Influence of regioirregular structural units on the crystallization of isotactic polypropylene

Marigo, Antonio; Marega, Carla; Saini, Roberta; Camurati, Isabella

doi:10.1002/1097-4628(20010110)79:2<375::aid-app230>3.0.co;2-z

Cited by 15 publications

(11 citation statements)

References 28 publications

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“…On the other hand, it is known that the isotactic poly(propylene) and its copolymers with alpha olefins may exhibit polymorphism in its crystal structure, where the most prominent structures are the monoclinic (α), hexagonal (β), and orthorhombic (γ). The type of crystalline structure depends, among other factors, on the thermal treatment process in the crystallization step and the presence of nucleating agents . Recent studies have shown how these different crystalline structures in PP and its copolymers with alpha‐olefins can be favored and related this characteristic with their behavior and final properties.…”

Section: Introductionmentioning

confidence: 99%

Influence of the Polymeric Matrix and Thermal Treatment on the Properties of Polyolefin‐Graphite Nanosheets Nanocomposites

González

Quijada

Yazdani‐Pedram

et al. 2016

Macro Materials & Eng

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Homo and copolymers of metallocenic poly(propylene) with 1‐hexene and 1‐octadecene are used to prepare nanocomposites via melt mixing by using graphite nanosheets (GNSs) as filler. Different amounts of GNSs are used in order to study the influence of the filler on the thermal, mechanical, and electrical properties of nanocomposites. Significant changes have been observed in the crystallization temperature (Tc) of the nanocomposites. Thermogravimetric analysis shows improvement in thermal stability. Young's modulus and elongation at break of the nanocomposites are depended on the type of the matrix and the amount of GNSs. Materials with high flexibility are obtained in the cases of matrices based on copolymers even at high filler loading. Nanocomposites have become a semiconductor material reaching conductivity of 10−4 S cm−1. Two different thermal treatments have been applied in the preparation of the films by compression molding. X‐ray diffraction analysis shows the existence of polymorphism according to the thermal treatment applied.

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Section: Introductionmentioning

confidence: 99%

Influence of the Polymeric Matrix and Thermal Treatment on the Properties of Polyolefin‐Graphite Nanosheets Nanocomposites

González

Quijada

Yazdani‐Pedram

et al. 2016

Macro Materials & Eng

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“…The thermal treatment applied to polymers is important because the structure and mechanical properties strongly depend on the thermal history imposed during processing. In particular, iPP can crystallize into different crystalline structures according to the crystallization conditions 17. The development of the α, β, γ, or smectic forms depends on the crystallization conditions18, 19 and on the number of structural irregularities of the polymeric chain 20…”

Section: Introductionmentioning

confidence: 99%

“…The hexagonal β modification appears only under special crystallization conditions or in the presence of selective β nucleating agents. The orthorhombic γ form has been found in the case of low‐molecular‐weight iPP17, 22, 23 and in random copolymers of propylene and α‐olefins, favored when the proportion of the incorporated comonomer is increased 24. Moreover, the γ modification is especially favored in the case of iPP synthesized by metallocene catalysts because of the presence of errors homogeneously distributed among the different polymer chains 25…”

Section: Introductionmentioning

confidence: 99%

Metallocene copolymers of propene and 1‐hexene: The influence of the comonomer content and thermal history on the structure and mechanical properties

López-Majada

Palza

Guevara

et al. 2006

J Polym Sci B Polym Phys

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The relationships between the structure and properties have been established for copolymers of propylene and 1‐hexene synthesized with an isotactic metallocene catalyst system. The most important factor affecting the structure and properties of these copolymers is the comonomer content. The thermal treatment, that is, the rate of cooling from the melt, is also important. These factors affect the thermal properties, the degree of crystallinity, and therefore the structural parameters and the viscoelastic behavior. A slow cooling from the melt favors the formation of the γ phase instead of the α modification. Regarding the viscoelastic behavior, the β relaxation, associated with the glass‐transition temperature, is shifted to lower temperatures and its intensity is increased as the 1‐hexene content raises. The microhardness values are correlated with those of the storage modulus deduced from dynamic mechanical thermal analysis curves, and good linear relations have been obtained between these parameters. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1253–1267, 2006

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“…The presence of very short isotactic sequences, due to the random distribution of stereodefects and/or regiodefects in iPP samples synthesized by metallocene catalysts, favours the crystallization of the γ form 7–10…”

Section: Introductionmentioning

confidence: 99%

Crystallization of the γ form in random propylene‐ethylene copolymers

Marigo¹,

Causin²,

Marega³

et al. 2004

Polymer International

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Wide‐angle X‐ray scattering and differential scanning calorimetry measurements have been conducted on seven random copolymers of propylene with ethylene in order to study the γ phase formation as a function of the comonomer content. The lamellar morphology of the samples was also investigated by small‐angle X‐ray scattering. The content of the γ phase was found to go through a maximum with crystallization temperature and to increase with comonomer concentration, up to a point (ethylene ≥6.5 wt%) where the latter parameter became less influential. The multiple melting endotherms behaviour of the samples was studied by DSC and temperature‐controlled diffractometric techniques. The attribution of the DSC peaks to the different isotactic polypropylene polymorphs that form in these conditions was confirmed. The results obtained permitted us to ascertain that, in the experimental conditions chosen, some further formation of crystallites takes place during the quenching to room temperature after the crystallization isotherm. In this phase, the chains organize themselves in stacks with thin lamellae, forming a distinct population with respect to those formed on isothermal crystallization. The melting of the thinner lamellae determines a convergence of the two populations into just one, still retaining an organization in stacks, that gradually disappears until complete melting of the material. Copyright © 2004 Society of Chemical Industry

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Influence of regioirregular structural units on the crystallization of isotactic polypropylene

Cited by 15 publications

References 28 publications

Influence of the Polymeric Matrix and Thermal Treatment on the Properties of Polyolefin‐Graphite Nanosheets Nanocomposites

Influence of the Polymeric Matrix and Thermal Treatment on the Properties of Polyolefin‐Graphite Nanosheets Nanocomposites

Metallocene copolymers of propene and 1‐hexene: The influence of the comonomer content and thermal history on the structure and mechanical properties

Crystallization of the γ form in random propylene‐ethylene copolymers

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