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Rubber Mouldings

William Johnston & Company Limited- is recognised for technical ability, customer service and quality accreditation and supply custom rubber mouldings, thermoplastics, rubber injection mouldings, compression and transfer rubber mouldings with recognised approvals for specific industries.

We offer a wide range of rubber compounds meeting many industrial specifications including British and European standards, Automotive, MOD, WRAS and FDA requirements

Elastomer Types Overview
There is a wide variety of polymers available, each with their own unique properties. We recommend that our Technical Department is involved at the earliest opportunity to optimise all the various aspects of the product or service requirements and together find the most effective compound and efficient solution that will result in a technically accurate, cost effective and high quality end product for you.

WRAS approved EPDM compounds
Are used for cold and hot potable water use to the requirements of the UK, German and French water industries.

Nitrile compounds
Are approved to EN 549, EN 682 for gas applications and by WRAS for cold potable water use.

Fluorocarbon (FKM) and Hydrogenated Nitrile (HNBR) compounds
Are approved for use in Well Head safety equipment.

William Johnston & Company Limited are able to offer compounds that conform to British Standards, ISO, Def Stan (Defence Standard), DTD specifications, ASTM, AMS, WRC, WRAS and SAE. Below is an overview of some of the most common elastomers which we supply but please contact us for more specific information and assistance.

  Natural Rubber SBR EPDM Neoprene (CR) Hypalon* (CSM) Nitrile (NBR) Acrylic (ACM) Silicone (Si) Viton*(FPM) Fluro- silicone (FSi)
Basic Properties
Cost Factor 1 1 2 2 3 2 4 6 15 40
Hardness Range (Shore A) 30 - 90° 40 - 95° 30 - 85° 30 - 90° 40 - 85° 40 - 100° 50 - 85° 40 - 80° 50 - 95° 40 - 80°
Colours Full Range Full Range Limited Full Range Limited Limited Black Limited Limited Limited
Temperature Tolerances (degrees Celsius)
Maximum Continuous 75° 85° 130° 95° 130° 100° 150° 205° 205° 180°
Maximum Intermittent 105° 115° 150° 125° 160° 130° 180° 300° 300° 200°
Minimum Temperature -60° -55° -50° -40° -25° -20° -20° -60° -20° -60°
Environmental Tolerances
Oxidation Fair Fair Excellent Very Good Excellent Good Excellent Excellent Excellent Excellent
Ozone & Weathering Poor Poor Excellent Very Good Excellent Fair Excellent Excellent Excellent Excellent
Oil Resistance (degrees celsius)
ASTM Oil No. 1 @ 20° Poor Poor Fair Excellent Excellent Excellent   Excellent Excellent Excellent
ASTM Oil No. 1 @ 100° Poor Poor Poor Good Good Good Excellent Good Excellent Excellent
ASTM Oil No. 3 @ 20° Poor Poor Poor Good Excellent Excellent   Good Excellent Excellent
ASTM Oil No. 3 @ 100° Poor Poor Poor Fair Fair Good Good Fair Excellent Excellent
Fuel Resistance (degrees celsius)
ASTM Fuel B @ 40° Poor Poor Poor Poor Poor Fair Poor Poor Excellent Fair
Solvent Resistance (@ 20° celsius)
Alcohol Good Good Good Good Good Good Good Good Good Good
Acetone Fair Fair Good Fair Fair Poor Poor Fair Unsuitable Unsuitable
Benzene Poor Poor Poor Poor Poor Poor Poor Poor Good Good
Chemical Resistance
Acids Fair Fair Good Good Very Good Good Poor Fair Excellent Good
Bases Good Good Good Fair Good Fair Poor Fair Good Fair
Physical Properties
Physical Strength Excellent Good Good Good Good Good Good Poor Good Poor
Compression Set Good Good Good Fair Fair Good Good Good Good Good
Tear & Abrasion Resistance Excellent Good Good Good Good Good Good Poor Good Poor
Resilience Excellent Good Very Good Very Good Fair Good Poor Good Fair Fair
Permeability To Gases Poor Low Low Low Low Low Low Low Very Low Low
Electrical Strength Excellent Excellent Excellent Good Good Poor Fair Excellent Good Excellent
Flame Resistance Poor Poor Poor Self - Extinguish Good Poor Poor Good Self - Extinguish Self - Extinguish
Water Resistance Very Good Good Excellent Good Very Good Good Poor Good Good Good

*Du Pont Registered Trade Mark | †Bayer Registered Trade Mark

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Contact William Johnston & Company Limited

For more information about our Rubber Mouldings that are available world wide, contact us on +44 (0)141 620 1666, Email us or simply complete our online Enquiry Form.

Please note, failure to select the correct materials or products we supply (“the Products”) may result in damage to plant, equipment or property. In some instances, it may cause death or personal injury. We are not designers and do not give advice about design related matters concerning the Products. We can help and assist with the technical specifications for the Products. In specific applications, particularly where critical conditions exist, we will try to assist you within the limitations of the services that we offer. All information supplied by us is intended as technical co-operation outlining the specifications of the different Products which we supply. To the extent permitted in law, no warranty is given in respect of any information supplied by us. The customer must satisfy themselves as to the suitability of the Products for their intended application and use. The correct fitting of Products is the responsibility of the customer. Your statutory rights remain unaffected. Save in respect of death, personal injury or fraud, our entire liability to you, however arising from the supply of Products shall be limited to the £10M indemnity amount provided by our insurers.

William Johnston Accreditation