Environmental effects on polymeric fibers

4 Some important low modulus synthetic polymeric fibers 

In this section we describe the processing, structure, and properties of some important low modulus synthetic polymeric fibers. 

Polyester fibers, similar to polyamide fibers, represent another important family of fiber. Polyester fiber was discovered in England in 1941 and commercialized in 1950. Two common trade names of polyester are Dacron in the US and Terylene in the UK. The term polyester fiber represents a family of fibers made of polyethylene terephthalate. Dimethyl terephthalate is reacted with ethylene glycol in the presence of a catalyst, antimony oxide, to produce polyethylene terephthalate or polyester. The chain repeat structure of PET is given in Fig. 4.6. Although polyesters can be both thermosetting and thermoplastic, the term polyester has become synonymous with PET. Note that the PET chain structure is different from the simpler structure of nylon or polyethylene. In PET, the aromatic ring and its associated C-C bonds provide a rigidity to the structure. The polyester structure is also bulkier than that of nylon or polyethylene. These factors make polyester less flexible than nylon and polyethylene, and the crystallization rate of PET slower than that of nylon or polyethylene. Thus, when polyester is cooled from the melt, an appreciable amount of crystallization does not result. 

Like nylon, polyester fibers are made from linear-condensation polymers by melt spinning, followed by drawing. Similar to nylon, the drawing treatment involves a stretch ratio of 5. The drawing of polyester fiber is done above its glass transition temperature of 80°C. 

Polypropylene and polyethylene are perhaps the two most important polyolefin fibers. Polyethylene has a simple, linear chain structure consisting of a carbon backbone and small hydrogen side groups. Such a structure makes it easy to crystallize. There are three common grades of polyethylene low density polyethylene (LDPE), high density polyethylene (HDPE), and ultra-high molecular 

---

The usage of this fiber can be found in construction and automobile industries. For instance, rubbers are rarely used in their unmodified form with respect to their applications. They are often mixed with fillers to improve their process ability, mechanical strength, and to reduce cost. Carbon black and silica are well-known filler that highly is commercialized. Rice husk ash in rubber compounding has drags intense interest because of its low cost, environmental preservation benefit, and an increased emphasis on the use of renewable resources (Arayapranee et al. 2005). Numerous trials have been done by the researchers which use Rice Husk as a filler for polymeric materials. Sae-oui et al. (2002) investigated the effects of filler loading on the properties of RHA-filled natural rubber (NR) materials compared with those of commercial fillers. 

---