ADHESIVE

ADHESIVE 

    These are those substances which are capable to holding materials together

# Advantages :-

- these are free from residual stresses

- In this no external force required 

- very fast and quick action

- even work on smooth surfaces

- adhesive joint also act as insulator

- adhesive substances are also resistance or corrosion free

- This adhesive also used to fix air tight chamber or leakage part

@ specific adhesive :-

      attachment of surfaces by adhesive by chemical or physical foreces of attraction

@ Mechanical adhesion :-

        in which adhesion show their effect on porous or rough surface to make adhesion between two surfaces

@ Fusion adhesion :-

       in this adhesion between two surfaces due to bondimg between two surfaces 

@ Developmwnt of adhesion :-

i) by loss of solvent :-

      these adheser work on suitable solvent 

ii) By heat :-

          some adheser work on specific heat when given to them

iii) By appplying pressue :-

 these are those adhser which work only when pressure applied on them EX;-  double sided tape work better when apply with some pressue

iv) by Chemical reacion :-

       some adheser work onlywhen some chemical agent are present

# Factor affecting adheser :-

- lesser the surface wet better will be the adheser work

- more is the porosity more will adheser work

- lesser the component are thermally conductive greater will bond form by adheser

- more the area more will the adheser bind easily and quickly

# Chemical factor affecting :-

* more wiil be the polar group in adheser more will be the strong bond formed

* more will be the material semi semid material more quickly adheser get it surface

* More will be the side chain present makes bond more stronger

* neutral condition make bond more stronger than alkali or alkaline condition

@ Classification :-

1. Thermosetting synthetic resins :-

               after adhesion bond become so strong due to cross linked netwok of adherser some example of these are Phenol-formaldehyde resin, urea formaldehyde resin ,polyester etc

2. Thermoplastic synthetic resin :-

          these are those adhesion which get soften when heated but at cool show proper adhersion, some example of these are cellulose acetate, ethyl cellulose, polivinyl eyc

3. Natural resin :-

        adheser obtained fron nature direct no chemical modification happen on this , some example of this are asphalt

4. Starch adhesive :-

             these are made by heating starch suspension in water , these are cheap,easy to use and handle 

5. Inorganic adhesive :-

                as name suggest no carbon compounds in this present totally inorganic material used in this

6. Vegetables glues :-

               glues prepared by soyabean,corn etc 

7. Animal glues :-

           glue which are obtain from animal dead bodies , these rae good adheser but lack bactrial,fungus moisture resistivity