3ADHESIVE: A Substance Capable of Holding Materials Together by Surface Attachment MULTI BILLION $ BUSINESS>750 COMPETING INDUSTRIESBoron Compounds – Little UsageSignificant Role
4Be B C Agriculture to Aerospace ‘Mummies to Cancer Therapy’ SMALL PRESENCE – BIG MAGICAL CHANGES IN MATERIALPROPERTYAgriculture to Aerospace‘Mummies to Cancer Therapy’
5First Known Adhesive: 4000BC Adhesives and Boron – Is the Connection Historic?First Known Adhesive: 4000BCPre-Historic Artefacts Glued with Tree Saps/ResinsIn Babylonian Temples: Glued Ivory Eyeballs1-500AD: Greeks/Romans: Veneering & MarquetryDeveloped Animal Glue: Fish/Blood/Bones/HideAD: Term ‘Adhesive’ as Specific Substance1700AD+: Industrial Revolution: Rapid Growth1900AD+: Synthetic Resins
6A Boron Based Mineral for Preservation; Bonding; Lamination BORON’S CONNECTION?Art of Making Mummies Involved : NATRONA Boron Based Mineral for Preservation;Bonding; Lamination
7Regardless of the Type : Plant, Starch, or Animal Based A Common Substance in Glue Recipe:Borax or Some form of BoratesAs Preservatives or Adhesive Enhancer?
8Chemistry Behind Its Marvel: B : 1s22p1 : sp2 Hyb : Trigonal Planar LEWIS ACIDChattopadhyay, Arun K.; J. Adhesion Sci and Technol (in press, 2014)
9Trigonal Planar sp2 ↔ sp3 Tetrahedral H3BO3 + H2OStereo Chemically They Can Be Both Tetrahedral and Trigonal PlanarB4O72-(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)
10Tetrahedral 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)
11The Prime Importance for Adhesion to A Substrate: Wetting or Surface ForceFor which the molecular structure of an adhesive especially:1. Chain length2. Presence of any branched chains3. Presence of polar groups4. Viscosityare the most important aspects to consider for the performance of an adhesive.
12Chattopadhyay, Arun K.; J. Adhesion Sci and Technol (in press, 2014)
13In Water Borne Adhesive Formulations: 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
14STARCH 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.
15ADVANTAGES OF BORATED ADHESIVES: Gives required viscosity and structure2. Increases tack.3. Improves film formation of the starchbased glue onto the papers.4. Improves water holding of the glue5. Minimizes water penetration (paper)6. Improves high temperature stability
16ANIMAL GLUE: One of the Oldest Arts Known Method: Extraction of Water Miscible ProteinsBy Boiling Blood,Bones, Hoofs, Horns, Hides –Extracted Protein Undergo HydrolyticDegradation Forming Collagen and thenGelatin – A Denatured Collagen Type-1Collagen Type-1 Glycoprptein
17Boric Acid and Borax In Animal Glues: Modify Rheology Provide High Temperature ToleranceImprove Water ResistanceResist Fungal, Bacterial and Insect AttacksAPPLICATIONS: Wood & Furniture IndustriesOften Formulated With CaseinT. 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).
18Neutral 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
19RUBBER BASED CONTACT ADHESIVES Pressure Sensitive Adhesive TapesFloor Tiles and CarpetsContact Adhesives for Plastic LaminatesSelf Sealing EnvelopsRubber CementsLEATHER INDUSTRIES
20Due to Increasing Stringency Towards Solvents: Water Borne Rubber Adhesives Are on the RiseUse of Boric Acid Improves:Set TimeStorage StabilityTensile StrengthHigh Elongation Characteristics
21Chattopadhyay, Arun K.; J. Adhesion Sci and Technol (in press, 2014)
22SYNTHTIC ADHESIVES:NON REACTIVE (Solvent and Water Based)REACTIVEDirect & Indirect Use of Boron Compounds
23Solvent based adhesives that get cured as the solvent evaporates. e.g. white glue, contact adhesives, rubbercement etc.Polymer dispersion types, like polyvinyl acetates(PVAc)Extensively Used In Wood & Packaging Industries.In water borne PVAc adhesive systems: EsterGroups of PVAc Hydrolyzes Forming HydroxyComponents of the polymer.Using Borax or Boric Acid Under an AlkalineCondition Causes the Polymer to Crosslink.
24Chattopadhyay, Arun K.; J. Adhesion Sci and Technol (in press, 2014)
25REACTIVE ADHESIVES:Reactive adhesives mainly include Urethanes, Epoxies, and Cyanoacrylates.Urethanes: A Small Addition BoraxReduces Formaldehyde Emission.
26EPOXIES: BF3 is Used as a Catalyst for Homo-Polymerization ofEpoxy Resins for High TempCuring.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 ParticularlyDesirable for Aerospace & Defense and formicroelectronic assemblies
27HOT MELT ADHESIVES: THERMOPLASTIC SOLID POLYMER Liquefy AtElevated TemperatureThe Major Use: Carton SealingFrozen Food Packages,Breakfast Cereal, Laundry Detergent,Beer Cartons, etc.Tri-Phenyl & Tri-Fluoro Boranes are Used forSynthesis of Co-Polymerized Ar.Vinyl-co-Sty.ButadieneSilicones Based Reactive Systems: Boron Halides areUsed for Curing
28In Cyanoacrylates (Super Glue): Boron Oxide and Boron Tri Fluoride ComplexesAre Used as Acid Inhibitor & Stabilizer for theSynthesis of Cyanoacrylates.
29Silicone Adhesives: Boron oxide and boric acid are used as fillers in Organometallic derivatives of boronic acids are used asphoto-initiators in UV curable compositions.Boron nitride is used in thermally conductive silicone adhesives.Self-adhering silicon rubbers of improved surface properties aresynthesized using boric acid (<0.5 wt%) for the manufacture ofpressure sensitive adhesive elastomers.It is well known that addition of boric acid to siliconesimproves adhesion to metalHot melt adhesive composition containing α-olefin/aromatic vinyl compound random copolymer; US Patent US B1.Adhesive Compositions for Medical Use: Single Additive as Both the Thickening Agent and the Accelerator; USPTO Patent Application US 2012/ A1.Viscous alpha-Cyanoacrylate Compositions; Patent Application US 2009/ A1.Acid chelate of boric acid or a derivative thereof with a poly-hydroxy compound; US Patent US A.Ashton Acton (Ed), in ‘Boron Compounds - Advances in Research and Application’, Scholarly Edition (2013).
30e.g.: Boron Compounds are Replaced by Chlorine Questionable Health Concerns with Boron CompoundsOpened New Vistas to Search for Substitutes to Replace Boron.In many Cases Such Attempts are Found to be No LessDamaging to Environment and Health, and Often They Are Costlier.e.g.: Boron Compounds are Replaced by Chlorineand Enzymes in DetergentsLi Compounds Are Used to Replace Borates inEnamels & Glass ProductsAmm.Sulphate/Magnesium Sulphate Used As Alternate to Borate For Fire Retardation
31THE FUTURE OF BORON IS ONLY LIMITED DESPITE ALL UNPLEASANT ATTEMPTS TO DISPLACEBORON COMPOUNDS, WHICH HAVE BEEN IN USEFOR CENTURIES, CAN EASILY OUTLAST SUCHCONCERNS AND MEET THE DEMAND FOR MANYCOMING YEARS.THE FUTURE OF BORON IS ONLY LIMITEDBY OUR IMAGINATION