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MANUFACTURING & MATERIALS INNOVATION
P
VC (polyvinyl chloride), when
compounded with plasticisers,
is a versatile soling material
available in a range of
hardnesses. It is relatively inexpensive,
easy to mould, bonds well with PU
adhesives and has a good range of
general properties. Since the 1960s, PVC
has been second only to vulcanised
rubber in usage and is injection moulded
to produce sole units for a wide range of
everyday and casual footwear. It can also
be blended with other polymers to
provide oil resistance in industrial
footwear and used for all-moulded
footwear such as boots and beach shoes.
ENVIRONMENTAL
PRESSURES
Starting in the 1970s, the use of
several of the materials employed in the
synthesis or compounding of PVC has
been questioned on environmental
grounds. Concerns over health and the
environment led to European Directive
91/338/EEC (now incorporated into
REACH Annex XVII), which restricted the
use of cadmium to stabilise or colour
PVC. Most PVC products on the EU
market will now be free of cadmium,
although it is still possible to find
cadmium-containing materials sourced
outside the European Union.
Vinyl chloride monomer (VCM), the
chemical building block for PVC, is
generally recognised as a carcinogen
and, as a result, it is recommended that
the production of PVC is closely
monitored to ensure the safety of
operatives. This also means that the
quantity of the monomer residual in the
final product must be carefully controlled,
especially in packaging for the food
industry. It has in fact been suggested
that specifying food-grade PVC for use in
apparel may allay concerns over the
potential risks from VCM.
There are ongoing concerns about
plasticisers used to impart flexibility to
PVC. It has been shown that these may
be harmful to health and restrictions
have been placed on the use of certain
phthalate-based plasticisers. Currently,
three phthalates have been restricted for
all toys and childcare articles and a
further three are restricted in toys and
childcare articles intended to be
mouthed. While footwear is not explicitly
included in these requirements, several
retailers have adopted a precautionary
stance and are removing these
phthalates from their children’s products.
Under REACH (Registration, Evaluation,
Authorisation and Restriction of
Chemicals), certain phthalate plasticisers
will be prohibited from use in the
EU/EEA from 2015. This will include
some of those used in footwear.
PERCEIVED RISKS FROM
WASTE
Some environmentalists object to
PVC merely because it contains the
chemical element chlorine. This view
stems from the knowledge that certain
28
WORLD FOOTWEAR | NOVEMBER/DECEMBER 2012
PVC: confronting
the environmental
challenge
MIKE GEORGE, SATRA TECHNOLOGY CENTRE
CREDITS: SATRA