Flexible resins

Ethylene has also been copolymerised with a number of non-olefinic monomers and of the copolymers produced those with vinyl acetate have so far proved the most significant commercially . The presence of vinyl acetate residues in the chain reduces the polymer regularity and hence by the vinyl acetate content the amount of crystallinity may be controlled. Copolymers based on 45% vinyl acetate are rubbery and may be vulcanised with peroxides. They are commercially available (Levapren). Copolymers with about 30% vinyl acetate residues (Elvax-Du Pont) are flexible resins soluble in toluene and benezene at room temperature and with a tensile strength of about lOOOlbf/in (6.9 MPa) and a density of about 0.95 g/cm. Their main uses are as wax additives and as adhesive ingredients. 

Where a flexible resin is required adipic and, rarely, sebacic acids are used. Whereas the phthalic acids give a rigid link these materials give highly flexible linkages and hence flexibility in the cured resin. Flexible resins are of value in gel coats. 

Polyquinoxalines Stable in air at 500°C (932°F) tough, somewhat flexible resins make film, adhesive. 

Flexible resins and Tough, good impact resistance, Vibration damping machine covers and... 

The majority of PVC is produced by free-radical suspension polymerization of vinyl chloride. PVC is available in a number of grades and forms rigid or flexible resins. A flexible resin is obtained by incorporating plasticizers into the resins. 

Glycidyl Ethers of Aliphatic Polyols. Glycidyl ether epoxy resins based on polyols provide greater flexibility and lower softening temperatures for the final cured epoxy system. The polyol is reacted with epichlorohydrin to produce these resins. These resins are generally not used alone because of water sensitivity and overall lack of toughness. However, they serve as modifiers for DGEBA-based epoxy resins. An idealized structure for a flexible resin based on this chemistry is shown in Fig. 2.9. 

Property 70 Parts DGEBA 30 parts flexible resin (EEW 320) 70 Parts DGEBA 30 parts flexible resin (EEW 190) 100 Percent DGEBA... 

Using a higher-molecular-weight, more flexible resin... 

Acrylics exhibit excellent adhesion to substrates such as concrete, masonry and wood. The majority of acrylic products are applied without using primer and give satisfactory adhesion. The more flexible resins give superior adhesion within the family of acrylic resins. The adhesive qualities of individual resins vary both with flexibility and with functionality. 

DER [Dow], TM for a series of epoxies including liquid resins, solid resins and solutions, flexible resins, and flame-retardant resins. 

Emcast [Bectronic Materials] One-part epoxy resins uv-curable flexible resin for decttonic encqpsulaticni, d n g, and adhesion applies. 

Polyesters of this class vary from heavy, sticky gums to brittle but tacky solids. For this reason they are seldom handled in this form but are immediately diluted with the monomer of choice. The resins are available in a wide range of viscosities. Most of the marketed resins yield rigid materials when cured. Flexible resins are available but are used for blending with rigid ones to impart flexibility. The properties of a typical general-purpose resin for matched die-molding work are lisied in Table 15-9. 

Impregnation with the Ludopal formulation gave the following results For beech samples, the mean shrinkages were 0.1% (Z), 0.9% (r), and 3.5% (t) Some radial cracks were present because the wood has a relatively soft surface. The softness can be explained by the presence of butyl acrylate in the formulation, which gave a more flexible resin than the Norsodyne formulation, but was more sensitive to oxygen inhibition. For oak samples, the mean shrinkages were 0.4% (Z), 1.2% (r), and 0.9% (f). No cracks were observed. 

As indicated earlier, PVC is available as rigid or flexible resins. Flexible PVC is obtained by incorporating internal or external plasticizers into PVC. Rigid PVC accormts for about 55% of PVC used while plasticized or flexible PVC accounts for the remainder. The largest single use of PVC is for piping systems. The major areas of use and typical applications of PVC are listed in Table 15.5. 

From the dynamic mechanical properties, resin D is evidently more flexible than resin A. As the resins are cured, the more flexible resin (D) develops less internal stress than the stiffer resin A due to greater molecular mobility. As wood absorbs and releases moisture during cyclic wet-dry treatment, the adhesive joint is subjected to cyclic stress. Resin D, due to its flexibility, is able to respond reversibly to the cyclic stress whereas the stiffer resins begin to degrade after five wet-dry cycles. 

Polyisobutenes do not crystallize. Polyisobutenes of low molecular mass are flexible resins, and those of high molecular mass are elastomers. Their use in the paint sector is restricted on account of their aliphatic nature and limited compatibility with other binders. They are employed in combination with hydrocarbons such as paraffins, rubber, and bitumen. They are used as plasticizing components. 

FeO ferrous oxide (iron oxide) FRTM flexible resin transfer molding... 

Although PLA-oriented film is transparent and thermally resistant, some problems may occur due to its brittleness. When used as a bag, for example, PLA film tends to create a rustling sound when products are placed into the bag. Many methods have been reported to improve the flexibility of PLA films, such as addition of plasticizer [232] and blending with other flexible/biodegradable resins. Some plasticizers with enhanced performance have been developed by Daihachi Chemicals, Arakawa Chemicals, and Riken Vitamin. Lamination with transparent flexible resins such as PE or PP has been used to make flexible PLA film while maintaining transparency [233]. PLA-oriented film begins to shrink above... 

The change in mode of failure in the burst tests also indicates that the laminate has been affected by 25 years of service. The major pipe wall fractures are typical for pipe made from less flexible resins. It appears that significant changes in resin properties have begun to occur. 

Chem. Descrip. Soft, flexible resin supplied as solv. sol n. 

Uses Used in colored baking enamels for space heaters, stoves alone or blended with Dow Comir 805 resin to prorTxrle intermediate hardness food-contact coatings Features Air dries tack-free Regulatory FDA 21 CFR 175.300 Properties Soft, flexible resin 50% solids Dow Coming 808 Resin [DowComingj... 

Uses Urethane for low-melting in-line/off-line blister board coatings Features Very soft, flexible resin works well with polystyrene and other substrates that often pose adhesion problems Properties Dens. 8.7 Ib/gal vise, as required pH 7.0-8.5 lens. sir. 3500 psi elong. 600% hardness (Sward) < 10 33 2% solids Solucote 101-113 [SoluoQ... 

Uses Urethane for in-line high-gloss heat-seal blister board coating for clay-treated, virgin, and recycled board, for indirect contact with wet food, and direct contact with pharmaceuticals, hard candy, gum balls Features Soft, flexible resin Regulatory FDA approved... 

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