This document discusses chloroprene rubber, a synthetic rubber introduced in 1932. It summarizes that chloroprene rubber is produced through the emulsion polymerization of chloroprene monomers. It can be produced through two main processes - one using sulfur modification and one using chain transfer agents like mercaptans. The document also lists some key properties of chloroprene rubber, including good resistance to ozone, heat aging and chemicals. Finally, it outlines some common applications for chloroprene rubber like gaskets, cable jackets and hoses due to its temperature resistance and chemical resistance.

1. CHLOROPRENE RUBBER
Synthetic Rubber
(3152608)
- Prof. Bhakti Patel

2. Manthan Sonani
• 190280126033
Abhishek Sudani
• 190280126034
Pratik Talaviya
• 190280126035
Zadafiya Meet
• 190280126039
Sandip Kanzariya
• 190280126014
Jay Mavani
• 190280126017
Jenish Savaliya
• 190280126029
Parth Savani
• 190280126030
Team members

3. INTRODUCTION
Chloroprene rubber, whose nominal repeat unit is as shown at (XLV),
has the distinction of being the earliest commercially-successful
synthetic rubber. First introduced in 1932 by Du Pont under the trade
name 'Duprene', later sold under the trade name 'Neoprene', and
designated as GR~M (Government Rubber Monovinylacetylene) by the
U.S. Government during World War II, it is still produced in quantity
today by several large chemical companies, including Du Pont.
It is a stereoregular rubber, being,
in fact, largely trans-I,4-
polychloroprene. It is therefore
able to crystallise on stretching.
In consequence, its gum
vulcanizates have high tensile
strength.

4. Its vulcanizates show moderate resistance to swelling in
hydrocarbon oils and greases, combined with good resistance
to low temperature stiffening. They also show good resistance
to heat ageing, to oxidation and, in particular, to attack by
ozone. The chemical resistance of the vulcanizates is also
generally good.
Chloroprene rubber is considerably more expensive than are
the general-purpose hydrocarbon rubbers. Another reason is
that, useful though the balance of properties offered by
chloroprene rubber may be for some applications, there are
many applications for which one particular property of
chloroprene rubber is insufficiently developed. Thus, for
instance, for many sealing applications, the resistance to
swelling in hydrocarbon oils is inadequate. Or again, for other
applications, the resistance to high temperature may be
insufficient.

5. PRODUCTION OF CHLOROPRENE
RUBBER
Chloroprene rubber is produced exclusively by the free-radical
emulsion polymerisation of chloroprene. It is possible to polymerise
chloroprene by cationic initiation, by anionic initiation, and also by
Ziegler-Natta catalysis, but the reactions take place more slowly than
does free-radical polymerisation. Furthermore, the products of such
reactions lack useful properties.
Emulsion-polymerisation processes for the production of chloroprene
rubber can be classified broadly into two types:
I. Those in which control of the polymer molecular weight is achieved
by copolymerisation with sulphur followed by reaction in which the
polymer chains are cleaved at the sites where the sulphur is
copolymerised
2. Those in which control of the polymer molecular weight is achieved
by the inclusion within the polymerisation recipe of a chain transfer
agent.

6. Chloroprene rubbers produced
by the first type of process are
usually described as being
sulphur-modified, although
they are also sometimes
described as being thiuram-
modified because, as will
appear subsequently, the
reagent which is commonly
used to cleave the
polychloroprene at the sulphur
sites is a thiuram sulphide.

7. Chloroprene rubbers produced by the second of these processes are
usually described rather negatively as being non-sulphur-modified.
Little published information seems to be available concerning these
latter types. It is known that at least some of them are produced
using mercaptans as regulators of molecular weight.
Grades produced in this way are described as being mercaptan-
modified. When chloroprene is emulsion polymerised in the absence
of either sulphur or a chain-transfer modifier, the product which
forms even at low conversion is a tough, insoluble, non-plastic
material.
If sulphur to the extent of 0·5-1·5 % is dissolved in the chloroprene
monomer prior to polymerisation, the product of the polymerisation
is still a tough, insoluble material which is unsuitable for use as an
elastomer.

8. Class Typical
Acid Acceptor Metal oxides
(1) High-activity magnesium oxide, MgO
(2) Red lead, Pb3 O4
Vulcanizing
Agent
Zinc oxide
Vulcanization
Accelerator
(1) Thioureas for W and T-types, sometimes G (2) Sulphur-based for
W-types
Vulcanization
Retarder
MBTS in G-Types, CBS, TMTD or MBTS in W-types
Antioxidant Octylated diphenylamine
Antiozonant Mixed diaryl-p-phenylene diamines with selected waxes, to 3 phr
Fillers Carbon black; precipitated silica; calcium silicate; hydrated alumina;
china clay
Plasticizers Aromatic or naphthenic process oils; mono esters; polyester;
chlorinated waxes
Processing
Aids
Stearic acid; waxes ; low molecular weight polyethylene; high-cis
polybutadiene; special factices
Compounding Ingredients for Neoprene

9. Types G W T
Raw Polymer Limited storage
stability
Excellent storage
stability
Excellent storage
stability
Polymer and
compounds
peptizable to
varying degree
Non-peptizable
Need acceleration
Least nerve, non-
peptizable
Fast curing but
safe processing
Best extrusion,
calendaring
performance
Accelerators
usually not
necessary
Need acceleration
Vulcanizates Best tear strength Best compression
set resistance
Properties similar
to W-types
Best flex Best heat aging
Best resilience
Characteristics of Neoprene

10. PROPERTIES
The chlorine in the polymer reduces the reactivity to many oxidizing agents and thus improves
its chemical resistance.
Due to its low reactivity, it displays good resistance to ozone cracking, heat aging and chemical
attack. For example, it has good resistance to many chlorofluorocarbons, aliphatic
hydrocarbons, mineral oils, greases and ozone, but only moderate or poor resistance to acids,
solvents, and fuels.
Its flame resistance is excellent. In fact, chloroprene is one of the few rubbers that are self-
extinguishing.
It also gives excellent rubber-to-metal bonds. However, chloroprene tends to harden over time
and degrades in the presence of some fairly common chemicals such as hydrochloric acid,
acetone, xylene, acetic acid, and hydrogen peroxide.
Its mechanical properties are generally inferior to those of natural rubber but it has superior
chemical resistance and lower gas permeability.

11. APPLICATION
Chloroprene is used primarily for gaskets, cable jackets, tubing, seals, O-rings, tire-
sidewalls, gasoline hoses and weather-resistant products such as wet suits and
orthopaedic braces.
It is also used as a base resin in adhesives, electrical insulations and coatings. It has
many useful properties and a reasonable price.
Its typical working temperature range is between -35°C and +100°C.

12. THANK YOU….