In Partial Fulfilment for the Requirements of CHE 413N

The Science and Engineering of Materials

INDIVIDUAL REPORT

POLYESTER GLASS

Submitted to:

Engr. Angelo H. Cabije

Submitted by:

Siclot, Karynne Bernardine G.

Date Submitted:

September 5, 2014

I. Introduction

Composite materials are broadly defined as those in which a binder is reinforced with a strengthening material. One such composite which is the focus of this study is polyester glass.

Polyester glass is a composite material made of unsaturated polyester matrix reinforced with glass fibers. It is a specific type of fiberglass and can also be referred to as glass-reinforced plastic (GRP). Fiberglass may also be composed of other polymer resins such as epoxy or thermoplastics. As the topic suggests, this report will tackle fiberglass with polyester resin.

Polyester, the resin or binder in which the glass fibers are embedded, is a functional group for thermosetting polymers. Thermosets are highly cross-linked polymer chains that from a three-dimensional network structure; and with that, these polymers possess good strength, stiffness, and hardness (Askeland, 2012, p. 636). Glass fibers are embedded into a polyester matrix in order to further increase its stiffness without significantly increasing its density for certain applications which will be discussed later in this report.

This report aims to show an explanation of how polyester glass is made and also present its properties, structure, and uses or applications. The report presents the details of this particular composite in terms of materials science and engineering concepts.

II. General Properties

Each of the various components retains its identity in the composite and maintains its characteristic structure and properties

When both glass and polymer are combined to form a composite, we obtain a material that is

• lightweight

• nonconductive

• high strength to weight ratio

• weather resistant

• cost effective

The tables below show quantitative information on polyester glass properties.

III. Atomic Model of the Structure (polyester)

A polyester is a large molecule made up of a number of individual molecules containing ester groups, linked together. An ester group contains a carbon double bonded to an oxygen. The carbon forms a single bond with either a single hydrogen atom or an "R" group containing carbon and hydrogen. The same carbon atom is single bonded to an oxygen, which forms another single bond with another "R" group. The basic diagram is: R-CO-O-R.

IV. Structural pictures (microstructure)

Microstructure of glass fiber reinforced polyester composite.

Atomic model of polyester (polyethylene terephthalate)

The picture shows a microscopic view of polyester glass. The material is magnified showing the rod-like glass fibers “glued” together in a polyester matrix.

V. Preparation/Synthesis

Polyester Resin

The polyester is formed by the condensation reaction:

The ester thus formed contains an alcohol group and an acid group, which can then react further, forming a polymer:

Difunctional alcohols and acids react to form the ester. Then it is cured with the monomer styrene to polymerize which is the main step in the pultrusion process.

Glass Fibers

Glass fibers are formed by extruding molten glass which is mainly made of silica into long fibers with a diameter ranging from 4 μm to 34 μm. These fibers are used as is to form the polyester glass or woven into flexible cloth for increased strength. The pattern of weave determines the strength and weight of the glass reinforced plastic, after resin has been

added.

Pultrusion

There are many industrial processes for manufacturing polyester glass. One of the most common is pultrusion. Pultrusion is a portmanteau word, combining "pull" and "extrusion".

Samples of different weaves of fiberglass: woven, chopped mat, and unidirectional

It produces continuous lengths of fiberglass-reinforced plastic shapes with a constant cross-section. With this technique, continuous fiber rovings, or tows (loose and untwisted bundle of continuous fibers that are drawn together as parallel strands), are first impregnated with a thermosetting resin (polyester resin for polyester glass) containing the monomer styrene and accelerators and catalysts for curing; these are then pulled through a steel die that performs to the desired shape and also establishes the resin/fiber ratio. The stock then passes through a curing die which is heated to initiate curing or the resin matrix. A pulling device draws the stock through the dies (Callister, 2008, p.648).

A diagram of the pultrusion process:

1 - Continuous roll of reinforced fibers/woven fiber mat2 - Tension roller3 - Resin Impregnator4 - Resin soaked fiber5 - Die and heat source6 - Pull mechanism7 - Finished hardened fiber reinforced polymer

The heart of the pultrusion process is the curing die. This is the part where solidification occurs. During this step, the resin undergoes polymerization. The polyester resin includes a catalyst to aid it in curing or in turning it from a liquid into solid. The heat in the curing die begins the thermosetting reaction process that cures the resin matrix. The liquid resin undergoes cross-linking to generate polyester chains, forming a hardened, three-dimensional network structure. The polyester resin which acts as a glue to the glass fibers is solidified to hold the fibers together.

Other processes for the manufacture of polyester glass are gun roving (generally for boat hulls), filament winding (for hollow cylindrical products like pipes, tubes, or posts), and molding.

VI. Uses

With the characteristics of polyester glass especially having a high strength to weight ratio, it can be used in a variety of applications such as the manufacture of boat hulls, road transport vehicle bodies, building applications (insulation), waterpark slides, furniture, alternative for steel, and many more products.

VII. Documented Case Study

A case study was published by the civil engineering department in Technical University of Lisbon on glass fiber-reinforced polyester entitled: Durability of glass fibre reinforced polyester (GFRP) pultruded profiles used in civil engineering applications. The study presented the results of experimental research on the physical, chemical, mechanical and aesthetical changes suffered by glass fiber reinforced polyester (GFRP) profiles under accelerated exposure to moisture, temperature and ultraviolet (UV) radiation. The durability tests conducted for the study proved the generally good behavior of GFRP under aggressive conditions.

VIII. References http://www.intechopen.com/books/polyester/fibre-reinforced-polyester-

composites http://www.technologystudent.com/joints/fibre1.html http://www.ehow.com/info_8672529_chemical-composition-polyester-

resin.html http://nzic.org.nz/ChemProcesses/polymers/10B.pdf http://www.compositesworld.com/articles/the-making-of-glass-fiber http://www.dcwort.co.za/polyester-glass-gpo3 http://www.moldedfiberglass.com/materials/polyester-resins http://en.wikipedia.org/wiki/Fiberglass http://composite.about.com/od/whatsacomposite/a/Selecting-Composite-

Materials.htm http://www.civil.ist.utl.pt/~jcorreia/Papers/ICPaper6.pdf Askeland, D. Science and Engineering of Materials. 6th ed. Callister, W. Materials Science and Engineering.