Low density polyethylene (LDPE) – involves an older gas phase process (still used) with conditions: high pressure (1000-3000 times atmospheric), high temperature (300°C) and an initiator (an organic peroxide e.g. dibutyl peroxide, or oxygen). The resultant product has significant chain branching due to alkyl groups replacing hydrogen atoms on some carbon atoms. Consequently, the alkane chains cannot pack together in an orderly fashion, resulting in low densities and weak dispersion forces; therefore LDPE is soft, flexible and has a low melting point. The initiator isn’t strictly a catalyst as it is involved in the actual formation (one initiator molecule per ½ polymer molecule).
Outcome1 1) Define the main food groups • Fruits - The fruit food group encompasses a wide range of fresh fruits and fruit products, including dried, frozen and canned fruit, and 100 percent fruit juice. • Vegetables - Any vegetable or 100% vegetable juice counts as a member of the Vegetable Group. Vegetables may be raw or cooked; fresh, frozen, canned, or dried/dehydrated; and may be whole, cut-up, or mashed. • Grains - Any food made from wheat, rice, oats, cornmeal, barley or another cereal grain is a grain product. Bread, pasta, oatmeal, breakfast cereals, tortillas, and grits are examples of grain products.
The linkage of polymers is a determining factor in the properties of a substance, such as solubility, elasticity, and viscosity. When they contain carbonyl groups, polymers can form hydrogen bonds with adjacent molecules, resulting in a stronger material on a larger scale. Polymers are used in many aspects of human life; natural polymers form vital tissue in organisms while synthetic polymers are used to create various types of plastics, concrete, glass, and rubbers. Cross-linking is a chemical process responsible for creating polymers by forming chains that connect adjacent atoms in a large
Carbohydrates are made up of carbon, hydrogen, and oxygen. They consist of sugars and starches. Its molecules can be broken down into usable chemical energy and can be used to build cell walls. Lipids are nonpolar. Which include fats, oils, waxes, and cholesterol.
For about the next 450 years different variances of the steel bullet proof vest would emerge (Williams). But it wasn’t until 1971 when the invention of Kevlar completely revolutionized any kind of ballistics protection armor. The official name of Kevlar is Poly-paraphenylene terephthalamide. It is produced by monomers “ 1,4-phenylene-diamine (para-phenylenediamine) and terephthaloyl chloride in a condensation reaction yielding hydrochloric acid as a byproduct. The result has liquid-crystalline behavior, and mechanical drawing orients the polymer chains in the fiber's direction.
Crystallization from acetone yields the pure compound. Most of the numerous other ether soluble components of nutmeg remain in the acetone solution. Note that triesters of glycerol, such as trimyristin, in which the carboxylic acid portion of the molecule is unbranched and contains 14 or more carbon atoms, are
[1] At that time the phrase polymer, as introduced by Berzelius in 1833, had a different meaning from that of today: it simply was another form of isomerism for example with benzene and acetylene and had little to do with size. [2] Usage of the term to describe large molecules varies among the disciplines. For example, while biology refers to macromolecules as the four large molecules comprising living things, in chemistry, the term may refer to aggregates of two or more molecules held together by intermolecular forces rather than covalent bonds but which do not readily dissociate. [3] According to the standard IUPAC definition, the term macromolecule as used in polymer science refers only to a single molecule. For example, a single polymeric molecule is appropriately described as a "macromolecule" or "polymer molecule" rather than a "polymer", which suggests a substance, composed of macromolecules.
The parent chain will not always be in a straight line. You do not include substituents when counting for the parent chain. The carbonyl carbon atom is always located as the number one in aldehydes. In ketones, the carbonyl carbon atom receives the lowest number possible. Substituents are molecules attached to the parent carbon chain.
Many kinds of polyethylene are known, with most having the chemical formula (C2H4)nH2 in which the density is carried by changing pressure and temperature .Most important types are High-Density Polyethylene (HDPE) and low-Density Polyethylene (HDPE) Contents Abstract 1 List of Figures 3 Introduction 4 Theory 4 Classfication 4 High-Density Polyethylene (HDPE) 5 Processing Techniques 5 Low density polyethylene (LDPE) 6 Processing Techniques 6 Linear low-density polyethylene 9 Processing Techniques 9 Ultra-high-molecular-weight polyethylene 10 Processing Techniques 10 Structure and properties: 11 Conclusion 11 Difference in Density 11 List of Figures Figure 1 : Polyethylene 4 Figure 2: LDPE 7 Figure 3 : Autoclave and tubular high pressure technology 8 Figure 4 : LLDPE Plant Layout 10 Introduction Polyethylene is derived from either modifying natural gas (a methane, ethane, propane mix) or from the catalytic cracking of crude oil into gasoline. In a highly purified form, it is piped directly from the refinery to a separate polymerisation plant. Here, under the right conditions of temperature, pressure and catalysis, the double bond of the ethylene monomer opens up and many monomers link up to form long chains. In commercial polyethylene, the number of monomer repeat units ranges from 1000 to 10 000 (molecular weight ranges from 28 000 to 280 000). Figure 1 : Polyethylene It is a polymer of ethylene, CH2-CH2, having the formula (-CH2-CH2-)n, and is produced at high
Paper made from hemp is acid-free and lasts much longer and is stronger than paper made from trees. The hemp fabrics are stronger and more resistant to mold than any other natural fiber. [The first Levi’s blue jeans were made from hemp] (Julin, part I, para. 7). Hemp can be used to make plastic, replacing toxic materials as polyvinyl chloride (PVC).