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Characteristics of Structural Adhesives

structural characteristics of an adhesive, structural adhesive (structural adhesive): This is a high strength for the adhesive pvc material (such as wood, composite materials or metal) adhesives, room temperature, the actual bond strength is greater than 6.9MPa ( 1000psi). Another definition: This is an effective design load does not occur under the deformation (or creep) material. As the performance requirements, structural adhesives are usually can be cross-linked (thermosetting's) organic compounds, often with a polarity, with a high surface energy, able to resist various types of external damage, a number of years in the harsh environment experienced or even decades; 2, membrane adhesive-film adhesive paste adhesive-paste adhesive 3, structural adhesive matrix resin chemical properties: 1). phenolic resin: a. alkali as the catalyst, phenol and excess formaldehyde reaction of A-order phenolic resin (resole phenolic resin); acid as catalyst and excess phenol formaldehyde reaction of phenol novolac resin (novolac phenolic resin) hexamethylene tetramine (Hexa methenamine) can be cured; b. phenol and formaldehyde to 2:1 ratio of pouch amount of material for reaction, pouch resulting product is known as bisphenol-F (2 phenol formaldehyde), when the phenol and acetone with the same amount of material than a reaction, will be given bisphenol A (2 phenol acetone); 2). protein: a protein for structural adhesives are the main source of animal blood, fish, milk, connective tissue and soybeans. Throughout history, adhesive proteins has been used by humans in the modern is mainly used for plywood production, but it can not withstand harsh environments, so she obtained only limited to indoor use of plywood; 3). Epoxy resin: The oxirane ring as part of its response element known as epoxy resins, and many more polyphenols and the reaction of propylene oxide-based; a.2, 2 - isopropylidene two phenol (also known as bisphenol A: BPA ) with epichlorohydrin reaction of available epoxy bisphenol A, 2 C ether (DGEBPA); it can be a further reaction with the bisphenol A a higher molecular weight resins, the epoxy-end-or phenyl; 2 phenol formaldehyde (also known as bisphenol F: BPF) to react with epichlorohydrin resin and DGEBPA similar resin; there are two categories of epoxy resin were epoxidized phenolic resin and cyclic aliphatic epoxy resin (alicyclic ?) b. epoxy curing methods are alcohol or mercaptan, anhydride, cationic polymerization (Lewis acid),yoga mat, anionic polymerization (imidazole), amines (dicyandiamide) c. Thermoset system for its curing temperature, curing time and the thermosetting resin The relationship between the physical state of a very complex and often confusing. See time-temperature shift (TTT) spectra; 4) urethane resin: Although the polyurethane inner strength or modulus is not prominent, but its got tough cured resin to absorb the energy potential is very large, either preparation of polyurethane adhesive at room temperature, can also be formulated into a high-temperature curing adhesives. Urethane-based adhesive formulations depends on the isocyanate, polyol and chain extender agent is called a (short-chain amine or alcohol) material choice. 5) Acrylic resin: broadly divided into two categories: free radical-curable adhesives, and cyanoacrylate adhesive (anaerobic, or UV-curing) 6) High Temperature Structural Adhesives: a. characterization of high temperature resistant adhesive material is a key feature is their high degree of aropvc maticity (to generate anti-oxidation) and the aggregate surplus in the course of chemical bonds. b. Polyimide (nadik functional groups, between the amino-p-phenylene vinylene), bismaleimide (Michael addition reaction) 4, structural adhesive properties of optimal design: 1) phenolic resin: acrylic - phenolic resin film adhesive ( nitrile - butadiene elastomer); 2) Epoxy resin: plastics processing and the use of additional phase separation of toughening (toughening toughening agent) (nitrile rubber), melamine curing agent may be used as an aid to reduce dicyandiamide required high curing temperature. Goland-Reissner effect; 3) acrylic resin: use of relatively high molecular weight acrylic ester - methyl acrylate copolymer, fumed silica ... 4) high-temperature structural adhesives: (Subrahmanian) a. In these polymers in There should only be the strongest chemical bond, preferably containing aropvc matic ring, but should be avoided such as alkyl and alkyl sub-unit; b. The structure at the lowest energy state, the heat does not occur rearrangement; c. to maximize resonance with stability (a high degree of aromaticity) structure; d. the structure of the chemical bond in the most stable configuration, when its heat after fracture, can be easily re-formation; e. the main chain with multiple keys attached ladder polymers should be many as possible, so a single bond rupture will not result in weight loss; f. the polymer at the lowest possible temperature should have the machinability; g. The polymer should have a low enough yield stress, itself so that it can absorb the fracture energy or toughness. Finally two contradictory points in front, to balance these requirements technology has been in the study. ---

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