Phase changes in isotactic polypropylene measured by microhardness

Calleja, F. J. Baltá; Salazar, J. Martinez; Asano, Tsutomu

doi:10.1007/bf01730607

Cited by 48 publications

(23 citation statements)

References 9 publications

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“…The data of Table II show that the thickness of the b-crystals is slightly higher than that of the acrystals. Nevertheless, the crystalline hardness corresponding to the b-form is lower than the one exhibited by the a-crystals, H 27 In any case, the b-crystals represent, as a maximum, only a 13% of the crystalline material in the sample with a 20 wt % of clay. This means that the influence of the b-crystals on the H value is not enough as to take it into account in the hardness depression.…”

Section: 32mentioning

confidence: 90%

Nanostructure and micromechanical properties of reversibly crosslinked isotactic polypropylene/clay composites

Bouhelal

Cagiao

Khellaf

et al. 2009

J of Applied Polymer Sci

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Recent developments concerning the methodology used to prepare composites of iPP and nanoclays are reported. Conventional (reactive melt mixing) and in situ preparations were performed, and the structural properties exhibited by the composites are discussed. Results suggest that the nanoclay could exhibit partial and, maybe, total exfoliation within the composites. Adhesion between the polymeric matrix and the nanoclay layers is similar to that obtained after grafting. The experimental procedure used and the analysis performed by means of the wide-angle X-ray scattering and differential scanning calorimetry techniques permit to describe, at nanoscale level, the contribution of the nanoclay to the polymer composite system. The microhardness values of the iPP-clay composites depend on the clay content and on the preparation method, and linearly correlate, according to the additivity law, with the degree of crystallinity.

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Section: 32mentioning

confidence: 90%

Nanostructure and micromechanical properties of reversibly crosslinked isotactic polypropylene/clay composites

Bouhelal

Cagiao

Khellaf

et al. 2009

J of Applied Polymer Sci

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“…Hardness of polymers can also be correlated with many of their mechanical properties [8][9][10][11], which makes such measurements a fast and convenient method for material characterization. The microhardness technique has also been proved to detect polymorphic phase changes in polymers [12], and especially changes in polymer blends with composition [13,14].…”

mentioning

confidence: 99%

“…During the last two decades it was demonstrated [8][9][10][11][12][13][14][15], that microhardness technique as a nondestructive method, due to its simplicity and high sensitivity, makes it possible to derive relevant information about the structure of polymers. Relationships between microhardness and polymer crystallinity, crystal perfection, chain conformation and other structural parameters have been derived [8,10,15].…”

mentioning

confidence: 99%

Influence of molecular weight on the microhardness of poly(ethylene terephthalate)

Vanderdonckt

Krumova

Calleja

et al. 1998

Colloid & Polymer Science

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Poly(ethylene terephthalate) (PET) was annealed in vacuum at different temperatures (190-260°C) for different times (10 min-24 h) in order to examine the mechanical properties (microhardness) of PET samples with a wide range of molecular weights (10 000-120 000). Short annealing times result in a twofold decrease in mol. wt. due to hydrolytic decomposition. However, long annealing times give rise to a substantial molecular weight increase. It is found that microhardness (H) rises linearly with the degree of crystallinity obtained during up-grading of mol. wt. and its extrapolation leads to H-values of completely crystalline PET, H.#2 "405 MPa for samples with conventional mol. wt. and of 426 MPa for samples with mol. wt. higher than 30 000. It is shown that the increase of mol. wt. for each set of samples with a given range of degree of crystallinity also causes a slight increase of H. The influence of mol. wt. upon hardness is discussed in the light of the changes in the physical structure (crystallinity, crystal thickness) which is formed at given heat treatment conditions.

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“…For the nique to detect structure changes, including polypreparation of the blend, both the homopolymer morphic transitions in crystalline homopolymers PBT and PEE were cooled in liquid nitrogen and and copolymers. [21][22][23][24] finely ground. PBT was blended with PEE in a Following the microhardness behavior during weight ratio of PBT-to-PEE Å 51/49.…”

Section: Methodsmentioning

confidence: 99%

Microhardness under strain. III. Microhardness behavior during stress-induced polymorphic transition in blends of poly(butylene terephthalate) and its block copolymers

Boneva¹,

Calleja²,

Fakirov³

et al. 1998

J. Appl. Polym. Sci.

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ABSTRACT:The microhardness ( H) technique was recently applied to poly(butylene terephthalate) (PBT) and its multiblock copolymer of poly(ether ester) (PEE) type for examination of the stress-induced polymorphic transition. In the present study, these investigations are extended to blends of PBT and PEE. For this purpose, drawn and annealed with fixed ends at 170ЊC for 6 h in vacuum bristles of PBT-PEE, blends were characterized with respect to their microhardness at various stages of tensile deformation. H was measured under stress, with each step of deformation amounting 5%. The variation of H with strain (1) shows 2 sharp stepwise decreasing values (by 40%). Each step is defined in a relatively narrow deformation (1) range (2-5%) due to the stress-induced a r b polymorphic transitions arising in PBT crystallites. The first polymorphic transition (at 1 Å 2-3%) is assigned to the PBT crystallites of the homopolymer (homoPBT). The second transition (at 1 Å 25%) is associated to those crystals within the PEE copolymer. From the observation of two distinct transitions, separated by a deformation interval of 1 Å 20% it is concluded that (1) homoPBT and the PBT segments from PEE crystallize separately (no cocrystallization takes place), and (2) the 2 species of PBT crystallites are subject to the external mechanical loading, not in a simultaneous manner, but in a two-stage process. In the deformation range between the 2 transitions ( 1 Å 2-3% and 25%), it is pointed out that conformational changes are induced through stretching, mainly in the amorphous regions.

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Phase changes in isotactic polypropylene measured by microhardness

Cited by 48 publications

References 9 publications

Nanostructure and micromechanical properties of reversibly crosslinked isotactic polypropylene/clay composites

Nanostructure and micromechanical properties of reversibly crosslinked isotactic polypropylene/clay composites

Influence of molecular weight on the microhardness of poly(ethylene terephthalate)

Microhardness under strain. III. Microhardness behavior during stress-induced polymorphic transition in blends of poly(butylene terephthalate) and its block copolymers

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