Plasticizers glass transition point

In selective separation of hydrocarbons from their mixtures with air or from their aqueous solutions, it makes sense to use membranes based on rubbery polymers, whose permeability increases with the decrease in glass transition point. Permselectivity of rubbery polymers is dominated by the sorption component, which increases with condensability of the hydrocarbon penetrant. Higher activity of the component being separated in the feed mixture results in plasticization of the membrane and can make it swell. This can produce a non-monotonic dependance of selective properties of the membrane on activity of the component being separated. As a rule, permselectivity for mixtures of penetrants is significantly lower than their ideal values. Negative values of sorption heat of easily condensable hydrocarbons can result in existence of non-monotonic temperature dependencies of mass transfer coefficients. 

Polyethylene is a semicrystalline polymer. It means that at ambient temperatures the polymer consists of two rather distinct fractions, or phases—crystalline and amorphous. The amorphous part of polyethylene, which is a sort of rubbery at ambient temperatures, becomes a glass-like at a certain transition temperature, the so-called glass transition point. For polyethylene the glass transition point varies from very low to low (from -130 to 20°C), thus making the plastic ductile at common temperatures. The lower glass transition point (y-transition) is always present in the range of -130 to -100°C, the higher one (P-transition, at —20°C) is manifested not in all PE materials. To complicate the picture even more, we can notice that there is one more transition in polyethylenes, called a-transition, commonly found between 10 and 70°C, and it is associated with crystallinity of PE. For WPC the last two transitions (a- and P-) are of little importance. 

Polymerization in Polymeric Glasses (10, 11). Poly (vinyl chloride) (PVC) films 0.35 mm. thick were used as a matrix. The pure polymer has a glass transition point at ca. +80°C. When soaked in a monomer at room temperature PVC swells slightly and softens. This plasticized polymer vitrifies again at low temperature. 

Energy elastic behaviour (glass state). Application range of the plastic Glass transition icmpeniturc> phase transition point. Transition to thcnnoclastic range. 

See also electronic plastic glass transition temperature heat distortion point IEEE thermal ratings continuous-use temperature. 

The recycling of the process water from a hardboard mill utilizing hardwoods has resulted in sticking of the boards at the press (36). In some cases the cause may be the thin layer of hemicelluloses, which under wet conditions and with heat from the rolls have passed the glass transition point to become plastic so that the paper web from semichemical pulps sticks to the rolls. The addition of a mixture of solvents, dispersants, and emulsifiers to NSSC pulps can control deposit formation at the wet end of the machine (56). 

For the purposes of this paper, plasticizers (which are usually associated with liquid additives, e.g. petroleum oils) are specific types of process aids used in unvulcanized rubbers to reduce viscosity. Other plasticizers, for example of the ester type, may be used in synthetic rubbers for other reasons such as the lowering of the glass transition point for low-temperature applications. 

Plasticity is the quality of being deformed permanently by a small force. When plasticizer is added to various kinds of binder, the glass transition point and melting point of the resin falls, giving it flexibility and making it easy to shape. The following qualities are required of the plasticizers for green sheets used in LTCCs. 

The dynamic mechanical properties of VDC—VC copolymers have been studied in detail. The incorporation of VC units in the polymer results in a drop in dynamic modulus because of the reduction in crystallinity. However, the glass-transition temperature is raised therefore, the softening effect observed at room temperature is accompanied by increased brittleness at lower temperatures. These copolymers are normally plasticized in order to avoid this. Small amounts of plasticizer (2—10 wt %) depress T significantly without loss of strength at room temperature. At higher levels of VC, the T of the copolymer is above room temperature and the modulus rises again. A minimum in modulus or maximum in softness is usually observed in copolymers in which T is above room temperature. A thermomechanical analysis of VDC—AN (acrylonitrile) and VDC—MMA (methyl methacrylate) copolymer systems shows a minimum in softening point at 79.4 and 68.1 mol % VDC, respectively (86). 

The results of tests on the polymers A, B, C, D are plotted versus the absolute temperature in Fig. 3.1 in order to facilitate comparison with Eq. 3.1. Tests on polymer E were spoilt by plastic deformation. Straight lines were drawn through the points in Fig. 3.1 and through the origin (T = OK). Such lines correspond with the Eq. (3.1). At temperatures below the glass transition where the polymers... 

Plasticizers and Copolymerization also shift the glass transition responses of the amorphous phase of crystalline polymers. In addition, the degree of Crystallinity and melting point are lowered. The resulting effects on the... 

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