EFFECTIVE PRIMER FOR THE CYANOACRYLATE ADHESIVES

The cyanoacrylate (CA) adhesives (typical one -"SuperGlue®") are widely usedin the industry when it is necessary to bond two closely fitting surfaces. When pressedinto a thin layer, they form a rigid thermoplastic film with excellent adhesion to manysubstrates. However, the currently available CA adhesives have some disadvantages thatsignificantly lower their application area. These disadvantages are:

• Weak bond to various plastics, such as polypropylene, polyethylene, polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (Teflon®;) that necessitates the need for primers. The currently available on the market primers allow rather strong bonds to polypropylene, but the adhesion to the other polyolefins is insufficient for the industrial purposes.
• Relatively weak initial bond. The cyanoacrylate adhesives with commercial primers reach 30% of their full strength after 15 min., and full strength only after 24 hours.
• Inability to bond materials at low temperatures. The cyanoacrylate adhesives with commercial primers cannot be effectively used at the temperatures below 40°F.
• Instability of the bond in warm water.

The currently available  commercially primers allow CA adhesives to bondpolypropylene and polyethylene, but the bonding strength is insufficiant for manyapplications.

The developed by POLYMERight, Inc. primer allows CA adhesives to bond polypropylene andpolyethylene with a much higher bonding strength. It also makes it possible to glue suchtraditionally impossible to bond plastics as polyvinylidene fluoride (PVDF) andpolytetrafluoroethylene (Teflon®;).

Lap shear bonding strength for polypropylene typically exceeds 2,000 psi (more, thanthe strength of the material itself), for the high density polyethylene (HDPE) it exceeds1000 psi, for PVDF and Teflon®; it exceeds 500 psi.

The POLYMERight's primer acts also as an accelerator and provides a quicker curing ofcyanoacrylates: its use allows bonds to reach 30% of their full strength after 10-15seconds and achieve full bonding strength after 10-15 min.

The other proven advantages of our system, in comparison with the best primers that arecurrently commercially available, are

• generally improved (by 30-100%) bonding strength,
• much more stable and consistent results,
• very significantly (by 300%) improved bonding strength at below freezing temperatures, and
• increased stability of open-to-air primed surface.

The further development of this product could lead to the production of the"primerless" cyanoacrylate adhesives that do not need any primers to bondpolypropylene, polyethylene, polyvinylidene fluoride, polytetrafluoroethylene and otherplastics.

COMPARATIVE RESULTS OF TESTING OF VARIOUS PRIMERS FOR CA ADHESIVES

Comparison of Bonding Strength to Polypropylene inDifferent Conditions

Same brand of adhesive was used for all tests

Material	Test Conditions	Leading USA Brand Primer	Leading European Brand Primer	POLYMERight's Primer
Polypropylene, unfilled	Specimen were bonded and placed under pressure for 15 minutes.	700 psi	400 psi	1700 psi
Polypropylene, filled		900 psi	400 psi	1700 psi
Polypropylene, unfilled	Specimen were bonded and placed for 15 minutes in a -5°C	200 psi	N/A	800 psi
Polypropylene, filled		250 psi	N/A	1200 psi
Polypropylene, unfilled	Tested 1 minute after bonding	350 psi	280 psi	550 psi
Polypropylene, unfilled	1 hr. between priming & bonding	400 psi	320 psi	700 psi
Polypropylene, unfilled	24 hrs. between priming & bonding	300 psi	250 psi	500 psi
Polypropylene, unfilled	24 hrs. in 80°C water after bonding	400 psi	250 psi	1000 psi

Comparison of Bonding Strength of Different CA Adhesives toPolypropylene with Different Primers

All specimen were bonded and placed under pressure for 15 minutes.

Material	Adhesive	Leading USA Brand primer	POLYMERight's primer	POLYMERight's Advantage
Polypropylene, unfilled	Loctite 401 Prism®	700 psi	1700 psi	143%
Polypropylene, unfilled	Loctite 496 Prism®	150 psi	400 psi	167%
Polypropylene, unfilled	Henkel Sicomet® 8300	400 psi	700 psi	75%
Polypropylene, unfilled	QuickFix® Super Glue	500 psi	700 psi	40%

 

Comparison of Bonding Strength to Different Plastics
All specimen were bonded and placed under pressure for 15 minutes.

Material	Leading USA Brand Primer	POLYMERight's Primer	POLYMERight's Advantage
Polypropylene, unfilled	700 psi	1700 psi	143%
Polypropylene, filled	900 psi	1700 psi	89%
High Density Polyethylene (HDPE)	300 psi	700 psi	133%
Cross-Linked Polyethylene (CLPE)	30 psi	600 psi	1900%
Polytetrafluoroethylene (Teflon®)	15 psi	350 psi	2233%
Polyvinylidene Fluoride (PVDF)	15 psi	450 psi	2900%

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