Transcrystallized interphase in thermoplastic composites

Thomason, James; Rooyen, Van

doi:10.1007/bf01197638

Cited by 184 publications

(98 citation statements)

References 13 publications

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“…8,12,13 On the other hand, although it has been specific morphology of the polymer in the transfound that the glass fiber increases the nucleation crystalline zone is expected to influence the adhedensity, 9 the existence of a transcrystalline zone sion at the interface, due to an increased nucleation density as well as the mechanical properties was not proved by microscopic investigations. 9,14 of the interphase due to a preferential orientation This article is the second part of a study of model of the lamellae.…”

Section: Introductionmentioning

confidence: 93%

“…The thickness of the critical crystal's coherent two-dimensional nucleus is given as 24 l* Å 2s e /DG u (8) where DG u is the difference between free energy for the polymer melt and crystal and can be approximated by DH u DT/T m . Based on DSC scans of isothermal crystallization (Fig.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…8,[9][10][11][12] Numerous results are also reported on glass fiber/iPP composites concerning transcrystallization phenomena, many of them being conIt is known that the presence of a solid surface flicting. It was recently shown that the transcrys-(substrate) in contact with thermoplastic polytalline zone appeared only if the glass fiber is mers during the crystallization from the melt genpulled out from the polymer melt or when shear eraly favors the heterogeneous nucleation 1,2 and stress is applied at given crystallization temperaoften a growth of the transcrystalline zone.…”

Section: Introductionmentioning

confidence: 99%

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Isothermal crystallization of iPP in model glass-fiber composites

Janevski¹,

Bogoeva‐Gaceva²

1998

J. Appl. Polym. Sci.

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Isothermal crystallization of iPP in model glass-fiber composites is studied by DSC, and the basic energetic parameters of crystallization are determined. Unsized untreated and thermally treated glass fibers are used in model composites to determine the role of the surface on nucleation and crystallization processes. Thermally treated glass fibers are found to exhibit a predominant nucleating effect as compared to unsized untreated ones, and the crystallization proceeds faster, resulting in lower values for the halftime of crystallization (10-120 s). The energy of formation of a nuclei of critical dimensions at a given T c is also lower, and it decreases as the content of the fibers in the composite increases. The surface free energy of folding, s e Å 140 1 10 03 J/m 2 , was determined for iPP in the composite containing 50% glass fibers, while for pure iPP, s e Å 170 1 10 03 J/m 2 was found.

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Section: Introductionmentioning

confidence: 93%

Section: Theoretical Backgroundmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Isothermal crystallization of iPP in model glass-fiber composites

Janevski¹,

Bogoeva‐Gaceva²

1998

J. Appl. Polym. Sci.

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“…23 The appearance of multiple peaks during the melting, observed by DSC analysis, is usually tallization phenomena. 8,9 Isotactic polypropylene (i-PP) is a polymorphic related to some of the following factors: different crystal structures, phenomenon of recrystallizamaterial with a high tendency to crystallize in numerous crystal modifications, such as monotion and perfection during fusion, and different crystal sizes. Besides the fact that the melting clinic (a), hexagonal (b), and triclinic (g).…”

Section: Introductionmentioning

confidence: 99%

Crystallization and melting behavior of iPP studied by DSC

Bogoeva‐Gaceva

Janevski²,

Grozdanov

1998

J. Appl. Polym. Sci.

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This article is a part of a study of model and bulk composites, based on isotactic polypropylene (i-PP) and glass (or carbon) fibers, produced from knitted textile preforms of hybrid yarns. First, we report the results on crystallization and fusion of textile-grade i-PP, used for the processing of hybrid yarns and the corresponding knitted fabrics. The kinetics of the crystallization process, in the dynamic and isothermal regime, was followed by DSC, and the results were analyzed by Avrami, Ozawa, and Harnisch-Muschik methods. Isothermal crystallization of i-PP was carried out at 388-400 K, and values for the Avrami exponent ranging from 1.93 to 4.39 were determined. The equilibrium melting temperature was determined by the Hoffman-Weeks method, and g Å 2.54 was found. Double melting peaks were observed both when the crystallization was performed at lower temperatures (isothermal regime) and at higher cooling rates (nonisothermal regime). A single melting peak appeared upon melting following isothermal crystallization at 400 K. The nonisothermal kinetics data showed that the peak crystallization temperature changes from 377 to 386 K as the cooling rate decreases from 20 to 3 K/min. Applying the Ozawa method, a value of the exponent n Å 2.33 was determined, which is in agreement with the results for isothermal crystallization at 391-400 K. The Harnisch-Muschik approach was also applied to compare the results for n, and a similar trend in the results of isothermal and nonisothermal crystallization was found, due to the predominant homogeneous mechanism of nucleation at lower cooling rates (lower isothermal T c ) in spite of being heterogeneous at higher cooling rates (higher isothermal T c ).

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“…As disadvantage of these Kevlar R and Nomex R fibers is their high cost. It is well known that fibers can act as a nucleating agent modifying the process of crystallization [4][5][6] provoking a reduction in the crystallization time. 7 On the other hand, a reduction in size and perfection of crystallites in composites compared with the isolated matrix has been pointed out in PET.…”

mentioning

confidence: 99%

Influence of the Type of Fiber on the Structure and Viscoelastic Relaxations in Composites Based on a Metallocenic Ethylene-1-octene Copolymer

Cerrada

Benavente

Zamfirova

et al. 2002

Polym J

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ABSTRACT:Several composites of a copolymer of ethylene and 1-octene, synthesized with a metallocene catalyst, have been prepared with a 5% in weight of different types of fiber. The effect of the fiber on the crystalline structure and on the viscoelastic response is analyzed. The role of the fiber on crystallite development is discussed based on WAXS, SAXS, optical microscopy and DSC experiments. The viscoelastic behavior is modified by incorporation of the fiber when compared with the plain copolymer. Thus, both the intensity and location of the γ, β and α relaxations are dependent on the introduction of the fiber. The β relaxation is assigned to the glass transition temperature, in agreement with the calorimetric results (DSC and MDSC) in the copolymer. Moreover, the stiffness is increased in the composites above the glass transition temperature of the copolymer, allowing the analysis of the viscoelastic behavior up to temperatures well inside the melting region of the copolymer crystals, and thus enlarging substantially the service temperature of these composites.KEY WORDS Ethylene-1-octene Copolymer / Glass Fiber / Kevlar R Fiber / Nomex R Fiber / Crystallinity / Diffraction Patterns / Relaxation Processes / The use of metallocene catalysts has allowed a very rapid development in the field of polyolefins. These catalysts present single-site characteristics (and very high activities) and thus all the sites produce nearly the same chain architecture, 1 leading to polymers with narrow molecular weight distributions, and, in the case of copolymers with α-olefins, the side branches are randomly distributed in the polymer backbone. If the comonomer content is high enough, around 4 mol% depending upon the catalyst system used, a material exhibiting dual characteristics of plastic and elastomeric behavior can be achieved.An enhance of the mechanical and thermal properties required for load bearing engineering applications can be achieved by the incorporation of disperse fibers into polymers. This change in the mechanical and thermal behavior is due to several factors, such as variation in the mobility of the macromolecules in the boundary layers, the orientation influence of the fiber surface, the different types of fiber-polymer interactions, as well as the effect of fibers on the structure of the polymers. 2, 3 Glass fibers are probably the most common of all reinforcing fibers for polymer matrix composites. Their principal advantages are their low cost and high strength. Kevlar R is one of the most important manmade organic fibers ever developed. Fibers of Kevlar R consist of long molecular chains produced from polyparaphenylene terephthalamide. The chains are highly oriented with strong interchain bonding leading to a unique combination of properties, making them very useful in a wide variety of industrial applications. Other kind of reinforcement frequently used are fibers of Nomex R that inhere in long rigid molecular chains produced from polymetaphenylene diamine. They do not flow or melt upon heating, provid...

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Transcrystallized interphase in thermoplastic composites

Cited by 184 publications

References 13 publications

Isothermal crystallization of iPP in model glass-fiber composites

Isothermal crystallization of iPP in model glass-fiber composites

Crystallization and melting behavior of iPP studied by DSC

Influence of the Type of Fiber on the Structure and Viscoelastic Relaxations in Composites Based on a Metallocenic Ethylene-1-octene Copolymer

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