Impact tests, coatings

Testing of Painted Products. The enhancement of paint adhesion is one of the principal functions of conversion coating (20—22). A group of tests based on product deformation is used to test the painted product. The appHance and cod-coating industries use the mandrel bend, the cross-hatch adhesion test, and the direct and reverse impact tests. Adhesion after a water soak is judged using a cross-hatch test performed on the exposed surface. 

Impact tests Such tests reveal the resistance of coatings to deformation and destruction by concentrated sudden stresses. They thus throw considerable light on the integrity of the metal-coating bond. Changes in adhesion through chemical reaction at the paint/metal interface will be reflected in the impact-test values. 

For impact tests, ASTM-02794, a ball of known mass was dropped a fixed height through a tube, impacting the coated metal panel. Indirect impact resistance is reported as the fraction of paint removable (pickoff) from the impact site when the panel is struck on the uncoated side. Direct impact resistance is reported as the pickoff at the impact site when the panel is struck on the coated side. Optimally, no coating is loosened by this test. 

In order to safely use Cyclonite for loading projectiles, the expl has to be desensitized to such an extent that its impact test value would be comparable to that of either PA or TNT. One of the ways to achieve desensitization of RDX is to coat the particles with wax or a less sensitive expl such as TNT. A major development during WWII was the development of binary, ternary and other expl mixts using the sensitive very powerful explosive RDX. Some of the compositions developed for military and industrial applications include ... 

After impact testing, the fractured surfaces were coated with a thin layer of gold prior to SEM examination. Observation of the fracture features was performed using a JEOL JX A-840 scanning electron microscope operated at 20 kV. 

ASTM D2794 Resistance of organic coatings to rapid deformation (impact test). 

In other high-temperature tests, Ryton polyphenylene sulfide coatings on aluminum will pass an 80 inch-pound reverse impact test after exposure in air at 600°F for eight days, or at 700°F for two days (Table VIII). 

At lesser rubber levels, heavy duty solventless coatings models based on dlethylenetrlamlne or fatty polyamide cures, showed elastomer-modification (10 phr rubber level) to advantage in Gardner impact, mandrel bend and corrosion-resistance testing (41). Impact testing (direct and reverse) gave 110 and 60 in-lbs, respectively for the rubber-modified fatty polyamide cured epoxy coating (14 days at R.T.), whereas a control formulation tested 10 in-lbs in each mode. 

Impact resistance of epoxy coatings, as determined by a reverse Gardner impact test, is enhanced by liquid polymer addition independent of functional type. Again, these results are consistent with both unpigmented and pigmented model coatings. Although... 

ISO 4646. 1989. Fabrics coated with rubber or plastics Low temperature impact test. 

The results of a tubular impact test are shown in Figure 11.9. Impact resistance of BDGDA coating was found to improve with the incorporation of AUA, which is attributed to the flexibility imparted by the AUA component (Hua and Hu 2000, Kumar et al. 2008, Spontak et al. 2000, Zielinski et al. 1996). This improvement may again be considered as corollary to decrease in Tg and gel fraction of coating with increase of the AUA content (Kumar et al. 2008). A noticeable improvement in impact resistance property of coating was observed only after a critical concentration of AUA (i.e., 40 phr). 

Rapid deformations are produced in impact tests (falling weight tests). A metal sheet coated on one side is deformed by a falling weight that has a hemispherical indentor. Deformation occurs directly or indirectly, i.e., the coated or the uncoated side of the sample is struck by the falling body and deformed (ISO6272). 

Izod impact tests at room temperature were performed on compression molded samples (50x13.0x3.0 mm ), having a notch of 0.5 mm deep and a tip radius of 0.25 mm. The fractured surfaces of the broken specimens were examined in a scanning electron microscope (SEM) after coating with Au-Pd by means of an evaporator. 

It seems, then, that epoxidized methyl esters of oleic, linoleic, and linolenic acid contribute equally to yellowing, taking into consideration die added amount of crosslinker. The observed yellowing with epoxidized methyl ricinoleate is rather poor, and the reason for fliat is not yet fully understood. For all of the model compounds under investigation, it can be concluded that the films show poor coating characteristics after heat-curing. The films are too brittle and do not resist the standard re-versed-impact tests. It is likely fliat epoxide functionalities between 1 and 3 per alkyl chain are too low to form flexible three-dimensional networks. 

K.-D. Bouzakis, N. Vidakis, T. Leyendecker, O. Lemmer, H.-G. Fuss and G. Erkens, Determination of fatigue behaviour of thin hard coatings using the impact test and FEM simulation. Surf Coat. Technol. 1996,86-87,467-471. 

Coating adhesion The film adhesion can be qualitatively assessed by Rockwell and scratch test methods. These test procedures do not always yield reliable results, due to limitations of the test procedures (Bouzakis et al. 2011a). The evolution of the inclined impact test renders possible the accurate and quantitative coating adhesion evaluatiOTi (Bouzakis et al. 2010b). 

Bouzakis K-D, Mirisidis I, Michailidis N, Lili E, Sampris A, Erkens G, Cremer R (2007) Wear of tools coated with various PVD films correlation with impact test results by means of FEM simulations. Plasma Process Polym 4(3) 301-310... 

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