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This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. August Learn how and when to remove this template message On a microscopic scale, relaxed rubber is a disorganized cluster of erratically changing wrinkled chains.
In stretched rubber, the chains are almost linear. The restoring force is due to the preponderance of wrinkled Reaction paper in natural science over more linear ones. For the quantitative treatment see ideal chainfor more examples see entropic force.
Cooling below the glass transition temperature permits local conformational changes but a reordering is practically impossible because of the larger energy barrier for the concerted movement of longer chains. The parallel chains of stretched rubber are susceptible to crystallization.
This takes some time because turns of twisted chains have to move out of the way of the growing crystallites. Crystallization has occurred, for example, when, after days, an inflated toy balloon is found withered at a relatively large remaining volume. Where it is touched, it shrinks because the temperature of the hand is enough to melt the crystals.
Vulcanization of rubber creates di- and polysulfide bonds between chains, which limits the degrees of freedom and results in chains that tighten more quickly for a given strain, thereby increasing the elastic force constant and making the rubber harder and less extensible.
Malodour[ edit ] Raw rubber storage depots and rubber processing can produce malodour that is serious enough to become a source of complaints and protest to those living in the vicinity.
These impurities break down during storage or thermal degradation and produce volatile organic compounds. This produces malodourous hydrogen sulphide. Synthetic cis-polyisoprene and natural cis-polyisoprene are derived from different precursors, isopentenyl pyrophosphate and isoprene.
Latex is the polymer cis-1,4-polyisoprene — with a molecular weight ofto 1, daltons. Polyisoprene can also be created synthetically, producing what is sometimes referred to as "synthetic natural rubber", but the synthetic and natural routes are different.
Natural rubber is an elastomer and a thermoplastic. Once the rubber is vulcanized, it is a thermoset. Most rubber in everyday use is vulcanized to a point where it shares properties of both; i.
The final properties of a rubber item depend not just on the polymer, but also on modifiers and fillers, such as carbon blackfacticewhiting and others.
Biosynthesis[ edit ] Rubber particles are formed in the cytoplasm of specialized latex-producing cells called laticifers within rubber plants. The membrane allows biosynthetic proteins to be sequestered at the surface of the growing rubber particle, which allows new monomeric units to be added from outside the biomembrane, but within the lacticifer.
The rubber particle is an enzymatically active entity that contains three layers of material, the rubber particle, a biomembrane and free monomeric units.
The biomembrane is held tightly to the rubber core due to the high negative charge along the double bonds of the rubber polymer backbone. The monomer adds to the pyrophosphate end of the growing polymer.
The reaction produces a cis polymer. The initiation step is catalyzed by prenyltransferasewhich converts three monomers of isopentenyl pyrophosphate into farnesyl pyrophosphate. The required isopentenyl pyrophosphate is obtained from the mevalonate pathway, which derives from acetyl-CoA in the cytosol.Reversible reactions and dynamic equilibrium (AQA GCSE Chemistry paper 2, Topic 6 "The rate and extent of chemical change").
Topic 6 The rate and extent of chemical change QUIZ (AQA GCSE Chemistry). Reversible reactions. Know that in some chemical reactions, the products of the reaction can react to produce the original reactants. Organic matter preservation is central to understanding biological potential on Mars through time.
Whether it holds a record of ancient life, is the food for extant life, or has existed in the absence of life, organic matter in martian materials holds chemical clues to planetary conditions and processes.
The Bend+Libration Combination Band Is an Intrinsic, Collective, and Strongly Solute-Dependent Reporter on the Hydrogen Bonding Network of Liquid Water. Field Trip 2 Reaction Paper: National Museum of Natural History On February 12, I travelled to the National Museum of Natural History with some of my fellow members of the Science and Global change scholars group.
At least one field trip is The National Museum of Natural History displays a multitude of information relating to. In college, most chemistry classes were focused on creating chemical reactions.
We were constantly challenged to figure out what reaction would happen when you mix chemicals together. A reaction paper in science(global warming) 1. A REACTION PAPER IN GLOBAL WARMING SUBMITTED BY: ANDREI DYON PAGSOLINGAN SUBMITTED TO: MR.