Alkyl chain branching in ethylene–vinyl acetate copolymer

Ethylene–vinyl acetate copolymers contain two kinds of side chains: acetoxy branches originating from incorporated vinyl acetate and alkyl branches. The alkyl branching was determined by infrared analysis after converting the ethylene–vinyl acetate copolymer to a hydrocarbon polymer by three steps: hydrolysis, iodation with hydriodic acid containing red phosphorus, and reductive hydrogenation with lithium aluminum hydride. It was found that physical properties such as stiffness were dependent both on the degree of alkyl chain branching and on vinyl acetate content.     

13C-NMR study of chlorinated ethylene–vinyl acetate copolymers

¹³C-NMR has been used to analyze the microstructures of a series of experimental chlorinated ethylene–vinyl acetate copolymers (15–56% CI). Previously established line assignments for EVA copolymers and substituent effect parameters for chlorine have enabled us to tentatively assign partial structures up to five carbon atoms in length. The ¹³C-NMR analyses of a commercial vinyl chloride–vinyl acetate copolymer, a commercial vinyl chloride–vinyl acetate–ethylene terpolymer, and a commercial chlorinated polyethylene support the structural assignments. Data obtained for the experimental resins indicate that the acetate groups influence the way in which chlorine is added to the polymer chain. furthermore, the data indicate the acetate groups undergo little, if any, chlorination.     

Interaction of water in polymers: Poly(ethylene‐co‐vinyl acetate) and poly(vinyl acetate)

We studied the interaction of water in poly(ethylene‐co‐vinyl acetate) of various vinyl acetate compositions and poly(vinyl acetate), on the basis of the infrared spectrum of the water dissolved therein. The spectrum shows a very sharp and distinct band at about 3690 cm^?1 (named as A), and less‐sharp two bands around 3640 (B) and 3550 cm^?1 (C), the A band being outstanding especially at a low vinyl acetate composition. As the vinyl acetate composition increases, the A band decreases in intensity relative to the C band, whereas the B band increases contrarily. Analysis of the spectral change has elucidated that one‐bonded water (of which one OH is hydrogen‐bonded to the C?O of an ester group and the other OH is free) and two‐bonded water (each OH of which is hydrogen‐bonded to one C?O) coexist in the copolymer and that two‐bonded water increases in relative population with increasing vinyl acetate composition. Dissolved water is entirely two‐bonded in poly(vinyl acetate), in which C?O groups are densely distributed in the matrix. We proved that dissolved water in polymers is hydrogen‐bonded through one or two OH groups to the possessed functional groups but does not cluster. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 777–785, 2005     

Head-to-head vinyl chloride–vinyl acetate copolymer

Addition chlorination of cis-1,4-polybutadiene in the presence of acetic acid as a cosolvent resulted in the formation of head-to-head vinyl chloride–vinyl acetate copolymer. Chlorine analysis, IR, and NMR spectra of the chlorinated polybutadiene indicated that reaction was primarily double bond addition; there was little evidence for substitutive chlorination. Acetate was incorporated by nucleophilic participation of the acetic acid cosolvent. The extent of incorporation of the acetate group in the polymer chain was a function of the acetic acid concentration. Both the glass transition temperatures and the densities of the chloroacetylated polymers decreased as the degree of acetylation increased.     

Nuclear magnetic resonance studies on microstructure of ethylene copolymers. VI. Carbon-13 spectra of ethylene–vinyl acetate copolymers

The 22.6-MHz Fourier-transform noise-decoupled ¹³C (carbon-13) NMR spectra of several ethylene–vinyl acetate (E–VA) copolymers were obtained. We found that triad information on monomer placement can be deduced from carbonyl resonances, triad and pentad information can be deduced from methine carbon resonances, and triad information is available from the methylene carbon resonances. The random comonomer distributions in E–VA polymerizations were demonstrated up to pentad placements. In addition, the use of model-compound data in the analysis of copolymer spectra was shown.     

A comparative study of UV aging 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 UV aging 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 by means of UV light with a wavelength in the vicinity of 259 nm, in air, up to 400 hr. Sol‐gel analyses 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 aging. Dynamic and isothermal thermogravimetry 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 UV irradiation. EVA/CB, however, becomes a gel to a smaller extent, comparatively, under the same conditions. As a result of FT‐IR measurements, some oxidation products such as ketone, lactone and vinyl species were observed through UV ageing of EVA and EVA/CB. Thermal analysis experiments exhibited that the thermal stabilities of EVA and EVA/CB decreased, to a similar extent through UV aging. Copyright © 2004 John Wiley & Sons, Ltd.     

Assignment of finely resolved 13C NMR spectra of poly(vinyl acetate)

¹³C NMR spectra of two poly(vinyl acetate)s (PVAC) with different tacticities (r‐diad, 0.54 and 0.57) were measured, and their peak intensities were compared with the calculated ones. The methine carbon signals were assigned with pentads in the order of mmmm, mmmr + rmmr, rmrr + mmrr, rrrr, mmrm, rmrm, mrrr, mrrm from low field. The methylene carbon signals were assigned with tetrads (partly with hexads) as rmr, rrr(mrrrm, mrrrr, rrrrr), mmr + mrr, mrm and mmm from low field. Some assignments are different from those previously reported. The methyl carbon signals showed splittings which were partly assigned.     

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.     

Silica aerogel–poly(ethylene‐co‐vinyl acetate) composite for transparent heat retention films

Poly(ethylene‐co‐vinyl acetate) (EVA) plastic films are widely used for solar coverings including photovoltaic modules and commercial greenhouse films, but are poor at controlling heat flow. In this work, silica aerogel (SA) nanogels were examined for preparing transparent heat retention EVA films that block far infrared spectra radiation to maintain heat, without compromising the optical performance of the films. SA nanogels were melt‐mixed using a mini twin‐screw extruder with EVA pellets to form SA/EVA composite, which were pressed into thin films with controlled thickness. The composite films were characterized in terms of optical properties using a variety of analytical methods including FTIR, UV–Vis spectroscopy, electron, confocal, and atomic force microscopy. Both thermicity and thermal conductivity of commercial and experimental SA/EVA films were measured. The results demonstrated that the SA/EVA films gave improved infrared retention compared to commercial thermal plastic films without compromising visible light transmission, showing the potential for this approach in next generation heat retention films. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 927–935     

Equation of state of copolymer melts: The poly(vinyl acetate)–polyethylene pair

The pressure—volume—temperature properties of a series of copolymers ranging in content from 18 to 40 wt % of vinyl acetate, and up to a maximum pressure of 1800 kg/cm² are studied. The results for the melt state can be satisfactorily fitted by the scaled equation of state, developed previously and applied to single-component systems and to mixtures. The dependence of the scaling parameters for the copolymers on composition deviates from that expected for a mixture, where volumes at elevated pressures can be predicted without further recourse to experiment. These differences are discussed in terms of the sequential structure of the copolymer chain and its series of interfaces between the two species.     

Solid‐state NMR characterizations on phase structures and molecular dynamics of poly(ethylene‐co‐vinyl acetate)

Solid‐state nuclear magnetic resonance spectroscopy and relaxation measurements, together with DSC, have been used to elucidate the structures and molecular dynamics in poly(ethylene‐co‐vinyl acetate) (EVA). It has been found that besides immobile orthorhombic and monoclinic crystalline phases, the third mobile crystalline phase (possibly the phase) of a considerable amount (36% of total crystalline phases) appears in the EVA samples, which forms during room‐temperature aging as a result of the secondary crystallization and melts at temperature somewhat higher than room temperature. Such a mobile crystalline phase has not only the well‐defined chemical shift of its own, but also has different molecular mobility from the orthorhombic phase. The mobile crystalline phase is characterized by the rapid relaxation of the longitudinal magnetization, which is caused by conventional spin‐lattice relaxation, while the slow relaxation of the longitudinal magnetization occurring in the orthorhombic phase is originated from the chain diffusion. In addition, the amorphous phase also contains two components: an interfacial amorphous phase and a melt‐like amorphous phase. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2864–2879, 2006     

Compatibility of poly(ethylene oxide)–poly(vinyl acetate) blends

The compatibility of poly(ethylene oxide)–poly(vinyl acetate) (PEO-PVA) blends was examined at five compositions covering the complete range. Samples were prepared by coprecipitation and solution casting. Dynamic mechanical properties were studied at 110 Hz between ?120 and 65°C for dry, quenched, and annealed samples. The study also included tensile testing at 25°C, examination of blend morphology, and DSC measurements at elevated temperatures. Optical microscopy revealed that crystallization of PEO proceeds essentially unhindered at up to 25% poly(vinyl acetate) content by weight. Higher levels of this component drastically reduce spherulite size, and at the highest PVA compositions there was no evidence of crystallization. Thermomechanical spectra of quenched and annealed samples indicate limited mixing of the two components except for the higher (>75%) PVA compositions. Tensile properties show a mutual reinforcement at 10-25% PVA content due to possible polymer segment association. The melting-point depression of PEO is significant above 25% PVA and has been attributed to morphological changes of the PEO crystalline phase.     

Structure and property relationships in ethylene–vinyl acetate copolymers

The effects of vinyl acetate content on crystallinity of ethylene–vinyl acetate (E/VA) copolymers were investigated by x-ray diffraction and differential thermal analysis (DTA). The values of these parameters obtained from DTA were found to agree quantitatively with data calculated from x-ray, probability equations, and copolymer theory. The melting points of the crystalline copolymers, and the molar amounts of vinyl acetate to produce a completely amorphous rubber corresponds exactly to that predicted by the Flory theory. The random character expected in E/VA copolymers is thereby confirmed. The physical properties of E/VA copolymers of all ranges of compositions and crystallinity were determined. Depending directly upon vinyl acetate content, the copolymers changed progressively from highly crystalline polyethylene to semicrystalline polyethylene, a completely amorphous rubber, a soft plastic with a glass transition near room temperature. Properties which were correlated with copolymer composition include: crystallinity, melting point, density, modulus, tensile strength, glass transition, and solubility. Finally, the effect on crystallinity and physical properties of replacing the acetoxy group in E/VA with the smaller, highly polar hydroxyl group (ethylene—vinyl alcohol copolymer) was also investigated.     

Carbon-13 nuclear magnetic resonance of ethylene–propylene copolymer and the determination of sequence distribution of monomeric units

The ¹³C-NMR spectra of ethylene–propylene copolymers and their model compounds were measured at 15.1 MHz. Assignments of the signals were carried out by using the equation of Grant and Paul and also by comparing the spectra with those of squalane, hydrogenated natural rubber, polyethylene, and atactic polypropylene. The accuracy and the precision of intensity measurements, that is, the deviation from the theoretical values and the scatter of the measurements, respectively, were checked for the spectra of squalane and hydrogenated natural rubber and were shown to be at most 12% for each of the signals. On the basis of these results the mole fractions of the four types of the dyad sequences, that is, the propylene–propylene (head-to-tail and head-to-head), the ethylene–propylene, and the ethylene–ethylene sequences, were determined together with the average sequence lengths of both monomer units.     

Sorption and diffusion of normal alkanes through poly(ethylene‐co‐vinyl acetate) membranes

The transport behavior of uncrosslinked and crosslinked poly(ethylene‐co‐vinyl acetate) membranes has been investigated using normal alkanes as probe molecules, in the temperature range of 30–60 °C. Benzoyl peroxide was used for crosslinking the matrix. It has been observed that, a critical concentration of crosslinker is necessary for maximum solvent uptake, followed by a decrease at higher concentration. The effect of free volume on liquid transport was investigated by positron annihilation lifetime spectroscopy. The mechanism of transport has been found to deviate from the regular Fickian behavior. The dependence of the transport coefficients on crosslink density, nature of penetrants, and temperature was studied. The polymer–solvent interaction parameter, enthalpy, and entropy of sorption have also been estimated from the transport data. The affine and phantom models for chemical crosslinks were used to predict the nature of crosslinks. Finally, the experimental sorption data were compared with theoretical predictions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2470–2480, 2007     

Radiation-induced oxidation of polyethylene,ethylene–butene copolymer,and ethylene–propylene copolymer

Oxygen consumption and yield of oxidation products during γ-irradiation were studied on five types of polyethylene (PE), ethylene–butene copolymer (EB), and ethylene–propylene copolymer (EPR) using gas chromatography, mass spectrography, and high-resolution NMR. Samples were irradiated in oxygen under pressure from 0 to 500 torr by ⁶⁰Co γ-rays up to 20 Mrad at 22–25°C. In enough oxygen, oxygen consumption and yield of oxidation products are independent of oxygen pressure for low-density PE, EB, and EPR. The G values of oxygen consumption were 14–18.4 for PE, 11.6 for EB at 1 × 10⁶ rad/h, and 8.3 for EPR at 2 × 10⁵ rad/h. The oxidation products determined were carboxylic acid (? CH₂? CO? OH), H₂O, CO₂, and CO. The oxygen consumption and oxidation products for PE were found to increase with increasing crystallinity.     

Relationship between structures of phosphorus compounds and flame retardancies of the mixtures with acrylonitrile–butadiene–styrene and ethylene–vinyl acetate copolymer

Various analogos of phosphonic acid, phosphinic acid, and CH₃? P(O) group containing organo‐phosphorus compounds were synthesized as model compounds to investigate the effects of P content and the structure of flame retardant (FR) on their fire retarding performances of acrylonitrile–butadiene–styrene (ABS) and ethylene–vinyl acetate (EVA) copolymer. The success of synthesis was confirmed by ¹H‐ and ³¹P‐NMR. The flame retarding efficiencies were evaluated by a UL‐94 vertical test method. Thermogravimetric analysis results reveal that all the mixtures of FRs with ABS or EVA exhibit no or very little charred residues at 600°C under inert atmosphere condition, indicating that all FRs work in the gas phase rather than in the condensed phase for both ABS and EVA. The fire retarding efficiency of FR depends not only on the P content in FR but also on the nature of its structure. UL‐94 results show that P FRs with ? CH₃ group attached to the P atom exhibits the best fire retarding performance on both ABS and EVA. It was found that at least 4 wt% P in the formulation is required to show self‐extinguishing ability for both ABS and EVA when P FRs having ? CH₃ group are employed. The fire retarding efficiency of P FRs with different attached group is in order of: ? CH₃ > ? C₆H₅ > ? OH > ? H. Copyright © 2009 John Wiley & Sons, Ltd.     

Toughening of poly(lactic acid) by ethylene-co-vinyl acetate copolymer with different vinyl acetate contents

The well-known bio-based and biocompostable poly(lactic acid), PLA, suffers from brittleness and a low heat distortion temperature. In this paper, we address a possible route to make PLA tough(er) by blending with ethylene-co-vinyl acetate (EVA) with different vinyl acetate contents. The compatibility and phase morphology of the PLA/EVA blends was controlled by the ratio of vinyl acetate and ethylene in the random copolymers. Tough PLA/EVA blends with increased impact toughness, up to a factor of 30, were obtained with a maximum toughness at a vinyl acetate content of approximately 50 wt.%. The local deformation mechanism was well studied by TEM, SAXS and SEM. It revealed that internal rubber cavitation in combination with matrix yielding is the dominant toughening mechanism for the PLA/EVA blends under both impact and tensile testing conditions.     

An NMR investigation of compatibility in blends of poly vinyl chloride and ethylene-vinyl acetate copolymer

A series of technical composite suspension polymerized poly vinyl chloride products with additions of ethylene-vinyl acetate copolymer (Levapren 450M. 45 wt % VAc) have been investigated with NMR. Partial compatibility is found in these samples, and the phase conditions have been shown to be very much dependent upon the methods of forming of the materials. Complete phase separation is observed after prolonged heating.