Unsaturated Polyester Resin -as a matrix

Lukkumanul hakkim N.CBPST kochi

lukku007@gmail.com

Polyester resin

The most important esters are those derived from carboxylic acids Polyesters are defined as polymers containing recurring –CO-O-

groups in the main chain A large number of polyesters is commercially available: –Unsaturated polyesters –Poly(allylester)s –PET

–etc

Unsaturated Polyesters resin

Linear polyester containing aliphatic unsaturation which provides sites for subsequent cross-linking

Prepared from di ethylene glycol and maleic anhydride and could be cross-linked by reaction of styrene

During the past few years the use of polyester moulding compositions has grown significantly, particularly in the transportation field

Linear unsaturated polyesters are prepared commercially by the reaction of a saturated diol with a mixture of an unsaturated dibasic acid and a “modifying”dibasic acid (or corresponding anhydrides).

The function of the modifying acid is to reduce the number of reactive unsaturated sites along the polymer and hence to reduce the cross-linking intensity and brittleness of the final product.

Reactive ingredients

Diols -propylene glycol-Diethylene glycol-Neopentylene glycol-Ethylene glycol

Unsaturated acids and anhydrides -maleic anhydride-pthalic anhydride(modifying anhydride)

Cross linking monomer -styrene

Preparation Linear unsaturated polyesters are prepared batch-wise by heating a mixture

of the appropriate acidic and hydroxyl components in a reactor jacketed for heating and cooling and fitted for distillation.

A typical formulation for general-purpose material might be as follows:-Propylene glycol100 parts by weight-Maleicanhydride72 parts by weight-Phthalicanhydride54 parts by weight

The molar ration of the ingredients shown above is 1.2:0.67:0.33

The excess of glycol is to allow for loss during the reaction and to restrict the molecular weight of the polymer

The mixture is heated at 150°C-200°C for 6-16 hours and water is continuously

distilled from the reactor. Sometimes xylene is added to the reaction mixture to assist in the removal of water by

azeotropic distillation and sometimes catalyst such as p-toulene sulphonicacid is added to reduce the reaction time.

In order to prevent discoloration, the reaction is carried out in an inert atmosphere of either carbon dioxide or nitrogen

Heating is continued until the average molecular weight of the polyester reaches about 1000-2000.

The polymer is then cooled to about 90°C and pumped into a blending tank containing vinyl monomer to which has been added an inhibitor such as hydroquinone.

In a general purpose material, the weight of styrene used is about half that of the polymer

The blend (which is commonly referred to as ‘polyester resin’) is then

allowed to cool to room temperature. The reaction between hydroxy-compound and anhydride proceeds in

two distinct steps. In the first step, esterification of the anhydride occurs to form a free

acid group which is then esterified in the second step. Reaction is ;

Mechanical properties

Thermal properties

UPR composites -as a matrix material

Nano /micro Silica- UPR composite Nano inorganic fillers are used in polymeric matrix

for improving the electrical, mechanical and physical properties

UPR-silica composite is one of the popularly used composite resins for electrical insulation application

Addition of nano material improves its partial discharge,dielectric strength and surface degradation properties.

PREPARATION Adding varying amount of silica nano or micro particle to UPR

resin under agitation. The mixture was then, subjected to ultrasonication coupled with

mechanical agitation, using an rpm of 1,500 ± 50. This was done in a temperature controlled bath which was maintained

at 25°C for a period of 8 hours The required amount of initiator was then, added and stirred. The

composition was then poured into Teflon and metal moulds. They were allowed to cure at room temperature i.e. 25 ±1°C for 12

hours. This was followed by post-curing at 80 ± 1°C for four hours. The composites were then, allowed to stabilize for 7 days at 25 ± 1°C

and it had 50% relative humidity

Properties

The electrical properties of pure UPR resin and its composites were evaluated.

The investigation revealed that the nano silica-UPR composites exhibited better surface, volume resistivity, dry arc resistivity, dielectric strength, dielectric constant and dissipation factor when compared to the micro composites and neat resin.

This was due to the surface and interface modification of the polymeric matrix by the nano material.

Nano silica composites have larger inter-surface area than micro composites or pure resin due to the formation of one additional nano phase.

Therefore it should show higher improved surface, volume and arc resistivity, dry arc resistance and tan delta.

It is observed that the higher the dispersion of silica in the UPR resin better is the electrical property of silica-UPR composites

Glass fiber / UPR composites The most important polymer in glass fiber reinforced composite is

unsaturated polyester. In the last 40 years glass fiber/ polyester conceders as one of the

most famous composites because of its reasonable mechanical properties, low cost and easily fabrication techniques which include: spray, hand lay up reactive injection modeling and resin transfer,

marine transportation, contraction, electrical and industrial are the application area

Bending stresses are important in structure tests because of variety of loading situations in service.

Glass fibers used for the study are chopped and 0/90

Sample Preparation Hand layup (HLU) technique was used to produce three layer

composites. First the UPE liquid mix with methyl-ethyl-ketone-peroxide (MEKP)

hardener 10% liquid. The mixture reinforced by glass fiber with different values of volume

fraction. The glass mould of frame was (15x15x4) cm used for casting the

sheet of composite material. Wax was fixed on the inner mould faces before casting to ensure the

releasing of casting composites and having smooth faces. Samples were left to cure for two days at room temperature. The specimens were cut out of the molds with sample dimensions in

accordance with the related international , ASTM standard 790-D

Properties

The influence of reinforced type of fiberwas notice. The random composite was notice to have young modulus, max.

stress, and yield strength higher by comparing with the 0/90 composite

The same behavior was notice for X4 by comparing with X5, since the chopped fiber glass to absorb more ester monomers than 0/90 mate that lead to higher plastic content .

The photograph show the initiation of the cracks for all samples which indicates was notice in X2 and X4.

Bio fiber [bagasse fiber]/UPR composite Bagasse is the residue left after the crushing

of sugar cane for juice extraction. Bagasse studied ad useful for many value-

added industrial products to cater the needs in automotive, agriculture and other industrial sectors

Bagasse fibre is used after NaOH and acrylic acid treatment

Preparation

The bagasse fiber–USP composites were prepared by vacuum bagging technique. The vacuum process was carried out until the impregnation of the resin into the fiber mat was completed, followed by curing process in room temperature. Formula (1) is utilized in the preparation of the composites:

Properties

(a) Dynamic storage modulus and (b) tand for resin (as control), 20 vol.% of untreated and treated fiber based composites.

Addition of higher amount of fiber results in higher tensile and flexural properties of the bagasse fiber–reinforced polyester composites.

Higher tensile and flexural properties were obtained for treated fiber composites compared to those of untreated fiber based composites, with significant trend shown by AA treated fiber based composites.

Chemical treatments via NaOH and AA decreased the water absorption of composites, and increased the storage modulus and Tg of the composites

Reference Effect of fiber surface treatment and fiber loading on the properties of

bagasse fiber–reinforced unsaturated polyester composites V. Vilay a, M. Mariatti a,*, R. Mat Taib a, Mitsugu Todo b A Study of Bending Properties of Unsaturated Polyester/Glass Fiber

Reinforced Composites Estabraq T. Abdullah Effect of Nano/micro Silica on Electrical Property of Unsaturated

Polyester Resin Composites Ram Avatar Sharma, Dawid D'Melo, Subhendu Bhattacharya, Lokesh

Chaudhari,and Sarojini Swain

THERMOSETTING POLYMERS:Processing, Application and Future Direction

Dr. Hazizan Md Akil