Relationships between mechanical properties and microhardness of polyethylenes

Lorenzo, Vicente; Pereña, José M.; Fatou, J. M. G.

doi:10.1002/apmc.1989.051720103

Cited by 57 publications

(25 citation statements)

References 24 publications

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“…The correlation between E and MH has been analysed before [4,11] and the relation: MH = a N E b has been proposed. For semicrystalline polymers, the key parameter is the crystallinity, as it has been reported for a broad range of polyethylenes, [4,10] including low, medium and high density ones.…”

Section: Stress-strain Behaviourmentioning

confidence: 99%

“…For semicrystalline polymers, the key parameter is the crystallinity, as it has been reported for a broad range of polyethylenes, [4,10] including low, medium and high density ones. Figure 6 shows that the results for the polyethylene sample studied in the present work lies in the general trend of crystalline polyethylenes.…”

Section: Stress-strain Behaviourmentioning

confidence: 99%

“…In addition, MH results can be related to mechanical parameters such as the elastic modulus and yield stress. [4] The dynamic mechanical thermal analysis (DMTA) gives information about the relaxation processes in amorphous and semicrystalline polymers, aiding to characterise the molecular motions in these materials. DMTA results have a great scientific interest in the elucidation and detailed description of the molecular processes taking place in these copolymers, in order to understand or explain their behaviour in different working conditions.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Stress-Strain Behaviour, Microhardness, and Dynamic Mechanical Properties of a Series of Ethylene-Norbornene Copolymers

Scrivani

Benavente

Pérez

et al. 2001

Macromol. Chem. Phys.

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Section: Stress-strain Behaviourmentioning

confidence: 99%

Section: Stress-strain Behaviourmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Stress-Strain Behaviour, Microhardness, and Dynamic Mechanical Properties of a Series of Ethylene-Norbornene Copolymers

Scrivani

Benavente

Pérez

et al. 2001

Macromol. Chem. Phys.

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“…10 The type of catalyst, glass transition temperature, T g , norbornene content as well as the prevailing sequences, determined by NMR investigations, 5 are listed in Table I. The molecular weights, M w , of the samples range from 1 to 2 × 10 5 , while their polymolecularity indices are around 2, as usual in metallocene polymers.…”

Section: Materials and Samplesmentioning

confidence: 99%

Norbornene–Ethylene Copolymers Studied by Non-Destructive Methods

Zamfirova

Misheva

Pérez

et al. 2002

Polym J

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ABSTRACT:Norbornene-ethylene copolymers with relatively high norbornene content, synthesised using different metallocene catalysts, were studied by Microhardness methods and Positron Annihilation Lifetime Spectroscopy. It has been established that plastic and elastic properties as well as free volume of the investigated materials do not depend linearly on the norbornene content since the different molecular structures, as a result of the various catalytic systems used, have also an important influence on those parameters. Vickers microhardness and plastic properties of the samples investigated are not sensitive to the quantity of ethylene blocks and are influenced predominantly by micromechanical properties of polymer chains. Vickers microhardness is not sensitive either to dimensions and quantity of the pores or to the free volume. On the other hand, long ethylene sequences are related to total microhardness, i.e., during penetration they contribute to the elastic deformation. The sizes, distribution and quantity of the nanopores have been determined and explained in relation to the structure of the norbornene-ethylene copolymers.KEY WORDS Norbornene-Ethylene Copolymers / Microhardness / Positron Annihilation / Nanopores / Free Volume / Norbornene-ethylene (N-E) copolymers possess a relatively high glass transition temperature and improved transparency, stability against chemical degradation, impact resistance, toughness, flexibility, water vapour impermeability and processability. That is why they are very appropriate and extremely useful for optical applications, electrical appliances, automotive parts, containers, bottles, tough films, compact disks, etc.Recently, there have been many articles devoted to the investigation of the structure and properties of norbornene-ethylene copolymers using standard investigative methods such as DSC, WAXS, DMTA, NMR, FT-IR and Raman spectroscopy. [1][2][3][4][5][6][7] The most interesting and disputable issue is the relationship between the copolymer microstructure (that is influenced by the type of catalyst used in synthesising N-E copolymers) and the norbornene content.In this work both Microhardness (MH) and Positron Annihilation Lifetime Spectroscopy (PALS) are also used as appropriate methods of investigation for this class of amorphous copolymers.Microhardness is not only a routine measurement of the material hardness, but in recent years it has developed as an investigation method and adequate tool for determining the structure and mechanical properties of polymeric materials. It has been established that Vickers microhardness is sensitive to many structural parameters as well as to the mechanical behaviour. Therefore, as a method, it occupies an intermediate place between typical structural investigative methods and classical mechanical measurements, and consequently acts as a connecting link between both. [8][9][10][11][12][13][14][15] Microhardness measurements carried out in the present work include that of Vickers microhardness (MHV), connected with the irrever...

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“…This equation is also fulfilled by many systems 56,59,60 in a very broad range of MH and E values: from thermoplastic elastomers to very rigid polymers. Figure 7 show a good linear relationship between MH and either E or E in those specimens with monoclinic crystalline structure.…”

Section: Mechanical Responsementioning

confidence: 97%

Structure and Mechanical Behavior of the Mesomorphic Form in a Propylene-b-Poly(ethylene-co-propylene) Copolymer and Its Comparison with Other Thermal Treatments

Arranz-Andrés

Benavente

Pérez

et al. 2003

Polym J

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ABSTRACT:Several thermal treatments have been imposed along processing to a poly[propylene-b-(ethylene-copropylene)] and their effect on structure, thermal characterization and mechanical response has been explored. Quenching in a dry ice/methanol bath after melting has allowed to obtain a mesomorphic form due to the existence of long isotactic polypropylene (iPP) chains within the block copolymer here studied. An exhaustive analysis of such a mesophase has been performed comparing its morphological details and mechanical properties with the rest of thermal treatments. A microspherulitic superstructure is found in this mesomorphic form which leads to the lowest values in mechanical parameters, such as storage and Young moduli as well as microhardness, compared to those exhibited by the other specimens with distinct thermal histories. However, the ductility of the mesomorphic structure is the highest one, owed to the non-existence of monoclinic crystallites. A phase transition is observed at around 90• C on heating, which suggests the transformation of this mesomorphic form to the monoclinic crystalline structure. KEY WORDS Poly(ethylene-co-propylene) / Mesomorphic Form / Monoclinic Crystallites /The crystallization behavior of isotactic polypropylene (iPP) is very complicated. The morphology and properties after crystallization depend upon thermal history and the detailed microstrucutre of the polymer molecules. The iPP chains adopt a 3 1 helical conformation when crystallized from the molten state. These helical chains can organize into several different spatial arrangements giving rise to three distinct polymorphs: α-monoclinic, β-hexagonal, and γ-orthorhombic forms, depending on the crystallization conditions and catalyst used. [1][2][3][4][5][6][7][8][9][10][11][12][13] Cooling from the melt at low or moderate cooling rates leads usually to the formation of the thermodynamically stable α-monoclinic crystalline lattice, being this α-form the most common one.Moreover, there is also a "mesomorphic" phase, which can be obtained by rapid quenching of molten iPP. The appearance of two broad peaks in the X-ray diffraction pattern is a characteristic of this quenched form. 14 The presence of broad, diffuse peaks in X-ray diffraction tends to suggest that the quenched structure is in a disorder state. These two peaks, however, exhibit an intermediate width between the crystal diffractions and the pattern found for a completely amorphous polypropylene. 15 Natta and Corradini 1 first pointed out that this form had an intermediate degree of ordering between the amorphous phase and the crystalline phase. They categorized it as smectic to indicate the presence of two-dimensional ordering, being better in longitudinal than in transverse chain direction. 16 However, the full evidence for the smectic phase in iPP has not been documented. The description of the mesophase can be quite confusing in the literature. In addition to the smectic phase, 1, 17 other investigators described the mesomorphic phase as paracrystalline, 18...

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Relationships between mechanical properties and microhardness of polyethylenes

Cited by 57 publications

References 24 publications

Stress-Strain Behaviour, Microhardness, and Dynamic Mechanical Properties of a Series of Ethylene-Norbornene Copolymers

Stress-Strain Behaviour, Microhardness, and Dynamic Mechanical Properties of a Series of Ethylene-Norbornene Copolymers

Norbornene–Ethylene Copolymers Studied by Non-Destructive Methods

Structure and Mechanical Behavior of the Mesomorphic Form in a Propylene-b-Poly(ethylene-co-propylene) Copolymer and Its Comparison with Other Thermal Treatments

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