I. ABSTRACT
Polymers are made from relatively small molecular fragments known as monomers that are joined together. Synthetic polymers which include the large group known as plastics are divided into three groups: commodity thermoplastic, engineering thermoplastics (ETP), and advanced engineering thermoplastics (AETP). The engineering thermoplastics (ETP) have heat resistance, strong mechanical properties, lightness, self-lubrication, and easy manufacturing. This plastic category has been lately used to replace wood and metal applications.
To have a better understanding of ETP, we will discuss about outstanding properties of some well-known engineering thermoplastics materials which are polyamides 12 (PA12), and polyether ether ketone (PEEK) in aerospace industry. Also, we will focus on major methods to enhance performance of engineering thermoplastics by modification via specialty additives. II. INTRODUCTION
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Synthetic polymers which include the large group known as plastics are divided into three groups: commodity thermoplastic, engineering thermoplastics (ETP), and advanced engineering thermoplastics (AETP). In recent years, the whole new generations of the engineering thermoplastics (ETP) have become commercially available. These offer properties far superior, particularly in regard to high temperature performance, excellent heat resistance, strong mechanical properties, lightness, self-lubrication, and easy manufacturing. This plastic category has been lately used to replace wood and metal applications and open the door to new types of application for
It was found that ATH can help to improve the flammability of HDPE composites in decreasing of heat release rate, total heat release and mass loss rate. With addition of inorganic flame retardants including RP and EG, the ATH flame retarded HDPE composites show obvious synergistic effects in improving the flame retardancy [72].
The Crystallinity of Kevlar Polymer strands, contributes to the unique strength and stiffness of the material. Kevlar is very similar to other common synthetic polymers, including Nylon, Teflon and Lycra. In all Polated to strength. Aromatic refers to the Carbon atoms attached in a ring, and Amides refers to a group of Carbon, Nitrogen and Hydrogen atoms. Kevlar fiber is therefore a “Polyaromatic amide”, as it has a high breaking strength.
The most common form of polyethylene is petroleum based or olefins based; as before mentioned polyethylene compounds have a wide commercial applicability and are made from non-renewable resources (Harding, Dennis, von Blottnitz, Harrison, & S.T.L., 2007). Its manufacturing processes are regarded as energy intensive and release significant amount of CO2 and heat into the atmosphere (Broderick, 2008). Next a little more detailed description of polyethylene’s production processes will be presented, with a focus on the way the material inputs are extracted and synthesized.
Polymeric materials play a functional role in every aspect of daily life, from clothing to infrastructure. Polymers differ greatly from other materials, such as ceramics or metals, based upon the types of bonding. Metals bond metallically, creating a sea of electrons, and ceramics generally bond ionically, strongly tying electrons to lattice points. Polymers bond covalently in carbon chains, which (in general) make their properties more variable due to the possibilities of arrangement in bond length, angle, and molecular configuration. Polymers, on average, tend to be more lightweight, have a greater range of colors, lower thermal and electrical conductivity, less brittleness, more resistance to acids, bases, and moisture, and higher dielectric strength than their ceramic or metallic counterparts, but with great range. This variety of properties leads to a variety of classifications, and therefore differing processing methods based on the classification of polymer.
Injection moulding is the most widely used polymeric fabrication process. It evolved from metal die casting, however, unlike molten metals, polymer melts have a high viscosity and cannot simply be poured into a mould. Instead a large force must be used to inject the polymer into the hollow mould cavity. More melt must also be packed into the mould during solidification to avoid shrinkage in the mould. The injection moulding process is primarily a sequential operation that results in the transformation of plastic pellets into a moulded part. Identical parts are produced through a cyclic process involving the melting of a pellet or powder resin followed by the injection of the polymer melt into the hollow
As our technology advances further, there will be a demand and need for new performance from engineering materials.
Thermoset polymers contain no set arrangement of chains and as such they can be classified as amorphous i.e. they contain no distinct crystalline structure [3]. Thermoset materials are formed from a chemical reaction of a resin and a hardener or catalyst and this reaction is irreversible and produces a hard and infusible material [4]. Cured thermosets will not become liquid again if heated but above a certain temperature their mechanical properties can change substantially. The temperature at which this change can occur is called the Glass Transition Temperature (Tg) and it varies depending on the particular resin and hardener/catalyst used as well as its degree of cure and whether it was mixed properly. If the temperature of a thermoset material is raised above the Tg, the molecular structure changes from that of a hard crystalline polymer to a more flexible amorphous polymer. At this elevated temperature the properties of the thermoset such as resin modulus (stiffness) drop significantly and as a result the compressive and shear strength of the composite will do the same. Other properties such as water resistance and colour stability also reduce above the resin’s Tg This change can be reversed by cooling the material back down to below the Tg.
Polymer-Polyethylene is partially crystalline as well as amorphous because it has crystalline and amorphous regions. Also it has linear chains so this is the simplest structure compared to a branched or network chain. This can be of an advantage to it over other types of materials as its good toughness and elongation makes it very significant in the engineering industry as it can be moulded or extruded into shape...
Polypropylene is one of those most versatile polymers available with applications, both as a plastic and as a fiber, in virtually all of the plastics end-use markets.[3]
M. W. Darlington and P. H. Upperton, “Procedures for Engineering Design with Short Fibre Reinforced Thermoplastics,” in Mechanical Properties of Reinforced Thermoplastics, D. W. Clegg and A. A. Collyer, Eds. Springer Netherlands, 1986, pp. 205–248.
Thermoplastics are the most commonly used raw materials for SLS process. Based on the applications, the raw materials can be selected based on the criteria’s related to mechanical properties, thermal properties, Electrical properties and manufacturing feasibility.
Everyone has heard a cashier one time or another mumble, “Paper or plastic?” as he put their groceries in a bag, but do shoppers know the effects of each vessel in which they carry their comestibles? There are many issues and benefits to both paper and plastic. The making and recycling of both paper and plastic bags can harm the environment. One must also look at the costs of making each bag. The convenience of each is also something to look at. Many people jump to conclusion that paper bags are better for the environment without knowing the facts. Since plastic bags are preferred by customers and plastic bags actually do not hurt the environment as much as paper ones do, consumers should feel at ease when choosing plastic.
Plastic fasteners have grown to become viable products for joining applications in various industries. They are regarded as suitable alternatives to metal fasteners, and are known for their flexibility, durability, and application versatility. The various material features and benefits makes them ideal products for applications in a variety of industries such as aviation, marine, automotive, construction, oil and gas, food and beverage, sewage plants, and heavy machinery.
But plastic is an extraordinary innovation that replaces many other expensive products with lightweight, strong easy to maintain , longer lasting material with a less expensive plastic. “Plastics are manufactured materials that can be shaped into almost any form.” Most plastics are made when two or more chemical compounds combine and cause chemical reactions to polymerize, or form a long chain of molecules to form. This causes the plastic to form. The plastic is then heated into a molten liquid and then molded into the shape needed. There are two basic types of plastics. They are thermosetting plastics and thermoplastics. The type of plastic it is determined by the way they react when heated. Thermoplastics are plastics that can be heated and melted and still reform its shape. Thermosetting plastics are just the opposite. They can be melted and cannot be reshaped into its original
Cryogenics comes from the combination of two different Greek words, namely “kryos”, which means very cold or freezing and “genes” means to produce. Cryogenics is thus defined as the branch of physics and engineering which deals with the study of very low temperature (below 123K), their production and the materials behavior at such low temperature.