What is thermo oxidative degradation?
Oxidative degradation is usually initiated when polymer chains form radicals, either by hydrogen abstration or by homolytic scission of a carbon-carbon bond. This can occur during manufacture, processing or during service when exposing the polymer to light or heat.
What causes thermal degradation?
Thermal degradation occurs when the polymer changes its properties under the influence of increased temperature. Initially, it causes the migration of low-molecular-weight additives in aging materials, if any are present.
What causes oxidative degradation of polymers?
Oxidative degradation (Coury et al., 2004; Griesser, 1991) in polymers occurs as a result of a chemical reaction that takes place when the material is exposed to oxygen, for example hydrogen peroxide can degrade polymers oxidatively (Griesser, 1991).
What is thermo oxidative stability?
This chapter discusses thermal-oxidative stability and degradation of polymers. Thermal stability refers to the ability of a material to maintain desirable mechanical properties such as strength, toughness or elasticity at a given temperature.
What is mechanical degradation?
Mechanical degradation describes the breakdown of molecules in the high flow rate region close to a well as a result of high mechanical stresses on the macromolecules. This short-term effect is important only in the reservoir near the wellbore (and also in some of the polymer handling equipment, in chokes, and so on).
What is pharmaceutical degradation?
PHARMACEUTICAL DEGRADATION. The incapacity or incapability of a particular formulation in a specific container to remain within a particular chemical, microbiological, therapeutical, physical & toxicological specification.
What is thermogravimetric analysis used for?
Thermogravimetric analysis (TGA) is an analytical technique used to determine a material’s thermal stability and its fraction of volatile components by monitoring the weight change that occurs as a sample is heated at a constant rate.
What is photodegradation of polymers?
Light – induced polymer degradation, or photodegradation, includes the physical and chemical changes caused by irradiation of polymers with ultraviolet or visible light. In order to be effective, light must be absorbed by the substrate (polymeric system).
How can oxidative degradation be prevented?
Both antioxidants and thermal stabilization aids can be added to WPC formulations to decrease thermal degradation during processing. In addition to protecting the polymer during processing, antioxidants can also help protect the polymer matrix during environmental exposure (Klyosov, 2007).
How many types of polymer degradation are there?
The types of polymer degradation can be divided into three general categories: chain depolymerisation, random scission and substituent reactions.
What is thermal stabilization?
Thermal Stabilization is a heat treatment process performed on chemically stabilized alloys (primarily Stainless Steel) to introduce certain carbides while avoiding others.
What is thermal stability in chemistry?
Thermal stability of polymer is defined as the ability of the polymeric material to resist the action of heat [22] and to maintain its properties, such as strength, toughness, or elasticity at given temperature [23].
Which tissue has all the pathways of amino acid synthesis and degradation?
The liver is the only tissue that has all the pathways of amino acid synthesis and degradation.
Why are amino acids deaminated in the fed state?
Most amino acids are deaminated to produce α-keto acids. In the fed state these α-keto acids can be used to synthesize triacylglycerols.
What is muscle protein degradation?
Muscle protein degradation supplies these amino acids, which the liver uses to synthesize the glucose and ketone bodies required to sustain life.
What is biosynthesis of non essential amino acids?
Biosynthesis of nonessential amino acids. Non essential amino acids are synthesized from intermediates of metabolism or, from essential amino acids. Synthesis from α-keto acids Ala, Asp and Glu are synthesized by transfer of an amino group to the α-keto acids pyruvate, oxaloacetate, and a-ketoglutarate respectively.