatings

In this study, fluorine chains were bonded with covalently in epoxy acrylate system via UV light. For this purpose, five different coating samples prepared. Bisphenol-A glycerolate diacrylate (epoxy acrylate) and 1,6-Hexanediol diacrylate were used as the main coating solution. The weight ratio of Bisphenol-A glycerolate diacrylate and HDDA was determined as 7/3. As a long fluorine chain, 1H,1H,2H,2Hperfluorodecyl acrylate (PFOA) was added into the main coating solution in the ratios of 0.25 wt %, 0.50 wt %, 0.75 wt % and 1 wt %. All prepared solutions were coated on aluminum plates by 75 µm by wire wound applicator and then cured via UV dryer. Physical properties of coatings were measured by tests such as MEK rubbing test for solvent resistance, gloss 60o test for brightness, cross-cut test for adhesion property and pencil hardness test for scratch resistance. Hydrophobicity was measured as static water contact angle test. The total surface energy was calculated by contact angle measurement software. In terms of mechanical properties, sheen impact test (for coating samples) and Shore - D hardness tests (for free film samples) were carried out. By examining the results of all these tests; cross-cut adhesion and gloss 60o values decrease with the fluorine content. On the other hand, by the increasing within the content of the fluorine chains, Taber abrasion resistance and hydrophobicity increase significantly but sheen impact resistance and Shore - D hardness values decrease slightly. In terms of cost and overall results, the most proper and multifunctional coating seemed at 0.25 wt %.

Thin film mechanical characterization of UV-curing acrylate systems

This study presents the mechanical characterization of UV-curing acrylate systems. UV-curable polymers are commonly used in the stereolithography (SLA) technique to build multi-layered objects. Typically, the mechanical properties of the 3D-printed product are affected by the intrinsic material heterogeneity along the sample thickness. To understand what determines this heterogeneity, single layers of UV-curable polymer are characterized and the effect of process conditions on the mechanical properties is studied. Micro-compression experiments are carried out to determine the intrinsic mechanical properties which are representative of one single UV-cured layer. To determine the right conditions to generate maximally-cured micropillars, the evolution with irradiation time of monomer conversion, glass-transition temperature and yield stress has first been studied. Thereto, micrometer-sized pillars and dog-bone shaped samples have been prepared via UV-curing. Micro-compression measurements on maximally-cured micropillars are performed to study possible size effects. The results reveal that with decreasing pillar size, the yield stress decreases. Tensile measurements are performed on dog-bone shaped samples which have been processed in the same way as compared to the compression samples. These tensile tests show higher yield stress values when compared with compression tests. This size effect can be attributed to the rinsing with acetone during the sample preparation that leads to a removal of monomer from the crosslinked network. As a consequence, in the real 3D-printing process, the mechanical properties will depend on the feature size. In conclusion, a method is presented to determine the mechanical properties of one single layer of material used in the rapid-prototyping SLA process. The experimental procedure we adopted requires only a few millilitres of material and, therefore, is well suited for screening materials under real SLA process conditions.

State of the Art in Dual-Curing Acrylate Systems.

Acrylate chemistry has found widespread use in dual-curing systems over the years. Acrylates are cheap, easily handled and versatile monomers that can undergo facile chain-wise or step-wise polymerization reactions that are mostly of the “click” nature. Their dual-curing processes yield two distinct and temporally stable sets of material properties at each curing stage, thereby allowing process flexibility. The review begins with an introduction to acrylate-based click chemistries behind dual-curing systems and relevant reaction mechanisms. It then provides an overview of reaction combinations that can be encountered in these systems. It finishes with a survey of recent and breakthrough research in acrylate dual-curing materials for shape memory polymers, optical materials, photolithography, protective coatings, structured surface topologies, and holographic materials.

Investigation of cure advancement in dual-cure polyurethane-acrylate coatings over metal substrates

In the present study, a polyurethane acrylate (PUA) system cured via a thermal–UV (dual-cure process) was developed. The system selected for this work was a two-pack polyurethane acrylate with polyester polyol as the main component and urethane monoacrylate (UMA) as hardener. The polyester polyol was synthesized in a way to provide a final film coating containing both a suitable flexibility and high surface hardness. The thermal and photochemical curing behavior of the resin was studied via the chemorheology technique and the real-time FTIR. The Boltzmann sigmoidal model was implemented and well-fitted to the data obtained from the chemorheology measurements. The comparison between two reactive diluents, butanediol diacrylate (BDDA) and trimethylolpropane triacrylate (TMPTA) showed that BDDA reacts faster than TMPTA in the thermal curing condition. Nevertheless, the network buildup is stronger when TMPTA is used. The photopolymerization is also faster for the case of TMPTA. However, its final double bond conversion is restricted to a lower amount due to steric hindrance and higher viscosity of the system.

Preparation of polymer-dispersed liquid crystal doped with indium tin oxide nanoparticles

ABSTRACTTo study polymer-dispersed liquid crystal (PDLC) films doped with indium tin oxide (ITO) nanoparticles (NPs), samples were prepared by ultraviolet-initiated polymerisation based on the thiol–acrylate system. Owing to the interaction between PDLC system and ITO NPs, the content and the size of ITO NPs are the main determinants to the microstructure which plays an essential role on the electro-optical and anti-infrared properties of the PDLC films. In the polymer matrix, a novel microstructure consisting of a dense surface, micron-sized meshes and submicron meshes is found to benefit the better performances of the low driven voltage (20.7 V), the relatively high contrast ratio (8.3) and the lowest transmittance(500–2500 nm) on average at about 3.55% with maximum of merely 7.6%. Thus, it lays a solid foundation for the further investigations on the microstructure and the performance of the PDLC films. Meanwhile, it is proved that the PDLC film, improved performance through doping ITO NPs, is promising to be a superior choice in the field of energy-saving.

β-Pinene – acrylate copolymer as a potential biodegradable multifunctional additives for lube oil

ABSTRACTViscosity index improver (VII) and Pour point depressant (PPD) performances of the β-pinene based newly developed greener additives were tested in base oil in terms of viscosity index (VI) and pour point (PP), respectively. It is observed that, incorporation of β-pinene induces excellent biodegradability in the acrylate system. Among the two systems, β-pinene – dodecyl acrylate copolymers showed higher VI and pour point depression efficiency than the corresponding decyl acrylate copolymers. The study also indicated that VI and PP values of the additive doped base oils depend on the nature of mineral base oils as well as on the type and concentration of the additives. The synthesized copolymers of each of them with β-pinene (BP) were characterized by spectral, gel permeation chromatographic (GPC) and thermogravimetric analysis. For a comparison the respective homopolymers were also prepared under identical conditions and tested for VII and PPD properties in base oils by the standard ASTM methods. The biodegradability along with multifunctional additive performance showed potential for the copolymers for their industrial application as lube oil additives.

Specific Features of Radical Formation in the Trialkylborane–Oxygen System and the Gluing Mechanism of Acrylate Composites

Fundamental study of how radicals are generated, with involvement of trialkylboranes combined with oxygen and organoelement peroxides, was carried out. It was shown that the complex process of gluing of polymeric materials with low-energy surface predominantly occurs under the action of trialkylborane unblocked from the amine complex and oxygen dissolved in the gluing formulation and also under the action of growth radicals produced in the trialkylborane–peroxide–acrylate system in the closed-system mode at room temperature. The curing process of the gluing formulation occurs in the course of time both in the bulk and on the substrate surface.

Confined Crystallization within Cylindrical P3EHT Block Copolymer Microdomains

Confinement of crystallites within block copolymer microdomains is a promising approach to study conjugated polymer crystallization due to interfacial chain tethering and defined geometries. The nanoscale organization of crystallites is often critical to determining the charge transport properties of conjugated polymers. Here, a poly(3-(2′-ethyl)hexylthiophene)-block-poly(methyl acrylate) (P3EHT-b-PMA) system is leveraged to study the impact of confinement within cylindrical microdomains. The crystalline P3EHT permits accessible melting temperatures and robust formation of traditional microphase-separated morphologies, while the rubbery PMA allows the local deformations required to permit P3EHT crystallization. Crystallites form with chains perpendicular to the diblock interface, causing domain expansion; TEM reveals that this is accommodated in the cylindrical geometry via local deformation. Complementary SAXS/WAXS of aligned diblocks shows preferential orientation of the alkyl chain stacks down domains....

Performance Evaluation of Pervaporation Technology for Process Intensification of Butyl Acrylate Synthesis

Pervaporation-based hybrid processes have been investigated to overcome the drawbacks of equilibrium-limited reactions. Pervaporation processes are strongly recommended for heat-sensitive products and azeotropic mixtures as in the butyl acrylate system case, since pervaporation can operate at lower temperatures than distillation. In this work, experimental pervaporation data for multicomponent mixtures in the absence of reaction were measured for the compounds involved in the esterification reaction of acrylic acid with n-butanol at different temperatures: 323, 353, and 363 K. A commercial tubular microporous silica membrane from Pervatech was used which is highly selective to water, and its performance was evaluated by studying several parameters, like the selectivity, permeate fluxes, driving force of species, and separation factor. The effects of temperature and feed composition were assessed for binary, ternary, and quaternary mixtures. Increasing the temperature increases significantly the total perm...

Termination, Transfer, and Propagation Kinetics of Trimethylaminoethyl Acrylate Chloride Radical Polymerization in Aqueous Solution

The SP–PLP–EPR (single pulse–pulsed laser polymerization–electron paramagnetic resonance) method has been used to measure the rate coefficients of termination, intramolecular transfer, and propagation for the radical polymerization of 20 wt % trimethylaminoethyl acrylate chloride (TMAEA) in the temperature range 0–90 °C. The high complexity of this acrylate system is due to water being the solvent, to the monomer being a strong electrolyte, and to both secondary chain-end radicals and tertiary midchain radicals being simultaneously present. The termination kinetics, which was analyzed by a chain-length-dependent scheme, largely differs from the situation met with nonionized radicals. The reliability of the rate coefficients obtained from the SP–PLP–EPR experiments has been demonstrated by the almost perfect agreement of TMAEA conversion vs time data from simulation, on the basis of these coefficients, and from the chemically initiated TMAEA polymerization experiment at 70 °C.

Surface-Triggered Tandem Coupling Reactions of Cyclic Azasilanes.

Cyclic azasilanes have been synthesized for the purpose of developing coupling agents appropriate for a variety of nanotechnologies including surface modification of nanoparticles, nanocrystals, mesoporous materials and substrates. N‐Methyl‐aza‐2,2,4‐trimethylsilacyclopentane is representative of this class of compounds. Preliminary data for the treatment of inorganic surfaces, including nanoparticles and oxidized silicon wafers, with cyclic azasilanes suggest high‐density monolayer deposition by a ring‐opening reaction. Cyclic azasilanes contain a cryptic amine functionality that can perform a subsequent tandem coupling reaction with functional molecules after the surface‐triggered ring‐opening reaction, allowing for a one‐pot self‐assembly route on nanostructures. Tandem coupling reactions are demonstrated via addition reactions of the cryptic amine with epoxy and acrylate systems.

Tailoring Copolymer Properties by Gradual Changes in the Distribution of the Chains Composition Using Semicontinuous Emulsion Polymerization.

To design the properties of a copolymer using free radical polymerization, a semicontinuous process can be applied to vary the instantaneous copolymer composition along the conversion searching for a specific composition spectrum of copolymer chains, which can be termed as weight composition distribution (WCD) of copolymer chains. Here, the styrene-n-butyl acrylate (S/BA) system was polymerized by means of a semicontinuous emulsion process, varying the composition of the comonomer feed to obtain forced composition copolymers (FCCs). Five different feeding profiles were used, searching for a scheme to obtain chains rich in S (looking for considerable modulus), and chains rich in BA (looking for large deformation) as a technique to achieve synergy in copolymer properties; the mechanostatic and dynamic characterization discloses the correspondence between WCD and the bulk properties. 1H-nuclear magnetic resonance (1H-NMR) analysis enabled the determination of the cumulative copolymer composition characterization, required to estimate the WCD. The static test (stress-strain) and dynamic mechanical analysis (DMA) were performed following normed procedures. This is the first report that shows very diverse mechanostatic performances of copolymers obtained using the same chemical system and global comonomer composition, forming a comprehensive failure envelope, even though the tests were carried out at the same temperature and cross head speed. The principles for synergic performance can be applied to controlled radical copolymerization, designing the composition variation in individual molecules along the conversion.

Microscopic progression in the free radical addition reaction: modeling, geometry, energy, and kinetics.

The free radical addition reaction is very important in UV curing. The benzoyl radical is the most commonly observed radical. In the addition process, the benzoyl radical adds to an acrylate monomer, forming a primary radical that has great value for subsequent research. In this article, a quantum chemical method was used to study the microscopic progression from the reactive complex to the saddle point. The reactions of three monomers (amylene, allyl methyl ether and methyl acrylate) with a benzoyl radical were evaluated in terms of geometry and energy. The results were also interpreted with an expanded version of the Polanyi rules and the interaction/deformation theory. The deformation energy of methyl acrylate was found to be the smallest, and the bond formation index showed that the transition state in the methyl acrylate system forms early, and can easily reach the saddle point. The activity of the monomer was ascertained by charge analysis and was further confirmed by the reaction rate. Mayer bond order curves depicted the constantly changing chemical bonds during formation and dissociation. Reduced density gradient analysis showed a weak interaction between the monomer and the benzoyl radical.