Types of Rubber – Pick-and-Mix

Posted on August 13, 2014 by Matt Darlington

There are a near infinite variety of rubber compounds, with variety in mineral fillers, accelerators, curatives (and the type of cure), plasticizers, colour and of course the base rubber polymer. Rubber polymers come in two basic groups, natural and synthetic.

Natural rubber (NR), popularly known as Latex (when in the liquid form) or Natural Gum Rubber (once dried) is obtained mainly from the Hevea Brasiliensis Tree in South East Asia. Natural rubber consists of Cis-1,4-polyisoprene which can have masses as large as 1 million Daltons. Such large atomic structures, with plenty of double bonds, allows sulphur and heat to bond two double bonds of adjacent isoprene polymers with 3 or 4 sulphur atoms. This process is called vulcanisation, which was accidentally discovered by Charles Goodyear in 1839 using. Vulcanisation creates a network of bonds that changes the physical form of the Gum Rubber to the harder, elastic material that revolutionised the late 19^th century world.

Initially sought by the Germans in the 1^st World War, Synthetic Rubber was developed due to the Royal Navy’s Blockade causing a shortage of Natural Rubber. The first attempt at Artificial Rubber, Methyl Rubber, was of poor quality. Later attempts such as the Soviet use of Giant Dandelions to produce latex in WW2 weren’t much more successful. It wasn’t until the US Synthetic Rubber Programme developed Styrene Butadiene early in WW2 that a viable alternative to natural rubber became available, and the doorway to synthetic rubber polymers was opened.

There are now many types of rubber polymer, each tailored to the desired needs of the client. Below is a good rough outline to the characteristics of each rubber polymer, for example Acrylonitrile Butadiene Rubber is often used in oil seals and o-rings due to its excellent oil resistance:

Taken from: http://www.denka.co.jp/eng/organic/product/img/detail_001123_07.gif

We at J. Allcock and Sons are able to granulate NBR, SBR, EPDM, FKM and FFKM on site to any desired crumb mesh size, as long as the rubber is free of any textiles or metals. Crumb can be used as a filler in compounds, reduce the chance of trapped air causing lakeing during moulding or dusted onto rubber sheets to help the separation after cooling. Crumb is a great way to reduce compound cost without increasing the specific gravity of the compound (keeping volume costs down).

If you are interested in disposing of some of your cured rubber compound with us please get in touch via our website or phone us on 0161 223 7181.

Rubber Reclaim Part 2

Posted on January 17, 2014 by Luke Gilbert

Although we’ve blogged about Rubber Reclaim in two previous posts (31/08/12 & 13/09/12), we thought another blog would reinforce Rubber Reclaim as a viable rubber hydrocarbon source, carbon black source and process aid.

In the 31/08/12 blog, which is still available to read, we wrote about how it is made, its basic properties and why a compounder should use it. In this post we hope to expand on these slightly and talk about ourselves, as UK and European suppliers of Reclaim.

How Rubber Reclaim is made:

Step 1) Collection and Selection of suitable materials

This is probably the most important step. In order to get a uniform and consistent product you have to use the correct materials. This is a part of the process that for many years has been overlooked hence producing inconsistent materials.

Step 2) Reduction in size and removal of contaminants.

In Tyre Reclaim this consists of removing the bead wire, cutting out the side wall then granulating the remaining materials to 2-4mm removing textile and metals.

In Butyl Reclaim Tubes are de-valved and patches removed before being granulated.

Step 3) Blending

The rubbers are mixed with the chemicals required and the oils needed for the reclaiming process to take place.

All the chemicals and oils used today are REACH registered and compliant on PAH’s

Step 4) Cooking

This is where the materials are heated up. There are 2 main ways this is done either using an extruder to produce mechanical heat. Alternatively the materials are cooked in a digester using steam pressure to give 160° C

Step 5 ) Mastication

Either in the extruder or on a 2 roll mill the rubber is worked which breaks the polymer chain, also refining and blending the reclaim

Step 6) Filtering

The better quality producers at this point extrude the materials through a 60’s mesh (250 µm) filter to remove any undigested materials (nibs)

Step 7) Finishing

The filtered material is either extruded into blocks or is put back on a mill where a paper thin sheet is built up to 15mm thickness before being cut into blocks, coated in anti-tack agent and weighed off into the desired bundle weight (normally 25 kilos, but any bundle size is possible on request)

So why should you use Rubber Reclaim?

3 Reasons; RHC Source, Carbon Black Source and Processing Aid.

1) Rubber Hydrocarbon Source

Reclaim is a more cost effective source of rubber hydrocarbon than virgin rubber.

Attractive Price – Reclaim generally contains 50%+ RHC . For every 1% Reclaim you add you save 0.6% on Compound Cost*
Price Stability – Prices are not affected by NR and SBR prices.

* Based on an average compound cost of £1-70/kg

NR Prices versus Reclaim Prices

2) Carbon Black Source

Tyre reclaim contains approximately 27% of reinforcing Carbon Black
Easy to use as a Black Masterbatch
Much cleaner and easier to handle

3) Processing Aid

Improved Processing
Uniformity
Low Heat Development
Low Thermoplasticity
Minimum Reversion
Low Swelling and Shrinkage
High Rate of Cure
Good Aging
Good Shape Retention
Improved Tack

Other Savings include reduced mixing times and power consumption

Markets

There are 3 main types of rubber reclaim; tyre, butyl and EPDM. These reclaim serve a number of markets:

1) Tyre Reclaim

Tyres- New
Retreading
General Moulding
Belting
Adhesives
Footwear
Sheeting/Matting

2) Butyl Reclaim

Inner Tubes
Tyre Lining
Tyre Repair
Cable Bedding Compound
Sound Reduction
Sheeting & Belting
Mastics and Adhesives

3) EPDM Reclaim

Automotive Extrusions
Hoses
Civil Engineering Extrusions
General Moulding
Roofing Membrane

Where do J. Allcock & Sons fit in?

J. Allcock & Sons are UK distributors of Rubber Reclaim for GRP Limited, who are based in India and have a maximum capacity of 89,000MT’s per year.

We have been supplying reclaim from GRP Limited for many years and have proven it to be a successful partnership and have expanded our customer base overseas.

Although GRP Limited have distributors all over the world, any enquiries are welcome and if we cannot supply GRP Products to your location ourselves, we would happily point you in the right direction!

To conclude this post. Please do not hesitate in emailing ja@allcocks.co.uk or phoning on +44 (0)161 223 7181 for any enquiries or information on reclaim. We firmly believe reclaim has a place in todays rubber compounding market.

Red/Brown & Green FKM Crumb Available

Posted on July 15, 2013 by Luke Gilbert

Red/Brown and Green FKM Crumb

J. Allcock & Sons’ now have the ability to provide an extra 11 tonnes of Red/Brown FKM Crumb and 4 tonnes of Green FKM crumb per month.

Cured FKM scrap is sent to our facilities on a monthly basis and we granulate and “crumb” this FKM scrap to 72′s and 120′s mesh particle size. These particle sizes are not averages, so when we say 120′s Green FKM Crumb, we mean the biggest particle you will find will be 120′s mesh!

We always ask the customers we visit: What’s the cost of testing FKM Crumb in your compound? Compare that amount, to the amount you will be saving if tests came back positive and you started using it…

If you are interested in trialling some of the above crumb, please contact us at ja@allcocks.co.uk or +44 (0) 1612237181.

Alternatively, if you are unsure about using a different FKM compounded crumb in your own FKM compound, why not speak to us about “crumbing” some of your scrap and J. Allcock & Sons’ sending it back to you?

Carnauba Wax

Posted on April 22, 2013 by Luke Gilbert

I haven’t written a technical blog recently, so I have decided that I should write one regarding Carnauba wax. We have high stocks of Type 3 Carnauba wax, in powder form, so perhaps it might bring us some new sales!

With the help of Norman Challinor, here is some information on Carnauba wax!

Carnuaba wax is also known as Brazil wax and Palm wax. It is a hard wax obtained from the leaves of the palm copernicia prunifera - a plant native to and only grown in north eastern Brazil.

It is usually in the form of hard yellow / brown flakes that can also be ground down to a fine powder and often offered in that alternative form.

Due to its fantastic properties compared to other waxes, most people believe it is one of the best waxes in the world; hence it is sometimes referred to as the “queen of waxes.”

It has a melting point of 80 – 86 ^oc and a density of about 0.97

The main components are:-

Aliphatic esters                                                   (40% by wt.)
Di-esters of 4 – hydroxycinnamic acid                (21% by wt.)
ω – hydroxycarboxylic acids                               (13% by wt.)
Fatty acid alcohols                                              (12% by wt.)

Predominantly derived from acids and alcohols in the c₂₆ – c₃₀ range.

Carnauba wax, can come in Type 1, Type 3 and Type 4. These “types” relate to the purifity level, with Type 1 being most pure and Type 4 being least.

It has a very wide range of uses, including …..

Polishes (Usually Type 4 used)
Food (chewing gum, gravy, sauces, sweets etc) (Usually Type 1 used)
Pharmaceutical (tablet coating agent) (Usually Type 1 used)
Cosmetic (Usually Type 1 used)
And of course, as a process aid and mill / mould release agent in rubber compounds, particularly the harder to process specialist materials. (Usually Type 3 used)

For rubber compounders:

In rubbers, the hard nature of the material will not act as a softener but will behave as an internal lubricant, facilitating the incorporation and dispersion of the non-rubber ingredients.

Its relatively low melting point means that it will migrate to the surface of the rubber and form an extra, very thin, layer between the rubber surface and the metal it is in contact with – - i.e. The mill bowls or the mould surface. The hardness of the wax means that it will not act as a sticky softener, but will form a release layer, overcoming the tendency for the rubber to stick to the metal.

Allcocks mostly sell, Type 3 Powder, and we really focus on selling to the high specification rubber compounding industry, such as FKM compounds.

Here is some technical information on our T3 Carnauba Wax Powder:

Solubility                                      Insoluble in water; partially soluble in Alcohol.
.                                                   Soluble on warming in Ethyl Acetate & Xylene.
Melting Point                               80-86°C
Acid Value                                   2-7 mg KOH/g
Sponification Value                     78-95 mg KOH/g
Ester Value                                 71-93 mg KOH/g
Sulphated ash                             No more than 0.25% w/w
Unsaponifiable matter                 50-55 μm
Particle Size                                100% passing 600 μm
.                                                   94.8% passing 300 μm
.                                                   88.1% passing 250 μm
.                                                   40.6% passing 125 μm

If you have any questions regarding carnauba wax, please feel free to email ja@allcocks.co.uk! Despite only selling T3 Carnauba Wax powder, please feel free to get in touch regarding other types, we may be able to help.