Testing impact strength

Imide precursor, 317 Imide-terminated telechelics, 457 Impact strength tests, 243 Impet, 21... 

Overall, impact strength tests are measures of toughness or the ability of a sample to withstand sharp blows, such as being dropped. 

Notch Effect - The effect of the presence of specimen notch or its geometry on the outcome of a test such as an impact strength test of plastics. Notching results in local stresses and accelerates failure in both static and cycling testing (mechanical, ozone cracking, etc ). 

Many tests commonly applied to plastics in the form of solids, elastomers, coatings, and sealants may of course also be applied to cellular plastics. For example, notched impact strength tests can be applied to high-density structural foams, and it is very common to quote Shore hardness values for skin hardnesses of rigid and semirigid foam moldings. It is the intention here, however, to restrict the discussion to tests derived exclusively for plastics containing a cellular structure. 

Notched Izod impact strength tests have been conducted on the effect of fiber length in a nylon 6/6 compound reinforced with 50 wt% glass fiber. It shows that impact strength of reinforced TPs (RTPs) increases significantly, as fiber length is increased. Similar effects have been measmed with other fibers, such as aramid and carbon, and with other matrices, such as polypropylene and polyphenylene sulphide. 

Other impact strength tests that use gravity are the Gardner impact and Falling Dart tests. These are described in the following standards ... 

The tensile impact strength test, ASTM D1822, uses an apparatus very similar to that used for the Izod tests except that in this case the specimen is attached to the pendulum on one end and has a T-bar attached on the other end. When the pendulum drops the T-bar catches on the apparatus at its base, causing the specimen to undergo tensile impact. This test is typically performed on materials that are too elastic to fail in the Izod test. 

Relationships exist between Tg, T, and the type of termonomer introduced in the polymer and between Tg and the ductile to brittle temperature transition of polyketones in notched Izod or falling-weight impact strength test. For decene- or dodecene- containing grades Tm and Tg decrease simultaneously, while for propene-containing grades the opposite is observed (5). 

Figure 18.25 Examples of types of failure occurring in the falling weight impact strength test. Source Author s own files)...

Fig. 3.4. Solid dispersion of rubber particles in a glassy polymer matrix (sample prepared for the notched impact strength test).

Falling weight impact strength tests (FWIS) are possibly the most useful type of impact test as they can often be carried out on products and require little specimen preparation. End-use service performance can be more easily simulated, especially with the more advanced instrumented models [20]. This form of testing is popular for film, sheet and pipe, besides general plastic products. 

Tensile impact strength Impact strength tests permit no differentiation between specimens undergoing the test without failure. In this respect, the tensile impact strength test is superior, because other variables are eliminated (notch sensitivity, loss factor, and specimen thickness). It can be used... 

ThermoHaakeMinijet ram injection moulding machine was used to prepare samples for DMA and impact strength testing. The cylinder and mould temperatures were set 210°C and 40°C, respectively. 

Impact strength test for plastics bonding adhesives. 

Impact strength test for glass bonding adhesives. 

Charpy Impact Test. This test is conducted in a very similar manner to the Izod impact strength test. The only difference is the positioning of the specimen. Figure 2-41 illustrates one such setup. In this test the specimen is mounted horizontally and supported undamped at both ends. Only the specimens that break com-... 

Tensile Impact Test (ASTM D1822). The tensile impact strength test was developed to overcome the deficiencies of flexural (Izod and Charpy) impact tests. The test variables, such as notch sensitivity, toss factor, and specimen thickness, are eliminated in the tensile impact test. Unlike Izod-Charpy-type pendulum impact tests, which are limited to thick specimens only, the tensile impact test allows the user to determine the impact strength of very thin and flexible specimens. Many other characteristics of polymeric materials, such as the anisotropy and the orientation effect, can be studied through the use of the tensile impact test. 

Figure 13.14 Effects of glass fiber content on Izod impact strength. Test bars were molded at a mold temperature of 150 °C. Symbols represent glass fiber content in weight percent , 10 , 20 A, 30 , 40.

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