Copolymer balances

Octylacrylamide/acrylates/butylaminoethyl methacrylate copolymer Balance CR, Balance Extra, Balance N Balance 0/55. See Acrylates copolymer Ballotini A, Ballotini AA, Ballotini AAA Ballotini AH. See Glass Balm. See Balm mint (Melissa officinalis) Balmix . See 1,1,1-Trichloroethane Balm leaves extract. See Balm mint (Melissa officinalis) extract... 

Acrylates copolymer Balance 0/55 National Starch ADR-50% solids... 

The tightrope situation that arises from balancing high mobility, low crystallinity, and optimum crosslinking is often dealt with by using copolymers rather than homopolymers. With chain composition as an additional variable, molecules can be tailored better for specific application situations. 

Adhesives. Acryhc emulsion and solution polymers form the basis of a variety of adhesive types. The principal use is in pressure-sensitive adhesives, where a film of a very low T (<—20 " C) acrylic polymer or copolymer is used on the adherent side of tapes, decals, and labels. Acrylics provide a good balance of tack and bond strength with exceptional color stabiUty and resistance to aging (201,202). AcryUcs also find use in numerous types of constmction adhesive formulations and as film-to-film laminating adhesives (qv). 

Useflil properties of acrylonitrile copolymers, such as rigidity, gas barrier, chemical and solvent resistance, and toughness, are dependent upon the acrylonitrile content in the copolymers. The choice of the composition of SAN copolymers is dictated by their particular appHcations and performance requirements. The weU-balanced and unique properties possessed by these copolymers have led to broad usage in a wide variety of appHcations. 

An a priori method for choosing a surfactant was attempted by several researchers (50) using the hydroph i1 e—1 ip oph i1 e balance or HLB system (51). In the HLB system a surfactant soluble in oil has a value of 1 and a surfactant soluble in water has a value of 20. Optimum HLB values have been reported for latices made from styrene, vinyl acetate, methyl methacrylate, ethyl acrylate, acrylonitrile, and their copolymers and range from 11 to 18. The HLB system has been criticized as being imprecise (52). 

Polypropylene polymers are typically modified with ethylene to obtain desirable properties for specific applications. Specifically, ethylene—propylene mbbers are introduced as a discrete phase in heterophasic copolymers to improve toughness and low temperature impact resistance (see Elastomers, ETHYLENE-PROPYLENE rubber). This is done by sequential polymerisation of homopolymer polypropylene and ethylene—propylene mbber in a multistage reactor process or by the extmsion compounding of ethylene—propylene mbber with a homopolymer. Addition of high density polyethylene, by polymerisation or compounding, is sometimes used to reduce stress whitening. In all cases, a superior balance of properties is obtained when the sise of the discrete mbber phase is approximately one micrometer. Examples of these polymers and their properties are shown in Table 2. Mineral fillers, such as talc or calcium carbonate, can be added to polypropylene to increase stiffness and high temperature properties, as shown in Table 3. 

Vinyl acetate is another monomer used in latex manufacture for architectural coatings. When copolymerized with butyl acrylate, it provides a good balance of cost and performance. The interior flat latex paint market in North America is almost completely dominated by vinyl acetate—acryHc copolymers. Vinyl acetate copolymers are typicaHy more hydrophilic than aH-acryHc polymers and do not have the same ultraviolet light resistance as acryHcs as a result. 

In poly(vinyl acetate) copolymer emulsions, the properties are significantly affected by the composition of the aqueous phase and by the stabilizers and buffers used iu the preparation of these materials, along with the process conditions (eg, monomer concentrations, pH, agitation, and temperature). The emulsions are milk-white Hquids containing ca 55 wt % PVAc, the balance being water and small quantities of wetting agents or protective coUoids. 

The earliest study describing vulcanised polymers of esters of acryUc acid was carried out in Germany by Rohm (2) before World War I. The first commercial acryUc elastomers were produced in the United States in the 1940s (3—5). They were homopolymers and copolymers of ethyl acrylate and other alkyl acrylates, with a preference for poly(ethyl acrylate) [9003-32-17, due to its superior balance of properties. The main drawback of these products was the vulcanisation. The fully saturated chemical stmcture of the polymeric backbone in fact is inactive toward the classical accelerators and curing systems. As a consequence they requited the use of aggressive and not versatile compounds such as strong bases, eg, sodium metasiUcate pentahydrate. To overcome this limitation, monomers containing a reactive moiety were incorporated in the polymer backbone by copolymerisation with the usual alkyl acrylates. 

Mihtary interest in the development of fuel and thermal resistant elastomers for low temperature service created a need for fluorinated elastomers. In the early 1950s, the M. W. Kellogg Co. in a joint project with the U.S. Army Quartermaster Corps, and 3M in a joint project with the U.S. Air Force, developed two commercial fluorocarbon elastomers. The copolymers of vinyUdene fluoride, CF2=CH2, and chlorotrifluoroethylene, CF2=CFC1, became available from Kellogg in 1955 under the trademark of Kel-F (1-3) (see Fluorine compounds, ORGANic-POLYcm.OROTRiFLUOROETHYLENE Poly(vinylidene) fluoride). In 1956, 3M introduced a polymer based on poly(l,l-dihydroperfluorobutyl acrylate) trademarked 3M Brand Fluorombber 1F4 (4). The poor balance of acid, steam, and heat resistance of the latter elastomer limited its commercial use. 

Vulcanizates of ECH homopolymer and ECH—EO copolymer are resistant to ASTM oils, aUphatic solvents, and aromatic-containing fuels, showing low swell after exposure. The polymers do not harden after exposure to these fluids, although plasticizer may be extracted. Overall, these polymers offer a good balance of heat, ozone, and fuel resistance over a broad temperature range. 

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. 

Mixtures of monomers can be used to balance properties. This is possible due to the ease of copolymer formation via free-radical polymerization. The glass transition temperature of acrylic copolymers can be predicted from the weight fraction of the component monomers and the glass transition temperatures of the respective homopolymers [20]. Eq. 3 (commonly known as the Fox equation) is reported ... 

Nitrile rubber (NBR) was first commercialized by I.G. Farbindustry, Germany, in 1937, under the trade name of Buna N. Its excellent balance of properties confers it an important position in the elastomer series. Nitrile rubber, a copolymer of butadiene and acrylonitrile, is widely used as an oil-resistant rubber. The acrylonitrile content decides the ultimate properties of the elastomer. In spite of possessing a favorable combination of physical properties, there has been a continuous demand to improve the aging resistance of NBR due to the tougher requirements of industrial and automotive applications. 

Extremely soft and fluid blends of E-plastomers with iPP have been made by incorporating a large amount of a low-density E-plastomer with added process oil for fluidity and softness with a minor amount of iPP [10]. In a representative formulation, 56 parts of an impact copolymer (ICP) which had 62 wt% of iPP and the balance an EPR, 22 parts of an E-plastomer (hexene comonomer), 11 parts of an E-plastomer (octene comonomer), and 5 parts of talc showed a Rockwell R hardness 77,... 

This paper presents the physical mechanism and the structure of a comprehensive dynamic Emulsion Polymerization Model (EPM). EPM combines the theory of coagulative nucleation of homogeneously nucleated precursors with detailed species material and energy balances to calculate the time evolution of the concentration, size, and colloidal characteristics of latex particles, the monomer conversions, the copolymer composition, and molecular weight in an emulsion system. The capabilities of EPM are demonstrated by comparisons of its predictions with experimental data from the literature covering styrene and styrene/methyl methacrylate polymerizations. EPM can successfully simulate continuous and batch reactors over a wide range of initiator and added surfactant concentrations. 

Rate of Formation of Primary Precursors. A steady state radical balance was used to calculate the concentration of the copolymer oligomer radicals in the aqueous phase. This balance equated the radical generation rate with the sum of the rates of radical termination and of radical entry into the particles and precursors. The calculation of the entry rate coefficients was based on the hypothesis that radical entry is governed by mass transfer through a surface film in parallel with bulk diffusion/electrostatic attraction/repulsion of an oligomer with a latex particle but in series with a limiting rate determining step (Richards, J. R. et al. J. AppI. Polv. Sci.. in press). Initiator efficiency was... 

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