Potential and limits of dynamic mechanical analysis as a tool for fracture resistance evaluation of isotactic polypropylenes and their polyolefin blends

Abstract

Potential and limits of dynamic mechanical analysis (DMA) as a tool for fracture resistance evaluation of isotactic polypropylenes and their polyolefin blends are presented. A minimum of information about the materials under investigation is a prerequisite to interpret the DMA traces in a right way. Although DMA is, in general, a powerful method to rank materials in term of toughness, care should be taken with (1) nucleated materials (where both intensity and strength of molecular relaxations need to be taken into account in material evaluation) and with (2) visbroken (i.e., peroxyde treated) grades. Except for these cases, the strengths of the principal or secondary molecular relaxation evaluated by DMA and the Charpy impact toughness correlate quantitatively when all the grades of a series exhibit unstable crack propagation. When changes in the macroscopic mode of fracture or in blend morphology occur, only qualitative correlations remain possible.

Investigation into mechanical and microstructural properties of polypropylene manufactured by selective laser sintering in comparison with injection molding counterparts

“…According to the data compiled in Table 5, though no apparent difference is found in the intensity of tan δ, the I R of the IM specimen is 36% higher in comparison with that of the SLS specimen. It has been proved that a positive correlation is exists between the I R and toughness of materials [40]. Therefore, the higher I R of the IM specimen indicates a better toughness, which is in good agreement with the experimental tested result listed in Table 4.…”

“…I R is defined as the magnitude of β-relaxation which is determined by the integration area under the β-relaxation peak and calculated following the detailed procedure described by C. Grein et.al. [40]. The values of T g , tan δ max and I R are listed in Table 5.The glass transition of the IM specimen occurs at a lower temperature than that of the SLS specimen.…”

Influence of annealing on microstructure and physical properties of isotactic polypropylene/calcium carbonate composites with β-phase nucleating agent

“…As expected, annealing induces a significant increase of tan ı max and I R , indicative of the improved damping capacity. Generally, the impact toughness can be reflected by the magnitude of the ␤-relaxation (I R ) [58,59]. Anyway, the DMA results suggest that annealing is favorable to the improvement of the fracture toughness and damping capacity simultaneously.…”

“…DMA has also been proved to be a useful tool in estimating the fracture toughness of polymer and its blends [58][59][60]. The increase in tan ı max and I R is representative of, respectively, the maximum and total energy dissipated because of viscoelastic relaxation of iPP component.…”

Annealing induced microstructure and mechanical property changes of impact resistant polypropylene copolymer

“…Second, the  c -relaxation is greatly shifted to high temperatures, indicating the increased amount of rigid amorphous molecules and/or the increased degree of restriction for the rigid amorphous molecules, resulting in more energy requirement for the occurrence of  c -relaxation. Generally, the magnitude of -relaxation of iPP matrix (I R-iPP ), which represents the total energy dissipation because of viscoelastic relaxation, can be also used to reflect the fracture toughness of sample under the load condition [39] . Here, I R-iPP was calculated.…”