Plasticizer content

As weU as imparting improved fire retardancy these materials may also result ia volume cost savings if they can be purchased for a lower price than the commodity phthalate. Precise knowledge of the compatibiHty between standard plasticizers and chlotinated paraffins is requited because some mixtures become iacompatible with each other and the PVC resias ia use at certain temperatures. Phthalate—chlotinated paraffin compatibiHty decreases as the molecular mass of the phthalate and the plasticizer content of the PVC formulation iacrease. Many compatibiHty graphs are available (1). 

The plasticizer content of a polymer may be increased by the suppression of crystallization in the polymer, but if crystallization subsequently occurs the plasticizer exudes. For highly crystalline resins, the small amounts of plasticizer allowable can change the nature of the small amorphous regions with a consequent overall change in properties. 

Addition of a plasticizer decreases the Tg of the polymer and, in partially crystalline polymers, also influences both crystallization and melting. The amount of plasticizer affects its effectiveness. Thus, while the Tg of the polymer is strongly depressed by small plasticizer additions, the increase in the plasticizer content leads to lower decrease in To and in several systems two T values can be found [36J. Therefore, the increase in the plasticizer content in polymers does not show a monotonic decrease in Tg. 

Aside from ion content, a wide range of properties is available in ionomers by control of various processing variables, such as degree of conversion (neutralization), type of counterion, plasticizer content and thermal treatment. Various examples illustrating possible effects of these variables on mechanical relaxation behavior and on such mechanical properties as stiffness, strength, and time- or energy-to-fracture have been given. 

Chemorheology is concerned with the chemical kinetics and the associated flow properties of a model reacting system. Energetic composite rheology is a continuously evolving process. The initial slurry viscosity is determined by the system temperature, plasticizer content... 

Figure 8 CTPB viscosity as a function of temperature and plasticizer content.

Concerning the PBDEs content in computers, no specific information about this compound has been found. Therefore, since computers belong to the category 3, the PBDE content of this category presented in Sect. 2 (Table 2) has been assumed as the one in computers. The considered value is 28.03 g/kgPlastic, it is the result of the sum of the content of the different PBDE congeners in appliances from Table 2 (appliances produced before 1998 as conservative scenario). In addition the plastic content in a computer is around 22.99% based on Puckett et al. [3]. 

The main classes of plasticizers for polymeric ISEs are defined by now and comprise lipophilic esters and ethers [90], The regular plasticizer content in polymeric membranes is up to 66% and its influence on the membrane properties cannot be neglected. Compatibility with the membrane polymer is an obvious prerequisite, but other plasticizer parameters must be taken into account, with polarity and lipophilicity as the most important ones. The nature of the plasticizer influences sensor selectivity and detection limits, but often the reasons are not straightforward. The specific solvation of ions by the plasticizer may influence the apparent ion-ionophore complex formation constants, as these may vary in different matrices. Ion-pair formation constants also depend on the solvent polarity, but in polymeric membranes such correlations are rather qualitative. Insufficient plasticizer lipophilicity may cause its leaching, which is especially undesired for in-vivo measurements, for microelectrodes and sensors working under flow conditions. Extension of plasticizer alkyl chains in order to enhance lipophilicity is only a partial problem solution, as it may lead to membrane component incompatibility. The concept of plasticizer-free membranes with active compounds, covalently attached to the polymer, has been intensively studied in recent years [91]. 

Fig. 29 Dispersion of Pigment Violet 19, -modification, in PVC on a roll mill in relation to the plasticizer content (DOP) and the dispersion temperature.

To ensure good dispersion of the pigments in a preparation and subsequently good distribution in the end product, it is necessary to increase the flowability of the preparation above that of the plastic being colored. This is achieved by using a carrier material with a low molecular weight (wax), a copolymer or increased plasticizer content. 

A reduction in the plasticizer content leads to a better degree of dispersion at a given temperature owing to an increase in viscosity of the plasticized plastic, but even in plasticizer-free PVC complete dispersion of the pigment is not achieved on the roll mill under the dispersion conditions chosen. 

The transverse resistivity of plasticized PVCs decreases as the plasticizer content increases. 

Plasticizers. Compounds added to high molecular weight polymers to give them flexibility, softness, and stretch. Plasticizers can be added mechanically at the compounding or shaping stage or chemically by copolymerization. For example, dioctyl phthalate is mechanically added to PVC vinyl acetate is copolymerized with PVC. Plasticizer content can vary from 5—40%. 

So far, most of the experimental studies have been limited to fully polymerized samples or samples with a high plastic content. That is because the earlier Interest was mainly focused on the effect of properties of the constituents, such as crosslink density and miscibility, ease of TEM studies, etc. 

The Poisson s ratio (A//Aw, where A/ is the change in length produced by a change of width, Aw) of an isotropic liquid is 0.5, and that of an elastic solid is about 0.2. The value of P for an elastomer, such as NR, is 0.5, and this value decreases as the elastomer is cured with increasing amounts of sulfur, i.e., as the crosslink density increases. Likewise, P for rigid PVC is about 0.3, and this value increases progressively as the plasticizer content is increased. 

Creep rates of three glassy polymers are much greater during electron irradiation than before or after. Radiation heating is eliminated as a possible cause. Essentially the same concentration of unpaired electrons and ratio of cross-linking to scission were found in polystyrene samples in the presence or absence of stress. The effects of radiation intensity, stress, and temperature on creep during irradiation are examined. The accelerated creep under stress is directly related to a radiation-induced expansion in the absence of stress. This radiation expansion is decreased by increase in temperature or plasticizer content and decrease in sample thickness. It is concluded that gas accumulation within the sample during irradiation causes both the expansion under no stress and the acceleration of creep under stress. 

The above experiment on the effect of plasticizer content was repeated at 35.5° instead of 23.5 °C. The accelerating effect of radiation on the creep rate of stressed samples again appears to disappear at about the same plasticizer content where the expansion of the unstressed samples disappears however, both vanish at a lower plasticizer concentration (approximately 20% ) at 35.5° than at 23.5°C. Hence, we can conclude that an increase in temperature also diminishes the acceleration of creep rate caused by the radiation. 

Figure 13. Effect of plasticizer content on creep rate or unstressed expansion of polystyrene during irradiation at 23.5°C.

An irradiation-induced expansion could conceivably be caused by the ions, formed as precursors of the radicals, or by thermalized electrons trapped within the polymer. Irradiation induces electrical conductivity in polymers, and this conductivity decays after irradiation is ceased (4, 5). The decay process is accelerated by increased temperature or plasticity of the specimen, presumably by facilitating leakage of the trapped electrons or ions to ground. One might speculate that the sample expands upon irradiation because of the local mutual electrical repulsions of like charges which are trapped in the polymer matrix, and that both increased temperature and plasticizer content diminish this expansion because of charge leakage out of the specimen. It is difficult to prove or disprove this hypothesis. 

If the gases which accumulate within the specimen cause the free volume to expand, thus leading to both radiation expansion under no stress and radiation acceleration of creep under stress, one would expect these effects to be diminished by conditions which enhanced gas diffusion out of the sample. Such conditions would include lower sample thicknesses and higher temperature or plasticizer content. 

Figure 5b. According to the plasticizer content a shift to lower temperatures occurs, corresponding with a decrease of the glass temperature.

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