Tuesday, February 25, 2020

High temperature polymers Essay Example | Topics and Well Written Essays - 2000 words

High temperature polymers - Essay Example Introduction: Polymers or most ordinarily known as plastics is used abundantly in a wide range of applications. In fact, they are seen almost anywhere in our daily lives. Polymers are those substances that are composed of individual monomers cross linked with long chains and bonds. They are composed of a long chain of carbon backbone constituted with other elemental contributions such as O,N,S,F, Si and S. Polymers are organic materials. Generally, their basic properties include lightweight, good insulation properties, ductile, low strength, and good noise and vibration dampers. There are plastics used widely in many industries and can even be seen in everyday lives. Majority of the packaging materials seen today uses polymers with varying densities. Polymer molecular structures are large with complex bonds and chains. There are high density polymers and low density polymers. As per molecular structure, these polymers differ in their chain length, chain branching and the inter-chain bonds (Reusch). As a common misconception, polymers are said to be applied in low temperatures as they are known to degrade immediately with the presence of heat and exposure to high temperature. There is however, a special kind of polymer- the high temperature polymer that exudes exemplary properties greatly superior than ordinary ones. Their applications are slowly introduced in the market and little by little replace the more conventional structural materials. High Temperature Polymers: Definition and Properties Plastics as considered with their physical appearance are not known to be used in high temperatures due to misconception that they easily melt with application of heat. This may be true somehow as most plastics found in nature are easily destructed with high temperature. However, there are some kinds of plastics that are designed differently from all the rest. Indeed, there are plastics and polymers that are resistant with temperatures and they are guaranteed to be of bes t application when high temperature and heat are concerned. High temperature polymers are those plastics that can withstand temperatures above 135oC. They are known as the ‘commodity’ plastics and at the moment, it has increased in the percentage in the total plastic usage (Performance 1). These are stable plastic materials derived through lengthy and vigorous research works and innovative inventions of brilliant minds that walked through this life that prove that the synthetic chemistry field has reached maturation. Applications of these materials range widely as there are many technologies where these polymers are used. It is important to note that high temperature polymers have properties that bypassed those ordinary ones. Heat transfer is mostly through conduction. Specific heats have a range of 0.7-2.5 kJ/kg-K. Polymer composites on the other hand have variable specific heats depending on the average weight of the components. Thermal conductivity ranges from 0.1 -0 .2 W/m-K (Tant et al 4). It is also important to note that the value may differ when there is incorporation of other particles in the materials (5). The maximum tensile stress application can reach from 455 kPa or 1820 kPa (6). Properties of composite polymers that are applicable for high temperatures have higher values as compared to other materials. High temperature

Sunday, February 9, 2020

Position paper 7 see below Essay Example | Topics and Well Written Essays - 500 words

Position paper 7 see below - Essay Example The action to be taken should be determined by a court of law. Killing without trial is only allowed in incidences self-defense or as a necessity to save more lives. That said target killing of terrorists, in my opinion, is an immediate necessity executed with the aim of saving more lives. Therefore, the United States should be allowed to continue killing terrorist based on their intelligence. The benefit of targeted killing is that, unlike an arrest operation, there are fewer risks. For example, in U.S, targeted killing are mostly executed using an automated drone craft. According to Becker  and  Shane (2012), among the counterterrorism tactic applicable, targeted killing has proved to be the most effective in the prevention of terror attacks. A targeted killing meant to kill a leader of a terrorist organization disrupts terrorist organization’s plans to a point of collapsing. For example, killing the Gaza military commander, Salah Shehadeh, prevented six terror attacks he planned to execute in Israel. Base on the outcome of targeted killing Obama’s regime has embraced the tactic as the most effective approach to eradication Al-Qaeda and Taliban members Afghanistan-Pakistan border. However, United States need make targeted killing acceptable in other countries by justifying the tactic. For instance, United States should not engage enforcement operations in a foreign country without their knowledge. Doing so is a violation of peaceful relations and international norms (Taylor, 2013). The government should come up with a set of norms that support targeted killing but upholds and acknowledge the principles of peace. Additionally, the collateral damage that comes with targeted killing need to be considered. Regardless the fear of an attack plot advancing following delays to counterattack, consideration should be given to damage expected. The government need to form policies that validate all operations