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Polyester Fiber:
Polyester fiber is a “manufactured fiber in which the fiber forming substance is any long chain synthetic polymer composed at least 85% by weight of an ester of a dihydric alcohol (HOROH) and terephthalic acid (p-HOOC-C6H4COOH)”. The most widely used polyester fiber is made from the linear polymer poly (ethylene terephtalate), and this polyester class is generally referred to simply as PET. High strength, high modulus, low shrinkage, heat set stability, light fastness and chemical resistance account for the great versatility of PET.

Process Flow Chart of Synthetic Fiber Production:
The process flow chart of various synthetic fibers is differing from one to another but basic process is same. Here, I have given a flow chart of synthetic fiber production which is same for all. It is the basic sequence of man made fiber production.

Raw Materials / monomers

↓

Polymerization

↓

Drawing and Stretching

↓

Texturing

↓

Intermingling

↓

Heat Setting

↓

Finished Filaments

Raw Materials:
Polyester is a chemical term which can be broken into poly, meaning many, and ester, a basic organic chemical compound. The principle ingredient used in the manufacture of polyester is ethylene, which is derived from petroleum. In this process, ethylene is the polymer, the chemical building block of polyester, and the chemical process that produces the finished polyester is called polymerization.

Polymer Formation:
Polyethylene Teraphthalate (PET) is a condensation polymer and is industrially produced by either terephthalic acid or dimethyl terephthalate with ethylene glycol. Other polyester fibers of interest to the nonwovens field include:

1. Terephthalic Acid (PTA), produced directly from p-xylene with bromide-controlled oxidation.
2. Dimethyl Terephthalate (DMT), made in the early stages by esterification of terephthalic acid. However, a different process involving two oxidation and esterification stages now accounts for most DMT.
3. Ethylene Glycol (EG) initially generated as an intermediate product by oxidation of ethylene. Further ethylene glycol is obtained by reaction of ethylene oxide with water.

Synthesis of Polymer:

Synthesis of Polymer:s: A representative polyester, PET is polymerized by one of the following two ways: Ester Interchange: Monomers are diethyl terephtalate and ethylene glycol.

Direct Etherification: Monomers are terephthalic acid and ethylene glycol. Both ester interchange and direct esterification processes are combined with polycondensation steps either batch-wise or continuously. Batch-wise systems need two-reaction vessels- one for esterification or ester interchange, the other for polymerization. Continuous systems need at least three vessels – one for esterification or shear interchange, another for reducing excess glycols, the other for polymerization.

Another way to produce PET is solid-phase polycondensation. In the process, a melt polycondensation is continued until the pre-polymer has an Intrinsic Viscosity of 1.0-1.4, at which point the polymer is cast into a solid firm. The pre-crystallization is carried out by heating (above 200oC) until the desirable molecular weight is obtained. Later the particulate polymer is melted for spinning. This process is not popular for textile PET fibers but is used for some industrial fibers.

Branched and Crosslinked Polyesters: If glycerol is allowed to react with a diacid or its anhydride each glycerol will generate one branch point. Such molecules can grow to very high molecular weight. If internal coupling occurs (reaction of a hydroxyl group and an acid function from branches of the same or different molecule), the polymer will become crosslinked. Rigidly crosslinked polymers are totally unaffected by solvents.

Fiber Formation:
The sequences for production of PET fibers and yarns depend on the different ways of polymerization (continuous, batch-wise, and solid-phase) and spinning (low or high windup speed) processes.

The Manufacturing Process:
Polyester is manufactured by one of several methods. The one used depends on the form the finished polyester will take. The four basic forms are filament, staple, tow, and fiberfill. In the filament form, each individual strand of polyester fiber is continuous in length, producing smooth-surfaced fabrics. In staple form, filaments are cut to short, predetermined lengths. In this form polyester is easier to blend with other fibers. Tow is a form in which continuous filaments are drawn loosely together. Fiberfill is the voluminous form used in the manufacture of quilts, pillows, and outerwear. The two forms used most frequently are filament and staple.

Manufacturing Filament Yarn:

Polymerization

1. To form polyester, dimethyl terephthalate is first reacted with ethylene glycol in the presence of a catalyst at a temperature of 302-410°F (150-210°C).

2. The resulting chemical, a monomer (single, non-repeating molecule) alcohol, is combined with terephthalic acid and raised to a temperature of 472°F (280°C). Newly-formed polyester, which is clear and molten, is extruded through a slot to form long ribbons.

Drying

3. After the polyester emerges from polymerization, the long molten ribbons are allowed to cool until they become brittle. The material is cut into tiny chips and completely dried to prevent irregularities in consistency.

Melt spinning

4. Polymer chips are melted at 500-518°F (260-270°C) to form a syrup-like solution. The solution is put in a metal container called a spinneret and forced through its tiny holes, which are usually round, but may be pentagonal or any other shape to produce special fibers. The number of holes in the spinneret determines the size of the yarn, as the emerging fibers are brought together to form a single strand.

5. At the spinning stage, other chemicals may be added to the solution to make the resulting material flame retardant, antistatic, or easier to dye.

Drawing the fiber

6. When polyester emerges from the spinneret, it is soft and easily elongated up to five times its original length. The stretching forces the random polyester molecules to align in a parallel formation. This increases the strength, tenacity, and resilience of the fiber. This time, when the filaments dry, the fibers become solid and strong instead of brittle.

7. Drawn fibers may vary greatly in diameter and length, depending on the characteristics desired of the finished material. Also, as the fibers are drawn, they may be textured or twisted to create softer or duller fabrics.

Winding

8. After the polyester yarn is drawn, it is wound on large bobbins or flat-wound packages, ready to be woven into material.

Manufacturing Staple Fiber:
In making polyester staple fiber, polymerization, drying, and melt spinning (steps 1-4 above) are much the same as in the manufacture of filament yarn. However, in the melt spinning process, the spinneret has many more holes when the product is staple fiber. The rope-like bundles of polyester that emerge are called tow.

Drawing tow

1. Newly-formed tow is quickly cooled in cans that gather the thick fibers. Several lengths of tow are gathered and then drawn on heated rollers to three or four times their original length.

Crimping

2. Drawn tow is then fed into compression boxes, which force the fibers to fold like an accordion, at a rate of 9-15 crimps per inch (3-6 per cm). This process helps the fiber hold together during the later manufacturing stages.

Setting

3. After the tow is crimped, it is heated at 212-302°F (100-150°C) to completely dry the fibers and set the crimp. Some of the crimp will unavoidably be pulled out of the fibers during the following processes.

Cutting

4. Following heat setting, tow is cut into shorter lengths. Polyester that will be blended with cotton is cut in 1.25-1.50 inch (3.2-3.8 cm) pieces; for rayon blends, 2 inch (5 cm) lengths are cut. For heavier fabrics, such as carpet, polyester filaments are cut into 6 inch (15 cm) lengths.

Spinning Process:
The degree of polymerization of PET is controlled, depending on its end-uses. PET for industrial fibers has a higher degree of polymerization, higher molecular weight and higher viscosity. The normal molecular weight range lies between 15,000 and 20,000. With the normal extrusion temperature (280-290oC), it has a low shear viscosity is 1000-3000 poise. Low molecular weight PET is spun at 265oC, whereas ultrahigh molecular weigh PET is spun at 300oC or above. The degree of orientation is generally proportional to the wind-up speeds in the spinning process. Theoretically, the maximum orientation along with increase in productivity is obtained at a wind-up speed of 10,000m/min. Although due to a voided skin, adverse effects may appear at wind-up speeds above 7000m/min.

Drawing Process:
To produce uniform PET, the drawing process is carried out at temperature above the glass transition temperature (80-90oC). Since the drawing process gives additional orientation to products, the draw ratios (3:1-6:1) vary according to the final end-uses. For higher tenacities, the higher draw ratios are required. In addition to orientation, crystallinity may be developed during the drawing at the temperature range of 140-220oC.

Polyester Fiber Production Flow Chart:

The latest Polyester production (Research Method):
Dr Boncella and Dr Wagner at The University of Florida are two scientists involved with the study to reveal a method for manufacturing polyester from two inexpensive gases: carbon monoxide and ethylene oxide. The polyester most commonly used today is referred to as PET or polyethylene terephtalate. Scientists have been successful in producing low molecular weight polyester using carbon monoxide and ethylene oxide, but researchers still lack the catalyst – a substance that speeds up chemical reactions – needed to make the reaction work more efficiently. They are looking for the chemical compound that will take molecules of low DP and create 1arger ones. Although they have had success in the research so far, they have yet to produce commercially useable polyester from the inexpensive gases. If this is successful, then these research findings can be used to replace the current polyester product, getting the same performance for a lower price. Finally, we all know that research requires patience and a long-term effort.

Structural Composition of PET:
The one of the distinguishing characteristics of PET is attributed to the benzene rings in the polymer chain. The aromatic character leads to chain stiffness, preventing the deformation of disordered regions, which results in weak van der Waals interaction forces between chains. Due to this, PET is difficult to be crystallized. Polyester fiber may be considered to be composed of crystalline, oriented semi crystalline and noncrystalline (amorphous) regions. The aromatic, carboxyl and aliphatic molecular groups are nearly planar in configuration and exist in a side-by-side arrangement. Stabilization distances between atoms in neighboring molecules are usually van der Waals contact distances, and there is no structural evidence of any abnormally strong forces among the molecules. The unusually high melting point of PET (compared to aliphatic polyesters) is not the result of any unusual intermolecular forces, but is attributed to ester linkages. The cohesion of PET chains is a result of hydrogen bonds and van der Waals interactions, caused by dipole interaction, induction and dispersion forces among the chains. The capacity to form useful fibers and the tendency to crystallize depend on these forces of attraction.

The interactive forces create inflexible tight packing among macromolecules, showing high modulus, strength, and resistance to moisture, dyestuffs and solvents. The limited flexibility in the macromolecule is mainly due to the ethylene group. The extended quenched fiber does not show any early development of crystallinity; the growth of crystals starts to occur upon drawing. A number of basic structural models are required to represent the different states of the fiber: amorphous (no orientation) after extrusion, amorphous (no orientation) after cold drawing, crystalline orientation after thermal treatment and after hot drawing, stretching and annealing. The crystalline oriented form can also be obtained by high stress (high-speed) spinning.

Differential Scanning Calorimerty (DSC) can measure crystallinity and molecular orientation within the fibers. This type of analysis is based on distinctly different values of the heats of fusion for crystalline and noncrystalline forms of the polymer. The heat of fusion of the sample is compared with a calibration standard. The crystallinity is determined by the following relationship.

% Crystallinity = ΔHf/ΔH*f

Where, H*f is the heat of fusion of a 100% crystalline polymer, reported in the literature to be about 33.45 cal/g (equal to 140 J/g). The Tg (glass transition temperature) and Tm (melting point) of the fibers can also be determined by DSC analysis. The results of the density and DSC measurements are shown in Table 1.

Table 1: Crystallinity of Polyester Fiber

Tg – Glass transition temperature.
Tm – Melting temperature.
∆H – heat of fusion.

The rapid quenched PET without drawing is amorphous. The temperature range of crystallization for PET is From 10oC below the melting point to the temperature a little higher than the glass transition temperature, 250-100oC. Typical PET has 50% crystallinity. The repeat unit of PET is 1.075 nm and is slightly shorter than the length of a fully extended chain (1.09 nm). Therefore, the chains are nearly planar. The crystal unit cell is triclinic with dimensions a = 0.456nm, b = 0.594nm, c = 1.075nm. PET crystal structure is illustrated in below Fig 4. Another factor for crystallization is the position of the benzene rings. If benzene rings are placed on the chain axis (c), then close packing of the molecular chains eases polymer crystallization.

General Polyester Fiber Characteristics:

1. Strong
2. Resistant to stretching and shrinking
3. Resistant to most chemicals
4. Quick drying
5. Crisp and resilient
6. Wrinkle resistant
7. Mildew resistant
8. Abrasion resistant
9. Retains heat-set pleats and crease
10. Easily washed

Physical Properties of Polyester Fiber:

1. Thickness : 1.2D, 1.5D , 2.0D
2. Color : white
3. Length : Variable cut lengths
4. Density : 1.39 g/cc
5. Tenacity : high, 40 to 80 cN/tex
6. Moisture regain : 0.4 % (at 65% R.H and 20°C)
7. Elongation : high, 15 to 45%
8. Flame reaction : melts, shrinks, black fumes
9. Melting point : 260°C

Melt-Blown Process of Polyester:
The IV (intrinsic viscosity) and crystallinity levels of a melt-blown polyester determine the performance of the finished product. A higher IV leads to an increased level of crystallinity, which improves the barrier properties of the polyester melt-blown structure. However, it significantly reduces modulus, toughness and elongation. The advantage of using polyester over such polymers as polyolefins is its heat resistance and greater chemical resistance. Polyesters also offer a moderate oxygen barrier.

Relationship between Structure, Properties and Processing Parameters of PET Fibers:
Properties of polyester fibers are strongly affected by fiber structure. The fiber structure, which has a strong influence on the applicability of the fiber, depends heavily on the process parameters of fiber formation such as spinning speed (threadlike stress), hot drawing (stretching), stress relaxation and heat setting (stabilization) speed.

As the stress in the spinning threadlike is increased by higher wind-up speed, the PET molecules are extended, resulting in better as-spun uniformity, lower elongation and higher strength, greater orientation and high crystallinity. Hot drawing accomplishes the same effect and allows even higher degrees of orientation and crystallinity. Relaxation is the releasing of strains and stresses of the extended molecules, which results in reduced shrinkage in drawn fibers. Heat stabilization is the treatment to “set” the molecular structure, enabling the fibers to resist further dimensional changes. Final fiber structure depends considerably on the temperature, rate of stretching; draw ratio (degree of stretch), relaxation ratio and heat setting condition. The crystalline and noncrystalline orientation and the percentage of crystallinity can be adjusted significantly in response to these process parameters.

Mechanical Properties: As the degree of fiber stretch is increased (yielding higher crystallinity and molecular orientation), so are properties such as tensile strength and initial Young’s modulus. At the same time, ultimate extensibility, i.e., elongation is usually reduced. An increase of molecular weight further increases the tensile properties, modulus, and elongation. Typical physical and mechanical properties of PET fibers are given in Table 2. And stress-strain curves in Fig. 5. It can be seen that the filament represented by curve C has a much higher initial modulus than the regular tenacity staple shown in curve D. On the other hand, the latter exhibits a greater tenacity and elongation. High tenacity filament and staple (curve A and B) have very high breaking strengths and moduli, but relatively low elongations. Partially oriented yarn (POY) and spun filament yarns, exhibit low strength but very high elongation (curve E). When exposing PET fiber to repeated compression (for example, repeated bending), so-called kink bands start to form, finally resulting in breakage of the kink band into a crack. It has been shown in that the compressibility stability of PET is superior to that of nylons.

Table 2: Physical Properties of Polyester Fiber

Hangzhou Yaoyang Technology Co.,Ltd Our Factory is Located in Lushan Industry, Lushan District, Fuyang City ,Zhejiang Province,China
Since 1995,We specialize in textiles business ; And Yaoyang is mainly in producing Regenerated and Virgin fiber ; Goods series : Hollow Polyester Stable Fiber , Hollow Conjugated silicon and nonsilicon ; micro fiber ; feather fiber ; low melt fiber both white and black ; polyester tops etc ,both colored and white ; including Bedding Fiber over 10 years,Mainly for stuffing Soft Toys,pillow ,quilts and sofa mattress ; spinning ; nonwoven ,bedding sheet and so on.

linda@yaoyangtechnology.com

whatsapp 008613396518161 

Yaoyang History:

Factory Since 1990,Company Since 2018, Hangzhou Yaoyang Technology Co.,Ltd,Our Factory is Located in Lushan Industry, Lushan District, Fuyang , Hangzhou City,Zhejiang Province,China
Our factory is mainly in producing Regenerated and Virgin Polyester Staple fiber ; Goods series : Hollow Polyester Stable Fiber , Hollow Conjugated silicon and nonsilicon ; Micro feather fiber ; Feather fiber ; Solid silion or non silicon Fiber ; Low melt fiber both white and black 2D-4D -6D ; polyester tops etc ,both colored and white and FR fiber ,Anti Bacteria Fiber etc Functioned ;
We have four advanced domestic production lines and we can produced 50000Tons fiber per year,and having built the long-term buisiness with domestic and foreign company.We Promise that our products are in excellent quality and competitive price.

Goods are widly used in for stuffing Soft Toys,pillow ,quilts and sofa mattress ; spinning ; nonwoven ,bedding sheet and so on.

Yaoyang Group Branch business : Viscose Fiber / Acrylic Fiber /Nylon Fiber /Bamboo fiber;

Yaoyang Technology Sourcing Department : We also have trading department in Chemicals : like Poliol / polimerico and Tdi ,and other special items over 10 years

Linda (Marketing Manager )
Hangzhou Yaoyang Technology Co.,Ltd
Lushan morden times,Lushan district ,Fuyang City ,Zhejiang Province ,China
Post Code: 311400
Celphone : 008613396518161
On line services :
WhatSapp : 008613396518161 & 008615336525326
Wechat Id : c13396518161
Tel:86-571-63358973
E-mail: linda@yaoyangtechnology.com or admin@yaoyangtechnology.com
www.fiber-polyester.com