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NaturalRubber NR. (Hevea, rubber, natural cis-polyisoprene)

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RUBBER Natural Rubber NR. (Hevea, rubber, natural cis-polyisoprene) (slide 1) I'm going to talk to you about rubber, I'll talk about natural rubber first and then go on to talk about the way in which its natural state can be modified and manipulated so its advantageous properties can be used. (slide 2) Natural rubber is an excellent engineering material and is used as the main material in many everyday items the most prevalent being car tires which I'll discuss later also. (slide 3) Natural rubber is obtained from the milky white fluid called latex, found in many plants however synthetic rubbers are produced from unsaturated hydrocarbons (basically this means that there are carbon atoms in the rubber molecule that have a potential to be bonded to more hydrogen. Latex is a milky fluid found in specialized cells, called lactiferous cells. To gather the latex from plantation trees, a diagonal cut angled downward is made through the bark; this cut extends one-third of the circumference of the trunk. ...read more.


So that makes quite an interesting material chemically. I'll talk to you now a bit about natural rubber's advantageous physical properties. One of which is its long fatigue life, due to this it is commonly first choice for spring applications as it can be stretched compressed and distorted many times before becoming deformed. It also has a high strength without the need for reinforcing fillers like many other polymers- (Strength in this instance being an indication of its yield stress, which just to refresh your memory is the stress at the point when the material has reached its elastic limit.) It can also be compounded to give a wide range of hardness. It has a very good low temperature flexibility which means its form can be manipulated easily without needing to be heated, to think of a commonplace example 'rubber gloves need to be misshapen at room temperature without becoming permanently deformed. (slide 4) And now for synthetic rubbers. ...read more.


Other automobile parts, hose electrical insulation and footwear are normally made up of ethylene-propylene rubbers (RPDM) due to their high resistance to weathering and sunlight. (slide 5) Some synthetic materials have been developed to replace rubber. Urethane elastomers are called spandex and they consist of urethane blocks and polyether the urethane blocks give strength and heat resistance, the polyester and polyether blocks provide elasticity; they are the most versatile elastomer family because of their hardness, strength, oil resistance, and aging characteristics. Other uses range from airplane wheels to seat cushions. Other synthetics are highly oil-resistant, but their high cost limits their use. Silicone rubbers are organic derivatives of inorganic polymers, they are very stable and flexible. Over natural rubber: better aging and weathering, more resistance to oil, solvents, oxygen, ozone, and certain chemicals, and resilience over a wider temperature range. The advantages of natural rubber are less build-up of heat from flexing and greater resistance to tearing when hot. So basically although rubber in its natural state has many physical properties that make it a useful material we can modify and manipulate this natural material to make high performing compounds that can be found in everyday use. ...read more.

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