Cross-linking Reaction Of Polymer Research Articles

Effect of polymer crosslinking to the failure behavior of thermoplastic composite remelting interface: Molecular dynamics simulation and experimental verification

AbstractThe forming interface is the weak link of thermoplastic composite complex structures. To explore the effect of polymer crosslinking on the failure behavior of thermoplastic composite remelting interface using “Preforming + Remelting bonding” process, the all‐atom models of different types of interfaces were established, and a molecular dynamics (MD) simulation was conducted on the uniaxial tensile failure process of the remelting interface. The failure behavior of the remelting interface with different preforming processes was tested to verify the correctness of MD simulation, and the influencing mechanism of polymer crosslinking reactions in the preforming stage to the remelting interface properties was clarified. The results showed that the yield stress of the uncrosslinked interface reaches 283.2 MPa and 16.0% and 50.6% higher than that of the unilateral and bilateral crosslinked interfaces respectively. The polymer crosslinking reaction during the preforming stage will reduce the interlaminar bonding performance. The interlaminar shear strength (ILSS) of the uncrosslinked interface is 87.46 MPa and 7.21% and 27.36% higher than that of the unilateral and bilateral crosslinked interface respectively, and only 3.95% lower than that of the non‐remelting sample formed by standard process. This research provides a new approach for predicting and analyzing the effect of polymer crosslinking on remelting interface properties of thermoplastic composite using “Preforming + Remelting bonding” process.Highlights The failure behavior of different thermoplastic composite remelting interfaces was studied. MD simulation was conducted on the uniaxial tensile failure process of the remelting interface. The influencing mechanism of polymer crosslinking reactions in the preforming stage to the remelting interface properties was clarified. It is effective to explore the failure mechanism of thermoplastic remelting interface by MD simulation.

Improved thin film stability of differently formulated, printed, and crosslinked polymer layers against successive solvent printing

ABSTRACTInterface control remains a top challenge of solution‐processed organic light emitting diodes (OLED) stacks since the device performance heavily relies on it. Film stability of an inkjet deposited and crosslinked layer against subsequent exposure to a suitable inkjet printed solvent has been investigated. Impact of processing solvent (solvent used to prepare the polymer layer) on solution‐cast thin film properties has already been shown for polymer films. To our knowledge, this study is the first one analyzing thin films stability against solvent exposure using technology relevant materials processed via inkjet printing (IJP). The outcome of this research showed that the stability of the crosslinked films is affected by the solvent used for ink formulation. These findings are of great interest for multilayered semiconductors devices, such as OLEDs, field‐effect transistors and dye‐sensitized solar cells. Differential scanning calorimetry (DSC) was used to quantify the efficiency of the polymer crosslinking reaction in pure powder and in thin films, as processed from different solvents. Crosslinking efficiency measured by DSC correlated well with the deformation induced by the solvent and observed on layer surfaces. The interaction in solution between polymer and solvent has also been evaluated to explain its impact on thin film stability against successive solvent printing. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48895.

Research on deep profile control technology of polymer gel with low hydrolytic degree

Polymer gels have attracted increasing interest as profile control agent to control water content and enhance oil recovery in heterogeneous reservoirs. However, retarding the gel crosslinking reaction of polymer and making it farther in the reservoir has become a difficulty in deep profile control. In this article, polyacrylamide with low degree of hydrolysis was prepared to react slowly with chromium ion to form gel, which was used for adjusting water injection profile. The microstructure of polymer gel was characterized using Fourier transform infrared spectroscopy and scanning electron microscopy. Core displacement experiments were used to evaluate the profile adjustment capability of polymer gels. It was found that the gel prepared by crosslinking the 5% polyacrylamide with chromium acetate can retard gelation time to 30 days in comparison with the conventional polymer gels when the polymer concentration reached to 1500 mg/L. The gel can form a regular spatial network which increases the viscosity from 80.2 to 6578 mPa · s. The results obtained by the core flooding experiment prove that the polymer gel has good profile control ability and further demonstrate the future potential of polymer gel to enhance oil recovery.

Characterisation of C-shape pultruded fibre reinforced polymer for bridge structures

The development of polymer technology has been increased for the past 20 years. Most of the polymer based product is available for aviation, automotive, industrial, and infrastructure purposes include bridges. But, information concern with the used of polymer materials for bridge structures are scattered. In this paper, characterisation was made to investigate the applicability of pultruded fibre reinforced polymer (PFRP) for bridges as structural elements. Several experiments test was then carried out to determine the physical and mechanical properties of PFRP. Some results are compared with the available pre-standard of PFRP for structures. Afterwards, an ageing test was undertaken to observe the effect of temperature on the mechanical properties of PFRP. Comparison with the pre-standard of PFRP for structures show that the physical characteristics are satisfied the minimum requirements. In the mechanical part, the tensile and flexural properties of tested PFRP are conform with the pre-standard of PFRP, whereas the compressive strength was below the recommendation of the pre-standard. From ageing test under high temperature, the PFRP strength is possible to increase or decrease. Enhancement of mechanical strength could be generated by polymer cross-linking reactions which takes place after the production of PFRP and accelerated by high temperature. While, the decreasing of strength is related to the delamination process of the fibre.

Non-enzymatic amperometric sensor for hydrogen peroxide detection based on a ferrocene-containing cross-linked redox-active polymer

Herein, we report a novel redox-active polymer-based amperometric hydrogen peroxide sensor constructed by physical entrapment of ferrocene carboxylic acid (FcA) into a cross-linked amino-polyethersulfone film (denoted as FcAPS) in a single-step process. The strategy of design was simple yet original allowing the simultaneous achievement of two tasks: i) easy FcA immobilization and ii) in situ polymer crosslinking reaction directly at a glassy carbon electrode surface (GCE). The FcAPS/GCE system shows a good redox behavior, pertaining to the ferrocene/ferrocenium redox couple. The APS-based immobilization was highly effective avoiding the entrapped FcA leaching and thus stabilizing its electrochemical response. The sensing platform, best operated at an optimal voltage of +0.6 V (vs. SCE), was found to exhibit good electrocatalytic activity towards H2O2 oxidation with a detection limit of 2.07 μM (at S/N = 3) and a wide linear range of 10 μM to 10 mM. The enzyme-free sensor, endowed with satisfactory performances, was successfully used to detect H2O2 in processed cow’s milk samples with very good recoveries.

Solution Processed Alternating Organic/Inorganic Multilayer for OLED Encapsulation

Organic light-emitting diodes (OLEDs) are promised to replace the existing displays and lightings in terms of the quality of light. One of the most exciting features of organic electronics is that they can be made flexible. However, flexible OLED encapsulation is actually one of the major challenges because they are very sensitive to oxygen and moisture. Thin-film encapsulation (TFE) prepared by vacuum-deposition processes (ALD, CVD) have high barrier properties, but low throughput and high cost. For the significant cost reduction, all solution-processed roll to roll (R2R) production of OLEDs need to be established. Among the technologies needed, that for the thin-film encapsulation (TFE) imposes the highest challenge, because thin films with a very high level of barrier performance needs to be fabricated onto a complete organic device, so that solvents to attack the materials and high temperature treatments need to be strictly avoided. In this work, organic/inorganic multilayer encapsulation structures based on one step solution-processed alternating polysiloxane and silica layer are presented in Fig. 1(A), in which organic layers are spin-coated, followed by polymer crosslinking reaction, and finally subjected to photochemical conversion of the surface into dense silica barrier layers under exposure to vacuum ultraviolet（VUV) light. The whole process is very simple and fast to perform at room temperature, and the coating solution is successfully developed not to destroy the pre-formed organic emitting layer. Transmission electron microscopic (TEM) image shows successful fabrication of multi-stacks of organic/SiOx hybrid alternating layers (Fig. 1(B)). The thickness of ~ 100 nm was achieved per coating. The performance of such multilayer as thin-film encapsulation (TFE) of an OLED device has also been investigated as shown in Fig. 1 (C). The preliminary life time to reach 90% of the initial luminance (5000 cd/m2) was 73 hours for the OLED encapsulated with 450 nm TFE, about 6 times extended compared to that of the bare device. Figure 1

Single cell-laden protease-sensitive microniches for long-term culture in 3D.

Single cell-laden three-dimensional (3D) microgels that can serve to mimic stem cell niches in vitro, and are therefore termed microniches, can be efficiently fabricated by droplet-based microfluidics. In this technique an aqueous polymer solution along with a highly diluted cell solution is injected into a microfluidic device to create monodisperse pre-microgel droplets that are then solidified by a polymer crosslinking reaction to obtain monodisperse single cell-laden microniches. However, problems limiting this approach studying the fate of single cells include Poisson encapsulation statistics that result in mostly empty microniches, and cells egressing from the microniches during subsequent cell culture. Here, we present a strategy to bypass Poisson encapsulation statistics in synthetic microniches by selective crosslinking of only cell-laden pre-microgel droplets. Furthermore, we show that we can position cells in the center of the microniches, and that even in protease-sensitive microniches this greatly reduces cell egress. Collectively, we present the development of a versatile protocol that allows for unprecedented efficiency in creation of synthetic protease-sensitive microniches for probing single stem cell fate in 3D.

Nitrile Oxide-Norbornene Cycloaddition as a Bioorthogonal Crosslinking Reaction for the Preparation of Hydrogels.

This communication describes the first application of cycloaddition between an in situ generated nitrile oxide with norbornene leading to a polymer crosslinking reaction for the preparation of poly(ethylene glycol) hydrogels under physiological conditions. Hydrogels with high water content and robust physical strength are readily formed within 2-5 min by a simple two-solution mixing method which allows 3D encapsulation of neuronal cells. This bioorthogonal crosslinking reaction provides a simple yet highly effective method for preparation of hydrogels to be used in bioengineering.

Comparison of Isothermal with Nonisothermal Kinetics for Ethylene-Vinyl Acetate Cross-Linking Reaction in the Solid State

Cross-linking reaction kinetics of ethylene-vinyl acetate (EVA) copolymer initiated with dicumyl peroxide is studied by differential scanning calorimetry (DSC) and a cross-linking rheometer. As the degree of cross-linking (α) is less than 0.30, EVA can flow relatively freely because of insufficient cross-linking. As α ranges from 0.31 to 1, there is more of the cross-linking reaction, and the polymer becomes fully cross-linked in the later stage of the reaction so that three-dimensional cross-linked nets have been constructed. New kinetics approaches are proposed on the basis of the cross-linking parameters measured with the cross-linking rheometer incorporated into Hill and Avrami mathematical equations. As the cross-linking rheometer is popular in manufacturing the cross-linked EVA, the approaches are simpler and more convenient than the DSC method for fast studying kinetics of the cross-linking reaction of polymer in solid or melting state. The total cross-linking reaction rate changes with α, and the apparent activation energy is 91.2–175.0 kJ/mol.

Photocrosslinking of styrene–isoprene–styrene; effect of benzoin and ethylene glycol dimethacrylate on physical properties

Crosslinking reaction of polymer by ultraviolet (UV) irradiation has been important in industries. In this work, photocrosslinking of styrene–isoprene–styrene (SIS) triblock copolymer in the presence of benzoin photoinitiator and a dimethacrylate monomer as crosslinking agent was investigated. Curing of samples was initiated under UV irradiation. Benzoin was used as photoinitiator because it contains chromophore group that could absorb UV irradiation. Ethylene glycol dimethacrylate (EGDMA) was used as crosslinking agent, since it has alkene functional groups that could react with the alkene group of SIS. ATR-FTIR spectra of samples show that absorption band of double bond at 1500–1600 cm−1 decreases after UV exposure. Increasing the concentration of benzoin (0.1–1 phr) and EGDMA (1–10 phr) leads to an increase in gel content and hardness, while swelling ratio decreases. After 5 min heating at 150 °C, about 20%wt of the unirradiated compound became insoluble, because heating of compound at 150 °C causes crosslinking reaction without any irradiation.

Precipitated Calcium Carbonate as Reagent Carriers for Crosslinking Reactions

Precipitated calcium carbonates (PCC) of different particle morphologies were used as appropriate carrier particles for post-processing crosslinking reactions. Optimum particle morphology and size were estimated for preparation of dry liquids (DLs). The DLs were tested in three typical crosslinking reactions of polymers.

Cross-linking Reaction of Polymer by Atmospheric Pressure Plasma Jet

Cross-linking Reaction of Polymer by Atmospheric Pressure Plasma Jet

Warpage evolution of overmolded ball grid array package during post-mold curing thermal process

Two of the main driving forces for warpage deformation and residual stress in electronic packages are the thermal expansion mismatch between dissimilar package constituents and the crosslinking reaction of polymers during packaging thermal processes. For the purpose of quantitatively characterizing these two driving forces and assessing the process effect on warpage deformation, experimental and numerical analyses were applied to study the warpage evolution of overmolded ball grid array (BGA) package under post-mold curing (PMC) thermal histories. From in situ shadow Moiré warpage analyses on bimaterial and package specimens, it was observed that, during the isothermal curing condition, a significant increase in specimen warpage occurred as a result of molding compound shrinkage. A numerical modeling procedure that incorporates the models for the thermochemical cure kinetics, the curing- and chemical aging-induced shrinkage strains, and the cure-dependent viscoelastic relaxation modulus for the molding compound was then applied to simulate and compare to the experimentally obtained warpage evolutions. It can be seen from the analysis results that the evolution of package warpage over multiple thermal histories can be superpositioned by the thermal expansion mismatch-driven warpage change during non-isothermal stages and the chemical shrinkage-induced warpage evolution during isothermal aging at temperatures above the material glass transition point.

Effects of solvent basicity on free radical polymerizations of N,N′‐bismaleimide‐4,4′‐diphenylmethane initiated by barbituric acid

AbstractThe polymerizations of N,N′‐bismaleimide‐4,4′‐diphenylmethane (BMI) initiated by barbituric acid (BTA) carried out in a variety of solvents at 130°C were studied. The nitrogen‐containing cyclic solvents such as N‐methyl‐2‐pyrrolidinone acted as a catalyst to promote the formation of the three‐dimensional crosslinked network structure. By contrast, the polymerization in a cyclic solvent that did not contain nitrogen such as γ‐butyrolactone resulted in nil gel content. The higher the solvent basicity, the larger the amount of insoluble polymer species formed. The molar ratio of BTA to BMI also played an important role in the polymerizations. The resultant polymers, presumably having a hyper‐branched structure, exhibited much narrower molecular weight distributions than those prepared by conventional free radical polymerizations. The BMI polymerizations using BTA as the initiator could not be adequately described by conventional free radical polymerization mechanisms. A polymerization mechanism that took into account the generation of a ketone radical pair between BTA and BMI and the subsequent initiation, propagation and termination reactions was proposed. It was concluded that the nitrogen‐containing cyclic solvents were capable of participating in the ketone radical pair formation process, thereby increasing the extent of polymer crosslinking reactions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Polysaccharide Film-Coating Process for Freely Swellable Hydrogels

ABSTRACTIn order to control the drug release from coated hydrogels by preventing membrane fractures, an intramembrane freely swellable matrix device was designed by enclosing a void space between a crosslinkedpoly(vinyl alcohol) (PVA) matrix and a calcium alginate membrane. The highly swellable PVA matrix loaded with diltiazem hydrochloride was obtained by means of a simplified procedure of the polymer crosslinking reaction using glutaraldehyde in solution with ammonium persulfate. The undried swollen matrix was coated with a calcium alginate membrane employing an ionotropic gelation of sodium alginate induced by calcium ions. The subsequent drying process generated a void space separating the inner core from the membrane. The resulting calcium alginate membrane, which was uniform and compact in the structure, increased in thickness according to the coating time. Coating times exceeding 5 min allowed modification of the drug release profile providing, after a short burst period, sustained and constant rate phases in both simulated gastric fluid and simulated intestinal fluid. Because the inner hydrogel expanded freely inside the device, the unstressed and intact membrane could act as the rate-controlling factor in the drug release process. Owing to the pH-dependent behavior of the membrane, most of the drug was delivered in intestinal fluid. Therefore, the device proposed could be advantageously used for drug targeting to the small intestine.

Synthesis and thermal crosslinking reaction of polymers containing pendant carboxyl and epoxy groups

Synthesis and thermal crosslinking reaction of polymers containing pendant carboxyl and epoxy groups

Synthesis and thermal crosslinking reaction of polymers containing pendant carboxyl and epoxy groups

Synthesis and thermal crosslinking reaction of polymers containing pendant carboxyl and epoxy groups

Synthesis and thermal crosslinking reaction of polymers containing pendant carboxyl and epoxy groups

Polymers containing both pendant carboxyl and epoxy groups were synthesized by the radical copolymerization of p-vinylbenzyl glycidyl ether (VBGE) and itaconic acid monomethyl ester (IAME). The copolymerization proceeded smoothly under various conditions, and polymer soluble in 1,4-dioxane with no gel fraction was obtained. However, the carboxyl-epoxy addition reaction between VBGE and IAME was observed, when DMSO or DMF were used as polymerization solvents. The IR and 1H-NMR spectrum of copolymers of VBGE and IAME showed the corresponding structure. The thermal crosslinking reaction of the resulting copolymers was examined under various conditions. Tetrabutylammonium bromide (TBAB) showed catalytic activity for the reaction. However, a 100% gel fraction of polymer was achieved after only 15 min without any catalyst, when the crosslinking reaction was performed at 150°C. © 1996 John Wiley & Sons, Inc.

Hydrolyzed Polyacrylamide/Chromium(III) Acetate Gel Chemistry

Proton NMR and visible spectroscopy are used to investigate the chemistry of hydrolyzed polyacrylamide/chromium acetate gels. Color changes in conjunction with HNMR are used to monitor chromium acetate hydrolysis, and HNMR is used to characterize Polyacrylamide in solution and to monitor increases of free acetate and decreases of polymer backbone proton and amide proton resonances during gel formation. The data indicate that chromium acetate hydrolysis is halted by polymer coordination. The polymer cross-linking reaction appears to be a simple replacement of chromium(III) coordinated acetate groups on the chromium(III) trimer by polymer carboxylate groups.

Syntheses and crosslinking reactions of polymers containing spiroorthoester moieties

AbstractThe radical copolymerization of unsaturated spiroorthoesters such as 2‐methylene‐1,4,6‐trioxaspiro[4.6]undecane (SOE I) and 2‐methylene‐9‐methyl‐1,4,6‐trioxaspiro[4,5]decane (SOE II) with vinyl monomers was carried out to find that SOE I and SOE II were copolymerized with electron‐poor olefins such as methyl acrylate, acrylonitrile, and methyl methacrylate to obtain the corresponding copolymers containing spiroorthoester moieties, respectively. The obtained copolymers were treated with BF3.OEt2 or BzS+SbF to afford crosslinked polymers undergoing expansion in volume on crosslinking in those cases of copolymers of SOE I.