The mechanical properties of epoxy resins and epoxy resin/graphite fiber composites are adversely affected by moisture absorption. Incorporation of masked isocyanates that unmask to release isocyanates in situ at the cure temperatures (150-177ºC) reduce the equilibrium absorption up to ∼70%. Dynamic mechanical analyses and stress-strain properties of epoxy resins containing masked isocyanates were examined to determine their effect on mechanical properties. The ultimate Tg of the epoxy is reduced by incorporation of masked isocyanate, but the actual Tg is comparable to the “as cured” Tg of the epoxy. The dynamic moduli up to the Tg are relatively unaffected. Ina number of cases, the initial modulus, elongation at break and peak stress are equal or better than the unmodified resins.

A series of phenylacetoxy cellulosics with degrees of substitution (DS) between 1.4 and 3.0 and different halogenation (2-chloro, 3-chloro, 4-chloro, 2,4-dichloro, 3,4-dichloro, and 4-bromo) were synthesized. All the prepared phenylacetoxy cellulosics were soluble in dimethylformamide (DMF) and DMAc. The solubility increased with increasing DS. Mesophases were observed for all of the phenylacetoxy cellulosics with low to medium DS (DS < 2.5) in DMF and DMAc. Non- or mono-halogeneated phenylacetoxy cellulosics with high DS (DS > 1.9) were soluble in methylene chloride (CH2Cl2), whereas those with very low DS or di-halogenation on the phenyl ring were only slightly swollen or partially soluble in CH2Cl2. Non- and mono-halogenated phenylacetoxy cellulosics were soluble in DMSO and formed liquid crystals regardless of the DS, in contrast to CH2Cl2 solutions which display liquid crystalline behavior at medium to high DS (DS > 1.9) only. The solubility of the di-halogenated phenylacetoxy cellulosics in DMSO was limited to approximately 40 wt %.

Supercritical carbon dioxide (SC-CO 2 ) extractions of paraffin-based wax coatings from saturated and curtain-coated old corrugated containers (OCC) are reported. Extractions were performed in a 500-mL reactor (300 bar, 100°C, 50 g CO 2 /min and 1 h). Wax removal efficiencies of 98 and 70% for saturated and curtain-coated OCC, respectively, were obtained. Under similar conditions, extractions in the presence of water resulted in an extraction efficiency of 99% for saturated OCC. Decreasing the operating pressure to 200 bar decreased the extraction efficiency to approximately 50%. Gas chromatography (GC) of the wax coatings on OCC, before and after extraction with SC-CO 2 , showed a slight shift in the molecular weight distribution of the paraffin wax (after SC-CO 2 extraction) toward higher molecular weights for both saturating wax and curtain-coating wax. There was no evidence of chemical degradation or modification of the paraffin wax coatings by SC-CO 2 The packing density, packing arrangement, and dimensions of the curtain-coated OCC in the extraction apparatus affected the extraction efficiency. Loose packing compared to tight packing, 1 X 1 cm squares versus 1 X 20 cm strips, had higher extraction efficiencies; a random packing arrangement was better than packing with the fluting material in the direction of SC-CO 2 flow.

Carbon fibers have been produced for the first time from a commercially available kraft lignin, without any chemical modification, by thermal spinning followed by carbonization. A fusible lignin with excellent spinnability to form a fine filament was produced with a thermal pretreatment under vacuum. Blending the lignin with poly(ethylene oxide) (PEO) further facilitated fiber spinning, but at PEO levels greater than 5%, the blends could not be stabilized without the individual fibers fusing together. Carbon fibers produced had an over-all yield of 45%. The tensile strength and modulus increased with decreasing fiber diameter, and are comparable to those of much smaller diameter carbon fibers produced from phenolated exploded lignins. In view of the mechanical properties, tensile 400–550 MPa and modulus 30–60 GPa, kraft lignin should be further investigated as a precursor for general grade carbon fibers.

Release liner waste material is found in post-consumer waste streams and is also a significant component of the preconsumer waste stream generated in the manufacturing of adhesive products. To date, very little has been reported pertaining to the behavior of release liner in paper recycling. In this study, the effect of the release liner material on the behavior of adhesive contaminants during laboratory pulping was investigated by dyeing the adhesives and the release liner with a blue dye and performing image analysis. The presence of release liner in the furnish caused a decrease in the size and an increase in the number of adhesive particles after pulping. The recyclability of the release liner was evaluated by processing a wastepaper furnish containing release liner and copy paper (no adhesive) through a laboratory pulping, screening, centrifugal cleaning and flotation processes. The release liner was removed with a laboratory screen and a laboratory centrifugal cleaner both with high efficiency but was not removed with a laboratory flotation device. The presence of residual release liner particles in recycled paper decreased the strength and printing properties of the recycled paper significantly.

The melt spinning of two thermotropic cellulose derivatives—trimethyl silyl cellulose and phenyl acetoxy cellulose—is described in this article. Removal of the substituents was facile, rapid, and essentially complete. Both the melt-spun and regenerated fibers had banded textures typical of fibers spun from a liquid crystalline phase. The regenerated cellulose fibers had high strengths and moduli compared to viscose rayon and Lyocel cellulose fibers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 418–423, 2000

Cationic species are often introduced into coating formulations to improve print quality and waterfastness. This study investigates the effects of three ionic species-polydiallyl dimethyl ammonium chloride (poly-DADMAC), ammonium zirconium carbonate (AZC), and zirconium acetate (ZAA)-on the rheologicol, optical, and printing properties of a silica/polyvinyl alcohol matte ink-jet coating All three additives increased the steady-shear viscosity and the dynamic elastic modulus of the coating formulations, with the sample containing poly-DADMAC exhibiting the largest increases. The a cationic additives did not improve she ink density of printed samples, but the poly-DADMAC samples showed i superior waterfastness, with the highest level of ink density. In addition, poly-DADMAC samples exhibited lower levels of print bleeding than samples without additives. However, SEM photographs reveal that addition of poly-DADMAC produces a hard, inflexible coating structure that tends to crack during drying.

In this study, a set of pulps containing different PSA products that were recycled at the Forest Products Laboratory (FPL) pilot plant were analyzed for deposition using the PIRA deposition device at North Carolina State University. The work is part of the United States Postal Service Environmentally Benign Pressure Sensitive Adhesive effort. The deposition device consists of a counter-rotating paper machine wire immersed in a low consistency pulp suspension. The contrast between the deposited PSA and the paper machine wire was increased by selectively dyeing the PSA deposited on the wires. Image analysis was performed on the wires to provide a value of the overall ppm, average size, and size distribution of deposits on the wire. The same pulps were dyed with an adhesive specific dye to increase the contrast between adhesive and fiber and image analysis was performed on handsheets at the FPL. The deposition results were found to correlate in general with image analysis results of the same pulp.

This study examines the interaction between carboxymethylated chitosan and clay by determining effects of carboxymethylated chitosan on microstructure, rheology, and water retention ability of clay. Results are compared to that of clay and alginate systems whose interactive chemistry and relationship to water retention has been recently studied. Microscopy results of the interactions between the carboxymethylated chitosan and clay correlate to the water retention ability and dynamic and steady rheological measurements. The degree of interaction of carboxymethylated chitosan and clay mixtures relates directly to the water retention properties of the clay. The resulting properties are different from that of clay and alginate mixtures.

The water retention properties of starch solutions containing Ca++ complexed alginates were investigated. The viscosities and water retention properties were found to be considerably higher for the complexed alginate than for the non-complexed alginate, but the complex was easily destroyed upon the addition of a sequestering agent. The water retention of the alginate could be manipulated with the level of Ca++ ion added, with more ions providing better water retention. Greatly reduced levels of the complexed alginates provided better water retention than the non-complexed alginates. This is of commercial importance as lower levels of complexed alginate are required to obtain the same level of water as a non-complexed alginate.