Dart impact resistance

EtO gas sterilization has declined in use because of its overall toxicity to operators, and polymers reactivity wdth (and surface adsorption of) the EtO gas. Testing has shown negative property changes in POs from EtO treatments. For example, repeated treatments have produced a 50% reduction in HOPE tensile modulus, lower dart-impact resistance, and lower ultimate tensile elongation. In similar testing vvdth PP, tensile yield modulus was reduced by 78% after only two EtO exposures [16-3],... 

Dart impact resistance of polyethylene blown film was improved by addition of nucleation agent. The nncleating agent was Hyperform HPN-20E (34% zinc stearate and 66% 1,2-cyclohexanedicarboxylic acid, calcium salt). ... 

D5420 Falling dart impact resistance (Gardner impact) see also D4226, D5628 —... 

ATS FAAR supplies the Fall-O-Scope Universal apparatus for free-falling dart impact resistance tests. The apparatus can be set to obtain the rate of energy absorption dnring the impact. The apparatus can be used to conduct tests to different specifications with computerized operation in the range 70°C-200°C. 

Minimum drop dart impact resistance, g ASTM D 1709 40-165 75-255 105-315 ... 

The use of PPA may eliminate melt fracture and surface defects which may result in an inproveMnt in the dart impact resistance. Process LLDPE with Dynamar PPA on LDPE Equipment ... 

Reeent work has shown that the use of up to 20% stearate coated ultrafine ground calcium carbonate in linear low density polyethylene (LLDPE) garbage bags increased the production rate by 50%, increased dart impact resistance fivefold, reduced cost and improved blocking, with no change in tensile or tear strength. 

ASTM D1709 - Free falling dart impact resistance. 

Figures. Effect of fiber length (Lv) on biaxial driven dart impact resistance of glass and glass-organic fiber reinforced PP at 25°C.

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.

To improve the end use performance and make the processability easy, control of MW and MWD as well as the use of.more than one comonomer has been reported for LLDPE [28]. Union Carbide s high MW-LLDPE with broad MWD is a 1-hexene-based resin, and its film provides superior (about 30-50% higher) tensile strength, puncture resistance, and dart impact strength than conventional 1-hexene-based resin, but with lower tear resistance in the transverse direction. The broad MWD makes the resin processability easy on the conventional extruder. 

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). 

We test the impact resistance of polymer plaques using the configuration shown in Fig. 8.8. We subject circular injection molded plaques to the shock of a falling weight with a hemispherical impacter. This test is also known as the Dart Drop Test . Samples can fail in a brittle or a ductile manner. Brittle samples often shatter. Ductile samples can split or a small disk may be punched out of their center. This test provides results that are analogous to those obtained from un-notched impact beam testing. 

ISO 7765-1, Plastics film and sheeting - Determination of impact resistance by the free-falling dart method - Part 1 Staircase methods, 1988. 

ASTM D 5628-96 Standard Test Method for Impact Resistance of Flat, Rigid Plastic Specimens by Means of a Falling Dart Tup or Falling Mass), pp. 1-10, American Society for Testing and Materials, Philadelphia, 1996. 

ISO 7765-2 1994. Plastics Film and Sheeting - Determination of Impact Resistance by the Free-Falling Dart Method - Part 2 Instrumented Puncture Test. 

ASTM D5628, Impact resistance of flat, rigid plastic specimens by means of a striker impacted by a falling dart (tup or falling mass), 1995. 

On its own, VLDPE should find use in applications requiring impact strength, puncture resistance, and dart drop resistance combined with flexibility. The drawdown characteristics of VLDPE allow for very thin films to be formed without pinholing. Soft flexible films for disposable gloves, furniture films, and high-performance stretch and shrink film are potential markets. 

MAJOR APPLICATIONS Major applications include blown and cast films for bags, shrink-wrap, packaging, and injection molding. Such films exhibit exceptional toughness, dart impact, and puncture resistance when compared to blown films of LDPE. Other applications include blow molding, pipe and conduit, lamination, coextrusion, rotomolding, and wire and cable coatings. There is considerable use of blends of LLDPE with LDPE in a wide variety of applications. 

Impact Resistance of Plastic Film by the Free-Falling Dart Method. Primary Film Test Method ASTM D1709 Additional Test Method ISO 7765-1. A weighted dart is dropped from a standard height onto a taut sample. Depending upon the expected impact strength of the test sample, either method A or method B is chosen. The method defines the dart size and the drop height for the dart. Test method A specifies a dart with a 38 mm diameter dropped from 0.66 m. Test method B specifies a dart with a 51 mm diameter dropped from 1.5 m. 

Dart Drop See Impact Resistance, Dart Drop... 

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