John A. Cuculo

The Solubility of Unmodified Cellulose: A Critique of the Literature

Abstract Petrochemical, shortages have stirred renewed interest in cellulose because it is the single replaceable raw material, and exists in great abundance. This literature survey reviews the cellulose solvent systems that do not in general rely on stable cellulose derivatives that can be isolated. This review is arranged in a manner suggested by Turbak [1] that classifies all cellulose solvents by the nature of their interaction with cellulose. An alternate classification, presented in Section VI, mainly for the benefit of the pragmatist, reappraises the various solvents in terms of aqueous or nonaqueous systems. When available, the minimum information on the properties of regenerated and coagulated cellulose is provided to further assist in assessing the overall potential of the many different systems capable of dissolving cellulose.

Structure and property studies of poly(ethylene terephthalate)/poly(ethylene-2,6-naphthalate) melt-blended fibres

Abstract The effects of blend composition and take-up velocity on structural variations and physical properties of poly(ethylene terephthalate) [PET]/poly(ethylene-2,6-naphthalate) [PEN] blend fibres were studied using WAXS, n.m.r., d.s.c., density, tensile and thermal shrinkage tests. Over the ranges studied, the structure and properties of the blend fibres were significantly influenced by the composition and melt spinning velocity. With the increase in content of any second component (PEN or PET), the crystallization process in the as-spun fibres becomes difficult, because of the formation of random copolymers via a transesterification reaction occurring between PET and PEN molecules. This reaction also produces a miscible amorphous phase with the result that all blend samples exhibit a single glass transition temperature intermediate to those of the two homopolymers. The WAXS results of annealed samples, however, indicate separate crystals for the two components rather than a co-crystallization. Room temperature mechanical properties, for fibres spun at constant take-up velocity, improved gradually with increasing PEN content. The thermal shrinkage, however, is relatively high for blend fibres and reaches a maximum for the 50/50 PET/PEN blend, indicating that the copolymer chains are oriented fairly well, but exist in the amorphous state.

Oriented noncrystalline structure in PET fibers prepared with threadline modification process

The development of an oriented noncrystalline phase in a semicrystalline polymer filament has been studied via X-ray scattering. These unique PET fibers contain a relatively high noncrystalline content and also have high tenacity, high modulus, and low breaking elongation. Fiber properties were found to be very responsive to the oriented amorphous phase content. This phase was utilized for interpreting noncrystalline orientation in PET fibers produced by a new extrusion technique. Here, the oriented noncrystalline regions in a series of PET fibers varies from 6% to 63%, depending strongly on the production conditions. In particular, samples produced with a newly developed threadline modification process possess a high content of oriented noncrystalline polymer. Measurements such as dynamic and static mechanical properties have been performed on various samples, and these properties are related to the oriented noncrystalline phase. The results provide direct evidence for the existence of highly oriented noncrystalline material in these unique PET fibers spun with a threadline modification process.

High performance poly(ethylene terephthalate) fibre properties achieved via high speed spinning with a modified liquid isothermal bath process

Abstract A liquid isothermal bath (LIB) was used in the spinline to produce high performance poly(ethylene terephthalate) (PET) fibres at high speed melt spinning in a one step process. The take-up stress was measured under various spinning conditions. It was found that maximum applicable take-up stress was determined by the state or morphology of the filament before entering the liquid bath. To render the filament more amenable to a preferred morphological texture prior to its entry into the liquid bath, a small amount of hot liquid was applied to the running filament at a position upstream of the liquid bath. The results show that rapid cooling leads to a non-uniform fibre structure and the loss of subsequent filament deformability. However, the prolongation of attenuation, attendant the heating of the filament before entering the liquid bath, induced uniform radial structure and an increase of deformability. Then the maximum operable liquid depth within the LIB could be attained. Furthermore, the delay of attenuation in the upper portion of the liquid bath and the attendant increase of stress within the liquid bath also resulted in an increase of the tensile properties. The modified LIB process was suggested as a further control of the temperature profile upstream of the liquid bath. High tenacity (9.7 g d−1), high modulus (>120 g−1) and high load at a specified elongation of 5% (LASE-5) (>4 g d−1) PET of as-spun fibres are achievable using the modified LIB one step process. The as-spun fibres produced with the modified LIB process have high amorphous orientation, low crystallinity and relatively large crystalline size. After drawing and annealing, the fibres exhibit desirable characteristics of high tenacity (>11 g d−1), high modulus (>140 g d−1), high LASE-5 (5.8 g d−1), and low shrinkage (

High performance PET fibre properties achieved at high speed using a combination of threadline modification and traditional post treatment

Abstract A process was investigated for producing high modulus, high strength, dimensionally stable poly(ethylene terephthalate) (PET) filament by combination of threadline modification and post drawing techniques. Unlike traditional commercial processes for the production of PET filament yarn, the present process uses a liquid isothermal bath to develop an extremely high level of tension in the threadline. This results in extremely high amorphous orientation and low crystallinity in the as-spun fibres, with good mechanical properties, similar to those found in products produced using a commercial spin-draw process. The oriented amorphous structure produced directly by such a modified spinning process can be further oriented by a subsequent hot-drawing operation, resulting in a final PET filament product which possesses ultra-high birefringence ( Δn > 0.23) and excellent mechanical properties. The tenacity, elongation, and initial modulus ( T/E/M ) are, respectively, in the range of 9.5–10.7 g d −1 , 6–9%, and 130–150 g d −1 . Experimental filaments also exhibit excellent resistance to yielding within the range of small strain, with tensile stress values as high as 5–7 g d −1 being observed at 5% elongation. This superior balance of properties, high modulus, high tenacity and high dimensional stability, is unprecedented in conventional commercial processes for the production of PET filament.

Polymer Flow Instability: A Review and Analysis

Abstract In the flow of polymeric materials through small orifices, it was recognized early that if flow parameters such as shear stress or shear rate exceeded certain critical values, the extrudate emerging from the die would exhibit surface defects or irregularities in cross-section. Since the extrusion of molten plastics, elastomers, and fibers is such an important industrial operation and the production of extruded products is limited to rates below those which produce extrudate distortion, the study of this phenomenon became important. In the last 30 years many descriptions and experiments of the onset of extrudate distortion and its accompanying flow behavior have appeared in the literature. This literature has attained such proportion that it has been subject to several reviews in recent years [1-6].

Morphological characteristics of the lyotropic and gel phases in the cellulose/NH3/NH4SCN system

Solutions of cellulose in the ammonia/ammonium thiocyanate (24.5/75.5 w/w) solvent form several stable phases. Of particular interest in this work are the temperature-dependent liquid crystalline and gel phases which are stable at cellulose concentrations above 6% w/v. While the temperature-composition conditions yielding these phases are reasonably well established, very little is currently known about the morphological characteristics of lyotropic and gelled cellulose. Polarized light microscopy is employed here to demonstrate that solutions at temperatures above the gel melting point are birefringent, composed of liquid crystals. Field-emission scanning electron microscopy has been used to (i) examine the three-dimensional network in cellulose gels, and (ii) correlate network morphology with cellulose molecular weight and solution concentration. Results obtained from two complementary sample preparation techniques (i.e., critical point drying and freeze drying) are compared to identify and minimize artifacts, and reveal that gel formation occurs as the solutions phase-separate into polymer-rich anisotropic and solvent-rich isotropic phases. The polymer-rich phase is highly interconnected and forms a fibrillar network, with fibrils measuring 20-70 nm in diameter.

High-performance PET fibers via liquid isothermal bath high-speed spinning : Fiber properties and structure resulting from threadline modification and posttreatment

Poly(ethylene terephthalate) fibers with improved mechanical properties and dimensional stability were spun via controlled threadline dynamics by a liquid isothermal bath (LIB) spinning process, followed by postdrawing and annealing. Control fibers were made by unperturbed spinning and posttreatment similar to a traditional spin—draw process. The two sets of as-spun fibers were spun at take-up speed in the range of 2000–5000 m/min. Fiber properties of the as-spun fibers and posttreated fibers of each process were compared. Two commercial tire cords, i.e., conventional tire cord and low shrinkage tire cord, were also included. Unlike unperturbed spinning, the LIB as-spun fibers show unique structural properties of high amorphous orientation, low crystallinity, high strength, and high initial modulus. Moreover, noncrystalline chains are further extended during posttreatment. The posttreated LIB fibers exhibit mechanical properties with tenacity higher than approximately 9 g/d, initial modulus higher than 120 g/d, and ultimate elongation less than approximately 10%. They also demonstrate superior dimensional stability with thermal shrinkage less than 6% and LASE-5 higher than 5 g/d. The overall properties are not obtainable by either the traditional spin—draw process or any modified process that produces low shrinkage tire cord. Unlike the case for unperturbed fibers, the mechanical properties of the posttreated LIB fibers demonstrate a strong/dependency on the birefringence of their respective as-spun fibers. There are at least three significant pieces of evidence that strongly indicate the existence of a third phase, referred to as the taut—tie noncrystalline phase (TTNC), in addition to the traditional two-phase model, i.e., crystalline and random amorphous phases. A unique feature involving a high fraction of taut—tie noncrystalline phase (TTNC %) in the LIB as-spun and the posttreated fibers is also found and which is, in fact, achieved neither by the traditional spin—draw nor the commercial tire cord processes. Further, different from the posttreated unperturbed fibers, the posttreated LIB fibers have an enhanced fraction of taut—tie noncrystalline chains with shorter length, which is believed to be one of the important factors leading to the superior mechanical properties and excellent dimensional stability achieved.

Formation and characterization of the fibres and films from mesophase solutions of cellulose in ammonia/ammonium thiocyanate solvent

Abstract Fibres and films were formed from mesophase solutions of cellulose in ammonia/ammonium thiocyanate solvent. The physical properties of the fibres and films were discussed on the basis of the properties of the mesophase solutions used. Cholesteric and nematic phases were formed in the solutions. Fibres were extruded from both kinds of solution. The fibres from the nematic solutions were more highly oriented, had a more fibrillar texture and were apparently stiffer than those from the cholesteric solutions. The fibres spun from the nematic solutions using the technique of dry jet-wet spinning had moduli comparable to those of Fortisan ® .

Pad-Bake Reactions: Part II: A New Pad-Bake Reaction of Cellulose and Aqueous Solutions of Anhydride-Ammonia

A new anhydride/ammonia-cellulose reaction has been developed. It has led to a fast, simple, pad-hake process for modifying cellulose. The structure of the modified reaction product is presumed to be a cellulose half-acid ester. The easily synthesized cellulose ester derivative may be of possible value as a precursor for subsequent reactions to obtain cellulose fabrics with improved properties. Cellulose hemisuccinate, phthalate, and maleate, are reported.