eXpert 7600 Single Column Universal Testing Machine

eXpert 7600 – Optional Long-Travel Extensometer

Nanoengineered biomaterials from polymers and nanoclays continue to generate interest in biomedical and biotechnological applications due to their high water content, biocompatibility, and shear-thinning characteristics. In this study,  the rheological implications between model clay and polymer system of poly(ethylene glycol) and Laponite for use in 3D bioprinting and cell delivery are investigated.

The ADMET eXpert 7600 Single Column Testing System equipped with 25 lb load cell was used for compression testing of 3D printed and cast (bulk) hydrogel. Strain rate of 1 mm/min was used to compress the samples 50% of original height. The compressive modulus was calculated and plotted to compare bulk versus 3D printed structures. Compressive modulus of print and cast hydrogels were compared and no difference was observed.

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Grips and extensometer for ASTM D1708 microtensile testing

Summary:

Historically, test method ASTM D1708 has been used to measure the tensile and elongation properties of plastics that have little amount of material available. There are also many other ASTM test methods for specific materials (FEP, ETFE, PTFE) that reference the same test method a list of which is referenced below. A change has been made to the ASTM D1708 tensile specimen shape so that it now is the same as the shape found in ISO 12086-2. ASTM D1708 is no longer the preferred plastic microtensile method as ASTM recommends the much more common ASTM D638 tensile test using the very small type V specimen shape. If interested, another ADMET page discusses ASTM D638 here.

The convenient feature of D1708 is that the specimen shape is such that an extensometer is not required to perform the test. Rather, the universal testing machine’s built in jaw separation position is sufficient to measure elongation. It becomes critical however that you have a very accurate initial jaw separation which happens to be less than an inch.

Equipment Required:

1. Universal Testing Machine (UTM) of the constant-rate-of-crosshead-movement variety. I’m not aware of any manufacturer that makes anything but this type anymore. However, the UTM should be servo-controlled to maintain the set speed throughout the test.
2. Load Cell accurate to at least 1% of the reading. Also, the breaking strength of the material should be between 1/100th and the full capacity of the load cell. For example, a 100 lbf load cell should be used to measure from 1 – 100 lbf.
3. Tensile Grips of the “vise” or “side action” variety so as not to interfere with the elongation measurement. Serrated, plain, and rubber coated jaw faces can be used. Pneumatic grips of the “side action” type can also be used. Self-tightening grips such as eccentric roller and wedge styles are not good for this test. Eccentric roller grips are hard to set the jaw separation properly and wedge grips have the same problem but can also add an undesirable compressive load on the sample. Systems that adjust grip separation automatically to accommodate a compressive load then adjust the gauge length. It’s not tricky as it sounds if you use a simple pair of manual tensile vise grips.

The cost for a system that meets the accuracy requirements of the specification and include all the items above generally start at around $ 8,000 USD. Depending on vendor and options chosen, typical 1kN – 50 kN systems range in price from $8,000 – $ 40,000 USD. The major cost driver with these systems is the maximum force capacity of the system. 1 kN & 5 kN single column systems are sufficient for many materials when testing to a microtensile method and are the most cost effective. Larger capacity 10, 25, 50, 100 kN and higher dual column systems are also available that can perform this test as well and performing other high capacity tests.

Other Microtensile Test Methods:

1. ASTM D2166 Section 11.4 – Tensile Properties of FEP Fluorocarbon Molding and Extrusion Materials
2. ASTM D3159 Section 11.4 – Tensile Properties of Modified ETFE-Fluoropolymer Molding and Extrusion Materials
3. ASTM D4745 Section 12.4 – Tensile Properies of Filled Compounds of Polytetrafluoroethylene (PTFE) Molding and Extrusion Materials
4. ASTM D4894 Section 10.7 – Tensile Properties of Polytetrafluoroethylene (PTFE) Granular Molding and Ram Extrusion Materials
5. ASTM D4895 Section 10.7 – Tensile Properties of Polytetrafluoroethylene (PTFE) Resin Produced From Dispersion

Video of a Micro tensile test:

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Stretch wrap film, commonly made from polyethylene plastic, is a clear packaging film normally used to wrap large or bulk items for transportation or warehousing purposes. ASTM D5458 is a testing standard designed to measure the “cling” between two layers of stretch wrap film. This is a relevant measurement because two or more layers of stretch wrap are usually in contact with each other. For example, stretch wrapped pallets require several layers of film to secure and are usually moved across, or transported on top of, other wrapped pallets. This post is designed to help you understand the test procedure and equipment needed to perform this test with certainty. When you are ready to test products to this standard, please refer to and follow the steps in the official ASTM specification.

Procedure:

This test requires a special fixture (shown below).

1. There are two types of samples to prepare. A large piece of film to go on the fixture, and smaller film strips of film that are attached to film clips. Make sure to carefully prepare each specimen as indicated.
2. Clamp the large film sample on the bottom of the incline of the fixture (outside face up).
3. Secure the loose end of the sample with the steel rod to create a smooth surface. If you wish to perform the test on a stretched piece of film:
   a. Select your desired elongation %
   b. Place the steel rod on the distance down the incline face that matches your desired elongation %
   c. Roll and secure the loose end of the film on the steel rod in that position
   d. Pull the rod back to stretch and clamp the film
4. Take a film strip sample (sandwiched between two pieces of paper for easier handling) and carefully press down .5 inches of the strip to the top of the incline. Make sure that the strip is parallel to the gridlines on the fixture.
5. Slide the pieces of paper and apply pressure to the rest of the film strip to create a smooth contact with the large sample.
6. Secure the end of the film strip closest to the bottom of the incline to the film clip.
7. Making sure data is being recorded; begin moving the crosshead upwards (the crosshead is connected to the film clip through a string and pulley).
8. Note the moment when the film strip begins to separate from the “cling line” demarcated on the fixture. The load at this moment is the cling strength of the sample.

Analysis:

1. Cling strength: load at which film begins to separate from the “cling line”.

Equipment Recommended:

1. 1. Special ASTM D5458 fixture with incline, steel rod, clip, and pulley. ADMET can provide you with this exact fixture.

1. Tensile testing machine capable of servo control (constant rate of movement) equipped with a 500g load cell. All ADMET testing machines satisfy these requirements. We offer a full line of load cells.
   eXpert 7600 single column testing machine equipped with pulley fixture used for coeficient of friction tests (similar to ASTM D5458)
2. A testing controller capable of moving the crosshead at the specified rate and displaying load in real-time. Both MTESTQuattro, our most advanced PC based controller, and the eP2 Digital Controller, a standalone unit, are capable of displaying a load/position curve in real time.
   
   MTESTQuattro (left) eP2 Digital Controller (right)

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In their study, National Institute of Health researchers describe the engineering of a bioinspired elastic and biocompatible hydrophobic light-activated adhesive (HLAA) that achieves a strong level of adhesion to wet tissue and is not compromised by preexposure to blood.

Pull-off adhesion testing (at 90°) was performed on an ADMET eXpert 7601 universal tester with fresh porcine epicardial tissue. The tissue was kept in phosphate-buffered saline to assure that it remained wet during testing. The pull-off procedure involved the controlled application of a preload (−1 N) to the adherent PGSU patch followed by grip separation at a rate of 8 mm/min, causing uniform patch detachment from the tissue surface. Adhesion force was recorded as the maximum force observed before adhesive failure, when a sharp decrease in the measured stress was observed.

In addition, in vitro burst pressure testing was performed on freshly explanted swine carotid arteries.

This work was supported by the Center for Integration of Medicine and Innovative Technology grant 11-315 and W81XWH-09-2-0001, the Technology Research Program grant of Boston Children’s Hospital, and NIH grant HL73647 to P.J.d.N. This work was also supported by the NIH grants GM086433 (to J.M.K.) and DE013023 (to R.L.). M.J.P. acknowledges the Portuguese Foundation for Science and Technology (fellowship SFR/BD/43013/2008) and the MIT-Portugal program (bioengineering focus area). N.L. acknowledges the German Research Foundation (DFG) for financial support (LA 2865/1-1).

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Researchers at LANL used an ADMET eXpert 7601 frame to run ASTM testing on sPVC and APU ester specimens to compare the properties of commonly used sPVCs with APU and investigate the better selection for nuclear material storage. 

For ASTM D412 testing, specimens of each bag were cut into dumbbell or dog-bone structures using Die D according to ASTM D412. Samples were mounted on GV-1T manual vise grips with serrated jaws and tested with the crosshead velocity of 3.84 mm/sec. The elongation and applied force were recorded automatically on MTESTQuattro software until the sample reached the break point.  ultimate tensile strength, breaking strength and maximum elongation to verify that the materials meet the requirements established for bag-out bags and to predict how the material will perform in use under normal and extreme conditions.

ASTM D4833 tests were run on the same system using the puncture test fixture designed per ASTM D4883. A circle-cut sample of 50.8 mm diameter was prepared and locked in the fixture. The steel rod applies force against the center of the sample with the crosshead velocity of 5 mm/sec. The resistance force was recorded automatically until the sample reaches the rupture point. 

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