Swelling measurement of some ethylene copolymers crosslinked by dicumyl peroxide

Swelling equilibrium of crosslinked ethylene copolymers prepared by the curing of ethylene–vinyl acetate (EVA), ethylene–ethyl acrylate (EEA), and ethylene–acrylic acid (EAA) with dicumyl peroxide (DCP), has been measured in toluene at 23°C. The stress–strain behavior of the swollen EVA and EEA networks was in accord with that predicted from the statistical rubber elasticity theory, while that of the swollen EAA network was divergent. The concentration dependence of the polymer–solvent interaction parameter for the EAA network–toluene system was observed to be highest, while that for the EVA network–toluene system remained nearly zero. The order of the reactivity of pendant groups in the copolymers by radicals from DCP was estimated to be carboxyl > acetyloxy > ethoxycarbonyl group.     

Sorption phenomena of organic solvents in polymers: Part I

In this work we use the vapor-sorption equilibrium data to show the degree of solvent upturn in each solvent-polymer system. For this purpose, 23 isothermal data sets for four polymer + solvent binaries, one block copolymer + solvent binary and for the corresponding polymer pairs have been used in the temperature range of 25-70 °C. Solvents studied are benzene, carbon tetrachloride, chloroform and pentane. Homopolymers studied are polyisobutylene, poly(ε-caprolactone), poly(ethylene oxide), n-heptadecane, polystyrene, poly(vinyl chloride), poly(vinyl methyl ether), and n-tetracosane.According to these data sets, solvent weight fraction in the polymer is plotted against solvent-vapor activity that is calculated assuming an ideal gas phase of pure solvent vapor neglecting the vapor pressure of the polymer. We use the Flory-Huggins theory to obtain dimensionless interaction parameter, χ. Also the Zimm-Lundberg clustering theory and non-ideality thermodynamic factor, Γ are used to interpret the equilibrium data.     

高聚物双流体配位模型状态方程的简化

对高聚物以流体配位模型状态方程进行了简化，忽略了其中的Ｑ项，以简化的状态方程对４２个纯高聚物（聚丙烯、聚苯乙烯、聚异丁烯和聚丁烯－１），２种纯溶剂（苯，环己烷）和２个高聚物／溶剂混合系（聚异丁烯／苯和聚异丁烯／环己烷）进行关联，结果表明，简化的状态方程与原方程同样具有很好的关联精度和温度适用性。     

Correlation between excess adsorption data measured for solvent mixture/adsorbent systems and RM values obtained for different solutes chromatographed in binary mobile phases

This paper concerns the application of excess adsorption isotherms, measured for solvent mixture/adsorbent systems, to the characterization of TLC data. For this purpose the excess adsorption isotherms for three liquid mixtures: cyclohexane/ benzene, benzene/acetone, and carbon tetrachloride/ethyl acetate on silica gel at 20°C have been measured. These mixtures have been used as binary mobile phases in TLC measurements. It has been shown for a given solute in binary mobile phase that the quantity R_M is a simple function of the excess adsorption. Parameters of this function have been used to characterize chromatographic systems with binary mobile phases.     

Effect of the liquid–liquid phase separation on the crystallization behavior of a poly(ethylene‐ran‐vinyl acetate) and paraffin wax blend

The effect of liquid–liquid phase separation (LLPS) on the crystallization behavior of poly(ethylene‐ran‐vinyl acetate) with a vinyl acetate content of 9.5 wt % (EVA‐H) in the critical composition of a 35/65 (wt/wt) EVA‐H/paraffin wax blend was investigated by small‐angle light and X‐ray scattering methods and rheometry. This blend exhibited an upper critical solution temperature (UCST) of 98°C, and an LLPS was observed between the UCST and the melting point of 88°C for the EVA‐H in the blend. As the duration time in the LLPS region increased before crystallization at 65°C, both the spherulite size and the crystallization rate of the EVA‐H increased, but the degree of the lamellar ordering in the spherulite and the degree of crystallinity of the EVA‐H in the blend decreased. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 707–715, 2000     

Long branching in poly(vinyl acetate) and poly(vinyl alcohol). II. Polymerization of vinyl acetate in the presence of crosslinked poly(vinyl alcohol)

It is a common view that poly(vinyl acetate) has many branches at the acetyl side group, but that the corresponding poly(vinyl alcohol) has little branching. In order to study the branching in poly(vinyl acetate) and poly(vinyl alcohol) which is formed by chain transfer to polymer, the polymerization of ¹⁴C-labeled vinyl acetate in the presence of crosslinked poly(vinyl acetate), which was able to be decrosslinked to give soluble polymers, was investigated at 60°C and 0°C. This system made it possible to separate as well as to distinguish the graft polymer from the newly polymerized homopolymer. Furthermore, the degree of grafting onto the acetoxymethyl group and onto the main chain were estimated. It became clear that, in the polymerization of vinyl acetate, chain transfer to the polymer main chain takes place about 2.4 times as frequently at 60°C as that to the acetoxy group and about 4.8 times as frequently at 0°C.     

Effect of the liquid–liquid phase separation on the crystallization behavior and mechanical properties of poly(ethylene‐ran‐vinyl acetate) and paraffin wax blend

The effect of liquid–liquid phase‐separation (LLPS) on the crystallization behavior and mechanical properties of poly(ethylene‐ran‐vinyl acetate) (EVA) with various amounts of vinyl acetate and paraffin wax blend was investigated. The blend of EVA‐H (9.5% vinyl acetate) and the wax became homogeneous at temperatures greater than its upper critical solution temperature (UCST) (98°C), and an LLPS was observed between UCST and the melting point of 88°C for EVA‐H in the blend. The existence of the LLPS is attributed to the relatively large amount of the hydrophilic component of vinyl acetate in EVA, although the molecular weight of the wax was just 560. However, LLPS did not occur for the EVA/wax blend when the content of vinyl acetate in EVA was less than 3%. This behavior was explained by using the Flory–Huggins lattice model with an effective interaction parameter. The degree of crystallinity of EVA‐H in the EVA‐H/wax blend, judged from a melting endothermic peak in differential scanning calorimeter (DSC) thermograms obtained during heating runs, decreased with increasing duration time in the LLPS region. The flexural modulus of the EVA/wax blend became maximum at certain blend composition (about 30 ∼ 40 wt % EVA depending upon the amount of vinyl acetate). This behavior can be explained by the fact that this blend composition has the largest relative degree of crystallinity of EVA measured by DSC and wide‐angle X‐ray scattering method. We found that the flexural modulus of the binder itself is directly related to that of a feedstock consisting of larger amounts of metal powder and the binder, which can help someone to develop a suitable binder system for a powder injection molding process. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1991–2005, 1999     

Effects of orientation on dynamic shear behavior of some amorphous polymers from 4.2° to 300°K

The dynamic shear behavior of four highly amorphous polymers in the unstretched and stretched states (draw ratios 3:1 to 6:1) was investigated with a torsion pendulum at temperatures from 4.2°K to 180–300°K and frequencies from 0.4 to 3.2 cps. The polymers studied were polystyrene, poly(vinyl acetate), poly(vinyl propionate), and poly(isobutyl vinyl ether). Previously unreported loss maxima were found at 48°K (1.5 cps) and 149°K (1.3 cps) for poly(vinyl proplonate), at 10°K (1.0 cps) for poly(vinyl acetate) and at 9°K (1.6 cps) for poly(isobutyl vinyl ether). Uniaxial orientation increased the shear storage modulus G, measured with the torsion axis parallel to the stretch direction and caused changes in the loss peaks which depended on the polymer material studied.     

Sorption phenomena of organic solvents in polymers: Part II

In this work we use the vapor-sorption equilibrium data to show the degree of solvent upturn in each solvent-polymer system. For this purpose, sixty-one isothermal data sets for forty copolymer + solvent binaries and for fourteen of their parent homopolymer + solvent binaries have been used in the temperature range of 23.5-80 °C. Solvents studied are acetone, acetonitrile, 1-butanol, 1,2-dichloroethane, chloroform, cyclohexane, hexane, methanol, octane, pentane, and toluene. Copolymers studied are poly(acrylonitrile-co-butadiene), poly(styrene-co-acrylonitrile), poly(styrene-co-butadiene), poly(vinyl acetate-co-ethylene), and poly(vinyl acetate-co-vinyl chloride). All copolymers are random copolymers. Some homopolymers are also studied: polyacrylonitrile, poly(cis-1,4-butadiene), poly(ethylene oxide), polystyrene and poly(vinyl acetate).According to these data sets, solvent weight fraction in the polymer is plotted against solvent vapor activity that is calculated assuming an ideal gas phase of pure solvent vapor neglecting the vapor pressure of the polymer. We use the Flory-Huggins theory to obtain dimensionless interaction parameter, χ. Also the Zimm-Lundberg clustering theory and non-ideality thermodynamic factor, Γ are used to interpret the equilibrium data.     

Molecular architecture and physicochemical properties of some vinyl alcohol-vinyl acetate copolymers

Two series of vinyl alcohol-vinyl acetate copolymers were prepared by homogeneous and heterogeneous acetylation of the same precursor poly(vinyl alcohol). Their intramolecular monomer distributions were analyzed by IR spectrometry, calorimetry, and differential thermal analysis. The results show a more blocky distribution for the heterogeneously prepared copolymers. The properties of these (co)polymers in dilute aqueous solution were determined by means of viscometry. Whereas the copolymer-solvent interaction parameter of the homogeneously acetylated, random copolymers hardly varied with acetate content, a definite minimum was found for the blocky copolymers at about 7 mole% vinyl acetate. These findings were attributed to the incompatibility of dissimilar sequences, which sharply decreases with decreasing vinyl acetate sequence length. Up to about 17 mole% vinyl acetate content, the solvent quality for the copolymers is at least as good as for poly(vinyl alcohol). In addition, the dilute solution properties of the samples were established in water saturated with 1-butanol. For copolymers with up to about 17 mole% vinyl acetate, at 25°C this mixture is a better solvent than water. The highest increase in solvent quality was found for the homopolymer, whereas the increase diminished with acetate content, irrespective of the intramolecular vinyl acetate distribution. These findings are explained in terms of preferential adsorption of 1-butanol onto the (co)polymer backbone due to hydrophobic interactions and prevention of this process by the bulky acetate groups.     

Solubility in Binary Solvent Systems: Comparison of Predictive Equations Derived from the NIBS Model

Abstract

Experimental solubilities are reported for pyrene in binary solvent mixtures containing benzene with n-hexane, cyclohexane, n-heptane, n-octane, cyclooctane and isooctane at 26°C. Results of these measurements, combined with published pyrene and biphenyl solubilities, are used to test predictive expressions derived from the Nearly Ideal Binary Solvent (NIBS) model. The most successful equation in terms of goodness of fit involved a surface fraction average of the excess Gibbs free energy relative to Raoult's law and predicted the experimental solubilities in 17 systems with an average deviation of 2.3% and a maximum deviation of 8.9%. Two expressions approximating weighting factors with molar volumes provided accurate predictions in many systems studied but failed in their ability to predict pyrene solubilities in solvent mixtures containing benzene.     

Transport of steroids in poly(etherurethane) and poly(ethylene vinyl acetate) membranes

The permeability of polymer membranes to steroids was studied as a function of both permeant and membrane properties, using nine steroids and copolymer membranes prepared from poly(etherurethanes) and poly(ethylene vinyl acetates). Permeabilities, diffusion coefficients, and solubilities of the steroids in the membranes were determined in sorption—desorption and permeation experiments. Steroids with higher melting points permeated more slowly. This relationship originated from the lower diffusivities and solubilities of higher-melting steroids in the polymer phase; the effect of solubility changes was predominant. Reducing the polyether content of poly(etherurethane)merebranes ten-fold decreased their permeability to androstenedione by four orders of magnitude (from 10^?10 to 10^?14 g steroid/cm-sec at 37°C), due largely to diffusivity decreases. In contrast, reducing the vinyl acetate content of poly(ethylene vinyl acetate) membranes from 40% to 9% produced only modest changes in bath steroid solubility and diffusion coefficient. The permeability to androstenedione within this series of copolymer membranes ranged between 10^?11 and 10^?12 g steroid/cm-sec at 37°C.     

Mechanistic study of thermal behavior of poly(vinyl acetate) blended with aluminum tribromide: an investigation aided by IR and Py–GC–MS techniques

Thermal behavior of poly(vinyl acetate) in the presence of aluminum tribromide (thin film cast from common solvent) is studied by thermoanalytical, IR, and Py–GC–MS techniques. Pyrolytical characterization reveals two-step degradation for neat polymer whereas blends pyrolyze in three stages. The detailed examination of blends was performed to identify the compounds formed. Moreover, the mixed film sample was heated at 200, 300, and 400 °C and residues were analyzed by IR spectroscopy in order to follow the progress of degradation. Acetic acid does not appear as major product of the blends’ degradation due to the formation of acetyl bromide, development of polyene backbone at high temperatures with intact acetate units, conversion of acetate to formate under the influence of additive, etc. The effective flame retardance of additive for polymer is noteworthy. Various schemes have been outlined to show the probable degradation mechanism.     

Polymerization of 2,2,2-trifluoroethyl vinyl ether

The polymerization of 2,2,2-trifluoroethyl vinyl ether by six different catalyst systems was examined. Low-temperature studies (?78°C) with boron trifluoride etherate catalyst in hydrocarbon and chlorinated solvents slowly yielded low molecular weight polymers which were amorphous and noncrystallizable upon cold drawing. Under similar conditions, polymerizations with boron trifluoride gas were spontaneous, quantitative, and gave relatively high molecular weight, form-stable, amorphous polymer. Heterogeneous polymerizations with chromium trioxide crystals in toluene at 68°C and bulk reactions with ethylmagnesium bromide–carbon tetrachloride catalyst at 40°C failed to produce polymer. Room temperature runs with triisobutylaluminum–titanium tetrachloride catalyst gave amorphous, tacky material. Aluminum hexahydrosulfate heptahydrate (AHS) initiated polymerizations conducted at 25 and 60°C gave low yields of mixtures of amorphous and crystalline polymers, the ratio depending upon the polymerization solvent employed. The infrared spectra and x-ray diffraction intensity curves of crystalline and amorphous poly(trifluoroethyl vinyl ether) are reported and compared herein for the first time.     

Radiation-Induced Degradation of a Series of Poly(vinyl Ethers)

The degradative effects of γ-radiation on diethyl ether solutions of poly(alkyl vinyl ethers) under a variety of conditions were studied by polymer molecular weight measurements. Poly(methyl vinyl ether) (PMVE), poly(ethyl vinyl ether) (PEVE), poly(isopropyl vinyl ether) (PIPVE), and poly(isobutyl vinyl ether) (PIBVE) exhibited similar degradative behavior, with G_(SC) values between 0.3 and 0.9 scissions/100 eV at 0°C. Chemically polymerized and radiation-polymerized PEVE samples gave comparable results. Chain degradation was much more pronounced for samples of poly(tert-butyl vinyl ether) (PTBVE) which yielded a G_(SC) value of 3.6 at 0°C. Degradation experiments conducted on PEVE in air resulted in significantly higher rates of scission: G_(SC) = 5.6 scissions/100 eV at 0°C. Chain scission was not measurably influenced by changing the solvent from diethyl ether to di-isopropyl ether. Increased polymer concentration was found to reduce the rate of polymer degradation.     

ASSOCIATION OF ETHYLENE—VINYL ACETATE COPOLYMER IN DILUTE SOLUTIONS Ⅲ. CRITICAL ASSOCIATION CONCENTRATION*

Association behavior of ethylene vinyl acetate (EVA) copolymer in foursolvents 1, 2-dichloroethane (DCE), cyclohexane (CYH), xylene (XYL) and chloroform(CF) has been investigated by dilute solution viscometry The critical association concen-tration (C_A) was determined at which the incipient decrease in slope of the η_(sp)/C～ Ccurve in solutions at the dilute regime. Our results showed that whether the CA couldexist depends on solvent property. The values of CA in DCE increase with increasing, oftemperature and vinyl acetate (VA) content in EVA and decreasing of molecular weight ofEVA.     

A comparative study of thermal ageing characteristics of poly(ethylene‐co‐vinyl acetate) and poly(ethylene‐co‐vinyl acetate)/carbon black mixture

In this comparative study, the effect of carbon black (CB) on the thermal ageing characteristics of poly(ethylene‐co‐vinyl acetate) (EVA) was investigated. EVA, containing 13% vinyl acetate (VA), and poly(ethylene‐co‐vinyl acetate)/carbon black mixture (EVA/CB) containing 13% VA and 1% CB were aged at 85°C in air up to 30 weeks. Sol‐gel analysis experiments were made to determine the percentage gelation of both virgin and aged samples. FT‐IR measurements were performed to follow the chemical changes which took place in the samples during ageing. Dynamic and isothermal thermogravimetric studies were performed for determination of the thermal stabilities of virgin and aged samples. Sol‐gel analysis results showed that EVA itself has a tendency to form a gel under thermal treatment, whereas EVA/CB never becomes a gel when being thermally aged under the same conditions. As a result of FT‐IR measurements, some oxidation products such as ketone, lactone and vinyl species were observed through thermal ageing of EVA. It is also clear that these kind of oxidation products did not appear to a considerable extent in EVA/CB. Thermal analysis experiments exhibit that thermal stability of EVA decreased through thermal ageing; whereas that of EVA/CB remained almost unchanged. Copyright © 2004 John Wiley & Sons, Ltd.     

Correlation of infinite dilution activity coefficients of solvents in polymer solutions using connectivity indices

In this work, correlations for the estimation of the infinite dilution activity coefficients of non-polar solvents in polystyrene (PS), poly(vinyl acetate) (PVAc), poly(n-butyl methacrylate) (PBMA), poly(dimethyl siloxane), poly(methyl methacrylate) (PMMA), poly(ethylene oxide) (PEO), poly(vinyl chloride) (PVC), polyisobutylene and polyethylene (PE), and that of polar solvents in PS, PVAc, PBMA, PMMA, PEO, PVC and PE are proposed. A total of 205 polymer/non-polar solvent systems with 1708 data points, and 118 polymer/polar solvent systems with 695 data points were used to develop the correlations. The overall average errors were 9.6% and 11.3%, respectively, significantly lower than other predictive models. Since the new correlations require only the connectivity indices of the solvents in the calculations, and the connectivity indices can be calculated easily once the molecular structure of the substance in question is known, they are easy to apply, and are useful for process design and development.     

Flow rates of polymer solutions through porous disks as a function of solute. II. Thickness and structure of adsorbed polymer films

The thickness of films of poly(methyl methacrylate) (PMMA), poly(vinyl acetate) (PVAc), and polystyrene (PS) adsorbed on Pyrex glass was studied by measuring the flow rates of polymer solutions and the corresponding pure solvents through sintered filter disks. Adsorption isotherms were in agreement with those reported by other workers and showed saturation adsorption equivalent to 2–8 condensed monolayers of monomer units. Film thicknesses were of the order of magnitude of the free coil diameters in solution and were directly proportional to the intrinsic viscosity of the polymer, except for PS in benzene where the thicknesses leveled off as molecular weight increased. It was concluded that polymers adsorb from solution in monolayers of compressed or interpenetrating coils; that below some critical molecular weight which varies with polymer and solvent, a much larger fraction of the segments lies directly in the interface; that adsorbed films may consist of a dense layer immediately adjacent to the surface and a deep layer of loops extending into the solvent; and that it is the segment—solvent interaction rather than the segment—surface interaction which dominates the conformation of the adsorbed chain.     

Living cationic polymerization of vinyl ethers with a naphthyl group: Decisive effect of the substituted position on naphthalene ring

Living cationic polymerization of a vinyl ether with a naphthyl group [2‐(2‐naphthoxy)ethyl vinyl ether, βNpOVE] was achieved using base‐assisting initiating systems with a Lewis acid. The Et_1.5AlCl_1.5/1,4‐dioxane or ethyl acetate system induced the living cationic polymerization of βNpOVE in toluene at 0 °C. The living nature of this reaction was confirmed by a monomer addition experiment, followed by ¹H NMR and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) analyses. In contrast, the polymerization of αNpOVE was not fully controlled; under similar conditions, it produced polymers with broad molecular weight distributions. The ¹H NMR and MALDI‐TOF‐MS spectra of the resultant poly(αNpOVE) revealed that the products had undesirable structures derived from Friedel–Crafts alkylation. The higher reactivity of αNpOVE in electrophilic substitution reactions, such as the Friedel–Crafts reaction, was attributable to the greater electron density of the naphthyl ring, which was calculated based on frontier orbital theory. The naphthyl groups significantly affected the properties of the resultant polymer. For example, the glass transition temperatures (T_g) of poly(NpOVE)s are higher by approximately 40 °C than that of poly(2‐phenoxyethyl vinyl ether). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012