Mechanical,thermal and dielectric properties of BDM/DBA/HBPSi composites

N, N′-4, 4′-bimaleimide diphenyl methane (BDM), diallylbisphenol A (DBA) and hyperbranched polysiloxane (HBPsi) are performed to fabricate the BDM/DBA/HBPSi composites by one-step method. The contents of HBPSi affecting on the mechanical, thermal and dielectric properties of the BDM/DBA/HBPSi composites are investigated. Results show that the appropriate incorporation of HBPSi into BDM/DBA not only significantly improves the toughness, but also improves the heat resistance and dielectric properties of the BDM/DBA/HBPSi composites. The outstanding comprehensive properties of BDM/DBA/HBPSi composites indicate great potentiality in fabricating advanced polymeric composites.     

Preparation and electrochemical properties of polyaniline/α‐RuCl3.xH2O composites for supercapacitor

Polyaniline/α‐RuCl₃.xH₂O composites were successfully synthesized by an in‐situ chemical polymerization and employed as new electrode materials in supercapacitors. The synthesized composites were characterized physically by scanning electronic microscope (SEM). The electrochemical capacitance performance of these composites was investigated by cyclic voltammetry, galvanostatic charge–discharge tests and AC impedance spectroscopy with a three‐electrode system in 1 mol l⁻¹ NaNO₃ aqueous solution electrolyte. The polyaniline/α‐RuCl₃.xH₂O composites electrodes showed much higher specific capacitance, better power characteristics and were more promising for application in capacitor than pure polyaniline electrode. The effect and role of α‐RuCl₃.xH₂O in the composite electrode were also discussed in detail. POLYM. COMPOS., 34:2142–2147, 2013. © 2013 Society of Plastics Engineers     

Mechanical properties and densification behavior of β‐spodumene/anorthite composites

Although β‐spodumene/anorthite composites are interesting systems, little research work has been done to study their properties. This study aims at investigating the preparation and properties of β‐spodumene/anorthite composites containing β‐spodumene proportions ranging between 10 and 25 mass %. X‐ray diffraction analysis (XRD), Scanning electron microscopy (SEM), and the coefficient of thermal expansion (CTE) were used to characterize the effect of addition of β‐spodumene on the phase relations, microstructure, and thermal expansion behavior of resultant composites. The results show that the presence of β‐spodumene significantly reduces the porosity and reduces the densification temperature. It reduces thermal expansion and enhances the mechanical properties of anorthite‐containing composites.     

Preparation and characterization of γ‐irradiated crosslinked silicone rubber/organoattapulgite composites

Silicone rubber (SR)/organoattapulgite (OAT) composites were prepared with γ‐irradiation crosslinking at a dose range varied from 30 to 300 kGy. Natural fibrillar silicate attapulgite (AT) was modified by silane coupling agent, and the obtained OAT was used as reinforcing fillers in SR. The effect of irradiation doses on the degree of crosslinking of SR/OAT composites was determined by solvent swelling method. It was found that the molecular weight between crosslinks (M_c) reduced with the increase in irradiation doses. Moreover, the addition of OAT to SR matrix promoted an increase in the crosslinking density of the composites because of the presence of the active crosslinking sites of OAT. The mechanical properties of the SR/OAT composites including tensile strength, elongation at break, and Shore A hardness subjected to various irradiation doses were studied. The experimental results showed that the tensile strength, elongation at break, and Shore A hardness were all improved significantly in the presence of OAT, which indicated that OAT was an alternative reinforcing filler of SR. In addition, the effect of various irradiation doses on the mechanical properties of SR and SR/OAT composites was also investigated. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Preparation and properties of β‐phase graphene oxide/PVDF composite films

We report preparation of graphene oxide (GO) from expanded graphite (EG) via a modified Hummers method. GO/PVDF composites films were obtained using solvent N, N‐Dimethylformamide (DMF) and cosolvent comprising deionized water/DMF combination. X‐ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses revealed that the main crystal structure of the composite films is β‐phase, and use cosolvent method tends to favor the formation of β‐phase. Scanning electron microscopy (SEM) was used to investigate the microstructure of composite films. Storage modulus and loss modulus were measured by Dynamic mechanical analysis (DMA). Broadband dielectric spectrum tests showed an increase in the dielectric constant of the GO/PVDF composite films with the rising content of GO, and by cosolvent method could improve the dielectric constant while reducing the dielectric loss. Our method that uses GO as an additive and deionized water/DMF as the cosolvent provides a promising and low‐cost pathway to obtain high dielectric materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41577.     

Preparation of polyethylene oxide/LixV2‐δO4‐δ nanocomposites

Polyethylene oxide (PEO)/LixV_2‐δO_4‐δ nanocomposites were prepared in aqueous solution. Characterization of the nanocomposites using thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), powder X‐ray diffraction (XRD), and Fourier transform infrared spectrum (FTIR) shows that polymer chains intercalate inorganic host lamella and exhibit lattice expansion along the stacking direction of 4.2 Å. A possible model for the structure of the nanocomposite is also provided. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2162–2166, 2001     

The mechanical properties of β‐Si3N4 whiskers‐reinforced dental resin composites

The surface‐modified β‐Si₃N₄ whiskers were used as inorganic fillers to reinforce dental resin (Bis‐GMA/TEGDMA) matrix with filler level ranging from 0 to 60 wt %. The experimental results indicated that the fracture strength of the composites increased from 79.85 to 139.8 MPa with increasing the whiskers loading. The compressive strength, elastic modulus, and rockwell hardness all increased monotonously with increasing filler level. Furthermore, thermal cycling did not decrease the fracture strength of the composites. Moreover, the composites showed good biocompatibility to support MG63 cells adhesion and proliferation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40692.     

Preparation and properties of poly(ε‐caprolactone) self‐reinforced composites based on fibers/matrix structure

Self‐reinforced poly(ε‐caprolactone) (PCL) composites were prepared from bi‐component PCL yarns composed of PCL drawn fibers and PCL matrix by a combined process of yarns winding and hot‐pressing. Series of PCL polymers with different melting points were synthesized and used as matrix. PCL melt‐spun fibers were subject to different draw ratios and functioned as reinforcement. During the process of hot‐pressing, the matrix with low melting points melted and bonded the unmelted drawn fibers together creating self‐reinforced composites, the morphologies of which were examined by scanning electron microscope. Tensile testing of the composites was performed along the longitudinal and transverse directions separately. The longitudinal tensile test results showed that the Young's modulus and strength at break of the self‐reinforced composites were 59% and 250% higher than that of pure PCL. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44673.     

Ruthenium(II)‐Catalyzed Protocol for Preparation of Diverse α,β‐ and β,β‐Dihaloenones from Diazodicarbonyls

Efficient one‐step syntheses of α,β‐ and β,β‐dihaloenones were achieved by ruthenium(II)‐catalyzed reactions between cyclic or acyclic diazodicarbonyl compounds and oxalyl chloride or oxalyl bromide in moderate to good yields. This methodology offers several significant advantages, which include ease of handling, mild reaction conditions, one‐step reaction, and the use of an effective and non‐toxic catalyst. The synthesized compounds were further transformed into highly functionalized novel molecules bearing aromatic rings on the enone moiety using the Suzuki reaction.

     

Preparation and properties of polystyrene/SiCw/SiCp thermal conductivity composites

The silicon carbide whisker (SiCw) and silicon carbide particle (SiCp) were employed to prepare polystyrene/silicon carbide whisker/silicon carbide particle (PS/SiCw/SiCp) thermal conductivity composites, and the titanate coupling reagent of NDZ‐105 was introduced to functionalize the surface of fillers. The thermal conductive coefficient λ improved from 0.18 W/mK for native PS to 1.29 W/mK for the composites with 40% volume fraction of SiCw/SiCp (volume fraction, 3 : 1) hybrid fillers. Both the thermal decomposition temperature and dielectric constant of the composites increased with the addition of SiCw/SiCp hybrid fillers. At the same addition of SiCw/SiCp hybrid fillers, the surface modification of hybrid fillers by NDZ‐105 could improve the thermal conductivity and the mechanical properties of the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Interfacial and mechanical properties of γ‐Fe2O3/segmented polyurethane/poly(vinyl chloride) composites

Segmented polyurethane (SPU)/poly(vinyl chloride) (PVC) blends were particulated with γ‐Fe₂O₃. Interfacial properties of the composite were studied through the adsorption behaviors of SPU and PVC and their blends on γ‐Fe₂O₃ particles surface. Mechanical properties of the composite were measured with dynamic mechanical analysis and tensile test measurements. PVC with functional groups (FPVC), because of strong interactions, showed preferential adsorption on γ‐Fe₂O₃ compared with SPU and PVC. Moreover, the γ‐Fe₂O₃ particles were covered by FPVC in the γ‐Fe₂O₃/SPU/FPVC composite. The adsorption layer of FPVC protected SPU from catalytic degradation by γ‐Fe₂O₃, resulting in increasing hydrolytic stability for SPU. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3030–3035, 2001     

β‐Polypropylene/wood flour composites: Effects of specific β‐nucleation and coupling agent on mechanical behavior

Polypropylene/wood flour composites were prepared by melt compounding. To improve their mechanical performance, the matrix polypropylene was modified with a specific nucleation agent based on an amide of dicarboxylic acid, which promotes crystallization predominantly in the β‐phase. The resulting material was used as a matrix for composites containing 10%, 20%, and 30% of wood flour. Uniform dispersion of the filler and improved interfacial adhesion was ensured by compatibilization with a small amount of maleic anhydride‐grafted polypropylene. A beneficial effect of application of the nucleation agent together with a compatibilizer on the resulting mechanical behavior was shown. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 506–511, 2007     

Chemoenzymatic Preparation of Enantiopure Homoadamantyl β‐Amino Acid and β‐Lactam Derivatives

Racemic cis‐10‐azatetracyclo[7.2.0.1^2,6.1^4,8]tridecan‐11‐one was prepared from homoadamant‐4‐ene by chlorosulfonyl isocyanate addition. The transformation of the β‐lactam to the corresponding β‐amino ester followed by Candida antarctica lipase A‐catalyzed enantioselective (E>>200) N‐acylation with 2,2,2‐trifluoroethyl butanoate afforded methyl (1R,4R,5S,8S)‐5‐aminotricyclo[4.3.1.1^3,8]undecane‐4‐carboxylate and the (1S,4S,5R,8R)‐butanamide with>99% ee at 50% conversion. Alternatively, transformation of the β‐lactam to the corresponding N‐hydroxymethyl‐β‐lactam and the following Pseudomonas cepacia (currently Burkholderia cepacia) lipase‐catalyzed enantioseletive O‐acylation provided the (1S,4S,6R,9R)‐alcohol (ee=87%) and the corresponding (1R,4R,6S,9S)‐butanoate (ee>99%). In the latter method, competition for the enzyme between the (1R,4R,6S,9S)‐butanoate, 2,2,2‐trifluoroethyl butanoate and the hydrolysis product, butanoic acid, tended to stop the reaction at about 45% conversion and finally gave racemization in the (1S,4S,6R,9R)‐alcohol with time.     

Electrical and thermal properties of γ‐irradiated nitrile rubber/rice husk ash composites

The effects of both the rice husk ash (RHA) loading and fumed silica (FS) loading on the structure, thermal stability, and electrical properties of acrylonitrile–butadiene rubber (NBR) composites were studied. The filler loading were chosen to be 5 and 20 phr for RHA and 5 and 30 phr for silica. Also, the effect of the γ‐irradiation dose (25 kGy) on these parameters was investigated. The structure and thermal stability were studied with X‐ray diffraction and thermogravimetric analysis techniques. Furthermore, some electrical parameters, such as the direct‐current electrical conductivity (σ_dc), activation energy (E_a), dielectric constant (?′), and dielectric loss (?″), were determined. The incorporation of both RHA and FS resulted in improved thermal stability after γ irradiation at 25 kGy. The loading of FS on NBR was shown to decrease σ_dc, ?′, and ?″ and increase E_a. On the other hand, the loading of RHA showed the opposite trend. Finally, γ irradiation of NBR composites filled with both fillers decreased the values of σ_dc, ?′, and ?″ for all the samples, which followed the trend for the unirradiated composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and sorption properties of tunable polyester copolymers containing β‐cyclodextrin

Polyester copolymers were prepared with β‐cyclodextrin (β‐CD) and sebacoyl (SCl) or terephthaloyl (TCl) chloride cross linker agents using a simple, one‐pot synthesis. Variation of the mole ratios (i.e., 1 : 1, 1 : 2, 1 : 3, 1 : 6, and 1 : 9) of β‐CD to diacid chloride linker units resulted in copolymers with differing solubility and chemical stability in aqueous solution. The sorption properties of copolymers such as 1 : 6 and 1 : 9 SCl, and 1 : 9 TCl materials were investigated because of their relative insolubility and resistance to hydrolysis at pH 4.6. The monolayer sorption capacity (Q_m) of the copolymers varied according to the nature of the cross linker and the relative mole ratio of monomers. Q_m values obtained from the Sips isotherm model range from 2.7 to 5.2 mmol/g for the sorption of p‐nitrophenol at 295 K and approach the value of Q_m for a commercially available granular activated carbon sorbent. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and sorption studies of β‐cyclodextrin/epichlorohydrin copolymers

β‐Cyclodextrin (β‐CD) copolymer materials were synthesized by reacting different mole ratios (1 : 15, 1 : 25 and 1 : 35) of β‐CD with epichlorohydrin (EP). The products were characterized using N₂ porosimetry, Fourier Transform Infrared spectroscopy, ¹³C CP‐MAS NMR spectroscopy, thermogravimetry analysis, elemental (C and H) analysis, and scanning electron microscopy. The sorption properties in aqueous solution were studied using p‐nitrophenol (PNP) with UV–Vis spectrophotometry. Sorption isotherms were obtained at pH 4.6 and three temperatures (22, 35, and 45°C) and at pH 10.3 at 22°C. The isotherms were analyzed using the BET isotherm model and the sorption parameters provided estimates of the surface area, sorption capacity, and isosteric heats of sorption for each polymeric material. The estimated surface areas are as follows: 58.2, 52.1, and 90.1 m²/g at pH 4.6. At pH 10.3, the estimated surface areas are 44.2, 40.5, and 58.5 m²/g, respectively. The removal efficiency of PNP by the polymeric materials ranged between 4.5 and 58% for the conditions investigated whereas the isosteric heats ranged between ?24.5 and ?13.6 kJ/mol. Removal efficiencies were concluded to strongly depend on the sorption conditions such as pH, temperature, and the relative amounts of sorbent and dye in aqueous solution. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

On mechanical properties of sago starch/poly(ε‐caprolactone) composites

Four types of sago starch were incorporated into a poly(ε‐caprolactone) (PCL) matrix, native, predried, thermoplastic starch (TPS) granules and TPS. All systems were found to be phase‐separated. Tensile properties were obtained after formulation of various mixtures and processing of suitable test specimens. It was found that elongation at break of composites comprising native starch and thermoplastic starch decreases almost linearly with volume fraction of starch whereas tendencies to nonlinear dependencies were observed for predried and thermoplastic starch granules. Except for composites containing native starch, tensile strength was found to decrease linearly with volume fraction of starch. However, statistical analysis of the corresponding regression coefficients shows that the coefficients ruling the compostion dependence of tensile properties are not significantly different for the four starch types. One may conclude that in all cases, tensile properties decrease almost linearly with volume fraction and maximum volume fraction of starch loading is around 0.6. Scanning electron micrographs of fracture surfaces revealed weak interfacial adhesion between sago starch and the polymer matrix.     

Fabrication and properties of surface‐modified β‐Si3N4 whiskers reinforced dental resin composites

In this article, three kinds of surface‐modified methods were used to treat β‐Si₃N₄ whiskers before being incorporated into Bis‐GMA/TEGDMA dental resin matrix in order to improve the whiskers' reinforcing effect. The experimental results showed that composites with directly heat‐treated and then silanized β‐Si₃N₄ whiskers had the best reinforcing effect. They had flexural strength of 160 ± 7.0 MPa (mean ± SD; n = 6), compressive strength of 371 ± 1.4 MPa (mean ± SD; n = 5) and HRA of 48.4 ± 0.5(mean ± SD; n = 5), respectively. In addition, water sorption and solubility test demonstrated that the composites were reliable to use as the dental restoration materials. Therefore, the directly heat‐treated and then silanized β‐Si₃N₄ whiskers (better than β‐Si₃N₄ whiskers mixed with SiO₂ nanoparticles or SiO₂ sols) were most suitable fillers to reinforce dental resin composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Structural elucidation and iron oxidation states in situ formed β‐Ca3(PO4)2/α‐Fe2O3 composites

A detailed structural analysis on the in situ synthesized β‐Ca₃(PO₄)₂/α‐Fe₂O₃ composites is demonstrated. Compositional ratios, the influence and occupancy of iron at the β‐Ca₃(PO₄)₂ lattice, oxidation state of iron in the composites are derived from analytical techniques involving XRD, FT‐IR, Raman, refinement of the powder X‐ray diffraction and X‐ray photoelectron spectroscopy. Iron exists in the Fe³⁺ state throughout the investigated systems and favors its occupancy at the Ca²⁺(5) site of β‐Ca₃(PO₄)₂ until critical limit, and thereafter crystallizes as α‐Fe₂O₃ at ambient conditions. Fe³⁺ occupancy at the β‐Ca₃(PO₄)₂ lattice yields a Ca₉Fe(PO₄)₇ structure that is isostructural with its counterpart. A strong rise in the soft ferromagnetic behavior of β‐Ca₃(PO₄)₂/α‐Fe₂O₃ composites is obvious that depends on the content of α‐Fe₂O₃ in the composites. Overall, the diverse level of iron inclusions at the calcium phosphate system with a Ca/P ratio of 1.5 yields a structurally stable β‐Ca₃(PO₄)₂/α‐Fe₂O₃ composites with assorted compositional ratios.     

Investigation on β‐polypropylene/PP‐g‐MAH/ surface‐treated calcium carbonate composites

β‐Polypropylene composites containing calcium carbonate treated by titanate coupling agent (T‐CaCO₃) and maleic anhydride grafted PP (PP‐g‐MAH) were prepared by melt compounding. The crystallization, morphology and mechanical properties of the composites were investigated by means of differential scanning calorimetry, wide‐angle X‐ray diffraction, polarized light microscopy, scanning electron microscopy and mechanical tests. It is found that both T‐CaCO₃ and NT‐C are able to induce the formation of β‐phase, and NT‐C greatly increases the β content and decreases the spherulitic size of PP. PP‐g‐MAH facilitates the formation of β‐form PP and improves the compatibility between T‐CaCO₃ and PP. Izod notched impact strength of β‐PP/T‐CaCO₃ composite is higher than that of PP/T‐CaCO₃ composite, indicating the synergistic toughening effect of T‐CaCO₃ and β‐PP. Incorporation of PP‐g‐MAH into β‐PP/T‐CaCO₃ composite further increases the content of β‐crystal PP and improves the impact strength and tensile strength when T‐CaCO₃ concentration is below 5 wt%. The nonisothermal crystallization kinetics of β‐PP composites is well described by Jeziorny's and Mo's methods. It is found that NT‐C and T‐CaCO₃ accelerate the crystallization rate of PP but the influence of PP‐g‐MAH on crystallization rate of β‐PP composite is marginal. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers