Wednesday, February 3, 2010

Starch Adhesives

Starch adhesive, or glues were first used in large scale industrial application approximately in the 1910s. The chief kinds on the marked today are made from cornstarch, tapioca flour, wheat flour, and potato starch. Starch adhesive may be applied cold chief advantages over animal glues, although most of them have the disadvantage of less strength and lower water resistance than animal glues. Starch adhesives are less costly than synthetic resin adhesives. Native starch is widely employed as an adhesive for veneer, plywood and corrugated cartons and laminated boards where water resistance is not important. Incorporated with 5 to 15% resins, such as urea formaldehyde, it is used for cartons where water resistance is important. Through enzyme conversions it is a base for many liquid adhesives. Native starch is the raw material for hydration to dextrin and British gums; these are modified glues for glass, metal, and wood, cartoons, laminated broads, and padding glues. Tapioca dextrin is the adhesive used for postage stamps.

Native starches are prepared from grains or roots. Dextrin is made by heating a dry starch with dilute acid, causing partial hydration. British gums result from heating native starch with small amount of catalysts; they are gummier and more adhesive that dextrin. In the manufacture of starch adhesives, dextrin, British gums, or starch are rarely used alone. Many chemicals may be admixed as indicated. Borax increases viscosity, gum-mines, rate of tack, and speed of production.

Starch adhesive mostly used for paper glue, this starch adhesive price vary some of them are expensive depend on the anti-spoil substance and concentration of these chemical they use, some of cheap product very easy to spoil because they use low concentration of this substance.

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