Polymer Chemistry, Ceramics, and Composite Materials
Polymer Chemistry
For obtaining a polymer in polymer chemistry, hundreds of thousands of molecules (monomers) are chemically bound. Homopolymers are obtained if the polymer chain is formed by the union of identical monomers. If the polymer chain is formed by the union of different monomers, copolymers are obtained.
Polycondensation: The chain growth occurs by chemical reaction between two functional groups, in most cases with the loss of a small molecule, such as water or hydrochloric acid.
Polyaddition: Chain growth occurs by continuous addition of the same type of small molecules that bind to others without causing the loss of any molecule.
Oil: A dark liquid, less dense than water. It is a mixture of hydrocarbons composed of hydrogen and carbon. Contains paraffin, naphthalene, and aromatics.
Polymer Types
Thermoplastic Polymers: Form long chains of carbon atoms that are relatively rigid. Plastics are made in this way, as they can be shaped by heat and subsequent solidification in a mold. Commonly used examples are polyethylene, polystyrene, and methacrylate.
Thermosetting Polymers: More resilient and fragile, forming cross-linked chains of carbon atoms. They do not support recycling since they decompose when heated. Examples include phenolic resin adhesives, polyurea, and some elastomers.
Elastomers: Polymers such as rubber. They can deform under pressure and return to their initial shape when the pressure is released. Examples include silicone, polybutadiene, and polychloroprene.
PET (Polyethylene Terephthalate): A polyester used in fiber manufacturing. Currently, it is used in the manufacture of flasks, bottles, films, and parts.
Ceramic Materials
Ceramic materials are compounds composed of metallic and non-metallic elements bound ionically and/or covalently. They behave better than metals and polymers at high temperatures and in aggressive environmental conditions; however, their fragility makes them unsuitable for many industrial applications.
Types of Ceramic Materials
Glass: Contains approximately 70% silicon, along with soda and lime. It is a non-crystalline ceramic.
Ceramics: Lose their crystalline state through controlled solidification procedures and then reach a polycrystalline state. Used in applications like heat exchangers or cooking hotplates.
Clays: Hydrated aluminum silicates that are easily molded. Their products are classified into white line and structural ceramics.
Refractories: Composed of coarse particles of metal oxides, along with finer refractory materials. They resist chemical attack and high temperatures.
Abrasives: Examples include diamond, silicon carbide, tungsten carbide, and alumina.
Cements: Calcium silicates in powder form, which, when mixed with water, form a paste that hardens over time at room temperature.
Ceramics (High-Strength): Very resistant to impact, but their processing is slow and expensive. These ceramics have higher mechanical resistance than other ceramic materials.
Advanced Ceramics: Includes carbides, nitrides, oxides, and borides. They have excellent high-temperature mechanical and physical properties.
Specific Advanced Ceramics
Aluminum Nitride: Good electrical insulator with high thermal conductivity. Used in the manufacture of integrated circuits.
Silicon Carbide: Excellent corrosion resistance at elevated temperatures. Used as a coating for metals and in the manufacture of high-temperature materials.
Boron Carbide: A hard, lightweight material extremely resistant to wear by abrasion.
Alumina and Alumina Oxide: Pure alumina metal is ductile and malleable, able to withstand impacts without breaking. Alumina oxide ceramic material is chemically very stable with a melting point of 2020°C, resistant to high temperatures but very fragile.
Cermet: A composite material consisting of ceramic particles in a metallic matrix.
Composite Materials
Composite materials are formed by a matrix or binder material and other materials in the form of fibers or particles as reinforcement. The resulting material possesses the best properties of each component. Classification is based on reinforcement:
Types of Reinforcement
Particle Reinforcement: Particles are harder than the matrix and improve the mechanical properties of the composite material. Cermets are made with hard particles like titanium carbide (TiC) in a metallic matrix of nickel or cobalt.
Fiber Reinforcement: Fibers are enclosed in a soft and ductile matrix.
Structural Reinforcement: Classified into laminar and sandwich structures. Laminates are composed of stacked plates with different reinforcements in different directions, such as plywood. Used in the manufacture of fuselages, aircraft, and building walls.
Types of Matrices
There are several types of matrices (details not provided in the original text).