Nov 1, ASTM D Standard Test Method for Rubber-Measurement of Unvulcanized Rheological Properties Using Rotorless Shear Rheometers. Find the most up-to-date version of ASTM D at Engineering ASTM D describes a test method for determining the rheological properties of raw rubber and uncured rubber compounds. Using the RPA, the viscosity and .
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Rubber World — October Overview of rubber process testing in a changing global economy.
One hundred and twenty-five years ago, rubber technology was much more of an art than a science. Rubber compounders then would make judgments on the quality of a mixed batch of a rubber compound based on all five of their senses. There was a great deal of adtm and tacit knowledge about rubber, but not a lot of science with good, quantitative rubber test methods. In the s, Dr.
Melvin Mooney introduced the first practical viscometer for measuring the viscosity asmt a rubber stock. This instrument allowed the rubber compounder to apply actual quantitative measurements to his process. It was used to test raw SBR as part of the U. In the s, Monsanto Instruments Group now Alpha Technologies introduced the first successful curemeter, which was referred to as the ODR oscillating disc rheometer.
Unlike the Mooney, which could only measure rubber viscosity and scorch time time until the onset of vulcanizationthe ODR could also measure cure rate, state of cure, and even reversion, as well.
RPA troubleshooting for eliminating injection molding non-fills with ASTM D6204.
These instruments were so successful that over 10, of them were used throughout the world by the end of the s. It is interesting to note that on September 13,Alpha Technologies received the Trilogy Award for the creation of the ODR in recognition as one of the top tire technological achievements in the 20th Century. In the late s, after much research and development, Monsanto Instruments now Alpha Technologies introduced a new generation of curemeters known as the MDR moving die rheometers.
These new curemeters were rotorless in design, much more precise, could measure dynamic properties for the first time and required much less time to complete the test.
Because of the significantly shorter test cycles, the MDR has almost completely replaced the ODR, which has helped the rubber industry achieve its doubling in production productivity in the last 20 years.
In the s, the technology that went into the development of the MDR evolved into the RPA rubber process analyzer. The RPA was first introduced into the rubber industry in by Monsanto.
The development of various RPA test methods and techniques occurred in three separate stages: This testing was applied to both natural and synthetic rubber. These types of RPA test measurements helped motivate the development of ASTM D Part A in the late s for measuring these rheological differences within the linear viscoelastic region.
In fact, these same linear viscoelastic differences were also applied, using the Cox Merz rule, to measure shear thinning profiles dd6204 various mixed rubber compounds. Linear viscoelasticity measurements were made by the E6204 with the German Standard DIN 53 Part 2, using the Arrhenius equation to calculate different energy of activation values EA for rubber compounds with differing curative packages.
This was applied to calculate cure equivalents in determining state of cure profiles in tire curing studies. Also, with the programmable variable temperature analysis feature of the RPA, this instrument could also be used as a cure simulator for thick article cures, such as tires or conveyor belts.
This thermal ramp capability was standardized in ASTM D Part C, which has been used routinely to achieve better statistical test sensitivity to subtle differences in scorch times for compounds cured with different peroxide cure systems.
Factory problem solving with non-linear viscoelasticity to solve Six Sigma problems In the late s, the RPA was found to be invaluable in quality programs such as Six Sigma in solving factory problems.
Very early in the Six Sigma process, it was discovered that only the RPA tests, especially when applying higher strain amplitudes, could provide sufficient statistical test sensitivity by ASTM D to detect and provide the data for corrective actions for downstream quality problems involving mixed stocks in the factory. Even though high asm testing is by definition in the non-linear viscoelastic region, it still provided better statistical test sensitivity in the factory to downstream quality problems that conventional low-strain RPA tests in the linear region of aastm could not detect.
In addition, high strain testing in the non-linear viscoelastic region proved very useful with raw rubber sources, as well. From a joint study with the Rubber Manufacturers Association RMAit was found that higher strain test conditions with the RPA were necessary in order to distinguish important quality differences among quite different sources of natural rubber.
Just running low strain tests with the RPA did not make these distinctions. Studies comparing capillary rheometer measurements of quite different tire compounds carcass, tread, wire coat, black sidewall, apex, innerliner, etc.
RPA messurements at steadily increasing strain amplitude found that the correlation coefficient constantly improved significantly with higher applied strains.
In addition, it was found that running the RPA tests at high strains was more effective at measuring carbon black structural differences that are imparted to rubber compounds. So even though high strain testing is asgm conducted in the non-linear viscoelastic region, it was aatm to give superior statistical test sensitivity to real differences in mixed factory stocks, as well as raw rubbers.
However, the accuracy of the linear viscoelasticity from low strain testing is necessary for successful applications of time-temperature superposition TTS or finite element analysis modeling. These tests are used routinely throughout the rubber industry to insure that new mixed rubber stocks can provide the dynamic properties needed d624 rubber product performance, whether it is needed for tires, v-belts, golf balls, isolators, dampers, bushings or conveyor belts.
RPA dynamic properties of aerobic aged vulcanizates This RPA methodology was developed with parallel plate dies, because after these specimens are cured, they can actually be removed from the instrument and aged in an air oven for given time increments, after which these specimens are reinserted into the RPA to determine the change in dynamic properties from the established baseline.
This RPA test methodology is applied to measuring the dynamic property changes brought about from oven post-curing of compounds based on specialty elastomers such as FKM, silicone and ACM, or the air-oven aging of compounds based on conventional general purpose elastomers such as natural rubber, BR and SBR.
TPE and TPV viscosity and shear thinning profile comparisons are typically made by this new test method. Testing liquid elastomers Using the RPA, techniques were developed in to test liquid rubbers such as polyurethanes, silicones, polysulfides and certain liquid rubber adhesive compounds.
There is only a minimal cost to modify an RPA for testing liquids. Directly measuring viscous heating and heat buildup with the RPA Special methods were developed using the RPA to directly measure the viscous heating of a rubber compound that would result from processing a given uncured rubber compound in the factory, as well as also measuring the resulting heat buildup hysteresis of corresponding cured specimens which relate to dynamic product performance.
Direct measure of stress relaxation with the RPA Insoftware was developed that would allow the RPA to directly measure stress relaxation of either a raw elastomer or a mixed stock. Stress relaxation tests can sometimes characterize very high molecular weight elastomers better than a conventional frequency sweep. This particular test is sensitive enough to be used for testing raw elastomers, as well as mixed stocks giving a better characterization of the ultimate state of mix than Mooney stress relaxation can give.
So this is another method for quantifying the extent of completion for the silanization reaction.
Testing Standards List
As a result, there are now nine standard ISO and ASTM methods that have been established to date, and more new methods being developed for the immediate future. John Dick has over 39 years of experience in the rubber industry. He was with B. Goodrich, and later Uniroyal Goodrich Tire Co.
Dick has authored over 80 journal and magazine publications, including five books on rubber technology. He has consulted, presented technical papers or given seminars in over 38 countries.