Polyurethane Tensile test

FIG. 6—Effect of adhesive thickness on load at failure and location from which cracks grow for button tensile test. Specimens made of PMMA with a diameter of 1,5 in. The model adhesive was Thiokol Chemical Corp. Solithane polyurethane. Crack growth was observed and recorded with a video camcorder. 

Flexural strain reflects the flexibility of a material. Highly flexible resins like rubbery epoxy, polyurethane, and modified resins do not break even after a large deflection determination of ultimate flexural strength is impractical for them. The relevance of mechanical tests depends on the form in which the material is going to be used. If a material is to be used as a beam, then a flexural test is more relevant than a tensile test. 

First, the shape memory effect (SME) was quantified via the set of thermomechanical cychc tensile tests mentioned above. Figme 2.7 shows the SME of the segmented polyurethanes with varying HSC. It can be seen that the shape fixity decreases with an increase of HSC. When HSC < 35%, the shape fixity of the segment is over 94%, while when HSC > 40%, the shape fixity decreases abruptly. 

In the thermo-mechanical cyclic tensile tests, the shape recovery of the segmented polyurethanes occurs at + 20°C. To examine the influence of T on... 

As a type of smart material, precise control of the SME is essential for the application of SMPs. In the thermo-mechanical cychc tensile tests of the segmented polyurethanes, the third loading curve is close to the second loading curve. In other words, the segmented polyurethanes turn completely elastic after the first deformation. This led to enhancing the shape recovery of the segmented polyurethanes by a pre-deformation treatment. In this study, the segmented polyurethanes were extended to 120% of strain on the tensile tester at + 20°C. Afterwards, the specimens were removed from the tensile tester and kept at + 20°C for 15 minutes for shape recoveiy. Then the recovered specimen was viewed as a new sample to perform the thermo-mechanical cyclic tensile tests with 100% of deformation amplitude. 

The segmented polyirrethane without hard domains shows over 90% of shape recovery in the thermo-mechanical cyclic tensile tests with 50% of elongation. This suggests that the molecular interactions can also play the role of physical cross-finks and enable the segmented polyurethane to show the SME under some... 

Shape memory properties of T-type high performance shape memory polyurethane thermo-mechanical cyclic tensile tests... 

Keywords Organomodified layered Silicates, SEBS, polyurethane, tear strength, tensile tests... 

Priorconcomitant work on this problem at the Jet Propnlsion Laboratoi indicated that an elastomer based on the Thiokol Chemical Company s Solithane family of polyurethanes most nearly fulfilled these goals. Hence, one particular formulation of Solithane 113 was adopted as an interim standard. This is called GALCIT I. Its major defects are that the chemical structure is not sufficiently well defined, its properties change slowly with time, and its ultimate elongation in a uniaxial tensile test at 25 C is only about 7056, This means that it is an inadequate vehicle for large deformation studies,... 

Other tests are cited in ASTM 3574 and other standards, but they are of less importance in the context of how we will use them. Among parameters tested are resilience, fatigue/durability, flammability, and creep. A polyurethane devised to meet our primary objectives of density, tensile strength, compression, air flow, etc., will probably lead to values for these other properties that will have to be adjusted on a systems basis. 

The ultimate tensile strength and the modulus at various strains are always quoted in technical literature. These are very good quality control values and give an indication to the type (ether, ester, MDI, IDI) and nature of the prepolymer system used. These tests are also valuable in evaluating the chemical and aging effects on polyurethanes. Where polyurethanes are used in tension, the amount they are stretched is normally no more than 30%. The highest extension is on the order of 100%. 

Tensile properties are used in the evaluation of batches of material as well as in determining the aging effects on polyurethane. Currently, the time taken for the preparation and stabilization of the samples does not make this test ideal for a batch-to-batch real-time quality control tool. Testing is normally carried out to one of the following standards ... 

In tensile strength determinations, the material has to completely break through the cross-section, whereas the tear strength test indicates the resistance to the propagation of a defect, such as a nick, in the polyurethane. The way that elastomers tear under different conditions has led to a number of different tests. 

In peel tests, the polyurethane is bonded to a metal strip. The bonded area is 25 x 25 mm. The sample is conditioned, and an initial length of approximately 1.5 mm is stripped from the plate using a knife. The sample is mounted in a tensile strength machine and the polyurethane stripped from the plate. Figure 9.4 shows the sample configurations used. 

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