Dr. Sushil K. Verma
Director General
Central Institute of Plastics
Engineering & Technology,
Chennai
Preamble
Mechanical recycling of Plastics
Waste was developed initially as
inplant processing of industrial scrap
followed by post consumer waste recycling.
Between 1970 and 80s, technologies
of plastics recycling to obtain
monomers, valuable chemicals and
fuels were developed. Subsequently,
many innovative technologies for recycling
of segregated and co-mingled
plastics waste into value added materials
have been developed. The concept
of value addition by conversion of
mixed plastics waste containing dissimilar
plastics material products and
non-plastic waste into high performance
blends of composite plastic materials
could gain momentum in 1990s.
Since in many of the under developed
and developing countries of the world,
currently, the segregation of plastics
waste is not carried out, but, the major
focus of recyclers is to develop cost
effective, user friendly and eco-friendly
recycling processes to produce value
added products from co-mingled plastics
waste.
Process Sequence for
Recycling of Co-Mingled
Plastics Waste
Process sequence for recycling of comingled
plastics waste or scrap depends
upon the chemistry of the ingredients
and compatibility of various
polymers during the recycling process.
For example, mixed plastics
waste containing similar chemical
compositions such as polyolefins and
styrenics, may require limited
compatibilistion, whereas, co-mingled
plastics belonging to different chemical
families such as polyolefins, polyamides,
polycarbonate, polyesters,
polystyrene, polyvinyl chloride (PVC),
etc. would require compatibilisation
during recycling process.
Mixtures of polar polymers, such
as: Polyvinyl Chloride (PVC), Polycarbonate
(PC), Polymethylmethacrylate
(PMMA), Thermoplastic Polyurethane
(TPU), Polyamide (PA), Thermoplastic
Polyesters (PEST),
Polyglutarimides (PGI), Stryene Acrylonitrile
Copolymer (SAN) or Acrylonitrile
Butadiene Styrene (ABS)
could be compatibilised by incorporation
of two copolymers, the first
containing vinyl alcohol, the second
an anhydride. For example, blends of
TPU with Phenoxy, Ethylene Vinyl
Alcohol Copolymers (EVAI), Copoly-
mers COPO, modified cellulose, and/
or polyalkylene oxide, had attractive
physical, optical and barrier properties,
and are melt-processable without
degradation. They can be transformed
into films, sheets, or bottles with good
barrier properties. Blends containing
PA can be used for films, tubes, toys,
gears, bearings, shafts, curtain sliders,
door rollers, etc. The blends with
elastomers were reported suitable for
improved wiper blades. In general, the
sequence of operations for recycling
of co-mingled plastics scrap is as follows:
....contd.
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