Macrogol PEG is the basis of a number of laxatives. PEG is also used as an excipient in many pharmaceutical products.
The polymer is obtained in a similar way to the slurry method. A mixture of ethene and hydrogen is passed over a Phillips catalyst in a fixed bed reactor Figure 6.
Ethene polymerizes to form grains of HDPE, suspended in the flowing gas, which pass out of the reactor when the valve is released. Modern plants sometimes use two or more of the individual reactors in series for example two or more slurry reactors or two gas phase reactors each of which are under slightly different conditions, so that the properties of different products from the reactors are present in the resulting polymer mixture, leading to a broad or bimodal molecular mass distribution.
This provides improved mechanical properties such as stiffness and toughness. By kind permission of Total.
The HDPE powder coming out of any of the reactors discussed above is separated from the diluent or solvent if used and is extruded and cut up into granules. This method gives linear polymer chains with few branches. The poly ethene molecules can fit closer together.
The polymer chains can be represented thus: This leads to strong intermolecular bonds, making the material stronger, denser and more rigid than LDPE. The polymer is not transparent.
Linear low density poly ethene LLDPE Low density poly ethene has many uses but the high pressure method of manufacture by which it is produced has high capital costs. Any of the three processes, slurry, solution and gas phase, can be used when a Ziegler-Natta catalyst is chosen.
The gas phase process is used when the inorganic catalyst is employed. Small amounts of a co-monomer such as butene or hexene are added to the feedstock. The monomers are randomly polymerized and there are small branches made up of a few carbon atoms along the linear chains.
The side chains are known as pendant groups, or short chain branching. The molecule can be represented as: The structure is essentially linear but because of the short chain branching it has a low density.
The structure gives the material much better resilience, tear strength and flexibility without the use of plasticisers.
This makes linear low density poly ethene an ideal material for the manufacture of film products, such as those used in wrappings. The properties of the polymer, and hence its uses, can be varied by varying the proportion of ethene and co-monomer and by using different co-monomers.
All this can be done without shutting down the plant, an enormous advantage.
By kind permission of BP. Another name for this family is single site catalyst. Each catalyst is a single site catalyst which produces the same PE chain. Chemists have compared the structure of metallocenes to that of a sandwich.
There is a transition metal often zirconium or titanium 'filling' a hole between layers of organic compounds. The catalysts are even more specific than the original Ziegler-Natta and it is possible to control the polymer's molecular mass as well as its configuration.
Either the slurry or solution processes are usually used.Instagram is a fun and quirky way to share your life with friends through a series of pictures. Snap a photo with your mobile phone, then choose a filter to transform the image into a memory to.
benzene or chlorobenzene used as the solvent since both polymer (polythene) and monomer dissolve in these compounds at the temperature and pressure used. Water or other liquids may be added to dissipate the heat of reaction as the polymerization reaction is highly exothermic.
Polyethylene is classified by its density and branching.
The scientific name polyethene is systematically derived from the scientific name of the monomer. The alkene monomer converts to a long, Look up polyethylene in Wiktionary, the free dictionary.
Plastic is material consisting of any of a wide range of synthetic or semi-synthetic organic compounds that are malleable and so can be molded into solid objects.. Plasticity is the general property of all materials which can deform irreversibly without breaking but, in the class of moldable polymers, this occurs to such a degree that their actual name derives from this specific ability.
Different properties of polymers - higher.
Ethene can be polymerised in slightly different ways to make low-density polyethene (LDPE) and high-density polyethene (HDPE). Look into "investigate" is from s; look up "research in books or papers" is from s. To look down upon in the figurative sense is from ; to look down one's nose is from To look forward "anticipate" is c; meaning "anticipate with pleasure" is midc.