Monomer Viscosity Research Articles

Vat photopolymerization 3D printing of biobased low viscosity photoactive benzoxazine thermosets

Preparing biobased benzoxazine resin through vat photopolymerization 3D printing is of great significance for its sustainable development and application in cutting-edge fields. In this work, biobased guaiacol and eugenol are used as phenol sources, while 2-(2-aminoethoxy) ethanol with flexible ether bonds is used as an amine source to create photoactive benzoxazine monomers, Eu-BzMA and Gu-BzMA. The viscosity of both monomers at room temperature is lower than 150 mPa·s, which can satisfy the requirements of digital light processing (DLP) 3D printing without adding diluents. The thermal and mechanical properties of the 3D printing benzoxazine resins are studied and the relationship between structure and properties is discussed by comparing the two molecules. Eu-BzMA resin has higher thermal decomposition temperature (T5 = 343 °C), higher hardness (0.70 GPa), higher flexural stress (43.5 MPa) and flexural moduli (2.71 GPa); while, Gu-BzMA resin has higher glass transition temperature (176 °C). This is because Eu-BzMA resin shows higher cross-linking density, but contains more flexible structures formed by allyl crosslinking. In this article, a preparation strategy of low viscosity biobased photoactive benzoxazine is proposed and successfully applied to vat photopolymerization 3D printing.

Synthesis, characterization, photo-polymerization, hydrolytic stability, and etching behavior of new self-etch adhesive monomers

Considering the poor hydrolytic stability of the most methacrylate-based functional monomers of self-etch dental adhesives in acidic and aqueous conditions, in this study allyl-based photo-polymerizable self-etch monomers was synthesized in order to improve the hydrolytic stability.The new self-etch monomers based on phosphonic acid functional groups were synthesized through a two-step procedure. First, phosphoric anhydride, poly-phosphoric acid, and polyethylene glycol were reacted to produce phosphate ester precursor (P-PEG-P). Next, allyl 2, 3-epoxypropyl ether was reacted with P-PEG-P to synthesize allyl self-etch monomer. Glycidyl methacrylate was also reacted with P-PEG-P to synthesize a methacrylate self-etch analogue monomer. The monomers were characterized using FTIR and 1H-NMR spectroscopy. The viscosities of monomers were measured using a rheometer. The degree photopolymerization conversion of monomers was measured using FTIR spectroscopy. The pH assay was performed by a digital pH-meter. The etching behavior of the monomers on human teeth was studied using scanning electron microscopy (SEM). Thermo-gravimetric analysis (TGA) was performed to evaluate the possible interaction of the monomers with tricalcium phosphate (TCP). The solubility of synthesized monomers was examined in ethanol, acetone, and water. The hydrolytic stability of cured resins in artificial saliva during 4 months was also surveyed.The synthesis of new self-etching monomers was successfully confirmed by spectroscopy analyses. The results represented appropriate viscosity of self-etching monomers around 1 (Pa s). The resin containing methacrylate monomer exhibited its degree of conversion is more than that of allyl monomer (p < 0.05). The allyl and methacrylate self-etch monomers exhibited pH values of 1.2 and 1.3, respectively. SEM micrograph verified that the synthesized monomers were able to suitable etching of the enamel human premolar teeth. The data obtained from TGA tests revealed that thermal stability of (TCP) containing monomers is enhanced. Also, the monomers exhibited an excellent solubility in polar solvents, but when they are mixed with TCP, they are not, anymore, dissolved in these solvents. Furthermore, the allyl monomer showed higher hydrolytic stability than the methacrylate monomer.The new photo-polymerizable acidic monomer based on allyl functionality showed enhanced hydrolytic stability compared to methacrylate-based monomer. It may be considered as a promising monomer for self-etch dental adhesives.

Advances on holographic polymer nanocomposites

<p indent="0mm">Holography is a revolutionary technique to reconstruct the whole information of light including amplitude and phase, which has displayed transformative impacts on a myriad of fields such as display, data storage, anti-counterfeiting and stereo-advertising. For these applications, holographic polymer materials have been widely applied due to the lightweight, easy-processing and cost-effective characteristics. However, due to the small box of material pool and limited protocols to tune the properties, it is difficult for traditional holographic polymer materials to meet the increasing requirements of emerging optical and electro-optical applications. Holographic polymer nanocomposites (HPNC), which are novel polymer nanocomposites with periodically ordered structures, show transformative potential compared with traditional holographic polymer materials. They can be fabricated through photopolymerization-induced phase separation upon laser interference patterns, during which the whole information of light is stored in the micron/submicron gratings. More excitingly, as conceptual information materials, HPNC can record added information using the incorporated functional components including nanoparticles, liquid crystals, and photoluminescent molecules. Thus, they show great application potential in high-tech fields such as advanced anti-counterfeiting, three-dimensional display to the naked eye, augmented reality and high-density data storage. Functions and performances of HPNC are not only determined by the phase separation structure, but also highly dependent on the spatial location of functional components. This minireview intends to summarize the methods for boosting the phase separation and performance of HPNC, and to introduce several useful protocols for endowing added functions to HPNC. (1) “Photoinitibitors”, which are conceptual and distinct from traditional photoinitiators or inhibitors, are of vital significance for boosting the phase separation and diffraction efficiency of HPNC gratings by the unique synergy of the concurrently generated photoinitiation and inhibition functions. This synergy cannot be realized by adding other inhibitors. Several “photoinitibitors” have been demonstrated, e.g., the blue light sensitive 3,3′-carbonylbis(7-diethylaminocoumarin) (KCD)/<italic>N</italic>-phenylglycine (NPG) and green light sensitive rose bengal (RB)/NPG systems. (2) A mathematical model is presented, which shows that the segregation degree during holographic photopolymerization-induced phase separation is proportional to the gelation time while reversibly proportional to the initial viscosity. This model suggests the employment of multifunctional monomers but with low viscosity. To this end, monomers with hyperbranched architectures are critical as the monomer viscosity usually increases with an augmentation of functionality. (3) Liquid crystals show remarkable impacts on the electro-optical performance of HPNC by dialing the dimensions of the liquid crystal droplets within HPNC. Generally, larger droplets will give rise to lower driving voltage and higher light scattering. However, the light scattering must be depressed for practical applications. Boosting the phase separation while decreasing the droplet size would be rational. (4) Nanoparticles (e.g., ZnS, POSS, upconversion nanoparticles) show complicated influences on the electro-optical performances of HPNC, which is not only dependent on the intrinsic nature of the nanoparticles, but also determined by the spatial location of nanoparticles within HPNC. Therefore, deliberate modifications of nanoparticle surface with predesigned functions are particularly important, based on which more functions like upconversion emission can be enabled in the HPNC. Furthermore, orthogonal reconstruction of holographic and upconversion emission dual images can be achieved by carefully dialing the emission properties of upconversion nanoparticles. (5) Crosstalk-free integration and cooperative-thermoresponse of holographic and fluorescent dual images are realized by boosting the synergy of an aggregation-induced emission luminogen (AIEgen) with liquid crystals in the HPNC, which opens a new door towards the design of advanced materials for high-security level anti-counterfeiting. (6) Despite the success, challenges and opportunities remain regarding HPNC: To design and synthesize red light sensitive photoinitibitors; to explore multi-image functions; to realize the flexible manufacturing.

Development of CFRTP Intermediate Substrates Using&lt;i&gt; in-Situ&lt;/i&gt; Polymerizable Thermoplastic Epoxy Resin

This study aims to create a novel method for fast mass-production of carbon fiber-reinforced thermoplastic (CFRTP) intermediate substrates by using in-Situ polymerizable thermoplastic epoxy resin, which is fed on reinforcing fibers in monomer mixture form in impregnation process and then allowed to rapidly polymerize into linearly-extended thermoplastic high polymer. Comparison between the monomer viscosity of this resin and the melt viscosity of polypropylene (PP) implied that thermoplastic epoxy resin can impregnate into fiber bundles approximately 103 times faster than PP. The investigation of resin applying method to carbon fiber fabrics revealed that linearly applying method was better than planarly applying method in terms of less voids. Finally, two types of polymerization catalysts were investigated to rapidly polymerize thermoplastic epoxy resin. As a result, as short as 2.5-minute polymerization using the phosphorous-type catalyst allowed the resin polymerize into high polymer enough to exhibit practical flexural strength of 900 MPa or more when used as the matrix of CFRTP in the volume fraction of about 50 %.

Development of new diacrylate monomers as substitutes for Bis-GMA and UDMA

ObjectiveBisphenol A-glycidyl methacrylate (Bis-GMA) and urethane dimethacrylate (UDMA) are widely used as the primary components of (meth)acrylic monomers. However, the use of Bis-GMA, which is a bisphenol A derivative, in dentistry is being questioned after bisphenol A was found to exhibit estrogenic activity. Although UDMA is being considered as a substitute for bis-GMA, the mechanical properties of cured resin composites containing UDMA are less than desirable. Therefore, in this study, we developed new alternative (meth)acrylic monomers to enhance the mechanical strength of cured composite resins. MethodsFive urethane acrylic monomers were synthesized in this study as (meth)acrylic monomer substituents to replace Bis-GMA and UDMA. The elastic modulus, strength, and breaking energy values of cured resins consisting of mixtures of the urethane acrylates and diluting monomers were determined using the three-point flexural test. The data obtained were analyzed using one-way ANOVA and the post-hoc Tukey HSD tests (p < 0.05). Viscosities of the urethane acrylic monomers were measured with a cone-plate viscometer. Refractive indices of the urethane acrylic monomers were determined with an Abbe refractometer. ResultsThe results of the three-point flexural tests revealed that the cured urethane acrylic monomer-based resin exhibited higher elastic modulus (up to 40%) and strength (up to 21%) compared to the cured UDMA-based resin. Viscosity and refractive index of the urethane acrylic monomers were between those of UDMA and Bis-GMA. SignificanceThe developed urethane diacrylates prepared from diisocyanates which have an aromatic or aliphatic ring, 1,3-bis(1-isocyanato-1-methylethyl)benzene (TMXDI), 1,3-bis(isocyanatomethyl)benzene (XDI), or norbornane diisocyanate (NBDI) are worth considering as alternative options of Bis-GMA and UDMA for restorative resin composites.

Selection of Polymerizable Functional Group of Adhesive Monolayer to Control Monomer Viscosity under Confinement in Silica Nano-gaps

We disclose that the viscosity of a polymerizable diacrylate monomer confined in a nano-gap between acryloyloxy-terminated monolayer surfaces exhibited exponential increase at a longer distance tha...

Selection of Diacrylate Monomers for Sub-15 nm Ultraviolet Nanoimprinting by Resonance Shear Measurement.

In UV nanoimprinting, the selection of monomers suitable for sub-15 nm patterning is difficult because the filling behavior of resin at this scale still remains scientifically unclear. We demonstrate sub-15 nm patterning by UV nanoimprinting using silica molds with 20, 15, and 7 nm diameter holes; however, the 7 nm diameter pillar patterns were not fabricated using hydroxy-containing monomers. The filling behavior into silica holes of around 10 nm depended on the chemical structure of the monomers. Resonance shear measurements revealed the following: (1) The viscosities of hydroxy-containing monomers confined between chlorodimethyl(3,3,3-trifluoropropyl)silane (FAS3-Cl)-modified surfaces began to increase at distances shorter than those of the monomers between unmodified surfaces. (2) The monomers confined between tridecafluoro-1,1,2,2-tetrahydrooctyltrimethoxysilane-modified surfaces were squeezed out when the surface-surface distance decreased at less than 7 nm. The measured viscosities between the FAS3-Cl-modified silica surfaces were correlated with the insufficient filling behavior into the silica holes of around 10 nm in UV nanoimprinting. Contact angle measurements provided an additional insight that a higher wettability of the monomers onto the antisticking chemisorbed monolayers resulted in imprinted patterns with higher aspect ratios. Considering the increase in the monomer viscosity in the nanospace and the wettability of monomers onto chemisorbed monolayers, we concluded that the monomer showing low viscosity under confinement and high wettability onto the mold surface was suitable for single-digit nanometer UV nanoimprinting.

BisGMA analogues as monomers and diluents for dental restorative composite materials

Current commercially available dental composite materials have certain limitations for their use, including high monomer viscosity and high polymerization shrinkage, resulting in residual stresses and interfacial gaps. This study focused on the chemical modification of resin monomer bisphenol A-glycidyl methacrylate (bisGMA), so as to reduce the viscosity and polymerization shrinkage. In this design, the hydroxyl groups of bisGMA were transformed into ester groups with various alkyl chain length and branching. The modified monomers showed promising properties including reduced viscosity, reduced polymerization shrinkage, increased hydrophobicity, increased degree of double bond conversion, and improved mechanical properties of the resulting dental resin composites. The structure/property relationships of the new monomers were investigated, and optimal monomer structures were identified for dental composites with improved properties.

Nanometer-Resolved Fluidity of an Oleophilic Monomer between Silica Surfaces Modified with Fluorinated Monolayers for Nanoimprinting

Ultraviolet (UV) nanoimprinting has the potential to fabricate sub-15 nm resin patterns, but the interfacial fluidity of organic monomers near monomer liquid/mold solid interfaces related to filling nanoscale mold recesses with UV-curable resins still remains unclear. In this study, we demonstrated that surface forces and resonance shear measurements were helpful to select a surface modifier appropriate for silica mold surfaces for UV nanoimprinting with the low-viscosity monomer 1,10-decanediol diacrylate. Surface forces between silica surfaces mediated with the diacrylate monomer and fluidities of the monomer were investigated with nanometer resolution. Chemical vapor surface modification of silica surfaces with chlorodimethyl(3,3,3-trifluoropropyl)silane (FAS3-Cl) and tridecafluoro-1,1,2,2-tetrahydrooctyltrimethoxysilane (FAS13) gave fluorinated silica surfaces with root-mean-square roughness of less than 0.24 nm suitable for the measurements. When the distance D between two silica surfaces was decreased stepwise in the range of 0-30 nm, monomer viscosity between cleaned silica surfaces increased markedly at D < 6 nm. Surface modification with FAS3-Cl suppressed this increase of interfacial monomer viscosity. In contrast, FAS13-modified silica surfaces caused a jump-in phenomenon at approximately D = 7-9 nm, suddenly decreasing to D = 1 nm as the monomer fluid layer was squeezed out. We concluded that FAS3-Cl was appropriate as a fluorinated surface modifier for silica molds used in UV nanoimprinting with an oleophilic low-viscosity monomer, because the chemisorbed monolayer maintained low monomer viscosity near the surface/monomer interface, in addition to its low surface free energy and short CF3CH2CH2- group.

Flexible and Bio‐Based Nonisocyanate Polyurethane (NIPU) Foams

The amine cure of cyclic carbonate blends, derived from renewable resources and carbon dioxide, in the presence of a liquid fluorohydrocarbon as physical blowing agent with no ozone depletion potential, enables the facile tailoring of flexible bio‐based nonisocyanate polyurethane (NIPU) foams. Unlike conventional PU foams, neither isocyanates nor phosgene or aromatic amines are required as intermediates in NIPU foaming. Typically, rigid cyclic carbonates such as carbonated trimethylolpropane glycidylether (TMPGC) are blended together with the corresponding flexible cyclic carbonate such as ethoxylated TMPGC (EO‐TMPGC) which lowers monomer viscosity and reactivity. This is reflected by higher pot life and gelation times for the cure with hexamethylene diamine (HMDA), improving NIPU foam processing. With increasing EO‐TMPGC content, rigid TMPGC/HMDA‐NIPU foams are rendered flexible and soft, as verified by simultaneously declining storage modulus and glass transition temperature. In this NIPU foam family, the TMPGC/EO‐TMPGC (60 wt%/40 wt%) blend cured with HMDA in the presence of Solkane 365/227 affords flexible NIPU foams exhibiting low density, very good mechanical hysteresis, and tailored hardness, meeting the demands of various applications like automotive seating. Emission tests confirm the absence of critical compounds mentioned in the global automotive declarable substance list. image

Influence of nanoparticle morphology on reaction kinetics, particle size and rheology in acrylic latex

ABSTRACTOrganic/inorganic (O/I) composite latexes combine the best attributes of inorganic solids with the processability, lightweight and handling advantages of organic polymers. There are common methods to produce polymer nanocomposites: melt compounding, in-situ polymerization and solution mixing. Emulsion polymerization is an unique chemical process widely used to produce waterborne resins with various colloidal and physicochemical properties. This free radical polymerization process involves emulsification of the relatively hydrophobic monomer in water by an oil-in-water emulsifier, followed by the initiation reaction with a water insoluble initiator. This research focuses on the synthesis and reactions kinetics of polyacrylic latex with the incorporation of various nanospheres (SiO2, TiO2, Al2O3 and Fe2O3), and layered silicate (Bentonite nanoclay) nanoparticles via emulsion polymerization. The influence of nanoparticle concentration on reaction kinetics was also investigated. The results showed that the concentration of nanoparticles has significant influence on the monomer conversion, particle size, coagulum content and viscosity of the emulsion. Furthermore, the nanostructured emulsions were shear thinning, exhibiting a power-law behavior, and the viscosity was influenced by the nanoparticle morphology.

Control of microstructure and gradient property of polymer network by photopolymerizable silicone-containing nanogel

This article reports a new type of silicone-containing nanogel. The nanogel was dispersed in triethylene glycol dimethacrylate (TEGDMA) in increments between 10 and 40 wt % with a series of properties evaluated before and after polymerization. The nanogel raised monomer viscosity but did not significantly affect reaction kinetics or final conversion attained during photopolymerization. Polymerization stress was reduced progressively with the addition of nanogel with a significant delay in the onset of stress observed compared with the control. The self-floating ability of the nanogel was demonstrated by elemental analysis and X-ray photoelectron spectroscopy. As a result, the nanogel spontaneously formed a concentration gradient in the monomer prior to photopolymerization, leading to a gradient change of properties of the polymer. The research on surface morphology and elemental composition of PTEGDMA indicated the enrichment of the nanogel on the polymer surface, which resulted in enhanced hydrophobic character along with altered surface microstructure. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2830–2840

Shear-thinning and isotropic–lamellar–columnar transition in a model for living polymers

A model consisting of short polymer segments, capable of self assembling to form a branched network through the interaction of their ends, is considered. We investigate the mechanistic origins of a shear induced isotropic–lamellar–columnar transition, reported earlier in this model for living polymers. We find that these structures arise only in the presence of a potential barrier in the end point interaction between polymer segments. To elucidate the role played by long range solvent mediated forces, we have carried out simulations with and without the hydrodynamic interactions between the polymers and have seen that these structures are present in both these cases. We also show that the shear induced layering in these systems is a bulk phenomena and boundary interactions have little effect on the transition. The monomer volume fraction and viscosity of the background solvent are shown to have significant effects on determining the morphology of the flow-induced structures. We demonstrate that the structures obtained are indeed non-equilibrium states induced by the shear.

Shrinkage strain – Rates study of dental composites based on (BisGMA/TEGDMA) monomers

The viscosity of the initial monomer mixture and the chemical structure of the monomers are both important variables in the kinetic behavior of resin composites. This paper aims to determine the effect of opaque mineral fillers and monomer ratios on the shrinkage strain-rate and time at maximum shrinkage strain (Smax) rate, of experimental composites based on (BisGMA/TEGDMA) monomers. Polymerization shrinkage and the degree of conversion (DC) of resin composites are closely related manifestations of the same process. The proportionality of these two properties was also investigated by studying the variation of the ratio: (total shrinkage strain/degree of conversion): (Smax/DC), as a function of mineral filler contents and monomer ratios.Resin composites were prepared by mixing different monomer ratios of (BisGMA/TEGDMA) with camphoroquinone and dimethyl aminoethyl methacrylate (DMAEMA) as photo-initiator system. Five different radiopacifying filler agents: La2O3, BaO, BaSO4,·SrO and ZrO2 at various volume fractions ranging from 0 to 80wt.% were added. The samples were cured at ca. 550mW/cm2. The shrinkage strain-rate, was calculated from the derivative of shrinkage strain using numerical differentiation. The shrinkage strain was measured by the bonded-disk technique at room temperature. Degree of conversion was calculated using FTIR/ATR spectroscopy.The results revealed that the fraction of opaque filler had no significant effect on the shrinkage strain-rate and on the time at maximum shrinkage strain-rate but these two parameters are closely related to the monomer ratios and viscosity of the organic matrix. The results have confirmed the proportionality of the shrinkage strain and DC and showed that the filler contents and monomer ratios would not affect this proportionality.

Research of Silica Particles Dispersion in Polymer Matrix Under Acoustic Levitation

Series of resins consisting different amount of silica particles with different sizes and surface properties were prepared as suspended samples under an acoustic levitator. The resulting composites after curing under irradiation have been investigated. Fracture surface morphologies of the resins were compared to those with same composition prepared in a normal gravity field via scanning electron microscopy. The results showed that except for such factors like particle sizes, surface properties, particles concentration, and monomer viscosity, the microgravity state produced by acoustic levitation could also be an element that affects silica particles dispersion in the resins.

Use of laboratory-grown bacterial alginate in copper removal

Industrial production leads to toxic heavy metal pollution in water bodies. Copper is one of the examples that requires removal from effluents before being discharged. It is difficult and sometimes very expensive to remove toxic heavy metals by conventional treatment techniques. This study aims to remove copper by the use of bacterial alginate as a non-conventional technique. Bacterial alginates (natural polymers composed of mannuronic and guluronic acid monomers) were synthesized by Azotobacter vinelandii ATCC(®) 9046 in a laboratory fermentor under controlled environmental conditions. The alginates produced, with a range of different characteristics in terms of monomer distribution and viscosity, were investigated for maximum copper uptake capacities. The average copper uptake capacities of alginates produced were found to be about 1.90 mmol/L Cu(2+)/g alginate. Although the GG-block amount of alginates was varied from 12 to 87% and culture broth viscosities were changed within the range of 1.47 and 14 cP, neither the block distribution nor viscosities of alginate samples considerably affected the copper uptake of alginates.

Preparation of porous honeycomb monolith from UV‐curable monomer/dioxane solution via unidirectional freezing and UV irradiation

AbstractA well‐ordered micrometer‐scale honeycomb monolith porous polymeric material with aligned channels was successfully prepared from UV‐curable urethane diacrylate monomer and 1,4‐dioxane solutions by conducting unidirectional freezing, photopolymerization, and sublimation of the frozen solvent. UV light was irradiated into the frozen solution, and the monomer was photopolymerized and solidified in a template of 1,4‐dioxane crystals. The effects of monomer concentration, freezing rate, and viscosity of the solution on the porous structure were investigated. High monomer concentration increases the solution viscosity, decreases the diffusivity of solute, and consequently, increases the degree of the supercooling. Thus, the pore size was decreased, and the channel wall feature was changed from smooth to dendrite as the solution viscosity increased. Pre‐UV irradiation was also conducted before the unidirectional freezing process so as to control the solution viscosity and change the porous structure. Experiments elucidated that the solution viscosity is one of the key factors of determining the cell structure in the unidirectional freezing technique. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Dimethacrylate network formation and polymer property evolution as determined by the selection of monomers and curing conditions

Objectives This overview is intended to highlight connections between monomer structure and the development of highly crosslinked photopolymer networks including the conversion dependent properties of shrinkage, modulus and stress. Methods A review is provided that combines the polymer science and dental materials literature along with examples of relevant experimental results, which include measurements of reaction kinetics, photorheology as well as polymerization shrinkage and stress. Results While new monomers are continually under development for dental materials applications, mixtures of dimethacrylate monomers persist as the most common form of dental resins used on composite restorative materials. Monomer viscosity and reaction potential is derived from molecular structure and by employing real-time near-infrared spectroscopic techniques, the development of macromolecular networks is linked to the evolution of polymerization shrinkage (measured by linometer), modulus (measured by photorheometer), and stress (measured by tensometer). Relationships between the respective polymer properties are examined. Significance Through a better understanding of the polymer network formation and property development processes using conventional dimethacrylate monomer formulations, the rational design of improved materials is facilitated with the ultimate goal of achieving dental polymers that deliver enhanced clinical outcomes.

The Polymerization and Performance of Fluorinated Acrylic Copolymer with Low Surface Energy

Fluoro-polymer is of great importance as coating materials because of their excellent resistance to high temperature, chemicals and organic solvents. In the interest of researching low surface energy coating, a kind of copolymer was prepared by solution polymerization method, using methyl methacrylate, butyl acrylate, 2-hydroxyethyl acrylate and perfluoroalkyl ethyl acrylate whose length of fluorinated carbon chain was from 6 to12. Solid content, monomer conversion rate and viscosity of the copolymer were measured. Parallel experiments were separately carried out with different contents of initiator and fluorinated monomer. The results showed that the water contact angle of the film becomes bigger with the increase of the content of fluorinated monomer, with the biggest value in 108° when the content of fluorinated monomer content is 30 wt%, but only changing little after content of fluorinated monomer reaches up 15 wt%. The results indicated that the copolymer can offer the best property combination when the contents of fluorinated monomer and initiator were 15 wt% and 1.8 wt%.

Magnetic Epoxy Resin Nanocomposites Reinforced with Core−Shell Structured Fe@FeO Nanoparticles: Fabrication and Property Analysis

Epoxy resin nanocomposites reinforced with various loadings of core−shell structured nanoparticles (Fe@FeO) are prepared using a surface wetting method. Nanoparticle loading effect on the viscosity of epoxy monomers is well-correlated to Cross’ rheological model. Dynamic mechanical analysis (DMA) results reveal that the glass transition temperature is increased by 10 °C with the addition of nanoparticles, which is surprisingly independent of the particle loadings. The saturation magnetization (Ms) of the 20 wt % Fe@FeO/epoxy nanocomposites is 17.03 emu/g, which is about 15.8% of that of the pure nanoparticles. Meanwhile, the coercivity increases from 62.33 to 202.13 Oe after the nanoparticles are dispersed in the epoxy matrix. The electrical conductivity percolation is found to be around 5−10 wt %, where the resistance of the nanocomposites sharply decreases by 6 orders of magnitude. Thermal stability and tensile properties of the pristine epoxy and nanocomposites are also investigated in this work.