DESCRIPTION :

Basically, polyester resins are polycondensation products of dicarboxylic acid with dihydric alcohol. The resins are available in many forms, generally depending upon the raw materials which go into their manufacture and their method of production. And because of this, they can be tailored to meet many specialized requirements.

The polycondensation yields an unsaturated polyester if at least one od the components contains a double bond in its molecule. The double bond in unsaturated polyester enables the material to be cured by subsequent crosslinking, normally, crosslinking, normally effected by copolymerization with an unsaturated monomer e.g. styrene. As the result of curing, an insoluble and heat resistant polymer is produced, having a three-dimentional molecular structure, formed by a crosslingkage of the double bonds of the polyester with those of the monomer.
Unsaturated polyester is a result of an exothermic reaction. Organic peroxides are predominantly used as catalyst for the curing process. In practice, unsaturated polyester dissolved in styrene is used almost without exception, and curing effected by one of the following two methods :

COLD CURING (ROOM TEMPERATURE CURING)
Cure is begun by adding an initiator, usually methyl ethyl ketone peroxide (MEKP). Typically, promoters or accelerators (e.g. cobalt naphthenate) are used to promote the decomposition of the initiator at room temperature.

HOT CURING (HIGH TEMPERATURE CURING)
Benzoyl peroxide is generally used as catalyst and polymerization is induced by high temperature treatment. An accelerator such as dimethyl aniline is also normally employed.
Unsaturated polyster resins are thermosetting and have the following properties :

• In Their uncured state, they are liquid and therefore capable of easy handling, may be cast, coated on or sprayed.


• They have good physical properties


• They are cured to a solid material by catalytic reaction with the application of neither pressure nor heat is essential in the curing process, nor is the there any tendency for gaseous or liquid component to separate out


• They are easily pigmented to very wide variety of colors by MATAPEL UNIPOL® Pigments pastes

DIRECTION FOR USE:

MATAPEL UNIPOL PIGMENT PASTES are highly concentrated preparations of organic and inorganic pigments, which the vehicle is compatible with polyester resins, particularly gelcoats, lay-up and casting resins.
The pastes may be dispersed directly into polyester resins by mechanical mixer or by hand. It is advisable initially to mix a little resin with the required quantity of Unipol color paste, stirring vigorously. The remainder resin is then added slowly with continuous stirring.
Normally, required quantity of Unipol pigment pastes will generally vary between 3 to 5% for gelcoats and 1 to 2 % for thick objects (calculated by weight).
In clear polyester resins, a small percentage (0.05 to 0.2%) of Unipol organic pigments yield transparent shades of remarkable brightness and clarity. Unipol organic pigments are frequently selected for non-transparent coloration in preference to pure pigments, as the required high opacity is simply attained by addition of Unipol White Paste. Unipol organic payments may be mixed with Aluminum paste or pearl paste. This is recommended in order to obtain metallic or pearl colours with lustrous effect.
In full shades. Unipol inorganic pigments are mainly recommended for the use of full shades. They are not as bright as organics pigments for use of depth shades (reduced with paste).
Unipol pigment pastes have good stability with long shell life.