Negrican Sandalcı 030070084 1st Week

RESIN (NEW / BETTER)

The resins are typically based on cross-linked polystyrene, where the ion-exchange properties are conferred by the presence of functional groups such as sulphonate (cation-exchange) or quaternary ammonium (anion-exchange).

There are lots of type of resins could be found. We can recognize some of populer ones as alkyd resins and epoxy resins.

Alkyd resins have been introduced in the 1930s as binders for paints. Their compatibility with many polymers and the extremely wide formulating latitude made them suitable for the production of a very broad range of coating materials. This includes do-it-yourself paints and varnishes for wood and metal, road marking paints, anticorrosive paints, nitrocellulose lacquers, two-component isocyanate curing coatings, acid curing coatings, stoving enamels, etc. Except for phthalic anhydride, being of petrochemical origin, the other raw materials used in the synthesis of the alkyds are from biologically renewable sources. This, combined with their biological degradability, makes them very interesting binders from an ecological point of view. Solvents which are used to reduce and adjust the paint viscosity are the only concern with respect to the ecological aspects of the alkyd paints. In recent years, however, we witness quite an activity in designing alkyd emulsions and high solids alkyds which can serve as binders for environmentally friendly coatings.

The first alkyd resin was synthesized in the mid-1920s by Kienle, who combined the already known technology of producing polyester resins based on glycerol and phthalic anhydride (the so-called Glyptals) with the empirical knowledge of producing oleoresinous paints already existing for several centuries. Kienle also classified the alkyd resin in three groups: long, medium and short oil resins, a classification nowadays still in use. Full-scale commercial production of alkyd resins began in 1933 at General Electric and it was followed by other companies after in 1935 Kienle's patent was ruled invalid because of the anticipation of prior art . Shortly after commercialization started, the alkyd resins enjoyed explosive growth replacing the oils as binders in the old-fashioned oleoresinous paints offering much better coating properties at a very attractive price.

Table 1 shows the carbon footprint of a collection of binders in the form as they leave a well-assorted resin plant. Looking at these figures one should realize that they are all of different solids content. The performance of a coating is, amongst others, related to volume solids, which is in turn a function of the solids by weight. Therefore, in prediction of the durability and in this way the total carbon footprint per unit of human satisfaction, this solids content by weight should be taken into consideration.

Table 1. Energy content of some classes of binders, delivery form.

Product class	NREU (GJ/tonnes) in process	NREU (GJ/tonnes) in raw materials	Total expressed as CO2, tonnes/tonnes supplied product
Traditional (85% in white spirit)	4.4	46	2.8
Polymer dispersion (47% in water)	1.6	58	2.8
Fatty acid modified polyurethane dispersion	1.6	43	2.3
Alkyd emulsion (53% in water)	4.5	34	2.0
High solids alkyds (90% in aliphatic white spirit)	4.4	48	3.2

Biobased raw materials constitute typically 60–70% of an alkyd.

Epoxy resins are used extensively as adhesives and as a matrix for fiber reinforced composite materials because of their good thermal, mechanical, and adhesive properties, excellent solvent

resistance, and high dimensional stability. Current demands for high performance materials have increased the usefulness of epoxy resins as structural adhesives and as the matrix resin for advanced composites. Both of these applications demand high strength, high modulus, and good adhesion characteristics in

the epoxy resins.

However, such uses require good fracture resistance and impact strength, which epoxy resin does not generally exhibit. A major drawback of epoxy resins is their inherent brittleness (having low fracture energy, ranging from 80 to 200 J/m);1−3 that is, they easily fail under impact because of highly crosslinked structure,1 and this has led to extensive research efforts to improve their low toughness.

(Ting, R. Y. Epoxy Resins, Chemistry and Technology, 2nd ed.; Marcel Dekker: New York, 1988

 A. Hofland,  Pigment Resin Technol., 23 (4) (1994), pp. 7–11

 K. Holmberg, High Solids Alkyd Resins,Marcel Dekker, New York (1987) )

Resin transfer molding ( OLD )

High volume production of FRP component demands automation of the molding process for efficiency, component quality, and safety issues. Automated high volume production of processes due to the simplicity and maturity of such techniques, SMC and BMC, for example, are used extensively inthe automotive industry. A disadvantage of these methods is that short fibre orientation is difficult to control during injection, causing a wide variation in the component mechanical properties. As a result, short fibre reinforced components are limited to non-structural application.
Rtm is a closed-mould FRP process which can utilize low moulding pressures and low cost flexible tooling. RTM can be used to produce complex components with high fibre volume fraction and a good surface finish. The process involves the placement of dry reinforcement in closed matched moulds followed by the injection of a liquid thermosetting resin. The resin is polymerized either at ambient or elevated temperatures and the component is removed with a smooth surface on both sides. Several types of resin system are available including polyesters, vinyl esters, urethane methacrylates, phenolic resin and epoxy resins. The choice depends on both cost and application. Prior to moulding the reinforcement is often shaped to produce a fibre preform in a seperate process. The preform can consist of different hypes of fibres such as glass, polyester, aramid or carbon in several forms such as woven fabric, continuous filament random mat, non-crimp fabric or chopped strand mat.
(P.W. Dufton,Lightweight Thermoset Composites: Materials in Use, Their Processing and Application, p. 151)