Plasticizers monomeric, migration

Migration of ions through the plasticizer is frequently considered to be a function of the mobility of the plasticizer itself (2,5). In many electrical applications, where fugitive monomeric plasticizers like DOP can cause damage, they can be replaced by non-fugitive polymeric plasticizers such as viscous liquid polyesters. Comparison of DOP vs. a typical polymeric plasticizer, Rohm Haas Paraplex 0-25 poly (propylene sebacate), showed no significant improvement in volume resistivity (Table VI), particularly when its lower plasticizing efficiency was considered. Thus plasticizer mobilitv alone does not help us explain volume resistivity (5). 

The polymeric plasticizers are used where permanence is of prime importance. The molecular weights of these plasticizers vary quite extensively. Variations from under 850 to 8000 are not uncommon. The cost of polymeric plasticizers is usually in excess of that of the normal monomeric types. Resistance to extraction by soapy water, oils, and migration into nitrocellulose, polystyrene, and rubber are usually superior with polymeric plasticizer systems. Because of their higher viscosities, they are usually more difficult to handle. 

In practice, esters from adipic, sebacic, and phthalic acid are frequently used as polyester plasticizers. The value of n may vary from 3 to 40 for adipates and from 3 to 35 for sebacates. Polyester plasticizers are seldom used alone. They are used in combination with monomeric plasticizers to reduce the volatility of the mixed solvents. They offer a higher resistance to plasticizer migration and to extract by kerosene, oils, water, and surfactants. Polyester plasticizers are used specially in PVC-based blends and in nitrocellulose varnishes. 

The main drawback of monomeric plasticizers is their tendency to migrate from the polymer or to be leached out by contacting media. In anticipation of permanence problems caused by monomeric plasticizers, oligomeric... 

Polymeric plasticizers already have established their superiority over monomeric or low molecular weight plasticizers because these display less volatility and more resistance to solvent and oil extraction, good permanence, and slight migration to other materials as compared to conventional monomeric plasticizers. These are materials incorporated in a plastic or a resin in order to impart flexibility, reduce viscosity, and improve light stability, corrosion resistance, and water permeability of the resin. For better compatibility, mixtures of monomeric and polymeric plasticizers are used. 

Because of lower efficiency than a monomeric plasticizer and higher costs, polymeries are used frequently in combination with phthalates to improve migration resistance and oil extraction characteristics over the phthalate system. Upholstery and aircraft seating subject to extraction by body or hair oil are examples of useful applications. Refrigerator gasketing, electrical tape, decals, and oil-resistant electrical wire use high levels of polymeries frequently as the sole plasticizer (5). 

An adhesive is a linear or branched amorphous polymer above its Tg. It must be able to flow on a molecular scale to grip surfaces. (This definition is not to be confused with polymerizable adhesive materials, present in monomeric form. These are tacky or sticky only in the partly polymerized state. Frequently they are cross-linked thermoset, finally. Contact with the surface to be adhered must be made before gelation, in order to work.) An example is the postage stamp adhesive, composed of linear poly(vinyl alcohol), which is plasticized by water (or saliva) from below its Tg to above its Tg. On migration of the water away from the adhesive surface, it sticks. ... 

Kawakami and Sonoda reported on a similar system in 1993 [72]. They used PVK as photoconductive polymer and TNF as a sensitizer, too. The system also included a plasticizer and the non-linear optical dye 1 -cyano-2(4-dimethylaminophenyl) acrylic acid. Unfortunately, the 40-50 pm layers prepared by blade casting showed diffraction maximum efficiency of which was only 4 X lO . Furthermore fading of colour in the irradiated areas was observed. It was concluded that the monomeric dye migrates within the polymer and reacts photochemically. 

Resistant to migration into adhesives and other plastics in contact with vinyl. Migration resistance to adhesives from vinyl is important for applications such as decals or electrical tapes. Monomeric plasticizers are not nearly as resistant to migration to adhesives on vinyl films as polymeric plasticizers. 

The use of 30 phr of 33 percent ACN NBR greatly reduces plasticizer migration into, or chemical stresscracking of, polystyrene, acrylics, ABS, or rigid PVC. Levels below 20 phr do not have a useful effect. Typically, 30 phr is used, replacing 5-10 phr monomeric plasticizer. 

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