The PlasticsEurope website describes polyethylene as:. Polyethylene is reliable under every circumstance and it can easily deal with tropical temperatures as well as the frosty cold of the polar circle. This tough material is hard wearing. Yet it is remarkably light and it can be processed into all kind of articles without any problem. It can be found in everything from packaging films, to plumbing pipes, to housewares and grocery bags.
Different characteristics such as stiffness or elasticity can be imparted to the polyethylene during production, depending on the density of the material and its liquidity in melted form. Pressure applied during production can also have an effect on the density or liquidity.
Producing polyethylene at low pressure forms straight, robust and tightly packed branches. The result is dense polyethylene with a firm and stiff structure.
Manufacturing polyethylene at high pressure causes the particles to form a crisscross of branches and side branches, resulting in a lighter, more elastic material. To summarize, since polyethylene is a challenging material, it is best to utilize FT-IR, FT-NIR , and ICP-MS methods for identifying and measuring the density of the material, the liquidity of the material, the pressure used, the alloyed materials, the amount of alloyed material, the metal content, and the specifications of the finished products — among other things — in order to produce quality material that meets customer requirements.
Your email address will not be published. If the ratio of polyethylene compared to other materials in a product is incorrect, problems can occur. For example, when plastic fasteners were cracking over time, FT-IR analysis was done to discover the problem. Examination of the expanded hydrocarbon stretching region of the failed and control parts showed that the ratio of the polyethylene to polypropylene in the failed part was significantly higher than in the control part.
The higher relative amount of polyethylene created a part that was not as stiff as intended, making it more prone to deformation and cracking under long-term stress. In a similar situation, a section of plastic tubing used in a refrigerator had leaked while in use, so it was examined and analyzed. This type of tubing is generally extruded from a grade of low density polyethylene LDPE. It was discovered that the molecular degradation caused by oxidation through contact with chlorinated municipal water resulted in a marked reduction in mechanical integrity of the tubing material, and together with the nominal internal pressure, produced cracking within the tubing.
Chemically reinforced polyethylene is used in many industrial applications. Fluorination of the polyethylene surface is one of the processes for improving its performance. However, to obtain the specified material, the fluorination level must be monitored to ensure correct measurements.
The new process causes the polymer to conduct heat very efficiently in just one direction, unlike metals, which conduct equally well in all directions. This may make the new material especially useful for applications where it is important to draw heat away from an object, such as a computer processor chip. The work is described in a paper published on March 7 in Nature Nanotechnology. The key to the transformation was getting all the polymer molecules to line up the same way, rather than forming a chaotic tangled mass, as they normally do.
The team did that by slowly drawing a polyethylene fiber out of a solution, using the finely controllable cantilever of an atomic force microscope, which they also used to measure the properties of the resulting fiber. The high thermal conductivity could make such fibers useful for dissipating heat in many applications where metals are now used, such as solar hot water collectors, heat exchangers and electronics.
Chen explains that most attempts to create polymers with improved thermal conductivity have focused on adding in other materials, such as carbon nanotubes, but these have achieved only modest increases in conductivity because the interfaces between the two kinds of material tend to add thermal resistance. But using this new method, the conductivity was enhanced so much that it was actually better than that of about half of all pure metals, including iron and platinum.
Producing the new fibers, in which the polymer molecules are all aligned instead of jumbled, required a two-stage process, explains graduate student Sheng Shen, the lead author of the paper. The polymer is initially heated and drawn out, then heated again to stretch it further. Already, the degree of conductivity they produce, if such fibers could be made in quantity, could provide a cheaper alternative to metals used for heat transfer in many applications, especially ones where the directional characteristics would come in handy, such as heat-exchanger fins like the coils on the back of a refrigerator or in an air conditioner , cell-phone casings or the plastic packaging for computer chips.
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