Modulus Of Rigidity By Static Method Viva
Elisabet Schwartzkopf
The machine frame of every MonTech Rheometers is constructed from aerospace grade aluminum and stainless steel making MonTech Rheometers the most rugged and stable Rheometer systems in the market. This design includes baseplates of up to 80 mm thickness, 50 mm stainless steel pullrods, massive 80 mm crossheads with integral stainless steel force crossbeam support for superb die symmetry and alignment as well as and up to 20 mm thick side panels. This results in an overall superior instrument stiffness; significantly improving repeatability and result correlation, while reducing signal-to-noise ratio as well as guaranteeing the best damping abilities, especially for high frequency testing and unbeaten dynamic testing performance.
This ultra-rigid instrument design has even more advantages: The whole instrument frame is used as a heatsink for all major electronic components so that the instrument does not need any fans or air ventilation for cooling, allowing the complete electronic cabinet to be sealed against pollution and especially conductive carbon black dust.
MonTech Moving Die Rheometers are equipped with a biconical die assembly with integrated direct heating, accurate sample temperature measurement, superior temperature control with unbeaten accuracy, highest heating and cooling rates, and minimized response times. The specific die and crosshead design ensures a perfect alignment and uniform closing as well as parallelism of both test dies, significantly reducing result variations. MonTech Rheometer test dies are entirely made from superior, lot-traceable stainless steel, hardened, precision ground and polished, making the dies built to last with an extreme stiffness and durability even against the most abrasive rubber compounds.
Every MonTech Rheometer is equipped with a pneumatic die closing system for a reliable closing and sealing of the die cavity. Optionally, instruments can be equipped with variable closing force, cavity pressure and variable die gap control. In combination with the MonTech loadframe, this instrument design guarantees compliant testing results at the highest possible level of accuracy and precision paired with perfect reproducibility and reliability.
Along with MonTech precision calibration tools, customers are guided through a software sequence, making the verification of the instrument really easy in order to always guarantee the highest instrument precision and most accurate test data. Once the verification process is completed, a detailed PDF Report with all critical verification and calibration is generated, assuring traceability to any reference standard used. Readings of most reference standards and performance parameters are taken by the software, minimizing operator involvement for providing objective results.
Torque / force transducers and loadcells are the most critical part when it comes to precision of the instrument because raw torque and force signals, as well as derived modulus and viscosity signals are directly used for test result calculation. This is exactly the reason why MonTech designs and manufactures all transducers in-house. This guarantees the widest measurement ranges along with clean-room applied strain gauge technology paired together in ultra-rugged and stiff assemblies.
The highly complex set of stress, strain and other raw data streams and results that are all time-critical to each other are analyzed in real-time with the most advanced 24-bit electronics and a 10 kHz high speed data sampling rate. This superior oversampling technology paired with the superior signal to noise ratio eliminates the need for data filtering or further data processing, providing the user with actual true measured data and results. MonTechs advanced rubber testing machines support customers with as much valuable material information as possible, with features including measurement of higher harmonics, nonlinearities, and behavior at extreme processing conditions.
Every MonTech Rheometer and Mooney Viscometer is equipped with a rugged, well-proven and reliable Programmable Logic Controller (PLC) system as well as standard automation components. Every instrument is directly equipped with an Ethernet interface, allowing direct integration of the machine into the customers network as well as linking host systems and computers by standard TCP/IP protocol with extremely highdata rates and throughput.
The MDR 3000 Basic instrument features a geared, brushless DC motor with integrated drive control systems, digitally connected to the instrument PLC unit, making this drive the ideal system for static testing at fixed frequencies.
Due to the rugged design and superior design quality, MonTech instruments clearly offer superior accuracy and precision, proven by our certifications and accreditations including ISO 9001:2008 and ISO/IEC 17025:2005.
These calibrations services are offered throughout the world by our highly qualified team of MonTech field engineers in order to make sure that the calibrations of your instruments are fully traceable and comply to all local, company, and international standards.
Isothermal cure experiments are the most common type of test for quality control in rubber and elastomer processing. MonTech Moving Die Rheometers provide high precision data as well as a simple operation of the instruments. All the important characteristics, such as minimum / maximum elastic torque, scorch times, cure times and reaction rates are precisely calculated, with over 3500 different datapoints. All data is available in numerical as well as graphical form; limits, control gates and tolerance graphs can easily be set, and Pass / Fail status is automatically evaluated after each test.
Especially for sealing applications, blowing agents form a vital part of compound recipes in order to produce a cellular structure via a foaming process that runs in parallel to the cure reaction. The cellular matrix structure which is created during the foaming process reduces density, increases thermal and acoustic insulation, and affects the relative stiffness of the mix. Therefore, MonTech Rheometers can be fitted with a precision normal force measurement transducer in the die cavity in order to calculate cavity pressure simultaneously during the curing and reaction in a single test, and revealing interrelations between the two reactions.
Test data from similar static or dynamic test sequences executed at different temperatures can automatically be evaluated and modelled for an advanced cure kinetics analysis, providing information about Reaction Rate, Order of Reaction (n), Rate Constant (k), Activation Energy (E) and Incubation Time (ti).
In general, the mechanical properties of materials depend on frequency. A good under-standing of the influence of frequency on a material is therefore very important for its practical use. For example, a material appears stiff under the action of a force at high frequency, but soft when the force is applied slowly. Isothermal frequency sweeps provide information about the weight distribution MWD (crossover modulus) as well as average molecular weight AWM (crossover frequency). But the behavior of viscoelastic materials like polymers not only depends on frequency, it also depends on temperature. MonTech has incorporated further advanced testing capabilities such as the Time-Temperature Superposition principle (TTS), which is based on the equivalence between frequency and temperature behavior during transition processes, forming the basis of WLF master-curve modelling available on MonTech dynamic Rheometers, even for predicting material performance at frequencies outside the range that can be measured with a dynamic mechanical analyzer.
The rheological properties of rubbers are related to their structural characteristics and will influence the behavior of the rubber during processing and the performance of the final product. While Mooney testing does not provide sufficient information to clearly differentiate branching and Molecular weight distribution the Rubber Process Analyzer can easily be used as a tool for solving production problems. Using frequency sweeps to scan the material over the whole shear rate range can reveal substantial materialdifferences and variations e.g. causing a particular material to be very sticky and therefore difficult to process while others can be perfectly processed.
These test can be performed in the linear and also non-linear viscoelastic range to cover all different processing methods and material states. ISO 13145 suggests a simple and quick test procedure utilising a rotorless sealed shear rheometer (RPA) for rheological evaluations as an alternative to traditional Mooney Viscometer testing.
Dynamic oscillatory shear tests are common in rubber rheology - more specifically, small-amplitude oscillatory shear (SAOS) tests are the most common test method for measuring linear viscoelastic properties of rubber compounds and polymers.
But in processing operations, the shear rates can be large and rapid; non-linear material properties form an even more important part in understanding material response. Therefore, MonTech Rheometers provide Fourier transformation analysis capabilities of periodic data, along with full raw-data access, for in-depth analysis to investigate and quantify the nonlinear viscoelastic behavior by using large-amplitude oscillatory shear (LAOS) testing in order to characterize and quantify material stress response which is no longer purely sinusoidal (linear), allowing a better understanding of filler content and structure, as well as the polymer architecture.
Typically, cure experiments on rubber compounds - especially for quality control purposes - are performed with a fixed oscillation angle of +/- 0.5 and a frequency of 1.67 Hz. However, for specific rubber compounds or challenging materials such as silicones or epoxy resins, this might not be ideal as either reaction torque readings are too low, providing only a limited ability to distinguish between different batches, or might be too high causing high result variability as the material is damaged as strain already exceeds the linear viscoelastic range. MonTech Rheometers provide the possibility of testing with variable oscillation angles to allow measurements within the ideal strain amplitude for optimal signal-to-noise ratio and the most precise test results, while avoiding any structural breakdown or slippage of the sample in the die cavity.
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