Stress‐induced crystallization of poly(ethylene terephthalate)

Abstract

Quenched amorphous films of poly(ethylene terephthalate) (PET) are stretched at temperatures less than Tg; changes in density, wide‐angle x‐ray diffraction, and small‐angle light scattering are observed. The density increase upon stretching is attributed to an increase in crystallinity accompanied by an increase in the intensity of somewhat diffuse wide‐angle x‐ray diffraction and of both VV and HV small‐angle light scattering patterns. The formation of oriented rodlike superstructure may be discerned from small‐angle light scattering. Annealing of these samples increases the crystallinity as measured from density and leads to an increase in the perfection of crystalline and supercrystalline structure as measured by wide‐angle x‐ray diffraction and small‐angle light scattering. The rodlike morphology changes to form spherulitelike aggregates as observed by small‐angle light scattering and light micrographs. A model is proposed to explain the observations. Studies are extended to stretching films of PET above their Tg and observing changes in birefringence, density, wide‐angle x‐ray diffraction and small‐angle light scattering as a function of elongation and stretching temperature. The formation of defomed spherulitelike superstructure may be discèrned from light micrographs. Results are compared with those obtained upon stretching films below Tg.

Reinforcement in melt-processed polymer–graphene composites at extremely low graphene loading level

“…In the neat polymer, fracture is known to be preceded by fibrillation and stress induced crystallization [45,46]. The fracture makes the fibrils visible and measurement of the characteristics of these fibrils can shed light on the influence of graphene on the fracture process.…”

Morphological and Mechanical Properties of Poly(ethylene terephthalate) Gel and Melt Films in Terms of the Crystal Lattice Modulus, Molecular Orientation, and Small Angle X-Ray Scattering Intensity Distribution

“…With the relationship S~3 = e~3 /o-, eq 12 is given by S~3 = cos 2 ¢ 3 S 33 + (l/2)(1-cos 2 ¢ 3 )(S 13 + S 23 ) = { cos 2 <p3 + (I /2)(1-cos 2 <p3) (13) According to an estimate by Hibi et al, 33 the compliances S 13 and S 23 can be represented as S13= -V31S33 (14) Thus, eq 13 can be rewitten as {cos 2 ¢ 3 -(l/2)(1-cos 2 </J 3 )(v31 +v 32 )}S 33 (15) The crystal lattice modulus E~ in the c-axis ( or fiber axis) is represented by using the apparent where the values of all the coefficients in eq 17 were given by Daubeny et al 24 Substituting the values into eq 17, we find ¢ 3 =9.77. This indicates that the c-axis are oriented predominantly in the X 3 axis and the mathematical evaluation by eq 9-16 is valid.…”

Mechanically Induced Gelation of a Kinetically Trapped Supramolecular Polymer

“…The solution was acidified using concentrated HCl (3 mL), and the aqueous phase was extracted with DCM (2 × 40 mL). The combined organic phases were dried using MgSO 4 N-(6-Methyl-4-oxo-1,4-dihydropyrimidin-2-yl)-1H-imidazole-1-carboxamide (7). 2-Amino-6-methylpyrimidin-4(1H)-one (1.0 g, 7.99 mmol) was dissolved in DMSO (10 mL), di(1H-imidazol-1-yl)methanone (1.68 g, 10.36 mmol) was added, and the mixture was stirred for 24 h at 80°C.…”

“…1−3 Particularly interesting are mechanical forces; the aligning of polymeric chains by stretching, 4 inducing symmetry breaking by stirring a solution during crystallization, 5,6 influencing the charge transport properties of semiconductors by shear stress during fabrication, 7 and the shear-induced gelation of a mixture of telechelic polymers 8 are examples that highlight their potential. The behavior of supramolecular systems is sensitive to external stimuli as well, and many elegant examples using a variety of external stimuli have been presented.…”