Neoprene
By Paul Morales
Neoprene
Simple 4 carbon polymer with a single chlorine attached to the double bond.
Neoprene
Also known as polychloroprene.
Neoprene Truths
• Annual consumption of
nearly 300 000 tons worldwide
• Widely used due to its
favorable combination of
technical properties.
• Mainly used in the rubber industry (61%)
– also important as a raw material for adhesives (both
solvent based and water based (33%)
– has different latex applications such as dipped articles (e.g.
gloves) and molded foam. (6%)
Interrogate #1
What property does
chlorine give to the overall
polymer?
• Lower flammability!!!
Neoprene Truths cont.
• The typical delivery form is “chips”
• The polymer is not characterized by one outstanding
property, but its balance of properties is unique
among the synthetic elastomers. It has:
– Good mechanical strength
– High ozone and weather resistance
– Good aging resistance
– Low flammability
– Good resistance toward chemicals
– Moderate oil and fuel resistance
Neoprene Truths cont.
• According to the IISRP, in 2000 the following production
facilities and producers are shipping polychloroprene into
the market place:
Company name
Country
Capacity (Metric Tons)
DuPont Dow Elastomers
USA
100 000
Bayer AG
Germany
65 000
EniChem
France
40 000
Denki Kagaku Kogyo
Japan
48 000
TOSOH
Japan
30 000
Showa DDE
Japan
20 000
• Additional capacities are located in Peoples Republic of
China and Armenia.
Early History
• During the 1920s the
increasing demand for natural
rubber led to higher and
higher prices,
-There for sparking a search for an
equivalent synthetic rubber.
• In 1932, Wallace Carothers
produced a rubber-like
substance during a
polymerization experiment
using chloroprene.
-A chemist in DuPont's fundamental
research group.
History 1930s
• The polymer was originally called Duprene and in 1937 DuPont
discontinued the trade name
– They changed it to "neoprene"
– The name change was also used to signify that the material was an
ingredient, not a finished consumer product.
• It was also used in consumer goods like:
– gloves
– shoe soles
• Although production was stepped up
– it was all claimed by the military.
• World War II removed neoprene from the commercial market.
• Essentially unchanged since 1950, neoprene continues to be essential in
the manufacture of
– adhesives,
– sealants,
– power transmission belts,
– hoses and tubes.
History 1950s
• It wasn't until the 1950s
that neoprene was first
used in a wetsuit.
• Hugh Bradner,
– a University of California,
Berkeley physicist is often
considered the original
inventor and "father of the
modern wetsuit.”
• Corporate legend Jack
O'Neill from San Francisco
was known for pioneering
the application of neoprene
wetsuits around 1955.
History 1960s-Present
• During the 1960s a new type of neoprene was pioneered.
– Up until this time, the process of manufacturing neoprene involved
petroleum and petro-chemicals.
– Petro based polymers use a polymerization process that heats oil to
extremely high temperatures.
• Yamamoto Corporation developed special technology to
convert the calcium carbonate from limestone into
chloroprene rubber chips and then further processing to
achieve neoprene foam with a very high micro-cell
structure.
• This new process results in neoprene with very different
characteristics to oil based neoprene.
• Yamamoto has been marketing their Yamamoto limestone
neoprene since this inception.
Types of neoprene
• Normal linear grades (general-purpose grades):
– General-purpose grades are mostly produced with n-dodecyl mercaptan
as the chain transfer agent and occasionally with xanthogen disulfides.
– Depending on the ingredients used the polymer can be more readily
proccessible and give improved mechanical properties.
• Precrosslinked grades:
– Precrosslinked grades consist of a blend of soluble polychloroprene and
crosslinked polychloroprene.
– They show less swelling after extrusion (die swell) and better
calenderability.
– Precrosslinked grades are particularly suitable for the extrusion of profiled
parts.
Interrogate #2
What is Vulcanization?
• It is chemical process
for converting rubber or
related polymers into
more durable materials
via the addition of
sulfur.
Types of neoprene
• Sulfur-modified grades:
– Sulfur-modified grades are copolymers of chloroprene and elemental
sulfur.
– Sulfur-modified grades are used in particular for parts exposed to dynamic
stress, such as driving belts, timing belts or conveyor belts because of their
excellent mechanical properties.
– But the polymers are less stable during storage and the vulcanizates less
resistant to aging.
• Slow crystallizing grades:
– Slow crystallizing grades are polymerized with 2,3-dichloro-1,3-butadiene
as a comonomer.
– This comonomer reduces the degree of crystallization by introducing
irregularities into the polymer chain.
– Crystallization resistant grades are used to produce rubber articles, which
have to retain their rubbery properties at very low temperatures.
• Overall will focus on the one type of neoprene
production:
– Limestone based neoprene.
Limestone Neoprene
• Limestone neoprene has a high micro-cell structure.
– These are independent closed cells (bubbles basically)
within the neoprene that are packed together at an
extremely high density.
– limestone neoprene has a 94% cell penetration.
– less dense than oil-based neoprene.
• Because of this micro-cell structure, limestone neoprene
provides several serious distinct advantages to the functionality
of wetsuits compared to the traditional oil-based neoprene:
– It is more impermeable
– It is lighter in weight
– It is warmer
– It is more durable
– It is stretchy
Oil-Based Neoprene (comparison)
• Low micro-cell structure.
• Oil-based neoprene has a cell penetration of 60-70%
– The amount of bubbles or pockets with in the polymer, oil
based neoprene has low density closed cells.
• Also denser than limestone neoprene.
• Problems associated with inferior-quality neoprene:
– Delamination: blisters between the nylon and rubber which
deteriorates quickly
– Compression: neoprene 'cave-ins', especially around the
knee/elbow areas
– No memory: does not return memory (hold its shape) and the
fit gives out over time
– Splits: neoprene splits unnecessarily within the nylon layers
The Makings!!!
• Yamamoto uses acetylene derived from the calcium
carbonate found in limestone.
• Extracted limestone is fed into a furnace and heated at
a temperature around one-tenth of that used for
refining petroleum
• Calcium carbide is produced by heating coke with
calcium oxide (limestone) in an electrical furnace up to
2000 °C.
The Makings cont.!!!
• Calcium carbide reacts with water, releasing acetylene,
C2H2.
CaC2(s) + 2 H2O(l)  C2H2 (g) + Ca(OH)2 (aq)
• Dimerization of acetylene by passing it through an
aqueous solution of Ammonium Chloride and Cuprous
Chloride at 343K.
• Vinylacetylene performs a Markonikov addition under
acidic condition to produce Chloroprene
The Makings cont.!!!
• The Chloroprene obtained undergoes Polymerization to give
Neoprene. Though no specific catalysts are needed for this process
but the polymerization becomes faster in the presence of Oxygen or
peroxide.
• The polychloroprene rubber chips are melted and mixed together
with foaming agents and black carbon pigments, and then baked in an
oven to make it expand.
• It's during this process that Yamamoto's specialized technology
combines with the calcium carbonate to create the micro-cell
structure of limestone neoprene versus the regular oil-based
neoprene.
Limestone Neoprene
Oil-Based Neoprene
Overall
• Polychloroprene will continue to be one of the
most important synthetic specialty elastomers
because its balance of properties is unique.
Sources
• Polychloroprene (CR), chloroprene rubber:
http://www.iisrp.com/webpolymers/04finalpolychloropreneiisrp.pdf
• NEOPRENE: THE INSIDE STORY: http://www.korduroy.tv/2012/neoprenethe-inside-story/
• How is Yamamoto limestone neoprene made:
http://www.seventhwave.co.nz/wetsuits101/neoprene+info/How+is+Ya
mamoto+Limestone+neoprene+made.html
• Pictures: https://www.wikipedia.org