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QUIZ ?

  1. Is the label to be permanent or removable?
  2. What is the composition of the substrate?
  3. What is the shape of the substrate surface?
  4. Are there any special application or exposure conditions that the label must withstand?
  5. Is the application surface clean or contaminated?
  6. Is there any plasticizer present that will deteriorate the adhesive?
 
1. Is the label to be permanent or removable?

Permanent: The bond to the substrate makes removal difficult or impossible without distorting the facestock or damaging the substrate.
Removable: The bond to the substrate makes removal easy without damage to the facestock or substrate.

- Considerations with removable adhesives
- Make sure that the surface on which the label is to be applied is strong enough to withstand label removal. Some papers and board stocks require special considerations.
- Label size is important with removable labels. Larger labels will require a stronger facestock to ensure removability.
- Small labels with a stiff facestock may not adhere well to curved or irregular surfaces and may appear 'too removable'. Prior testing is always recommended.


2. What is the composition of the substrate?

The composition of the substrate that the label will be applied to can have an effect on the ultimate strength of the bond that the label will obtain.
It is important to identify the exact type of substrate being used. Specific identification of any substrate is needed.

- Plastic is not descriptive enough. The level of adhesion will vary with the type of 'plastic' being used: High Density Polyethylene, Low Density Polyethylene, Polypropylene, Vinyl, Polyester etc.

Plastic Description
Examples
Polyethylene Terephthalate Soft drink bottles, crystal clear squeezable bottles
High Density Polyethylene Milk jug bottles, semi rigid bottles
Vinyl (Polyviny Chloridel) Vinyl binders, bags
Low Density Polyethylene Plastic bags
Ploypropylene Diapers, straws
Polystyrene Expanded foam, casings for compact disks, Components for copiers.
Multi-Resin & Other Plastics  

On low surface energy materials, initial tack is the most important criteria. Adhesion levels may improve with longer dwell.

What is the texture of the substrate (the surface to which the label will be applied)?

The texture of a substrate can have an impact on the bond to the material as textured materials do not allow 100% contact of the adhesive you have purchased with your substrate - less contact; less bonding area; lower adhesion.

A rough/mottled surface may require a stronger bonding adhesive to maximise adhesion at contact area.

Adhesion to any substrate is achieved by the adhesive flowing into all areas of the substrate and "bonding" with them.

 


3. What is the shape of the substrate surface?

The shape of the substrate along with the size and stiffness of the label must be considered to ensure proper end use performance.

- Curved surfaces (approximately 25mm in diameter) will require an aggressive adhesive; combination of a high tack adhesive and flexible facestock with little or no memory.
- Compound curves will require a special label shape and a flexible facestock for conformability to the surface. Film generally performs better for compound curves.


4. Are there any special application or exposure conditions that the label must withstand?

Special conditions may be defined as: temperature extremes, outdoor weatherability, ultra-violet light exposure, sterilization, large amounts of humidity or moisture and exposure to solvent/cleaning agents.

Some other questions to consider:

- Will the label be exposed to large amounts of moisture? If so, a moisture resistant or wet strength facestock should be selected with gloss over-varnish.
- Will there be prolonged exposure to ultra-violet light? Long term exposure to U.V. light deteriorates rubber-based adhesives. Special adhesives may be needed if transparent facestocks are to be used or the labels are to last an exceptionally long time. Concentrated U.V. exposure will also affect the graphics on the label so this consideration is particularly important where long label life is desired.
- Will the label be exposed to elevated temperatures +90 degrees C for an extended period? If so, an acrylic adhesive combined with film or foil may be required.


5. Is the application surface clean or contaminated?

The cleanliness of the surface of the substrate when the label is applied will affect the ultimate adhesion of the label and the success of the application.

- Contamination from oil, grease, frost, dusts, dirt, moisture and release agents, are some causes of label failure. All keep the adhesive from contacting the actual surface!
- Mold Release Agents are another typical contaminate seen when labelling "plastics" and glass containers
- Consider the use of wrap around (overlap) labels where contamination is present and cannot be removed.


6. Is there any plasticizer present that will deteriorate the adhesive?

Plasticizer: Plasticizer is a component used in vinyl, which controls the degree of softness or pliability in the vinyl. A highly plasticized vinyl will be very soft and pliable while a low plasticized vinyl will be very stiff.

- A plasticizer in contact with some adhesives will degrade the adhesive bond strength. If may be necessary to use a plasticizer resistant adhesive. Pre-testing by accelerated aging and careful product selection is always advisable when the existence of plasticiser is suspected