Question

Name: Matric No: Question 1 (a) Flat-plate X-ray diffraction pattern of a polytetrafluoroethylene was obtained by using CuKu radiation (A 0.1542 nm). Calculate the theoretical density of a polytetrafluoroethylene crystal. Given that it is a triclinic crystal, with a-b-1.768 nm, and c-0.554 nm. A unit cell consists of 13 tetrafluoroethylene repeat units, the angles between planes are a B 90, and y 119.3, Use equation: Vabc (1-cos a - cos B-cos) +2 (cosa cosp cosy)t (b) In a polymer blend, the mass fraction of crystallized polymer A is found to be 0.21. What is the density of the polymer blend, assuming the density of amorphous polytetrafluoroethylene is 0.89 g/cm?

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Answer 1

(as Theoretical density of a polymer is given by 1 VNA them . V= volume of pilymer unit cell A = Mass of repeating unit NA - avogadoo. No - 6. 023x 1023 n a no of repeat units in polymer unit cell =13 For triclinic system : Va abeli-cos'a-usy --COSP8') + + 2 llosa cs p cost a, b, c are lattice parameters and a, b, 8 are angle betrees them a= b = 1.768 nm = 1.768 x 10 Fem em a lot C = 0.554 nm = 0.554x107 X = B = 90° ; 3=119.3°C V= (1-769x1768 x 0.554)x10-(1-65°90-kosroo- cos*119. 3) . + 2 / C8590crsqo cosia:3: [crsqo ol: = 1.732 x 0.761 = ls 317 *10-Yem Repeating unit of Polytetrafluoroethylene is tc-4.7 → Molecular mass = 12x2 + 4x18.99 ... = 24 x 75.66 = 99.96ol met Atomic mass of C=12 Atomic . ua f = 18.99 137 99.96 x 10-2 128 Pt 1317 x 1072\x61023x1983 h glee = (1 638 gieel L xi FO

In fraction of . a mass ä polymer. polymer blend - Crystalline palyner a 0.21 & Mass fraction of amorphous polynes of amorphous polymer = oras( 10.21) 30.79 Hono Density of crystalline polytetra fluoroethylene (PTFE) = !.638 gice : Dersity of amorphous PTFE' = 0.89 glee Density of blend = 0.79x0.8941638x0.21 = 1:047 glee