PKG-322 Lecture 9: Barrier and Mechanical Properties

What test is used to measure water resistance of paper?

The Cobb Test

What is the TAPPI standard for the Cobb Test?

TAPPI T441

What does the Cobb Test measure?

The mass of water absorbed per unit area over a set time

What units are used for Cobb values?

g/m^2

How is the Cobb value calculated?

(Wwet − Wdry) / Area × 100

What does a high Cobb value indicate?

Poor water resistance

What are the two main methods for measuring grease resistance?

Kit Test and Cobb Oil Absorption Test

What is the Kit Test used for grease resistance?

It simulates grease penetration using standard solutions

What is the TAPPI standard for the Kit Test?

TAPPI T559

What determines the kit rating in the Kit Test?

The highest-numbered solution that does not stain the paper

What is the Cobb Oil Absorption Test?

A test that measures oil absorbed over time similar to the water Cobb test

What TAPPI standard is used for Cobb Oil Absorption?

TAPPI T441

What is air permeance?

A measure of how easily air passes through paper

What does the Gurley air permeance test measure?

The time for a fixed volume of air to pass through paper

What TAPPI standard applies to the Gurley method?

TAPPI T460

What units are reported in the Gurley test?

Seconds

What does the Bendtsen air permeance method measure?

The air leakage rate through paper

What standard applies to the Bendtsen method?

ISO 5636-3

What units are used for Bendtsen air permeance?

mL/min or µm/(Pa·s)

What is Water Vapor Transmission Rate (WVTR)?

The amount of water vapor passing through a material per area per time

What units are used for WVTR?

g/m^2·day

How is WVTR calculated?

Weight gain / (area × time)

What standards are used for WVTR testing?

TAPPI T464 or ASTM F3299

What is Oxygen Transmission Rate (OTR)?

The amount of oxygen passing through a material per area per day

What units are used for OTR?

cc/m^2·day

How is OTR calculated?

Oxygen volume / (area × time)

What standards are used for OTR testing?

ASTM D3985 or ASTM F1927

What is permeance?

Transmission rate divided by partial pressure difference

How is permeance calculated?

WVTR or OTR divided by ΔP

What is permeability?

Permeance multiplied by material thickness

What is normalized WVTR or OTR?

Transmission rate multiplied by thickness

Why do paper properties differ between MD and CD?

Fiber orientation during manufacturing

How are fibers oriented in the machine direction (MD)?

More oriented

How are fibers oriented in the cross direction (CD)?

Less oriented

Which direction has higher stiffness and tensile strength?

Machine direction (MD)

Which direction has higher ring and edge crush strength?

Machine direction (MD)

Which direction has higher tear resistance?

Cross direction (CD)

Which direction has higher elongation?

Cross direction (CD)

How can MD be identified using moisture?

The paper curls around an axis parallel to MD

How can MD be identified by tearing?

MD tears more easily than CD

How can MD be identified by bending?

MD feels stiffer than CD

What is the coefficient of friction (COF)?

A measure of resistance to sliding

Why is COF important in packaging?

It affects conveyor performance and load stability

What problems are caused by high COF?

Conveyor jams and miss picks

What problems are caused by low COF?

Load instability

What is static COF?

The force required to start motion

What method measures static COF?

Inclined-plane method

What TAPPI standard measures static COF?

TAPPI T815

How is static COF calculated?

COFs = tan(θ)

What is kinetic COF?

The force required to maintain motion

What method measures kinetic COF?

Horizontal-plane method

What TAPPI standard measures kinetic COF?

TAPPI T816

How is kinetic COF calculated?

COFk = F / (m × g)

What test measures tear resistance?

Tear Resistance Test

What TAPPI standard applies to tear resistance?

TAPPI T414

What instrument is used to measure tear resistance?

Elmendorf pendulum tester

What does puncture resistance measure?

The energy required to penetrate board

What TAPPI standard applies to puncture resistance?

TAPPI T803

What units are used for puncture resistance?

Beach units

How much energy is one Beach unit equal to?

0.0299 Joules

What factors affect paper stiffness?

Thickness, fiber orientation, basis weight, and coatings

Why is stiffness important in packaging?

It affects carton forming and stacking strength

What standard measures bending resistance?

TAPPI T489

What is Taber stiffness?

The bending moment required to bend a sample to a set angle

What angles are used in Taber stiffness testing?

15° or 7.5°

What is bending stiffness (Sb)?

A calculated value representing resistance to bending

What standard evaluates score or crease quality?

TAPPI T829

What is score ratio?

The force to bend an unscored sample divided by the force to bend a scored sample

How is score ratio calculated?

(Unscored force / Scored force) × 100

What does a lower score ratio indicate?

Better crease quality