Polymer Physics for Polymers - Assignment Example

1. (6 points) The glass transition temperature of Nylon-6,6 varies with its water content expressed in the terms of number of moles per mole of constitutional repeating unit (Xwater) according to the linear equation: Tg(K)= 354-170Xwater Nylon-6,6 can absorb up to 7% w/w of water. Why is this good news for your laundry and ironing? Glass transition temperature of nylon -6.6 varies with water content but in normal circumstances it is known to range between 33-530C. However in this case the glass transition temperature is calculated as follows Tg(K)= 354-170(7%) = 342.1Kor 69.10C This is an improvement and it is good for laundry and ironing since wrinkling of cloths depends on glass transition temperature. It means glass transition temperature increased above the polymer molecules thus its crystallisation structure improved reducing the glassy nature of nylon. In normal circumstances nylon is wrinkled by heat and water because of low glass transition temperature. the chemicals used to make nylon have reactive groups at both ends of their molecules. The reactive groups join by splitting off a small molecule of water or hydrogen chloride. In this way a long-chain polymer molecule is formed. The process is called condensation polymerization. 2. (14 points) Try to sort the following polymers according to their glass transition temperature. Give reasons why you decided this way! In some cases it is not possible to decide between 2 polymers with the information given. In such a case put the two polymers in one group and explain why you think they should have similar Tg’s! Polystyrene star polymer The Polystyrene have low Tg’s because of structure nature Polystyrene prepared with Ziegler-Natta catalyst Ziegler-Natta catalyst reduces the glass transition temperature as compared with that of butanthiol and divinylbenzen Polystyrene prepared in the presence of a chain transfer agent such as butanthiol It has higher glass transition temperature as compared to Ziegler-Natta catalyst Polymer prepared via radical polymerisation of styrene and divinylbenzene It has higher glass transition temperature as compared to Ziegler-Natta catalyst Block copolymer of styrene and acrylic acid acrylic acid increases glass transition temperature but is lower than butyl acrylate Random copolymer of polystyrene and butyl acrylate (50/50 mol-%) It has a higher among the given polymers The Polystyrene prepared in the presence of a chain transfer agent such as butanthiol and Polymer prepared via radical polymerisation of styrene and divinylbenzene have the similar Tg’s because the structure formed during polymerization is similar polymer 3. (20 points) The Rayleigh ratio for a series of dilute solutions of PMMA in ethylene dichloride at 25 °C, was determined in a light scattering photometer at various angles θ. The following table shows values of c/R(θ), for the various concentrations and scattering angles c θ 0.0096 0.0048 0.0024 0.0012 30 56.3 35.9 26.4 21.4 45 57.1 36.4 26.7 21.5 60 57.5 36.8 26.8 21.8 75 58.3 37.5 27.6 22.6 90 59.1 38.4 28.3 23.6 Given n0 = 1.5, dn/dc = 0.11 cm3/g, λ = 436 nm and Avogadro’s Number = 6.03 × 1023, calculate Mw for the PMMA sample. Also, determine the radius of gyration of the polymer in the solvent, and the second virial coefficient. K=()2 K=(0.11)2 = 24.66cm2/g 56.3 = 24.66cm2/g X Mw x 0.0096 Mw = 237.812 Rg = x x 0.0096 Rg = 304,336,655.7 = 1+ (304 x106)2 sin2 ( = 1.01 P() = 0.989 = ( +2AC)() = ( +2A x 0.0096)(1.01) A= 0.00637 4. (10 points) You are dissolving isotactic PMMA (Mn = 100,000 g/mol) in THF, a good solvent for this polymer (α = 5), and you know that PMMA (δ = 18.4 (J/cm3)1/2) has a χ1 value of 0.477 in THF (δ = 20 (J/cm3)1/2) and a cr value of 9.3. Calculate: a. The solvent molar volume (Vs), in L/mol, when the solution temperature is held at 50 °C χ=()2 0.477=()2 0.477=()2 V=301 b. The radius of gyration () for PMMA in THF 5. (15 points) Below is the schematic diagram of a single extruder which you are using to process HDPE into plastic bottles on a production line. Describe the different parts of the extruder set up shown below and the operating temperature of the extruder. What steps would you take to ensure that the bottles have a sufficiently high percent crystallinity so as to prevent leakage of the liquid contents? A- hopper supplies and holds the plastics which are to be processed. It can also be used to supply any other materials which will be conveyed through the system. The plastic pellets to be conveyed into the crushing and melting within the extruder are fed in this zone. It controls the flow of materials into the heating section before shutting. B-compression zone- is where the material is put into pressure for purposes of compression. That is it must be melted before compressing. During the compression heating and friction is increased to melt the materials. Before these materials are sent to metering zone which is C. C- Metering zone is involved in measuring the output which has been put in a uniform room temperature. This zone has thick-walled steel chamber so as to be able to withstand high temperatures and pressures as well as friction D- This cooling zone which has resulting with a dropped pressure and temperature . E – Downstream Equipment which allows the completed plastic is out of the extruder. To have had a sufficiently high percent crystallinity so as to prevent leakage of the liquid contents; the plastics are cleaned and separated to different colors. They are melted after they have been separated and cooled to avoid. During melting, the liquidity is mixed with stabilizers to assist in block formation. The walls are lubricated to make them pliable and reduce adherence to the extruder walls. Plasticisers reduce brittle behaviour, making processing easier and less costly. Read More