CPT Packaging Materials & Processes 3 — Questions and Answers
Question 1: In rotogravure printing used for flexible packaging, the image is carried by:
- Raised relief areas on the plate
- Recessed cells etched into a cylinder (Correct answer)
- Openings in a mesh screen
- Charged electrostatic areas
Correct answer: Recessed cells etched into a cylinder
Rotogravure uses tiny recessed cells engraved into a cylinder to hold ink, which is then transferred to the substrate.
Question 2: Which test method measures the force required to separate two sealed plies of flexible packaging film?
- Elmendorf tear test
- Peel adhesion test (Correct answer)
- Gurley porosity test
- Mullen burst test
Correct answer: Peel adhesion test
The peel adhesion test (ASTM F88) measures seal strength by pulling apart bonded film layers at a controlled angle and speed.
Question 3: Which glass forming process is most suitable for producing wide-mouth jars used for peanut butter?
- Press-and-blow process (Correct answer)
- Blow-and-blow process
- Float glass process
- Tube drawing process
Correct answer: Press-and-blow process
The press-and-blow process uses a plunger to press the gob into a parison mold, enabling production of wide-mouth containers with uniform wall thickness.
Question 4: What property of aluminum foil makes it the preferred material for blister packaging of pharmaceutical tablets?
- High tensile strength
- Near-zero moisture vapor transmission rate (Correct answer)
- Excellent heat sealing ability
- Low cost per unit area
Correct answer: Near-zero moisture vapor transmission rate
Aluminum foil provides near-zero MVTR and OTR, protecting moisture-sensitive pharmaceutical products throughout their shelf life.
Question 5: In injection molding, what causes 'sink marks' on the surface of a plastic container?
- Excessive mold temperature
- Insufficient packing pressure after injection (Correct answer)
- Too-rapid ejection from the mold
- High melt temperature
Correct answer: Insufficient packing pressure after injection
Sink marks form when insufficient packing pressure allows the outer skin to collapse inward as the thick interior cools and shrinks.
Question 6: What is the McKee formula used to estimate in corrugated packaging design?
- Moisture vapor transmission rate
- Box compression strength (Correct answer)
- Drop impact resistance
- Printing ink adhesion
Correct answer: Box compression strength
The McKee formula estimates box compression strength (BCT) based on edgewise crush test (ECT) values, box perimeter, and caliper.
Question 7: Which metal can coating system is specifically designed to prevent sulfur staining in canned protein products like tuna?
- Oleoresinous (C-enamel) coating (Correct answer)
- Epoxy-phenolic coating
- Vinyl coating
- Acrylic coating
Correct answer: Oleoresinous (C-enamel) coating
C-enamel (oleoresinous) coatings contain zinc oxide that reacts preferentially with sulfur compounds from proteins, preventing black iron sulfide staining.
CPT Packaging Materials & Processes 3
In rotogravure printing used for flexible packaging, the image is carried by: