Influence of molecular weight on J-integral testing of polypropylene

Fukuhara, Naomichi

doi:10.1016/s0142-9418(98)00021-x

Cited by 12 publications

(14 citation statements)

References 15 publications

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“…The results state that the fracture parameters are also dependent on the molecular weight, especially the crack initiation resistance seems to be more sensitive. These results are in accordance with those presented by Fukuhara [19]. The higher the molecular weight, the higher are the crack initiation resistance and the tearing modulus.…”

Section: Tensile Propertiessupporting

confidence: 93%

“…The mechanical and fracture response of PP produced via catalysers is strongly influenced by the microstructure, especially the crystalline morphology [10][11][12][13][14][15][16][17][18][19]. The ultimate properties of these polymers depend principally on the degree of crystallinity, the size and shape of spherulites, the lamellar thickness and the crystalline orientation.…”

Section: Introductionmentioning

confidence: 99%

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Fracture toughness of controlled-rheology polypropylenes

Salazar¹,

Rodríguez²,

Navarro³

et al. 2007

E-Polymers

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Abstract:The rheological, thermal, tensile and fracture properties of controlledrheology polypropylene processed via organic peroxides have been evaluated. Different concentrations of di-tert-butylperoxide (DTBP) were used in this work. Both melt flow index and the crystallinity index increased slightly with the peroxide content while the melting temperature tend to decrease. This was attributed to the decrease in the molecular weight which mainly affects the amorphous region, especially the entanglement density of this semycrystalline polymer. As a consequence, the tensile stress and strain at break reduced as the peroxide content increased. The elastic-plastic response of the different polypropylenes at room temperature promotes the use of J-integral to determine the fracture toughness. A multiple specimens method was utilized. The crack initiation resistance and the crack propagation resistance were influenced by the molecular weight, decreasing as the peroxide content increased. The micromechanisms of failure were analyzed via scanning electron microscopy.

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Section: Tensile Propertiessupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Fracture toughness of controlled-rheology polypropylenes

Salazar¹,

Rodríguez²,

Navarro³

et al. 2007

E-Polymers

View full text Add to dashboard Cite

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“…The reduction in M W and the narrowing of MWD in CRPPs involve modification of structural parameters such as the crystallinity or the distribution and size of spherulite. There are many reports on the effect of these parameters on the mechanical properties of semicrystalline reactor‐made PPs on the mechanical properties [1, 20–30]. The ultimate properties principally depend on the degree of crystallinity, the size and shape of spherulites, the lamellar thickness, and the crystalline orientation.…”

Section: Introductionmentioning

confidence: 99%

“…Several authors have proved that the fracture strength decreases with the reduction in the molecular weight. The crack initiation and growth, as well as the final breakdown, are controlled by the amorphous interconnections among the spherulites, the entanglement density of which improves as the molecular weight increases [18, 23, 25, 26, 28, 30]. Gahleitner et al [7, 13], Xu et al [31, 32], and Yu et al [33] have also shown that the impact strength is increased for polymers with small spherulite size and low crystallinity degree.…”

Section: Introductionmentioning

confidence: 99%

“…The results revealed the same tendency as in the case of reactor‐made PPs, the fracture toughness reduces with the molecular weight decrease caused by the addition of peroxide. In any case, there are no explicit researches which tackle with the influence of the spherulite size and distribution on the fracture mechanics parameters of CRPPs, which allow us to extrapolate the results attained in reactor‐made PPs [21, 24–33]. Even more, most of the results found in the literature have been performed on thermally treated specimens with controlled spherulitic architectures and sizes [7, 13, 21, 25, 27–29, 31–34] but not on real injected or extruded samples, ready for engineering or industrial applications.…”

Section: Introductionmentioning

confidence: 99%

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Relating fracture behavior to spherulite size in conrolled‐rheology polypropylenes

Salazar

Rico

Rodríguez

et al. 2011

Polymer Engineering & Sci

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The influence of the spherulite size and distribution on the fracture toughness and Izod impact strength at different temperatures of controlled‐rheology polypropylenes with 0, 154, 402, and 546 ppm of peroxide has been evaluated. As the peroxide content increased, the average spherulite size was enhanced and the distribution width reduced. The fracture toughness and the Izod impact strength were lowered with the peroxide content due to the diminution of the amorphous interconnections among the crystalline regions. Porosity seems to control the fracture behavior for the materials with the highest peroxide content. Besides, a considerable loss of ductility was observed ahead of the stable crack growth zone. Below the glass transition temperature, the impact strength underwent a sudden drop with the temperature, more remarkable as the molecular was higher. The main mechanism of deformation and failure consisted on the formation of crazes, stretch out, and a final collapse through the interspherulitic zones. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

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Impact modified isotatic polypropylene with controlled rubber intrinsic viscosities: Some new aspects about morphology and fracture

Grein

Bernreitner

Hauer

et al. 2002

J of Applied Polymer Sci

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ABSTRACT:The influence of the molecular weight of the dispersed phase of ethylene-propylene rubber modified isotactic polypropylene (iPP/EPR) reactor blends was studied in a systematic way by varying their intrinsic viscosity (IV) from 1.7 to 6 dg/L while keeping the matrix melt flow rate (MFR) constant. Standard Charpy measurements were completed by a continuous analysis of the impact properties over a wide range of temperatures at fixed test speed. As expected, the higher the IV, the tougher the iPP/EPR blends. However, ductile-brittle transitions as key mechanical descriptors did not correlate linearly with M w , suggesting the macroscopic behavior of the blend to be controlled primarily by the morphology of the EPR particles. Moreover, strong correlations were found between impact mechanical properties, amount of stress-whitening, and strength of the molecular relaxations estimated from dynamical mechanical analysis.

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Influence of molecular weight on J-integral testing of polypropylene

Cited by 12 publications

References 15 publications

Fracture toughness of controlled-rheology polypropylenes

Fracture toughness of controlled-rheology polypropylenes

Relating fracture behavior to spherulite size in conrolled‐rheology polypropylenes

Impact modified isotatic polypropylene with controlled rubber intrinsic viscosities: Some new aspects about morphology and fracture

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