CHARACTERISTICS OF INSOLE MATERIALS:
Insole form the base of the shoe on which the upper is lasted. When a shoe is used, the foot rests on the stage of insole and brings to bear all type of mechanical stresses. It therefore, provides protection to the foot along with the outer sole and also takes up moisture in the form of perspiration from the foot. Insoles may be half or full depending upon the construction and design of the shoe.
The properties for an ideal insole material are:
To absorb moisture readily and dry out quickly.
Durable enough to stand up to friction in wear.
Flexibility, and does not harden and harden and crack in wear.
Dimensionally stable (does not alter in shape in manufacture or wear).
Uniformity in thickness and quality.
Light in weight
Ability to hold tacks, adhesive, or stitches.
In footwear industry the following materials are used for insole making.
1) Insole board/cellulose board
2) Shank board/backer board
3) Leather board
4) Leather
5) Shank
Insole board/Cellulose board:- Cellulose board for insole are made from wood pulp, resin and bonded with latex. As with leather boards it is supplied in sheet in various thicknesses, and in different grade. This material has better dimensional stability than leather boards.(i.e. does not shrink or grow). It is a flexible board. Common trade names are Texon, Bontex. Typically women’s insole use cellulose board of thickness 1.25 – 1.75 mm and men’s insoles boards of thickness 1.5 – 2.25 mm. from a standard sized sheet of dimensions 150 x 100 cm about 33 pairs of men’s insole can be obtained which translates to a usages norm of 450 square centimeter per pair of insoles. Similarly for women’s insoles about 38 pairs can be produced from a sheet of 150 x 100 centimeter which is equivalent to swage norm of 395 square centimeter per pair of insole.
The characteristics of this material are:
a) Its ability to absorb moisture
b) Uniformity of substances
c) Resistance to shrinkage or growth (in change of humidity and heat)
d) Resistance to hardening or cracking due to moisture or perspiration.
f) Durable enough to stand up to friction in wear.
g) Flexible in nature.
h) Resistance to fungal growth.
Leather:- leather is not much used because of high cost and the lack of uniformity in thickness. The type of leather which is used for making insole is vegetable tanned leather(VT Leather) . Leather insole were usually cut from bellies (sometimes shoulders), and are now used only in very high-quality footwear e.g. men’s welted.
Leather board:- A flexible manufactured board made up with at least 75% leather fibers, which gives it the ability to absorb perspiration. It is made in sheets in various thicknesses (mm), and in different grade to suit particular shoe making requirements e.g. tack holding, cement bonding, high pressure/heat for injection molding. Common trade names are Ferrersflex, Articor. Many grades of leather board are available and this material extensively used in the footwear trade as a insole material as well as toe puff and stiffener. Leather board is manmade material widely used by shoe industry. It is a compound of fibrous substance, vegetable matter and leather scrape bound together with latex rubber. Resin and alum are used in it while mixing. It helps to make the board more waterproof. The alum takes part to thicken with the latex.
General characteristics of a leather board:
Width, length, thickness can be made to order, as opposed to the varying thickness and sizes of leather pieces.
It has most of the quality and properties of leather.
Cheaper than leather.Superior flexibility and durability as compared with card board or any other
types of boards.
It retains the leather look, which other types of boards do not have.
Economic in manufacturing, the ingredients being are waste materials and by-products of trimmings and shavings from chrome tanned leather.
Shank board/Backer board:- This is a very hard and strong fiber board, able to withstand the tremendous loads which occur in the waist and heel of the shoe. It is again produced in much the same as way as paper. However the main raw material is mixture of waste and recycled paper which, together with the vegetal bonding resins used in its manufacture, make shank board a very environmental friendly product. The molding quality of this type of board is less than cellulose board. The standard sheet size of shank boards are 150 x 100 centimeter and the thickness start from 1.5 mm and goes up to 6 mm. The raw materials which are used for the manufacturing of cellulose shank board are Paper pulp. Dye, Hard resin binder, Aluminum sulphate, Preservative etc. The other materials which are used for making shank boards are fiberglass, plastic, injected material. The im
portant properties of backer boards are
a. Rigidity
b. Surface appearance
c. Resistance to de laminations
d. Nail holding strength
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