Poly crystal modulus

Here m is the mode order (m — 1,3,5. .., usually 1 for polyethylenes), c the velocity of light, p the density of the vibrating sequence (density of pure crystal) and E the Young s modulus in the chain direction. The LAM band has been observed in many polymers and has been widely used in structural studies of polyethylenes [94—99,266], as well as other semi-crystalline polymers, such as poly (ethylene oxide) [267], poly(methylene oxide) [268,269] and isotactic poly(propylene) [270,271], The distribution of crystalline thickness can be obtained from the width of the LAM mode, corrected by temperature and frequency factors [272,273] as ... 

Poly(HAMCL), unlike PHB or its copolymers, behave as elastomers with crystals acting as physical crosslinks and therefore can be regarded as a class of its own with respect to mechanical properties [53,61,91]. Elongation to break of 250-350% has been reported, and a Young s modulus up to 17 MPa [53,91]. 

Andrews76 gave results of the work of Reed and Martin on cis-polyisoprene specimens crystallized from a strained cross linked melt and on solid state polymerized poly-oxymethylene respectively, explaining the results by simple two phase models. He also summarized the studies of Patel and Philips775 on spherulitic polyethylene which showed that the Young s modulus increased as a function of crystallite radius by a factor of 3 up to a radius of about 13 n and then decreased on further increasing spherulite size. 

Figure 12,27 Variation of the complex relaxation modulus of poly(ethylene ter-ephthalate) with temperature, in the vicinity of the glass-rubber relaxation, for samples of various crystallinities obtained in isothermal crystallizations ( ) 46%, (<>) 40%, ( ), (V) 26%, ( ) 2-3%, and (O) 0%. (From Ref. 33.)...

Ultrasonic interferometry, in which the travel time of high-frequency elastic waves through a sample is measured, also yields elastic moduli. Because it is a physical property measurement, rather than an optical spectroscopy, it can be used equally well on poly-crystalline samples as single-crystals, although polycrystalline measurements only yield the bulk elastic properties, bulk modulus and shear modulus, G. High-pressure ultrasonic interferometry techniques were initially developed in the piston cylinder... 

S. L. Kwolek, a woman scientist of DuPont, invented the liquid crystal aromatic polyamides which eventually paved the way to the first commercial liquid crystalline polymer product—poly-p-phenyleneterephthalamide under the trade name Kevlar. She recently recalled, When I dissolved the PBA (poly-p-aminobenzamide) polymer at 10% concentration in tetram-ethylurea with 6.5% LiCl, the solution was unusually fluid, turbid, stir-opalescent, and butter-milk-like in appearance. The fiber that was spun turned out to be extremely strong with a modulus of 430 gpd This discovery in 1964 remains a milestone of this field. In recognition of her contribution, the American Society of Chemistry Industry awarded Kwolek the 1997 Perkin Medal. 

The physical properties of polypropylene, poly(ethylene terephthalate), and polyimide are greatly influenced by orientation of the polymer. Polypropylene and poly(ethylene terephthalate) become highly crystallized upon stretching. Oriented, crystalline poly(ethylene terephthalate), for example, has significantly higher modulus, tensile strength, and continuous use temperature than its extruded, unoriented analog (see Table II). 

Figure 2. Mechanical loss tangent (tan 5) and elastic storage modulus at 102 c.p.s. and spin-lattice relaxation time (20) vs. temperature for poly (4-methyl-l-pentene) crystallized from dilute solution...

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