Temperature gradients in the channels of a single‐screw extruder

We used a temperature‐sensitive fluorescent dye, perylene, to monitor the true resin temperature during extrusion of polycarbonate. The measurement involved doping polycarbonate with perylene and detecting fluorescence with an optical sensor that accesses a standard instrumentation port on a barrel of a single‐screw extruder. The sensor's confocal optics design permits fluorescence intensity measurements as a function of position. Using a previously established calibration function, temperature and temperature gradients were obtained from the measured fluorescence. Because the origin of the measurement is the fluorescent dye molecule that is soluble in the resin, this method allows temperature measurement of the polymer without interference from the surrounding metal parts. With the sensor looking over the screw, temperature profiles from the barrel wall to the core of the screw were obtained as a function of screw speed, screw design and resin melt flow rate. Polym. Eng. Sci. 44:2148–2157, 2004. © 2004 Society of Plastics Engineers.

1 This paper is a contribution from the National Institute of Standards and Technology, and, thus, is not subject to copyright in the United States.

     

Hydrophilic foams containing corn products for horticultural use

Polyurethane foams containing equal amounts of commercial unmodified cornstarch and a polyisocyanate-terminated polyether exhibit properties suitable for horticultural applications. The use of cornstarch in the foam formulation increased the volume by one-fourth as compared to the foam without cornstarch. This volume increase represents an economic advantage of 20% savings based on material cost. When cornstarch or corn flour is added to the foam formulation, the foams are more resistant to compressive force. Upon wetting and draining, the foams prepared with no auxiliary blowing agent and containing corn products exhibit higher volumes than do the unfilled foams. Radish seeds planted inside 25 mm cubes of foams began to sprout after 1 day. Early developmental growth for the plants was similar in the control and cornstarch-filled foams. Spectroscopic analyses of the starch-containing foams revealed that 60–70% of the cornstarch was metabolized within 4–5 weeks by a microbial consortium. Control polyurethane foams were not affected by the microorganisms tested. © 1994 John Wiley & Sons, Inc.

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

     

Detection of Radicals at the Photolysis of tert-Butyl Hydroperoxide in DMSO and water

The decomposition of tert-butyl hydroperoxide by photochemically induced reactions in DMSO

1 Abbreviations used: DMSO, dimethyl sulfoxide; DMSO-d₆, completely deuterium labelled dimethyl sulfoxide; cw-ESR, continuous-wave Electron Spin Resonance; u. v., ultra violet; DMPO, 5, 5-dimethyl-I-pyrroline N-oxide; TMPO, 3, 3, 5, 5-tetramethyl-l-pyrroline N-oxide.

and water was investigated by cw-e.s.r. spectroscopy. The products tert-butylperoxyl, methyl and sulfur-centered free radicals were identified. The tert-butoxyl free radical is involved in the primary process as shown by time-resolved e.s.r. technique. On the basis of directly identified radical species, a mechanism for the photochemically induced reactions of tert-butyl hydroperoxide in DMSO is proposed. At concentrations below 0.8 mol · l⁻¹ the radical formation from tert-butyl hydroperoxide proceeds by cleavage of the O O bond rather than by hydrogen abstraction.     

Effects of jet-cooking conditions upon intrinsic viscosity and flow properties of starches

This work examined the sensitivity of intrinsic viscosity values of jet-cooked waxy maize starch to initial pH conditions and the effects of jet-cooker steam pressure parameters upon the intrinsic viscosity and flow viscosity values of four jet-cooked starches. Flow viscosities of the 10 wt % cooked starches and intrinsic viscosities in 90% DMSO-H₂O were the lowest when mixing and turbulence during steam jet-cooking was increased (i.e., by adjusting steam line pressure vs. pressure within the cooking chamber to allow greater amounts of steam to flow through the apparatus). The percent decreases of the intrinsic viscosity caused by the most severe cooking conditions compared to gentle cooking conditions were 52, 45, 32, and 12, respectively, for waxy maize, waxy rice, normal maize, and 70% high amylose maize starches. Initial pH values, from 3 to 10.5, of waxy maize starch had minor effects upon the intrinsic viscosity of the jet-cooked material. © 1996 John Wiley & Sons, Inc.

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

     

Behavior of amine-modified urea–formaldehyde-bonded wood joints at low formaldehyde/urea molar ratios

Urea–formaldehyde-bonded wood products are limited to interior nonstructural applications because of their poor durability under cyclic moisture or humid environments. The stability of solid-wood joints and particleboards can be enhanced by bonding with urea–formaldehyde adhesives modified with di- and trifunctional amines at an effective resin formaldehyde-to-urea mol ratio (F/U) of 1.6; however, particleboard formaldehyde emissions were not improved over those from boards made with unmodified adhesives and were unacceptably high. The relative effectiveness of selected modifications was investigated at resin form aldehyde-to-urea (F/U) molar ratios of 1.4 and 1.2 Solid-wood joints and particleboards made with modified adhesives, an unmodified adhesive, and a phenol formaldehyde (PF) resin were subjected to cyclic soak-dry (cyclic stress) treatments and moist-heat aging. Formaldehyde emissions from particleboards were also determined. At F/U 1.4, the resistance of solid-wood joints made with modified adhesives to cyclic stress and moist-heat aging was equal to that of PF-bonded joints and superior to that of joints bonded with unmodified adhesive. The resistance of particleboards made with modified adhesives was greater than that of boards made with unmodified adhesive but less than that of PF-bonded board. Solid-wood joints and particleboards made with F/U 1.4 resins performed better than did those made with F/U 1.2 resins. Particleboards made with F/U 1.2 resins had formaldehyde emissions well below the standard, and room temperature aging or bonding at high temperature reduced emissions substantially. © 1994 John Wiley & Sons, Inc. 1

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

     

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.     

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.     

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.     

Fracture behavior of coated/uncoated graphite-epoxy composites

The static delamination behavior of graphite/epoxy composite specimens subjected to mode I tensile opening (using UDCB

1 Uniform double cantilever beam.

specimens), and pure mode II shear loading (using ENF

2 End-notched flexural.

specimens) were studied. The graphite epoxy composites for the study were made from commercially treated fibers, with and without an electropolymerized interlayer. The mode I fracture energy (G_IC) was found to be significantly higher (more than 50 percent) for the coated fibers. However, this improvement was accompanied by a high reduction (more than 3 times) in the mode II fracture energy (G_IIC). This effect is apparently related to poor adhesion between the interlayer and the epoxy resin, which may be corrected by use of a “top layer” of appropriate composition to form chemical bonds between the phases. The fracture toughness (K_IC) of composites made with commercially treated fibers was also evaluated, using double side-notched specimens.     

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.     

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.     

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.     

Density of desublimed layers

Starting from the assumption that the growth of desublimed layers is governed mainly by heat and mass transfer, the authors present a model based on conditions in the diffusion boundary layer and suggest that the “hoarfrost”

1 Hereafter the term frost will be used instead of hoarfrost.

density depends on only one parameter. The discussion accounts for the process determining factors, i.e. the growth rate, mass transfer and gas concentration. The theoretical relationship is confirmed by the authors' own experiments on two systems and data from literature. The relationship can be established by a few laboratory experiments and permits the calculation of frost density and of associated variables, thus facilitating the optimization of desublimator design.     

Antioxidants and stabilizers, 107. Reaction of N-phenyl-1,4-benzoquinoneimine with the 1-cyano-1-methylethyl-radical

The reaction of N-phenyl-1,4-benzoquinoneimine (I)

1 Decoding of abbreviations see p. 103/104.

and 4-hydroxydiphenylamine (II) with the carbon centred 1-cyano-1-methylethyl radical (R^·) was studied in connection with an investigation of the action mechanism of industrial antidegradants, such as N-phenyl-N′-sec-alkyl-1,4-phenylenediamines. The mixture of I and II reacts very readily with R^·, giving rise to III , VI , and VIII . I alone reacts much slowlier, and the reaction mixture contains more products. IV and VII were identified along with III . Under the conditions used, II alone does not react at all. IV exists in two isomeric forms, syn and anti. VIII is very labile; XI was isolated from its transformation products. Reduction of IV gives V , which is labile, similarly to VIII .     

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.     

Synthesis and characterization of melt-polymerizable aminophthalocyanine monomers

The strategy, synthesis, and characterization of a soluble amine-functionalized phthalocyanine monomer and two examples of its polymerization into optically transparent glasses are reported. A simple, fast, and versatile method for incorporating metal ions into the metal-free phthalocyanine is demonstrated. Measurements of the nonlinear optical properties associated with a lead-substituted phthalocyanine/urethane copolymer are also reported. © 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.

     

The synthesis and properties of a cation-exchange resin prepared by the pyrolysis of starch in the presence of phytic acid

A black charcoal-like material having cation exchange and adsorption properties was prepared by the controlled pyrolysis of starch in the presence of a commercial phytic acid solution. Resins with binding capacities of 0.7–5.7 meq/g of calcium were prepared by varying the phytic acid to starch ratio, the temperature, or the duration of heating of the reaction mixture. SEM photomicrographs of some of these new materials showed that they are composed of particles similar in size and shape to the starting starch granules. These resins also removed atrazine from aqueous solutions. © 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.

     

Polyphosphazene membranes. II. Solid-state photocrosslinking of poly[(alkylphenoxy)(phenoxy)phosphazene] films

The solid-state UV photocrosslinking mechanism and the properties of dense crosslinked films composed of poly [(methylphenoxy)(phenoxy)phosphazene], poly[(ethylphenoxy)(phenoxy)phosphazene], and poly[(isopropylphenoxy)(phenoxy)phosphazene] were investigated, where the alkyl substituent was in either the meta- or para-position. Solution-cast films containing dissolved benzophenone photoinitiator (at a concentration of 1–25 mol %) were crosslinked at either 25 or 70°C. The ordering of benzophenone disappearance during polymer irradiation was methylphenoxy > ethylphenoxy > isopropylphenoxy, indicating that the rate controlling step for photoinitiator disappearance was the consumption of benzophenone, either by benzopinacole formation (with the creation of a polymer crosslink) or by reaction of a benzophenone-derived ketyl radical with a polymer macro-radical. The presence of such a ketyl adduct in crosslinked ethylphenoxy/phenoxy and isopropylphenoxy/phenoxy phosphazene films was verified by solid-state NMR. The ordering of crosslinked polymer swelling (for a given initial benzophenone concentration) when films were equilibrated in dimethylacetamide (DMAc) was isopropylphenoxy/phenoxy > ethylphenoxy/phenoxy > methylphenoxy/phenoxy, indicating that steric effects of the alkyl group were playing a role during crosslink formation. The methylphenoxy/phenoxy phosphazenes were the best materials for crosslinking; the glass transition temperature increased by approximately 25°C (from −15 to 10°C) and the film swelling (in DMAc) decreased from infinity (complete solubilization) to 35% as the benzophenone concentration was increased from 0 to 25 mol %. © 1998 John Wiley & Sons, Inc.

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

J Appl Polym Sci 68:827–836, 1998     

A simple dilatometer for thermoset cure shrinkage and thermal expansion measurements

A simple capillary and bulb mercury dilatometer designed for specific volume measurements on thermoset resin systems during the curing reaction and as a function of temperature is described. The design, calibration, operation, data treatment, and error analysis are presented in detail, with data on the bisphenol A dicyanate resin system used as an example. Particular attention is directed at experimental difficulties such as monomer/prepolymer degassing, filling the dilatometer under vacuum, adhesive distortion of the curing resin on the dilatometer bulb, and the dilatometer bulb to capillary connection problem. © 1994 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.

     

Thermomechanical properties of blends of pectin and poly(vinyl alcohol)

Blends of citrus pectin and several types of poly(vinyl alcohol) were investigated to determine the effects of compositional variables and polymer type on film properties. Some films were also plasticized with glycerol. Films were cast from water onto Lexan™ plates, dried, and removed. Thermomechanical properties were obtained using a dynamic mechanical analyzer, and thermodynamic transitions were also obtained using a differential scanning calorimeter. Increasing the amount of poly(vinyl alcohol) in the blends reduced the storage and loss modulus of the films above the glass transition temperature (T_g). The T_g values observed decreased as the amount of PVOH in the blend increased. Addition of glycerol depressed the PVOH T_g and merged it into the T_g of the pectin/glycerol blend. Changes in the molecular weight and degree of ester hydrolysis of poly(vinyl alcohol) exerted a rather small effect on the blends. © 1996 John Wiley & Sons, Inc.

1 Reference to a brand or firm name does not constitute an endorsement by the U.S. Department of Agriculture over others of a similar nature.