|
Thermosetting Plastics
In materials science, a thermosetting polymer, often called a thermoset, is a polymer that is obtained by irreversibly hardening (" curing") a soft solid or viscous liquid prepolymer (resin). Curing is induced by heat or suitable radiation and may be promoted by high pressure, or mixing with a catalyst. Heat is not necessarily applied externally, but is often generated by the reaction of the resin with a curing agent (''catalyst'', ''hardener''). Curing results in chemical reactions that create extensive cross-linking between polymer chains to produce an infusible and insoluble polymer network. The starting material for making thermosets is usually malleable or liquid prior to curing, and is often designed to be molded into the final shape. It may also be used as an adhesive. Once hardened, a thermoset cannot be melted for reshaping, in contrast to thermoplastic polymers which are commonly produced and distributed in the form of pellets, and shaped into the final product form b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Structures Of Macromolecules
A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as organism, biological organisms, minerals and chemical substance, chemicals. Abstract structures include data structures in computer science and musical form. Types of structure include a hierarchy (a cascade of one-to-many relationships), a Complex network, network featuring many-to-many Link (geometry), links, or a lattice (order), lattice featuring connections between components that are neighbors in space. Load-bearing Buildings, aircraft, skeletons, Ant colony, anthills, beaver dams, bridges and salt domes are all examples of Structural load, load-bearing structures. The results of construction are divided into buildings and nonbuilding structure, non-building structures, and make up the infrastructure of a human society. Built str ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Injection Molding
Injection moulding (U.S. spelling: injection molding) is a manufacturing process for producing parts by injecting molten material into a mould, or mold. Injection moulding can be performed with a host of materials mainly including metals (for which the process is called die-casting), glasses, elastomers, confections, and most commonly thermoplastic and thermosetting polymers. Material for the part is fed into a heated barrel, mixed (using a helical screw), and injected into a mould cavity, where it cools and hardens to the configuration of the cavity. After a product is designed, usually by an industrial designer or an engineer, moulds are made by a mould-maker (or toolmaker) from metal, usually either steel or aluminium, and precision-machined to form the features of the desired part. Injection moulding is widely used for manufacturing a variety of parts, from the smallest components to entire body panels of cars. Advances in 3D printing technology, using photopolymers that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Melting
Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which increases the substance's temperature to the melting point. At the melting point, the ordering of ions or molecules in the solid breaks down to a less ordered state, and the solid "melts" to become a liquid. Substances in the molten state generally have reduced viscosity as the temperature increases. An exception to this principle is the element sulfur, whose viscosity increases in the range of 160 °C to 180 °C due to polymerization. Some organic compounds melt through mesophases, states of partial order between solid and liquid. First order phase transition From a thermodynamics point of view, at the melting point the change in Gibbs free energy ''∆G'' of the substances is zero, but there are non-zero changes in the enthalpy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied on various reference points and thermometric substances for definition. The most common scales are the Celsius scale with the unit symbol °C (formerly called ''centigrade''), the Fahrenheit scale (°F), and the Kelvin scale (K), the latter being used predominantly for scientific purposes. The kelvin is one of the seven base units in the International System of Units (SI). Absolute zero, i.e., zero kelvin or −273.15 °C, is the lowest point in the thermodynamic temperature scale. Experimentally, it can be approached very closely but not actually reached, as recognized in the third law of thermodynamics. It would be impossible to extract energy as heat from a body at that temperature. Temperature is important in all fields of natur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polybenzoxazines
Polybenzoxazines, also called benzoxazine resins, are cured polymerization products derived from benzoxazine monomers. Monomers Benzoxazines are bicyclic heterocyclic compounds containing one oxygen and one nitrogen atom in a doubly unsaturated six-member ring, specifically a 1,3-oxazine ring, fused with a benzene ring. The systematic IUPAC name of the prototypical unsubstituted monomer is 3,4-dihydro-3-phenyl-2''H''-1,3-benzoxazine. Benzoxazines are products of condensation between an amine, a phenol and formaldehyde, used to produce thermoset resins or thermosetting polymer. Because of the wide availability and low-cost of starting materials (amines, phenols and formaldehyde), as well as ease of preparation (one-pot reaction) diverse benzoxazines are available. Numerous research focus on the different curing temperature, and polymer properties, such as cross-linking, from benzoxazines derived from substituted phenols. Commercial benzoxazines by Huntsman are based on bisphenols: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Furan
Furan is a heterocyclic organic compound, consisting of a five-membered aromatic ring with four carbon atoms and one oxygen atom. Chemical compounds containing such rings are also referred to as furans. Furan is a colorless, flammable, highly volatile liquid with a boiling point close to room temperature. It is soluble in common organic solvents, including alcohol, ether, and acetone, and is slightly soluble in water. Its odor is "strong, ethereal; chloroform-like". It is toxic and may be carcinogenic in humans. Furan is used as a starting point for other speciality chemicals. History The name "furan" comes from the Latin ''furfur'', which means bran. ( Furfural is produced from bran.) The first furan derivative to be described was 2-furoic acid, by Carl Wilhelm Scheele in 1780. Another important derivative, furfural, was reported by Johann Wolfgang Döbereiner in 1831 and characterised nine years later by John Stenhouse. Furan itself was first prepared by Heinrich Lim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amino
In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group (these may respectively be called alkylamines and arylamines; amines in which both types of substituent are attached to one nitrogen atom may be called alkylarylamines). Important amines include amino acids, biogenic amines, trimethylamine, and aniline; Inorganic derivatives of ammonia are also called amines, such as monochloramine (). The substituent is called an amino group. Compounds with a nitrogen atom attached to a carbonyl group, thus having the structure , are called amides and have different chemical properties from amines. Classification of amines Amines can be classified according to the nature and number of substituents on nitrogen. Aliphatic amines contain only H and alkyl substituents. Aroma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phenol Formaldehyde Resin
Phenol formaldehyde resins (PF) or phenolic resins (also infrequently called phenoplasts) are synthetic polymers obtained by the reaction of phenol or substituted phenol with formaldehyde. Used as the basis for Bakelite, PFs were the first commercial synthetic resins (plastics). They have been widely used for the production of molded products including billiard balls, laboratory countertops, and as coatings and adhesives. They were at one time the primary material used for the production of circuit boards but have been largely replaced with epoxy resins and fiberglass cloth, as with fire-resistant FR-4 circuit board materials. There are two main production methods. One reacts phenol and formaldehyde directly to produce a thermosetting network polymer, while the other restricts the formaldehyde to produce a prepolymer known as novolac which can be moulded and then cured with the addition of more formaldehyde and heat.A. Gardziella, L.A. Pilato, A. Knop, Phenolic Resins: Chemistry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unsaturated Monomer
Unsaturated monomers are those having carbon–carbon double bonds. In general, the term " unsaturated" refers to the presence of one or more double (or triple) bonds and the ability to "saturate" the molecule by addition of H2. Some examples of unsaturated monomers include: acrylic acid, acrylamide, acryloyl chloride, and methyl methacrylate Methyl methacrylate (MMA) is an organic compound with the formula CH2=C(CH3)COOCH3. This colorless liquid, the methyl ester of methacrylic acid (MAA), is a monomer produced on a large scale for the production of poly(methyl methacrylate) (PMMA .... Research suggests that unsaturated monomers that are coordinatively complexed together may be important in the process of enantioselective cyclopropanation of synthetic fibers. References Polymer chemistry Monomers {{polymer-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vinyl Ester Resin
Vinyl ester resin, or often just vinyl ester, is a resin produced by the esterification of an epoxy resin with acrylic or methacrylic acids. The "vinyl" groups refer to these ester substituents, which are prone to polymerize and thus an inhibitor is usually added. The diester product is then dissolved in a reactive solvent, such as styrene, to approximately 35–45 percent content by weight. Polymerization is initiated by free radicals, which are generated by UV-irradiation or peroxides. 352px, Bis-GMA a typical "vinyl ester" derived from bisphenol A diglycidyl ether. This thermosetting polymer, thermoset material can be used as an alternative to polyester and epoxy materials as the thermoset polymer matrix in composite materials, where its characteristics, strengths, and bulk cost are intermediate between polyester and epoxy. Vinyl ester has lower resin viscosity (approx. 200 cps) than polyester (approx. 500cps) and epoxy (approx. 900cps). Uses In homebuilt airplanes, the Glas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crosslink
In chemistry and biology a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural polymers (such as proteins). In polymer chemistry "cross-linking" usually refers to the use of cross-links to promote a change in the polymers' physical properties. When "crosslinking" is used in the biological field, it refers to the use of a probe to link proteins together to check for protein–protein interactions, as well as other creative cross-linking methodologies. Although the term is used to refer to the "linking of polymer chains" for both sciences, the extent of crosslinking and specificities of the crosslinking agents vary greatly. As with all science, there are overlaps, and the following delineations are a starting point to understanding the subtleties. Polymer chemistry Crosslinking is the general term for the process of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rubber
Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and Indonesia are three of the leading rubber producers. Types of polyisoprene that are used as natural rubbers are classified as elastomers. Currently, rubber is harvested mainly in the form of the latex from the rubber tree (''Hevea brasiliensis'') or others. The latex is a sticky, milky and white colloid drawn off by making incisions in the bark and collecting the fluid in vessels in a process called "tapping". The latex then is refined into the rubber that is ready for commercial processing. In major areas, latex is allowed to coagulate in the collection cup. The coagulated lumps are collected and processed into dry forms for sale. Natural rubber is used extensively in many applications and products, either alone or in combination wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
