Glass fiber-reinforced epoxy composites

Glass fiber-reinforced epoxy composites were prepared from the matrix resins tetraglycidyl diaminodiphenylmethane

1 Systematic name: N,N,N′,N′-Tetrakis(2,3-epoxypropyl)-4,4′-diaminodiphenylmethane.

(TGDDM) and tetraglycidyl bis(o-toluidino)-methane

2 Systematic name: N,N,N′,N′-Tetrakis(2,3-epoxypropyl)-4,4′-bis(o-toluidino)methane.

(TGMBT) using various amines like 4,4′-diaminodiphenylmethane (DDM), 4,4′-diaminodiphenylsulfone (DDS) and diethylene triamine (DETA) as curing agents. The fabricated laminates were evaluated for their mechanical and dielectrical properties and chemical resistance. The composites prepared using an epoxy fortifier (20 phr) showed significant improvement in the mechanical properties.     

The hierarchical structure and flexure behavior of woven carbon fiber epoxy composite

The hierarchical structure and flexure behavior of woven carbon fibers epoxy composite were investigated in this work. First, the hierarchical structure of the composite is characterized on three levels: composite, ply, and yarn. Structura imperfections,

1 In this paper, “structural imperfections” is used to describe the inherent structural characteristics of the actual composite, which deviate from the theoretically ideal and perfect composites, control, that are used in composite theories.

such as, ply‐ply misalignment, ply‐ply offset, and resin pockets, are identified and described. Second, a four‐point bending arrangement is used to study the flexure properties of the composite. Additionally, in‐situ traveling microscope and acoustic emission (AE) techniques are utilized to gain insight to the failure proceses during flexure test. AE showed early stages of matrix cracking before visual observation, which makes it a valuable tool for early failure detection.     

Investigation of primers reducing the pink-ring formation in multilayer printed circuit boards

A rapid and easy screening test was applied to assess the capability of various formulated primers to reduce the defect of pink rings in multilayer printed circuit boards. The mixtures of silanes with multifunctional silanol groups (crosslinkers) and 3-glycidoxypropyl-trimethoxysilane

1 Systematic name: 3-(2,3-Epoxypropoxy)propyl-trimethoxysilane.

(referred to as silane C) or N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane

2 Systematic name: 3-[N-2-aminoethyl]aminopropyl-trimethoxysilane.

(silane B) were proved to be effective in reducing the pink rings. The performance of the mixed silanes using silane A and crosslinkers with aromatic groups were better than other formulated primers which was partly attributed to less amounts of hydrophilic groups and better integrity in the primer films. A developed primer consisting of siloxane compounds had the best performance. The online test confirmed the results from the screening test and demonstrated the feasibility of the designed screening test in assessing the performance of primers. The results of FTIR spectroscopy and thermogravimetric analyses confirmed that the effective primers coated on the copper oxides could improve the curing reaction and the thermal oxidative stability of the epoxy/CuO system.     

Oxidative aging of thermoplastic polyimide films

Two linear polyimides were subjected to accelerated isothermal aging at temperatures between 300 and 400°C. Losses in toughness correlated well with changes in glass transition temperature (T_g) of the films, but not with weight loss. Both materials have extrapolated lifetimes of 100,000 h near their T_g's. © 1995 John Wiley & Sons, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Functional polyamides. 3. Synthesis and chelating properties of a new poly(amide thioether)

Polymerization of β,β′-(ethylenedithio)dipropionitrile

1 IUPAC name: 4,7-dithiadecane dinitrile.

with formaldehyde in the presence of sulfuric acid was carried out in order to permit the synthesis of polymides containing thioether groups. The obtained poly(amide thioether)s were characterized; they coordinate mercury (II) with a high degree of selectivity.     

Mowrah (Madhuca latifolia) seed saponin. Toxicological studies

Mowrah seed (Madhuca latifolia) meal

1 Meal refers to solvent extracted material.

contains high levels of saponin (7%) making it unsuitable for incorporation in animal feedstuff formulations. The saponin from mowrah seed meal was isolated and purified by paper chromatography. This was used for in vitro tests as well as pharmacological and acute toxicity studies for a better understanding of its properties and toxicity. The oral, intraperitoneal and intravenous LD₅₀ of mowrah saponins in mice are 1 g, 15–20 mg and 15 mg/kg body weight respectively. Processing of the meal to remove or inactivate the saponin will be essential prior to its incorporation in animal feeds.     

The STOBBE Condensation with Pyrrolyl Aldehydes – a synthesis of indole derivatives

The condensation of pyrrolyl-2-aldehyde or 1-methyl-pyrrolyl-2-aldehyde with dimethyl succinate, using sodium hydride as condensing agent, gave predominantly the halfesters 1a and 1c respectively. Their structure and (E)-configuration

1 i. e., pyrrol ring and COOCH₃ group are in trans position. This nomenclature follows the IUPAC 1968 Tentative Rules, Section E, Fundamental Stereochemistry, J. org. Chemistry 35 , 2849 (1970).

were confirmed by their cyclisation to the corresponding indole derivatives 2a–h .     

Properties of standard materials for reflection

This article gives a short survey of some literature on the calibration, suitability, properties, and use of various materials which are used as standards of reflectance. The classical ultimate reference standard, smoked magnesium oxide, is discussed briefly, and information is given on the properties of materials presently used: BaSO₄, Russian opal glasses, ceramic tiles, and Halon.

1 Halon is a registered trade name of the Allied Chemical Corporation.

The suitability of these materials for use as transfer standards or working standards is discussed.     

Synthesis of phosphorus-containing polymers with potential bioactivity

Phosphorylation of poly(N-vinyl pyrrolidone-co-vinyl amine) and poly(N-vinyl pyrrolidone-co-glycidylcrotonate

1 Systematic name: (2,3-Epoxypropyl)crotonate.

) is realized by Atherton-Todd and Fields-Kabachnik reactions and by the means of direct interaction with phosphorus trichloride and phosphorus trichloride oxide. The composition and structure of the isolated final products was proved by NMR (¹H and ³¹P), IR spectroscopy and elemental analysis.     

Porous bead aliphatic-aromatic methacrylate copolymers,I. Effect of polymerization conditions on porous structure formation of methyl methacrylate — di(methacryloyloxymethyl)naphthalene copolymers

The influence of inert porogenic mixture and monomer mixture composition and concentration on specific surface areas, pore size distribution, volumes of pores capable of capillary condensation of nitrogen and true density of copolymers were investigated for a new type of methacrylate monomer system: methyl methacrylate and di(methacryloyloxymethyl)naphthalene. The obtained copolymers exhibit similar character as it is typical for PPS

1 PPS = Porous by Precipitant and Solvent.

styrene-divinylbenzene resins.     

Stevensanaloge,Durch Nickelkomplexe Katalysierte Umlagerung Von Triarylphosphoryliden Und Darstellung Sowie Strukturbestimmung Von Phosphorylid-Nickeltricarbonylkomplexen

The Stevens rearrangement of the triarylphosphorusylids R₃ P=CHR′ (III) (R′ = H, CH₃, C₂ H₅) to diarylbenzylphosphines (V) is catalyzed by nickel complexes (e.g., (COD)₂ Ni (I)). Attempts to prepare trimesitylphosphine-methylene result in direct formation of dimesityl (mesitylmethyl) phosphine (XII) — the first recorded direct Stevens rearrangement of a phosphorusylid. Phosphorusylids react with nickeltetracarbonyl without rearrangement to give complexes of the type R₃P=CH_a · Ni(CO)₃ (XIV). The structure of XIV has been established by the IR and NMR spectra and confirmed by an X-ray structural determination.

1 B. L. Barnett and C. Krüger, J. Cryst. Mol. Struct., im Druck.

The ylid is bonded to the nickel through the C-atom with resulting hybridization from sp² towards sp³.     

Simultaneous fluorine elimination and alkylation of poly(tetrafluoroethylene)

PTFE (powder or foils) was defluorinated and derivatized in a one-step process by alkyl- and aryllithium in the presence of tetramethylethylenediamine

1 Systematic name: 1,2-Bis-[dimethylamino]ethane.

(TMEDA) as a catalyst. As evidenced by infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and elemental analysis the C₄H₉-, C₈H₁₇-, C₁₂H₂₅- or phenyl groups were attached to a partly defluorinated macromolecular chain. Analogous reactions with dilithioaryl or dilithioalkyl agents presumably lead to crosslinking of the polymeric chains through alkyl or aryl groups. When the PTFE powder is treated with more concentrated RLi (>3 mol L^?1) at temperatures >150°C, the defluorination is almost quantitative even in the absence of the catalyst. The TMEDA-catalyzed reaction proceeds via elimination and nucleophilic addition. On the other hand, more concentrated RLi in the absence of the catalyst seems to react via a radical mechanism.     

Synthesis of phosphorus-containing wofatit cation exchangers and their affinity toward selected cations

A number of solid Cationits have been prepared derived from Wofatit

1 Trademark, VEB Chemiekombinat Bitterfield.

gel and canal structures: styrene/DVB, chloromethylated ST/DVB, and acrylic acid/DVB copolymers. To functionalize the copolymers, PCl₃/AlCl₃ and dialkyl phosphites or trialkyl phosphites were used. The influence of the polymer matrix structure and the chemical structure of the functional groups of obtained Ionits on their affinity toward 23 metallic cations in acidic media has been investigated using the conductivity method. To obtain comparison data, commercial “Wofatit”–sulfonic and–carboxylic Cationits, have been tested under identical conditions.     

Photochemical and thermal stability of amaranth (FD&C red no. 2) in aqueous media

The decomposition of the formerly

1 This dye was delisted by the U. S. Food and Drug Administration in 1976, and has not been legally used in the U. S. in foods, drugs, or cosmetics since that date.

used food and pharmaceutical dye amaranth (FD&C Red No. 2) in water was studied under a variety of conditions. A matter of some concern is that one of the decomposition products is α-naphthylamine, a known carcinogen.     

Dicyclopentadienoxidation. II 5. Katalysierte Flüssigphasenoxidation von Dicyclopentadien

Dicyclopentadiene Oxidation. II. Catalyzed Liquid-Phase Oxidation of Dicyclopentadiene The liquid-phase oxidation of dicyclopentadiene 1 by molecular oxygen was studied in the presence of MoO₂(acac)₂

1 Acac- Acetylacetonat

as a typical epoxidation catalyst. The yield of the mono-epoxides 2 and 3 is increased to 56,4% (uncatalyzed reaction: 43,6%). The ratio of the two mono-epoxides is decreased to 2/3 = 2,6 in relation to the uncatalyzed reaction ( 2/3 = 7,1). The influence of temperature, conversion and solvents is described. The bisepoxide 4 is formed at lower conversions than in the uncatalyzed reaction. But also at higher conversions of 1 not more than 10% of the bisepoxide 4 is formed     

Physical aging in thermosets of differing degrees of cure—master curve generation and the relation to mechanical properties

Physical aging of a thermoset system based on bisphenol-A epoxy (DER

1 Trademark of The Dow Chemical Company.

383) and tetrabromobisphenol-A cured with sulfanilamide and diaminodiphenylsulfone was studied as a function of cure history. Changes in the dynamic mechanical spectra for the thermoset system were correlated to changes in relative toughness associated with physical aging as determined by plane-strain biaxial tension-compression yield measurements. It was found that master curves, generated by using tan δ data obtained in the β relaxation temperature regime, are well related to the corresponding changes in mechanical properties and, hence, have predictive value. Relative toughness decreases and compressive yield increases with decreasing tan 5 because of decreased molecular segmental mobility. The relative extent of physical aging for the as-cast thermosets was shown to be linearly related to the cure time.     

The STOBBE Condensation with Dimethyl Homophthalate. Part I

The condensation of methyl 2-thienyl, methyl 2-furyl, and phenyl 2-thienyl ketone with dimethyl homophthalate in the presence of either potassium t-butoxide or sodium hydride as condensing agent, gave predominantly the (z)-half esters

1 The nomenclature of cis/trans isomers follows the IUPAC Tentative rules, Section E, Fundamental Stereochemistry, J. org. Chemistry 35 , 2849 (1970). See also N. R. El-Rayyes, J. prakt. Chem. 315 (2), 300 (1973). (E) = trans-(Heterocyclic ring/CO₂CH₃) (Z) = cis-(Heterocyclic ring/CO₂CH₃)

. The structure and configuration of the products were inferred by chemical and spectroscopic means.     

Thermal analysis of poly(phenylene sulfide) polymers. I: Thermal characterization of PPS polymers of different molecular weights

Thermal properties of Fortron®

1 ®Registered trademark of Hoechst Celanese Corporation.

poly(phenylene sulfide) (PPS) polymers of different molecular weights were studied by DSC. Crystallization studies revealed that the ability of these polymers to crystallize decreases with increasing molecular weight. The Avrami equation poorly describes the isothermal crystallization of PPS. Lamellar crystallization was observed for the lowest molecular weight sample. For the other, higher molecular weight polymers the Avrami exponent is always between 2 and 3, suggesting development of distorted spherulites with heterogeneous nucleation. The temperature dependence of the solid and melt heat capacities have been determined. The solid specific heat capacity did not exhibit a molecular weight dependence. The heat capacity increase at the glass transition, T_g, has been calculated to be 28.1 J°C^?1 mole^?1. The equilibrium melting point of PPS has been estimated to be 348.5°C using the Hoffman–Weeks method. The T_g of PPS increases with molecular weight. The T_g of the highest molecular weight evaluated is 92.5°C. A DMA relaxation peak corresponding to the onset of the phenylene ring rotation occurs at ?92°C. Only the highest molecular weight could be quenched to a completely amorphous state.     

Dicyclopentadienoxidation. I,Unkatalysierte Flüssigphasenoxidation von Dicyclopentadien

Dicyclopentadiene Oxidation I. Uncatalyzed Liquid-Phase Oxidation of Dicyclopentadiene Dicyclopentadiene is oxidized by molecular oxygen to a mixture of the monoepoxides 2 and 3 . The identification of the epoxides 2 , 3 and 4 was executed with authentic samples prepared by epoxidation with peracetic acid or with tert-butylhydroperoxide in the presence of MoO₂(acac)₂

1 acac — Acetylacetonat

The main product is the substituted norbornene oxide 2 . Allylic oxidation is also observed. Remarkable amounts of hydroperoxides can be determined iodometrically. The formation of allylic oxidation products 7 , 8 , 9 and 10 was proved by GC-MS-analysis. It is shown that in the uncatalyzed liquid phase oxidation of dicyclopentadiene no more than 50% of epoxides are formed. The bisepoxide 4 was found in small amounts only at higher conversions of the dicyclopentadiene.     

Styrene emulsion polymerization in the presence of a maleate-functional surfactant

Dodecylhemiester of maleic anhydride is a very good anionic stabilizer for the emulsion polymerization of styrene. Rather high solid contents may be produced. Up to about 70% of the surfactant can be grafted onto the surface of the particles. Upon floculation with calcium salt, only 3% of the surfactant is left in the washing water. © 1997 John Wiley & Sons, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

J Appl Polym Sci 65: 2289–2296, 1997