In this post, for better understanding of Aramids and Para Aramid Fiber properties especially Twaron properties
Para Aramid Fiber Properties
If you want to have a better understanding of Aramids and their synthesis. Please follow, “what are Aramids and how they are synthesized?”.
The excellent properties of para aramid fiber properties are derived from their structure, in which aromatic ring and other bulky groups play an important role. For aramid applications, high oxidative stability, solvent resistance are very important and the presence of aromatic ring in the main chain of polymer is responsible for high oxidative stability, solvent resistance, stiffness and stability at high temperature with excellent mechanical properties. These are also the main points of Twaron Properties.
Aramids are formed by linking aromatic rings and amide bonds. Presence of steric hindrances restricts the rotation of N-C bond which is normally possible in other polymers where cis-conformation of amide linkage is produced for betterment in para aramid fiber properties. Due to the trans-conformation present in aramids, their molecules extend but do not form kinks under normal conditions. The disassociation energies of C-C and C-N bonds are also generally higher than other aliphatic polyamides because of the partially double bond character of C-N bond as it conjugates with the aromatic ring double bond.
All of these effects result in increased thermal stability and chain rigidity of aramids. This gives better Twaron properties and, also, make Aramid applications quite diverse. The hydrogen bridge between the extended adjacent polymer chains holds the polymer chains together, ensures good cohesion between, creates a high degree of orientation and forms a two-dimensional layered structure.
Other para aramid fiber properties (Twaron properties) that enable them to perform highly specialized functions are:
- High tenacity
- Structurally rigid with low elongation
- High Modulus
- Highly resistant to chemicals and solvents
- High-temperature stability
- Dimensionally stable
- Highly flame-resistant and self-extinguishing
- High toughness
Twaron Properties
On basis of Para aramid fiber properties, Twaron fibers are best in terms of a balance between mechanical properties, chemical resistance, and thermal stability.
If we talk about the mechanical strength of Twaron Fiber, their strength is five times higher than steel and 2 times at least higher than polyester fiber. Twaron properties become so important because of their excellent chemical resistance to organic chemicals.
General idea about Twaron properties is displayed below:
Commercial Forms of Aramids
There are commercial forms available for Aramid applications. Some of these forms are:
- Films
- Fibers
- Paper
Films
Several Japanese companies Toray, Teijin, and Asahi have developed aramid films since the 1990s. Solutions or films is one of the main areas of Aramid applications. The solution of aramids is extruded into films using flat dies. The films of m-aramids are prepared by the conventional wet process through which unidirectional and the bi-oriented film is formed. The films of p-aramids are complicated to form due to laborious processing steps. PPTA/H2SO4 solution is extruded and exposed to the steam treatment. After steam treatment bi-axial stretching, drying and specific annealing is done. These aramid films find their application in the electrical industry.
Fibers
Due to high melting points, melt decomposition and other para aramid fiber properties, it is impractical to form aramid fibers by melt spinning.
Flexible chain homo and copolymers are the only commercially available aramids that are drawn into fibers via dry spinning by dissolving them into NMP and DMAc to form isotropic solutions. Dry-jet wet processing is another process of aramid fiber formation patented in 1973 by Blades. Aramid fibers have a wide range of applications as they are used in fiber-reinforced composites. KEVLAR fiber is one of the main commercial product of Aramid applications.
Paper
A mixture of fibroids and fibers forms aramid paper which is also referred to as flock. Due to their superior properties, they are used in the aerospace industry for many different Aramid Applications applications.
Aramid Applications
High thermal, mechanical and other para aramid fiber properties make aramids high-performance engineering material. They have a very wide range of applications for different purposes. The areas in which aramids are used to achieve desired functions can be classified as:
- Aerospace industry
- Marine industry
- Sports industry
- Defense applications
Aerospace industry
The high tenacity, good shear, high resistance to chemicals and better fatigue properties enable aramids to be used for aerospace applications. They are used to form core structures of several interiors and exterior panels. Forming flooring panels from p-aramids is a recent commercial adaptation in Airbus A-340 and the double-deck Airbus A-380. Honeycomb structure made up of aramid is used in aircraft, flooring, antennas, military shelter, fuel tanks, aircraft leading and trailing edges, missile wings, galleys, radomes, helicopter rotor blades and navy bulkhead joiner panels in PN2 aircraft.
Sports
As aramids are lightweight materials but have very high strength and stiffness so they are also used in sporting goods. Tennis rackets, skis, fishing rods, golf shafts and surfboards are some of the sports goods manufactured using aramids as reinforcing material. They have excellent resistance to solvents and high toughness so a wide range of vessels such as canoes, catamarans, kayaks, and racing boats are also made by aramids.
Marine applications
High fatigue resistance, resistance to solvents and excellent stiffness of aramids is also utilized in marine applications. Sailing yacht, motorboats and fast cruising and racing that demands high strength and safety are made up from high modulus, low weight and flex fatigue resistant aramids. Hulls are also made from fibers of aramids to get a wide range of benefits such as high energy absorption, high strength, low weight as well as vibration and sound dampening properties.
Defense Applications
Due to lightweight, high thermal and flame retardant properties aramids also find their applications for defense purposes. They are very comfortable and flexible when drawn into fibers so they can easily be used for making fire-resistant clothing.
Aramids are also used in ballistic applications due to dampening properties and fatigue resistance. They are used in making bulletproof helmets, soft body armors and hard ballistics.
