Plastics compounders are striving to be competitive and seeking cost reduction opportunities in order to cope up with changing global economic conditions. Maintaining a high level of batch-to-batch quality provides compounders the required competitive edge and enables them to meet more rigorous quality standards. Moreover, the continuous expansion of the application space for thermoplastics necessitates new performance requirements that need to be confirmed through testing.
Compounders can demonstrate performance for a wide range of values in order to relate to customer applications by testing under non-ambient conditions. Heat Deflection Temperature and Vicat Softening Temperature are typical examples of tests that are widely used. Compounders are also working on increased throughput in testing and automation solutions in order to support this requirement. Since there is no definite melting point for thermoplastics that accurately represents the transformation from solid to fluid, analyzing the slow softening experienced by them when temperature increases is a key step to determine their quality and performance.
Testing Solutions from Zwick
Zwick provides a complete suite of testing solutions for compounders, of which the latest testing machines are Aflow and Mflow extrusion plastometers.
Aflow Extrusion Plastometer
The Aflow extrusion plastometer from Zwick is engineered for high throughput environments, supporting detection of melt volume flow rate (MVR) and melt mass flow rate (MFR). The system’s automation features, such as force-control and automatic parameter control, enable users to perform faster and more reliable melt index determinations. Force-control automatically controls stepless tuning of test loads as high as 50 kg, while the relevant parameters can be automatically set by automatic parameter control, which is especially helpful for polymers with an unknown MFR. In such situations, measurement accuracy could be reduced by the influence of operators in the detection of parameters. Automatic parameter control enables operators to auto program the test method for all flow rates, while push-button pre-compacting and cleaning save operator time. The Aflow extrusion plastometer, shown in Figure 1, reduces manual interference during the test procedure and increases accuracy in results.
Figure 1. Zwick’s Aflow extrusion plastometer incorporates a pneumatic feature which allows the polymer being tested to be defined and evenly pre-compacted at the press of a button.
Mflow Extrusion Plastometer
The Mflow extrusion plastometer from Zwick features program-controlled weight positioning and removal that streamlines the testing procedure by eliminating operator engagement for manually positioning the weights needed for testing each polymer.
Characterizing Plastics in Composites Applications
Fiber-reinforced plastics or composites are gaining momentum owing to their increased usage in the electronics, consumer goods, marine, aerospace and automotive industries. The typical characteristics of plastic composite compounds are sensitive flexural behavior and relatively high tensile strengths. As these materials demonstrate different mechanical behavior and properties when compared to unfilled plastics, the tests used for assessing their performance in application also differ greatly.
High strength, low weight and good stiffness are the typical characteristics of fiber-reinforced composites. They contain thin fibers which are either randomly or directionally oriented. Hence, it is necessary to employ different tests based on the main fiber direction. The material consisting of the fibers and the fiber alignment in the material are the key aspects controlling the properties of the fiber-reinforced composites. Hence, it is necessary to consider fiber orientation in materials testing procedures for fiber-reinforced composites and employ different tests accordingly. The scope of tests carried out on composites is industry-specific and standards-driven. The two essential prerequisites for performing tensile tests on plastic composite compounds are specimen loading over a large area, which can be done by applying load transmission components in the form of bonded tabs, and a tensile load precisely aligned axially. For more sophisticated testing, for instance, as per a Nadcap certification, special aids are utilized to provide axial and angular errors in any direction to be determined.
The variety of tests employed once needed frequent equipment changes. Zwick has addressed the market demand for improved test efficiency and throughput with the introduction of the latest Allround-Line system for performing tests on composites. This new system, shown in Figure 2, is a one-stop solution to customers, enabling them to perform over 20 different types of tests as outlined in more than 100 standards. Zwick offers the new Allround-Line composite testing machine in 100 and 250kN versions. An optional temperature chamber enables the Allround-Line to accommodate non-ambient testing in the range of -70 °C to +250 °C. Hence, the new equipment can perform a larger number of tests, including some highly complex, along with usual flexure, compression and tensile tests. Tests that can be performed on the new machine range from V-notched shear tests to fracture tests to determination of inter-laminar shear strength, lap-shear tests and static compression tests. The combination of shear loading and end loading methods are also possible with this new solution.
Figure 2. The new Allround-Line system for testing of fiber-reinforced composite specimens is compatible with 13 different test fixtures and operates in accordance with over 100 testing standards.
The modular testing system can yield defined and valid fracture values at higher compression strengths thanks to the improved pressure distribution. This solution, called the Hydraulic Composites Compression Fixture, can also be employed for performing open-hole and filled-hole compression tests to AITM 10008. This makes the Zwick Allround-Line an ideal solution that can perform a large number of different types of tests on fiber-reinforced composites in a single platform.
For over 150 years the name of ZwickRoell has stood for outstanding technical expertise, innovation, quality and reliability in materials and component testing. Our customers’ confidence in us is reflected in our position as world-leaders in static testing and the significant growth we are experiencing in fatigue strength testing systems. The figures tell the same story: in the 2011 the company achieved incoming orders of €185m.
With innovative product development, a comprehensive range and worldwide service, this family concern supplies tailor-made solutions for the most demanding research and development and quality assurance requirements in over 20 industries. With over 1100 employees, a production facility in Ulm, Germany, additional facilities in America and Asia plus agencies in 56 countries worldwide, the Zwick brand name guarantees the highest product and service quality.
This information has been sourced, reviewed and adapted from materials provided by ZwickRoell.
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