Crystallinity of ethylene–vinyl acetate copolymers

Kamath, Pandurang M.; Wakefield, Robert W.

doi:10.1002/app.1965.070090919

Cited by 37 publications

(13 citation statements)

References 1 publication

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“…The EVA of lower VA content is similar to polyethylene, which has adequate ability to crystallize. As the VA content increases, the pendent acetoxy group prevents adjacent polyethylene chains to form crystal lattice, which results in lower levels of crystallinity …”

Section: Resultsmentioning

confidence: 99%

Effect of vinyl acetate content on the photovoltaic‐encapsulation performance of ethylene vinyl acetate under accelerated ultra‐violet aging

Sharma

Desai

Singh

et al. 2019

J of Applied Polymer Sci

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The vinyl acetate (VA) content in ethylene vinyl acetate (EVA) can significantly affect its performance as an encapsulant in photovoltaic modules under field conditions. EVA films of varying VA content (18, 24, 33, and 40%) have been prepared using twin screw extruder with the necessary additives and subsequently cured at 150 C. All the EVA films have been subjected to UV radiation at a wavelength of 340 nm for 1000 and 2000 h to simulate accelerated field aging. The effects of accelerated aging on the gel content, mechanical properties, transmittance, Fourier transform infra-red (FTIR) spectra, thermal stability, degree of crystallinity, and yellowness have been studied. The observations made in this study of UV aging up to 2000 h suggests that the optimum range of VA content in EVA should be between 18 and 33% by weight. VA content beyond 40% degrades almost all properties needed for an encapsulate material after aging of only 2000 h. VA content of around 18% is the most stable under UV aging conditions but has a slightly lower value of transmittance for the unaged sample although the difference in transmittance between different specimens decreases with UV aging.

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Section: Resultsmentioning

confidence: 99%

Effect of vinyl acetate content on the photovoltaic‐encapsulation performance of ethylene vinyl acetate under accelerated ultra‐violet aging

Sharma

Desai

Singh

et al. 2019

J of Applied Polymer Sci

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“…This effect could account for the consistency in T g s observed for bulk PEVAc copolymers with small vinyl acetate contents. 33,35,36 The PEVAc copolymer is expected to be totally amorphous when it contains over 45% vinyl acetate, 33,43 which explains the significant increase in T g for PEVAc (70% VAc) compared with the other PEVAc copolymers. The differential conformational mobility of the amorphous polymer chains with different proximity to the ethylene crystallites resulted in broad glass transitions for the copolymers containing small amount of vinyl acetate.…”

Section: Discussionmentioning

confidence: 99%

Thermal analysis and FT‐IR studies of adsorbed poly(ethylene‐stat‐vinyl acetate) on silica

Maddumaarachchi

Blum

2014

J Polym Sci B Polym Phys

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Adsorbed poly(ethylene‐stat‐vinyl acetate) (PEVAc) on fumed silica was studied using temperature‐modulated differential scanning calorimetry (TMDSC) and FT‐IR spectroscopy. The properties of the copolymers were compared with poly(vinyl acetate) (PVAc) and low density polyethylene (LDPE) as references. TMDSC analysis of the copolymer‐silica samples in the glass transition region was complicated for the copolymers because of the ethylene crystallinity. Nevertheless, examination of the glass transition region for small adsorbed amounts of these copolymers indicated the presence of tightly‐ and loosely‐bound polymer segments, similar to other polymers which have an attraction to silica. Compared with bulk polymers with the same composition, the tightly‐bound polymers showed an increased glass transition temperature (Tg) and a loosely‐bound fraction with a lower Tg than bulk. FT‐IR spectra of the surface copolymers indicated that the fraction of bound carbonyls (p) increased as the fraction of vinyl acetate in the copolymers decreased, consistent with the notion that the carbonyls from vinyl acetate preferentially find their way to the silica surface. Spectra from samples with different adsorbed amounts of polymer were used to obtain the amount of bound polymer (Mb) and the ratio of molar absorption coefficients of bound carbonyls to free carbonyls (X). The copolymers had very large p values (up to 0.8) at small adsorbed amounts and dependent on the composition of the polymer. However, an analysis of the bound fractions, based on only the vinyl acetate groups, superimposed the data, suggesting that the ethylene units simply dilute the vinyl acetate groups in the surface polymer. The sample with the smallest fraction of vinyl acetate did not show this behavior and may be considered to be “carbonyl poor.” © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 727–736

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“…Its properties are easily variable by the adjustment of the comonomer ratio. When the VAc content is low, the copolymer is more akin to polyethylene and has enough ability to crystal, but for high VAc content the pendent acetoxy is excessive enough and prevents adjacent polyethylene chains packing into the crystal lattice [2], then totally amorphous and rubber-like EVA is expected when the VAc content is more than 43% by weight as indicated by Kamath and Wakefield [3]. It should be noticed that Varga and his coworkers revealed that the crystallization and melting characteristics of PE are very sensitive to the VAc content [4].…”

Section: Introductionmentioning

confidence: 98%

Non-isothermal crystallization and melting of ethylene-vinyl acetate copolymers with different vinyl acetate contents

Shi¹,

Zhang

Jin³

et al. 2008

Express Polym. Lett.

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Abstract. Non-isothermal crystallization and subsequent melting of three grades of ethylene-vinyl acetate copolymer were investigated by differential scanning calorimetry (DSC) technique. The DSC crystallization curves show that vinyl acetate (VAc) content has the same effect on the onset, peak and final crystallization temperatures, and these copolymers have almost the same spacing of thermal windows under identical crystallization condition. Subsequent melting DSC results suggest that EVA14 (14 wt% VAc) has the narrowest distribution of lamellar thickness and the most perfect crystals. Though the instantaneous nucleation was preferred, non-isothermal crystallization kinetics shows that EVA14 could form tridimensional crystallites, whereas EVA18 (18 wt% VAc) and EVA28 (28 wt% VAc) are prone to crystallize two-dimensionally, as a result of more noncrystallizable VAc co-monomers introduced in the crystallizable ethylene segments. The growth rate falls on the following sequence: EVA14>EVA18>EVA28. Moreover, the kinetic crystallizability G also well characterizes the variation of the non-isothermal crystallization of these EVA materials, in the view of structural impediment caused by the VAc content.

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Crystallinity of ethylene–vinyl acetate copolymers

Cited by 37 publications

References 1 publication

Effect of vinyl acetate content on the photovoltaic‐encapsulation performance of ethylene vinyl acetate under accelerated ultra‐violet aging

Effect of vinyl acetate content on the photovoltaic‐encapsulation performance of ethylene vinyl acetate under accelerated ultra‐violet aging

Thermal analysis and FT‐IR studies of adsorbed poly(ethylene‐stat‐vinyl acetate) on silica

Non-isothermal crystallization and melting of ethylene-vinyl acetate copolymers with different vinyl acetate contents

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