TECHNICAL - PHYSICAL CHARACTERISTICS
ENVIRONMENTAL IMPACT NEUTRAL
URETEK(r) resins combine to form thermoset polymers, produced from the reaction of a polymeric MDI and a poly-functional alcohol. Thermoset polymers are those that form irreversibly during a reaction, into a material that is infusible and insoluble due to the formation of a cross linked, thermally stable network.
The environmental impact of buried thermoset polymer samples was tested in a harsh environment - a disposal site - and evaluated after three and five years. The samples, although discoloured, did not change their structure. Analysis of the leachate water did not show any noticeable deviation in composition from leachate water derived from waste which did not contain samples.
To the best of our knowledge, reacted URETEK resins do not have any detrimental effect on the environment due to decomposition or degradation of the polymer. Many resistance tests have been carried out, inside and outside laboratories.
MECHANICAL PROPERTIES
Within certain limits, URETEK(r) expanding resins show a substantially elastic behaviour which means that they demonstrate deformations which are approximately proportional to the forces applied, according to Hooke's law.
Only when the force exceeds a certain limit (the Elastic Limit) is the internal cellular structure permanently modified and after compression will not recover its initial form. This Elastic Limit depends on the density of the material.
The four accompanying diagrams below illustrate the effect the density of the material has on its resistance to forces of compression, shear, bending and tension.
The expanded density of injected URETEK resins will vary according to the application and the particular type of resin used. Typical densities are 65 to 100 kg per cubic meter under floors and up to 300 kg per cubic metre in Deep-Injection.
Compressive strength
As URETEK expanding resins are primarily used to consolidate ground and relevel settled structures, it is clear that, from a practical point of view, their most important property is that of final compressive strength.
Uretek material has a high strength-to-weight ratio - usually much more than the ground it is replacing and certainly more than the ground it is compressing.
From the diagram, "Effect of density on compressive strength", it can be seen that the elastic limit can be very high. It is can be seen from the diagram that in the zone representing typical URETEK densities, the Elastic Limit varies between 10 and 65 kg cm2 (130 and 900 psi).
Shear strength
In the diagram "Effect of density on shear strength", the zone representing typical URETEK densities evidences considerable shear strength, based on a standard thickness according to the ASTM standard. Shear strengths can vary from 5 to 30 kg/cm2 (70 - 400 psi) according to the density of the material.
CHEMICAL AND OTHER PROPERTIES
RESISTANCE TO CHEMICAL AGENTS
The stability of resin is well documented and the use of such products is common in the construction industry.
From the accompanying table of chemical resistances, the resistance of URETEK resin material will be recognised as most satisfactory. Resistance to most solvents, gasoline and oil is good or excellent. URETEK material will swell in aromatic oxygenated solvents, but will regain its original properties when dried. It is stable in water solutions of common detergents, salts, acids, and bases. Strong acids and bases can attack the material and cause chemical degradation.
URETEK resin material is inert to mildew and fungi and will not get mouldy or decay. It does not nourish insects or rodents. It is chemically neutral.
When exposed to sunlight, ultra violet rays cause a yellowing of the resin and an embrittlement of the surface but this is not relevant to URETEK material as it is typically used underground.
RESISTANCE TO LIQUID ABSORPTION AND THERMAL STRESS
General description of the test
Samples of URETEK expanded material were subjected to immersion in various liquids and to cycles of thermal stress. After the test, the variations in volume were measured by means of a high precision optical measuring instrument and the degree of liquid absorption through variations in floatation thrust.
The test was carried out as follows:
Temperature cycle
There were 10 cycles, each one consisting of the following:
8 hours in air at 65øC
16 hours in air at 23øC
8 hours in air at 30øC
16 hours in air at 23øC
Tests of immersion in liquids
The samples were completely immersed in various liquids at a temperature of 23øC for 14 days. The liquids used were:
crude oil
fuel oil
gas oil
high octane gasoline
kerosene
Two of the samples already subjected to thermal stress were also subjected to this test. They were immersed in high octane gasoline.
Water absorption test
The samples were immersed in 1.25 m (4,1 ft) of water at 20øC (70ø F) for 7 days to determine absorption through percentage variations in their floatation thrust.
This test included samples which had been subjected to the two previous tests.
Conclusions
The 10 cycles of thermal stress described above left no visible trace on the material and its dimensions incurred no measurable variation.
The material was absolutely impermeable to water even after various immersions and almost completely impermeable to the other liquids used in the tests.
Thermal stress had the effect of reducing its total liquid content but probably because of evaporation occurring during the periods of high temperature.
TEST RESULTS
RESISTANCE TO SHRINKAGE AND DEGRADATION
The accompanying table shows the results of an experiment carried out in the USA to evaluate the effects of ageing on slabs of cured resin material of similar chemical composition to that of URETEK.
Samples measuring 300 x 300 x 50 mm (12" x 12" x 2" ) have been placed in two conditions. Some were kept in a warehouse and others buried in the ground at a depth of some 2.5 metres (8 ft).
Properties investigated were density, resistance, tensile elongation, compressive strength, thermal conductivity ("K" factor) and volume. Properties were measured at the start of the tests and again after 10 years. As can be seen from the results given in the table, after 10 years of ageing both in the warehouse and in the ground, the material has substantially retained its initial properties.
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