Acrylic Composites Research Articles

Mechanical and thermal properties of cationic ring-opening o-cresol formaldehyde epoxy/polyurethane acrylate composites enhanced by reducing graphene oxide

Polyurethane acrylate (PUA) and o-cresol formaldehyde epoxy resin (o-CFER) is synthesized. The PUA/o-CFER glass fiber-reinforced composites cured by free radical/cationic ring-opening reaction are modified by the reducing graphene oxide (r-GO). Effect of r-GO on the thermal and mechanical properties of PUA/o-CFER glass fiber-reinforced composites are characterized by FTIR, DMA and TGA. The result of FTIR shows that the system has cured completely. DMA analysis indicates that this system has better compatibility, and the glass transition temperature (T g) decreases with increasing r-GO content. TGA analysis shows that the initial thermal degradation temperature (T id) and activation energy (E a) enhance 13.1 °C and 3.12 kJ/mol, respectively. The tensile and impact strength of glass fiber-reinforced composites are approximately 50 and 60 % higher than those without r-GO. It is shown that the r-GO can enhance the mechanical properties and thermal stability of composites.

Features of using photocurable acrylic composition to create the immersion-formed layer for lenticular lenses

The possibilities of creating a monolithic lenticular lens with an increased focal length capable of forming a view zone of an autostereoscopic image at a distance of at least 3–7 m away from the screen, are studied. At the optimal ratio between the refractometric, viscosity, and chemical parameters of liquid composition, the use of polymerizable photocurable acrylic compositions based on oligourethane acrylates as the immersion medium gives rise to an immersion-formed polymer with optical parameters ensuring the desired focal length of a monolithic lenticular lens.

Carbon‐fiber‐reinforced acrylonitrile–styrene–acrylate composites: Mechanical and rheological properties and electrical resistivity

ABSTRACTThe aim of this study was to improve the mechanical properties of an acrylonitrile–styrene–acrylate copolymer (ASA) with the help of carbon fibers (CFs). Additionally, the effects of the CFs on the morphology, rheological properties, dynamical mechanical properties, electrical resistivity, and heat resistance of the ASA composites were studied with scanning electron microscopy, rotational rheometry, and dynamic thermomechanical analysis (DMA). The mechanical properties of the ASA composites were enhanced largely by the CFs. The maximum tensile strength of the ASA/CF composites reached 107.2 MPa. The flexural strength and flexural modulus also reached 162.7 MPa and 12.4 GPa, respectively. These findings were better than those of neat ASA; this was attributed to the excellent interfacial adhesion between the CFs and ASA resin. Rheological experiments proved that the viscosity and storage modulus (G′) values of the ASA/CF composites did not increase until the CF content reached 20%. The DMA outcomes confirmed that the glass‐transition temperature of the ASA composites was elevated from 120.6 to 125°C. Importantly, the G′ values of the composites with 20 and 30% CFs showed a large increase during heating. In addition, the ASA/CF composites exhibited excellent conductivity and heat resistance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43252.

Effect of inorganic nanopowders on properties of acrylic composites

The effect exerted by small amounts (up to 0.5 wt %) of nanopowders of silicon, titanium oxide, aluminum oxide, iron oxide, silicon carbide, and boron carbide on the time in which the glassy state is reached in radical polymerization of methyl methacrylate in the bulk, on the molecular mass of the resulting polymer, and on some operation characteristics of highly filled acrylic nanocomposites containing, along with nanofillers, also coarsely dispersed mineral fillers was studied. The use of nanodispersed titanium and aluminum oxides as components of the above polymeric composites allows the compression strength to be enhanced by more than 10%, and the bending tensile strength, by more than 20%.

Frequency and Temperature Dependence of Dielectric Behaviors for Conductive Acrylic Composites

ABSTRACTIn this study, acrylic‐based conductive polymeric composite thin films were prepared by in situ chemical polymerization of pyrrole (Py) in the case of ammonium persulfate (APS) and iron(III) chloride (FeCl3). Composite thin films were produced by the solution casting method. The effect of polypyrrole (PPy) content and the type of oxidant on the morphological and dielectric properties were investigated. Temperature‐ and frequency‐dependent dielectric properties were also studied in a frequency domain starting from 0.01 Hz to 10 MHz and in a temperature domain from 35 to 195°C. The results revealed that the dielectric constant and dielectric loss increased, whereas temperature and the highest dielectric values were obtained in the case of APS. The density of interconnected pores enwrapped with PPy under the surface improved the electrical/dielectric properties of the composite thin films.

Influence of dysprosium addition on the structural, morphological, electrical and magnetic properties of nano-crystalline W-type hexaferrites

Dysporium (Dy)-substituted W-type barium hexaferrites were prepared by the citrate sol–gel-method. Crystalline structure, morphology, magnetic properties, DC resistivity and microwave absorption properties of BaNi2Dy x Fe16−x O27 (x = 0–0.9) were studied using X-ray diffraction, transmission electron microscope (TEM), vibrating sample magnetometer and vector network analyzer and sensitive source meter, respectively. Single-phase W-type barium hexaferrites, with a chemical composition of BaNi2Dy x Fe16−x O27 (x = 0–0.9), were formed by being heated at 1250°C for 4 h in air. The magnetic properties such as saturation magnetization (M s ), and coercivity (H c) were calculated from hysteresis loops. Hysteresis loop measurements show that the coercivity values lie in the range of 530–560 Oe with increasing Dy content. It was also observed that magnetization decreases with the increase of Dy content. The DC resistivity was observed to increase from 0.83 × 107 to 6.92 × 107 Ω cm with increasing Dy contents due to the unavailability of Fe3+ ions. Microwave absorption properties of hexaferrite (70 wt%)–acrylic resin (30 wt%) composites were measured by the standing-wave-ratio (SWR) method in the range from 12 to 20 GHz. For sample with x = 0.6, a minimum reflection loss of −40 dB was obtained at 16.2 GHz for a layer of 1.7 mm in thickness. Sample with x = 0.9 had wide bandwidth absorption in the frequency range of 13.5–18 GHz with reflection losses less than −15 dB. Meanwhile the minimum reflection point shifts toward higher frequency with the increase of Dy content.

Effect of silver-supported materials on the mechanical and antibacterial properties of reinforced acrylic resin composites

The aim of this study was to investigate the effect of silver-supported material (Novaron (N)) in acrylic resin (poly(methyl methacrylate) (PMMA)) composites, which reinforced with zirconium dioxide nanoparticles (nano-ZrO2) and aluminum borate whiskers (ABWs), on the mechanical behavior, antibacterial properties and cytotoxicity. Silanized ABWs (4wt%) and nano-ZrO2 (2wt%) were mixed with PMMA powder to obtain nano-ZrO2–ABW/PMMA matrices. Various amounts of Novaron particles were incorporated into the matrices and the pure PMMA to test the flexural strength. In addition, Streptococcus mutans (S. mutans) and Canidia albicans (C. albicans) biofilms on the specimen surface and in the culture medium were investigated for metabolic activity and colony-forming units (CFUs). Extracts taken in the cell culture medium of the specimens were used to evaluate cell viability. Results showed that the silanized nano-ZrO2 and ABWs could improve the flexural strength of composites compared with the pure PMMA. Novaron itself had no mechanical function for composites while it had synergistic effect when it mixed with silanized nano-ZrO2 and ABWs. And when 4wt% (N-4) Novaron mixed in nano-ZrO2–ABW/PMMA composites, flexural strength achieved an increase of 44%, getting the maximum value. For the antibacterial properties, the values of MTT and CFUs of S. mutans and C. albicans biofilms on the composites surface were greatly reduced (p<0.05) with the higher proportion of Novaron, and no significant difference was found in the culture medium. The composites did not have an adverse affect on fibroblast growth in this study (p>0.05).

Preparation and characterization of microencapsulated n-octadecane as phase change material with different n-butyl methacrylate-based copolymer shells

Microcapsules containing n-octadecane with different n-butyl methacrylate (BMA)-based copolymer shells were fabricated by a suspension-like polymerization method. n-butyl acrylate (BA), methacrylic acid (MAA) and acrylic acid (AA) were employed as monomers to copolymerize with BMA. The surface morphologies of the microencapsulated phase change materials (MicroPCMs) were studied by scanning electron microscopy (SEM). The thermal properties, thermal reliabilities and thermal stabilities of the MicroPCMs were investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The temperature-regulated properties of the MicroPCMs were determined by an infrared thermography. The incorporation of MAA or AA to the acrylic composition of the polymer shells led to an increase in both the heat storage capacities and thermal stabilities of the MicroPCMs. The MicroPCMs with P(BMA-co-MAA) exhibit a greater heat capacity and thermal stability compared with the MicroPCMs with P(BMA-co-AA). The MicroPCMs with P(BMA-co-MAA) have the highest latent heats of melting (144.3J/g) and crystallization (152.9J/g) as well as the highest thermal resistant temperature (249°C). The phase change temperatures and enthalpies of the MicroPCMs varied little after 1000 thermal cycles. Thermal images showed that the gypsum board containing the MicroPCMs with BMA-based copolymers as shells, especially with P(BMA-co-MAA) and P(BMA-co-AA) as shells, possessed temperature-regulated properties. As a result, the MicroPCMs with BMA-based copolymers as shells have good thermal energy storage and thermal regulation potentials, such as solar energy-saving building materials.

Radiation-curing of acrylate composites including carbon fibres: A customized surface modification for improving mechanical performances

Abstract The lower transverse mechanical properties of radiation-cured acrylate-based composites reinforced with carbon-fibre with respect to the thermosettable analogues was investigated from the viewpoint of chemical interactions at the interface between the matrix and the carbon material. XPS analysis of representative commercial carbon fibres revealed the presence of a significant amount of chemical functions potentially exerting an adverse effect on the initiation and propagation of the free radical polymerization initiated under high energy radiation. The EB-induced polymerization of n -butyl acrylate as a simple model monomer was conducted in the presence of various aromatic additives exhibiting a strong inhibiting effect, whereas thiols efficiently sensitize the initiation mechanism and undergo transfer reactions. A method based on the surface modification of sized fibres by thiomalic acid is proposed for overcoming the localized inhibition phenomenon and for improving the mechanical properties of the resulting acrylate-based composites.

Effect of Nd Substitution on Magnetic and Microwave Absorption Properties of Nanocrystalline Sr(MnSn)0.5Fe11O19

The preparation of Sr1-xNdx(MnSn)0.5Fe11O19 M-type hexaferrites powders by a citrate sol-gel method was investigated. The samples were determined by X-ray diffraction (XRD) and transmission electron microscope (TEM). Microwave absorption properties of hexaferrite- acrylic resin composites were measured using SWR (standing-wave-ratio) method in the range of 12 to 20 GHz. It was shown that small amounts of Nd+3 substitution could significantly modify the microwave electromagnetic parameters. Furthermore, the investigation indicated that substitution of Nd+3 ions for Sr+2 ions in Sr(MnSn)0.5Fe11O19 resonant frequency would move toward higher frequency. The results showed that the powder possesses excellent microwave absorption properties. A minimum reflection loss of –43 dB was observed for the composite, where x = 0.03. A broad bandwidth of microwave absorption (with a –10 dB reflection loss as a reference) is predicted in the composite samples containing the ferrite powders of x=0.02, and x=0.03 in Ku-band frequencies. Keywords: Chemical synthesis, magnetic materials, magnetic properties, nano crystalline materials.

Avaliação do efeito da Moagem no desempenho e na caracterização DRIFT-NIR de microbicidas na superfície de tintas comerciais

In this work, an evaluation is presented of the FT-IR diffuse reflectance spectroscopy (DRIFT) technique in the NIR region (DRIFT/NIR) for characterizing OIT, diuron and carbendazim in acrylic paint compositions containing these ground microbicides reduced to particle sizes around 5 µm. The DRIFT-NIR analysis showed analytical bands at 6077, 5799, 5681 and 4335 cm - 1 for OIT, 4943 and 4435 cm - 1 for carbendazim, with the absorption at 4943 cm - 1 being possibly attributed to diuron, as well. The presence of microbicides in the dry paint film was also confirmed by HPLC and microbiological analyses, which revealed that the ground microbicides are more effective for the microbiological control, enhancing the preservation of the dry paint film compared to the non-ground microbicides. This allows the microbicides to be used in lower concentrations in paints and coating materials, thus saving financial resources and lowering the toxicological impacts to humans and the environment.

Influence of surface treatments on fracture strength of implant-supported provisional-crowns

Purpose: The purpose of this studywas to evaluate fracture strength between acrylic resin tooth and composite resin of immediate implant-supported provisional crown after several surface treatments to improve bond strength. Methods and materials: One hundred and twenty screwretained implant-supported provisional crowns were prepared using incisor acrylic resin teeth. Teeth were ground in a concave shape and distributed into 10 groups (n=12) according to the tooth surface treatment: (1) no surface treatment (control), (2) methyl-methacrylate (MMA) monomer for 180 s, (3) metal primer (MP) for 30 s, (4) bonding system (BS) for 30 s and light curing for 20 s, (5) MMA treatment additional to 2:1 (g/g) composite resin/auto-polymerized acrylic resin (CR-AR) mix, (6) alumina sandblasting (Al3O2), (7) Al3O2 additional to MMA treatment, (8) Al3O2 additional to MP treatment, (9) Al3O2 additional to BS treatment and (10) Al3O2 additional to MMA, and CR-AR mix. After tooth surface treatment the lingual surface was reconstructed with composite resin in layers. Subsequently specimens were submitted to thermal cycling (1× 104 cycles, 5–55 ◦C). For the mechanical test each crown was screwed in an embedded implant and afterwards essayed to fracture strength. The static mechanical test was performed with a crosshead speed of 0.5mm/min until the fracture of specimen. Data from fracture strength assay were non-normally distributed (Kolmogorov–Smirnov, P 0.05). Stereomicroscope analysis showed adhesive failure in all specimens of groups 1, 3, 7 and 8. Groups 2 and 7 showed a large amount of adhesive failure followed by some mixed failure, groups 4 and 9 showed a large amount of mixed failure followed by some adhesive failure. Groups 5 and 10 showed cohesive failure in all specimens. Conclusion: Bond strength between acrylic resin tooth and composite was improved by the use of bonding system and application of MMA treatment additional to 2:1 (g/g) CR-AR mix. Alumina sandblasting did not improve bond strength in a significant way.

Grafting acrylate functionalities at the surface of carbon fibers to improve adhesion strength in carbon fiber–acrylate composites cured by electron beam

Acrylate functionalities were grafted at the surface of carbon fibers in order to improve the adhesion strength with an acrylate matrix cured by electron beam. An isocyanate bearing aliphatic urethane acrylate was used as a coupling agent. As revealed by X-ray photoelectron spectroscopy, the isocyanate groups reacted with carboxylic acids and hydroxyl groups located at the surface of the fiber, leading to a covalent bonding of the acrylate groups. The adhesion strength was measured by a micromechanical test derived from the pull-out test. A significant improvement of the interfacial shear strength was obtained (+91%) with an electron beam curing. For comparison, an isothermal cure by UV was also investigated and led to the same level of adhesion strength. The improvement was also proved by an increase in the 90° flexural strength of unidirectional composites (+38%). Grafting functionalities that were compatible with the radical mechanism of the polymerization of the matrix appeared to be a promising strategy for the improvement of the mechanical properties of carbon fiber–acrylate composites cured by electron beam.

Biodegradation of resin composites and adhesives by oral bacteria and saliva: A rationale for new material designs that consider the clinical environment and treatment challenges

ObjectiveTo survey the recent literature from the late 1980s to recent years in order to assess the relationship between resin degradation, catalyzed by biological factors, and clinical failure outcomes such as marginal breakdown. MethodsThe literature shows that degradation occurs in many manufacturers’ products despite varied vinyl acrylate compositions. The authors examine salivary enzyme activity and their ability to degrade the polymeric matrix of resin composites and adhesives, as well as oral microorganisms that can promote demineralization of the tooth surface at the marginal interface. A survey of recent research relating matrix metalloproteinase (MMPs) to the degradation of the exposed collagen at the dentin adhesive interface is also discussed in the context of marginal breakdown. ResultsThe literature provides strong support that together, the above factors can breakdown the marginal interface and limit the longevity of resin composite restorations. The authors have found that the field's current understanding of resin biodegradation in the oral cavity is just beginning to grasp the role of bacteria and enzymes in the failure of resin-based restorations. SignificanceKnowledge of these biodegradation processes is pertinent to areas where innovative strategies in the chemistry of restorative materials are anticipated to enhance the longevity of resin composites.

Mechanical and microwave absorbing properties of in situ prepared hydrogenated acrylonitrile–butadiene rubber/rare earth acrylate composites

Lanthanum oxide (La2O3), samarium oxide (Sm2O3) and acrylic acid (AA) were in situ reacted in hydrogenated acrylonitrile–butadiene rubber (HNBR) to obtain HNBR/acrylate and HNBR/acrylate/multi-walled carbon nanotubes (MWNTs) composites. Fourier transform infrared spectrum analysis showed the absorption peaks of carbon–carbon double bonds of the acrylates became weak after curing at elevated temperatures, indicating the self-polymerization of acrylates and their participation in crosslinking reactions of HNBR. The morphology of composites was characterized by scanning electron microscopy and X-ray diffraction analysis, and the well dispersion of acrylates was attributed to the in situ reactions during curing. The tensile strength of HNBR/La2O3/AA/MWNTs and HNBR/Sm2O3/AA/MWNTs composites reached 25.2 and 17.6MPa, and their stress at 100% extension reached 8.4 and 7.4MPa, indicating the good reinforcement of in situ formed acrylates and MWNTs on HNBR. The glass transition temperature of HNBR increased to a limited extent because of the addition of AA and La2O3. The HNBR/La2O3/AA/MWNTs and HNBR/Sm2O3/AA/MWNTs composites had good microwave absorbing properties, with the maximum reflection loss of −9.0 and −13.5dB, respectively, and broad absorption bands.

Polyacryl–nanoclay composite for anticorrosion application

Polyacryl–nanoclay composites are new class of materials obtained by dispersing montmorillonite clay nanoplatelets (nanoclay) into the polymer matrix. In present work we investigate and confirmed that montmorillonite nanoclay significantly enhances barrier properties of acrylic composite. Two stage of dispersion process was used to prepare polyacry–nanoclay composites. Different percentages of montmorillonite clay nanolayers were added to polyacryl dispersion and applied on steel panel with 0% (w/w), 1% (w/w), 2% (w/w) and 4% (w/w) of nanoclay as composites. Performance of nanoclay intercalation in polyacryl composite was measured by X-ray diffraction (XRD) and the structure characteristics of samples were analyzed with transmission electron microscopy (TEM). The effectiveness of prepared nanocomposites was identified by the hardness measurements and mechanical properties. Further anticorrosion characteristics, especially barrier properties were indirectly detected by electrochemical impedance spectroscopy (EIS). This method was also used for the determination of montmorilonite nanoclay optimal concentration in acrylic composite where optimal barrier properties were achieved.

Effect of Ho3+ substitution on magnetic and microwave absorption properties of Sr(ZnZr)0.5Fe12O19 hexagonal ferrite nanoparticles

Sr1−x Ho x (ZnZr)0.5Fe11O19 (x = 0.03, 0.06 and 0.09) hexaferrite nanocrystallites of average sizes in the range of 46–60 nm are synthesized by the citrate sol–gel method. Crystalline structure, morphology, magnetic properties, and microwave absorption properties of powders were studied via X-ray diffraction, field emission scanning electron microscope vibrating sample magnetometer, and vector network analyzer, respectively. The magnetic properties such as saturation magnetization (M s ) and coercivity (H c ) were calculated from hysteresis loops. The XRD patterns show that the main phase is M-type strontium hexaferrite without other impurity phases. Microwave absorption properties of hexaferrite (70 wt%)–acrylic resin (30 wt%) composites were measured by the standing-wave-ratio (SWR) method in the range from 12 to 20 GHz. Results showed that substitution of Ho3+ ions for Sr2+ ions in Sr(ZnZr)0.5Fe11O19 resonance frequency moves to higher frequency. For samples with x = 0.03, a minimum reflection loss of −42 dB was obtained at 16.6 GHz for a layer of 1.7 mm in thickness. It was concluded that the prepared composites could be good candidates for electromagnetic compatibility and other practical applications at high frequency.

Structural self-organization mechanism of ZnO nanoparticles in acrylate composites

Transparent homogeneous polymeric composite media have been obtained and investigated that contain up to 14 wt. % of ZnO nanoparticles. It has been established that the physical properties of the material, such as light scattering, Brinell hardness, and moisture absorption, vary nonmonotonically as the concentration of nanoparticles increases as a result of the modification of the internal structure of the nanocomposites. The nanocomposite structure has been investigated by the methods of IR spectroscopy and atomic-force microscopy. By comparison with the unmodified polymeric matrix, the hardness is not degraded, while the light scattering and moisture absorption are reduced. Because the active groups of one of the monomers (the carboxyl groups) interact with the surface of the nanoparticles, the latter are uniformly distributed over the entire volume of the material, and this forms an optically homogeneous nanocomposite medium. The ZnO nanoparticles are photocatalysts and centers of the polymerization process.

Poly (methyl methacrylate) grafted halloysite nanotubes and its epoxy acrylate composites by ultraviolet curing method

Addition of natural inorganic nanotubes to epoxy acrylate resin can significantly improve their mechanical properties. Halloysite nanotubes are one kind of novel reinforcing and toughening materials for polymers. In the present work, halloysite nanotubes were compounded to epoxy acrylate resin to improve the wear resistance and toughness of the composites. To improve the embedding of halloysite nanotubes within the epoxy acrylate resin matrix, the halloysite nanotubes surface was grafted by poly (methyl methacrylate). The morphology of the grafted halloysite nanotubes particles demonstrates a core-shell structure with halloysite nanotubes as the core and the grafted polymer as the shell. Poly (methyl methacrylate) was chemically attached to the halloysite nanotubes particles as indicated by the Fourier transform infrared and X-ray photoelectron spectroscopy results. The poly (methyl methacrylate) grafted halloysite nanotubes (poly (methyl methacrylate)- g-halloysite nanotubes) then compounded with epoxy acrylate resin and composites are formed via ultraviolet-curing method. The hardness, flexibility, impact resistance and wear resistance of epoxy acrylate/poly (methyl methacrylate)- g-halloysite nanotubes composites were markedly improved in comparison with that of neat epoxy acrylate. The improvement was correlated to the well-dispersed halloysite nanotubes and the interfacial bonding between epoxy acrylate resin and poly (methyl methacrylate)- g-halloysite nanotubes. The well dispersion of halloysite nanotubes in the matrix is attributed to the modification on the surface of halloysite nanotubes.

The effect of chlorhexidine on plaque index and mutans streptococci in orthodontic patients: A pilot study

Aim: The purpose of this study was to assess chlorhexidine effects on plaque index and salivary levels of mutans streptococci (MS) when used as the immersion solution for removable orthodontic appliances and added to their acrylic resin composition. Methods: Forty-five patients (6 to 12 years old) were randomly assigned into three groups with 15 patients each. Group I (control)—without orthodontic appliances disinfection; Group II—removable orthodontic appliances which had been immersed in 0.12% chlorhexidine digluconate overnight (8 hours), and Group III—orthodontic appliances in which 0.12% chlorhexidine digluconate solution had been incorporated into their resin composition. Saliva was collected for quantification of MS and evaluation of plaque index was performed before and after installation of orthodontic appliance at 0, 2, 4, 6, 8, and 10 weeks. Data were analyzed by using analysis of variance. Results: Number of MS colonies in saliva and plaque index showed no statistically differences among groups at the different periods (p > 0.05). Conclusions: It could be concluded that chlorhexidine incorporation into the acrylic resin of removable orthodontic appliances at 0.12% concentration and immersion of the appliance into 0.12% chlorhexidine solution were not effective in reducing plaque index and the number of MS in saliva.