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High Performance Adhesives and Sealants by UV Cure

Posted on 7/17/2018 9:05:04 AM By Deb Bhattacharjee
  

Significant progress has been made in industrial, medical, and electronic adhesive technologies to accommodate the need of rapidand strong bonding to glass, metal, plastic, and ceramic substrates.  This was accomplished by utilizing UV/visible light instead of conventional heat, leading to very fast cure and reduction in overall processing time (few seconds to minutes depending on the systems), while improving productivity through reduced labor/assembly costs and lower overall cost with simplified manufacturing footprint (e.g. elimination of ovens).

The chemistry could be the combination of free radical and cationic UV curing systems containing monomers, oligomers, photoinitiators and additives which undergoes rapid polymerization on exposure to the appropriatewavelength of UV light. Often these are formulated using epoxies, acrylates, and urethane chemistriesto cure on demand without any extra heat.  However, in order to expand the versatility of applications, dual cure systems (e.g. one component silicones in combination with moisture cure)were developed to enable very rapid bonding of substrates for the ease of assembly followed by secondary moisture cure allowing curing in shadowed areas. Improved storage stability/pot life at ambient condition would be a positive attribute. The performance advantages would include excellent thermal stability, reduced shrinkage, optical clarity, improved chemical and moisture resistance while maintaining or improving EHS protocols.

However, it is important to note that ultraviolet light can only be used when at least one of the substrates is transparent to light. The cure of opaque, filed or thick cross section is problematic using UV triggered systemand it is not the preferred option in all applications where conventional technology would be adequate.

References:

“UV curable adhesives based on acrylic polymers” https://patents.google.com/patent/WO2016177861A1

“UV-curable floor sealants” https://patents.google.com/patent/US8808863

“UV-curable optical resin adhesive composition” https://patents.google.com/patent/US8765833

“UV-Curing Adhesive, Preparation Process, Adhesively Bonded Semiconductor Component, and Method of Adhesive Bonding” https://patents.google.com/patent/US20080193751

“Solvent free process for making UV curable adhesives and sealants from epoxidized monohydroxylated diene polymers”
 https://patents.google.com/patent/EP0832163A1

Non-yellowing fast cure speed UV\visible curable liquid acrylic ester adhesives for glass bonding”, https://patents.google.com/patent/US6596787B1/en

Structural anaerobic adhesive compositions with improved cure speed and strength”,

https://patents.google.com/patent/US6596808B1/en

Liquified polyols, urethane acrylate resins prepared therewith and curable compositions employing such resins”, https://patents.google.com/patent/US6562881

“Acrylic-type pressure sensitive adhesives by means of ultraviolet radiation curing”,

https://patents.google.com/patent/US4181752A/en

Dual curing silicone compositions”, https://patents.google.com/patent/US6451870

“Adhesive composition, process, and product” https://patents.google.com/patent/US5234730A/en

“Curable adhesive compositions” https://patents.google.com/patent/US20040072933