Testing methods impact resistance

Organic coatings are commonly evaluated using salt water immersion, salt fog or spray, modified salt exposure tests (e.g., salt fog with added SO2), and various cyclic exposure tests. Humidity exposure and water immersion, and, for many applications, physical resistance tests (adhesion, impact resistance, etc.) are widely used preliminary tests. Standard methods for most of these tests are given in compilations of standard tests such as the Annual Book of ASTM Standards (16). Test methods have been extensively reviewed (e.g., 17-23). 

D 2794 Standard Test Method for Resistance of Organic Coatings to the Effects of Rapid Deformation (Impact)... 

Method of test for impact resistance of polymer-modified mortar... 

Source Reprinted from ASTM C 131, Standard test method for resistance to degradation of small-size coarse aggregate by abrasion and impact in the Los Angeles moch/ne. West Conshohocken, Pennsylvania, US ASTM International, 2006. With permission ( ASTM International). 

Methods of Test for Impact Resistance of Plastics and Electrical Insulating Materials, ASTMD 256-54T, ASTM Standards, Part 6, p. 182 (1955). Also ASTM D-256-56, ASTM Standards 1956. American Society for Testing Materials, Baltimore, 1955 and 1956. 

The most common test for impact resistance of plastics is the Izod pendulum method, ASTM D256, often used with rigid PVC. In this method, either the mass of the weight or the extent of arc can be used to specify failure. It is differentiated into notched and un-notched Izod the former, notably more severe, uses a sample with a cut notch of specific dimensions. With suitable instrumentation, Izod measurements can be extended to determination of low-temperature impact resistance. 

Tables 4—6 Ust ASTM methods used for the characterization of PB and PMP. A number of specialized methods were developed for testing particular articles manufactured from polyolefins several of these determine the performance of PB and PMP film, including the measurement of the film s dart impact strength and tear strength. Dart impact strength is measured by dropping a heavy dart with a round tip on a stretched film. Tear resistance, which reflects the film s resistance to tear propagation, is measured with the Ehnendorf tear tester. Two values for the tear strength are usually reported, one in the machine dkection of the film and the other in the transverse dkection. Pipes manufactured from PB are tested by pressurizing them internally with water the time-to-burst failure is determined at various temperatures (46). The standard test method for haze and luminous transmittance (ASTM D1003) is used for the measurement of PMP optical characteristics.

Water resistance test methods include AATCC 127 (hydrostatic pressure test), AATCC 42 (impact penetration test), and AATCC 35 (rain test). In the hydrostatic pressure test, a sample is subjected to a column of increasing water pressure until leakage occurs. The impact penetration test requires water to be sprayed on the taut surface of a fabric sample from a height of two feet. The fabric is backed by a blotter of predeterrnined weight, which is reweighed after water penetration. The rain test is similar in principle to the impact penetration test. 

Water-resistant fabrics protect against water penetration during a light or brief shower and pass AATCC Test Methods 22 and 42 (Impact Penetration Test). 

Testing. Various test methods are provided by ASTM (16). These iaclude pigment tests of importance such as chemical analysis, presence of oversize particles, oil absorption, particle size distribution, degree of dispersion, presence of soluble components, etc. Numerous tests are also given by ASTM for the properties of filled and unfilled polymers. These iaclude, for example, such properties as impact resistance, stiffness, viscosity, tear resistance, hardness, color, and electrical resistivity. 

Methods employed to determine the impact resistance of plastics include pendulum methods (Izod, Charpy, tensile impact, falling dart, Gardner, Dynatup, etc.) and instrumented techniques. In the case of the Izod test, what is measured is the energy required to break a test specimen transversely struck (the test can be done either with the specimen notched or unnotched). The tensile impact test has a bar loaded in tension and the striking force tends to elongate the bar (Chapter 5, Impact Strength). 

ISO 7765-2, Plastics film and sheeting - Determination of impact resistance by the free-falling dart method - Part 2 Instrumented puncture test, 1994. 

ISO 13957 1997 Plastics pipes and fittings - Polyethylene (PE) tapping tees - Test method for impact resistance... 

ISO 2897-1 1997 Plastics - Impact-resistant polystyrene (PS-I) moulding and extrusion materials - Part 1 Designation system and basis for specifications ISO 2897-2 2003 Plastics - Impact-resistant polystyrene (PS-I) moulding and extrusion materials - Part 2 Preparation of test specimens and determination of properties ISO 14631 1999 Extruded sheets of impact-modified polystyrene (PS-I) - Requirements and test methods... 

ASTM D3029, Test Method for Impact Resistance of Rigid Plastic S heeting or Parts by Means of a Tup (Falling Weight), Vol. 8.02, ASTM, Philadelphia, Pa., 1993. 

However, it is possible to compare the durability of some of the more common products by taking typical values for resistance to impact, scratching, and wear derived from appropriate test methods in BS EN 438 Part 2 (see Table X). 

Impact Test. Impact testing is of importance because adhesives, like most polymeric materials, are sensitive to high rates of application of force. The resistance of an adhesive to impact can be determined by ASTM D 950. This test is analogous to the Izod impact test method used for impact studies on materials. 

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