Terephthalic acid and related derivatives p-Xylene is the principal precursor to
terephthalic acid and
dimethyl terephthalate, both
monomers used in the production of
polyethylene terephthalate (PET)
plastic bottles and
polyester clothing. 98% of
p-xylene production, and half of all xylenes produced is consumed in this manner.
o-Xylene is an important precursor to
phthalic anhydride. The demand for
isophthalic acid is relatively modest, so
m-xylene is rarely sought (and hence the utility of its conversion to the
o- and
p-isomers).
Solvent applications and industrial purposes Xylenes are used as a solvent in
printing,
rubber, and
leather industries. It is a common component of ink,
rubber, and
adhesives. In thinning
paints and
varnishes, it can be substituted for
toluene where slower drying is desired, and thus is used by
conservators of art objects in solubility testing. Similarly it is a
cleaning agent, e.g., for
steel,
silicon wafers, and
integrated circuits. In dentistry, xylene can be used to dissolve
gutta percha, a material used for endodontics (root-canal treatments). In the petroleum industry, xylene is also a frequent component of paraffin solvents, used when the tubing becomes clogged with paraffin wax.
Laboratory use Xylene is used in the laboratory to make baths with dry ice to cool reaction vessels, and as a
solvent to remove synthetic
immersion oil from the microscope
objective in
light microscopy. In
histology, xylene is the most widely used clearing agent. Xylene is used to remove paraffin from dried microscope slides prior to staining. After staining, microscope slides are put in xylene prior to mounting with a coverslip.
Precursor to other compounds In one large-scale application, para-xylene is converted to
terephthalic acid. The major application of ortho-xylene is as a precursor to
phthalate esters, used as
plasticizer. Meta-xylene is converted to
isophthalic acid derivatives, which are components of
alkyd resins. ==Chemical properties==