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Heat Sealing – How to Qualify a Heat Seal Product.

Home Heat Sealing – How to Qualify a Heat Seal Product.

Product Qualifying Questions for – HEAT SEAL Adhesives.

Some questions below that you may use to explore a potential’s capabilities regarding Heat Seal Coating

1 What is the function of heat seal coating?

  1. Heat seal coating
  2. Gloss over lacquer with bonding capabilities
  3. In-mould labelling
  4. Lidding
  5. Blister pack coating
  6. Skin pack coating
  7. Primer
  8. Adhesive
  9. Other, Explain.

2 What Substrates are being coated?

  1. Film, type, treatment level, gauge, PVC, PET, PE, PP, PS, HIPS
  2. Paper
  3. Metallized film, foil
  4. Blisters – PET, CAP, CAB, CA, PVC, PS, Surlyn, EAA

3 What type of bond is required?

  1. Peelable gm/in at 90 degree or 180 degree peel angle e.g. at 90 degree 600 gm/in – at 180 degree 1200 gm/in
  2. Destruct type bond
  3. What is the rate of peel 12”/min, 2”/min?
  4. Does it matter if heat seat coating

4 What are the sealing conditions used?

  1. Heat seal temperature?
  2. Dwell time?
  3. Pressure?
  4. What is the minimum heat seal temperature, pressure and dwell?

5 What are the coating conditions?

  1. What is the required dry coat weight?
  2. Is a smoothing bar employed?
  3. Is bar driven in machine or reverse machine direction?
  4. Is the bar heated?
  5. Does the bar oscillate?

6 What is the set up in the fountain ?

  1. What is the cylinder etch (inch/inch) (quad microns depth is best)? Must deliver 2.5-5 lb. /ream dry. Hot melt up to 20 lb./ream
  2. What is pan temperature?
  3. Are pan contents recirculated (link ink) to keep temperature relatively constant?
  4. Is cylinder heated? Cylinder should ideally run 10 degree F higher than fountain temperature to ensure good release of the coating from the gravure cylinder. (gel lacquer)
  5. Fountain temperature 120-140 degree F or 18-20 sec. #2 Zahn (for gel lacquer).
  6. Fountain pan 300-375 degree F hot melt.

7 Is F.D.A. required?

  1. Direct?
  2. Indirect?
  3. Not required?
  4. Aseptic sterilization
  5. Aseptic hydrogen peroxide dip at room temp? Or 50 degree C?

8 What must heat seal coating resist?

  1. Water, milk, products, lactic acid
  2. Grease, oil
  3. Tatar sauce
  4. Jams, jellies
  5. Vinegar
  6. Hot fill
  7. Freezing temperatures
  8. Vacuum (airline standard) number of inches of Mercury vacuum over a specified period of time, eg 12” Hg for two minutes without leaking

9 Viscosity of product supplied

How do they reduce viscosity? Air motor mixer? Wood paddles?

10 What is press-ready viscosity/solids, do they prefer to run?

(#2 Zahn 18-20 sec. usually is best) Quotes cps and #2 Zahn + temperature or Brookfield in cps.

11 What are dying conditions?

  1. Is oven zoned? How many zones?
  2. What is oven temperature profile, e.g. 3 zone oven
  3. Zone 1. 160-180 degree F
  4. 250-280 degree F
  5. 240-260 degree F
  6. Do they run using dries on each station (some gravure presses and all Flexor presses.)
  7.  What is maximum web temperature obtained?
  8. Is web temperature to fuse or cause coating “flow” to give maximum gloss?
  9. Is a chill roll employed just prior to roll up?

12 Further processing:

  1. Is surface that heat seal coating is rolled up against going to be further processed by:
  2. Being printed
  3. Being glued
  • Is wax offset a possibility interfering with ink or adhesive “wet out”

13 Press Capabilities

Are reversing capabilities available on press so coating can put on in line with print on one pass?

14 Blocking Conditions

  1. What block resistance is required? (500 psi, 24hr. @ RT)
  2. What are the tension requirements on rewind (loose or tight)?
  3. Will web be slit prior to sending out to customer?
  4. What type of ink is the coating going over?
  5. High slip inks may bloom slip additive through heat seal causing blocking or offset problems as described in 12 (b)
  6. Are you surface printing or reverse printing

  1. Slip conditions
  1. Is there a “static” COF requirement? (coefficient of friction)
  2. What is slip requirement? 0.1 to 0.5
  3. Is lip COP taken?
  4. Coating to coating
  5. Coating to stainless steel

  1. Web appearance

Is coating clarity required?

  1. Blister pack conditions
  1. PVC- 80% market; PETG – 15% market; PS,CA,CAP,CAB – 5% market
  2. Dwell, coating weight, heat seal conditions
  3. Thickness or gauge of board
  4. Pressure

  1. Are there any coating weight restrictions on flexo-press?

  1. What are maximum coat weight capabilities with existing dries in place?
  2. Do you have any other print or color stations available to double or triple hit heat seal coating on web

  1. Do you have capability of gravure or extrusion coating hot melt on web?

  1. Heated fountain and cylinder (oil) gravure
  2. PE extruder with barrel and screw suitable to run high EVA content PE

  • Sealing conditions

How important is hot tack in heat seal operation?

  • costing

Are their applied cost/ream restrictions?

  • Can solvent based lacquers/gel lacquers be used?
  1. EPA restrictions on solvent
  2. Odor retention problem

  • Pass/Fail Criteria

Please outline specific test used to pass or fail our coating

  • Substrates
  1. Can you supply coated substrates as a control?
  2. Can you supply uncoated web for our screening test?
  3. Can you supply a sample of competitive product?
  4. Customers sealing equipment

  1. Please advise us of typical sealing equipment used by customer.
  2. Does it stretch the heat seal layer prior to heat sealing?
  3. Does It heat seal occur in one or two hits of platen?
  4. Does second hit cut lidding material?

Need more information?  To speak with a technical representative about your application, and to request samples or pricing, please call 800-249-0337  or email us at

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