CENTRAL INSTITUTE OF PLASTICS ENGINEERING & TECHNOLOGY
Question Bank
3 MARK --- QUESTION
4/5 MARK ----QUESTION
COURSE : DPT
SEMESTER : IV
SUBJECT : Plastics Testing – I
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1. What are the observations made by burning test during the identification of plastics?
Ans: I) Flame characteristics
II) Self-extinguishing and continues to burn
III) Speed of burning
IV) Smoke and presence of soot in air
V) Melting, Dripping, charging, boiling
VI) Odour (Smell)
2. Write down the full form of (any two):
a) ISO b) BIS c) NABL
Ans: a) ISO: - International Organization for Standardization
a. b) BIS: - Bureau of Indian Standard
b. c) NABL: - National Accreditation Board for Testing and Calibration Laboratories.
3. Write down the different specimen preparation method to conduct the test.
Ans: Injection Moulding, Compression moulding, Two roll Mill, Contour Cutter, Transfer Moulding,
Punching
4. How to identify the unknown plastics by solubility test ?
Ans: About 100 mg of sample is taken and 10 ml of approximate solvent is added and stirred occasionally. The contents are shaken in a test tube and observed for few hours. Swelling may occur
before complete dissolution of the polymer.
5. Write a short note on MFI.
Ans: It is defined as the mass of polymer in grams flowing in 10mins through a capillary of specific
diameter of (2.06 + 0.0051mm) and length (8 + 0.025mm) by a pressure applied using a piston. MFI
is an assessment of average molecular mass and is an inverse measure of the melt viscosity; i.e.
high melt flow rate corresponds to low molecular weight.
6. Define Bulk density.
Ans: It is defined as the mass of many particles of the material divided by the total volume of they occupy. It can be expressed in Kg/m.
7. What are the significance of MFI test and What is the standard test method using for MFI?
Ans: For MFI - ASTMD 1238
- Uniformity of flow, Quality check, Differentiation in polymer grades, Determination of the extent of degradation, Prediction of molecular weight etc.
8. . Write the formula for calculating Melt flow rate.
Ans:
𝐹𝑙𝑜𝑤 𝑅𝑎𝑡𝑒 =𝑚/𝑡× 600
Where, m = mass of the extrudate (g)
t = reference time (s)
9. What are the factors affecting test result for melt flow rate?
Ans: Factors affecting test result for melt flow rate are
a) Preheat time
b) Presence of moisture
c) Packing
d) Volume of sample
10. What is the test method and significance of Cup Flow test?
Ans: The test method is ASTMD 731 and test for measuring the flow properties of thermoset
materials. A standard mould is charged with preweighed material and the mold is closed using
sufficient pressure to form a required cup. Minimum pressure required to mold a standard cup and
the time required to close the mould fully are determined.
11. What are the factors affecting test result for cup flow test?
Ans: Factors affecting test result for cup flow test are
a) Resin types
b) Types of filler
c) Storage time
12. What is the significance and test method of Spiral Flow test?
Ans: A method for determining the flow properties of a plastic material based on the distance it will
flow under controlled conditions of pressure and temperature along the path of a spiral cavity using a
controlled charge mess. The test method is ASTMD 3123
13. What are the factors affecting Dilute solution viscosity (DSV)?
Ans: Flow time, Temperature, Concentration, Purity, Air bubbles
14. Write down the pre-drying temperature for the following polymers?
a) ABS b) Nylon c) PET
Ans: Pre-drying temperature for ABS – 88 ͦC
Nylon - 60-80 ͦC
15. What are the limitation of dilute solution viscosity?
Ans: Limitation for dilute solution viscosity are :
a) High purity is required to obtain accurate results.
b) These data alone may be insufficient in predicating the processing
behaviour of polymer.
c) Additives drastically affect the viscosity of polymer solution.
d) The measurements are based on a very dilute solution.
16. What are the melt characteristics and odour of the following materials.
Polypropylene (PP), Polystyrene (PS)
Ans: Material Melt characteristics Odour such as:
PP Melts and drips slowly lubricating oil smell
PS Softens but doesn’t drip Sweet smell of marigold
17. Write down the ASTMD test method to conduct the tensile strength and the significance of tensile
strength.
Ans: For Tensile ASTMD -638
- To know the tensile strength, Percentage of elongation, Tensile modulus,
Stiffness, Toughness, Quality control of the product.
18. Write the definition of Tensile strength, Tensile modulus and Yield point.
Ans: Tensile strength – Ultimate strength of a material subjected to tensile loading.
Tensile modulus –The ratio of tensile stress to corresponding strain at the maximum load within
a) Proportional limits is called tensile modulus.
Yield point – The point on the stress-strain curve at which increase in strain occurs without an
increase in stress.
19. Write short note on Yield strength and Young’s modulus.
Ans: Yield strength- The stress at which a material exhibits a specified limiting deviation from the
proportionality of stress to strain.
Young’s Modulus – The ratio of tensile stress to tensile strain below the proportional limit.
20. Write down the different type of speed used to conduct the tensile strength.
Ans: Speed - A - 1 mm/min
Speed - B- 50 mm/min
Speed - C- 50 mm /min
Speed - D- 1000 mm/min
Speed - E- 500 mm/min
21. Which instruments are used to conduct the tensile strength?
Ans: Universal testing machine with tensile test fixture, Extensometer, Micrometre, Vernier calliper,
steel rule.
22. What are the factor affecting test result for tensile strength.
Ans: Specimen Preparation technique, Rate of strain, Test temperature
23. What is the standard test method and specimen size for flexural strength? Define the types of
methods for determination of flexural strength.
Ans: Test method – ASTMD 790
Specimen size 127 x 12.7 x 6.4 mm
Types- i) Three point loading system
ii) Four point loading system
24. Define Flexural strength and flexural modulus.
Ans: Flexural strength- It is the ability of a material to withstand bending forces applied
perpendicular to itslongitudinal axis.
Flexural Modulus- Within the elastic limit, the ratio of the applied stress on a test specimen in
flexure to
a) the corresponding strain in the outer most fibre of the specimen. Flexural modulus is
b) the measure of relative stiffness.
25. What are the significance of the flexural strength?
Ans: Classify or rank the material with respect to bending strength and stiffness.
26. What are the factors affected to the test result for flexural strength?
Ans: Factors affected for the test result are Specimen preparation technique, Temperature, Test
Condition, and Increase of anisotropy.
27. Define compressive strength, the specimen size with standard test method?
Ans: The ability of a material to resist forces that tends to crush or compress is called compressive
strength.It is expressed in N/mm
To conduct compressive strength cylindrical shape of size 12.7mm x12.7mm x 25.4mm and For
Rectangular block of 12.5 x 12.5 x25.4 mm.
Test Method – ASTM D 695
28. Write the formula for calculating the compressive strength. Write the condition temperature for
conditioning of the specimen.
Ans: Compressive strength = Force (N) / Area (mm2).
For conditioning the sample should be conditioned at 23 + 20C and 50 + 50% RH for 40hrs.
29. What are the factors affecting the compressive properties and how?
Ans: i) Test specimen preparation method- Molded specimen shows better compressive strength
and modulus than those prepared by machining or lamination process.
ii) Test speed- with the increasing speed of testing, compressive strength and lowest strength are
Observed to increase.
a. iii) Test temperature & humidity – The higher the temperature, the lower the strength.
30. What are the major types of impact tests for plastics?
Ans: 3 major types; i) Pendulum Impact test ii) Drop weight Impact iii) Instrumented Impact
31. Define Impact strength and Notch sensitivity.
Ans: Impact strength- It is defined as the ability to resist the fracture under shock loading or ability of
material
a) to resist the fracture under stress applied at high speed.
Notch sensitivity- Measure of reduction in load carrying ability caused by stress concentration in
specimen. Brittle plastics are move notch sensitive than ductile plastics.
32. What are the test significances for Impact strength?
Ans: To know the toughness of material, resistance to speed loading, research and development,
quality control of material.
33. Write down the test method for impact test and the notch dimension for notched sample.
Ans: Test method for Izod impact test is ASTM D 256.
- The angle of notch is 450± 10 with a radius of 0.25 mm. The depth of notch is generally 2.54 mm.
34. What is the laboratory condition of test specimen for short term mechanical test?
Ans: For ASTM = 23 ± 20 C and 50+5%RH, For ISO = 27+20 C 65+5%RH
35. What is Secant modulus, Toughness and Stiffness?
Ans: Secant Modulus: The ratio of stress to the corresponding strain at any specified point on the
stress
a) strain curve is defined as secant modulus.
Toughness - The extent to which a material absorbs energy without fracture. The area under a
stress-
- strain diagram is also a measure of toughness of a material.
Stiffness – it is defined as the resistance to deformation.
36. What are the factors affecting Impact strength?
Ans: i) Rate of loading
ii) Notch sensitivity
iii) Temperature
iv) Orientation
v) Processing condition
vi) Degree of crystallinity and molecular weight
37. Write down the test method an specimen size for shear strength.
Ans: Test method for shear strength is ASTM D 732.
- Specimen form of disc of 50 mm diameter and thickness range of 0.125 mm to 12.5 mm.
38. What are the factors affected for shear strength?
Ans: Shear strength of material depends upon,
I) Nature of material,
II) Sharpness of shear tool,
III) Thickness of specimen
IV) Test temperature
39. What is hardness? What is the standard method for calculating the hardness of plastics and
electrical insulating material?
Ans: Hardness- It is defined as the resistance of material to indentation, penetration, scratches,
deformation
- and particularly permanent deformation.
- Rockwell hardness – ASTMD 785
40. What are the significance for hardness test?
Ans: It is used to measure the surface durability, it can also be used to predict the length of time that
that the product will give a trouble free service, quality control of the product.
41. What are the test method for Durometer & Barcol hardness?
Ans: Test method for Durometer hardness ASTM D2240
Test method for Barcol hardness ASTM D2583
42. What are the various type of hardness?
Ans: Various type of hardness are
a) Rockwell hardness test.
b) Durometer hardness test.
c) Barcol hardness test
d) Brinley hardness test.a
e) Knoop hardness scale.
f) Vicker scale.
43. What is the difference between Shore A and Shore D?
Ans: Shore A Used for relatively soft and Shore D Used for hard materials
44. What are the factors affected for creep?
Ans: Factors affected for creep test are
a) Stress, b) Temperature.
45. Define thermal expansion?
Ans: The co-efficient of linear thermal expansion (CLTE) measures the change in length per unit
length of a material, per degree change in temperature. Expressed as in/in/F or cm/cm/C.
- CLTE is used to calculate the dimensional change resulting from thermal expansion.
46. . Define co-efficient of thermal expansion?
Ans: The maximum load sustained by a test specimen in a compressive test divided by the original
cross section area of the specimen.
47. What are the factors affecting thermal expansion of polymeric material?
Ans: Thermal expansion is sustainably affected by the use of additives, especially fillers and
depends on their quality and amount of filler loading. The co-efficient of thermal expansion lowers
with increasing amount of filler.
48. . Define Vicat Softening Point (VSP). What is the standard test method for VSP?
Ans: Vicat Softening Point (VSP) – The temperature at which a flat ended needle of 1 sq mm circular or square cross section will penetrate a thermoplastic specimen to a depth of 1mm under a specified load using a uniform rate of temperature rises.
- Test method – ASTM D 1525
49. Define thermal conductivity?
Ans: Thermal conductivity - The ability of a material to conduct heat. The coefficient of thermal
conductivity is expressed as the quantity of heat that passes through a unit cube of the substance in
a given unit of time when the difference in temperature of the two faces is 1 degree.
50. What is Heat Deflection Temperature (HDT)? Write the standard method for HDT.
Ans: The temperature at which the a standard test bar (127mm×13mm×3mm) deflects 0.01” under a
stated load of either 66psi (0.45MPa) or 264psi (1.82MPa) when heated at a rate of 20C/min.
- HDT is a measure of a material’s ability to perform for a short time at a elevated
temperature while supporting a load.
- Test method = ASTM D 648
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