Poly plasticizers effect

Lai, M.C., Hageman, M.J., Schowen, R.L., Borchardt, R.T., Laiard, B.B., and Topp, E.M. 1999b. Chemical stability of peptides in polymers. 2. Discriminating between solvent and plasticizing effects of water on peptide demidation in poly(vinyl pyrrolidone). J. Pharm. Sci. 88, 1081-1089. 

DMTA is a very interesting tool for characterizing heterogeneous materials in which domains of distinct Tg values coexist. The most interesting cases involve modified thermosets of different types (see Chapter 8). Examples are the use of rubbers (e.g., liquid polybutadiene and random copolymers), or thermoplastics (e.g., polyethersulphone or polyetherimide in epoxy matrices or poly(vinyl acetate) in unsaturated polyesters), as impact modifier (epoxies), or low-profile additives (polyesters). The modifier-rich phase may be characterized by the presence of a new a peak (Fig. 11.10). But on occasions there may be superposition of peaks and the presence of the modifier cannot be easily detected by these techniques. If part of the added polymer is soluble in the thermoset matrix, its eventual plasticizing effect can be determined from the corresponding matrix Tg depletion, and the... 

Hydrophobic polymers and films, such as paraffin wax and poly (vinyl chloride), show no change in stiffness modulus when flooded with water. On the other hand, butyl alcohol on a paraffin wax film causes a slow, slight increase of stiffness modulus over a period of several minutes. The effect of benzene on paraffin films is similar to that of methanol on PVA. A poly (vinyl chloride) film is unaffected by plasticizers such as dimethyl and diethyl phthalate over short time periods. However, PVC gives rise to the ultrasonic modulus anomaly when contacted with tetrahydrofuran, a strong solvent for PVC. The plasticizing effect of dibutyl phthalate on polystyrene has been demonstrated by ultrasonic impedometry (16). No anomalies were found. 

As can be seen from Table 9.12, photochromism is also strongly affected by humidity. It is well known that thiazine and its derivatives undergo photoreduction smoothly in the presence of such activated surfaces as silica gel and alumina with water molecules,37 and that methylene blue is also photochemically reduced in acid solution, even with only available water as the reducing agent38 Therefore the water present in polymer films must produce a thionine-water hydration system, which accelerates the rate of the photoreduction of thionine, as well as promoting the contact of reductants by a plasticizer effect. PVA, used as the matrix, can also play the role of reductant, but its extent may be minor as compared with the added reductant. The effect of water is supported by the fact that a less hydrophilic polymer matrix such as poly(methyl methacrylate) does not exhibit photochromism even though the system contains an appreciable amount of reductants. 

Low molecular weight substances offering a hi dipole moment, such as nitriles, amides, nitro compounds, etc., (Table 3) have a strong plasticization effect on poly-... 

Lai MC, Hageman MJ, Schowen RL, Borchardt RT, Laird BB, and Topp EM. Chemical Stability of Peptides in Polymers. 2. Discriminating between Solvent and Plasticizing Effects of Water on Peptide Deamidation in Poly(vinylpyrrolidone).yP/i(zm Sci 1999b 88 1081-1089. 

Poly(alk yl methacrylates), PS/BR Methanol, Toluene, DME The Tg of polymers varied because of residual solvent, possible due to the plasticizing effect, and thermal history. DSC [Brostrom et al., 1980]... 

Benzyl alcohol [100-51-6] is miscible with organic solvents apart from aliphatic hydrocarbons. It dissolves cellulose esters and ethers, fats, oils, alkyd resins, natural and synthetic resins, and colorants. Polymers—with the exception of lower poly(vinyl ethers) and poly(vinyl acetates)—are not dissolved. Small amounts of benzyl alcohol improve the flow and gloss paints, delay the evaporation of other solvent components, and have a plasticizing effect in physically drying paints. It is used in ballpoint pen inks. Benzyl alcohol reduces the viscosity in two-pack epoxy resin systems. 

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