Instand Adhesives

Three Bond Technical News Issued March 20, 1988 21 Instant Adhesives (Cyanoacrylate Adhesives) Introduction Instant adhesives (cyanoacrylate adhesives ) are one-part solvent-free adhesives that cure immediately at room temperature and offer strong bonding strength. Instant adhesive was first developed in 1949 by Alan E. Ardis at Goodrich Company in the U.S., and was later developed into a product by F. B. Joyner and G. F. Hawkins at Eastman Company and marketed as Eastman 910 in 1959. Since then, various adhesive manufacturers around the world have improved and modified methods of synthesizing the main components, monomer. Due to the unique characteristics that distinguish these adhesives from other types, instant adhesives are currently used in a wide range of applications, both in industry and in the home. This issue will describe the reaction mechanism of these unique instant adhesives and the advantages and disadvantages stemming from their properties. This issue will also introduce the ThreeBond 1700 series and discuss the present and future of instant adhesives. Contents Introduction................................................................. 1 1. The reaction mechanism of instant adhesives ...... 2 2. Instant adhesives-ThreeBond 1700 (TB 1700) series ..................................................................... 2 2-1. Classification of the TB 1700 series ............. 2 2-2. Characteristics of the TB 1700 series........... 3 3. Advantages and disadvantages of instant adhesives .............................................................. 3 4. Examples of main applications of instant adhesives .............................................................. 4 5. ThreeBond 1797-an adhesive primer for hard-to-bond materials (for instant adhesives)...... 5 5-1. Outline...........................................................5 5-2. Characteristics ..............................................5 5-3. Properties......................................................5 5-4. Performance..................................................5 6. ThreeBond 1739 (gel-type instant adhesives) .......7 6-1. Outline...........................................................7 6-2. Properties and basic performance ................7 6-3. Performance..................................................8 Conclusions.................................................................9 1 1. The reaction mechanism of instant adhesives chemical groups that have negative ions (anions) are water (H-OH), methanol (CH3OH), and caustic soda (NaOH). The OH-group within the molecular structures of these groups acts upon the cyanoacrylate, and, through the chemical reactions illustrated below, induces polymerization and curing. The chemical reaction that causes curing of instant adhesives is referred to as anion polymerization. In other words, a substance containing anions causes a reaction to progress rapidly, with polymerization and curing taking place within seconds. Representative examples of R: Methyl group (-CH3), ethyl group (-C2H5), alkyl groups, etc. 2. Instant adhesives-ThreeBond 1700 (TB 1700) series 2-1. Classification of TB 1700 series Types Purpose TB Grade Viscosity (cP) Remarks 1701 1702 1703 Heat-resistant type Impact-resistant type ThreeBond 1700 series Woodwork type Low-odor low blooming type Methyl cyanoacrylate For bonding metals, rubber, and plastics 1741 1743 2 100 1745 1747 Multi-purpose type 3 35 100 500 2,000 Ethyl cyanoacrylate For bonding metals, rubber, and plastics 1713 1751 1753 1781 1782 1783 1785B 1786 1787 1721 100 3 80 3 80 1,000 3 150 1,100 10 High heat-resistant type High peeling strength, impact-resistant type For bonding porous substrate materials such as wood and balsa Low-odor, low-blooming type Gel form In gel form to permit use on ceilings and vertical surfaces Gel type 1739 Peeler 1795 1 Curing accelerators 1796 1 1797 1 Adhesive primers for hard-to-bond surfaces Slow-curing type For cleaning blooming and excess adhesive For curing thick coats of adhesives such as in hardfacing Allows bonding of PE and PP when used together with instant adhesives * In addition to the standard products listed above, specialized products are available in a variety of different viscosities, colors, etc. 2 2-2. Characteristics of the TB 1700 series The TB 1700 series has the following characteristics. (1) Instant bonding - a strong bond is formed within five seconds to three minutes. (2) Easy-to-use - Since it is a one-part formulation, there is no need to mix with a curing agent. Neither pressurization nor heating is required. (3) Strong bonds are formed at room temperature. (4) Extremely small amounts are required-due to its 3. low viscosity, it spreads well and extends into corners, reducing required application amounts by half relative to other adhesives. (5) The bonded part is clear and colorless, resulting in a neat finish. (6) Since it is solvent-free, virtually no shrinkage occurs during curing. (7) Promotes rationalization and efficiency in work procedures Advantages and disadvantages of instant adhesives Instant adhesive products that are popularly used today are either methyl cyanoacrylates or ethyl cyanoacrylates; 90% of them are the latter. Advantages and disadvantages common to these two representative instant adhesives are given below. Advantages Disadvantages 1) Instant bonding 1) Low heat resistance 2) Curing at room temperature 2) Low impact resistance 3) One-part catalyst-free formulation 3) Low elasticity 4) High bonding strength 4) Only applicable in small-clearance applications 5) High electric insulation capacity 5) Unsuitable for bonding large surfaces at once 6) High chemical resistance 6) Irritating odor and causes blooming 7) Requires small volumes 7) Bonds well with skin, so care is required in handling 8) Requires caution in storage and management ThreeBond 1739 Instant extra-strength adhesive (gel-type) 3 4. Examples of main applications of instant adhesives Below are examples of applications in various fields of industry. Fields Parts Substrate materials Tape recorder buttons Buttons on Irons Duracon + Aluminum Buttons on CD/DVD players Zinc + Brass Rod antenna accessories ABS + Chromium plating Capstans Brass + Stainless steel Magnetic heads Permalloy + Iron Fuse casings Polyester + Polycarbonate Calculators Urethane rubber + Polyacetal Gaskets in CRTs Electrical instruments ABS + Chromated metal parts Neoprene + Neoprene Gaskets in vacuum cleaners Neoprene + ABS Rubber vibration isolators in washing machines Neoprene + SBR Spark-plug lead covers Neoprene + Soft PVC Dashboard leather Urethane foam + Soft PVC Door edge guards Soft PVC + Soft PVC Door handle parts Neoprene + Phenol Rubber on window frames EPT + EPT Cushion absorbers Neoprene + Unichrome plating Washer nozzles Automobiles Neoprene + Unichrome plating Distributor gaskets Neoprene + ABS Mud flaps Neoprene + Chromium plating Camera viewfinders Glass + Iron Printer wiring Precision instruments Natural rubber + Natural rubber Tail lamp decorations ABS + Aluminum Camera shutters Stainless steel + Aluminum Camera tripods ABS + Aluminum Strain gauges ABS + Aluminum Guitar bridges Rosewood + Urethane-coated board Banjo drums ABS + Plywood Moving piano parts Maple + Maple Flutes ABS + Chrome plating Packing rubber in Hume pipes Synthetic rubber + Synthetic rubber Blood pressure meters Neoprene + Neoprene Frangible disks in fire extinguishers Polyester + Synthetic rubber Carrier wheels Neoprene + Zinc Rubber mat fasteners Synthetic rubber + Nylon Syringe needles Others ABS + SPC copper Pianica keyboards Musical instruments Polyimide+ Iron Sewing machine parts Stainless steel + PVC Felt-tipped pens 4 Polyacetal + Gold plating Dolls Soft PVC + Soft PVC 5. ThreeBond 1797 - an adhesive primer for hard-to-bond materials (for instant adhesives) hazardous procedures. ThreeBond 1797 is an adhesive primer that enhances bonding performance at room temperature, and was developed in order to eliminate the workload for such pre-treatment processes. Even in today's fast-developing world of chemistry, no adhesive has yet been developed for securely bonding polyethylene, polypropylene, and fluoroplastic materials. One method for bonding these hard-to-bond materials is to activate the substrate surface temporarily by acid, thermal, or radiation treatment before applying the adhesive. However, all three methods are impractical as they pose health hazards, require a specialized facility, and involve complicated procedures. In this section, a simple pre-treatment method using a primer will be introduced for securely bonding hard-to-bond materials while avoiding the above-cited difficulties. 5-2. Characteristics 1. It displays high adhesive performance with polypropylene, polyethylene, and polyacetal materials. It is also significantly effective in bonding EPT rubber, polyurethane, and soft PVC materials. 2. Since it is quick-drying, bonding may be performed immediately after surface application. 3. It also acts as a curing accelerator, so that setting time is reduced. 4. It cures quickly at room temperatures and increases the speed and productivity of the assembling process. 5. It can be used with all instant adhesives of the TB 1700 series. 5-1. Outline ThreeBond 1797 is a specialized primer for securely bonding hard-to-bond materials-such as polypropylene, polyethylene, polyacetal, and EPT rubber - using instant adhesives in the TB 1700 series. The conventional method of bonding polypropylene, polyethylene, etc. involved pre-treatment by strong acid, strong alkalis, or heat, to give the adhesiveness. However, these treatments were considered impractical in application as they involved complicated, time-consuming, and 5-3. Properties Product name Items ThreeBond 1797 Color and appearance Lemon yellow liquid Viscosity (cP/25°C) 0.85 Specific gravity (25°C) 0.80 Main constituent Amine accelerator 5-4. Performance (a) Setting time (for bonding between the same materials and between different materials) Materials Materials Polypropylene Polyethylene Polyacetal Iron (seconds) Polypropylene Polyethylene Polyacetal Iron 5 - 5 5 - 5 5 5 - 10 10 10 15 (b) Shearing adhesive strength (for bonding between the same materials and between different materials) Materials Materials Polypropylene Polyethylene Polyacetal Iron Polypropylene 45.6* * Material fracture Polyethylene 39.0* 33.0 - Polyacetal 49.6* 36.5 47.1 - (kgf/cm2) Iron 28.1 21.5 31.2 130.5 25°C × 24-hour curing 5 (c) Curing time and shearing adhesive strength Time (h) Materials Polypropylene Polyethylene Polyacetal 1 2 25.1 11.1 28.1 (kgf/cm2) 4 30.4* 17.0 36.2 8 35.3* 20.0 40.2* 12 72 41.4* 33.0 45.2* 38.7* 27.2 41.5* 24 45.6* 32.5 47.1* 46.0* 33.0 46.2* 25°C curing * Material fracture Curing time and shearing adhesive strength Shearing adhesive strength Polyacetal Polypropylene Polyethylene Curing time (h) (d) Leaving time after application of TB 1797 and shearing adhesive strength Time (h) Materials Polypropylene Polyethylene Polyacetal Immediately after application 45.6* 21.5 47.1* (kgf/cm2) 0.5 1 5 24 48.4* 31.6 56.7* 49.4* 30.0 55.0 35.2* 21.0 34.7 21.3* 10.6 24.8 25°C × 24-hour curing * Material fracture Shearing adhesive strength Leaving time after application and shearing adhesive strength Polyacetal Polypropylene Polyethylene Immediately after application 6 Leaving time after application (h) (e) Amount of application and shearing adhesive strength Application method A Materials Polypropylene Polyethylene Polyacetal (kgf/cm2) B 24.1 16.4 61.0* C 27.3 19.8 58.2* D 37.3* 32.3 49.4* E 42.1* 39.4 45.2* 46.0* 42.1 14.2 25°C × 24-hour curing * Material fracture Application method A: A single stroke with cloth soaked in TB 1797 B: Two strokes with cloth soaked in TB 1797 C: Three strokes with cloth soaked in TB 1797 Increasing application amount D: Five strokes with cloth soaked in TB 1797 E: Dipped in TB 1797 (f) Heat resistance test and shearing adhesive strength Peeling test 2 Allowed to stand at 80°C, measured at room temperature (kgf/cm ) Time 1 4 8 12 24 Materials Polypropylene Polyethylene Polyacetal 42.1* 39.1 48.2* 41.3* 40.2 56.1* * Material fracture 47.6* 42.2* 55.3* 52.1* 42.1* 48.6* Materials 47.2* 41.3 48.0* Polypropylene Polyethylene Peeling adhesive strength (kgf/25mm width) 3.5* 1.4* * Material fracture 25°C × 24-hour curing (g) Handling instructions 1. Wipe contact surfaces clean using solvents or the like. 2. Keep a cloth or brush dipped in TB 1797 at hand; apply 1-2 strokes of TB 1797 on the surfaces. After drying, bond the surfaces using an instant adhesive of the TB 1700 series. 3. When bonding hard-to-bond surfaces such as polyethylene and polypropylene with easy-to-bond surfaces such as iron and copper, use the adhesive primer only on the hard-to-bond surface. 4. Be careful not to apply either excessive or insufficient amounts of TB 1797, as this will result in reduced bonding strength. 5. The TB 1797 coating on the contact surface will remain effective for one hour. 6. ThreeBond 1739 (Gel-type instant adhesives) 6-1. Outline Unlike conventional liquid instant adhesives, ThreeBond 1739 is a new, gel-type instant adhesive. Its performance is comparable to that of conventional liquid types, except that its thixotropic properties enables use on vertical surfaces and ceilings. Through combination with curing accelerators, it becomes possible to use TB 1739 as filler for pits. 6-2. Properties and basic performance Test items Color and appearance Clear and colorless liquid Viscosity 23,000 cP Thixotropic index 3.5 Specific gravity 1.03 Setting time NBR 35-40 seconds Setting time Fe/Fe 30-35 seconds Shearing adhesive strength Fe/Fe 180kgf/cm 2 7 6-3. Performance (a) Leaving time and adhesive strength (RT: shearing adhesive strength) Fe/Fe 1h 2h 4h 8h 16h 24h Strength 85 115 143 162 178 180 Shearing adhesive strength Leaving time Leaving time x adhesive strength Leaving time (b) Shearing adhesive strength and setting time for various materials Setting time (sec.) Shearing adhesive 2 strength (kgf/cm ) Fe/Fe 30 to 35 180 sus-sus 45 to 50 150 Al-Al 20 to 30 130 Cu-Cu 10 to 15 165 Glass-Glass 10 to 15 * Hard PVC-Hard PVC 20 to 25 80* Polycarbonate-Polycarbonate 20 to 25 70* Nylon-Nylon 20 to 25 65* Natural rubber-Natural rubber 30 to 35 * NBR-NBR 35 to 40 * EPT-EPT 35 to 40 * Materials * Material fracture 8 (c) Purposes (1) Fixing of components on printed circuit boards and lead wires (2) Adhesion and patching of parts for automobiles and machinery (3) Adhesion for wood and paper products (4) Adhesive in hobby crafts such as plastic models (5) Filling and adhesion by combining with curing accelerators Examples of application Wood Leather Cardboard Plywood For metals, hard plastics, and rubber due to its high bonding strength Hard plastic Metals Rubber Hard plastic For vertical surfaces, slits, and uneven surfaces due to its thixotropic properties Vertical surface Nail holes Slits Conclusions Instant adhesives are easy to use due to the instant bonding that results from the structure and reactivity of these substances. However, because of their low impact, heat, and water resistance, these adhesives are less suitable as bonding agents relative to epoxy or acrylic adhesives for structural (or semi-structural) components. It is believed that these disadvantages may be overcome by the addition of new chemical groups to the molecular structure of instant adhesives, or by combining instant adhesives with elastomers, and that an improved product will be available on the market in the near future. Furthermore, instant adhesives may enjoy wider application in the field of electronic and electrical fields once electrical conducting properties are added to the instant bonding properties of these adhesives. Also, the development of products with superior qualities such as low odor and low bleaching will improve a wide range of work environments, enabling the transformation of these adhesives into versatile and essential products. Atsushi Ohkuma Adhesive Department Research Laboratory Three Bond Co., Ltd. 9 Easy-to-use, waste-free, and stress-free adhesion Automatic Instant Adhesive Coater Even after selecting quality products to use in your work, you may not be able to make the most of these products if the conditions are not right. Superior products can make your job less labor-intensive, saving time and cost, with the proper handling conditions. Three Bond has thus developed easy-to-use, automatic applicators, which have met with high acclaim by our customers. Fan Flow N100 A tube is inserted into a container of adhesive; pressing a button on the pen-type dispenser causes the adhesive to be drawn out of the container and ejected through the tip of the pen. This mechanism requires no air source; only a source of electrical power. Since it adopts a tubing pump method, precise ejection volumes can be obtained continuously. ThreeBond Coater S An adhesive container is placed inside a container; pressing a button on the pen-type dispenser causes the adhesive to be expelled by air pressure and ejected from the tip of the pen. It is easy to make fine adjustments in ejection volume without error, preventing excessive application. It is suitable for manual applications in its current form and can be incorporated into production line systems with the addition of several adaptor parts. 1456 Hazama-cho, Hachioji-shi, Tokyo 193-8533, Japan Tel: 81-426-61-1333 10