Impact strength Gardner

B. Gardner Impact strength of Pseudo-IPNs with and without Opposite Charge Groups... 

The crystallinity of isotactic polypropylene homopolymer, PP, however, leads to its well known brittle behavior at low temperatures or when impacted under conditions of stress concentration, i.e., in the presence of sharp notches. For example, the low temperature drop weight (Gardner) impact strength of unmodified PP is... 

Figure 3.105 Gardner impact strength vs. temperature for SABIC Innovative Plastics Noryl polypropylene ether and PS blend resins.

The relevant results of the tests are shown in Table 2. In our experience four parameters provide a very useful representation of the radiation tolerance of PP formulations. These are the color, tensile elongation at break, Gardner impact strength at 23°C, flexural deflection at peak load. 

Sample Number Radiation Dose, kGy Tensile Elongation at Break, % Gardner Impact Strength, inXlb Elexural Deflection at Peak Load, mm Color, Hunter b Units ... 

Figure 1. Sample 1 - Z-N Homopolymer. Gardner Impact Strength.

Figures. Sample 5 - Random Copolymer. Gardner Impact Strength.

Figure 9. Influence of Source on Post Irradiation Properties. Gardner Impact Strength.

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). 

The strength properties more often specified for plastics materials are (1) tensile strength and elongation, (2) flexural strength, (3) Izod and Gardner impact, and (4) heat deflection temperature under load. Our purpose here is not to describe each test in detail but to point out some of the known effects that colorants and other formulation ingredients can have on these properties. Table 22.1 lists the ISO and ASTM test methods for most of the physical properties, and ref. 1 (pp. 7-112) describes each of the methods in detail. Table 22.2 lists typical values of the above cite four properties for selected thermoplastics. 

Nelson investigated the relationship between density and physical properties, e.g., flexural modulus, Gardner impact, heat distortion, ten-sile/flexural strength, coefficient of linear thermal expansion, dynamic mechanical testing, and creep testing. The specific gravity of the SRIM obtained was changed from about 0.3 to 1.2. 

Impact strength vs. time was determined on solidified samples of the formulation that had been allowed to react from 30 min to 70 days at 135 °C. The impact strengths were measured with a Gardner impact tester on 1/2 in. thick samples. Impact strength values for all samples stabilized in the range 7-9 in.-lb. Hardness of the solidified samples was about 75 Shore D after 1 hr and increased to a maximum of about 80... 

Impact resistance Particularly relevant for PO packaging are Gardner (falling dart) impact, drop Impact strength for containers, and tear strength for films. 

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

Mineral Tensile strength (MPa) Tensile elongation (%) Tensile modulus, MPa (1% secant) Flexural modulus (MPa) Gardner impact U) Notched Izod impact strength 0/m)... 

Impact strength, Izod, notched, unnotched, Charpy Impact resistance, free-falling dart (Gardner impact)... 

Adhesive Acid Monomer Content Gardner Impact Energy, inelh Secant Flexural Modulus, psi Tensile Strength at Yield, psi... 

One of the most important properties—impact resistance—has been tested in various conditions of acceleration of the impact weight (acceleration being recorded on an oscilloscope). In this way, the falling rate, impact strength, and kinetic energy transmitted to the film can be calculated by the Gardner test [41, 42],... 

Typical Properties Density, g/cc Barcol hardness Tensile strength, psi Compressive strength, psi Gardner Impact, in. lb. 

---