Polycarbonate physical

Table 1. High heat polycarbonate physical properties...

Acrylic Resins. The first synthetic polymer denture material, used throughout much of the 20th century, was based on the discovery of vulcanised mbber in 1839. Other polymers explored for denture and other dental uses have included ceUuloid, phenolformaldehyde resins, and vinyl chloride copolymers. Polystyrene, polycarbonates, polyurethanes, and acryHc resins have also been used for dental polymers. Because of the unique combination of properties, eg, aesthetics and ease of fabrication, acryHc resins based on methyl methacrylate and its polymer and/or copolymers have received the most attention since their introduction in 1937. However, deficiencies include excessive polymerization shrinkage and poor abrasion resistance. Polymers used in dental appHcation should have minimal dimensional changes during and subsequent to polymerization exceUent chemical, physical, and color stabiHty processabiHty and biocompatibiHty and the abiHty to blend with contiguous tissues. 

Unless great care is taken in control of phenol/acetone ratios, reaction conditions and the use of catalysts, a number of undesirable by-products may be obtained such as the o-,p- and o-,o- isomers of bis-phenol A and certain chroman-type structures. Although tolerable when the bis-phenol A is used in epoxy resins, these have adverse effects on both physical properties and the colour of polycarbonate resins. 

SCHNELL, H., Chemistij and Physics of Polycarbonates, Interscience, New York (1964)... 

Hydrolysis studies compared a polycarbonate urethane with a poly(tetramethyl-ene adipate) urethane and a polyether urethane based on PTMEG. After 2 weeks in 80°C water, the polycarbonate urethane had the best retention of tensile properties [92], Polycarbonates can hydrolyze, although the mechanism of hydrolysis is not acid-catalyzed, as in the case of the polyesters. Polycarbonate polyurethanes have better hydrolysis resistance than do standard adipate polyurethanes, by virtue of the highest retention of tensile properties. It is interesting to note in the study that the PTMEG-based urethanes, renowned for excellent hydrolysis resistance, had lower retention of physical properties than did the polycarbonate urethanes. 

Nearly all of the polymers produced by step-growth polymerization contain heteroatoms and/or aromatic rings in the backbone. One exception is polymers produced from acyclic diene metathesis (ADMET) polymerization.22 Hydrocarbon polymers with carbon-carbon double bonds are readily produced using ADMET polymerization techniques. Polyesters, polycarbonates, polyamides, and polyurethanes can be produced from aliphatic monomers with appropriate functional groups (Fig. 1.1). In these aliphatic polymers, the concentration of the linking groups (ester, carbonate, amide, or urethane) in the backbone greatly influences the physical properties. 

Phosphorus -bromine flame retardant synergy was demonstrated in a 2/1 polycarbonate/polyethylene blend. These data also show phosphorus to be about ten times more effective than bromine in this blend. Brominated phosphates, where both bromine and phosphorus are in the same molecule, were also studied. In at least one case, synergy is further enhanced when both phosphorus and bromine are in the same molecule as compared with a physical blend of a phosphorus and a bromine compound. On a weight basis, phosphorus and bromine in the same molecule are perhaps the most efficient flame retardant combination. The effect of adding an impact modifier was also shown. 

How does the molecular architecture of the bisphenol molecule affect the physical properties of the final polycarbonate polymer ... 

Traditionally, ultrafilters have been manufactured from cellulose acetate or cellulose nitrate. Several other materials, such as polyvinyl chloride and polycarbonate, are now also used in membrane manufacture. Such plastic-type membranes exhibit enhanced chemical and physical stability when compared with cellulose-based ultrafiltration membranes. An important prerequisite in manufacturing ultrafilters is that the material utilized exhibits low protein adsorptive properties. 

Meldrum s acid chemistry, 21 151,152, 153 Melengesterol acetate (MGA), 10 871 Melissic acid, physical properties, 5 30t Melt behavior, of polycarbonates, 19 805 Meltblown fabrics, 17 478-479, 495 Meltblown fibers, 11 237, 240-241 Melt casting, 14 230 Melt crystallization, 3 137—141... 

Schnell, H. Chemistry and Physics of Polycarbonate , Interscience Publishers, New York, 1964, pp. 37-41. 

Engineering resins are polymers designed to excel in. certain physical characteristics. For the most part they are thermoplastics, but they can be thermosets as well. Examples are Nylon 6, Nylon 66, polycarbonates, and polyesters. Phenolics can be considered engineering resins. 

Requirements for CD-quality material are polycarbonate with low levels of chemical impurities, low particle levels, thermal stability, excellent mold release, excellent clarity, as well as constant flow and constant mechanical behavior (for reproducibility). There exists a time/cost balance. High molecular weight polycarbonate offers a little increase in physical property but the flow rate is slow, making rapid production of CDs difficult. The molecular weight where good mechanical strength and reasonable flow occurs, and that allows for short cycles, is in the range of 16,000-28,000 Da. 

A laser is used to encode information through creation of physical features, sometimes referred to as pits and lands of different reflectivity at the polycarbonate-metal interface. As noted above, recordable CDs contain an organic dye between the polycarbonate and metal film. A laser creates areas of differing reflectiveness in the dye layer through photochemical reactions. 

Thorat SD, Phillips PJ, Semenov V, Gakh A (2003) Physical properties of aliphatic polycarbonates made from CO2 and epoxides. J Appl Polym Sci 89 1163-1176... 

High-impact polystyrene (HIPS) is produced by polymerizing styrene in the presence of a rubber, usually poly(l,3-butadiene). HIPS has improved impact resistance compared to polystyrene and competes with ABS products at low-cost end applications such as fast-food cups, lids, takeout containers, toys, kitchen appliances, and personal-care product containers. HIPS as well as ABS and SMA are used in physical blends with other polymers, such as polycarbonates, polyesters, and polyamides, to improve impact resistance (Sec. 2-13c-3). 

SchneU H (1964) Chemistry and physics of polycarbonates. John Wiley Interscience, New York... 

Table 15.7 Thermal and Physical Properties of Polycarbonates (Typical Values)...

TABLE 1. Physical Properties of Polycarbonate Prepared Using Bisphenol A, 3,3-bis(4-hydroxy-phenyl)-l-phenyl-lH-indol-2-one, and Phosgene Dissolved in C Cb/Chlorobenzene at Ambient Temperature... 

---