Dart impact properties

Figure 12.15 demonstrates an opposite effect for dart impact properties. Here, the impact is normal to the orientation in parallel and perpendicular directions, allowing the impact point to be the crack initiator. The less orientation in the article thus provides greater impact strength. 

Tjong, S. C. et al. (1996). Morphological behaviour and instrumented dart impact properties of beta-crystalline-phase Polymer, Vol.37, Issue 12, pp. 2309-2316. 

Best Gardner and Instrumented Dart Impact Properties... 

See Table 14.40 for formulations that give the highest Gardner and instrumented Dart impact properties. Maximum predicted Gardner impact, 14.3 J, was obtained with 10 wt% mica, 67 wt% polypropylene, 20.0 wt% Exact 4033, 1.5 wt% Unite MP-1000, and 1.5 wt% Struktol TR-016. 

Tjong, S.C., Shen, J.S. and Li R.K.Y. (1996) Morphological behavior and instrumented dart impact properties of P-crystalline phase polypropylene. Polymer, 37, 2309-2316. 

Figure 5. Dart impact properties of glass fiber reinforced PPS.

Blending with LLDPE is used to upgrade the properties and improve the processing of conventional LDPE. For example, by adding 25% of ethylene—1-butene LLDPE resin with I2 of 0.5 to conventional LDPE resin, the dart impact strength of 75 p.m film is increased from 490 to 560 g, the puncture strength from 41 to 49 J /mm (770-920 ft-lbf/in.), and the tear strength from 43 to 63 N /mm (246—360 ppi). CompositionaHy uniform VLDPE resins are used in blends with HDPE, commodity LLDPE, and polypropylene (PP) (70,71,89). 

Toughness Dow Primacor copolymers have rugged physical properties. Ultimate tensile strength is comparable to that of LLDPE, while dart-impact strength is substantially greater,... 

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],... 

To evaluate this concern, LLDPE blown films have been fabricated with PPA levels two or four times those typically used. Evaluation of mechanical properties such as tear, tensile and dart impact lest indicated no positive or negative effect due to the PPA s presence. Given that the... 

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