Effects of injection molding-induced morphology on the work of fracture parameters in rubber-toughened polypropylenes

J. Karger-Kocsis, D. E. Mouzakis

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

The effects of the injection-molding induced skin-core morphology on the fracture behavior of rubber-toughened polypropylene (RTPP) systems were studied by employing the essential work of fracture (EWF) method. RTPP with 31 wt% ethylene/propylene rubber (EPR) showed no skin-core structure after molding and the EWF approach worked well in this case. In contrast, RTPP with 10 wt% EPR exhibited a pronounced skin-core morphology: EPR depletion and enrichment was observed in the skin and core region, respectively. This morphology caused necking instead of crack growth in deeply double edge-notched (DDENT) specimens under tensile loading along the mold filling direction (MFD). The necking process not only was accompanied by a large scatter but also yielded highly unrealistic specific essential work of fracture (we) values. This skin-core structure was also the reason for an anisotropic EWF response of this system observed by loading the specimens both in longitudinal (L) and transverse (T) directions to the MFD. The failure sequence and its characteristics were studied by light microscopy (LM) and infrared thermography (IT). It was concluded that the EWF approach cannot be applied for RTPP with a prominent skin-core structure. Since yielding preceded the limited crack growth prior to necking in the loading direction for the DDEN-T specimen of RTPP with 10 wt% EPR, the yielding-related specific essential work (we,y) was used for toughness comparison. In case of RTPP with 31 wt% EPR, where yielding was less pronounced prior to the crack growth, the work of fracture until the maximum load was assigned to the yielding-related work of fracture (wf,y) used for computing we,y. The latter value seems to be closely matched to the plane-strain essential work of fracture value.

Original languageEnglish
Pages (from-to)1365-1374
Number of pages10
JournalPolymer Engineering and Science
Volume39
Issue number8
Publication statusPublished - 1999

Fingerprint

Polypropylenes
Rubber
Injection molding
Skin
Propylene
Ethylene
Crack propagation
Molding
Toughness
Optical microscopy
ethylene
propylene

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Materials Chemistry
  • Polymers and Plastics

Cite this

Effects of injection molding-induced morphology on the work of fracture parameters in rubber-toughened polypropylenes. / Karger-Kocsis, J.; Mouzakis, D. E.

In: Polymer Engineering and Science, Vol. 39, No. 8, 1999, p. 1365-1374.

Research output: Contribution to journalArticle

@article{d855b23a1ada4f20a1050c0c8c071b80,
title = "Effects of injection molding-induced morphology on the work of fracture parameters in rubber-toughened polypropylenes",
abstract = "The effects of the injection-molding induced skin-core morphology on the fracture behavior of rubber-toughened polypropylene (RTPP) systems were studied by employing the essential work of fracture (EWF) method. RTPP with 31 wt{\%} ethylene/propylene rubber (EPR) showed no skin-core structure after molding and the EWF approach worked well in this case. In contrast, RTPP with 10 wt{\%} EPR exhibited a pronounced skin-core morphology: EPR depletion and enrichment was observed in the skin and core region, respectively. This morphology caused necking instead of crack growth in deeply double edge-notched (DDENT) specimens under tensile loading along the mold filling direction (MFD). The necking process not only was accompanied by a large scatter but also yielded highly unrealistic specific essential work of fracture (we) values. This skin-core structure was also the reason for an anisotropic EWF response of this system observed by loading the specimens both in longitudinal (L) and transverse (T) directions to the MFD. The failure sequence and its characteristics were studied by light microscopy (LM) and infrared thermography (IT). It was concluded that the EWF approach cannot be applied for RTPP with a prominent skin-core structure. Since yielding preceded the limited crack growth prior to necking in the loading direction for the DDEN-T specimen of RTPP with 10 wt{\%} EPR, the yielding-related specific essential work (we,y) was used for toughness comparison. In case of RTPP with 31 wt{\%} EPR, where yielding was less pronounced prior to the crack growth, the work of fracture until the maximum load was assigned to the yielding-related work of fracture (wf,y) used for computing we,y. The latter value seems to be closely matched to the plane-strain essential work of fracture value.",
author = "J. Karger-Kocsis and Mouzakis, {D. E.}",
year = "1999",
language = "English",
volume = "39",
pages = "1365--1374",
journal = "Polymer Engineering and Science",
issn = "0032-3888",
publisher = "John Wiley and Sons Inc.",
number = "8",

}

TY - JOUR

T1 - Effects of injection molding-induced morphology on the work of fracture parameters in rubber-toughened polypropylenes

AU - Karger-Kocsis, J.

AU - Mouzakis, D. E.

PY - 1999

Y1 - 1999

N2 - The effects of the injection-molding induced skin-core morphology on the fracture behavior of rubber-toughened polypropylene (RTPP) systems were studied by employing the essential work of fracture (EWF) method. RTPP with 31 wt% ethylene/propylene rubber (EPR) showed no skin-core structure after molding and the EWF approach worked well in this case. In contrast, RTPP with 10 wt% EPR exhibited a pronounced skin-core morphology: EPR depletion and enrichment was observed in the skin and core region, respectively. This morphology caused necking instead of crack growth in deeply double edge-notched (DDENT) specimens under tensile loading along the mold filling direction (MFD). The necking process not only was accompanied by a large scatter but also yielded highly unrealistic specific essential work of fracture (we) values. This skin-core structure was also the reason for an anisotropic EWF response of this system observed by loading the specimens both in longitudinal (L) and transverse (T) directions to the MFD. The failure sequence and its characteristics were studied by light microscopy (LM) and infrared thermography (IT). It was concluded that the EWF approach cannot be applied for RTPP with a prominent skin-core structure. Since yielding preceded the limited crack growth prior to necking in the loading direction for the DDEN-T specimen of RTPP with 10 wt% EPR, the yielding-related specific essential work (we,y) was used for toughness comparison. In case of RTPP with 31 wt% EPR, where yielding was less pronounced prior to the crack growth, the work of fracture until the maximum load was assigned to the yielding-related work of fracture (wf,y) used for computing we,y. The latter value seems to be closely matched to the plane-strain essential work of fracture value.

AB - The effects of the injection-molding induced skin-core morphology on the fracture behavior of rubber-toughened polypropylene (RTPP) systems were studied by employing the essential work of fracture (EWF) method. RTPP with 31 wt% ethylene/propylene rubber (EPR) showed no skin-core structure after molding and the EWF approach worked well in this case. In contrast, RTPP with 10 wt% EPR exhibited a pronounced skin-core morphology: EPR depletion and enrichment was observed in the skin and core region, respectively. This morphology caused necking instead of crack growth in deeply double edge-notched (DDENT) specimens under tensile loading along the mold filling direction (MFD). The necking process not only was accompanied by a large scatter but also yielded highly unrealistic specific essential work of fracture (we) values. This skin-core structure was also the reason for an anisotropic EWF response of this system observed by loading the specimens both in longitudinal (L) and transverse (T) directions to the MFD. The failure sequence and its characteristics were studied by light microscopy (LM) and infrared thermography (IT). It was concluded that the EWF approach cannot be applied for RTPP with a prominent skin-core structure. Since yielding preceded the limited crack growth prior to necking in the loading direction for the DDEN-T specimen of RTPP with 10 wt% EPR, the yielding-related specific essential work (we,y) was used for toughness comparison. In case of RTPP with 31 wt% EPR, where yielding was less pronounced prior to the crack growth, the work of fracture until the maximum load was assigned to the yielding-related work of fracture (wf,y) used for computing we,y. The latter value seems to be closely matched to the plane-strain essential work of fracture value.

UR - http://www.scopus.com/inward/record.url?scp=0032689777&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0032689777&partnerID=8YFLogxK

M3 - Article

VL - 39

SP - 1365

EP - 1374

JO - Polymer Engineering and Science

JF - Polymer Engineering and Science

SN - 0032-3888

IS - 8

ER -