Magnetic field processing of polymers. I. Hydroxypropyl cellulose

Hydroxypropyl cellulose (HPC) of degree of substitution three and average molecular weight of 100,000 was processed in a magnetic field of 1.2T. Films of HPC were cast from water, methanol, ethyl methyl ketone, and 1,1,2,2-tetrachloroethane solutions in a magnetic field using static and dynamic casting techniques. The processed films were evaluated for tensile strength, elastic modulus, microhardness, and molecular chain alignment by wide angle x-ray diffraction and polarized infrared. The best alignment and hence the greatest improvement in properties was obtained using a combined magnetic field and flow alignment procedure. These samples showed no increase in the elastic modulus, a 106% increase in the tensile strength, a 21% increase in the microhardness, and were dichroic. © 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.

     

Physical and mechanical properties of highly plasticized pectin/starch films

Blends of citrus pectin and high amylose starch plasticized with glycerine were investigated to determine the effect of compositional variables on film properties. Several films with representative compositions were made from sugar beet and almond pectin, and tested for comparison. The films were cast from water onto glass plates, dried, and removed. Mechanical analysis was done using a Rheometrics RSA II solids analyzer. Increasing the glycerine concentration led to decreases in static modulus, dynamic modulus, and tensile strength, but to increases in elongation. Increasing levels of starch in the blend lowered the effect of glycerine on mechanical properties. Oxygen permeability of the films was extremely low. Sugar-beet pectin and almond pectin gave films with mechanical properties comparable to those made with citrus pectin. © 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.

     

Effect of fiber-matrix adhesion on the properties of short fiber reinforced ABS

The tensile strength, fracture energy, and impact strength of ABS reinforced with discontinuous crystalline fibers such as Fybex

1 Du Pont trademark.

can be controlled by manipulating fiber-matrix interfacial adhesion. In “good bonding” situations composite tensile strength, thermal expansion coefficient, and elastic moduli are significantly improved over the unfilled resin. The excellent impact strength of unreinforced ABS can be retained by lowering the fiber-matrix interfacial adhesion. This results in a corresponding reduction in the improvements in tensile and flexural strength. However, the elastic moduli and thermal expansion coefficients are relatively insensitive to changes in adhesion. Consequently, a material with high modulus (>500,000 psi), high Izod impact resistance (7.0 ft-lb/in.), and low expansion coefficient (3.0 × 10^?5 in./in./°F) can be obtained. A material with this unique combination of properties should find use in large parts such as camper tops, truck grilles, and snowmobile bodies. Fiber-matrix adhesion was measured directly by an x-ray analysis technique which could be employed because of the fiber's crystallinity and unique growth habit. This independent measurement allowed a correlation between bonding and composite properties. The interfacial bond strength was manipulated by a variety of fiber coatings and resin additions.     

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.     

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.     

Low dielectric,fluorinated polyimide copolymers

Copolymers of fluorinated polyimides and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) have been prepared as films and composite laminates. The addition of BPDA was used as a means to achieve insolubility, making the polymers suitable as aircraft matrix resins. Glass transition temperatures, thermooxidative stabilities, and tensile strengths were increased with increasing BPDA content in the copolymers. Although the addition of BPDA did increase the UV cutoff and decrease the percent transmission slightly, the optical transparency of the polymers was still excellent. Dielectric constants of the copolyimide films ranged from 2.6 to 2.9. Astroquartz II laminates made with these resins had dielectric constant of 3.3–3.4. Flexural strength on unidirectional specimens were in the 1.24–1.41 GPa range and flexural moduli were 41 GPa. © 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.

     

Grafting of methyl methacrylate on isoprene rubber

Methyl methacrylate has been grafted on artificial isoprene rubber (IR) latex, with use of redox initiation. The properties of latices containing up to 40 phr

1 Parts per hundred parts of rubber.

methyl methacrylate (MMA) as well as solid products containing up to 80 phr of this compound were studied. Compared with ungrafted IR latex with the same solids content, the grafted IR latices had a lower viscosity, owing to their particle size being larger. Vulcanised films obtained from the grafted latices showed a considerably higher modulus, particularly at large deformations, than those based on IR or blends of IR with polymethyl methacrylate. by incorporation of certain reinforcing white fillers in the MMA-grafted IR latices, a further increase in the modulus of the latex films was effected.     

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     

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.     

The effects of morphology and hygrothermal aging on water sorption and transport in Kapton® polyimide

A comparison of water sorption and diffusion behavior in 2 mil, as-received, Kapton

1 = Trademark of E.I. Dupont de Nemours Inc.

film, and in otherwise identical but hygrothermally aged samples, suggests chemical differences between the samples. These differences can be related to known polyimide chemistry and the specific history encountered by the samples. Although the sorption isotherms are similar for an as-received 0.3 mil sample studied earlier and for the as-received 2 mil samples studied here, the diffusion coefficient of water in the as-received 2 mil sample is approximately 300% larger than in the as-received 0.3 mil sample. This large effect is believed to be related to the presence of small, paracrystalline aggregates with large aspect ratios. Differences in orientation measured by birefringence for the two samples suggest that the barrier properties of Kapton^® are strongly affected by the detailed morphological organization of the ordered aggregates. Comparison of the sorption isotherms for the as-received and hygrothermally aged 2-mil films suggests a significant increase in the hydrophillic nature of the aged film. This change is consistent with an apparent chemical reaction between water and uncyclized amic acid residues in the film. The tendency for water to cluster in as-received Kapton^® is essentially eliminated by the chemical modification associated with hygrothermal aging. The hygrothermal aging produces a dramatic reduction in the water vapor diffusion coefficient at low vapor activities but a rather modest change at high activities.     

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.

     

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.     

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.

     

Ultra-high strength polyethylene by hot drawing of surface growth fibers

Summary Hot drawing at 150°C has been applied to high molecular weight polyethylene fibers produced by flow induced crystallization in a Couette apparatus, referred to as the surface growth technique. A distinct improvement of the tensile properties of the fibers was noticed upon drawing. A tensile strength at break of 4.7 GPa was reached. Drawability is discussed in relation to fiber morphology. The shish-kebab like structure of the surface growth fiber was transformed into a morphology consisting of smooth fibrils upon drawing.     

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.     

Difurfuryl diisocyanates: New adhesives derived from renewable resources

The syntheses of difurfuryl diisocyanates [e.g., ethylidenebis (2,5-furandiylmethylene) diisocyanate (EDFI)] have been reported in the literature. Difurfuryl diisocyanates are structurally similar to diphenylmethane diisocyanate (MDI), which has proven to be an excellent adhesive for bonding wood composites. The MDI regin is synthesized from petroleum-derived chemicals; the EDFI resin is synthesized from biomass-derived chemicals. In this study, the mechanical properties of aspen flakeboards bonded with MDI and EDFI are compared. In general, results show that the strength properties of flakeboards bonded with MDI are only marginally better than those bonded with EDFI. Because EDFI is more viscous than is MDI less than optimum atomization of the EDFI resin during spraying of the flakes is believed to be largely responsible for the differences in strength property values. The dry internal bond strength values of flakeboards bonded with MDI (1.33 MPa; 193 lb/in.²) at 3% resin content are significantly greater than the 0.41 MPa (60 lb/in.²) required by the American National Standards Institute (ANSI/A208.1) for type-2 medium-density particleboard. © 1993 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.

     

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.

     

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 use of volume-averaging techniques to predict temperature transients due to water vapor sorption in hygroscopic porous polymer materials

Volume-averaging techniques developed for modeling drying processes in porous materials offer a convenient framework for analyzing vapor sorption in porous hygroscopic polymeric materials. Because of the large temperature changes associated with water vapor sorption in these materials (from 10° to 20°C), sorption/diffusion processes are best characterized through the coupled differential equations describing both the transport of energy and mass through the porous structure. Experimental and numerical results are compared for a variety of natural and man-made porous polymeric materials (textiles) using the volume-averaging technique. Boundary heat and mass transfer coefficients and assumptions about thermal radiative properties of the experimental apparatus are shown to influence results obtained with the numerical solution method. © 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 64: 493–505, 1997