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ARUN K. CHATTOPADHYAY Etimine USA, Inc., Pittsburgh, PA

BORON IN ADHESIVES. ARUN K. CHATTOPADHYAY Etimine USA, Inc., Pittsburgh, PA. ADHESIVES. Surfaces & Interfaces Solid/air; Solid/Solid; Solid/ L iquid ; Air/Liquid & Liquid/Liquid. ADHESIVE: A Substance Capable of Holding M aterials T ogether by Surface A ttachment

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ARUN K. CHATTOPADHYAY Etimine USA, Inc., Pittsburgh, PA

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  1. BORON IN ADHESIVES ARUN K. CHATTOPADHYAYEtimine USA, Inc., Pittsburgh, PA

  2. ADHESIVES Surfaces & InterfacesSolid/air; Solid/Solid; Solid/Liquid; Air/Liquid & Liquid/Liquid

  3. ADHESIVE: A Substance Capable of Holding Materials Together by Surface Attachment MULTI BILLION $ BUSINESS >750 COMPETING INDUSTRIES Boron Compounds – Little Usage Significant Role

  4. Be B C SMALL PRESENCE – BIG MAGICAL CHANGES IN MATERIAL PROPERTY Agriculture to Aerospace ‘Mummies to Cancer Therapy’

  5. Adhesives and Boron – Is the Connection Historic? First Known Adhesive: 4000BC Pre-Historic Artefacts Glued with Tree Saps/Resins In Babylonian Temples: Glued Ivory Eyeballs 1-500AD: Greeks/Romans: Veneering & Marquetry Developed Animal Glue: Fish/Blood/Bones/Hide 1500-1700AD: Term ‘Adhesive’ as Specific Substance 1700AD+: Industrial Revolution: Rapid Growth 1900AD+: Synthetic Resins

  6. BORON’S CONNECTION? Art of Making Mummies Involved : NATRON A Boron Based Mineral for Preservation; Bonding; Lamination

  7. Regardless of the Type : Plant, Starch, or Animal Based A Common Substance in Glue Recipe: Borax or Some form of Borates As Preservatives or Adhesive Enhancer?

  8. Chemistry Behind Its Marvel: B : 1s22p1 : sp2Hyb : Trigonal Planar LEWIS ACID Chattopadhyay, Arun K.; J. Adhesion Sci and Technol (in press, 2014)

  9. Trigonal Planar sp2 ↔ sp3 Tetrahedral H3BO3 + H2O Stereo Chemically They Can Be Both Tetrahedral and Trigonal Planar B4O72-(aq) + H2O(l) ↔ HB4O7-(aq) + OH-(aq) B4O72-(aq) + 5H2O(l) + 2H+(aq) ↔ 4H3BO3 (aq) B(OH)3 (aq) + H2O(l) ↔ B(OH)4-(aq) + H+(aq)

  10. Tetrahedral B(OH)4- Undergoes Bridging and Gels With Polyol, Cellulose, Polysaccharide, Glycoprotein etc. This is the basis for its importance in adhesives. Chattopadhyay, Arun K.; J. Adhesion Sci and Technol (in press, 2014)

  11. The Prime Importance for Adhesion to A Substrate: Wetting or Surface Force For which the molecular structure of an adhesive especially: 1. Chain length 2. Presence of any branched chains 3. Presence of polar groups 4. Viscosity are the most important aspects to consider for the performance of an adhesive.

  12. Chattopadhyay, Arun K.; J. Adhesion Sci and Technol (in press, 2014)

  13. ROLE OF BORATES/BORIC ACID? In Water Borne Adhesive Formulations: Increases molecular weight of starch or poly saccharides, casein, glycoproteins, and poly-ol type of molecules after forming complexes. Modifies Viscosity to a desired extent

  14. STARCH BASED ADHESIVES APPLICATIONS: Paper Bonding and paper products: Bookbinding, Corrugated Boxes, Paper Bags, Wallpaper pastes etc. Typical Formulation: Cooking Starch-Dextrin (35%) with Water (~58%), Borax (6%), Defoamer, Alkali, preservatives etc.

  15. ADVANTAGES OF BORATED ADHESIVES: • Gives required viscosity and structure • 2. Increases tack. • 3. Improves film formation of the starch • based glue onto the papers. • 4. Improves water holding of the glue • 5. Minimizes water penetration (paper) • 6. Improves high temperature stability

  16. ANIMAL GLUE: One of the Oldest Arts Known Method: Extraction of Water Miscible Proteins By Boiling Blood,Bones, Hoofs, Horns, Hides – Extracted Protein Undergo Hydrolytic Degradation Forming Collagen and then Gelatin – A Denatured Collagen Type-1 Collagen Type-1 Glycoprptein

  17. Boric Acid and Borax In Animal Glues: Modify Rheology Provide High Temperature Tolerance Improve Water Resistance Resist Fungal, Bacterial and Insect Attacks APPLICATIONS: Wood & Furniture Industries Often Formulated With Casein • T. E. Rolando, Rapra Review Report, vol 9 (5), 1-20 (1995). • L. A. Varghese and E. T. Thachil, J. Adhesion Sci. Technol., 18, 181 and 1217 (2004).

  18. Neutral Plastic Adhesive: HCl, tar, Congo gum, and urea, and cooking with an animal glue, casein, borax, sodium benzoate, oil of Wintergreen and water. Addition of casein provides improved plasticity to the adhesive by bridging with glycoprotein via B(OH)4- ion forming a massive H-bond network

  19. RUBBER BASED CONTACT ADHESIVES Pressure Sensitive Adhesive Tapes Floor Tiles and Carpets Contact Adhesives for Plastic Laminates Self Sealing Envelops Rubber Cements LEATHER INDUSTRIES

  20. Due to Increasing Stringency Towards Solvents: Water Borne Rubber Adhesives Are on the Rise Use of Boric Acid Improves: Set Time Storage Stability Tensile Strength High Elongation Characteristics

  21. Chattopadhyay, Arun K.; J. Adhesion Sci and Technol (in press, 2014)

  22. SYNTHTIC ADHESIVES: NON REACTIVE (Solvent and Water Based) REACTIVE Direct & Indirect Use of Boron Compounds

  23. Solvent based adhesives that get cured as the solvent evaporates. e.g. white glue, contact adhesives, rubber cement etc. Polymer dispersion types, like polyvinyl acetates (PVAc) Extensively Used In Wood & Packaging Industries. In water borne PVAc adhesive systems: Ester Groups of PVAcHydrolyzes Forming Hydroxy Components of the polymer. Using Borax or Boric Acid Under an Alkaline Condition Causes the Polymer to Crosslink.

  24. Chattopadhyay, Arun K.; J. Adhesion Sci and Technol (in press, 2014)

  25. REACTIVE ADHESIVES: Reactive adhesives mainly include Urethanes, Epoxies, and Cyanoacrylates. Urethanes: A Small Addition Borax Reduces Formaldehyde Emission.

  26. EPOXIES: BF3 is Used as a Catalyst for Homo-Polymerization of Epoxy Resins for High Temp Curing. Epoxy Adhesives of High Thermal Conductivity: BN Used as Filler For High Performance Bonding, Sealing, Coating and Potting. BN Based Epoxies Are Lighter in density Particularly Desirable for Aerospace & Defense and for microelectronic assemblies

  27. HOT MELT ADHESIVES: THERMOPLASTIC SOLID POLYMER Liquefy At Elevated Temperature The Major Use: Carton Sealing Frozen Food Packages, Breakfast Cereal, Laundry Detergent, Beer Cartons, etc. Tri-Phenyl & Tri-FluoroBoranes are Used for Synthesis of Co-Polymerized Ar.Vinyl-co-Sty.Butadiene Silicones Based Reactive Systems: Boron Halides are Used for Curing

  28. In Cyanoacrylates (Super Glue): Boron Oxide and Boron Tri Fluoride Complexes Are Used as Acid Inhibitor & Stabilizer for the Synthesis of Cyanoacrylates.

  29. Silicone Adhesives: Boron oxide and boric acid are used as fillers in silicone adhesives. Organometallic derivatives of boronic acids are used as photo-initiators in UV curable compositions. Boron nitride is used in thermally conductive silicone adhesives. Self-adhering silicon rubbers of improved surface properties are synthesized using boric acid (<0.5 wt%) for the manufacture of pressure sensitive adhesive elastomers. It is well known that addition of boric acid to silicones improves adhesion to metal • Hot melt adhesive composition containing α-olefin/aromatic vinyl compound random copolymer; US Patent US 6235818 B1. • Adhesive Compositions for Medical Use: Single Additive as Both the Thickening Agent and the Accelerator; USPTO Patent Application US 2012/0264846 A1. • Viscous alpha-Cyanoacrylate Compositions; Patent Application US 2009/0326095 A1. • Acid chelate of boric acid or a derivative thereof with a poly-hydroxy compound; US Patent US4182823 A. • Ashton Acton (Ed), in ‘Boron Compounds - Advances in Research and Application’, Scholarly Edition (2013).

  30. Questionable Health Concerns with Boron Compounds Opened New Vistas to Search for Substitutes to Replace Boron. In many Cases Such Attempts are Found to be No Less Damaging to Environment and Health, and Often They Are Costlier. e.g.: Boron Compounds are Replaced by Chlorine and Enzymes in Detergents Li Compounds Are Used to Replace Borates in Enamels & Glass Products Amm.Sulphate/Magnesium Sulphate Used As Alternate to Borate For Fire Retardation

  31. DESPITE ALL UNPLEASANT ATTEMPTS TO DISPLACE BORON COMPOUNDS, WHICH HAVE BEEN IN USE FOR CENTURIES, CAN EASILY OUTLAST SUCH CONCERNS AND MEET THE DEMAND FOR MANY COMING YEARS. THE FUTURE OF BORON IS ONLY LIMITED BY OUR IMAGINATION

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