Kevlar Physical properties

Liquid-crystal (LC) polymers are the subject of worldwide research and development. (1-5). Commercial films and plastics such as Kevlar (du Pont), Xydar (Dartco) and Ekonol (Sumitomo) utilize the remarkable ability of LC behavior to enhance physical properties. 

A third basic type, T950, has been developed especially for the rubber industry and is intended as a bracing in radial tyres. Arenka 900 and Arenka 930 have physical properties similar to those of Kevlar 29 and 49 respectively. 

The thermosetting resins used as matrices in FRP composites have been discussed in Chapter 2. The other constituent (fibre) and the interface between the matrix and the fibre merit attention. A wide variety of fibres are available for use in composites. The physical properties of the available fibres are presented in Table 62.. The most commonly used fibres are glass, carbon and Kevlar fibres. Each... 

Based on extensive research into the relationships between molecular structure and bulk physical properties, scientists at DuPont reasoned that a polyamide containing aromatic rings would be stiffer and stronger than either nylon 66 or nylon 6. In early 1960, DuPont introduced Kevlar, a polyaromatic amide (aramid) fiber synthesized from tere-phthalic acid and p-phenylenediamine ... 

Interest, academic and Industrial, In Liquid Crystal Polymers (LCP s) was sparked by the commercialization of Kevlar aromatic polyamide fiber In the early 1970 s. [1,2] This fiber can be made almost as stiff and as strong as steel, at one fifth of the density of steel. In addition. It has good resistance to chemical attack and outstanding resistance to heat. From a scientific point of view, LCP s are Interesting because they. In addition to displaying a variety of phenomena and properties seen with conventional Isotropic polymers, also exhibit many of the complex physical properties of small molecule liquid crystals.[3]... 

The physical properties of fibers produced from precursor liquid crystalline solutions are generally superior to those obtained from the corresponding isotropic solutions. Probably the most well-known commercial fiber derived from a lyotropic system is Kevlar , produced by Du Pont. Cellulose fibers have not yet been produced commercially from mesophase solutions using the direct solvent route [15]. Tencel , the commercialized cellulose fibers by... 

Table 9.7 Physical properties of Kevlar 29 (reprinted from Ref. 127 with permission of Wiley Sons).

The properties of resins, which are the weakest components in every composite, will be considered first. For epoxy resin, the effect of crosslinking as a correlation of chemical structure with physical data was studied. Many properties can be understood by the molecular anisotropy of binding forces. Strong covalent and weak van der Waals forces act along and transverse to the polymer chains, respectively. This molecular anisotropy also exists in fiber materials, such as Kevlar, which consists of strong, highly stretched polymer chains, which are weakly bonded together. 

Composites are made up of individual materials these are referred to as constituent materials. The purpose of a composite is to create a material that combines its constituent parts in some beneficial way. The two main categories of constituent materials are the matrix and the reinforcement. The synthetic matrix materials are either thermoplastic or thermosetting resins. These polymers bind the reinforcement together and determine the physical in-service properties of the composite material. Polymers can also act as reinforcing material in composites Kevlar for instance, is a synthetic polymer fibre that is very strong and imparts toughness to a composite. 

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