Heat setting process

Fabrics composed of synthetic polymer fibers are frequendy subjected to heat-setting operations. Because of the thermoplastic nature of these fibers, eg, polyester, nylon, polyolefins, and triacetate, it is possible to set such fabrics iato desired configurations. These heat treatments iavolve recrystaUization mechanisms at the molecular level, and thus are permanent unless the fabrics are exposed to thermal conditions more severe than those used ia the heat-setting process. 

Microwave heating techniques have been widely used in textile chemistry. This paper presents a state-of-the-art review of microwave technologies and industrial applications. The characteristics of microwave interactions with textile materials are outlined together with microwave fundamentals in the heat-setting process. Further more, the limitations in current imderstanding are included as a guide for potential users and for future research and development activities. 

One current commercial flame retardant for polyester is a mixture of cyclic phosphate/phosphonates used in a pad-dry-heat set process (Fig. 8.18). ° Heat set conditions of 190-210 C for 0.5-2 min are adequate. This product when applied at 3 % add-on can provide durable flame retardancy to a wide variety of polyester textiles. 

In addition to stabilising the fabric, the heat setting process will also result in an increase in the density of the structure through increased fibre consolidation. This in turn will further assist in achieving a higher level of filtration efficiency. 

In recent years poly(ethylene terephthalate) (PET) microfibers (De Clerck et al., 2003) have attracted significant attention as a result of their superior drape, hand, improved water repellence, and breathability. Unfortunately, these advantages are also accompanied by difficulties in achieving a uniform color build-up in dyeing. Heat-set processes are applied to many fibers, yams, and fabrics to improve their dimensional stabihty and this involves exposure of the material to an annealing treatment. 

Higher levels of crystallinity are achieved if the molecule segments remain free to move, as is the case when the preform is heated to its highest possible temperature and the blow mold temperature is high. The amount and the rate of the increase in crystallinity depend on material IV, temperature, and time. The blowing process that intentionally drives the crystallinity up to create hot tillable, thermally stable bottles is called heat setting. In a typical heat setting process, the level of crystallinity reached is... 

Kerins GJ, et al. Method for producing a hot finable, collapse-resistant polyester container without the need to utilize heat set process techniques and/or non-conventional container geometries. US Patent 4,665,682 assigned to Continental PET Technologies issued May 19, 1987. 

The main aim of the heat setting process is to ensure that fabrics do not alter their dimensions during use. This is particularly important for uses such as timing and driving belts, where stretching of the belt could cause serious problems. It is important to examine the causes of this loss in stability so that a full understanding can be obtained of the effects that heat and mechanical forces have on the stability of fabrics. All fabrics have constraints place on them by their construction and method of manufacture, but it is the heat-setting mechanism that occurs within the fiber that will ultimately influence fabric dimensions. 

A mixture of superheated steam and air is necessary for the rapid heat setting process. In the steam/air mixture used as the setting mediiun, the total heat capacity is increased considerably and thus it is possible to apply... 

What are the possible effects of the heat setting process ... 

Figure 17.3. Schematic of drawing and heat setting processes of fibers.

Little is known concerning the mechanical, thermal and morphological properties with increased levels of RPET -PET blends for ISBM bottle applications. Variations in crystalline morphologies are dependant on processing methods and techniques thereof One such method for ensuring thermal stability and material integrity for PET containers is via the heat-setting process. 

The Design of Experiment (DoE) tool namely Echip version 7 was used for this work. Design variables were chosen that influenced the heat-set process and the hot- fill shrinkage (S2) of a PET beverage container Design variables included blow time, preform cooling time, mould temperature and material blend formulations. 

---