(S.P.Prokopchuk,
12, Kosmonavtov avenue, flat 30, Vinnytsa-21,
Ukraine, 21021)
Synopsis:
Modification of
thermoplastic polymers (polystyrene, vinyl acetate,
polyacrylates, polyvinyl chlorides) by introduction of
oxygen or oxygen containing gas (air) into monomer
polymerization zone and heating of the peroxicontaining
polymer which is being formed to 110-180
o
C. The ways of
utilization of modified polymers to produce electric
insulating, thermo insulating and soundproof materials,
construction, corrosion protective, fiberglass plastic and
impregnation materials; radiation protective materials,
corrosion-proof products and anticeptic, anaesthetic
preparations are offered.
INTRODUCTION
Polymeric
materials are widely used in different branches of industry
and everyday life. Intensive development of industry
requires polymeric materials with different physical and
chemical properties. Such material can be developed by
synthesizing new polymers or by modifying already known
polymers [1-3].Modification of the known polymers is a more
economical and perspective method than synthesis of new
polymers since it does not require raw materials to develop
them. With respect to heating the well-known polymers are
divided into thermoplastic and thermo reactive [4,5]. Both
types of polymers have their advantages and shortcomings.
Thermoplastic polymers are mainly cheaper than thermo
reactive. But they have lower heat resistance than thermo
reactive polymers. Low cost of polymers and high thermal
stability enables to replace now used thermo reactive
polymers by modified thermoplastic polymers. This also
reduces the cost of the manufactured products and in many
cases the quality of the products is improved. Thermoplastic
polymers can be transformed to thermo reactive polymers by
introduction active centers or groups into the polymer, they
destruct at high temperature and form ross-linking of
polymeric chains as in thermo reactive polymers [6,7]. Such
transformation is carried out by introduction of peroxide
compounds into the polymer by copolymerization with peroxide
oligomers or monomers. Such modification of polymers is
expensive and explosive since the synthesis of the
peroxide groups
requires additional material, energy costs and observation
of
the
requirements to the synthesis of explosive materials.
Another
shortcoming of this method is increase of modified polymers
embrittlement
in the process of heating at the expense of polymeric chains
hard
cross-linking.
DISCUSSIONS
This paper
offers a cheaper and less explosive method of modifying
polymers, this method enables to develop heat resistant
polymers having small embrittlement. The method [8] is
realized by introduction of oxygen or oxygen containing gas
(air) into polymerization zone. Then oligomer radicals join
oxygen molecules and form polymeric chains containing
peroxide groups.
Polymerization
process takes place under the temperature below 90-110
o
C. Higher
temperature (above 110
o
C) leads to
destruction of peroxide groups and
formation of
oxioligomer radicals which further take part in the
polymerization
process. This
results in low molecular polymer chains, structural changes
in polymer forms and weakening of its physical and chemical
properties. Hence,
oxygen in
monomer polymerization zone is considered to be undesirable.
Depending on the product produced by changing the process of
oxygen introduction during monomer polymerization high or
low molecular compounds
containing
different numbers of peroxide groups in their chains can be
obtained.
Oxygen may be
introduced into polymerization zone both, at the initiating
of small oligomer chains (after short period of
polymerization) and during the formation of higher molecular
olygomers (at later stage of polymerization). The number of
peroxide groups in the polymer being modified can be
regulated by changing speed and duration of oxygen
introduction. When being used, the modified polymer must be
heated at the temperature of 100-180
o
C. In the
process of thermal treatment it looses viscosity or gains
elasticity depending on the condition of the initial
modified polymer. This is accompanied by decomposition of
peroxide groups and by formation of oxyoligomer radicals
which possess high chemical activity. They easily iteract or
transfer radicals into polymer chains, thus leading to
cross-linking of polymeric chains, changes in supermolecular
structures of polymer and formation of set layer. In the
process of the polymer hardening its embrittlement increases
a little as oligomer oxyradicals being formed change
supermolecular structure of polymers without causing high
tension in them. Polymer modified in such a way can be used
to develop new polymeric materials or different products.
Field of application of polystyrene, vinyl acetate,
polyacrylates, polyvinylchloride, polyvinyl alcohol widens
considerably. This method can be used to modify polymers
developed in the process of radical polymerization of
monomer in mass or in solution. Polymers modified by this
method can be used in different fields,
possible ways
of their application are given below.
Possible ways
of application of modified polymers
Electrical
insulating materials
As it is known
polystyrene is one of the most spread and cheap polymers
with high dielectric properties which enables it to be used
as electric insulating material [9]. However, application of
polystyrene based electric insulating materials is limited
as polystyrene has low heat resistance and poor adhesion.
Modifying polystyrene by the offered method it is possible
to change its properties considerably by converting it to
thermo reactive polymer which has high heat resistance and
higher adhesive properties. This enables to develop new
cheap and high quality electric insulating materials on the
base of modified polystyrene (lacquers, compounds),
electrical appliances materials for electrical equipment,
which can have high Comparative Tracking Index (CTI) of
Electrical Insulating Materials. Utilization of such
materials only as electric insulating lacquers to coat
electric wires enables to use thinner wiring in electric
motors, thus reducing their weight, cost and quality
respectively.
Corrosion
protective materials
Modified
polymers can also be used as corrosion protective materials
by coating equipment, machines, reservoirs, copper plating,
copper monuments and other surfaces. Modified polymers can
be applied to different surfaces in the form of lacquers,
low molecular polymers or heated viscous solutions of
polymers. The first two types of polymers are applied on the
surface by usual
methods (by a
sprayer, etc.), the surface is dried and heated by a
portable heater (electric or gas) to the temperature of
110-180 o
C to
form glassy solid surface. Heated viscous solutions of
modified polymers are applied by means of stationary or
portable screw electric appliances. Thus, protective
coatings can be applied on different surfaces on the base of
polyvinyl acetate, polystyrene, polymethylmethacrylate,
polyvinylchloride and other polymers.
Radiation
protection materials
Modified
polymers can be used to produce different radiation
protection means:
clothes,
containers, storages, devices casing. These materials can be
produced
by applying
modified polymer on metal foil (aluminium or copper) when
making clothes or by applying on thin metal sheets
(aluminium or other materials) when manufacturing other
protection means (containers, storages and etc.).
Manufacturing
of corrosion resistant products
Modified
polymers can also be used to manufacture different products,
in particular, to manufacture parts for equipment and
machines, building materials.
Such products
can be obtained by pouring heated modified polymer into
different moulds. To obtain products with specific
properties these polymers can be mixed with different
fillers beforehand. In particular, to obtain current
conducting products mixed with graphite or metal powders; to
obtain harder products polymers can be mixed with granite
fine powder, asbestos, titanium
dioxide
or with other fillers. Besides, to obtain new polymer
materials possessing specific properties polymer mixtures
comprising different modified polymers can be used when
manufacturing different products:
polymethylmethacrylate – polystyrene, polymethylmethacrylate
– polyvinyl
acetate,
polystyrene – polyvinyl acetate.
Manufacturing
of glass fibre plastics and impregnating materials
Modified
polymers can also be used to obtain glass fibre plastics or
other impregnating materials out of cheap polymers
(polyvinyl acetate, polystyrene
and acryl
polymers). Then, the quality of the products improves and
their cost
reduces as
expensive polymer materials (polyether, epoxy and other) are
substituted by cheap modified polymers. The quality of the
products is improved owing to chemical bond of impregnating
material and oxide radical which is formed during modified
polymer heating during decomposition of peroxide containing
polymer chains.
At present
glass plastics and impregnating materials on the basis of
these thermoplastic polymers are not practically
manufactured since such polymers
do not possess
the required qualities. Only polymers modified by means of
the
offered method
can be used to obtain glass fibre plastics and impregnating
aterials as they are transformed to thermo reactive
polymers. Such products
can be
manufactured by two methods: to apply heated modified
polymer on8
impregnating
material or to heat impregnating material together with
modified
polymer to the
required temperature.
Manufacturing
of structural materials
Polystyrene is
a structural material for the products which are not
subjected to large mechanic loads as it possesses small
mechanical strength (brittleness) and it shows a tendency to
ageing. Modified polystyrene can be used to manufacture more
durable structural materials by heating modified polymer to
110 – 180
o
C and by
filling appropriate moulds of structural products with it.
To introduce melted polymer a screw heater can be used or
simple filling. In certain time depending on modified
polymer polystyrene will be polymerized and hard closs-links
will be formed. Different fillers (powdery, net, fabric,
reinforced) may be used during structural materials
manufacturing, the fillers combine well with the polymer by
means of the formed oligomer oxyradicals and thus they
increase the products mechanical strength.
Manufacturing
of thermal insulating and sound – insulating materials
To manufacture
such materials modified polystyrene or other thermoplastic
material (polyvinyl acetate, etc.) can be used. Modified
polymer is mixed with low boiling substance (isopentane or
its fraction), is poured into a hollow autoclave and heated
to 180 o
C. Then
the pressure is released and the foaming polymer fills
completely the hollow autoclave of the set shape. In certain
time, depending on the modified polymer, the autoclave must
be opened and porous polymer is taken out. Thermal and sound
insulating materials will have higher mechanical strength
than polysterene manufactured in usual method, as foaming
material will have cross closs-links between polymer chains
formed by oligomer oxide materials.
Manufacturing
of anticeptic and anaesthetic preparations and materials
Polymers on the
basis of esters of acrylic acids (polybutylmethacrylate) and
polyvinylacetate can be used as raw material to manufacture
such preparations and materials. To obtain the above said
materials and preparations modified polymer is gradually
heated to 110 – 180
o
C, powdery
anticeptic, analsthetic remedies are added or iodine vapours
are passed through polymer. Anticeptic and anaesthetic
substance or each taken separately is introduced into
polymer. During the modified polymer heating oligomer
oxyradicals interact with added substances and form oligomer
chains containing anticeptic and anaesthetic substances.
These modified polymers can be used as base for
manufacturing different anticeptic and anaesthetic
preparations in the form of ointments, aerosols or to
manufacture special anticeptic and anaesthetic materials:
plasters, packs, bandages. When the above preparations or
materials contact with injured surface (wound) anticeptic
and anaesthetic substances can penetrate into a wound,
disinfect it and soothe pain. Then, the injured place is
covered with polymer pellicle which prevents foreign
substances and microbes from getting into the wound.
Besides, the anaesthetic preparations produced by means of
this method do not allow local anaesthetics remedies to
penetrate into blood, most of them have narcotic properties,
thus preventing their influence on human organism.
CONCLUSIONS
Modification of
thermoplastic polymers by introduction of oxygen or oxygen
containing gas
(air) into monomer polymerization zone and heating of the
peroxicontaining polymer which is being formed enables to
extend utilization of
the most spread
polymers and to obtain different polymer products, which has
some advantages in comparison with existing products.
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