Acrylic special

UV-curing adhesives are available in a number of chemical systems, most of which are polymer based. These systems include acrylics and acrylates, epoxies, polyurethanes, polyesters, silicones, and vinyl and vinyl esters. The most common UV-curable adhesive is the acrylics. Specially modified acrylic and epoxy adhesives can be cured rapidly by UV radiation. In the case of epoxy adhesives, the adhesives can be pre-irradiated after application to the substrate before closing the bond line. These adhesive systems are offered by most major suppliers. ... 

An important nitrile is acrylonitrile H2C=CHCN It is prepared industrially from propene ammonia and oxygen m the presence of a special catalyst Polymers of acryl omtrile have many applications the most prominent being their use m the preparation of acrylic fibers... 

Process. Any standard precursor material can be used, but the preferred material is wet spun Courtaulds special acrylic fiber (SAF), oxidized by RK Carbon Fibers Co. to form 6K Panox B oxidized polyacrylonitrile (PAN) fiber (OPF). This OPF is treated ia a nitrogen atmosphere at 450—750°C, preferably 525—595°C, to give fibers having between 69—70% C, 19% N density less than 2.5 g/mL and a specific resistivity under 10 ° ohm-cm. If crimp is desired, the fibers are first knit iato a sock before heat treating and then de-knit. Controlled carbonization of precursor filaments results ia a linear Dow fiber (LDF), whereas controlled carbonization of knit precursor fibers results ia a curly carbonaceous fiber (EDF). At higher carbonizing temperatures of 1000—1400°C the fibers become electrically conductive (22). 

The anthraquinones are useful in acrylics and are compatible with polystyrene and ceUulosics. Solvent Red 111 has a special affinity for poly(methyl methacrylate) as the red in automobile taillights exposure for a year in Florida or Arizona produces only a very slight darkening. Acid types are usehil for phenohcs (see Dyes, anthraquinone). 

Acrylics processed by compression-molding techniques give dentures as satisfactory and dimensionally stable as the estimated 5% of the dentures made with special resins and elaborate processing equipment (208). Promising fiber-reinforced dentures have been reported (209—212). 

Wool—Acrylic Fibers. This blend is being used for iadustrial and hand knitting yams. The acryHc fiber is aesthetically similar to wool, iacreases the strength of the yam, and adds bulk to the goods. Special precautions are necessary siace the two fibers are colored with dyes of opposite ionic type. Coprecipitation is prevented with the use of an antiprecipitant. Usually, level dyeing acid dyes are used for the wool portion in combination with the cationic dyes for acryHc fiber. 

The demands on insulating materials in soil and fresh water are relatively low. Anodically evolved oxygen makes the use of aging-resistant insulating materials necessary. These consist of special types of rubber (neoprene) and stabilized plastics of polyethylene, and polyvinylchloride, as well as cast resins such as acrylate, epoxy, polyester resin and many others. 

In addition to acting as impact modifiers a number of polymeric additives may be considered as processing aids. These have similar chemical constitutions to the impact modifiers and include ABS, MBS, chlorinated polyethylene, acrylate-methacrylate copolymers and EVA-PVC grafts. Such materials are more compatible with the PVC and are primarily included to ensure more uniform flow and hence improve surface finish. They may also increase gelation rates. In the case of the compatible MBS polymers they have the special function already mentioned of balancing the refractive indices of the continuous and disperse phases of impact-modified compound. 

In addition to poly(methyl methacrylate) plastics and polyacrylonitrile fibres, acrylic polymers find widespread use. First introduced in 1946, acrylic rubbers have become established as important special purpose rubbers with a useful combination of oil and heat resistance. Acrylic paints have become widely accepted particularly in the car industry whilst very interesting reactive adhesives, including the well-known super-glues are also made from acrylic polymers. 

Minimize stocks and segregate from other chemicals and work areas. Where appropriate, keep samples dilute or damp and avoid formation of large crystals when practicable. Add stabilizers if possible, e.g. to vinyl monomers. Store in specially-designed, well-labelled containers in No Smoking areas, preferably in several small containers rather than one large container. Where relevant, store in dark and under chilled conditions, except where this causes pure material to separate from stabilizer (e.g. acrylic acid). 

Perhaps a more specialized case of using plasticizers in acrylic formulations can be found in drug delivery patches. Here, plasticizing additives called excipients... 

In formulating adhesives, it is desirable to use materials with low cost. For specialty adhesives such as the acrylics, it is preferred to use commodity chemicals with a range of other uses. Minor components such as reactive rubbers, functional monomers and some additives are specially synthesized for acrylics, but these are expensive due to low volume. 

Standard-grade PSAs are usually made from styrene-butadiene rubber (SBR), natural rubber, or blends thereof in solution. In addition to rubbers, polyacrylates, polymethylacrylates, polyfvinyl ethers), polychloroprene, and polyisobutenes are often components of the system ([198], pp. 25-39). These are often modified with phenolic resins, or resins based on rosin esters, coumarones, or hydrocarbons. Phenolic resins improve temperature resistance, solvent resistance, and cohesive strength of PSA ([196], pp. 276-278). Antioxidants and tackifiers are also essential components. Sometimes the tackifier will be a lower molecular weight component of the high polymer system. The phenolic resins may be standard resoles, alkyl phenolics, or terpene-phenolic systems ([198], pp. 25-39 and 80-81). Pressure-sensitive dispersions are normally comprised of special acrylic ester copolymers with resin modifiers. The high polymer base used determines adhesive and cohesive properties of the PSA. 

The ophthalmic applications for plastics lenses include contact lenses which are now made of acrylic plastics. Another material for this application is a special hydrophillic acrylic polymer used in soft contact lenses. These lenses are much more comfortable than rigid contact lenses. 

Composite proplnts, which are used almost entirely in rocket propulsion, normally contain a solid phase oxidizer combined with a polymeric fuel binder with a -CH2—CH2— structure. Practically speaking AP is the only oxidizer which has achieved high volume production, although ammonium nitrate (AN) has limited special uses such as in gas generators. Other oxidizers which have been studied more or less as curiosities include hydrazinium nitrate, nitronium perchlorate, lithium perchlorate, lithium nitrate, potassium perchlorate and others. Among binders, the most used are polyurethanes, polybutadiene/acrylonitrile/acrylic acid terpolymers and hydroxy-terminated polybutadienes... 

A considerable viscosity increase in copolymers of tributylstannyl methacrylate with methyl methacrylate, butyl acrylate and styrene upon prolongated storage has been observed and special agents to eliminate this effect have been proposed 108). It is likely that the destruction of intermolecular coordination complexes formed by involvement of tin and carbonyl groups in comonomer units takes place in this case. 

Acrylic fibres can also be brightened during manufacture by gel application during the wet spinning process. Special FBAs have not been developed for this purpose. Products such as the pyrazoline sulphone 11.50 and the benzofuranyl-benzimidazole 11.55 are suitable for this application. 

The controlled polymerization of (meth)acrylates was achieved by anionic polymerization. However, special bulky initiators and very low temperatures (- 78 °C) must be employed in order to avoid side reactions. An alternative procedure for achieving the same results by conducting the polymerization at room temperature was proposed by Webster and Sogah [84], The technique, called group transfer polymerization, involves a catalyzed silicon-mediated sequential Michael addition of a, /f-unsaluralcd esters using silyl ketene acetals as initiators. Nucleophilic (anionic) or Lewis acid catalysts are necessary for the polymerization. Nucleophilic catalysts activate the initiator and are usually employed for the polymerization of methacrylates, whereas Lewis acids activate the monomer and are more suitable for the polymerization of acrylates [85,86]. 

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