Morphology of modified hydrolysis lignin

The morphology of hydrolysis lignin was studied. The effect of dimethyl sulfoxide, temperature, and activating additives on the surface characteristics of lignin was examined.     

Synthesis of phosphorus-based flame retardant systems and their use in an epoxy resin

Methods are proposed to synthesize efficient organophosphorous compounds and combine them with montmorillonite nanoparticles. The chemical-physical structure and mechanism of action of the new systems were studied in epoxy resin. Best results were achieved using the fully phosphorylated calixresorcinarene derivative: the heat release rate peak could be decreased by 61% and the LOI value was increased from 21 to 28. The salt form of additives in case of phosphorylated phloroglucine derivatives was not advantageous in epoxy resin, because the additives could not participate in the crosslinking process effectively due to their inhomogenous distribution in the matrix. The incorporation of the nanoparticles did not create the desired flame retardant effect which can be explained by the increased heat conductivity and lower mobility of the nanoparticles due to the crosslinked structure.     

Enhanced hydrolysis resistance of biodegradable polymers and bio-composites

This study investigated the hydrolysis of biodegradable polymers and bio-composites at 50 °C and 90% relative humidity (RH). With increasing hydrolysis time, the mechanical properties of the biodegradable polymers and bio-composites significantly decreased due to the easy hydrolytic degradation of the ester linkage of the biodegradable polymers. With increasing hydrolysis time, the tensile strength of the polybutylene succinate (PBS) treated with anti-hydrolysis agent or with trimethylolpropane triacrylate (TMPTA) significantly increased compared to the non-treated PBS. The same results were observed for the PBS-based bio-composites. This result was confirmed by the Fourier transform infrared-attenuated total reflectance (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS) spectra, which exhibited a less eroded surface, small cracks and fewer holes due to the reduced surface hydrolysis and erosion under high humidity condition.     

Preparation of 3‐aminopropyltriethoxy silane modified cellulose microcrystalline and their applications as flame retardant and reinforcing agents in epoxy resin

Cellulose microcrystalline (CMC), a linear polysaccharide with glucosidic bond, was successfully extracted from bamboo powder and modified by 3‐aminopropyltriethoxy silane coupling agent (KH550) to prepare KH550‐CMC. The prepared KH550‐CMC, in association with ammonium polyphosphate (APP), was introduced into epoxy resin (EP) by casting process to obtain flame retardant composites. The fire performance evaluation indicated that the presence of 10‐phr APP and 5‐phr KH550‐CMC in EP achieved the maximal LOI value of 28.9%, passed the UL‐94 V‐0 rating, and significantly decreased the peak heat release rate from 1055 kW/m² of neat EP to 286 kW/m². The improved fire performance is due to the improvement of dispersity of CMC in EP matrix and formation of better char layer, thus protecting the matrix effectively. Moreover, the introduction of KH550‐CMC could also partly eliminate the negative influence of flame retardants on the mechanical properties of EP composites due to the strengthening effect of CMC and better interfacial compatibility after modification with KH550.     

Physical aging of epoxy polymers and their composites

Exposure to extended periods of sub‐T_g temperatures causes physical changes in the molecular structure of epoxy resins and epoxy‐based materials to occur. These physical aging mechanisms include the reduction in free volume and changes to the molecular configuration. As a result, mechanical, thermodynamical, and physical properties are affected in ways that can compromise the reliability of epoxy‐based engineering components and structures. In this review, the physical changes in the molecular structure of epoxies are described, and the influence of these changes on the bulk‐level response is detailed. Specifically, the influence of physical aging on the quasistatic mechanical properties, viscoelasticity, fracture toughness, thermal expansion coefficient, volume relaxation, enthalpy relaxation, endothermic peak temperature, fictive temperature, and moisture/solvent absorption capability is reviewed. Also discussed are relationships between relaxation functions, crosslink density, composite reinforcement, and epoxy/copolymer blending and the physical aging response of epoxies. Finally, the concepts of thermal and mechanical rejuvenation are discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Preparation and characterization of organotin-oxomolybdate coordination polymers and their use in sulfoxidation catalysis

The organotin-oxomolybdates [(R(3)Sn)(2)MoO(4)].n H(2)O (R=methyl, n-butyl, cyclohexyl, phenyl, benzyl) have been prepared and tested as catalysts for the oxidation of benzothiophene with aqueous hydrogen peroxide, at 35 degrees C and atmospheric pressure. In all cases, the 1,1-dioxide was the only observed product. The kinetic profiles depend on the nature of the tin-bound R group and also on the addition of a co-solvent. For the tribenzyltin derivative, the apparent activation energies for sulfoxidation as a function of the co-solvent are in the order 1,2-dichloroethane (5 kcal mol(-1))相似文献   

Preparation of graphene oxide modified glass fibers and their application in flame retardant polyamide 6

In order to improve the flame retardancy of glass fibers (GFs) reinforced polyamide 6 (PA6) composites and eliminate the “wicking effect,” the preparation and application of graphene oxide (GO) modified GFs were investigated in this work. Flame retardant PA6 was prepared by blending graphene oxide modified GFs reinforced PA6 and aluminum diethyl phosphonate. For the GFs reinforced PA6, the limiting oxygen index of the composite increased from 20.6% to 22.3%, and peak heat release rate decreased by 37.2% in cone calorimeter test via introducing graphene oxide onto the surface of GFs. Comparing PA6/GF30/ADP15 and PA6/GF‐GO30/ADP15, LOI of the later increased to 31.2%, the vertical burning test (UL‐94) reached V‐0, and the peak heat release rate decreased by 18.0%. The interface compatibility was greatly improved after the introduction of GO. The sheet structure of the GO on the GFs surface could block the combustible gas spillage and the flow of melt along the GFs, thus significantly attenuating the “wicking effect” and improving the flame retardancy of composites.     

Facile synthesis of bio-based phosphorus-containing epoxy resins with excellent flame resistance

The development of high-performance biomass-derived epoxy thermosets with excellent flame resistance is vital to various applications (i.e., composites, coatings and adhesives). Herein, a difunctional epoxy monomer bis(2-methoxy-4-(oxiran-2-ylmethyl)phenyl) phenyl phosphate (BEU-EP) was synthesized from abundant and biobased eugenol. In addition, BEU-EP was cured by 4,4′-diaminodiphenyl methane (DDM) and the cured resin diglycidyl ether of bisphenol A (DGEBA)/DDM was used as a reference. Results indicated that BEU-EP/DDM not only showed a 58.1%, 28.8% and 35.1% increase in residual char (at 700 °C), flexural and storage modulus (at 30 °C) compared with DGEBA/DDM, but also exhibited excellent flame resistance and smoke suppression. BEU-EP/DDM passed V-0 rating (in UL-94 testing) with limiting oxygen index (LOI) of 38.4% and greatly decreased the peak heat release rate (pHRR) and total smoke production (TSP) by 84.9% and 80.5%, respectively. The mechanism analysis confirmed that the phosphorus-containing group and aromatic structure from BEU-EP contributed both the gas and condensed-phase flame retardation of BEU-EP/DDM network. This work provides an efficient and scalable route for synthesizing biobased epoxy thermosets with high integrated performance and superior flame resistance.     

Polyphosphazene microspheres modified with transition metal hydroxystannate for enhancing the flame retardancy of polyethylene terephthalate

A novel PZS@CS hybrid structure was synthesized for enhancing the flame retardancy of polyethylene terephthalate (PET). The PZS@CS hybrids showed significant flame retardance. For example, the incorporation of 6 wt% PZS@CS obviously brought about an 8.8% increase of limiting oxygen index value (29.3%) and passed the vertical burning test UL‐94 V‐0 level, accompanied with the sharp reduction of heat and smoke release. The flame retardant mechanism of PZS@CS hybrids was fully studied by the Thermogravimetric Analysis (TGA), pyrolysis‐gas chromatography‐mass spectrometry, and Raman methods, and the results showed that the improvement of flame retardancy was mainly ascribed to the synergistic effect of PZS and CS phases in both the condensed and the gas phase. Rheological results showed that PZS@CS hybrids improved the melt complex viscosity of PET composites and the well compatibility of PET matrix and PZS@CS hybrids was also proved by the improvement of mechanical properties.     

A novel ceramifiable epoxy composite with enhanced fire resistance and flame retardance

Journal of Thermal Analysis and Calorimetry - A novel epoxy composite with flame retardance and fire resistance was prepared by adding silicate glass frit (SGF) and ammonium polyphosphate (APP)...     

六苯氧基环三磷腈的热解及其对环氧树脂的阻燃机理

采用极限氧指数仪和锥形量热仪测试了以六苯氧基环三磷腈(HPCP)阻燃环氧树脂的燃烧性能,结果显示,与纯环氧树脂相比,阻燃环氧树脂的极限氧指数值(LOI)明显提高、热释放速率峰值(pk-HRR)和总热释放量(THR)明显下降、环氧树脂的点燃时间提前以及分解速度加快.采用热失重(TGA)、热重红外联用(TGA-FTIR)、X射线光电子能谱(XPS)和热裂解气相色谱质谱联用(Py-GC/MS)研究了HPCP及其阻燃环氧树脂的热解路线和阻燃机理.结果表明,在阻燃环氧树脂过程中,一方面,HPCP分子中的苯氧基团首先解离并发生歧化反应,由此产生的苯氧基及其歧化产物的焠灭效应在环氧树脂中发挥气相阻燃作用,剩余的磷腈环和苯环基团会进一步裂解产生小分子碎片;另一方面,环氧树脂基体在HPCP的作用下提前分解,产生了基于双酚A结构的大分子碎片并在HPCP裂解产物作用下加速炭化,从而使更多的基体组分以残炭的形式被固定在凝聚相中,提高了阻燃环氧树脂的残炭产率,发挥了凝聚相阻燃作用.     

Preparation, thermal properties and flame retardancy of phosphorus- and silicon-containing epoxy resins

Phosphorus- and silicon-containing epoxy resins were prepared from (2,5-dihydroxyphenyl)diphenyl phosphine oxide (Gly-HPO), diglycidyloxy methylphenyl silane (DGMPS) and 1,4-bis(glycidyloxydimethyl silyl)-benzene (BGDMSB) as epoxy monomers and diaminodiphenylmethane (DDM), bis(3-aminophenyl)methyl phosphine oxide (BAMPO) and bis(4-aminophenoxy)dimethyl silane (APDS) as curing agents. Epoxy resins with different phosphorus and silicon content were obtained. Their thermal, dynamic mechanical and flame retardant properties were evaluated. The high LOI values confirmed that epoxy resins containing hetero-atoms are effective flame retardants, but a synergistic efficiency of phosphorus and silicon on flame retardation was not observed.     

Preparation,flame retardancy,and thermal degradation of epoxy thermosets modified with phosphorous/nitrogen‐containing glycidyl derivative

Phosphorus/nitrogen‐containing advanced epoxy resins were obtained by chain‐extension of the diglycidyl ether of bisphenol‐A epoxy (DGEBA) resin with phosphorus‐modified triglycidyl isocyanurate (TGICP). The structure of TGICP was characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). Differential scanning calorimetry revealed that the EP/TGICP composites possessed higher glass transition temperatures than that of phosphorus free EP. The thermal stability and flame retardant properties of the epoxy resin/TGICP systems were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), and vertical burning test (UL‐94) test. When the TGICP content was 10 wt%, the LOI value of epoxy resin system was as high as 35.0% and it can obtain the V‐0 grade in UL‐94 protocol. From microscale combustion calorimetry (MCC) measurement, it was found that the addition of TGICP reduced the value of peak heat release rate and total heat release. The thermal degradation process of EP and EP/TGICP composite was monitored by real time FTIR. Moreover, scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS) were used to explore the morphology and chemical components of the char residues. Copyright © 2010 John Wiley & Sons, Ltd.     

Functional composition and IR spectra of cottonseed husk hydrolysis lignin and its derivatives

The functional compositions of cottonseed husk hydrolysis lignin and its derivatives have been determined and their IR spectra have been studied. A possible formation of stronger hydrogen bonds in derivatives of hydrolysis lignin has been shown.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 40 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 392–397, May–June, 1999.     

Suitable for immobilization ferromagnetic silica modified by carbonized lignin and carbodiimide: Preparation and properties

The composition of native aluminosilicate used to prepare, by means of chemical modification, a functionalized ferromagnetic organosilicon sorbent suitable for immobilizing biologically active substances was studied.     

Synthesis of three novel phosphorus-containing flame retardants and their application in epoxy resins

One symmetric diamine (4) and two symmetric phenols (5) and (6) were synthesized as phosphorus-containing flame retardants. The synthesis comprised a two-step procedure: the condensation of p-phenylenediamine with benzaldehyde, 4-hydroxybenzaldehyde and 2-hydroxybenzaldehyde respectively, followed by the addition of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to the imine linkage. The structures of (4)-(6) were characterized by FTIR, NMR and mass spectra. (4)-(6) served as co-curing agents of diaminodiphenylmethane for epoxy resins, and epoxy thermosets exhibited excellent flame retardancy, moderate changes in glass transition temperature (T_g) and thermal stability. When the phosphorus content reached 1.0 wt.%, the epoxy resin system met the UL-94 V-0 classification and the limiting oxygen index (LOI) reached more than 35.6, probably because of the nitrogen-phosphorus synergistic effect.     

联苯并环丁烯的制备及其聚合物的热稳定性

苯并环丁烯树脂具有优异的综合性能,可作为微电子器件中的高性能介电薄膜材料。其优异的性能满足大规模集成电路(MCM)、微电机系统(MEMS)、液晶显示器等器件的苛刻性能要求,在微电子领域有着极为重要的应用且前景广阔[1,2,3]。苯并环丁烯单体的种类较多,其聚合物大多具有优异的     

Preparation of reference materials for the determination of RoHS-relevant flame retardants in styrenic polymers

Reference materials for the analysis of polybrominated diphenyl ethers, polybrominated biphenyls and other common brominated flame retardants (FR) in styrenic polymers were prepared to suit the demands of actual restriction of the use of certain hazardous substances in electrical and electronic equipment analytics. Three methods of preparation were employed, viz. pellet forming, dissolution/vaporisation and extrusion, whereby extrusion proved to be the most suitable method. For extrusion, three procedures of pre-mixing were investigated: the polymers were either mixed with FR powder, FR solutions or FR concentrates that were taken from waste industrial polymers. The latter procedure proved to be most appropriate in terms of analyte concentration, predictability and recovery. The homogeneity of the samples, as well as the chemical and thermal long-term stabilities, was investigated. The result was an optimised method to prepare a suitable reference material for laboratory use. Figure   Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.