Polymer composites
Modification of organic materials adds additives. There are a few notable exceptions. Combination that is caused by a micro-structure unique to the product or unique microstructure. Additives are used primarily for:
Improving and controlling of processing characteristics.Property modification or enhancement.
Cost reductions across the board
Types and components of polymer composites
Polymer composites are a mix of polymer and organic or inorganic additives with geometrical certainty (flakes spheres fibers and particles). They are composed of more than two phases or components. The polymer is incorporated in a geometric pattern that covers the entire product. Laminate Thermoset – a common example based upon a fiber – is usually classified as high-performance polymer or large compound due to its length. The additive can also be discontinuous. For example, it could consist of short fibres. In these regions, the platelets are of the same nanoscale as the dispersed fibers. This is what we call nanocomposite. Because they contain multiple interfaces, they differ from microcomposites. Nanocomposites are unique in their properties and have great potential to be used for advanced applications. Composites are also classified by the nature (natural versus synthesized) of their matrix or filler. These are highly complicated structures that consist of fibers or particles, either continuous or not, embedded on a matrix. The fibre cellulose, lignin and other components are included. Bone is made of proteins, collagen and calcium-phosphate. Spider silk contains organic Nano-crystals within an organic matrix. Molluscs have shells made up of mineral layers of hardness, separated by protein binders. A micro-composite with mica flakes and thermoset polymeric matrix contains a similar platey structure providing a tortuous way for liquids, vapours, and gases.
Composites are classified according to their intended use or application. Someone can differentiate between two types bio-composites. Ecological bio-composites are made from a mixture of natural fibres, particulates and polymers from renewable or non-renewable materials. They are distinguished by their environmental degradation. Bio-composites are a combination of biostable, biodegradable, and inert polymers, with bioactive and inert fillers, that are used in biomedical applications such as orthopaedics or bone regeneration. Reinforcements with a stiffer, stronger polymer are used to increase the strength and modulus. The mechanical properties can have an impact on thermal expansion, stability and transparency.
When prepared in specific geometric patterns, continuous composites can be made up of long fibers and ribbons. Dis-continuous Composites consist of directional reinforcing materials such as short fibers or flakes that are arranged according to a geometric pattern and direction determined by selected molding and processing methods. There are however, manufacturing methods which can produce continuous oriented-fibre thermoplastic composites with very high fiber contents. These materials are often used for high-performance engineering Polymers.
Effects of Fillers/Reinforcements: Functions
In the past, fillers have only slightly increased the modulus of polymers due to their geometrical characteristics, surface area or chemical composition on the surface. The strength (tension and bending) has not changed. The main benefit of fillers was that they reduced the price of materials, by substituting the most expensive ones. The increased thermal conductivity could also lead to a faster molding cycle, and fewer rejected parts because of warpage. Inorganic fillers have a tendency to reduce the shrinkage or thermal expansion in moulds. The term reinforcing-filler was coined to describe additives which have undergone a change in surface chemistry, or their shape to enhance the mechanical properties of polymers. The inorganic Reinforcing Filler is rigider than the matrix. It is also less deformed. As a result, the matrix will deform, and the overall particle size will decrease near the interface. The fibre pinches and stiffens the polymer around it.
Aspect ratios of high reinforcement fillers can be defined as the ratios of length to diameter or thickness. The modifications not only enhance the filler’s main function (in this instance, it is used as a measure of mechanical properties), but can also add or increase additional features. Fillers can be modified or replaced to achieve new functions, which will expand their application. After the commercialization, talc and asbestos fibres formed the first group. They were chosen for their advantages in heat resistance and stiffness. Second-generation excipients were created as a replacement for asbestos because of its health risks. It was discovered that mica was an effective talc additive to increase heat resistance and hardness, whereas calcium carbonate had a lesser effect in hardening PP-like polymers. It was discovered that by modifying the surface of mica with bonding compounds to improve adhesion as well as the modification to the calcium carbonate-stearate dispersion to enhance these functions.
Functional Fillers, classification & Types
Filler can refer to a wide variety of materials. Fillers are solid particles (inorganic or organic) that can be fibrous, juicier or irregular. They are commonly used as bulk loaders in plastics. Fillers come in a wide range of chemical compositions, shapes, sizes, and properties. In general, fillers are highly rigid materials. They can be used in either a liquid or a solid state. As fillers, inorganic and organic materials are classified by their chemical families or by their size and shape. Particulate fillers like mica, calcium-carbonate, Kaolin, Talc, Feldspar and Aluminium Hydroxide are widely used. Fiber fillers include glass fibres and natural fibers. Carbon black is a filler that has been used for years. These products include montmorillonite such as hydrotalcite and montmorillonite as well as various oxides, nanofibers like single-walled or multi-walled nanotubes, and various oxides. Halloysite and graphene nanotubes can be used as additives in advanced nanocomposites. The first is made from a honeycomb-like structure of tightly packed carbon atoms, while the second is created by the surface weathering of minerals containing aluminosilicate. Natural nanotubes. Fillers can have multiple functions and are classified according to their primary function, as well as by the multitude of secondary functions.
