Heat-setting Temperature Research Articles

Shrinkage behavior after the heat setting of biaxially stretched poly(ethylene 2,6‐naphthalate) films and bottles

AbstractAmorphous preforms of poly(ethylene 2,6‐naphthalate) (PEN) were biaxially drawn into bottles up to the desired volume under industrial conditions. These bottles were used to characterize the shrinkage behavior of the drawn bottles with or without heat treatment and to study structural variations during heat setting. During drawing, a rigid phase structure was induced, and the amount of the induced rigid phase structure was linearly related to the square root of the extra first strain invariant under equilibrium conditions. During the production of these bottles, this equilibrium was not attained because of high stretching conditions and rapid cooling after stretching. The structure after orientation contained a rigid amorphous phase and an oriented amorphous phase. The shrinkage behavior was a function of the temperature and time of heat setting. Long heat‐setting times, around 30 min, were used to characterize the possible structural variations of the oriented PEN after heat setting at equilibrium. Under the equilibrium conditions of heat setting, the start temperature of the shrinkage was directly related to the heat‐setting temperature and moved from 60°C without heat treatment up to a temperature of 255°C by a heat‐setting temperature of 255°C; this contrasted with poly(ethylene terephthalate) (PET), for which the start temperature of shrinkage was always around 80°C. For heat‐setting temperatures higher than 220°C, the structural variations changed rapidly as a function of the heat‐setting time, and the corresponding shrinkage of the heat‐set samples sank below 1% in a timescale of 30–60 s for a film thickness of 500 μm. The heat treatment of the oriented films taken out of the bottle walls with fixed ends stabilized the induced structures, and the shrinkage of these heat‐set films was zero for temperatures up to the heat‐setting temperature, between 220 and 265°C, if the heat‐setting time was sufficient. According to the results obtained, a heat‐setting time of 30 s, for a film thickness of 500 μm, was sufficient at a heat‐setting temperature of 255°C to stabilize the produced biaxially oriented PEN bottles and to take them out the mold without further shrinkage. During the drawing of PEN, two different types of rigid amorphous phases seemed to be induced, one with a mean shrinkage temperature of 151°C and another rigid amorphous phase, more temperature‐stable than the first one, that shrank in the temperature range of 200–310°C. During heat setting at high temperatures, a continuous transformation of the less stable phase into the very stable phase took place. The heat‐set method after blow molding is industrially possible with PEN, without the complicated process of subsequent cooling before the molds are opened, in contrast to PET. This constitutes a big advantage for the blow molding of PEN bottles and the production of oriented PEN films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1462–1473, 2003

Polyester Fiber and Microfiber Structure by Critical Dissolution Time

A polyester microfiber and two classic fibers from the same manufacturer are examined using the critical dissolution time in phenol. In order to characterize the structures, we subject the yarns to a heat setting process at different temperatures. The monofilaments are initially tested at constant phenol temperature. The results show that the microfiber has a structure allowing good diffusion of the solvent. This property remains true even after heat treatment. On the other hand, the classic fibers show a similar behavior. Measurements of crystallinity by x-ray diffraction show that the microfiber and the circular filament are very close. This indicates that super-drawing induces the creation of longitudinal crystal zones, which do not overlap very much. Finally, the activation energy confirms this assumption. The energy barrier of the microfiber remains weak despite its increase according to the heat setting temperature.

Shrinkage behaviour of uniaxially drawn poly(ethylene 2,6-naphthalate) films

Amorphous films of poly(ethylene 2,6-naphthalate) (PEN) were drawn isothermally at 145°C up to the desired draw ratios mainly to study structure formation during uniaxial drawing by differential scanning calorimetry and to characterise the shrinkage behaviour of the drawn films with or without heat treatment. During drawing, a rigid phase structure is induced and the amount of induced rigid phase structure is linearly related to the square root of the extra first strain invariant. The stress–strain curves are characterised by a necking behaviour and the end of the yielding or necking is reached when the amount of induced rigid phase is attaining 50%. The stretching behaviour of PEN is characterised more by the strain induced rigid phase formation (SIRP) than by the stress or strain induced crystallisation. The shrinkage behaviour is characterised by two regimes. A first one for draw ratios below the necking behaviour where the films shrink back to their original length for temperatures between 100 and 140°C with a mid-value of 120°C, corresponding to the glass transition temperature of the amorphous phase. The second regime, for draw ratios above the necking behaviour is characterised by a shrinkage behaviour for temperatures between 120 and 160°C, with a mid-value of 140°C, corresponding to the transition temperature of the induced rigid phase structure. In this regime, the films never shrink back below the draw ratio after necking and a linear relation between the initial draw ratio and the final draw ratio after shrinkage is obtained. A heat treatment of the oriented films with fixed ends stabilises the induced structures and the shrinkage of these heat-set films is zero for temperatures up to the heat-setting temperature.

Influence of a Quaternary Ammonium Surfactant on Alkaline Hydrolysis of Heat-Set Poly( ethylene Terephthalate) Fibers

The hydrolytic behavior of heat-set poly ( ethylene terephthalate) (PET) fibers is compared in the presence and absence of a quaternary ammonium compound, do decylbenzyldimethylammonium chloride (DBDMAC). Alkaline hydrolysis without DBDMAC depends on the heat-setting temperature, showing a minimum weight loss at around 140°C and becoming more marked with increased NaOH concentration, hydrolysis temperature, and time. Alkaline hydrolysis is accelerated by DBDMAC for all PET fibers over the whole range of heat-setting temperatures. The fibers set at lower temperatures, however, have much larger increases in weight loss than those set at higher temperatures by alkaline hydrolysis in the presence of DBDMAC. The rate en hancement of alkaline hydrolysis by DBDMAC decreases with increased heat-setting ' temperature or degree of crystallinity of the fiber, and may preferentially occur in the amorphous regions of the fiber.

Effect of Heat-Setting Temperature on Alkali Hydrolysis of Poly ( ethylene Terephthalate) Fibers

Poly(ethylene terephthalate) (PET) fiber was heat set at 100 to 220°C and then hydrolyzed with 10% aqueous sodium hydroxide solution at 90°C for 60 and 120 minutes. Weight loss from the alkali hydrolysis initially decreased with increased heat- setting temperature up to 140°C and then increased at temperatures above 140°C. This phenomenon is similar to those with hydrazine treatment and with disperse dyeing of heat-set PET fibers and can be attributed to changes in the fine structure, especially in the amorphous regions of the fiber, caused by heat-setting treatment at different temperatures. Crystallinity and disperse dye uptake for the hydrolyzed PET fiber increased with hydrolysis, indicating differences in the fine structure from the outer to the inner regions of the fiber.

Dependence of Alkali Hydrolysis of Poly(ethylene terephthalate) Fibers on Temperature of Heat Setting in the Unstressed State.

Two kinds of poly (ethylene terephthalate) fibers, regular and partially oriented yarns, were heat set at 100°C-220°C in the unstressed state and then alkali hydrolyzed with 10% aqueous NaOH solution at 90°C. The rate of hydrolysis of the fibers with alkali was found to depend on heat setting temperature, i.e., weight loss initially decreased with increasing heat setting temperature up to 140°C and then increased at high temperatures. Shrinkage, disperse dyeing property, crystallinity and X-ray diffraction patterns were also measured with respect to the changes in the fine structure of fiber during heat treatment and alkali hydrolysis.

Effect of Heat-Setting Temperature on the Hydrazine Treatment of Poly (ethylene Terephthalate) Partially Oriented Yarn

Poly (ethylene terephthalate) partially oriented yarn (PET POY) was heat set at 100 to 220°c in a fixed state and then treated with hydrazine. Although crystallinity of the heat-set PET POY increased with increased heat-setting temperature, weight loss from the hydrazine treatment initially decreased at a temperature up to 120°c and subsequently increased above 120°c. The hydrazinolyzed POY fiber is dyeable with acid dyes because of the hydrazide groups incorporated by hydrazinolysis. Nitrogen content and dye exhaustion with CI acid orange 7 showed trends similar to the weight loss of the hydrazinolyzed POY fibers. On the other hand, the dyeability of the hydrazinolyzed POY fibers with CI disperse violet 1 was lower than that of the untreated fibers. Many cracks appeared on the surface of the hydrazinolyzed fibers, and they were smallest on the fibers that were heat set at 120°c.

Effect of heat-setting temperature on the hydrazine treatment of poly(ethylene terephthalate) fiber.

Poly (ethylene terephthalate) (PET) filament yarn was heat-treated at 100°C to 220°C for 10min under fixed state in air, and then treated with a 40% aqueous hydrazine monohydrate solution at 60°C for 3, 4, and 5h. Effect of the heat-setting pretreatment on the hydrazine treatment of PET fiber was investigated on the basis of weight loss, dyeing property, and morphological change. Weight loss by the hydrazine treatment decreased with the increase of heat-setting temperature up to around 160°C, and it increased again at temperatures higher than 160°C, as is the same behavior in dyeing of the heat-set PET fiber with disperse dyes. It is well known that the hydrazine treatment incorporates hydrazide groups in PET fiber and the fiber is dyed with acid dyes. Dye exhaustion curve with C. I. Acid Orange 7 showed a minimum at a heat-setting temperature of 160°C. Many cracks were produced perpendicular to the fiber axis by the hydrazine treatment and the effect was the smallest at a heat-setting temperature of 160°C. Crystallinity of the heat-set PET fiber was increased considerably by the hydrazine treatment. It is considered that the hydrazine treatment takes place mainly in the amorphous region of the PET fiber.

Effects of Commercial Heat Setting on the Structure and Properties of Polyester Carpet Yarn

Polyester carpet yarn is heat set during the production process in order to impart structural stability. Although batch (autoclave) and continuous (Superba TVP and Suessen GVA ) heat setting methods are used, the continuous processes are prevalent and constitute a greater part of this study. Commercial heat setting equipment and settings are used here because previous works were the results of laboratory studies. The primary technique applied in this study to determine the microstructural features of polyester is x-ray diffraction. Crystallization and crystallite melting temperatures from differential thermal analysis ( DTA ) and colorimetric determinations of initial rates of dyeing are also measured to provide additional data for interpreting the results, and tensile properties of the yarns are reported as well. X-ray and DTA results indicate no significant increases in the degree of crystallinity of yarns heat set by the Superba TVP method, while crystallinity increases with in creasing temperature for samples heat set by the Suessen GVA method. Crystal size increases for samples heat set by either of the continuous methods. Although x-ray determined crystallinity measures are significantly different at different levels of tem perature and dwell time, there are no significant differences in heat of fusion values obtained from DTA with changes in heat setting temperatures and dwell times. Te nacity, percent elongation, and work to break increase as a result of heat setting for samples set using the Superba TVP, autoclave, or Suessen GVA equipment, while the initial modulus decreases compared to a non-heat set sample.

Rheological properties of wheat gluten

Glutens were prepared from four wheat varieties (Kadet, Timmo, Extrem, San Pastore), which perform very differently in cereal products. The dynamic rheological and tensile properties of the glutens were measured by: (i) small angle oscillatory deformation of hydrated glutens in the temperature range 25–100 °C using a Rheometrics mechanical spectrometer to determine dynamic storage (G′) and dynamic loss (G″) moduli; and (ii) large deformation tensile measurement at ambient of heat-set glutens using an Instron Universal testing instrument to measure breaking stress, breaking strain and tensile modulus. The dynamic storage modulus (G′) of hydrated gluten was observed to be wheat variety dependent. When hydrated gluten was heated, G′ decreased steadily until ∼60 °C, when it began to increase, and at approximately 90 °C it increased dramatically. Oxidizing agents increased the dynamic storage modulus (G′), while the use of reducing agents led to a large decrease in G′ and a smaller decrease in loss modulus (G″) resulting in an increase in tan δ (i.e. reduced elasticity). Large deformation tensile properties were dependent on both water content and heat-setting temperature. For heat-set gluten the tensile modulus decreased with increasing water content. The decrease was greater than if water acted solely as a network diluent and suggests that it affects the mobility and interactions of the proteins. Maximum values for the modulus occurred after heat-setting the gluten at approximately 130 °C. Oxidants produced a lower modulus, and particularly a lower breaking stress, while reducing agents caused a dramatic loss of gluten structure prior to heat-setting by reduction of disulphide links. Interestingly, after heat-setting, there appeared to be some reformation of network structure.

Effects of Heat Setting on Tensile and Dye Sorption Characteristics of Anionic Modified PET-A Comparison With Normal PET

Anionic modified and normal poly(ethylene terephthalate) yarns were heat set at temperatures from 100 to 220°C and times from 3.75 to 45 seconds. Tensile properties, critical dissolution times, and dye sorption of these yarns were examined as a function of time and temperature of heat stabilization. Melting behavior (DSC thermograms), thermal stress, and critical dissolution times vary as a function of time and temperature of heat setting in the same way for both cationic dyeable and normal PET yams.

Evaluation of adhesion characteristics of nylon‐6 tire cord to natural rubber

AbstractThe adhesion characteristics of Nylon‐6 cords to rubber matrix, using Resorcinol Formaldehyde Latex (RFL) solution, were evaluated at various conditions. The heat‐setting studies of RFL dipped cords in the temperature range of 180–210°C showed a loss in tensile properties. However, a minimum in the loss was observed when a pretension load was given to the cords. Percent shrinkage of RFL‐dipped cords increased with the increase in temperature of heat setting. Adhesion behavior of Nylon‐6 cords to rubber matrix showed some improvement under relaxed conditions in the entire temperature range studied. With the application of suitable tension to cord, adhesion behavior can be made constant. This has been attributed to the higher extent of shrinkage of cords under relaxed conditions providing greater cord surface area. This in turn, leads to increased cord to rubber matrix.

Effect of Internal Stress on Lattice Strain in Relaxed Heat Set PET Filaments

Using the method of resolving overlapping peaks, wide angle x-ray scattering data for relaxed heat set poly(ethylene terephthalate) (PET) filaments were analyzed and the characteristic parameters of some main crystal peaks were obtained precisely. The relative lattice strains of the filaments treated at different heat setting temperatures were thus determined. With the help of a thermomechanical analyzer, the thermal shrinkage stresses were also measured. Analysis of these experimental results indicated that the crystal structure of polymer fibers differs from that of low molecular weight substances, in that the unit cell parameters of the former are much more influenced by the internal stresses left in the fiber during the heat setting of the drawn polymer fibers. The series model is suitable for explaining these phenomena.

Effects of Heat Treatment and Mechanical Stresses on the Dielectric Strength of Uniaxially Drawn Pet Film

The dc dielectric strength of uniaxially drawn polyethylene terephthalate (PET) film has been investigated under compressive stresses. The drawn samples are heat-set in a silicone oil bath over a temperature range from 100 to 220°C for durations of 1 and 60 min in order to control the degree of crystallinity of the samples. The dc dielectric strength under no mechanical stress is found to increase with heat-setting temperature regardless of the heat-setting time. The compressive stress value showing maximum dielectric strength under compression has decreased significantly with increase in the heat-setting time and heatsetting temperature. The results obtained are discussed in terms of the morphological and mechanical properties of the samples.

The effect of heat setting on the structure and mechanical properties of poly(ethylene terephthalate) fiber. I. Structural changes

AbstractWe report structural changes in commercial multifilament poly(ethylene terephthalate) (PET) yarn when it is heat set in silicone oil over a range of temperatures between 100 and 220°C for times ranging from 1 min to 1 hr, while the yarn was (1) free to relax, and (2) held taut at constant length. In one case, viz., a sample heat treated for 1 hr, the cooling time was also varied to study the effect of rate of cooling. The free‐annealed and taut‐annealed samples showed considerable differences. The predominant role of the temperature of heat setting on structure is discussed in detail. There are considerable changes in the amount and orientation of the amorphous phase, and these will be shown to have important influence on mechanical properties in subsequent reports.

The Noncrystalline State Within PET Fibers—Meaning and Characterization by Mechanical-Relaxation Measurements

The performance of synthetic fibers cannot be completely understood without any knowledge of the structure in the noncrystalline regions. X-ray diffraction measurements led to the conclusion that the noncrystalline regions in PET fibers can be divided into isotropic noncrystalline (amorphous) and oriented noncrystalline fractions, the amount of which is dependent on the thermal and mechanical history. But x-ray diffraction data, thermal analysis, and dyeing experiments left many effects unexplained: the dependence of glass-transition and dye uptake on thermal history, the real order-disorder situation within the noncrystalline regions, certain mechanical properties, and their time-dependence such as relaxation. The glass-transition temperature Tg of PET fibers, as determined by viscoelastic measurements, runs through a maximum depending on the heat-setting conditions. This can be explained by the assumption that the average size of crystallites reaches a minimum, and therefore the number of crystallites per unit volume shows maximum values at a heat-setting temperature of about 190°C. By raising the heat-setting temperature above 190°C, the crystal lites become larger. Segregation of the crystallites in the noncrystalline matrix occurs. If the network formed by the crystallites has its highest density, Tg shows maximum, and dye uptake, minimum values due to low molecular mobility. For the same reason the storage modulus in the rubber state has maximum values after heat-setting at temperatures around 190°C.

Studies on heating and cooling of synthetic fibers, yarns, and fabrics. I. Properties of nylon and polyester filament yarns on heat setting in silicone oil

AbstractNylon 6, nylon 66, and polyester [poly(ethylene terephthalate)] filament yarns were heat set at different temperatures in oil under a variety of experimental conditions. The effect of time of heat setting, tension on the yarn during heat setting, as well as the effect of the initial tenacity and extension on subsequent changes in the mechanical properties of the heat‐set yarns have been studied. The breaking strength, elongation at break, and work of rupture have been found to be different for samples heat set while slack and at constant length. The breaking strength remains more or less constant over a wide range of heat setting temperatures up to 240°C in the case of nylon 66 and polyester, and up to 200°C in the case of nylon 6, contrary to the observations of Dumbleton et al. When treated in the slack condition, the breaking extension increases by about 1–2.5 times the control value, while heat setting at constant length produces a decrease in the case of nylon 66 and a marginal increase in the case of nylon 6 and polyester. The initial modulus decreases irrespective of the conditions under which the filaments are heat set. From measurements of the shrinkage and the residual shrinkage in boiling water it appears that dimensional stability can be achieved by heat setting even at constant length. Heat setting produces significant improvement in the crease recovery and resiliency of the fibers. Heat setting has also been found to significantly increase the overall crystallinity of the fibers as determined by critical dissolution time and parallel and perpendicular refractive indices. The overall orientation of the polymer chains, as determined from sonic velocity measurements, decreases on heat setting in the slack condition. Heat setting at constant length produces a marginal improvement in the overall orientation only in the case of nylon 66 yarns. Shrinkage occurs instantaneously. Crystallinity, on the other hand, improves with increasing time of heat setting.

The Influence of Glass-Transition Temperatures of Poly (Ethylene Terephthalate) Films on the Fading Behavior of Fluorescent Brightening Agents

Studies have been made of the dependence of the fading behavior of dispersed-type fluorescent brightening agents in poly (ethylene tetrephthalate) (PET) films on the temperature at which the films have been heat-set and dyed. A measure of the variation in the fading behavior can be given by parameter A, defined as k2 (1st-order)ɛ/ k2' (2nd-order), as in Hida's equation. This constant decreases with increase in the temperatures of heat-setting and dyeing of PET films. And the rate of fading increases with increase in these temperatures. It is found that the physical state of adsorbed dye on PET films varies with these temperatures. The glass-transition temperatures Tg of heat-set PET films were measured. Tg decreases with increase in the heat-setting temperature. The values of parameter A are related to the difference between the dyeing temperature and Tg ( T — Tg), and so the physical state of adsorbed dye on PET films is considered to be governed by the segmental mobility of polymer chains during dyeing. The variation of the rate of fading and parameter A with the dyeing and heat-setting temperatures of PET films might be explained in terms of the additional free volume.

Effect of Drying and Heat-Setting Temperatures on the Removal Characteristics of Polyvinyl Alcohol Size

Polyvinyl alcohol applied to cotton/polyester fabrics was dried, then heat-set using temperatures ranging from 95 to 165°C. The samples were washed in water baths ranging in temperature from 45 to 85°C. Measurements of the amount of size removed during washing showed that the heat-setting temperature altered the ease of removal. Insight into the film structure of PVA which has been heat-set was gained using differential thermal analysis.

The effect of structural changes on dye diffusion in poly(ethylene terephthalate)

AbstractThe diffusion of a disperse dye, 1‐amino‐4‐hydroxyanthraquinone (C.I. Disperse Red 15) into poly(ethylene terephthalate) fibers has been studied as a function of heatsetting temperature and draw ratio. It was found that the dynamic loss modulus E″, measured under the dyeing conditions, was related to the dye diffusivity D. This indicates that the diffusion is controlled by the mobility of the polymer chain segments. Both the diffusivity and dye saturation values do not vary monotonically with heatsetting temperature but exhibit a minimum at a heat‐setting temperature near 175°C. X‐ray diffraction measurements were used to show that this behavior is attributable to crystallinity and crystal size changes resulting from heat‐setting.