Thermal properties relevant to the processing of PET fibers

Abstract

ABSTRACT:The thermal properties of poly(ethylene terephthalate) (PET) conventional fibers and microfibers are measured and compared to bulk samples. It is shown that the glass transition temperature (T g ) of the fibers can be monitored with modulated differential scanning calorimetry (MDSC). The T g region is about 30°C wide and shifted to approximately 110°C for conventional as well as for micro-PET fibers. The T g of these fibers is compared to the T g of cold-crystallized bulk samples. Upon crystallization, a shift and even a split up of T g is observed. The second T g is much broader and is situated around 90°C. This T g is related to the appearance of a rigid amorphous phase. In comparison, the mobility of the amorphous phase in fibers is even more restricted. The whole multiple melting profile observed on the fibers is the result of a continuous melting and recrystallization process, in contrast to bulk PET. The heat-set temperature is shown to trigger the start of melting and recrystallization. It is seen in the MDSC as an exotherm in the nonreversing signal and an excess contribution in the heat-capacity signal.

Variations in diffusion coefficient of disperse dyes in single PET fibres: monitored and interpreted by confocal laser scanning microscopy

“…A conventional fibre PET fabric (fabric quality 6460), supplied by Sofinal (Waregem, Belgium), was used and is described in detail elsewhere [13]. Warp and weft consist of the same 167/30 yarns (the yarn count is 167 dtex and the yarn consists of 30 filaments).…”

“…So far the diffusion coefficient (D) of dyes for fibres is commonly determined via the so called 'film roll method' in which a concentrationdistance profile is measured based on the concentrations of dye in adjacent layers of film of known thickness [3][4][5][6][7][8][9][10][11][12]. This however, disregards the appreciable differences in morphology between fibres and other materials like films of the same polymer [13,14]. Another approach described in literature [3,4,12,[15][16][17][18][19][20][21], determines the apparent diffusion coefficient by monitoring the total mass transport from the dyebath in the polymer during isothermal dyeing processes.…”

Dye–fiber interactions in PET fibers: Hydrogen bonding studied by IR‐spectroscopy

“…An amino group on the 1-position however brings about a decrease in fiber T g as can be observed for 1-amino anthraquinone, 1-amino, 4-hydroxy anthraquinone, and 1,4-diamino anthraquinone. Thus the plasticizing effect of the AQ1, AQ2, and AQ3 dyes as observed earlier 6,7 is related to the amino group on the 1-position in all of these dyes and not to the hydroxyl group in the 4-position.…”

“…5 The observed color differences between the conventional fiber fabric and the microfiber fabric suggest the causes not only to be the different fabric structure but also varying dyefiber interactions which are a function of dye concentration, dye structure, and fiber morphology. In earlier studies of dye-fiber interactions, the plasticizing effect was revealed of some anthraquinone dyes 6,7 and an interrelation was shown with the diffusion behavior. 8,9 In this article the same fabrics and dyes will be further investigated by infrared spectroscopy as to complement the understanding of the dye-fiber interactions.…”

“…It is how-ever crucial to study dye-fiber interactions in the fibers directly, as the morphology and interactions may be substantially different from bulk polymer systems. 6,7 It will be shown in this article that DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) offers a valuable easy applicable technique to study the dye-fiber interactions in fibers. To better understand the hydrogen bonding of the three main anthraquinone dyes studied in the PET fibers, some related model anthraquinone structures will be studied as well.…”