Answer the questions

CHEE 4885 Winter 2024 Assignment 3 Due: Tuesday, February 6, 2024, at 11:59 PM Atlantic Question 1 [6 marks] Draw a stress-strain curve for a plastic sample that has undergone tensile testing. For the curve that you have drawn, choose three points along your curve; label them as A, B and C. i) ii) iii) Explain what happened during testing at each labelled point. Describe (or draw) how the sample looked at each labelled point. List what material property/properties could be measured at each labelled point. Question 2 [4 marks] A rubber has an elastic modulus of 1.25×107 dyn/cm2. A load of 7.5 kg is applied to a material sample which is 10 cm long, 0.5 cm wide, and 0.25 cm thick. What is the total length of the elongated material? Question 3 [5 marks] Calculate 𝑀𝑛 , 𝑀𝑤 , 𝐷𝑃𝑛 , 𝐷𝑃𝑤 , and polydispersity index for a sample of polystyrene with the following composition, where i represents the degree of polymerization and wt% represents the weight fraction of chains at each degree of polymerization. i wt% 50 0.03 100 0.07 150 0.13 200 0.18 250 0.22 300 0.16 350 0.11 400 0.06 450 0.04 Question 4 [5 marks] 150 g of polymer A, 300 g of polymer B, 425 g of polymer C, and 200 g of polymer D are mixed. Calculate the PDI of each ‘pure’ polymer, then calculate the 𝑀𝑛 , 𝑀𝑤 and PDI of the blend. Explain the change in PDI observed between the ‘pure’ polymers and the polymer blend. Data: Polymer A: 𝑀𝑛 = 45,000; 𝑀𝑤 = 70,000 Polymer B: 𝑀𝑛 = 150,000; 𝑀𝑤 = 200,000 Polymer C: 𝑀𝑛 = 80,000; 𝑀𝑤 = 120,000 Polymer D: 𝑀𝑛 = 350,000; 𝑀𝑤 = 800,000 Assignment 3 Page 1 of 2 CHEE 4885 Winter 2024 Question 5 [5 marks] The following are data from osmotic pressure measurements on a solution of polyester in chloroform at 20°C. The results are in terms of centimeters of solvent. The density of HCCl3 is 1.48 g/cm3. Find 𝑀𝑛 . Question 6 [5 marks] The relative flow times (t/t0) of a poly(methyl methacrylate) polymer in chloroform are given below. a) Determine [η] by plotting relevant data. 0.8 b) Find 𝑀𝑣 for this polymer, given [𝜂] = (3.4 × 10−5 )𝑀𝑣 Assignment 3 (dL/g). Page 2 of 2

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