Physical properties resins

Styrene-Acrylonitrile (SAN) Copolymers. SAN resins are random, amorphous copolymers whose properties vary with molecular weight and copolymer composition. An increase in molecular weight or in acrylonitrile content generally enhances the physical properties of the copolymer but at some loss in ease of processing and with a slight increase in polymer color. 

Physical Properties. Furfuryl alcohol (2-furanmethanol) [98-00-0] is aHquid, colorless, primary alcohol with a mild odor. On exposure to air, it gradually darkens in color. Furfuryl alcohol is completely miscible with water, alcohol, ether, acetone, and ethyl acetate, and most other organic solvents with the exception of paraffinic hydrocarbons. It is an exceUent, highly polar solvent, and dissolves many resins. 

SAN resins possess many physical properties desked for thermoplastic appHcations. They are characteristically hard, rigid, and dimensionally stable with load bearing capabiHties. They are also transparent, have high heat distortion temperatures, possess exceUent gloss and chemical resistance, and adapt easily to conventional thermoplastic fabrication techniques (7). 

There are two major producers of SAN resin in the United States, Monsanto Chemical Company and The Dow Chemical Company, which market these materials under the names of Lustran and Tydl, respectively. Some typical physical properties of these have been shown in Table 1. Production figures for SAN and ABS for the 1980s are shown in Table 6 (148). 

The physical properties of polyurethane adhesives result from a special form of phase separation which occurs in the cross-linked polyurethane stmcture. The urethane portions of polyurethanes tend to separate from the polyol portion of the resin, providing good shear strength, good low temperature flexibiUty, and high peel strength. Catalysts such as dibutyltin dilaurate [77-58-7], stannous octoate [1912-83-0], l,4-diazabicyclo[2.2.2]octane... 

In the area of moleculady designed hot-melt adhesives, the most widely used resins are the polyamides (qv), formed upon reaction of a diamine and a dimer acid. Dimer acids (qv) are obtained from the Diels-Alder reaction of unsaturated fatty acids. Linoleic acid is an example. Judicious selection of diamine and diacid leads to a wide range of adhesive properties. Typical shear characteristics are in the range of thousands of kilopascals and are dependent upon temperature. Although hot-melt adhesives normally become quite brittle below the glass-transition temperature, these materials can often attain physical properties that approach those of a stmctural adhesive. These properties severely degrade as the material becomes Hquid above the melt temperature. 

Emulsion Adhesives. The most widely used emulsion-based adhesive is that based upon poly(vinyl acetate)—poly(vinyl alcohol) copolymers formed by free-radical polymerization in an emulsion system. Poly(vinyl alcohol) is typically formed by hydrolysis of the poly(vinyl acetate). The properties of the emulsion are derived from the polymer employed in the polymerization as weU as from the system used to emulsify the polymer in water. The emulsion is stabilized by a combination of a surfactant plus a coUoid protection system. The protective coUoids are similar to those used paint (qv) to stabilize latex. For poly(vinyl acetate), the protective coUoids are isolated from natural gums and ceUulosic resins (carboxymethylceUulose or hydroxyethjdceUulose). The hydroHzed polymer may also be used. The physical properties of the poly(vinyl acetate) polymer can be modified by changing the co-monomer used in the polymerization. Any material which is free-radically active and participates in an emulsion polymerization can be employed. Plasticizers (qv), tackifiers, viscosity modifiers, solvents (added to coalesce the emulsion particles), fillers, humectants, and other materials are often added to the adhesive to meet specifications for the intended appHcation. Because the presence of foam in the bond line could decrease performance of the adhesion joint, agents that control the amount of air entrapped in an adhesive bond must be added. Biocides are also necessary many of the materials that are used to stabilize poly(vinyl acetate) emulsions are natural products. Poly(vinyl acetate) adhesives known as "white glue" or "carpenter s glue" are available under a number of different trade names. AppHcations are found mosdy in the area of adhesion to paper and wood (see Vinyl polymers). 

Filled Resins. Filled compositions meet the requkements of an increased variety of mechanical, electrical, and chemical appHcations. Physical properties of filled granular compounds are shown in Table 4 (81). 

Mech nic lProperties. Extensive Hsts of the physical properties of FEP copolymers are given in References 58—63. Mechanical properties are shown in Table 3. Most of the important properties of FEP are similar to those of PTFE the main difference is the lower continuous service temperature of 204°C of FEP compared to that of 260°C of PTFE. The flexibiUty at low temperatures and the low coefficients of friction and stabiUty at high temperatures are relatively independent of fabrication conditions. Unlike PTFE, FEP resins do not exhibit a marked change in volume at room temperature, because they do not have a first-order transition at 19°C. They ate usehil above —267°C and are highly flexible above —79°C (64). 

Modified ETEE is less dense, tougher, and stiffer and exhibits a higher tensile strength and creep resistance than PTEE, PEA, or EEP resins. It is ductile, and displays in various compositions the characteristic of a nonlinear stress—strain relationship. Typical physical properties of Tef2el products are shown in Table 1 (24,25). Properties such as elongation and flex life depend on crystallinity, which is affected by the rate of crysta11i2ation values depend on fabrication conditions and melt cooling rates. 

Extmsion of polyethylene and some polypropylenes is usually through a circular die into a tubular form, which is cut and collapsed into flat film. Extmsion through a linear slot onto chilled rollers is called casting and is often used for polypropylene, polyester, and other resins. Cast, as well as some blown, films may be further heated and stretched in the machine or in transverse directions to orient the polymer within the film and improve physical properties such as tensile strength, stiffness, and low temperature resistance. 

Numerous avenues to produce these materials have been explored (128—138). The synthesis of two new fluorinated bicycHc monomers and the use of these monomers to prepare fluorinated epoxies with improved physical properties and a reduced surface energy have been reported (139,140). The monomers have been polymerized with the diglycidyl ether of bisphenol A, and the thermal and mechanical properties of the resin have been characterized. The resulting polymer was stable up to 380°C (10% weight loss by tga). 

Most hydrocarbon resins are composed of a mixture of monomers and are rather difficult to hiUy characterize on a molecular level. The characteristics of resins are typically defined by physical properties such as softening point, color, molecular weight, melt viscosity, and solubiHty parameter. These properties predict performance characteristics and are essential in designing resins for specific appHcations. Actual characterization techniques used to define the broad molecular properties of hydrocarbon resins are Fourier transform infrared spectroscopy (ftir), nuclear magnetic resonance spectroscopy (nmr), and differential scanning calorimetry (dsc). 

Polyethylene. Traditional melt spun methods have not utilized polyethylene as the base polymer because the physical properties obtained have been lower compared to those obtained with polypropylene. Advances in polyethylene technology may result in the commercialization of new spunbonded stmctures having characteristics not attainable with polypropylene. Although fiber-grade polyethylene resin was announced in late 1986 (11,12), it has seen limited acceptance because of higher costs and continuing improvements in polypropylene resin technology (see Olefin POLYMERS, POLYETHYLENE). 

Physical Properties. LLDPE is a sernicrystaUine plastic whose chains contain long blocks of ethylene units that crystallize in the same fashion as paraffin waxes or HDPE. The degree of LLDPE crystallinity depends primarily on the a-olefin content in the copolymer (the branching degree of a resin) and is usually below 40—45%. The principal crystalline form of LLDPE is orthorhombic (the same as in HDPE) the cell parameters of nonbranched PE are a = 0.740 nm, b = 0.493 nm, and c (the direction of polymer chains) = 0.2534 nm. Introduction of branching into PE molecules expands the cell slightly thus a increases to 0.77 nm and b to around 0.50 nm. 

Binders and Resins. The choice of binder is the most important ingredient choice in the formulation process because the binder affects the performance properties of a paint more than any other single ingredient (3). The physical properties of binders required for paints include the abiHty to dry or cure under various ambient conditions, good adhesion to various substrates, abrasion resistance, washabiHty, flexibiHty, water resistance, and ultraviolet light resistance. The balance of these required properties is mosdy dependent on whether the paint is being developed for interior or exterior appHcations. 

Special resoles are obtained with amine catalysts, which affect chemical and physical properties because amine is incorporated into the resin. For example, the reaction of phenol, formaldehyde, and dimethylamine is essentially quantitative (28). 

Waferboard, a more recent wood constmction product, competes more with plywood than particle board. Waferboard and strand board are bonded with soHd, rather than Hquid, phenoHc resins. Both pulverized and spray-dried, rapid-curing resins have been successfully appHed. Wafers are dried, dusted with powdered resin and wax, and formed on a caul plate. A top caul plate is added and the wafers are bonded in a press at ca 180°C for 5—10 min. Physical properties such as flexural strength, modulus, and internal bond are similar to those of a plywood of equivalent thickness. 

Uses. Phthabc anhydride is used mainly in plasticizers, unsaturated polyesters, and alkyd resins (qv). PhthaUc plasticizers consume 54% of the phthahc anhydride in the United States (33). The plasticizers (qv) are used mainly with poly(vinyl chloride) to produce flexible sheet such as wallpaper and upholstery fabric from normally rigid polymers. The plasticizers are of two types diesters of the same monohydric alcohol such as dibutyl phthalate, or mixed esters of two monohydric alcohols. The largest-volume plasticizer is di(2-ethylhexyl) phthalate [117-81-7] which is known commercially as dioctyl phthalate (DOP) and is the base to which other plasticizers are compared. The important phthahc acid esters and thek physical properties are Hsted in Table 12. The demand for phthahc acid in plasticizers is naturally tied to the growth of the flexible poly(vinyl chloride) market which is large and has been growing steadily. 

Steps 1 and 2 can be described as physical plasticization, and the precise details of how this is carried out depends on the appHcations technology involved, ie, suspension or paste PVC. The rate at which step 2 occurs depends on the physical properties of plasticizer visocity, resin porosity, and particle size. 

Acrylic Polymers. Although considerable information on the plasticization of acryUc resins is scattered throughout journal and patent hterature, the subject is compHcated by the fact that acryUc resins constitute a large family of polymers rather than a single polymeric species. An infinite variation in physical properties may be obtained through copolymerization of two or more acryUc monomers selected from the available esters of acryUc and methacryhc acid (30) (see Acrylic esterpolya rs Methacrylic acid and derivatives). 

Amino resins react with ceUulosic fibers and change their physical properties. They do not react with synthetic fibers, such as nylon, polyester, or acryhcs, but may self-condense on the surface. This results in a change in the stiffness or resiHency of the fiber. Partially polymerized amino resins of such molecular size that prevents them from penetrating the amorphous portion of ceUulose also tend to increase the stiffness or resiHency of ceUulose fibers. 

Pyrrole is a colorless, slightly hygroscopic Hquid which, if fresh, emits an odor like that of chloroform. However, it darkens on exposure to air and eventually produces a dark brown resin. It can be preserved by excluding air from the storage container, preferably by displacement with ammonia to prevent acid-catalyzed polymerization. A review of the physical and theoretical aspects of pyrrole is found in Reference 4. Some physical properties of pyrrole are Hsted in Table 1. 

Rosin ester resins are used as modifiers in the formulation of chewing gum. The rosin derivative modifies the physical properties of the polymer used, providing the desired masticatory properties. The glycerol ester of hydrogenated rosin is the predominant choice, because stabilized materials have improved aging resistance, which extends the shelf life of the gum. 

PVC. Poly(vinyl chloride) (PVC), a very versatile polymer, is manufactured by the polymerisation of vinyl chloride monomer, a gaseous substance obtained from the reaction of ethylene with oxygen and hydrochloric acid. In its most basic form, the resin is a relatively hard material that requites the addition of other compounds, commonly plasticisers and stabilisers as well as certain other ingredients, to produce the desired physical properties for roofing use. The membranes come in both reinforced and nonreinforced constmctions, but since the 1980s the direction has been toward offering only reinforced membranes. The membrane thickness typically mns from 0.8—1.5 mm and widths typically in the range of 1.5—4.6 m. 

Divinylbenzene. This is a specialty monomer used primarily to make cross-linked polystyrene resins. Pure divinylbenzene (DVB) monomer is highly reactive polymericaHy and is impractical to produce and store. Commercial DVB monomer (76—79) is generally manufactured and suppHed as mixtures of m- and -divinylbenzenes and ethylvinylbenzenes. DVB products are designated by commercial grades in accordance with the divinylbenzene content. Physical properties of DVB-22 and DVB-55 are shown in Table 10. Typical analyses of DVB-22 and DVB-55 are shown in Table 11. Divinylbenzene [1321 -74-0] is readily polymerized to give britde insoluble polymers even at ambient temperatures. The product is heavily inhibited with TBC and sulfur to minimize polymerization and oxidation. 

OC-Methylstyrene. This compound is not a styrenic monomer in the strict sense. The methyl substitution on the side chain, rather than the aromatic ring, moderates its reactivity in polymerization. It is used as a specialty monomer in ABS resins, coatings, polyester resins, and hot-melt adhesives. As a copolymer in ABS and polystyrene, it increases the heat-distortion resistance of the product. In coatings and resins, it moderates reaction rates and improves clarity. Physical properties of a-methylstyrene [98-83-9] are shown in Table 12. 

The excellent chemical resistance and physical properties of PVA resins have resulted in broad industrial use. The polymer is an excellent adhesive and possesses solvent-, oil-, and grease-resistant properties matched by few other polymers. Poly(vinyl alcohol) films exhibit high tensile strength, abrasion resistance, and oxygen barrier properties which, under dry conditions, are superior to those of any other known polymer. The polymer s low surface tension provides for excellent emulsification and protective coUoid properties. 

Amino resins are lighter in color and have better tensile strength and hardness than phenoHc resins their impact strength and heat and water resistance are less than those of phenoHcs. The melamine—formaldehyde resins are harder and have better heat and moisture resistance than the urea resins, but they are also more expensive. The physical properties of the melamine—formaldehyde laminates are Hsted in Table 1. 

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