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    Polyvinyl acetate

    http://si-resinjam.co.ir/en/polyvinyl-acetate.html
    posted in Science

    Polyvinyl acetate, PVA, PVAc, poly(ethenyl ethanoate), is a rubbery synthetic polymer with the formula (C4H6O2)n. It belongs to the polyvinyl esters family with the general formula -[RCOOCHCH2]-. It is a type of thermoplastic.

    It should not be confused with the related polymer polyvinyl alcohol, which is also called PVA.

    Polyvinyl acetate is a component of a widely used glue type, commonly referred to as wood glue, white glue, carpenter’s glue, school glue, Elmer’s glue (in the US), or PVA glue.

    Preparation
    PVAc is a vinyl polymer. Polyvinyl acetate is prepared by polymerization of vinyl acetate monomer (free radical vinyl polymerization of the monomer vinyl acetate).

    Discovery
    Polyvinyl acetate was discovered in Germany in 1912 by Fritz Klatte.

    The monomer, vinyl acetate, was first produced on an industrial scale by addition of acetic acid to acetylene with a mercury(I) salt[3] but it is now primarily made by palladium catalyzed oxidative addition of acetic acid to ethylene.

    Properties
    The degree of polymerization of polyvinyl acetate typically is 100 to 5000. The ester groups of the polyvinyl acetate are sensitive to base hydrolysis and will slowly convert PVAc into polyvinyl alcohol and acetic acid.

    Under alkaline conditions, boron compounds such as boric acid or borax cause the polymer to cross-link, forming tackifying precipitates or toys such as Slime and Flubber.

    Microbial degradation
    A number of microorganisms can degrade polyvinyl acetate; most commonly, damage is caused by filamentous fungi however there are also algae, yeasts, lichens and bacteria that have been shown to degrade polyvinyl acetate.

    Applications and uses
    As an emulsion in water, PVAc emulsions are used as adhesives for porous materials, particularly for wood, paper, and cloth, and as a consolidant for porous building stone, in particular sandstone.Uses:

    • as wood glue PVAc is known as “white glue” and the yellow “carpenter’s glue” or PVA glue.
    • as paper adhesive during paper packaging converting
    • in bookbinding and book arts, due to its flexible strong bond and non-acidic nature (unlike many other polymers). The use of PVAC on the Archimedes Palimpsest during the 20th century greatly hindered the task of disbinding the book and preserving and imaging the pages in the early 21st century, in part because the glue was stronger than the parchment it held together.
    • in handcrafts
    • as envelope adhesive
    • as wallpaper adhesive
    • as a primer for drywall

    The stiff homopolymer PVAc, but mostly the more soft copolymer a combination of vinyl acetate and ethylene, vinyl acetate ethylene (VAE), is used also in paper coatings, paint and other industrial coatings, as binder in nonwovens in glass fibers. sanitary napkins, filter paper and in textile finishing.

    PVAc can also be used as coating to protect cheese from fungi and humidity[citation needed].

    Text for article taken from wikipedia.org.

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