1. HARDNESS
The most common method for classifying polyurethanes is according to their hardness, which is measured on a durometer. Vastsky
elastomers offer a very wide hardness range in which items can be produced, ranging from 10-15 Shore A to over 90 Shore D.
2. ABRASION RESISTANCE
In applications where severe wear is a problem, Vastsky elastomers offer outstanding durability when compared with rubber plastics
or even metals. In many applications the unusual combination of properties has made it possible to design and fabricate products
from Vastsky Elastomers using less material than has been possible with other elastomers.
It should be emphasised, however, that abrasion resistance is a complex property. Selection of the most suitable Vastsky elastomer
should be based on actual experience or simulated service tests.
Vastsky is able to conduct abrasion testing using the DIN and TABER methods, using the relevant testing machine shown.
3. COMPRESSION PROPERTIES
Vastsky elastomers have greater load-bearing capability than conventional elastomers of equal hardness. This capacity is an important
advantage in some designs, eg. stripper springs, whilst in others it is the very factor which makes them possible. In addition to high
load bearing properties in both tension and compression, Vastsky elastomers have a high shear load bearing capacity.
4. MECHANICAL PROPERTIES
At lower hardness levels practically all elastomeric materials, merely bend under impact. As conventional elastomers are compounded
up to higher hardness they tend to lose elasticity and crack under impact. On the other hand, Vastsky elastomers even at their highest
hardness levels, have significantly better impact resistance than almost all plastics.
5. TENSILE PROPERTIES
Vastsky elastomers are characterised by high elongation, high tensile strength and high modulus. This provides a combination of
toughness and durability in fabricated parts.
The tensile test is normally carried out on a tensile testing machine. In this test we are not only interested in the overall stress-strain
curve, but also the shape of the curve and the ultimate elongation, as these also provide valuable information. A high elongation at
break, a long rubbery plateau followed by a steep rise to break indicates a high toughness.
6. TEAR STRENGTH
Tear Strength together with a high split tear, is a strong indication of toughness.
In actual use, especially in impingement abrasion applications, high tear strength is important. Vastsky elastomers have a distinct
advantage in this application over conventional rubber.
7. RESILIENCE
Resilience in conventional rubbers is generally a function of hardness. This often undesirable relationship does not hold true with
Vastsky elastomers. Formulations are available in a very wide range of resilience.
For very shock-absorbing uses, low rebound compounds are usually used. eg rebound values of 10-40%. For high frequency
vibrations or where quick recovery is required, compounds in the 40-65% rebound value, are used.
In general, toughness is enhanced by resilience.
8. FLEX PROPERTIES
Vastsky elastomers resist cracking under repeated flexing. As with any elastomer, the rate of cut growth under flexing may be
reduced by decreasing the thickness of the part. Unlike other elastomers however, Vastsky elastomers can be used practically
in very thin sections because of their strength and toughness.
9. LOW TEMPERATURE PROPERTIES
Many Vastsky elastomers remain flexible at very low temperatures and possess outstanding resistance to thermal shock.
The low temperature resistance of Vastsky's has led to many applications in below 0oC(32oF) conditions.
10. DRY HEAT RESISTANCE
Whilst many Vastsky elastomers are only suitable for continuous operation up to 90oC (194oF), intermittent use up to 120oC (248oF)
is possible, with some specially formulated materials, continuous operation up to 120oC or even higher can be achieved.
11. WATER RESISTANCE
Depending on the type, Vastsky polyether backbone elastomers are very resistant to the effects of water immersion and have
excellent long-term stability in water up to 50oC (122oF). Continuous use in hot water over 80oC (176oF) is not recommended.
Water absorption is very low, in the range of 0.3-1% by weight and volume swell is negligible. For example, Vastsky elastomers
can operate at close tolerance in water lubricated bearings without fear of seizure.
12. ELECTRICAL PROPERTIES
Some Vastsky's have very good insulating properties and are used in many potting and encapsulating applications.
13. OXYGEN AND OZONE RESISTANCE
Products made from Vastsky's are highly resistant to degradation by atmospheric oxygen and ozone. Tests on samples, aged over 500 hours in an atmosphere containing 3ppm ozone, show no attack even while under 20% strain. Past experience has shown that materials which resist this concentration for several hundred hours are virtually immune to attack by normal atmospheric concentrations.
This makes Vastsky's highly successful when employed around electrical equipment, without the hardening and cracking often experienced with conventional elastomers, and indeed, many plastics.
14. OIL GREASE AND CHEMICAL RESISTANCE
Whilst many rubbers and plastics have excellent resistance to one or more specific solvents, oils or chemicals, the wide resistance of Vastsky's to chemical attack means that they can be used in a multitude of environments with the exception of strong acids and alkalis and certain strong solvents.
As with all materials being examined for oil and chemical resistance, it is best to place a sample of the material in actual service. If this is not practical, tests should be devised which simulate actual service conditions as closely as possible.
15. RADIATION RESISTANCE
Vastsky elastomers are considered to have the best resistance to gamma ray radiation of all elastomers. They retain a high proportion of their original flexibility and toughness whilst exposed to gamma radiation.
16. FLAME RESISTANCE
Vastsky elastomers can be formulated to meet several self extinguishing or fire resistant specifications.
17. MOULD, MILDEW, FUNGUS RESISTANCE
Suitably formulated Vastsky elastomers, usually polyether based, do not support fungus growth and are generally resistant to such attack. This makes them particularly suitable for tropical environments.
18. FRICTIONAL PROPERTIES
Vastsky elastomers resemble most plastics and elastomers in that friction against non-lubricated surfaces generally decreases with increasing hardness. A high coefficient of friction is valuable for such products as solid industrial tyres, feed rollers, drive rollers etc.
High hardness compounds have the lowest coefficient of friction, and formulations having very low values are available. Such formulations are widely used for bushings, bearings and wear strips.
Wear of shafts and mating surfaces is minimal, and usually considerably less than with conventional plastic materials.
19. MACHINEABILITY
Vastsky elastomers can be machined using conventional equipment but you should consult Vastsky for specific recommendations and procedures.
20. BONDING TO OTHER MATERIALS
During the initial moulding process and under controlled conditions, Vastsky's can be bonded to a wide variety of materials. High strength bonds can be obtained to most metals, wood and many plastics. Bond strengths often exceed the tear strength of the Vastsky itself. These bond strengths, usually exceed the bond of rubber-metal substrate by several times.
It is more difficult to bond cured Vastsky sheet or mouldings to other materials but special techniques have been developed to satisfy most requirements.
21. NOISE REDUCTION
Special formulations are availablefor sound deadening and anti-vibration applications.
For advice on the most suitable material product for your needs please call our Technical Service personnel to discuss.