Measurement of hair tensile strength and combing properties MCQs With Answer

Measurement of hair tensile strength and combing properties is a core topic for B.Pharm students studying cosmetic and hair-care science. This introduction covers key concepts: tensile testing of hair fibers, combing force and friction, instruments such as universal testing machines and single-fiber testers, parameters like breaking load, elongation at break, Young’s modulus, gauge length and strain rate, and the influence of humidity, chemical treatments and cuticle damage on mechanical behavior. Understanding sample preparation, cross-sectional area measurement and interpretation of stress–strain curves helps design safer, effective hair-care formulations and evaluate product claims. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What does hair tensile strength primarily measure?

• The electric conductivity of hair
• The maximum force a hair fiber can withstand before breaking
• The thermal resistance of hair
• The color stability under UV exposure

Correct Answer: The maximum force a hair fiber can withstand before breaking

Q2. Which unit is commonly used to report breaking force in hair tensile tests?

• Pascal-seconds (Pa·s)
• Newtons (N)
• Milliliters (mL)
• Degrees Celsius (°C)

Correct Answer: Newtons (N)

Q3. What is Young’s modulus for a hair fiber indicative of?

• The fiber’s electrical charge
• Its stiffness or elastic modulus in the linear region of stress–strain curve
• The diameter variability along the fiber
• The amount of surface lipids

Correct Answer: Its stiffness or elastic modulus in the linear region of stress–strain curve

Q4. Which instrument is typically used for single-fiber tensile testing?

• Spectrophotometer
• Universal testing machine (e.g., Instron)
• pH meter
• Gas chromatograph

Correct Answer: Universal testing machine (e.g., Instron)

Q5. Why is cross-sectional area (CSA) measurement important in tensile testing?

• To calculate volumetric swelling
• To convert breaking force into stress (e.g., MPa) for comparison
• To identify chemical composition
• To determine cuticle thickness only

Correct Answer: To convert breaking force into stress (e.g., MPa) for comparison

Q6. Which parameter describes the length change of hair at break relative to original length?

• Strain or elongation at break
• Thermal expansion coefficient
• Diffusion coefficient
• Surface energy

Correct Answer: Strain or elongation at break

Q7. How does humidity typically affect hair tensile properties?

• Higher humidity usually makes hair stiffer and more brittle
• Humidity has no effect on hair mechanics
• Higher humidity generally plasticizes hair, reducing stiffness and increasing elongation
• Lower humidity always increases elongation at break

Correct Answer: Higher humidity generally plasticizes hair, reducing stiffness and increasing elongation

Q8. Which sample preparation factor critically influences tensile results?

• Color of the hair only
• Gauge length and preconditioning (tension, humidity)
• Type of shampoo used years ago
• Ambient light during testing

Correct Answer: Gauge length and preconditioning (tension, humidity)

Q9. What does the stress–strain curve of a hair fiber reveal?

• Only the chemical composition
• Mechanical behavior including elastic region, yield and failure
• The combing force required for wigs
• The amount of sebum present

Correct Answer: Mechanical behavior including elastic region, yield and failure

Q10. Which of the following treatments typically decreases hair tensile strength?

• Hydrating with water only
• Bleaching and harsh chemical treatments
• Conditioner application
• Low-temperature drying

Correct Answer: Bleaching and harsh chemical treatments

Q11. In combing tests, what does combing force measure?

• The optical clarity of hair bundles
• The resistance encountered when a comb passes through hair
• The pH of hair surface
• The tensile strength of individual fibers

Correct Answer: The resistance encountered when a comb passes through hair

Q12. Which device is used to measure combing force and frictional resistance?

• Combinator / combing machine or tribometer adapted for hair
• Microscope only
• Mass spectrometer
• Refractometer

Correct Answer: Combinator / combing machine or tribometer adapted for hair

Q13. What is meant by wet combability?

• Resistance to combing after hair has been wetted
• The hair’s colorfastness in water
• Electrical conductivity when wet
• The time hair takes to dry

Correct Answer: Resistance to combing after hair has been wetted

Q14. Why are conditioners evaluated using combing force tests?

• To measure fragrance retention
• To quantify reduction in combing resistance and improve slip
• To determine viscosity
• To measure mineral content

Correct Answer: To quantify reduction in combing resistance and improve slip

Q15. Which microstructural hair feature most strongly influences tensile strength?

• Cuticle lipid composition only
• Cortex keratin structure and integrity
• Number of hair follicles on the scalp
• Surface dust particles

Correct Answer: Cortex keratin structure and integrity

Q16. How does repeated combing contribute to hair damage?

• It polishes the cuticle making hair stronger
• It can cause cuticle abrasion, fiber breakage and increased split ends
• It increases internal moisture content permanently
• It changes hair color chemically

Correct Answer: It can cause cuticle abrasion, fiber breakage and increased split ends

Q17. What is the effect of surfactants on hair tensile and combing properties?

• All surfactants uniformly strengthen hair
• Some surfactants strip lipids and increase friction, while conditioners mitigate this
• Surfactants only affect scalp pH, not hair mechanics
• Surfactants make hair fully waterproof

Correct Answer: Some surfactants strip lipids and increase friction, while conditioners mitigate this

Q18. Which parameter is important to control to get reproducible single-fiber tensile tests?

• Color of testing room walls
• Strain rate (extension speed) during testing
• Type of comb used on the tester
• Time of day

Correct Answer: Strain rate (extension speed) during testing

Q19. What does a lower breaking stress (MPa) indicate about hair?

• Higher mechanical strength
• Lower resistance to fracture under load
• Greater electrical conductivity
• Increased thermal stability

Correct Answer: Lower resistance to fracture under load

Q20. Which analytical technique helps measure hair cross-sectional area accurately?

• Optical microscopy with image analysis
• Gas chromatography
• pH titration
• UV–Vis spectroscopy

Correct Answer: Optical microscopy with image analysis

Q21. Why compare wet and dry tensile tests?

• To evaluate hair color change in water
• To understand how hydration affects mechanical properties and product performance
• To determine scalp oiliness
• To measure bacterial contamination

Correct Answer: To understand how hydration affects mechanical properties and product performance

Q22. What role do plasticizers or conditioning agents play in combing tests?

• They usually increase combing resistance
• They reduce friction between fibers and lower combing force
• They only alter hair color
• They make hair electrically charged

Correct Answer: They reduce friction between fibers and lower combing force

Q23. Which measurement indicates energy absorbed by hair before failure?

• Break point color index
• Toughness (area under stress–strain curve)
• Surface reflectance
• Comb tooth count

Correct Answer: Toughness (area under stress–strain curve)

Q24. What can increased variability in tensile results across fibers suggest?

• Uniform molecular structure
• Heterogeneity in fiber diameter, damage or testing inconsistencies
• Perfect sample preparation
• Stable humidity control

Correct Answer: Heterogeneity in fiber diameter, damage or testing inconsistencies

Q25. Which of these is a common artifact to avoid during clamping in tensile tests?

• Proper alignment of sample
• Slippage or crushing of the fiber by clamps
• Maintaining gauge length
• Calibrating load cell

Correct Answer: Slippage or crushing of the fiber by clamps

Q26. What is a combing torque measurement useful for?

• Assessing rotational resistance and entanglement in hair bundles
• Measuring acidity of conditioners
• Quantifying UV absorption
• Counting medulla segments

Correct Answer: Assessing rotational resistance and entanglement in hair bundles

Q27. Which factor does NOT typically influence combing force?

• Bundle density
• Comb speed and design
• Color of shampoo bottle
• Surface friction between fibers

Correct Answer: Color of shampoo bottle

Q28. In tensile testing, what is meant by ‘gauge length’?

• The length of the entire hair bundle
• The initial clamped length of the fiber between grips
• The thickness of the clamp
• Distance to the lab bench

Correct Answer: The initial clamped length of the fiber between grips

Q29. Which observation suggests cuticle damage after a treatment?

• Decreased combing force and smoother surface
• Increased surface roughness, raised cuticle edges and higher friction
• Complete waterproofing
• Increased medulla count

Correct Answer: Increased surface roughness, raised cuticle edges and higher friction

Q30. Why is replicating environmental conditions important in reporting hair mechanical data?

• Because hair properties are invariant to environment
• Because temperature and humidity strongly affect tensile and combing measurements
• Only to improve visual presentation of data
• To calibrate color instruments

Correct Answer: Because temperature and humidity strongly affect tensile and combing measurements

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