Rubber testing booklet
44Pages

Testing with precision © Goran Spetz 2016 Elastocon AB Tvinnargatan 25 SE-507 30 Bramhult, SWEDEN www.elastocon.se

Preparation of test pieces 6-7 Testing of uncured rubber 8-12 Elastocon - Rubber testing 3

Standardisation What is a standard and standardisation? To create a standard is to set up rules,create order and make selections, in order to rationalize as well as to define various requirements, e.g. concerning matters of safety etc. A standard tells you how to do something how to produce a particular object, use a terminology, and to employ a method of testing or some other procedure in a specific manner. An International standard has first been set up in accordance to a particular set of rules and it is then approved and implemented. A standard can be regarded as an agreement between...

How is international standardisation carried out? Internationally, the co-operation in standardisation is carried out within the ISO, the International Organisation for Standardisation, which has 87 member countries. The counterpart within electrical standardisation is the IEC, International Electro technical Commission. In addition to the ISO and IEC there are the European organisations for standardisation, CEN (European Committee for Standardisation) and CENELEC (European Committee Electro technical for Standardisation). The importance of these organisations has greatly increased in...

Preparation of test pieces Preparation of test pieces The testing of rubber is either starting from uncured rubber or from cured rubber products. Testing can also apply to the uncured or cured state. The preparation of the test pieces is an extremely important part of the testing itself and it must not be the case that the test results reflect the effects of the preparation rather than the properties of the materials being tested. Temperature conditioning of the test material is also an important part of the preparation. Testing cured properties ISO 4661 In order to test cured properties,...

Testing materials in products In certain cases, one is interested in testing the material properties of a rubber product. Sheets 2 mm thick or cylindrical pieces are cut from the product for testing. A slicing machine or a cutting machine is very useful for this purpose and consists of a band knife or a rotating blade, which can cut off thin strips from a product. The cylindrical pieces are cut from thicker parts of a product with a rotating knife. Conditioning ISO 23529 Prior to testing, the test material must often be conditioned. After test sheets are cured, there is a specified waiting...

Testing of uncured rubber Batch control Batch control is the name given to the tests, which entails that each batch of mixed rubber is checked before it is used in any further processing. The testing can include the determination of viscosity, cure curve, density and hardness. Viscosity – Plasticity In the processing of rubber, it is important that the material has a suitable viscosity for the purpose. If the viscosity is too low the material will become difficult to process, e.g. due to increased stickiness, cold flow and low strength. If the viscosity is too high, processing requires...

Extrusion plastometers The most common instrument used in determining the viscosity of rubber polymers and compounds is the Mooney viscometer. The Mooney viscometer can be described as a rotation viscometer, in which the rubber is sheared between an inner rotor and an outer die. The die has a diameter of 50 mm and a height of 10 mm. The normal rotor has a diameter of 38 mm. For the measurement of high viscous materials, there is a smaller rotor with a diameter of 30 mm. The temperature of the die can be adjusted and normally 100 °C is used. The rotor is rotated with a speed of 2 rpm. This...

Testing of uncured rubber Compression plastometers The principle used in a compression plastometer is very simple – the testing piece is pressed together between two parallel plates using a constant load and the compressed thickness is measured. This simplicity explains the previous widespread use of the method within the rubber industry. Apart from the simplicity, the method has few advantages. It does however have a whole series of disadvantages: a) The shear rate is low, between 0.1 to 1 s-1. b) The rubber is not sufficiently deformed in order to   break down the thixotropic structure...

Measurement of the curing process in instruments with oscillating movements ISO 6502 Curemeter with rotor, ISO 3417 The construction and design of this instrument is similar to the Mooney viscometer with certain differences in the dimensions of the dies and the design of the rotor. The rotor is formed so that it is thicker in the centre and tapers off towards the extremities so as to obtain the same shear stress throughout the whole of the test material. The rotor oscillates sinusoidally at 1,7 Hz and normally with an amplitude of ± 1°. A torque sensor attached to the torque arm of the...

Testing of uncured rubber Rotorless Curemeter In the rotorless curemeter, the lower half of the die rotates and the torque is measured by a torque sensor. The amplitude is normally lower than that of the rotor type, namely ± 0,2°. In addition to the torque, which is a measurement of the rigidity, the damping and the crosslink rate can be registered. A rotorless curemeter has the advantage that it allows changes of the test specimens to be made quickly, since you do not need to peel off the cured sample from any rotor. On the other hand, however, it must be loaded with test pieces with an...

Mechanical testing Important factors Climates ISO 23529 Polymer materials are sensitive to temperatures close to normal ambient temperatures in a completely different way than what metals are. Careful control of the temperature is therefore necessary when carrying out tests. Many polymer materials, e.g. cellular material, are sensitive to humidity and particularly the relative humidity of air. It is therefore necessary to control this factor. It is not sufficient, however, to perform tests in a well-­ efined climate. The material must be in a state of d equilibrium with the surrounding...