How can polyester resins be used

It is also known as calcium phosphate. This compound is most commonly used for biomaterial and fire resistant applications. This compound can be physically blended in polymers to suppress, reduce, delay or modify the propagation of flame through polymeric materials. The fire retardant property of hydroxyapatite is due to the presence of phosphate. The technical specifications of hydroxyapatite used in this work are given as below:.

Zinc borate, 2ZnO 3 B 2 O 3 3. It has good thermal stability, lower density and good miscibility with most of the polymers. Zinc borate shows excellent fire resistance performance and can be therefore widely used in polymer, rubber, fibre, paint and ceramic industries. The technical specifications of zinc borate used in this work are given below:. Fly ash is the finely divided mineral residue resulting from the combustion of coal in electric generating plant.

Fly ash consists of inorganic matter present in the coal that has been fused during coal combustion. This material is solidified while suspended in the exhaust gases and is collected from the exhaust gases by electrostatic precipitators and is usually of silt sizes 0.

Fly ash is a pozzolanic material and has been classified into two classes F and C based on the chemical composition of fly ash. In the present study class C fly ash was used. Class C fly ash is produced normally from lignite and sub-bituminous coals. The technical specifications of fly ash used in this work are given below:. The formula of antimony trioxide is Sb 2 O 3. It is a solid white powder and is used mainly as fire retardant additive and as pigment.

The substance comes in various grades, depending on particle size. The breakdown of particle size affects both physical properties and pigment property. The finer fraction is used for pigmentation. The flame-retardant property, however, is not affected by particle size. This property is based on antimony trioxide reacting in the event of fire with the surrounding material, with the result that a protective layer of various antimony compounds covers the combustible materials.

Since the formation of these compounds consumes heat and because they are generally difficult to ignite, they protect the underlying material from ignition. The technical specifications of antimony trioxide used in this work are given as below:.

Several combinations were tested to determine effects of each additive in the polymer formulations. Additives in different amount were mixed with prepolymer polyester resin in a round bottom flask equipped with high speed agitator.

The resultant formulations were compounded with glass fibre as reinforcing materials and benzoyl peroxide as initiator for composite preparation.

Composites were prepared by hand lay-up technique using about 50 weight percent of glass fibre and filler. Two percent benzoyl peroxide BPO was used as initiator. GPC is one of the most powerful and versatile analytical technique available for understanding and predicting polymer performance. It is the only proven technique for characterizing a polymer by its complete molecular weight distribution.

Refractive Index detector was used with internal temperature of 35 0 C for peak detection. The GPC system was calibrated with eight different polystyrene standards having molecular weight ranging from to 2. Gel permeation chromatography of polyester resin is shown in figure An IR spectrum of prepolymer polyester resin is shown in figure The spectrum was run by applying resin sample on KBr cell covering the range of frequencies from cm -1 with scanning period of 20 seconds.

The crushed powder sample mg in the form of a pellet was prepared by mixing with dry KBr 1g. A broad-spectrum absorption bend at cm -1 confirms the presence of —C-O-C- of ester linkage. A medium absorption band at cm -1 can be attributed to —C-H bending. GPC of Polyester Resin. An IR spectrum of cured polyester resin is shown in figure This instrument measures the weight loss as well as the rate of weight loss of a material continuously as a function of increase in temperature. The cured sample about 8 to 12 mg was placed in the sample container and suspended on the quartz rod in an atmosphere of nitrogen gas.

The weight of the sample was noted on the TGA balance. The whole assembly was introduced into the furnace and the experiment started by heating the system at constant and definite rate throughout the experiment. The experiment was stopped when no further change in weight could be observed on further heating. Proper knowledge of the thermal stability of polymers is essential for their appropriate applications [ 93 - 95 ]. The thermal behaviour of polymers with reference to their thermal stability is of paramount importance.

TGA thermograms of all the composites indicate a similar decomposition pattern of two steps degradation. The first step can be assigned to degradation of resin part and the second one to that of filler part. In unfilled composite figure-5 loss of weight at , , , and O C is In filled composite figure-6 loss of weight at , , , and O C is Filled composites show very good thermal stability than unfilled composites.

In this work, fire behaviour of composites was evaluated. Many procedures exist to evaluate fire behaviour of the composite materials [ 96 - 97 ]. The key fire resistance properties of interest for polymers to be used in fire resistance applications are ease of ignition, flame spread, ease of extinction, smoke obscuration, smoke toxicity, heat release rate and limiting oxygen index.

In the present study limiting oxygen index ASTM D was determined to characterize the composites. Thermogram of FRC Fennimore and Martin developed this method [ 98 ]. The specimen used for LOI test having size mm length, 10 mm wide and 4 mm thick. The top edge of the test sample is ignited and the oxygen concentration in the flow is decreased until the flame is no longer supported.

Oxygen Index is calculated from the final oxygen concentrations tested. This is very simple and advantageous method for assessing fire resistance of polymers. The critical amount of oxygen was measured. LOI is expressed in percentage as:. Table-1 represents limiting oxygen index of filled and unfilled composites.

In the present study values of limiting oxygen index of filled composites are in the range of In practice material is often called the self extinguish materials if LOI is greater than 26 [ 99 ].

Thus the results of present study are in good agreement with the reported values. The results clearly indicate that the composites of present study can be used in all fire resistance applications.

Composites prepared using fillers give better fire resistance than unfilled composites and also there is increase in fire resistance with increase in amount of filler. Mechanical properties measured in this study include Izod impact strength, Rockwell Hardness and Flexural strength. The impact properties of the polymeric materials are directly related to the overall toughness of the material.

The objective of the Izod impact test is to measure the relative susceptibility of a standard test specimen to the pendulum type impact load.

The results are expressed in terms of kinetic energy consumed by the pendulum in order to break the specimen. A study of Izod impact strength was carried out in terms of resistance to breakage under high velocity impact conditions, according to ASTM D [ ]. Zwick model No. For the measurement, a specimen was cut from the fabricated composite 6.

The test specimen was clamped into position so that notched end of the specimen remained facing the striking edge of pendulum. The impact test indicates the energy to break standard test specimen of specified size under the stipulated conditions of specimen mounting and pendulum velocity at impact. All the measurements were carried out at room temperature. Hardness of a material is defined as the resistance to deformation, particularly permanent deformation, indentation or scratching.

The Rockwell hardness test measures the net increase in depth impression as the load on an indentor is increased from a fixed minor to a major load and then returned to minor load. Rockwell Hardness study was carried out at room temperature according to standard method of testing ASTM D [ ]. Udyog Pvt. Load of kgf was applied for each measurement. The specimen with parallel flat surfaces was placed on the avail of the apparatus and minor load 10kgf was applied by lowering the steel ball onto the surface of the specimen.

The dial was adjusted to zero on the scale under minor load and the major load kgf was immediately applied by releasing the trip lever.

After 15 second the major load was removed and the specimen was allowed to recover for 15 second. Rockwell hardness was read directly on the dial. It is one of the most important mechanical properties of interest for any comparison of rigid materials or modulus of rupture. Flexural strength is the ability of the material to withstand bending forces applied perpendicular to its longitudinal axis. For the measurement, a strip of the dimensions 8.

It suited the gauge length of 7. The test was initiated by applying the load to the specimen at the specified crosshead rate. The deflection was measured by gauge under the specimen in contact with it in the centre of the support span. Table—2 represents Izod impact strength, Rockwell hardness and Flexural strength. Mechanical Properties of Fire resistance Composites [ 92 ].

The mechanical properties of composites improve remarkably with increase in the filler content except in antimony trioxide and fly ash.

Increase in mechanical properties with increase in filler content is due to the reinforcement action provided by the filler particles to the polymer matrix [ - ]. Composites prepared using non-traditional fillers in combination with traditional filler gives better performance than unfilled composites and also there is increase in mechanical properties with increase in amount of fillers.

Antimony trioxide gives poor results compared to other fillers and also mechanical performance decreases with increase in amount. The results also revealed that the fire retardancy of the polyester based composites can be improved by using non traditional fillers like zinc borate, hydroxyapatite and fly ash.

They have an advantage over a traditional filler antimony oxide to increase the fire retardancy without decreasing mechanical and thermal properties of the composites. There is however, considerable variation in the efficiency of these fillers. The adequacy of the fire resistance performance of these filled composites is dependent on both types of filler and incorporation level of the fillers.

The use of antimony oxide and fly ash increases the fire resistance behaviour but there is decrease in mechanical properties and thermal stability.

The use of such fillers can also solve the problems of toxic emissions of halogenated fire retardants and also it lowers the cost of polyester resin. The composites can be used for facade elements, dome light crowns, in the transportation sector, in the electrical industry, e. The unbeatable combination of characteristics such as ease of fabrication, low cost, light weight and excellent insulation properties have made composite materials to be one of the most desirable materials for electrical applications.

The electrical properties of polymers are related to the behaviour of polymers as an electrical insulating material for the general interest. The purpose of electrical insulation may generally be described as the prevention of unwanted contacts between the electrical conductors at different potentials. A simple example such as two mounted terminals can usefully serve as an illustration. The insulation must maintain the separation under a wide variety of environmental hazards which include humidity, temperature, vibration, radiation, presence of gases, moisture and other contamination.

It must be sufficiently strong physically to withstand the mechanical forces which may be exerted by the conductors and at the same time must prevent any significant flow of current between the conductors. No insulator is perfect, but what constituents a significant flow of current depends upon the application. A few micro amps in an electrical supply circuit would be negligible. In every case the current must be sufficiently small to eliminate secondary effects such as temperature rise, mechanical stress and electrochemical action.

The primary function of thermosetting plastics in electrical applications has been that of an insulator. Thermosetting plastics not act as effective insulators but also provide mechanical support for field carrying conductors. For this reason the mechanical properties of thermosetting plastics materials used as insulators become very important.

The use of glass-reinforced laminates in the field of dielectric materials has been of prime importance in the engineering materials. The choice of dielectric material depends upon its dielectric and other properties over a wide range of temperature and dielectric field frequencies. Investigation of dielectric properties is one of the most convenient and sensitive methods in studying structural property relationship of the glass reinforced for engineering purpose. Typical electrical application of fibre reinforced composite include terminals, connectors, industrial and house hold plugs, switches and printed circuit boards.

Now a day unidirectional glass reinforced polymer composites have become a popular alternative to porcelain in the manufacture of high voltage insulators [ - ]. Several investigations on the effects of electrical properties and mineral fillers have been reported [ - ]. Survey of literature revels that there are some reports about the dielectric behaviour of the glass reinforced laminates [ - ]. The glass fibre reinforced laminates were studied for the electrical properties.

There are several experimental and numerical procedures which can be used to evaluate the laminates in terms of electrical properties [ - ]. It is also lightweight and easy to bend and control. Once covered with the resin, you get a durable and smooth fiberglass surface. Another benefit of this kit is that the resin will last slightly longer — giving you more working time. This does mean that the resin takes longer to fully cure. However, this can be adjusted using a heat applicator.

Working with polyester resin will require a quality fiberglass cloth for best results. This 3M fiberglass cloth by Bondo offers just the right qualities for great performance. There are interlocking strands on the fiberglass which help to cover up holes effectively.

This also makes the fiberglass easier to cut down to size with scissors and can be used on all kinds of projects. This fiberglass is fully waterproof and works very well for waterproofing certain areas or covering up holes or cracks. The cured product can be sanded down pretty easily and painted over with all kinds of paints. The fiberglass can be used over all kinds of different surfaces and areas. It offers excellent structure and durability when combined with polyester resin, while still being easy to work with.

This is thanks to its thinner qualities. Depending on your project, it is a good idea to know what to look out for when buying poly resins. What you need will depend on what you are doing, but the basic supplies include the following. We will also have a look at how to handle polyester resin, laminating, and creating a negative mold using polyester resin. Gather all the materials before you begin working, you want everything at hand when you are busy with the resin.

The entire process depends on the application, so we are going to now have a look at laminating and creating a mold. Molds come in both positive and negative forms, negative molds are great for things like model making or car body parts. Positive molds are used more for pond and swimming pool manufacturing. The curing time for the polyester resin is mainly dependent on the product, but also a few other things.

Also known as tempering. The polyester resin goes through a chemical process when curing, becoming thicker until it achieves a gelling point. The resin then becomes fully hard or completely cures. When higher temperatures are produced, the pot time or working time is reduced.

This is because the resin is less viscous. In cooler temperatures, the working and curing time are increased, sometimes up to seven days. Note: When a focused and even heat is applied, this can advance the composition to augment the mechanical properties. When applying this tempering process, you should remove any air bubbles that form.

This is to inhibit any weakening in the final structure. If you are looking to increase your processing time, adding an inhibitor is one way of doing this.

These chemical compounds will then set back the process of curing. This is especially helpful if you are working with a substantial amount of polyester resin. How many inhibitors should you add?

The general rule is if you include 0. Add 0. We do not recommend adding the inhibitor to the gelcoat, as it may affect its structure. Polyester resin can be colored just like epoxy resin but be mindful, as the colors can affect the structure of the final finish. Synthetic resins involve a delicate balance of hardener and resin.

By including other elements, could upset this balance and create changes in the structure and appearance of the resin. In other words, when adding color, these will influence the resin viscosity, which then affects the process of curing. Therefore, always make sure you use suitable color elements, specifically designed color pigments and pastes for polyester resin. Also, in most cases, the original color might differ from the color in the resin once it has cured.

So, to achieve the results you want, it might be necessary to carry out a few test samples before heading off to your main project. This might sound tedious, but it will save money and time. Take note when the resin viscosity changes, this might be a bit difficult at first but with experience, you should get it right.

When adding color to more viscous resin, you will find it difficult to blend the color uniformly. Also, if the resin is too thin, the color will form streaks. The polyester resin in its liquid form is toxic, so taking some precautions are necessary. Make sure your workspace is well-ventilated, or even better work outside. Wear a respirator mask, protective eyewear, gloves, and clothing. Your skin should never come into direct contact with the resin. Do not work in living spaces like the living room, as the resin gives off toxic fumes during the curing process.

Do not work with resin near an open fire or smoke while working. Try to avoid getting any polyester resin on surfaces you are not working on, as it is difficult to remove once cured. Lay some newspaper around your workspace to prevent this. However, if the resin has not cured yet and you act quickly, you can remove it with acetone.

Unfortunately, the resin cannot be removed if it lands on a porous surface. Note: If you are using a cobalt accelerator and ketone peroxide during cold curing, always add the two elements one at a time.

This stirring must be thorough and careful as any air introduced into the resin mix affects the quality of the final moulding. This is especially so when laminating with layers of reinforcing materials as air bubbles can be formed within the resultant laminate which can weaken the structure. It is also important to add the accelerator and catalyst in carefully measured amounts to control the polymerisation reaction to give the best material properties.

Too much catalyst will cause too rapid a gelation time, whereas too little catalyst will result in under-cure. Colouring of the resin mix can be carried out with pigments. To reduce the cost of the moulding To facilitate the moulding process To impart specific properties to the moulding. The use of fillers can be beneficial in the laminating or casting of thick components where otherwise considerable exothermic heating can occur. Addition of certain fillers can also contribute to increasing the fire-resistance of the laminate.

Twitter Facebook LinkedIn Email. Leave your comment Cancel reply. About Contact. Sign in. Connecting you to the composites industry. Polyester Resins Thursday, 24th January 0 comments Reading time: about 6 minutes Polyester resins are the most widely used resin systems, particularly in the marine industry.

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