Civil Engineering Reference
In-Depth Information
enough to break down their molecular structure, releasing chlorine atoms which
react with natural ozone and break down the ozone layer (see Table 9.3).
Alcohols and aldehydes
The alcohols that are mostly used as solvents, especially in varnishes, are
ethanol, propanol, isopropanol, buthanol, isobuthanol and methanol. Phenol is
an important ingredient in different building glues. Through further oxidation of
alcohol, formaldehyde (an important glue substance when mixed with phenol
and urea) is formed.
Ether alcohols and ketones
Important ether alcohols are glycol ethers such as methyl and ethyl glycol. They
are used as solvents and plasticizers in varnishes. Methylketone and methyl-
isobutylketone are the ketones used as solvents in chloroprene glue.
Amines
Amines are produced from hydrocarbons which react with ammonia. Amines
are most common as additives in plastics, e.g. silicon and polyester, mainly as a
hardener or anti-oxidizer. Amines are the starting point for the production of iso-
cyanate, which is the main constituent of polyurethane. Amines are also used in
the production of certain organic paint pigments.
Alkenes (or olefines)
This is the group name for hydrocarbons with double combinations. Amongst
the most important are ethylene and propylene, which are produced from naph-
tha and function as monomers in the production of polyethylene and polypropy-
lene. Vinyl chloride is produced by chlorinating ethylene and it is the main con-
stituent of PVC plastics.
Esters
Esters are formed when hydrocarbons react with acetic acid. Butyl acetate, ethyl
acetate and methyl acetate are commonly used as solvents in glue, while
polyvinyl acetate (PVAC), is an important binding agent in certain water-based
glues and paints. The acrylates are esters of acrylic acid, which is oxidized from
propylene, and is used as a binding agent in paints and the production of plas-
tics such as polymethyl metacrylate ('Plexiglas').
Phthallic acid esters
These esters are produced when phthallic acid reacts with alcohols. They are
used mainly as plasticizers in a range of plastics and can constitute as much as
50 per cent of a plastic. The most important types are diochtylphtalate (DOP) and
diethylhexylphtalate (DEHP).
