D. Cayuela

Physico-chemical Analytical Techniques for Evaluation of Polyester Heatsetting

A polyester fabric has been heatset in an industrial plant over a wide range of temperatures (160–220°C) to study the influence of this variable in the modification of the fine structure produced by this thermal treatment. For this purpose, the weft of the fabric has been characterised through physico-chemical tests such as critical dissolution time, differential solubility and iodine sorption. The heatsetting effective temperature has been determined by differential scanning calorimetry and the crystallinity calculated from density measurements in a density gradient column. Both parameters have been correlated. The fine structure parameters deduced from the above mentioned techniques have been correlated with the effective temperatures of heatsetting.

Texturing, Stretching and Relaxation Behaviour of Polylactide Multifilament Yarns

Polylactide multifilament yarns were textured in order to be endowed with properties of natural staple fibre yarns for textile applications. Texturing promotes the formation of stable secondary links between the macromolecular chains. A polylactide 167/68 dtex multifilament yarn was textured under different conditions. Relaxation experiments at yield, strain softening, strain hardening and just before breaking were performed. The relaxation behaviour was studied by the application of the generalized Maxwell model. The initial stress induced when stretched, the final non-relaxed stress after relaxation and the stress relaxed at different times were determined. Variations in the relaxation behaviour were related to texturing conditions and stretching.

Microstructure variations of polylactide fibres with texturing conditions

The characterization of the microstructure of synthetic fibres is necessary to identify changes in properties produced by differences in the production variables. To this end, two physico-chemical tests (iodine sorption and differential solubility), which are easy and rapid to implement were employed to study the differences in the microstructure of polylactide false-twist textured multifilaments. The results enabled us to identify variations in microstructure induced by texturing conditions and were related to processing variables. These tests were compared with more expensive and complicated techniques to quantify crystallinity and orientation of filaments. Both tests enabled us to identify microstructure variations between substrates.

Contribution of the secondary crystallization to the overall crystallinity of heatset polyester

The crystallinity of poly(ethyleneterephthalate) has been determined by differential scanning calorimetry and by density. The results obtained by calorimetry show that the increment in the crystallinity due to the heatsetting treatment is produced by the increase of the crystallinity corresponding to the premelting endothermic peak.ZusammenfassungMittels DSC und mit Hilfe der Dichte wurde die Kristallinität von Poly-(ethylenterephthalat) bestimmt. Die mittels Kalorimetrie erhaltenen Resultate zeigen, daß die Zunahme der Kristallinität im Zusammenhang mit der Heißhärtungsbehandlung durch die Zunahme der dem endothermen Vorschmelz-Peak entsprechenden Kristallinität verursacht wird.

DETERMINATION OF THE HEATSETTING TEMPERATURE OF POLYESTER BY TMA

The determination of the effective temperature of the thermal treatment applied to polyester substrates in the textile process has been broadly studied by differential scanning calorimetry (DSC). In this investigation, the authors have studied the possibilities of the thermomechanical analysis (TMA) as a method for the determination of this temperature. For this purpose, fabrics of polyester heatset in an industrial plant between 160 and 210°C, have been analyzed by DSC and TMA. The good results obtained show the possibilities of this technique for the determination of the effective temperature of a thermal treatment.

Effect of processing and wearing on viscoelastic modeling of polylactide/wool and polyester/wool woven fabrics subjected to bursting

Polyester fibers (PET) are greatly used in textiles but depend on fossil fuel resources. Poly-(lactic acid) (PLA) is an aliphatic polyester that can be derived from 100% renewable resources. The load–extension plot of a polylactide fiber seems to be especially compatible with that of wool. Consequently polyester/wool 55/45 and polylactide/wool 55/45 yarns were spun using the Sirospun process and plain and twill woven fabrics were industrially produced. Washed and heat set fabrics were subjected to a conventional process of dyeing and decatizing. Fabrics were gradually worn by abrasion using a Martindale wear and abrasion tester. Using the bursting strength test, the viscoelastic behavior of the fabrics when multidirectional extended was simulated and modeled using a modified non-linear Maxwell model. The three steps of fiber decrimping and orientation, fiber stretching and maximum yield and breaking were analyzed. PET/wool fabrics show a more linear behavior than PLA/wool ones and the influence of weave, finishing and wearing on the viscoelastic behavior of PLA/wool fabrics were highly relevant when compared with that on PET/wool ones. It seems that when blended with PET, wool develops its felting effect during finishing and wearing, while when blended with PLA, the felting effect of wool is hardly developed due to the lower resistance of PLA to hydrolysis and its lower thermal stability. PLA fiber properties need to be improved probably through the development of new L-D lactide (PLDLA) copolymers of different ratios between components and molecular weights to reach the optimal desirable properties for the fiber.

Relationship between microstructure and properties of false-twist textured and stabilized polylactide. Part 2: physicochemical characterization, accessibility of the amorphous phase and dyeing behavior

Polylactide fibers (PLA), textured by false twist at different temperatures (135, 150 and 165℃) and draw ratios (1.30, 1.35 and 1.40) were stabilized by the application of a continuous thermal treatment at 100℃ and 50 m/min. The effect of thermal stabilization on the microstructure was determined by physicochemical tests such as iodine sorption or differential solubility. Iodine sorption and differential solubility are closely related to the crystallinity of the samples. Stabilization enhances crystallinity and orientation with the result that differences between the samples are diminished. Color value differences, albeit reduced, in some cases exceed the accepted limits. Color absorption is mainly dependent on the orientation and accessibility of the amorphous phase.

Relationship between microstructure and properties of false-twist textured and stabilized polylactide. Part 1: dimensional stability, mechanical properties and thermomechanical behavior

Polylactide fibers (PLA), false-twist textured at different temperatures (135, 150 and 165℃) and draw ratios (1.30, 1.35 and 1.40) were stabilized by a continuous setting treatment at 50 m/min and 100℃ using a specially designed chamber. The crystallinity and the orientation of the original textured filaments and those of the stabilized ones were measured. The effect of post setting on the dimensional stability, mechanical properties and thermomechanical behavior in accordance with the texturing conditions was studied. The relationships between crystallinity and the dimensional stability and between the orientation and both the relaxation shrinkage and the endset temperature of shrinkage were considered.

Effect of different dispersing agents in the non-isothermal kinetics and thermomechanical behavior of PET/TiO2 composites

ABSTRACT This work is based on the analysis of the influence of dispersing agents on the non-isothermal kinetics, thermomechanical behavior and dispersing action of PET/TiO2 nanocomposites. The influence of two montanic waxes and an amide wax used as dispersing agents in the nucleating effect of the nanoparticles is studied. The dispersing agents are the following: a) a partly saponified ester of montanic acids (PSEMA), b) an ester of montanic acids with multifunctional alcohols (MAWMA) and c) an amide wax based on N,N′-Bisstearoyl ethylenediamine (AW). The non-isothermal kinetics based on the Avrami method revealed that MAWMA and PSEMA favors the nucleating effect of the nanoparticles when are included in PET. Birefringence microscopy points out the good dispersing capacity of MAWMA and AW and the termomechanical analysis confirmed that the ester of montanic acids with multifunctional alcohols MAWMA shows the best dispersing properties and best promotes the nucleating effect of the TiO2 nanoparticles when used for PET/TiO2 nanocomposites production.

Effect of the Presence of an Ester of Montanic Acids With Multifunctional Alcohols in the Composites of Titanium Dioxide Nanoparticles With Poly (Ethylene Terephthalate) in Their Non-Isothermal Crystallization

The effect of the addition of an ester of montanic acid with multifunctional alcohols in the effectiveness of the dispersion and compatibility of TiO2 nanoparticles when included as filler in poly(ethyleneterephthalate) for composite production is studied through the study of the non-isothermal crystallization by differential scanning calorimetry (DSC). The application of the Avrami method enables to evaluate the compatibility and the level of dispersion/aggregation of the nanofiller in the poly(ethyleneterephthalate) by the analysis of the temperature and enthalpy of crystallization, the kinetic parameters and the half-crystallization time.