Multiple endotherm melting behavior in relation to polymer morphology

Sweet, G. E.; Bell, James P.

doi:10.1002/pol.1972.160100707

Cited by 139 publications

(57 citation statements)

References 19 publications

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“…On the other hand, double melting peaks were observed for all SWNT-PS reinforced sPS nanocomposites as shown in Figure 2, B-F. This phenomenon is due to the competition between melting and recrystallization processes during the heating step [47]. Furthermore, a WAXD study near the melting region of about 270°C showed that the double endothermic melting behavior of sPS was caused not by a change in the crystalline form but by a recrystallization to a more perfect crystal [48].…”

Section: Thermal Behaviormentioning

confidence: 88%

Non-isothermal crystallization kinetics of syndiotactic polystyrene polystyrene functionalized SWNTs nanocomposites

Xiong

Gao²,

Li³

2007

Express Polym. Lett.

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Carbon nanotubes (CNTs) are unique nanostructured materials with remarkable physical, mechanical and electronic properties [1][2][3][4]. These properties make them attractive for applications in many scientific and technological fields such as electronic structures [5], polymer composites [6], and biological systems [7]. Among these potential applications, the prospect of obtaining high-performance CNT based polymeric nanocomposites has attracted the efforts of researchers in both academia and industry [8]. The combination of organic polymer components with CNT fillers in a single material has extraordinary significance for the development of advanced materials with remarkable mechanical, electrical, thermal and multifunctional properties [9][10][11][12]. Moreover, polymer/CNT nanocomposites challenge traditional filled polymers (loadings of 20 wt% or more) in many of these areas by providing similar physical enhancements but with as little as about 1 wt% addition of dispersed nanotubes [13]. Previous CNT based polymeric nanocomposites reports include increased modulus, impact strength, heat distortion temperature, and barrier properties with decreased thermal expansivity [14][15][16]. In addition, these nanocomposites are finding potential applications such as electrostatically dissipative materials and aerospace materials [17]. Currently, several processing methods, including melt mixing, solution process and in-situ polymerization [18][19][20] Abstract. Non-isothermal crystallization kinetics were characterized by using differential scanning calorimetry (DSC) analysis on neat semicrystalline syndiotactic polystyrene (sPS) and its nanocomposites with polystyrene (PS) functionalized full-length single walled carbon nanotubes (SWNT-PS), which was prepared by copper (I) catalyzed click coupling of alkyne-decorated SWNTs with well-defined, azide-terminated PS. The crystallization behavior of neat sPS polymer was compared to its SWNT based nanocomposites. The results suggested that the non-isothermal crystallization behavior of sPS/SWNT-PS nanocomposites depended significantly on the SWNT-PS contents and cooling rate. The incorporation of SWNT-PS caused a change in the mechanism of nucleation and the crystal growth of sPS crystallites, this effect being more significant at lower SWNT-PS content. Combined Avrami and Ozawa analysis was found to be effective in describing the non-isothermal crystallization of the neat sPS and its nanocomposites. The activation energy of sPS determined from nonisothermal data decreased with the presence of small quantity of SWNT-PS in the nanocomposites and then increased with increasing SWNT-PS contents.

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Section: Thermal Behaviormentioning

confidence: 88%

Non-isothermal crystallization kinetics of syndiotactic polystyrene polystyrene functionalized SWNTs nanocomposites

Xiong

Gao²,

Li³

2007

Express Polym. Lett.

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“…18 -21 Sweet and Bell 21 concluded that twin melting peaks of nylon polymers implies the existence of two crystalline structures: a structure (form I) that is less perfect and is recrystallizable upon heating, and another structure (form II) that does not recrystallize during melting. In the DSC experiment form I melted at a relatively low temperature and then recrystallized, resulting in a new crystalline structure that melted at about 258°C (peak I).…”

Section: Effect Of Acid Dyes On Formation Of Crystalline Structure Ofmentioning

confidence: 98%

Effects of acid dyes on crystallization and mechanical properties of melt-reprocessed nylon 66

Lin

Gowayed

1999

J. Appl. Polym. Sci.

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Nylon fibers dyed with different types of acid dyes were melt reprocessed using a compression-molding machine. The crystalline structure and mechanical properties of the melt-reprocessed nylon were experimentally evaluated. It was found that metal complex acid dyes showed much more distinct effects on the structure and mechanical properties of melt-reprocessed nylon than nonmetallized acid dyes. They decreased the crystallization rate of the molten nylon and reduced its crystallinity. They also reduced the imperfect form I structure in the crystalline region. Compressionmolded nylon samples showed inferior mechanical properties in the presence of metal complex acid dyes. The coordinate bonds between the Cr 3ϩ ions and amide groups are possibly formed in melt-reprocessed nylon, which could be the reason for the changes in the structure and properties of melt-reprocessed nylon.

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“…1 Double melting behavior has been reported for poly(ethylene terephthalate) (PET), [2][3][4] poly(butylene terephthalate) (PBT), [5][6][7][8][9][10][11] poly(phenylene sulfide) (PPS), [12][13][14][15] poly(ether ether ketone) (PEEK), 16 -20 and many other semi-crystalline polymers. Various interpretations and/or explanations on the melting behavior of these semi-crystalline polymers have been proposed.…”

Section: Introductionmentioning

confidence: 99%