Stress bisphenol

Figure C2.1.17. Stress-strain curve measured from plane-strain compression of bisphenol-A polycarbonate at 25 ° C. The sample was loaded to a maximum strain and then rapidly unloaded. After unloading, most of the defonnation remains.

Figure 23. Stress-relaxation curves of amorphous bisphenol A polycarbonate at the different temperatures shown by the curves. The numbers in brackets are the maximum deformations used in the tests. (From Ref. 217.)...

Oxidative stress and covalent binding to macromolecules. Oxidation to the epoxide occurs via a tetrahedral intermediate, which can form either an epoxide or a phenol directly (see the scheme below). The epoxide can covalently bind nucleophiles, such as DNA or proteins, to open up the epoxide to a phenol and make toxic covalent adducts. The phenols can be further oxidized to bisphenols, which can in turn form quinones. Quinones can cause serious oxidative damage to cells through radical pathways, or can alkylate N- or S-nucleophiles, such as glutathione and glycine. 

Fig, 19. (a) Sketch of the channel-die apparatus used for the deformation experiment. Dimensions are in millimetres. The compression stamp is moved along the deformation direction D. The flow of the sample is constrained by the rigid walls of the die in the direction C, and free flow is possible in the direction F. (b) Stress (cr)-strain(e) diagram resulting from channel-die extrusion of bisphenol-A polycarbonate at 300 K and a strain rate of e = 0.01 s l. (c, d) Dipolar DECODER spectra of 13C-labelled bisphenol-A polycarbonate before and after deformation. The spectra exhibit a characteristic star-like ridge pattern. Each of three types of corners (C, D, F) in the pattern corresponds to vectors oriented along a particular direction in the channel-die used for the experiment, (e, f) The anisotropy caused by the deformation becomes readily visible in the difference spectrum (deformed minus undeformed). For clarity, the negative (f) and positive contours (e) have been drawn separately. (Reproduced from Utz et al. with permission.)... 

Morphology, Viscoelastic Properties, and Stress-Strain Behavior of Blends of Polycarbonate of Bisphenol-A (PC) and Atactic Polystyrene (PST)... 

Estimate, the optical-stress coefficient for poly(bisphenol-A carbonate), [Ci6Hi403]n. with Vw = 144 cm3/mol unit. 

Kambour RP, Gruner CL, Romagosa EE (1974) Bisphenol-A polycarbonate immersed in organic media swelling and response to stress. Macromolecules 7(2) 248-253... 

Fig.16 S-N fatigue diagram of a bulk diglycidyl ether of bisphenol (DGEBA)/isophoron diamine (IPD) epoxy polymer giving the maximum applied stress as a function of the number of cycles to failure (three-point bending, 25 Hz, stress ratio OminMnax = 0.1) (from [53]). The two dotted lines correspond to theoretical values of the amplitude of the effective tensile stress, Acr, calculated for (a) gross slip condition and (b) under partial slip condition for an imposed displacement ( 10 xm) which corresponds to the experimental contact endurance limit at 105 cycles...

Two families of transparent polycarbonate-silicone multiblock polymers based on the polycarbonates of bisphenol acetone (BPA) and bisphenol fluorenone (BPF) were synthesized. Incorporation of a 25% silicone block in BPA polycarbonate lowers by 100°C the ductile-brittle transition temperature of notched specimens at all strain rates silicone block incorporation also converts BPF polycarbonate into a ductile plastic. At the ductile-brittle transition two competing failure modes are balanced—shear yielding and craze fracture. The yield stress in each family decreases with silicone content. The ability of rubber to sustain hydrostatic stress appears responsible for the fact that craze resistance is not lowered in proportion to shear resistance. Thus, the shear biasing effects of rubber domains should be a general toughening mechanism applicable to many plastics. 

Recently, Dettenmaier and Kausch have observed an intrinsic craze phenomenon in bisphenol-A polycarbonate (PC), drawn to high stresses and strains in a temperature region close to the glass transition temperature, T. This type of crazing is not only initiated under extremely well defined conditions which reflect specific intrinsic properties of the polymer but also produces numerous crazes of a very regular fibrillar structure. These crazes were called crazes II in order to distinguish them from the extrinsic type of craze, called craze I. As shown by the schematic representation in Figure 1, a detailed quantitative analysis of intrinsic crazes in terms of craze initiation and microstructure was possible. The basis of this analysis and the results obtained are reviewed in this article. 

Li, X., Environmental stress cracking resistance of a new copolymer of bisphenol-A, Polym. Degrad. Stab. 2005, 90, 44-52. 

In some epoxy systems ( 1, ), it has been shown that, as expected, creep and stress relaxation depend on the stoichiometry and degree of cure. The time-temperature superposition principle ( 3) has been applied successfully to creep and relaxation behavior in some epoxies (4-6)as well as to other mechanical properties (5-7). More recently, Kitoh and Suzuki ( ) showed that the Williams-Landel-Ferry (WLF) equation (3 ) was applicable to networks (with equivalence of functional groups) based on nineteen-carbon aliphatic segments between crosslinks but not to tighter networks such as those based on bisphenol-A-type prepolymers cured with m-phenylene diamine. Relaxation in the latter resin followed an Arrhenius-type equation. 

The stress-strain curves of ductile thermoplastics (including both glassy amorphous polymers such as bisphenol-A polycarbonate and semicrystalline polymers such as polyethylene at room temperature) have the general shapes shown in Figure 11.16(a), which can be compared with the shape of the stress-strain curve of a very brittle material shown in Figure 11.16(b). The stress-strain curves of polymers which are neither very ductile nor very brittle under the testing conditions being utilized have appearances which are intermediate between these. two extremes. 

---