Ethylene vinyl acetate copolymer

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Structural formula
Structural formula of ethylene vinyl acetate
General
Surname Ethylene vinyl acetate copolymer
other names
  • Poly (ethylene- co- vinyl acetate)
  • Ethyl vinyl acetate
  • Ethylene vinyl acetate
  • PEVA
  • E / VAC
CAS number 24937-78-8
Monomers / partial structures
PubChem 32742
properties
Physical state

firmly

safety instructions
GHS labeling of hazardous substances
no classification available
H and P phrases H: see above
P: see above
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Ethylene-vinyl acetate copolymers ( abbreviated EVAC , formerly EVA ) are made from ethylene and vinyl acetate prepared copolymers .

Chemical and physical properties

EVAC is available as granules, aqueous dispersion , powder, but also as film material. The plastic has high heat resistance and good aging resistance .

Manufacture and use

The process for manufacturing EVAC largely corresponds to that for manufacturing PE-LD . However, the properties and possible uses can be varied greatly with the proportion of copolymerized vinyl acetate . Vinyl acetate proportions of up to 7% are used almost exclusively to improve the properties (in particular to increase the elongation at break ) of films. Around half of EVAC production is made with a vinyl acetate content of less than 7%.

EVAC with a vinyl acetate content of 7 to 18% is often used as the exclusive material for special applications. Examples are cold-resistant, pull-out spouts from canisters , foils for agriculture and horticulture, shrink-wrapping foils ( office supplies , solar modules ), shower curtains, floor coverings, roofing membranes and electrical cables .

The additional class of EVAC with up to 28% vinyl acetate is mainly used as a hot melt adhesive , which in turn is used for the fiber binding of very high-quality tufted carpets and needle punched nonwovens , for adhesive binding in book production and for manual use with hot glue guns .

A rubber-like thermoplastic elastomer is formed with vinyl acetate proportions of over 30 up to 90% . It is mainly used for shoe soles or as a polyblend together with other elastomers.

In photovoltaics , solar cells are embedded in EVAC. The EVAC used in foils is melted at temperatures around 150 ° C, becomes crystal clear and cross-linked in three dimensions. After cooling, there is a permanent bond that protects the cells from environmental influences.

EVAC micropellets are used in some cosmetic peelings.

The manufacture of EVA products can be used by injection molding or compression molding .

Chemical analysis

Various methods are available for determining the proportion of vinyl acetate in EVAC:

  • Dissolve the sample in a suitable solvent, hydrolyze the acetate groups by adding acid or base, back-titrating the excess acid or base
  • Infrared spectrometry on the sample film: measure the CH 2 / CO band ratio , quantify the vinyl acetate content by calibrating with EVAC of known composition
  • Dynamic differential calorimetry : measure the enthalpy of fusion of the sample, quantify the vinyl acetate content through calibration with EVAC of known composition (only applicable for pure EVAC)
  • Thermogravimetry : heating the sample up to 600 ° C, whereby the first degradation stage correlates with the vinyl acetate content, calibration with EVAC of known composition (only applicable for pure EVAC)

Round robin tests to determine the vinyl acetate content of EVAC show that the comparative standard deviation s R is slightly dependent on the vinyl acetate content and is mainly in the range from 0.6 to 2.2 g / 100 g. s R is a good estimate of the standard measurement uncertainty u . The data were determined by 7 or 8 laboratories with different analysis methods. All of the methods listed above were used.

market

The European market for EVAC currently (2007) has a capacity of approx. 600,000 t. The world's largest sub-market, at almost 400,000 t per year, is that for products with a vinyl acetate share of less than 18%. To this end, almost 200,000 t of EVM products are produced in Europe every year. However, the EVM quantities in Asia for the shoe industry there are significantly larger. The largest providers, in order of market share, are ExxonMobil , Versalis , Arkema , Repsol , DuPont and Total .

Some trade names are Greenflex, Levapren, Evatane, Elvax, Ultrathene (US), Miravithen, Phylon, Evasky.

Web links

Individual evidence

  1. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
  2. ↑ Compendium of Polymer Terminology and Nomenclature , IUPAC Recommendations, RSC Publishing, Cambridge, 2008, pp. 403f.
  3. ↑ BUND purchasing guide: Microplastics - the invisible danger
  4. ↑ a b ISO 8985: Plastics - Ethylene / Vinyl Acetate Copolymer (EVAC) Thermoplastics - Determination of Vinyl Acetate Content . 1998.
  5. ↑ Thermal Properties of Elvax® Measured by Differential Scanning Calorimeter (DSC). DuPont Elvax® EVA Resins Product Information K-27274. 2013.
  6. ↑ W. Weber: Determination of the vinyl acetate content by means of thermogravimetry . Mettler UserCom, June 1997, p. 13-14 .
  7. ↑ Bruno Wampfler, Samuel Affolter, Axel Ritter, Manfred Schmid: Measurement uncertainty in plastics analysis - determination with round robin test data . Carl Hanser Verlag, Munich 2017, ISBN 978-3-446-45286-2 , pp. 102-104 .