Compared to thermoplastics, thermosets are more rigid, brittle, capable of higher service temperatures, and cannot be remelted.   Question 25 options:   True   False

A metal term used to indicate that two or more layers of plastics (or metals) are pressed together under pressure is ______.

Thermoset polymers are generally characterized as ________ polymers     Cross-linked     Thermoplastic     Recyclable     Heavy     All these choices

13.3 Given the following information, and the Instron curve below for an axial stress experiment conducted on a sample of polyisoprene at room temperature (25 °C): Engineering Yield Stress = 48 MPa Elastic Modulus = 40 MPa Elongation at break (e) = 2.25 Ultimate Stress = 50 MPa (note 1 MPa = 1MN/m²; MN = megaNewton) = 106 N/m² Initial Sample Length = 1.5 cm (= 0.015 m) Initial Sample Cross-Sectional Area = 0.34 cm² (= 3.4 * 105 m²) Glass Transition Temperature = look up using the macrogalleria, level 2. A. What force is applied as the polymer reaches its yield stress (in N)? B. What is the length of the polymer just before it breaks (in cm)? C. Draw a plausible stress-strain graph (preferably using software like Excel) that incorporates all of the data given above for this experiment. D. Draw a second curve (qualitatively, by hand) on top of the graph in part (C) to indicate what the Stress-strain curve would look like if the sample were tested at -90 °C instead of 25 °C. Note: glassy…

Q4:- Compare between thermoplastic and thermosetting polymers.

A continuous and aligned fiber-reinforced composite having a cross-sectional area of 1200 mm² is subjected to an external tensile load. If the stresses sustained by the fiber and matrix phases are 152 and 2.27 MPa, respectively, the force sustained by the fiber phase is 72300 N, and the total longitudinal strain is 0.00143, determine the following: (a) The force sustained by the matrix phase (in N). i (b) The modulus of elasticity of the composite material in the longitudinal direction (in GPa). i N i (c) The modulus of elasticity for the fiber phase (in GPa). GPa i GPa (d) The modulus of elasticity for the matrix phase (in GPa). GPa

Describe, giving an example, how annealing affects the dynamic-mechanical thermal (DMT) properties of crystalline thermoplastics.

An epoxy (E=2.7GPA) is reinforced with carbon fiber with module of elasticity equal to 260 GPa. Design a composite with a longitudinal elastic modulus of 160 GPa. Select one: a. Vm = 70 vol%, Vf = 30 vol% b. Vm = 40 vol%, Vf = 50 vol% C. Vm = 39 vol%, Vf = 61 vol% d. Vm = 62 vol%, Vf = 38 vol%

Which of the following are reasons why injection molding of thermosets is more difficult than injection molding of thermoplastics (two best answers): O allowances must be made for cross-linking of thermosets O barrel temperatures must be hotter for thermosets O cycle times are longer because of curing thermosets are denser O two injection units are required

What is referred to as being elastic perfectly plastic?