Monoaxial drawing behaviour of isotactic polypropylene quenched at different temperatures

Candia, F. De; Romano, G.; Russo, R.; Vittoria, Vittoria

doi:10.1007/bf01425031

Cited by 21 publications

(7 citation statements)

References 15 publications

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“…In polymer technology the orientation of the crystalline and amorphous phases is highly relevant for the performance of polymeric materials in their applications. In turn, unidirectional cold drawing of polymeric films, performed to optimize their orientation, clearly shows that different initial structures can affect the final properties of the fibers. − …”

Section: Introductionmentioning

confidence: 99%

Influence of the Initial Morphology on the Elasticity of Oriented Syndiotactic Polypropylene

et al. 2004

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The influence of the initial phase composition and crystallite size on the mechanical properties and the elastic behavior of oriented syndiotactic polypropylene (sPP) was investigated. Two samples (A25 and B100) were crystallized from the melt respectively at 25 and 100 °C, obtaining the same crystalline forms but different morphologies, in terms of crystallinity, crystal dimensions, and phase composition. X-ray diffraction was used to determine the crystallinity and the crystal dimensions, whereas the vapor transport properties allowed to evidence and quantify the presence of an intermediate phase. Sample A25 shows smaller crystals, lower crystallinity, and a lower amorphous fraction but a larger mesomorphic component as compared to B100. The two samples were then stretched to a draw ratio of 7. They showed very different stress−strain curves, which appear to correlate with the initial structure. On releasing the tension both fibers undergo a large shrinkage, reaching λ = 4. The presence of the trans-planar form III and of the trans-planar mesophase characterize the fiber A25 at λ = 7 while upon relaxation only the trans-planar mesophase and a small fraction of an oriented helical polymorph are apparent. In the fully extended fiber B100 well-oriented form III and small amounts of a modestly oriented helical form were evidenced. The relaxed fiber B100 contains an essentially unchanged crystalline helical component along with the trans-planar mesophase. Stress−strain cycles of fibers A25 and B100 allowed the determination of the hysteresis curves and the permanent set. The stress−strain data were evaluated in terms of the Mooney−Rivlin equation and show for fiber B100, with a more substantial, less constrained amorphous fraction and larger crystals, a more traditional elastomeric behavior. The permanent set is similar for the two samples, but A25, characterized by smaller crystallites, more intimately connected with the amorphous and a larger intermediate phase component, shows both higher modulus and strain hardening. This features appear related to the limited extensibility of the chains forming the elastic network of A25 and to its capacity to crystallize under stress.

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Section: Introductionmentioning

confidence: 99%

Influence of the Initial Morphology on the Elasticity of Oriented Syndiotactic Polypropylene

et al. 2004

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“…In the case of isotactic polypropylene we found a correlation between Adt neck and sample morphology [8,9]; in the present case we observe an increase of zlZ neck on increasing the drawing temperature. This result confirms, as expected [10], that the sample morphology depends on crystallization temperature.…”

Section: Discussionmentioning

confidence: 62%

“…The yielding is well evident and a macroscopically visible neck is present~ at lower strains the deformation is mainly concentrated in the neck which propagates through all the sample. The neck propagates at ~constant, and therefore this condition allows to identify the deformation range characterized by the neck propagation; the width of the range is an approximate evaluation of the deformation in the neck zl~ neck [8,9].…”

Section: Discussionmentioning

confidence: 99%

Drawing and dynamic-mechanical behavior of syndiotactic polystyrene an introduction

Candia

Romano²,

Russo³

et al. 1990

Colloid & Polymer Sci

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The drawing behavior of syndiotactic polystyrene was analyzed at different temperatures. Amorphous films were used and, depending on drawing temperature, strain-induced or thermal-induced cold crystallization was observed. This phenomenon, when present, greatly affects the drawing behavior. The dynamic-mechanical behavior of drawn samples was analyzed, and the obtained results indicate that the glass transition is affected by drawing, and that the effect depends drastically on the drawing temperature. Particularly interesting is the dynamic behavior at high temperature where the elastic modulus is weakly affected by temperature also near the melting point.

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“…In particular, in iPP, Z neck seems to be related to the dimensions of the spherulites present in the initial undeformed film [10,11]. In Fig.…”

Section: Discussionmentioning

confidence: 86%

Drawing behavior of cross-linked isotactic polypropylene

Candia

Romano

Vittoria

et al. 1990

Colloid & Polymer Sci

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The drawing behavior of cross-linked isotactic polypropylene was analysed.The crystallinity and the composition of the crystalline phase are affected by cross-linking. Structural and topological features play a significant role in the drawing behavior. The yielding, the necking phenomenon, and the ultimate properties, i.e., stress and strain at the fracture, can be correlated with the sample structure. The general picture agrees well with Peterlin's model of cold drawing.

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Monoaxial drawing behaviour of isotactic polypropylene quenched at different temperatures

Cited by 21 publications

References 15 publications

Influence of the Initial Morphology on the Elasticity of Oriented Syndiotactic Polypropylene

Influence of the Initial Morphology on the Elasticity of Oriented Syndiotactic Polypropylene

Drawing and dynamic-mechanical behavior of syndiotactic polystyrene an introduction

Drawing behavior of cross-linked isotactic polypropylene

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