Carbon copolymers, properties

The synthesis of his[3-(2-a11y1phenoxy)phtha1imides] and their copolymer properties with BMI have been reported (43). These allylphenoxyimide—BMI copolymers provide toughness and temperature resistance when used in carbon fiber laminates (44). 

Polycarbonate (PC) Resins. Polycarbonates (qv) based on bisphenol A are sold in large quantities. Other bisphenols can be incorporated, but do not give the same favorable combination of properties and cost (82). Small quantities of PC based on tetramethylbisphenol A are used as blending resins (83) and polyester carbonate copolymers are used for appHcations requiring heat-deflection temperatures above those of standard PC resins (47). 

Reports on the detailed investigation of thermal 150,233>, mechanical 233, morphological234 236) behavior and flame resistance 237 and adhesive properties 238 of siloxane carbonate copolymers are available 239,240). 

Numerous copolymer compositions have been screened with regard to ultimate carbon fiber properties, under comparable conditions of spinning, stabilization and carbonization. Although it is evident that different compositions will require different conditions for optimal properties, it was felt that a standard screening procedure, taking care of complete stabilization (match test), and providing for a minimum of fiber breaks, should help to select potential candidates. 

Table 5 shows the results from screening of fibers spun from binary copolymers as precursors. The fibers spun from AN/VBr copolymers are clearly the best with regard to carbon fiber properties. 

Although in some of the cases moderate improvements over the simple binary compositions may be discerned from the Tables 6 and 7, none of the compositions was superior to the binary AN/VBr copolymers, at least not under the screening conditions. It should be noted that VBr containing compositions are again at the top of each of the Tables. The 1 1 blend of AN/MMA + AN/VBr (first in Table 7) is particularly interesting because it shows carbon fiber properties comparable to the binary compositions AN/VBr (4-6 % VBr) with an overall content of VBr of only 2%. 

A polymer solution containing AN/MMA copolymer plus 5% (referred to polymer) of maleic anhydride gelled completely, indicating that the expected crosslinking actually took place. As the maleic anhydride concentration was reduced to 0.5%, fiber spinning was no longer a problem. However, at this low concentration the beneficial effect on carbon fiber properties was only minor (see Table 8). 

The resultant copolymer properties depend on different parameters, such as comonomer content and distribution throughout the polymer chain, as well as the configuration of the asymmetric carbons of the comonomer units. The microstmcture of the copolymer can be controlled by the appropriate choice of reaction conditions... 

New polyester carbonate copolymers afford the first resins with low color, high transmission and low haze combined with low OSU Heat Release values. In addition, the fabricated articles can be hard coated to provide improved levels of scratch resistance. These compositions can be varied to maximize the various mechanical properties depending on the needs of the application. The excellent clarity combined with OSU 65/65 compliance allow for applications such as interior transportation windows/dust covers, partitions, mirrors and lighting lenses. The excellent colorability also allows for the fabrication of interior opaque components for the transportation industry. 

A class of new polyester carbonate copolymers has been developed by GE Plastics that has low OSU heat release values (<55/55) while maintaining low color, high transmission and low haze. This resin complies with FAA requirements on flame, smoke and toxicity and will be hereto referred to as OSU resin. To our knowledge these are the first polymers that have the combination of OSU 65/65 compliance, high clarity and low color. This paper will explore the optical, physical, thermal and FAR properties of the new resins. Hard coated sheets made of OSU resin have been shown to meet OSU 65/65 standards and offer improved scratch resistance. Opaque formulations can be prepared by the addition of dyes and pigments and the properties thereof are also discussed. 

Acrylonitrile (AN), C H N, first became an important polymeric building block in the 1940s. Although it had been discovered in 1893 (1), its unique properties were not realized until the development of nitrile mbbers during World War II (see Elastomers, synthetic, nitrile rubber) and the discovery of solvents for the homopolymer with resultant fiber appHcations (see Fibers, acrylic) for textiles and carbon fibers. As a comonomer, acrylonitrile (qv) contributes hardness, rigidity, solvent and light resistance, gas impermeabiUty, and the abiUty to orient. These properties have led to many copolymer apphcation developments since 1950. 

Two of the perfluoropolyether fluid stmctures yet to be commercialized are interesting. The first stmcture is a strictly alternating copolymer of ethylene oxide and methylene oxide, which has the longest Hquid range of any molecule containing carbon (40). The second stmcture is the perfluoromethylene oxide polyether which has low temperature Hquid properties down to —120° C ... 

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. 

Polycarbonates are prepared commercially by two processes Schotten-Baumaim reaction of phosgene (qv) and an aromatic diol in an amine-cataly2ed interfacial condensation reaction or via base-cataly2ed transesterification of a bisphenol with a monomeric carbonate. Important products are also based on polycarbonate in blends with other materials, copolymers, branched resins, flame-retardant compositions, foams (qv), and other materials (see Flame retardants). Polycarbonate is produced globally by several companies. Total manufacture is over 1 million tons aimuaHy. Polycarbonate is also the object of academic research studies, owing to its widespread utiUty and unusual properties. Interest in polycarbonates has steadily increased since 1984. Over 4500 pubflcations and over 9000 patents have appeared on polycarbonate. Japan has issued 5654 polycarbonate patents since 1984 Europe, 1348 United States, 777 Germany, 623 France, 30 and other countries, 231. 

In order to achieve the desired fiber properties, the two monomers were copolymerized so the final product was a block copolymer of the ABA type, where A was pure polyglycoHde and B, a random copolymer of mostly poly (trimethylene carbonate). The selected composition was about 30—40% poly (trimethylene carbonate). This suture reportedly has exceUent flexibiHty and superior in vivo tensile strength retention compared to polyglycoHde. It has been absorbed without adverse reaction ia about seven months (43). MetaboHsm studies show that the route of excretion for the trimethylene carbonate moiety is somewhat different from the glycolate moiety. Most of the glycolate is excreted by urine whereas most of the carbonate is excreted by expired CO2 and uriae. 

Styrene is a colorless Hquid with an aromatic odor. Important physical properties of styrene are shown in Table 1 (1). Styrene is infinitely soluble in acetone, carbon tetrachloride, benzene, ether, / -heptane, and ethanol. Nearly all of the commercial styrene is consumed in polymerization and copolymerization processes. Common methods in plastics technology such as mass, suspension, solution, and emulsion polymerization can be used to manufacture polystyrene and styrene copolymers with different physical characteristics, but processes relating to the first two methods account for most of the styrene polymers currendy (ca 1996) being manufactured (2—8). Polymerization generally takes place by free-radical reactions initiated thermally or catalyticaHy. Polymerization occurs slowly even at ambient temperatures. It can be retarded by inhibitors. 

Random ethylene-carbon monoxide copolymers have been known for many years and have properties somewhat similar to low density polyethylene. Alternating ECO copolymers were first produced long ago by Reppe of BASF in... 

Polycarbonates with superior notched impact strength, made by reacting bisphenol A, bis-phenol S and phosgene, were introduced in 1980 (Merlon T). These copolymers have a better impact strength at low temperatures than conventional polycarbonate, with little or no sacrifice in transparency. These co-carbonate polymers are also less notch sensitive and, unlike for the standard bis-phenol A polymer, the notched impact strength is almost independent of specimen thickness. Impact resistance increases with increase in the bis-phenol S component in the polymer feed. Whilst tensile and flexural properties are similar to those of the bis-phenol A polycarbonate, the polyco-carbonates have a slightly lower deflection temperature under load of about 126°C at 1.81 MPa loading. 

Polyester Carbonates and Block Copolymers 579 Table 20.9 Selected properties of PC-ABS and PC-PBT alloys... 

---