Relaxation transitions in polypropylene

Бартенев, Г. М.; Aliguliev, R. M.

doi:10.1016/0032-3950(84)90050-9

Cited by 26 publications

(11 citation statements)

References 9 publications

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“…c relaxation is observed at about À60 C, and the origin is local motions in the amorphous phase. 9 b relaxation corresponding to the glass transition is observed approximately at 0 C and is cooperative motions of chains in amorphous phase. 10,11 a Relaxation, measured usually at temperatures between 50 and 100 C, is arising from local motions in the crystalline phase.…”

Section: Introductionmentioning

confidence: 91%

“…The local dynamics of chains in isotactic polypropylene (iPP) includes three main relaxations, usually labeled as α, β and γ in order of decreasing temperature. γ relaxation is observed at about −60°C, and the origin is local motions in the amorphous phase 9. β relaxation corresponding to the glass transition is observed approximately at 0°C and is cooperative motions of chains in amorphous phase 10,11.…”

Section: Introductionmentioning

confidence: 93%

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Poly(propylene) composite with hybrid nanofiller: Dynamic properties

Sarlin

Immonen

2012

J of Applied Polymer Sci

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Mechanical, impact, and relaxation properties of in situ synthesized carbon nanotubes-polyaniline (CNT-PANi) hybrid nanoparticle-filled poly(propylene) (PP) composites with or without an amphiphilic dispersing agent were investigated using tensile testing, notched Charpy impact testing, and dynamical mechanical testing methods. The reference material was MWCNT filled PP composite. Ethyl gallate (EG) was the dispersing agent which realizes high conductivity in PP composites with hybrid filler. Measured properties showed quite similar behavior of CNT-PANi hybrid and neat CNT filled composites. Addition of 20% EG in PP did not cause essential differences compared to the neat PP. When the dispersing agent was added in filler containing PP composites, remarkable effects were observed, especially in PP-hybrid composites. Mechanically, these materials had improved tensile properties, but they were brittle compared to the materials without dispersing agent. Dynamic mechanical analysis showed improvement in storage modulus, and in loss modulus the a transition was well observable.

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Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 93%

Poly(propylene) composite with hybrid nanofiller: Dynamic properties

Sarlin

Immonen

2012

J of Applied Polymer Sci

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“…A broad transition is detected with a maximum centered around −52°C in loss modulus and tan δ corresponding to γ relaxation which is generally attributed to local motions in the amorphous phase taking place at temperatures below T g [38,39]. The peak that appears around 17°C corresponds with β relaxation or glass transition and is characterized by a sharp drop in E'.…”

Section: Resultsmentioning

confidence: 99%

Bimodal polypropylene through binary metallocene catalytic systems: comparison between hybrid and mixed heterogeneous catalysts

et al. 2016

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Polypropylene with wider or bimodal molecular weight distribution is required for numerous applications since low molecular weight chains improve processability and high molecular weight fraction is required to get good mechanical properties. There are several routes to achieve a bimodal resin but the use of a binary catalytic system seems to be the most attractive, particularly with metallocenes combination. From a previous work two metallocenes were selected because they lead to polypropylenes with average molecular weights that differ in one order of magnitude. Two types of binary systems have been investigated, hybrid catalysts (two metallocenes loaded on the same support) and physical mixtures (two independent supported metallocenes that are introduced to the reactor and start the polymerization together), using different ratios, i.e., 25-75, 50-50, 75-25, at three reaction temperatures, i.e., 30, 50 and 70°C. Most of the binary catalytic systems lead to bimodal molecular weight distributions. Polypropylenes produced by mixed catalysts are greatly influenced by the most active catalyst, while in PP coming from hybrid catalysts, as there is a strong interaction between both metallocenes, each one contributes according to its presence in the hybrid catalyst. Therefore, properties of obtained bimodal polypropylenes are quite influenced by the ratio between both metallocenes.

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“…The γ relaxation is detected as a smooth drop of E' at low temperature between -150 ºC to -50 ºC (Figure 7a). This relaxation appears as a peak in the temperature-dependent variations of tan δ and E'' (Figure 7b and 7c) and is generally attributed to local motions in the amorphous phase taking place at temperatures below T g (26,27). Fig.…”

Section: Mechanical Propertiesmentioning

confidence: 89%

Morphology, thermal properties and mechanical relaxations of metallocene syndiotactic polypropylenes

et al. 2012

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The complex polymorphic behaviour of four syndiotactic polypropylene (sPP) samples have been analysed by means of DSC and WAXD techniques. Two samples (sPP1, sPP2) were synthesised via metallocene polymerization by using the ansa-zirconocene Ph2C(Cp)(9-Flu)ZrCl2 as catalyst. Finally, two additional specimens with different molar masses (sPP1-Fr1, sPP1-Fr2) were prepared from the most syndiotactic sPP1 sample by temperature gradient extraction. The WAXD analysis shows that together with the orthorhombic form I, form II can coexist in a variable but small proportion depending on both the chain features and the processing conditions. The relative contribution of the disordered and the ordered types of form I is also dictated by molar mass, configurational microstructure as well as processing conditions. The observed changes in the thermal properties as measured by DSC and in the mechanic-dynamical relaxations of the samples, on slowing the crystallisation rate down, can be rationalised in terms of two concurrent processes, namely the perfection undergone by the crystals and the segregation of the amorphous phase.

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Relaxation transitions in polypropylene

Cited by 26 publications

References 9 publications

Poly(propylene) composite with hybrid nanofiller: Dynamic properties

Poly(propylene) composite with hybrid nanofiller: Dynamic properties

Bimodal polypropylene through binary metallocene catalytic systems: comparison between hybrid and mixed heterogeneous catalysts

Morphology, thermal properties and mechanical relaxations of metallocene syndiotactic polypropylenes

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