Crystalline character of native and chemically treated Egyptian cottons. I. Computation of crystallinity,disorder parameter,orientation factor,and spiral angle

Computer data processing and electronic monochromatization of x-rays were employed for determining crystallinity, disorder parameter, Hermans' orientation factor, as well as DeLuca and Orr spiral angle of native, mercerized and urea-treated cottons. The results indicate the values for the degree of crystallinity to vary significantly between ecttons. Increase in disorder on mercerization is confirmed. The effect of urea treatment is not so well defined. The differences in Hermans' x-ray orientation factor are significant at the 1% level between cottons and at the 10% level between treatments. Besides, from a critical analysis of the values obtained, it is shown that the spiral angle φt in the method of DeLuca and Orr is probably a direct estimate of the mean inclination of the crystallites to the fiber axis, while Hermans' orientation angle β is a complex function of other parameters as well. The computer programs which could be applied to other polymers are included.     

Behavior of chemically modified cottons towards thermal treatment. II. Cyanoethylated cotton

Mill-scoured and bleached cotton fabric, alkali-treated cotton, and cyanoethylated cottons having 0.1%, 0.47%, 0.89%, and 1.25% nitrogen were subjected to thermal treatments. The latter were carried out at different temperatures for different durations of time. Chemical degradation of the substrates brought about by thermal treatments was assessed by copper number, carboxylic groups, nitrogen content, and degree of polymerization whereas deterioration was measured by tensile strength and elongation at break. It was found that: (a) alkali-treated cotton undergoes higher degradation than cyanoethylated cottons; (b) cyanoethylated cottons are more susceptible to degradation than the original (mill-scoured and bleached) cotton; (c) the magnitude of deterioration of the substrate is determined by the previous chemical treatments; and (d) with cyanoethylated cotton, the higher the cyanoethyl content (expressed as % nitrogen) the greater the DP and tensile strength.     

Study of kinetics in the biosorption of lead onto native and chemically treated olive stone

In this research, olive stone was used as precursor for the development of new biosorbents for lead ions. Chemical treatments were analyzed in terms of their effects on physical–chemical properties and kinetics of lead removal. A kinetic study of the biosorption of lead ions by olive stone was analyzed according to six different kinetic models (pseudo first, pseudo second, pseudo n-order, Elovich, solid diffusion and double exponential models). The biosorption kinetic data were successfully described with pseudo-nth order and double exponential models for all biosorbents. The double exponential model allowed estimating the values of external and internal mass transfer coefficients. The values of external mass transfer coefficient (k_e) ranged from 42.62 × 10⁻⁶ to 508.3 × 10⁻⁶ m min⁻¹ and the internal mass transfer coefficient (k_i) from 3.76 × 10⁻⁶ to 73.4 × 10⁻⁶ m min⁻¹. On the other hand, the analysis of experimental data showed that chemical treatments of the biomass led to increase biosorption capacity of the native biomass.     

Changes in porosity of treated lint cotton fibers. II. Treatments for chemically modifying cotton

Changes in the internal morphology of chemically modified lint cotton fibers were investigated by measurement of nitrogen adsorption at liquid nitrogen temperature. Surface areas and pore size distributions were calculated from the adsorption isotherms and compared with findings from measurements of changes in crystallinity and of fibrillar aggregation as shown by electron micrographs. Fibers were either preswollen in water or taken from the rinse water and solvent exchanged through methanol and n-pentane to helium before adsorption measurements were made. Unless reacted in the presence of water, the wrinkle resistance treatments studied caused losses in surface area of 55% or greater. Changes in surface area and porosity of cottons reacted with monofunctional reagents designed to give protective and other types of finishes were dependent on the type of reaction used.     

Behavior of chemically modified cellulose towards dyeing. XIV. Behavior of cotton and crosslinked cottons before and after mercerization towards some reactive dyestuffs

Cotton fabric was crosslinked with DMDEU by applying the Form D-Process and Form W-Process. The cotton and crosslinked cotton were then treated with caustic soda solution of mercerizing strength. The ability of cotton and crosslinked cottons to dyeing with two reactive dyes, viz. Procion Blue MRB and Procion Red HB was examined. It was found that crosslinking reduces significantly the amenability of cotton to reactive dyes particularly when the Form D-Process was applied. Mercerization enhances dyeability of all substrates, but the enhancement was much greater in the case of noncrosslinked cotton. Based on dyeing and other properties such as tensile strength, elongation at break, and crease recovery, it was shown that crosslinking decreases considerably the affinity of cotton to caustic soda solution. It was further anticipated that different color designs with different patterns and properties can be conferred on a given cotton fabric by making use of local crosslinking and/or mercerizing followed by dyeing.     

Computation of forced convection in slow flow through ducts and packed beds—II velocity profile in a simple cubic array of spheres

The velocity profile is calculated for slow three-dimensional flow through a simple cubic array of spheres. The velocity is represented by stream-function expansions which directly satisfy the equation of continuity and the no-slip conditions. The problem is solved by a variational principle which gives a lower bound on the total flow rate. The computed bound is within 0·2 per cent of the experimental results of Martin et al.[6].     

Graft copolymerization of vinyl monomers on modified cottons. XVIII. Grafting of methyl methacrylate and acrylonitrile on cotton treated with N-methylol crosslinking agents using tetravalent cerium as initiator

Ce^IV-induced grafting of methyl methacrylate and acrylonitrile on cotton fibers crosslinked with dimethylol ethylene urea, dimethylol dihydroxyethylene urea, and dimethylol carbamate was investigated. The graft yields obtained with crosslinked cotton were signifcantly lower than the untreated cotton, irrespective of the crosslinking agent and the monomer used. However, the extent and rate of grafting depended upon the degree of crosslinking and the nature of monomer. Based on the magnitude of grafting and Ce^IV consumption during grafting and oxidation of the untreated and crosslinked cottons, the different reactions occurring during grafting of vinyl monomers on these modified cottons were elucidated.     

Crosslinking of PVC formulations treated with UV light. II. Color formation and viscoelastic properties

Two wire coating PVC formulations stabilized with Ca/Zn systems and one stabilized with a traditional lead compound were prepared. All three formulations contained trimethylolpropane trimethacrylate (TMPTMA) as a crosslinking agent and Irgacure 819 as a UV photoinitiator. Small specimens of hot‐pressed materials with 1.0 and 1.5 mm thicknesses were irradiated with UV light for 10 days, while monitoring changes at different time intervals. The presence of TMPTMA in the samples influenced the coloration of the lead‐stabilized formulation, while the others experienced the usual color formation after UV treatment, as seen by Yellowing Index measurements and corroborated by the evaluation of fluorescence spectra. The elastic modulus (E′) determined by DMA was shown to be sensitive to surface changes associated with crosslinking, while the loss modulus (E″) determined by DMA and the complex modulus (E*) obtained by TMA were shown to be sensitive indicators of bulk property changes. J. VINYL ADDIT. TECHNOL., 13:189–194, 2007. © 2007 Society of Plastics Engineers     

Wood fiber–synthetic polymer composites. II. Laminates of treated fibers and polyolefins

Flexural properties of laminates prepared by hot pressing commercial papers and laboratory handsheets with films of polyolefins were measured following exposure to different levels of moisture. Prior to their incorporation in the laminates, the fibers, either individually or as preformed paper, were acetylated or crosslinked with formaldehyde to reduce their sensitivity to moisture. The results are compared with earlier measurements which showed that the properties of laminates based on paper precoated with polyethylene declined sharply at high relative humidities. For laminates comprising laboratory handsheets made from acetylated fibers, the decline in properties is less but the initial values under dry conditions are lower also. However, acetvlation or crosslinking of preformed paper improves up to threefold the retention of flexural modulus by the laminates under the wettest conditions with no concurrent loss in this property under dry conditions, although some embrittlement of the component paper sheets is observed. Enhanced fiber alignment or the addition of 5% glass fibers to the paper does not arrest the decline in flexural properties of the laminates with increasing relative humidity. This decline differs little when other polyolefins are used but is accentuated when ethylene–vinyl acetate copolymer is the binder.     

Simulation of aerosol dynamics and transport in chemically reacting particulate matter laden flows. Part II: Application to CVD reactors

A highly computationally efficient and accurate semi-implicit numerical technique based on the concept of operator splitting (described in detail in Part I of this paper) has been used to solve the General Dynamic Equation in complex, non-isothermal reacting flows to predict aerosol dynamics and particle deposition rates. The numerically efficient algorithm has made it possible to solve the GDE in complex two-dimensional and three-dimensional simulations, hitherto not done due to the computational intensiveness. Simulations have been performed to elucidate the role of different process parameters on aerosol dynamics and particle deposition rates in idealized and commercial horizontal single wafer CVD reactors. Specifically, it has been demonstrated that the gas phase kinetics, particle formation, growth and deposition rates result in very complex aerosol size distributions in the reactor that cannot be captured with simplistic models that do not couple the GDE to the detailed flow field simulations. Guidelines for minimizing particle contamination in CVD reactors on the basis of the simulation results are presented.     

Proton spin–lattice and spin–spin relaxation times in isotactic polypropylene. II. Effects of stretching ratio and temperature

Proton spin–lattice, T₁, and spin–spin, T₂, relaxation times of uniaxially stretched polypropylene film were measured at 40°C using a wide line pulse spectrometer operating at 19.8 MHz. T_1l, the longer T₁, increases almost linearly with increasing stretching ratio, and T_2a, T₂ of the amorphous region, decreases gradually as the stretching ratio is increased. These results can be interpreted in terms of the increased constraints to molecular motion in the amorphous region. The fraction of the rigid protons in the sample, F_c, increases with increasing stretching ratio, while the crystallinity calculated from the density, X_d, does not change largely. The difference between F_c and X_d, therefore, increases as the stretching ratio is increased. This indicates that the physical structure of the highly stretched sample is far from the ideal two-phase model. The influence of the stretching temperature was also investigated. There are only slight increases in T_1l and in F_c for the samples stretched in a temperature range from 80°C to 150°C, whereas the considerable increase in T_2a occurs. The most notable change introduced at a high temperature stretching is the increase in the chain mobility in the amorphous region.     

Rheology of 1‐butyl‐3‐methylimidazolium chloride cellulose solutions. II. Solution character and preparation

The focus of this article of a three part series is the effects of preparation and composition on the shear rheology of cellulose in the ionic liquid 1‐butyl‐3‐methylimidazolium chloride ([Bmim]Cl). Included are the effects of three different degrees of polymerization, (i.e., average molecular weight), manual versus high shear mixing, a range of cellulose concentrations, and the effects of controlled amounts of lignin and a hemicellulose. The rheology implies that a gel phase develops at higher degrees of polymerization, higher concentration, and at lower temperatures. The first article focused primarily on shear rheology of cellulose in [Bmim]Cl with a high shear preparation technique, one degree of polymerization, a narrow range of cellulose concentrations, and temperature. The third article focuses on elongational rheology of cellulose in [Bmim]Cl. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Determination of optimal reactor system configuration for polymerization reactions. II. Effect of chain transfer,autoacceleration, and temperature profile

The effect of chaln transfer, diffusion control, and temperature on the optimal design and selection of polymerization reactors was investigated. Chain transfer to the monomer was examined and a parametric study of the corresponding rate constant was carried out. The Trommsdorff effect was included in the model by using a diffusion-controlled termination process. An optimum temperature sequence was determined for this modified model by incorporating the effect of temperature on the rate constants and on the amount and rate of heat removal. Furthermore, the concept of dividing the plug flow reactor into several constant temperature zones was considered, and the effect of “zoning” on the system performance was determined.     

Cation-Exchange Study on a Crystalline and Thermally Stable Phase of Antimony Silicate. Effect of Irradiation on Ion-Exchange Behavior and Separation of Cd(II) from Zn(II) and Mn(II) and of Mg(II) from Ba(II), Ca(II), and Sr(II)

Abstract

A systematic ion-exchange study has been performed on antimony silicate, which includes its ion-exchange capacity, elution behavior, pH titrations, and distribution coefficients of common metal ions. The K_d values for alkali metals vary with the pH of the solution and the material is found to be highly selective for Rb(I) at pH values greater than 1. On the basis of distribution studies, the separation of Cd(II) from Zn(II) and Mn(II) has been achieved. Similarly, Mg(II) has been separated from Ba(II), Ca(II), and Sr(II) to illustrate its utility. Antimony silicate is very stable both thermally and chemically and possesses reproducible ion-exchange properties; also, the effect of irradiation on the ion-exchange behavior is negligible. A tentative formula of the material has also been proposed based on chemical, infrared, and thermogravimetric analysis studies. The x-ray studies reveal that the exchanger is crystalline with a d-value of 6.09 Å.     

The effects of weathering and atmospheric pollutants on cotton fabric and cotton fabric treated with selected flame retardants. II. Spectroscopic studies

Spectroscopic studies of weathered flame retardant cotton fabrics were conducted. The weathering conditions included combined and independent exposure to xenon arc light and low concentrations of SO₂, NO₂, and O₃ gases. Multiple internal reflectance infrared analysis of weathered Pyrovatex 3805-treated fabric showed that the finish removed after 150 hr of weathering exposure had the same structure as the original finish. Interferometer spectra of Pyrovatex 3805 and THPOH-NH₃ finishes on the fabric indicated no significant changes in the structure for both finishes after exposure to the various weathering conditions.     

Theophylline-loaded pectin-based hydrogels. II. Effect of concentration of initial pectin solution,crosslinker type and cation concentration of external solution on drug release profile

A series of drug-loaded pectin hydrogels were prepared by mixing method in two ion types, Ca⁺² or Zn⁺², for wound dressing applications and their drug release performances were investigated at pH 6.4 in four different calcium ion concentrations of external solution. Pectin hydrogels were synthesized in three different concentrations of initial pectin solution and theophylline was used as a model drug. Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy were used for hydrogel characterization. Additionally, fluid handling capacity, swelling behavior, dehydration rate, dispersion characteristic, dressing pH determination, water vapor permeability, oxygen permeability, surface contact angle, flexibility, mass per unit area, and thickness were determined for selected hydrogels. One of the most valuable contributions of our study is that the concentration of initial pectin solution and calcium ion concentration of external solution are very important parameters to obtain an effective drug release. After evaluating all data, we have shown that flexible and transparent pectin-based wound dressings can be synthesized as a controlled drug release system. Zinc-containing hydrogel was antibacterial against Staphylococcus aureus and Escherichia coli but not suitable for cell migration. On the other hand, calcium-based hydrogel was nontoxic on the fibroblast cells and it had no negative effect on cell migration. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48155.     

灌溉周期对工业大麻秆部分理化性能的影响Ⅱ.灌溉周期对纤维素相对结晶度和晶胞尺寸的影响

为更好利用生物质材料,研究纤维素的相对结晶度和晶胞尺寸及其影响因素,用广角X射线衍射仪,研究了不同灌溉周期（3天浇一次水、14天浇一次水、不浇水）对工业大麻秆纤维素相对结晶度和晶胞尺寸的影响。结果表明在整个生长期中,随着生长期延长纤维素的相对结晶度呈增加趋势,晶胞尺寸呈减小趋势;不同灌溉周期对纤维素相对结晶度和晶胞尺寸影响显著（P≤0.05）;纤维素的物理结构在纤维细胞壁不同层次中是不同的。     

Effects of reactive low‐profile additives on the properties of cured unsaturated polyester resins. II. Glass‐transition temperature and mechanical properties

The effects of reactive poly(methyl methacrylate) (PMMA) and poly(vinyl acetate)‐block‐poly(methyl methacrylate) (PVAc‐b‐PMMA) as low‐profile additives (LPAs) on the glass‐transition temperature and mechanical properties of low‐shrink unsaturated polyester resin (UP) were investigated by an integrated approach of determining static phase characteristics, reaction kinetics, cured sample morphology, and property measurements. The factors that, according to Takayanagi mechanical models, control the glass‐transition temperature in each phase region of the cured samples, as identified by both the thermally stimulated currents method and dynamic mechanical analysis, and the mechanical properties are discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 867–878, 2006     

Factorial optimization of the effects of extrusion temperature profile and polymer grade on as‐spun aliphatic–aromatic copolyester fibers. II. Crystallographic order

By using factorial experimental design, a range of crystallographic orders for as‐spun linear aliphatic–aromatic copolyester fibers have been characterized with the aid of wide angle X‐ray diffraction measurements. Full‐Width Half‐Maximum of an X‐ray scattering profile (FWHM) has been quantitatively assessed as responses to polymer grades denoted by melt flow index (MFI) and to extrusion temperature zones in the extrusion equipment used to produce the as‐spun fibers. With the advantages of the factorial experimental design in the development of fiber process technology, the enhanced statistical approach specifies the direction of change of the polymer's melt flow index and extrusion temperature profile for increasing or reducing crystallographic order. The produced as‐spun aliphatic aromatic copolyester fiber is an environmentally‐friendly attractive, alternative to conventional chemical fibers for different applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011