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.

The Cake Analogy – Fillers

Posted on April 9, 2014 by Norman Challinor

Fillers

When it comes to the rubber industry, there is one metaphor that seems to explain all the necessities and intricacies of rubber. “Making rubber is a lot like making a cake”. Since starting at J Allcock & Sons, I’ve heard it over a dozen times, and it still surprises me how apt a saying it is!

I’ve tried punching holes in the saying, and thought I’d finally done it when it came to this subject. If virgin rubber is the flour, release agents the butter on the tin and accelerators the yeast, what would fillers be in the cake analogy?

Calcium Carbonates – CaCO₃

Calcium Carbonate is a classic filler for the rubber industry. A cheap and fine grade filler suitable for almost all rubber compounds. If you want to reduce the cost per kilo of a rubber compound (and have already tried reclaim/rubber crumb, we hope!) CaCO₃ can stiffen up a compound as well as significantly decrease the total cost of a compound, but it will decrease the compound’s physical properties (another point Reclaim and Crumb can beat CaCO₃ on)

J Allcock & Sons provide 2 main types of Carbonate, Trucarb and V/40S Whiting. Trucarb is affectionately known as ‘Ground-up Derbyshire’ as it is simply naturally occurring limestone ground into a fine powder. If you are looking for a cheap filler, Trucarb is the way to go. V/40S Whiting is exactly the same chemically as Trucarb, but acquired from evaporating river water in Italy, and is therefore purer. This produces extremely fine powder of bright white, which is perfect for decreasing the weighted cost of a white compound, without dulling the brightness.

Here is the first hurdle for the cake analogy. Calcium Carbonate is, ironically, a lot like Sodium Bicarbonate in cakes, reducing the total amount of flour needed to produce the same amount of cake batter.

Taken From: http://www.glogster.com/marianchemistry5/calcium-carbonate-sophia/g-6mfbv68tglod14n058a6ja0

Barytes

Barytes is a powder of Barium Sulphate, and is at least twice as dense as CaCO₃. Barytes is extremely good at adding weight to your compound, such as a use in moulding rubber weights. Barytes is also very resistant to acid corrosion, as well as x-rays, infrared and radar. It can provide a ‘deadening’ quality to the rubber compound too.

We provide a single grade of Barytes, Barytes Supreme, which may not provide stealth-grade material, but will bring weight and deadening to a rubber compound.

Barytes could be considered as the fruit and raisins of a cake, any rubber compound made with Barytes will come out like a fruit cake; hard, heavy and resistant to almost anything.

Taken from: http://www.barytes.org/barytes.html

‘Talc’/Magsil – Magnesium Silicate

Talc is another speciality filler for the rubber industry (as well as plastics, paints and paper). Thanks to it’s microscopic disc shape, Talc is able to add slip to a compound (see below for an excellent diagram). Very little talc is needed to help a compound through extrusion and calendaring, as well as adding some mild reinforcement to your compound. Talc has an extremely ‘active’ surface, again due to the flat disc shape of the particles, and thus can absorb sulphur and slow a compound’s cure rate. This can be rectified with the use of glycol.

Taken From: http://en.wikipedia.org/wiki/File:Talc.GIF

Talc is also often used externally on a compound as a dusting agent (or anti-tack agent) , allowing the stacking of uncured compound sheets without the risk of them sticking together (exactly like the cosmetic use for Talcum powder).

Talc can also be partnered with Silanes, a molecule designed to chemically bond fillers with compounds such as rubbers and plastics, allowing a much larger amount of filler to be used without the degradation of properties normally associated with the use of fillers en-masse. (this will be expanded upon in the next blog post)

Two grades of Talc are available from J Allcock & Sons; Magsil Topaz 350 (or T350) which is our standard Talc, or Magsil Diamond which is a finer powder and thus is able to add greater slippage.

With its brilliant white colour, this fine powder has to be the icing on the cake, literally. Though icing sugar may not add slip to the top of a cake, it is a final addition that completes the baking of a cake in much the same way as powdering with talc signifies the completion of a rubber compound’s mix.

Thanks to Norman for helping with the technical details and editing. As always, if you have any questions please don’t hesitate to contact me by e-mail at matt@allcocks.co.uk or by telephone on +44 (0)161 223 7181

ISO 9001:2008

Posted on April 3, 2013 by Luke Gilbert

J. Allcock & Sons have been certified ISO 9001:2008 since 14th of January 1997. This month we had our re certification audit and have now gained certification up until 9th March 2016.

We are proud to be certified ISO 9001:2008 and believe this shows our commitment to keeping high standards and customer satisfaction throughout our organisation. We also believe we are probably the only rubber recycler in the UK to attain this certification.

ISO 9001:2008 Certificate