CPT Flexible Packaging Technologies 2 — Questions and Answers
Question 1: Which lamination process applies adhesive to one substrate and bonds it to a second substrate under pressure without using heat?
- Thermal lamination
- Solventless lamination (Correct answer)
- Extrusion lamination
- Wet bond lamination
Correct answer: Solventless lamination
Solventless lamination uses a 100% solids adhesive system that requires no drying oven, bonding substrates at room or slightly elevated temperature under nip pressure.
Question 2: In flexible packaging, what is the primary purpose of a slip additive incorporated into a polyethylene film?
- Increase tensile strength
- Improve heat seal initiation
- Reduce coefficient of friction for handling and machinability (Correct answer)
- Enhance oxygen barrier properties
Correct answer: Reduce coefficient of friction for handling and machinability
Slip additives migrate to the film surface and reduce COF, allowing the film to run smoothly on packaging equipment and preventing blocking.
Question 3: A flexible pouch fails a burst test at the bottom seal but passes at the side seals. What is the most likely root cause?
- Incorrect film gauge
- Insufficient dwell time at the bottom seal bar (Correct answer)
- Contaminated film surface on side panels
- Excessive cooling air on the bottom seal
Correct answer: Insufficient dwell time at the bottom seal bar
Insufficient dwell time prevents complete polymer fusion at the bottom seal bar, creating a weaker bond that fails under internal pressure before properly formed side seals.
Question 4: What does the term 'retort packaging' specifically refer to in flexible packaging?
- Packaging designed for microwave reheating only
- Flexible pouches or trays that withstand high-temperature sterilization (typically 121°C) (Correct answer)
- Cold-filled aseptic packaging systems
- Packaging with integral oxygen scavengers
Correct answer: Flexible pouches or trays that withstand high-temperature sterilization (typically 121°C)
Retort packaging withstands sterilization temperatures of 121°C (250°F) or higher under pressure, allowing shelf-stable food products without refrigeration.
Question 5: Which property of EVOH film is most significantly reduced when the material is exposed to high humidity conditions?
- Tensile strength
- Optical clarity
- Oxygen barrier performance (Correct answer)
- Heat seal strength
Correct answer: Oxygen barrier performance
EVOH is highly moisture-sensitive; absorbed water disrupts the polymer chain interaction that provides its excellent oxygen barrier, causing barrier performance to drop dramatically at high RH.
Question 6: In gravure printing on flexible packaging films, what is the function of the doctor blade?
- Apply ink to the engraved cylinder
- Remove excess ink from the non-engraved cylinder surface (Correct answer)
- Control substrate tension through the press
- Activate the corona treatment on the film
Correct answer: Remove excess ink from the non-engraved cylinder surface
The doctor blade wipes excess ink from the smooth land areas of the gravure cylinder, leaving ink only in the engraved cells to be transferred to the substrate.
Question 7: Which flexible packaging structure would provide the highest level of moisture barrier for a dry snack product?
- PET / adhesive / LDPE
- OPP / adhesive / metallized OPP / adhesive / LLDPE (Correct answer)
- Nylon / adhesive / LDPE
- PET / adhesive / nylon / adhesive / LDPE
Correct answer: OPP / adhesive / metallized OPP / adhesive / LLDPE
Metallized OPP provides an exceptional moisture vapor transmission rate barrier, and combining it with OPP and LLDPE in a laminate gives the best overall moisture protection for dry snacks.
CPT Flexible Packaging Technologies 2
Which lamination process applies adhesive to one substrate and bonds it to a second substrate under pressure without using heat?