Polymerization Time
Figures 3a-d show the effect of polymerization time on %GY (Fig. 3a) ; %GE (Fig. 3b); %TC (Fig. 3c) and %HP (Fig. 3d) at four different temperatures ( 50 0 ; 60 0 ; 70 0 and to 80 0C ). It is evident that , as the reaction time became longer , all polymer yield , except %GE , increased. The polymerization time corresponds to 180 min. brought about the maximum percentages for the positively dependence of polymer criteria. Enhancing effect of prolonging the duration of polymerization on grafting (%GY) and homopolymer (%HP) is reflected on the extent of total conversion (%TC) (Fig. 3). The latter increased as the time of polymerization increased particularly during the initial stages of the polymerization reaction.
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The latter embraced the salts of ferrous ammonium sulphate , manganous sulphate ans cobaltous sulphate. This pre-treatment process was carried out by impregnating the cellulose thiocarbonate fabric in a single metal salt solution at 30 0C for 30 min. , as described in the metathesis procedure. The pre-metallized cellulose thiocarbonate fabric was then grafted using moderate conditions included 4% MAA , 30 mmolL SPB , at 60 0C for 60 min. The results obtained are illustrated in Figure 5a-d. The data of this figure disclose (i) that the percentages graft yield (Fig. 5a) , grafting efficiency (Fig. 5b), and total conversion (Fig. 5c) enlarge by increasing the Fe2+ salt solution concentration and attain maximal at the FAS concentration corresponds to 0.2 mmol/L ; thereafter they decrease. The homopolymer (Fig. 5d) has an adverse deportment , (ii) that all polymer criteria slightly augment by heightening the Mn2+ salt solution concentration up to 0.02 mmolL ,then fall , (iii) that the Co2+ reductant ion fails to further improve the MAA grafting efficiency and graft yield. The %TC decreases by increasing the Co2+ salt solution concentration up to 0.06 mmolL , then increases. The lone prosperity of the Co2+ ion is the enhancement of MAA homopolymer
The purpose of this experiment was to create a polymer by reacting a mixture of decanedioyl dichloride and dichloromethane with a mixture of water, 1,6-hexadiamine and sodium carbonate. Specifically, we created the polymer Nylon-6,10. Nylon-6,10 polymers are used in a vast majority of things we use in everyday life such as zippers, the bristles in brushes, and even car parts. This experiment was different from the industrial method of making nylon because that takes place at a much higher temperature. A polymer is a substance that has a structure made of similar or identical units bonded together. All polymerizations fall into two categories: step-growth and chain-growth (both of which we used to form our polymer). Step growth polymerization
Investigating the Rate of Diffusion of Hydrochloric Acid into Gelatine Introduction = == == == ==
As can be seen, there is a point at which the rate of reaction becomes
Speed of Dissolving Jelly Introduction The investigation I have to do is I have to investigate what affects the speed at which the jelly will dissolve in water. This investigation will be using the theories we have covered on the rates of reaction and the collison theory. I am going to try to get the jelly to dissolve quicker by increasing the surface area. I predit that when increasing the surface area of some jelly, I think each time I change the surface area then the time the jelly dissolves will be increased. I think this because each piece of the jelly I will be using will be small, so in that case there will be less to dissolve, as I think increasing the surface area in any investigation will speed up a reaction.
A group of polymer chains can be organised together in a fiber. How the polymer chains are put together is important, as it improves the properties of the material. The flexibility, strength and stiffness of Kevlar fiber, is dependent on the orientation of the polymer chains. Kevlar fiber is an arrangement of molecules, orientated parallel to each other. This orderly, untangled arrangement of molecules is described as a “Crystalline Structure”. A manufacturing process known as ‘Spinning’ is needed to achieve this Crystallinity structure. Spinning is a process that involves forcing the liquefied polymer solution through a ‘die’ (small holes).
The future for the total artificial heart with respect to using polyurethanes comes in the form of thermoplastic polyurethane (TPU), also known as polyurethane elastomers that have molecular structures similar to that of human proteins. TPUs have slower protein absorption (protein absorption is the beginning of the blood clotting process) this makes TPUs ideal candidates in the manufacturing of the total artificial heart because it provides more adhesive strength and mimics certain elements within the body. Hence, biomedical polyurethanes can lead the way to eliminate some acute health challenges that the total artificial heart currently faces. By virtue of their range of properties, polyurethanes and their new applications will continue to play an important role in the future of the total artificial heart.
Bobby in the story symbolizes coming of age and being a single dad. Bobby has to raise a baby by himself when he lost Nia and now can't do the childish things as much as he used too. Bobby was now confused on where to go with Feather after high school. Bobby moves in with his brother so he can still have help with the baby. Bobby has now come of age where he has to make adult decisions for him and Feather.
The synthesis of polymers starts with ethylene, (or ethene). Ethylene is obtained as a by-product of petrol refining from crude oil or by dehydration of ethanol. Ethylene molecules compose of two methylene units (CH2) linked together by a double carbon
Acrylonitrile-butadiene rubber (NBR) is well-known unsaturated copolymers for concerning five decays [1-2]. It has been used in many industrial required purposes as hoses, o-ring seals, insulation base product and other many packaging materials []. The main components of technically related NBR comprise of 24-30 wt% of acrylonitrile and include some benefits in contrast to other elastomer like polymers. Such as, good processability, resistance to oils as well as hydrocarbons, especially resistance to hydrocarbons and oils, NBR has wide region of service temperature (from -35 oC up to 100 oC) [1-2].
German Chemist Hans von Pechmann first synthesized Polyethylene by accident in 1898 by heating diazomethane. His colleagues characterized the waxy substance polyethylene due to the fact that they recognized that it consisted of long ethene chains. It was then first industrially synthesized by accident in 1933 by applying extremely high pressure to ethylene and benzaldehyde. Over the years, development of polyethylene has increased due to the additions of catalyst. This makes ethylene polymerization possible at lower temperatures and pressures.1
There are numerous factors which can affect dimensions of subsequent casts on repetitive pouring. These include the process of polymerization (7), temperature (1), and material used to fabricate the replica or working cast (1). Although, PVS impression materials have demonstrated superior dimensional stability when compared with other elastomeric materials due to no releasing any by-products (8), it had been reported that the dimensional accuracy of a material is time dependent. A material may be highly dimensionally accurate soon after its initial polymerization but less accurate after the storage for a period of time (9). On the other hand, PVS impression materials have chosen as the impression material in many clinical situations because they possess excellent physical properties and handling characteristics
They are amorphous or solely moderately crystalline once injection shaped, but the degree of crystallinity will be abundant redoubled for fiber and film applications by orientation via mechanical stretching. The two most vital polyamides poly(hexamethylene adipamide) Nylon 6,6 and polycaprolactam Nylon 6. Both have wonderful mechanical properties together with high impact strength, high flexibility, high tensile strength, good resilience and low creep. They are straightforward to dye and exhibit wonderful resistance to wear due to a low constant of friction. Both amides have a high melting temperature (500 - 540 K) and glass transition temperature reports in excellent mechanical properties at elevated temperatures. For example, the heat rebound temperature of PA-6, 6 is usually between 180- 240°C that exceeds those of polycarbonate and polyester. They also have excellent resistance to fungi, oils, bases, etc. The main limitation is that the strong wet sensitivity water acts as a plasticizer and therefore the ensuring changes in mechanical properties. For example, the tensile strength of moist polyamide is 50% below that of dry polyamide. Another important polyamide is Nylon 6,12. It is less hydrophilic than Nylons 6,6 and 6 due to the larger range of chemical group of methylene within the compound backbone. For this reason, it has better dimensional
Cellulose is an abundant polysaccharide consisting of a β-1, 4 linkage of D-glucose [1,3]. There is an array of applications for cellulose, including, but not limited to: biofuels, reinforcement agents, thickeners, dietary fiber, and even wound care. As of late, cellulose, as a waste product, has been in high demand as a reinforcement agent in synthetic, petroleum-based polymer matrices (petroleum based plastics) [3]. Cellulose I has good flexibility, it is abundant in nature and also biodegradable. Because of its fiber- like structure, it has been compared to carbon nanotubes (CNT’s) [3].
Polymer means any of various chemical compounds made of smaller identical molecules called monomers linked together. Some polymers, like cellulose, occur naturally. Polymers have extremely high molecular weights, and made-up of many of the tissues of organisms, and have various uses in industries. The process by which molecules are linked together to form polymers is called polymerization (The American Heritage Science Dictionary, 2005). Polymeric compound is a compound made of many smaller molecules such as cellulose, chitin, soy protein, casein and many more. Polymeric is an organic giant molecule and most of the compound is non-crystalline.
My main aim during my undergraduate studies was to get an overview of the various fields in chemical engineering and identify a field of interest in which I could pursue my research career. Because of their vast applications, Materials & Polymer Sciences, in general, have attracted m...