TECHNICAL LITERATURE

TESTING OF SQUEEGEES

APOLAN - Polyurethane Screen Printing Squeegees were developed and improved over many years in actual printing environment, utilizing the most important principles of polymer chemistry.

IT IS IMPORTANT TO COMPARE PRODUCT FROM DIFFERENT MANUFACTURERS ON ACTUAL PRINTING PRESSES, NOT IN A GLASS JAR.

The three major requirements, abrasion resistance, solvent resistance and flex fatigue place contradicting requirements on the polymermatrix.

It is easy to formulate a squeegee for extreme low solvent-swell by increasing the crosslink in the polymer backbone. This will fail on the press due to a rapid, severe loss of mechanical properties under solvent attack, EVEN SO THE VOLUME SWELL IS LOW!

Abrasion resistance and good flex-fatigue demand a low crosslink, therefore some swell has to be tolerated.

 

Ultimately, the best polymer-back bone is achieved by controlled low crosslink and very high-linear-molecular-weight polymer in order to reduce swelling. While this is well-known in the better literature and has been subject of many discussions with polymer chemists of Bayer, Dupont, etc., the problem is to translate this concept into practice. Every squeegee made has to undergo the chemical reaction to cure to a polyurethane.

To achieve the above requires manufacturing technology, manufacturing discipline and strict machine processing. It is here where APOLAN excels, resulting in a worldwide reputation for superior quality and consistency.

THE PROOF IS IN PRINTING RESULTS USING MULTIPLE SAMPLES TO CONFIRM CONSISTENCY.



APPLICATION DATA

SOLVENT RESISTANCE
Durometer ShA
Color
Latex-Ink (Water)
PVC-Ink Cyclohexanon
UV-Ink Vinypyrolydone
50-55
clear
excellent
55-60
clear
excellent
60-65
orange
excellent
fair
fair
65-70
light orange
excellent
fair
fair
70-75
blue
excellent
good
good
75-80
grey
excellent
very good
very good
80-85
red
excellent
excellent
excellent
85-90
light red
excellent
excellent
excellent
90-95
dark orange
excellent
excellent
excellent

 

  1. When comparing solvent resistance of different Polyurethanes it is important to know that solvent swelling alone is not necessarily indicative for retained mechanical properties after long term exposure to solvents.

  2. The higher the Durometer, the better the solvent resistance.

  3. Certain Polyurethanes have a higher modulus (apparent stiffness) for a given Durometer. In this case use APOLAN at the next higher ShA interval.

  4. APOLAN squeegees, both, with molded edge and with cut edge, are always molded on both sides.
    It has been proven that molded sidewalls resist solvent attack better than open cast sidewalls

 

APOLAN screen printing squeegees are made from the toughest polyurethane formulation; very abrasion resistant and solvent resistant. Listed below are some tips to help to provide longest possible performance life.  

Before allowing the squeegee to rest, clean squeegee thoroughly with a solvent to remove any ink residue (Never   soak a squeegee in a solvent for an extended period to clean it, as this may cause irreversible damage to your   squeegee. This applies to any squeegee material.)

Depending on the durometer of the squeegee and the aggressiveness of the inks and solvents, the squeegee may   require a minimum of 12 to 48 hours of rest before re-use or re-sharpening, (As a rule, softer durometer squeegee   material tends to absorb more ink and solvents than harder durometers do, which in turn require longer recovery   periods.

Sharpening:
Before any sharpening is to take place, the squeegee material may require 12-48 hours to allow any solvents to   evaporate. This depends on the aggressiveness of the inks and solvents used.

Belt or grinding wheel sharpening is acceptable for most applications and is best done in a two step process.

  1. Coarse grit (60-120) to remove worn edge
  2. Fine grit (160-30) to create a sharp edge and a smooth polished finish

Following these helpful hints will result in extending the printing life of our already long lasting APOLAN squeegee.

Storage:
See attached instructions.

Maintenance:
To maintain uniform print quality, a rotation schedule should be established to allow a squeegee to "rest". (The proper rotation schedule will depend on the aggressiveness of your particular ink system.)

  1. Under the most aggressive inks and solvents, a squeegee should be used for approximately two to four hours of continuous printing and then inspected for any signs of swelling.
  2. Using moderate to weak inks and solvents, approx. after six to eight hours of printing the squeegee should be inspected for any sign of swelling before allowing to rest.
  3. Change squeegee at the first sign of swelling. Naturally, with more aggressive inks, swelling will be more apparent.

 



APOLAN - Screen Printing Squeegees Recommended Storage

STORAGE:

ENVIRONMENT:

Best:

Store flat.
a) Edge up - Cover top to protect from airborne contamination.

b) On side - Clean surface.
-Clean squeegee if stacked (particles will cause permanent deformation).

Acceptable:

Store coiled - O.K. if reverse coiled for 24 days prior to use.

  1. Ideal: 50'-80'F @ 30-70% humidity
    (up to 5 years)

  2. Acceptable: Up to 100'F below 50% humidity
    (up to 1 year)

  3. Avoid temperatures over 85'F together with humidity over 70%. This will shorten shelf-life
    (i.e. tropical climate (in non-air conditioned warehouse).