List of top Polymer Science and Engineering Questions

Binary polymer blends of polypropylene and polyamide 6 are immiscible. From a thermodynamic viewpoint this is due to \(\underline{\hspace{2cm}}\).

Equal and opposite forces of a constant magnitude \( F \) are applied at the two ends of a thin elastomeric rod, which is held at a temperature \( T_1 \) (where \( T_g < T_1 < T_m \), and \( T_g \) and \( T_m \) are the glass transition temperature and melting temperature respectively). If the temperature is increased to \( T_2 \) (where \( T_g < T_2 < T_m \) and \( T_2 > T_1 \)), the rod will \(\underline{\hspace{2cm}}\).

Match the Additive to its Function. 

Match the polymer processing operation with respect to its typical range of shear rate. 

Shear stress (\( \sigma \)) and shear viscosity (\( \eta \)) are plotted as functions of the shear rate (\( \dot{\gamma} \)) for idealized "solid-like with yielding (1)" and "liquid-like (2)" materials. 
 

Associate the shear stress and viscosity plots with the appropriate material responses.

The plateau modulus of polystyrene has a value of 0.2 × 10⁶ Pa at 150 °C. Given, the density of polystyrene is 1.05 g/cm³, the universal gas constant, \( R = 8.3 \, \text{J K}^{-1} \text{mol}^{-1} \), and the monomer molecular weight is 104 g/mol. The molecular weight between entanglements (rounded off to the nearest integer) of polystyrene chains is \(\underline{\hspace{2cm}}\) g/mol.

A single screw extruder is operating at a rotational speed of 2 revolutions per second for the extrusion of a Newtonian polymer under open-discharge conditions (in absence of a die, the pressure drop, \( \Delta p = 0 \)). The extruder has a screw diameter, \( D = 5 \, \text{cm} \), a channel depth, \( H = 0.4 \, \text{cm} \), distance between flights, \( W = 1 \, \text{cm} \), and a helix angle, \( \theta = 20^\circ \). Assume the value of \( \pi = 3.14 \). The volumetric flow rate (rounded off to 2 decimal places) is \(\underline{\hspace{2cm}}\) cm³/s.

At 215 °C, the viscosity of a polystyrene of molecular weight 250 × 10³ g/mol is 8.0 × 10³ Pa·s. The critical molecular weight of polystyrene, \( M_c = 35 \times 10^3 \) g/mol. For a similar polystyrene of molecular weight 500 × 10³ g/mol, the viscosity (rounded off to nearest integer) will be \(\underline{\hspace{2cm}}\) × 10³ Pa·s.

There are two different PTFE polymer specimens of the following density \( \rho \) and % crystallinity. For PTFE-specimen-1, \( \rho = 2.144 \, \text{g/cm}^3 \) and % crystallinity is 50. For PTFE- specimen-2, \( \rho = 2.215 \, \text{g/cm}^3 \) and % crystallinity is 75. Assuming the polymer is pure and defect free, the density (rounded off to 3 decimal places) of 100% amorphous PTFE specimen will be \(\underline{\hspace{2cm}}\) g/cm³.