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98-462: Much polymer is used in the firearm to save on weight and cost, with a steel slide and barrel and aluminum internal grip frame. Since its initial market introduction, the PMR-30 has undergone several improvements due to problems with the early available design. The twist rate on the barrel rifling was increased to 1:11 to better stabilize bullets and reduce key-holing. A stronger, lightly textured polymer

196-459: A catalyst . Laboratory synthesis of biopolymers, especially of proteins , is an area of intensive research. There are three main classes of biopolymers: polysaccharides , polypeptides , and polynucleotides . In living cells, they may be synthesized by enzyme-mediated processes, such as the formation of DNA catalyzed by DNA polymerase . The synthesis of proteins involves multiple enzyme-mediated processes to transcribe genetic information from

294-441: A lower critical solution temperature phase transition (LCST), at which phase separation occurs with heating. In dilute solutions, the properties of the polymer are characterized by the interaction between the solvent and the polymer. In a good solvent, the polymer appears swollen and occupies a large volume. In this scenario, intermolecular forces between the solvent and monomer subunits dominate over intramolecular interactions. In

392-498: A bad solvent or poor solvent, intramolecular forces dominate and the chain contracts. In the theta solvent , or the state of the polymer solution where the value of the second virial coefficient becomes 0, the intermolecular polymer-solvent repulsion balances exactly the intramolecular monomer-monomer attraction. Under the theta condition (also called the Flory condition), the polymer behaves like an ideal random coil . The transition between

490-537: A coding system that represented long sequences of amino acids. This would allow for these sequences to be compared to try to find homologies . These codes can consist of either a one-letter code or a three-letter code. These codes make it easier and shorter to write down the amino acid sequences that make up proteins . The nucleotide bases are made up of purines ( adenine and guanine ) and pyrimidines ( cytosine and thymine or uracil ). These nucleotide bases make up DNA and RNA . These nucleotide base codes make

588-408: A degree of crystallinity approaching zero or one will tend to be transparent, while polymers with intermediate degrees of crystallinity will tend to be opaque due to light scattering by crystalline or glassy regions. For many polymers, crystallinity may also be associated with decreased transparency. The space occupied by a polymer molecule is generally expressed in terms of radius of gyration , which

686-587: A deviation from a simple linear chain. A branched polymer molecule is composed of a main chain with one or more substituent side chains or branches. Types of branched polymers include star polymers , comb polymers , polymer brushes , dendronized polymers , ladder polymers , and dendrimers . There exist also two-dimensional polymers (2DP) which are composed of topologically planar repeat units. A polymer's architecture affects many of its physical properties including solution viscosity, melt viscosity, solubility in various solvents, glass-transition temperature and

784-464: A flexible quality. Plasticizers are also put in some types of cling film to make the polymer more flexible. The attractive forces between polymer chains play a large part in determining the polymer's properties. Because polymer chains are so long, they have many such interchain interactions per molecule, amplifying the effect of these interactions on the polymer properties in comparison to attractions between conventional molecules. Different side groups on

882-479: A given application, the properties of a polymer can be tuned or enhanced by combination with other materials, as in composites . Their application allows to save energy (lighter cars and planes, thermally insulated buildings), protect food and drinking water (packaging), save land and lower use of fertilizers (synthetic fibres), preserve other materials (coatings), protect and save lives (hygiene, medical applications). A representative, non-exhaustive list of applications

980-402: A high surface quality and are also highly transparent so that the laser properties are dominated by the laser dye used to dope the polymer matrix. These type of lasers, that also belong to the class of organic lasers , are known to yield very narrow linewidths which is useful for spectroscopy and analytical applications. An important optical parameter in the polymer used in laser applications

1078-1000: A member state of the Chemical Weapons Convention (CWC), are of concern to chemical scientists and engineers around the globe and we stand ready to support your mission of implementing the CWC." According to the CWC, "the use, stockpiling, distribution, development or storage of any chemical weapons is forbidden by any of the 192 state party signatories." IUPAC is governed by several committees that all have different responsibilities. The committees are as follows: Bureau, CHEMRAWN (Chem Research Applied to World Needs) Committee, Committee on Chemistry Education, Committee on Chemistry and Industry, Committee on Printed and Electronic Publications, Evaluation Committee, Executive Committee, Finance Committee, Interdivisional Committee on Terminology, Nomenclature and Symbols, Project Committee, and Pure and Applied Chemistry Editorial Advisory Board. Each committee

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1176-401: A polymer behaves as a continuous macroscopic material. They are classified as bulk properties, or intensive properties according to thermodynamics . The bulk properties of a polymer are those most often of end-use interest. These are the properties that dictate how the polymer actually behaves on a macroscopic scale. The tensile strength of a material quantifies how much elongating stress

1274-421: A polymer is its first and most important attribute. Polymer nomenclature is generally based upon the type of monomer residues comprising the polymer. A polymer which contains only a single type of repeat unit is known as a homopolymer , while a polymer containing two or more types of repeat units is known as a copolymer . A terpolymer is a copolymer which contains three types of repeat units. Polystyrene

1372-433: A polymeric material can be described at different length scales, from the sub-nm length scale up to the macroscopic one. There is in fact a hierarchy of structures, in which each stage provides the foundations for the next one. The starting point for the description of the structure of a polymer is the identity of its constituent monomers. Next, the microstructure essentially describes the arrangement of these monomers within

1470-536: A process called reptation in which each chain molecule is constrained by entanglements with neighboring chains to move within a virtual tube. The theory of reptation can explain polymer molecule dynamics and viscoelasticity . Depending on their chemical structures, polymers may be either semi-crystalline or amorphous. Semi-crystalline polymers can undergo crystallization and melting transitions , whereas amorphous polymers do not. In polymers, crystallization and melting do not suggest solid-liquid phase transitions, as in

1568-427: A result, they typically have lower melting temperatures than other polymers. When a polymer is dispersed or dissolved in a liquid, such as in commercial products like paints and glues, the chemical properties and molecular interactions influence how the solution flows and can even lead to self-assembly of the polymer into complex structures. When a polymer is applied as a coating, the chemical properties will influence

1666-456: A statistical distribution of chain lengths, the molecular weight is expressed in terms of weighted averages. The number-average molecular weight ( M n ) and weight-average molecular weight ( M w ) are most commonly reported. The ratio of these two values ( M w / M n ) is the dispersity ( Đ ), which is commonly used to express the width of the molecular weight distribution. The physical properties of polymer strongly depend on

1764-537: A tendency to form amorphous and semicrystalline structures rather than crystals . Polymers are studied in the fields of polymer science (which includes polymer chemistry and polymer physics ), biophysics and materials science and engineering . Historically, products arising from the linkage of repeating units by covalent chemical bonds have been the primary focus of polymer science. An emerging important area now focuses on supramolecular polymers formed by non-covalent links. Polyisoprene of latex rubber

1862-432: A variety of different but structurally related monomer residues; for example, polynucleotides such as DNA are composed of four types of nucleotide subunits. A polymer containing ionizable subunits (e.g., pendant carboxylic groups ) is known as a polyelectrolyte or ionomer , when the fraction of ionizable units is large or small respectively. The microstructure of a polymer (sometimes called configuration) relates to

1960-405: A wide-meshed cross-linking between the "main chains". Close-meshed crosslinking, on the other hand, leads to thermosets . Cross-links and branches are shown as red dots in the figures. Highly branched polymers are amorphous and the molecules in the solid interact randomly. An important microstructural feature of a polymer is its architecture and shape, which relates to the way branch points lead to

2058-421: Is cyclohexanol : Basic IUPAC inorganic nomenclature has two main parts: the cation and the anion . The cation is the name for the positively charged ion and the anion is the name for the negatively charged ion. An example of IUPAC nomenclature of inorganic chemistry is potassium chlorate (KClO 3 ): IUPAC also has a system for giving codes to identify amino acids and nucleotide bases. IUPAC needed

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2156-681: Is Germany. Germany's exclusion was a result of prejudice towards Germans by the Allied powers after World War I . Germany was finally admitted into IUPAC in 1929. However, Nazi Germany was removed from IUPAC during World War II . During World War II, IUPAC was affiliated with the Allied powers , but had little involvement during the war effort itself. After the war, East and West Germany were readmitted to IUPAC in 1973. Since World War II, IUPAC has been focused on standardizing nomenclature and methods in science without interruption. In 2016, IUPAC denounced

2254-644: Is a book about soil structures and the molecular processes that occur in soil. Structure and Surface Reactions of Soil Particles is aimed at any researcher researching soil or in the field of anthropology . It goes into depth on topics such as: fractal analysis of particle dimensions; computer modeling of the structure; reactivity of humics; applications of atomic force microscopy; and advanced instrumentation for analysis of soil particles. Metal Speciation and Bioavailability in Aquatic Systems, Series on Analytical and Physical Chemistry of Environmental Systems Vol. 3

2352-468: Is a book about the effect of trace metals on aquatic life. This book is considered a specialty book for researchers interested in observing the effect of trace metals in the water supply. This book includes techniques to assess how bioassays can be used to evaluate how an organism is affected by trace metals. Also, Metal Speciation and Bioavailability in Aquatic Systems, Series on Analytical and Physical Chemistry of Environmental Systems Vol. 3 looks at

2450-407: Is a book that delves into aerosol science. This book is aimed as a reference for graduate students and atmospheric researchers. Atmospheric Particles goes into depth on the properties of aerosols in the atmosphere and their effect. Topics covered in this book are: acid rain ; heavy metal pollution; global warming ; and photochemical smog. Atmospheric Particles also covers techniques to analyze

2548-463: Is a book that discusses techniques and devices to monitor aquatic systems and how new devices and techniques can be developed. This book emphasizes the future use of micro-analytical monitoring techniques and microtechnology . In Situ Monitoring of Aquatic Systems: Chemical Analysis and Speciation is aimed at researchers and laboratories that analyze aquatic systems such as rivers, lakes, and oceans. Structure and Surface Reactions of Soil Particles

2646-517: Is a book that gives background information on thermal analysis and calorimetry . Thermoanalytical and calorimetric techniques along with thermodynamic and kinetic properties are also discussed. Later volumes of this book discuss the applications and principles of these thermodynamic and kinetic methods. Equations of State for Fluids and Fluid Mixtures Part I is a book that gives up to date equations of state for fluids and fluid mixtures. This book covers all ways to develop equations of state. It gives

2744-479: Is a crucial physical parameter for polymer manufacturing, processing, and use. Below T g , molecular motions are frozen and polymers are brittle and glassy. Above T g , molecular motions are activated and polymers are rubbery and viscous. The glass-transition temperature may be engineered by altering the degree of branching or crosslinking in the polymer or by the addition of plasticizers . Whereas crystallization and melting are first-order phase transitions ,

2842-410: Is a long-chain n -alkane. There are also branched macromolecules with a main chain and side chains, in the case of polyethylene the side chains would be alkyl groups . In particular unbranched macromolecules can be in the solid state semi-crystalline, crystalline chain sections highlighted red in the figure below. While branched and unbranched polymers are usually thermoplastics, many elastomers have

2940-400: Is also commonly present in polymer backbones, such as those of polyethylene glycol , polysaccharides (in glycosidic bonds ), and DNA (in phosphodiester bonds ). Polymerization is the process of combining many small molecules known as monomers into a covalently bonded chain or network. During the polymerization process, some chemical groups may be lost from each monomer. This happens in

3038-586: Is also known for standardizing the atomic weights of the elements through one of its oldest standing committees, the Commission on Isotopic Abundances and Atomic Weights (CIAAW). The need for an international standard for chemistry was first addressed in 1860 by a committee headed by German scientist Friedrich August Kekulé von Stradonitz . This committee was the first international conference to create an international naming system for organic compounds . The ideas that were formulated at that conference evolved into

Kel-Tec PMR-30 - Misplaced Pages Continue

3136-512: Is an average distance from the center of mass of the chain to the chain itself. Alternatively, it may be expressed in terms of pervaded volume , which is the volume spanned by the polymer chain and scales with the cube of the radius of gyration. The simplest theoretical models for polymers in the molten, amorphous state are ideal chains . Polymer properties depend of their structure and they are divided into classes according to their physical bases. Many physical and chemical properties describe how

3234-481: Is an example of a natural polymer, and the polystyrene of styrofoam is an example of a synthetic polymer. In biological contexts, essentially all biological macromolecules —i.e., proteins (polyamides), nucleic acids (polynucleotides), and polysaccharides —are purely polymeric, or are composed in large part of polymeric components. The term "polymer" derives from Greek πολύς (polus)  'many, much' and μέρος (meros)  'part'. The term

3332-428: Is composed only of styrene -based repeat units, and is classified as a homopolymer. Polyethylene terephthalate , even though produced from two different monomers ( ethylene glycol and terephthalic acid ), is usually regarded as a homopolymer because only one type of repeat unit is formed. Ethylene-vinyl acetate contains more than one variety of repeat unit and is a copolymer. Some biological polymers are composed of

3430-409: Is defined, for small strains , as the ratio of rate of change of stress to strain. Like tensile strength, this is highly relevant in polymer applications involving the physical properties of polymers, such as rubber bands. The modulus is strongly dependent on temperature. Viscoelasticity describes a complex time-dependent elastic response, which will exhibit hysteresis in the stress-strain curve when

3528-552: Is given below. IUPAC The International Union of Pure and Applied Chemistry ( IUPAC / ˈ aɪ juː p æ k , ˈ juː -/ ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is a member of the International Science Council (ISC). IUPAC is registered in Zürich , Switzerland , and

3626-823: Is made up of members of different National Adhering Organizations from different countries. The steering committee hierarchy for IUPAC is as follows: Chemical Nomenclature and Structure Representation Division (Division VIII) Current officers of the Executive Committee : Scientists framed a systematic method for naming organic compounds based on their structures. Hence, the naming rules were formulated by IUPAC. IUPAC establishes rules for harmonized spelling of some chemicals to reduce variation among different local English-language variants. For example, they recommend " aluminium " rather than "aluminum", " sulfur " rather than "sulphur", and " caesium " rather than "cesium". IUPAC organic nomenclature has three basic parts:

3724-459: Is meant to be a compilation of other IUPAC works. The second edition of this book was published in 1997. This book made large changes to the first edition of the Compendium of Chemical Terminology . These changes included updated material and an expansion of the book to include over seven thousand terms. The second edition was the topic of an IUPAC XML project. This project made an XML version of

3822-474: Is meant to give an overview of a technique based on fractal geometry and the processes of environmental systems. This book gives ideas on how to use fractal geometry to compare and contrast different ecosystems . It also gives an overview of the knowledge needed to solve environmental problems. Finally, Biophysical Chemistry of Fractal Structures and Processes in Environmental Systems shows how to use

3920-485: Is now used for the frame. This eliminates drooping of the frame that created a large gap previously seen between the front of the frame and the barrel. This also gives the frame a less shiny appearance, and a less slick feel in the hand. More metal was added as reinforcement at the breech to completely cover the rim of a loaded cartridge, presumably for increased user safety in the event of a cartridge case head separation. Kel-Tec also offers an extended 5" threaded barrel for

4018-728: Is relatively well received as being useful for reviewing chemical toxicology. Macromolecular Symposia is a journal that publishes fourteen issues a year. This journal includes contributions to the macromolecular chemistry and physics field. The meetings of IUPAC are included in this journal along with the European Polymer Federation , the American Chemical Society , and the Society of Polymer Science in Japan. The Experimental Thermodynamics books series covers many topics in

Kel-Tec PMR-30 - Misplaced Pages Continue

4116-527: Is the Compendium of Analytical Nomenclature (the "Orange Book"; 1st edition 1978). This book was revised in 1987. The second edition has many revisions that come from reports on nomenclature between 1976 and 1984. In 1992, the second edition went through many different revisions, which led to the third edition. Pure and Applied Chemistry is the official monthly journal of IUPAC. This journal debuted in 1960. The goal statement for Pure and Applied Chemistry

4214-435: Is the change in refractive index with temperature also known as dn/dT. For the polymers mentioned here the (dn/dT) ~ −1.4 × 10 in units of K in the 297 ≤ T ≤ 337 K range. Most conventional polymers such as polyethylene are electrical insulators , but the development of polymers containing π-conjugated bonds has led to a wealth of polymer-based semiconductors , such as polythiophenes . This has led to many applications in

4312-563: Is the main constituent of wood and paper. Hemoglycin (previously termed hemolithin ) is a space polymer that is the first polymer of amino acids found in meteorites . The list of synthetic polymers , roughly in order of worldwide demand, includes polyethylene , polypropylene , polystyrene , polyvinyl chloride , synthetic rubber , phenol formaldehyde resin (or Bakelite ), neoprene , nylon , polyacrylonitrile , PVB , silicone , and many more. More than 330 million tons of these polymers are made every year (2015). Most commonly,

4410-769: Is the recognized world authority in developing standards for naming the chemical elements and compounds . Since its creation, IUPAC has been run by many different committees with different responsibilities. These committees run different projects which include standardizing nomenclature , finding ways to bring chemistry to the world, and publishing works. IUPAC is best known for its works standardizing nomenclature in chemistry, but IUPAC has publications in many science fields including chemistry, biology, and physics. Some important work IUPAC has done in these fields includes standardizing nucleotide base sequence code names; publishing books for environmental scientists, chemists, and physicists; and improving education in science. IUPAC

4508-443: Is to "publish highly topical and credible works at the forefront of all aspects of pure and applied chemistry." The journal itself is available by subscription, but older issues are available in the archive on IUPAC's website. Pure and Applied Chemistry was created as a central way to publish IUPAC endorsed articles. Before its creation, IUPAC did not have a quick, official way to distribute new chemistry information. Its creation

4606-420: The substituents , carbon chain length, and chemical affix. The substituents are any functional groups attached to the main carbon chain. The main carbon chain is the longest possible continuous chain. The chemical affix denotes what type of molecule it is. For example, the ending ane denotes a single bonded carbon chain, as in "hexane" ( C 6 H 14 ). Another example of IUPAC organic nomenclature

4704-542: The DNA to RNA and subsequently translate that information to synthesize the specified protein from amino acids . The protein may be modified further following translation in order to provide appropriate structure and functioning. There are other biopolymers such as rubber , suberin , melanin , and lignin . Naturally occurring polymers such as cotton , starch , and rubber were familiar materials for years before synthetic polymers such as polyethene and perspex appeared on

4802-539: The PMR-30 with an aluminum flash-hider to reduce the high amount of muzzle flash produced by escaping gases. A rifle variant, the CMR-30, is also available. In gun tests the KelTec PMR30 .22 WMR pistol gave an average velocity of 1,351 feet per second (412 m/s) from its 4.3 inch barrel. Polymer A polymer is a substance composed of macromolecules. A macromolecule is a molecule of high relative molecular mass,

4900-535: The Pacific Ocean are a result of reduced chlorophyll for phytoplankton production. It does this by reviewing information from research in the 1990s. This book goes into depth about: chemical speciation; analytical techniques; transformation of iron; how iron limits the development of high nutrient low chlorophyll areas in the Pacific Ocean . In Situ Monitoring of Aquatic Systems: Chemical Analysis and Speciation

4998-613: The Terrestrial Ecosystem gives techniques to analyze minerals, microorganisms, and organic components together. This book also has a large section positing why environmental scientists working in the specific fields of minerals, microorganisms, and organic components of soil should work together and how they should do so. The Biogeochemistry of Iron in Seawater is a book that describes how low concentrations of iron in Antarctica and

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5096-500: The Terrestrial Ecosystem is about how minerals, microorganisms, and organic components work together to affect terrestrial systems . This book identifies that there are many different techniques and theories about minerals, microorganisms, and organic components individually, but they are not often associated with each other. It further goes on to discuss how these components of soil work together to affect terrestrial life. Interactions Between Soil Particles and Microorganisms: Impact on

5194-477: The Thermodynamic Properties of Multiple Phases is a book that includes multiple techniques that are used to study multiple phases of pure component systems. Also included in this book are the measurement techniques to obtain activity coefficients , interfacial tension , and critical parameters . This book was written for researchers and graduate students as a reference source. Atmospheric Particles

5292-423: The Thermodynamic Properties of Single Phases is a book that gives an overview of techniques for measuring the thermodynamic quantities of single phases. It also goes into experimental techniques to test many different thermodynamic states precisely and accurately. Measurement of the Thermodynamic Properties of Single Phases was written for people interested in measuring thermodynamic properties. Measurement of

5390-441: The adhesion of the coating and how it interacts with external materials, such as superhydrophobic polymer coatings leading to water resistance. Overall the chemical properties of a polymer are important elements for designing new polymeric material products. Polymers such as PMMA and HEMA:MMA are used as matrices in the gain medium of solid-state dye lasers , also known as solid-state dye-doped polymer lasers. These polymers have

5488-912: The administrative office, known as the "IUPAC Secretariat", is in Research Triangle Park , North Carolina , United States . IUPAC's executive director heads this administrative office, currently Greta Heydenrych. IUPAC was established in 1919 as the successor of the International Congress of Applied Chemistry for the advancement of chemistry . Its members, the National Adhering Organizations, can be national chemistry societies , national academies of sciences , or other bodies representing chemists. There are fifty-four National Adhering Organizations and three Associate National Adhering Organizations. IUPAC's Inter-divisional Committee on Nomenclature and Symbols ( IUPAC nomenclature )

5586-704: The atmosphere and ways to take atmospheric samples. Environmental Colloids and Particles: Behaviour, Separation and Characterisation is a book that discusses environmental colloids and current information available on them. This book focuses on environmental colloids and particles in aquatic systems and soils. It also goes over techniques such as techniques for sampling environmental colloids, size fractionation, and how to characterize colloids and particles. Environmental Colloids and Particles: Behaviour, Separation and Characterisation also delves into how these colloids and particles interact. Biophysical Chemistry of Fractal Structures and Processes in Environmental Systems

5684-434: The backbone in a variety of ways. A copolymer containing a controlled arrangement of monomers is called a sequence-controlled polymer . Alternating, periodic and block copolymers are simple examples of sequence-controlled polymers . Tacticity describes the relative stereochemistry of chiral centers in neighboring structural units within a macromolecule. There are three types of tacticity: isotactic (all substituents on

5782-542: The book that includes over seven thousand terms. The XML version of the book includes an open editing policy, which allows users to add excerpts of the written version. IUPAC and UNESCO were the lead organizations coordinating events for the International Year of Chemistry , which took place in 2011. The International Year of Chemistry was originally proposed by IUPAC at the general assembly in Turin , Italy. This motion

5880-421: The case of water or other molecular fluids. Instead, crystallization and melting refer to the phase transitions between two solid states ( i.e. , semi-crystalline and amorphous). Crystallization occurs above the glass-transition temperature ( T g ) and below the melting temperature ( T m ). All polymers (amorphous or semi-crystalline) go through glass transitions . The glass-transition temperature ( T g )

5978-469: The continuously linked backbone of a polymer used for the preparation of plastics consists mainly of carbon atoms. A simple example is polyethylene ('polythene' in British English), whose repeat unit or monomer is ethylene . Many other structures do exist; for example, elements such as silicon form familiar materials such as silicones, examples being Silly Putty and waterproof plumbing sealant. Oxygen

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6076-536: The degree of crystallinity may be expressed in terms of a weight fraction or volume fraction of crystalline material. Few synthetic polymers are entirely crystalline. The crystallinity of polymers is characterized by their degree of crystallinity, ranging from zero for a completely non-crystalline polymer to one for a theoretical completely crystalline polymer. Polymers with microcrystalline regions are generally tougher (can be bent more without breaking) and more impact-resistant than totally amorphous polymers. Polymers with

6174-400: The driving force for mixing is usually entropy , not interaction energy. In other words, miscible materials usually form a solution not because their interaction with each other is more favorable than their self-interaction, but because of an increase in entropy and hence free energy associated with increasing the amount of volume available to each component. This increase in entropy scales with

6272-470: The effect of an equipment setup on an experiment. Fundamental Toxicology is a textbook that proposes a curriculum for toxicology courses. Fundamental Toxicology is based on the book Fundamental Toxicology for Chemists . Fundamental Toxicology is enhanced through many revisions and updates. New information added in the revisions includes: risk assessment and management; reproductive toxicology; behavioral toxicology; and ecotoxicology . This book

6370-417: The field of organic electronics . Nowadays, synthetic polymers are used in almost all walks of life. Modern society would look very different without them. The spreading of polymer use is connected to their unique properties: low density, low cost, good thermal/electrical insulation properties, high resistance to corrosion, low-energy demanding polymer manufacture and facile processing into final products. For

6468-513: The fields of thermodynamics. Measurement of the Transport Properties of Fluids is a book that is published by Blackwell Science . The topics that are included in this book are low and high-temperature measurements, secondary coefficients, diffusion coefficients , light scattering , transient methods for thermal conductivity , methods for thermal conductivity, falling-body viscometers, and vibrating viscometers . Solution Calorimetry

6566-530: The fractal approach to understand the reactivity of flocs , sediments, soils, microorganisms, and humic substances. Interactions Between Soil Particles and Microorganisms: Impact on the Terrestrial Ecosystem is meant to be read by chemists and biologists that study environmental systems. Also, this book should be used as a reference for earth scientists, environmental geologists, environmental engineers, and professionals in microbiology and ecology. Interactions Between Soil Particles and Microorganisms: Impact on

6664-527: The free energy of mixing for polymer solutions and thereby making solvation less favorable, and thereby making the availability of concentrated solutions of polymers far rarer than those of small molecules. Furthermore, the phase behavior of polymer solutions and mixtures is more complex than that of small molecule mixtures. Whereas most small molecule solutions exhibit only an upper critical solution temperature phase transition (UCST), at which phase separation occurs with cooling, polymer mixtures commonly exhibit

6762-467: The genome of an organism much smaller and easier to read. The codes for amino acids (24 amino acids and three special codes) are: Principles and Practices of Method Validation is a book entailing methods of validating and analyzing many analytes taken from a single aliquot . Also, this book goes over techniques for analyzing many samples at once. Some methods discussed include chromatographic methods, estimation of effects, matrix-induced effects, and

6860-401: The glass transition is not. The glass transition shares features of second-order phase transitions (such as discontinuity in the heat capacity, as shown in the figure), but it is generally not considered a thermodynamic transition between equilibrium states. In general, polymeric mixtures are far less miscible than mixtures of small molecule materials. This effect results from the fact that

6958-415: The individual chains more strongly in position and resist deformations and matrix breakup, both at higher stresses and higher temperatures. Copolymers are classified either as statistical copolymers, alternating copolymers, block copolymers, graft copolymers or gradient copolymers. In the schematic figure below, Ⓐ and Ⓑ symbolize the two repeat units . Monomers within a copolymer may be organized along

7056-451: The latter case, increasing the polymer chain length 10-fold would increase the viscosity over 1000 times. Increasing chain length furthermore tends to decrease chain mobility, increase strength and toughness, and increase the glass-transition temperature (T g ). This is a result of the increase in chain interactions such as van der Waals attractions and entanglements that come with increased chain length. These interactions tend to fix

7154-436: The length (or equivalently, the molecular weight) of the polymer chain. One important example of the physical consequences of the molecular weight is the scaling of the viscosity (resistance to flow) in the melt. The influence of the weight-average molecular weight ( M w {\displaystyle M_{w}} ) on the melt viscosity ( η {\displaystyle \eta } ) depends on whether

7252-742: The limitations of the use of bioassays to observe the effects of trace metals on organisms. Physicochemical Kinetics and Transport at Biointerfaces is a book created to aid environmental scientists in fieldwork. The book gives an overview of chemical mechanisms, transport, kinetics, and interactions that occur in environmental systems . Physicochemical Kinetics and Transport at Biointerfaces continues from where Metal Speciation and Bioavailability in Aquatic Systems leaves off. IUPAC color code their books in order to make each publication distinguishable. One extensive book on almost all nomenclature written (IUPAC nomenclature of organic chemistry and IUPAC nomenclature of inorganic chemistry) by IUPAC committee

7350-417: The load is removed. Dynamic mechanical analysis or DMA measures this complex modulus by oscillating the load and measuring the resulting strain as a function of time. Transport properties such as diffusivity describe how rapidly molecules move through the polymer matrix. These are very important in many applications of polymers for films and membranes. The movement of individual macromolecules occurs by

7448-436: The market. Many commercially important polymers are synthesized by chemical modification of naturally occurring polymers. Prominent examples include the reaction of nitric acid and cellulose to form nitrocellulose and the formation of vulcanized rubber by heating natural rubber in the presence of sulfur . Ways in which polymers can be modified include oxidation , cross-linking , and end-capping . The structure of

7546-413: The material will endure before failure. This is very important in applications that rely upon a polymer's physical strength or durability. For example, a rubber band with a higher tensile strength will hold a greater weight before snapping. In general, tensile strength increases with polymer chain length and crosslinking of polymer chains. Young's modulus quantifies the elasticity of the polymer. It

7644-444: The number of particles (or moles) being mixed. Since polymeric molecules are much larger and hence generally have much higher specific volumes than small molecules, the number of molecules involved in a polymeric mixture is far smaller than the number in a small molecule mixture of equal volume. The energetics of mixing, on the other hand, is comparable on a per volume basis for polymeric and small molecule mixtures. This tends to increase

7742-441: The official IUPAC nomenclature of organic chemistry . IUPAC stands as a legacy of this meeting, making it one of the most important historical international collaborations of chemistry societies . Since this time, IUPAC has been the official organization held with the responsibility of updating and maintaining official organic nomenclature . IUPAC as such was established in 1919. One notable country excluded from this early IUPAC

7840-713: The partially negatively charged oxygen atoms in C=O groups on another. These strong hydrogen bonds, for example, result in the high tensile strength and melting point of polymers containing urethane or urea linkages. Polyesters have dipole-dipole bonding between the oxygen atoms in C=O groups and the hydrogen atoms in H-C groups. Dipole bonding is not as strong as hydrogen bonding, so a polyester's melting point and strength are lower than Kevlar 's ( Twaron ), but polyesters have greater flexibility. Polymers with non-polar units such as polyethylene interact only through weak Van der Waals forces . As

7938-422: The physical arrangement of monomer residues along the backbone of the chain. These are the elements of polymer structure that require the breaking of a covalent bond in order to change. Various polymer structures can be produced depending on the monomers and reaction conditions: A polymer may consist of linear macromolecules containing each only one unbranched chain. In the case of unbranched polyethylene, this chain

8036-399: The polymer and create gaps between polymer chains for greater mobility and fewer interchain interactions. A good example of the action of plasticizers is related to polyvinylchlorides or PVCs. A uPVC, or unplasticized polyvinylchloride, is used for things such as pipes. A pipe has no plasticizers in it, because it needs to remain strong and heat-resistant. Plasticized PVC is used in clothing for

8134-426: The polymer at the scale of a single chain. The microstructure determines the possibility for the polymer to form phases with different arrangements, for example through crystallization , the glass transition or microphase separation . These features play a major role in determining the physical and chemical properties of a polymer. The identity of the repeat units (monomer residues, also known as "mers") comprising

8232-540: The polymer can lend the polymer to ionic bonding or hydrogen bonding between its own chains. These stronger forces typically result in higher tensile strength and higher crystalline melting points. The intermolecular forces in polymers can be affected by dipoles in the monomer units. Polymers containing amide or carbonyl groups can form hydrogen bonds between adjacent chains; the partially positively charged hydrogen atoms in N-H groups of one chain are strongly attracted to

8330-403: The polymer is above or below the onset of entanglements . Below the entanglement molecular weight , η ∼ M w 1 {\displaystyle \eta \sim {M_{w}}^{1}} , whereas above the entanglement molecular weight, η ∼ M w 3.4 {\displaystyle \eta \sim {M_{w}}^{3.4}} . In

8428-583: The polymerization of PET polyester . The monomers are terephthalic acid (HOOC—C 6 H 4 —COOH) and ethylene glycol (HO—CH 2 —CH 2 —OH) but the repeating unit is —OC—C 6 H 4 —COO—CH 2 —CH 2 —O—, which corresponds to the combination of the two monomers with the loss of two water molecules. The distinct piece of each monomer that is incorporated into the polymer is known as a repeat unit or monomer residue. Synthetic methods are generally divided into two categories, step-growth polymerization and chain polymerization . The essential difference between

8526-437: The same side), atactic (random placement of substituents), and syndiotactic (alternating placement of substituents). Polymer morphology generally describes the arrangement and microscale ordering of polymer chains in space. The macroscopic physical properties of a polymer are related to the interactions between the polymer chains. When applied to polymers, the term crystalline has a somewhat ambiguous usage. In some cases,

8624-512: The size of individual polymer coils in solution. A variety of techniques may be employed for the synthesis of a polymeric material with a range of architectures, for example living polymerization . A common means of expressing the length of a chain is the degree of polymerization , which quantifies the number of monomers incorporated into the chain. As with other molecules, a polymer's size may also be expressed in terms of molecular weight . Since synthetic polymerization techniques typically yield

8722-448: The states is known as a coil–globule transition . Inclusion of plasticizers tends to lower T g and increase polymer flexibility. Addition of the plasticizer will also modify dependence of the glass-transition temperature T g on the cooling rate. The mobility of the chain can further change if the molecules of plasticizer give rise to hydrogen bonding formation. Plasticizers are generally small molecules that are chemically similar to

8820-479: The strengths and weaknesses of each equation. Some equations discussed include: virial equation of state cubic equations; generalized Van der Waals equations ; integral equations; perturbation theory; and stating and mixing rules. Other things that Equations of State for Fluids and Fluid Mixtures Part I goes over are: associating fluids, polymer systems, polydisperse fluids, self-assembled systems, ionic fluids, and fluids near their critical points. Measurement of

8918-1024: The structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass. A polymer ( / ˈ p ɒ l ɪ m ər / ) is a substance or material that consists of very large molecules, or macromolecules , that are constituted by many repeating subunits derived from one or more species of monomers . Due to their broad spectrum of properties, both synthetic and natural polymers play essential and ubiquitous roles in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers . Their consequently large molecular mass , relative to small molecule compounds , produces unique physical properties including toughness , high elasticity , viscoelasticity , and

9016-686: The term crystalline finds identical usage to that used in conventional crystallography . For example, the structure of a crystalline protein or polynucleotide, such as a sample prepared for x-ray crystallography , may be defined in terms of a conventional unit cell composed of one or more polymer molecules with cell dimensions of hundreds of angstroms or more. A synthetic polymer may be loosely described as crystalline if it contains regions of three-dimensional ordering on atomic (rather than macromolecular) length scales, usually arising from intramolecular folding or stacking of adjacent chains. Synthetic polymers may consist of both crystalline and amorphous regions;

9114-555: The two is that in chain polymerization, monomers are added to the chain one at a time only, such as in polystyrene , whereas in step-growth polymerization chains of monomers may combine with one another directly, such as in polyester . Step-growth polymerization can be divided into polycondensation , in which low-molar-mass by-product is formed in every reaction step, and polyaddition . Newer methods, such as plasma polymerization do not fit neatly into either category. Synthetic polymerization reactions may be carried out with or without

9212-591: The use of chlorine as a chemical weapon . The organization pointed out their concerns in a letter to Ahmet Üzümcü, the director of the Organisation for the Prohibition of Chemical Weapons (OPCW), in regards to the practice of utilizing chlorine for weapon usage in Syria among other locations. The letter stated, "Our organizations deplore the use of chlorine in this manner. The indiscriminate attacks, possibly carried out by

9310-521: Was adopted by UNESCO at a meeting in 2008. The main objectives of the International Year of Chemistry were to increase public appreciation of chemistry and gain more interest in the world of chemistry . This event is also being held to encourage young people to get involved and contribute to chemistry. A further reason for this event being held is to honour how chemistry has made improvements to everyone's way of life. IUPAC Presidents are elected by

9408-605: Was coined in 1833 by Jöns Jacob Berzelius , though with a definition distinct from the modern IUPAC definition. The modern concept of polymers as covalently bonded macromolecular structures was proposed in 1920 by Hermann Staudinger , who spent the next decade finding experimental evidence for this hypothesis. Polymers are of two types: naturally occurring and synthetic or man made . Natural polymeric materials such as hemp , shellac , amber , wool , silk , and natural rubber have been used for centuries. A variety of other natural polymers exist, such as cellulose , which

9506-506: Was decided that the journal would reprint old journal editions to keep all chemistry knowledge available. The Compendium of Chemical Terminology , also known as the "Gold Book", was originally worked on by Victor Gold . This book is a collection of names and terms already discussed in Pure and Applied Chemistry . The Compendium of Chemical Terminology was first published in 1987. The first edition of this book contains no original material, but

9604-522: Was first suggested at the Paris IUPAC Meeting of 1957. During this meeting the commercial publisher of the journal was discussed and decided on. In 1959, the IUPAC Pure and Applied Chemistry Editorial Advisory Board was created and put in charge of the journal. The idea of one journal being a definitive place for a vast amount of chemistry was difficult for the committee to grasp at first. However, it

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