6 Adhesives
By far, the largest amouts of adhesives are ud to manufacture building materials, such as plywood, structural flakeboard, particaleboards, fiberboard, structural framing and timbers, architectural doors, windows and frames, factory-laminated wood products and glass fiber insulation.
Adhesives can effectively trasfer and distribute stress, thereby increasing the strength and diffness of the composite.
Effective transfer of stress from one member to another depends on the strength of the links in an imaginary chain of an adhesive-bonded joint.
Thus, performance of the bonded joint depends on how well we understan and control the complexity of the factors that constitue the individual links-wood, adhesive, and the interphasing regions between-which ultimately determine the strength of the chain.
The american Society for Testing and Materials (ASTM) defines an adhesive as a substanc
e capable of holding material together by surface attachment.
An adherend is a substrate held to another substrate by an adhesive.
adherend [əd'hiərənd]
n. 被粘物；黏剂
网络释义
adherend:粘附体|被粘物|涂胶体，粘附体
Adhesion is the state in which two surfaces are held togther by interfacial forces, which may be valence forces, intelocking action, or both.
valence ['veiləns] n. [化]价；原子价；化合价；[生]效价
网络释义
Valence:瓦朗斯|价数|原子价
身上长水泡valence band:价带|价电子带|价电带
近在咫尺的意思
bond valence:键价|释义：键价
valence force 原子价力
网络释义
上西楼valence force:原子价力猕猴桃酱>世好啤酒
valence force field:价力场
Organic polymers of either natural or synthetic origin are major chemical ingredients in all formulations of wood adhesives.
Polysaccharides and proteins are high molecular weight natural polymers derived from plants and animals.
Animal, blood, hide, cain, starch, soybean, dextrin, and celluloic adhesives are all derived from the natural polymers found in the indicated souces.
They have been ud as adhesives for centries and are still in u today, although they have been replaced mostly by adhesives made with synthetic polymers.
蚊哥The first wood adhesives bad on synthetic polymers were produced commercially during the 1930s.
This marked the beginning of fundamental changes in composition of adhesives from natural to synthesized polymers.
The adhesives could not only be stronger, more rigid, and more durable than wood, but also have much greater resistance to water than adhesives from natural polymers.
Synthetic polymers are chemically designed and formulated into adhesives to perform a great variety of bonding functions.
Whether the baes polymer is thermoplastic or thermotting has a major influence on how an adhesive will perform in rvice.
Thermoplastics are long chain polymers that soften and flow on heating, and then harden again by cooling.
They generally have less resistance to heat, moisture, and long-term static loading than do thermotting polymers.
Common wood adhesives that are bad on thermoplastic polymers include polyvinyl acetate emulsions, elastomeric, contacts, and holt-melts.
Thermotting polymers make excellent structural adhesives becau they undergo irreversible chemical change, and on reheating, they do not soften and flow again.
深圳翠竹公园They form cross-linked polymers that have high strength, have resistance to moisture and other chemicals, and are rigid enough to suport high, long-term static loads without deforming.
Phenolic, resocinolic, melamine, isocyanate, urea, and epoxy are examples of types of wood adhesives that are bad on thermotting polymers.
A formulation of wood adhesive consists of a mixture of veral chemically active and inert materials that vary in proportion with the basic adhesive polymer, which enhances performance, whether it be working characteristics, strength properties, shelf life, or durability.
Solvents disper or dissolve adhesive polymers, act as carries of polymer and additives, aid wetting, and control flow and penetration of the adhesive.
Water is ud as the carrier for most wood adhesives, primarily becau water readily absorbs into wood, is inexpensive, and is free of toxicity problems.长官的英文
Fillers of both organic and inorganic origins contribute to rheological control of the fluid system, particularly in reducing the spreading and penetrating of the adhesive into wood.
