Plasticizer absorption tests

Figure 12-4. Sigma-style mixer for plasticizer absorption test. (Courtesy of C. W. Braben-der Instruments, Inc.)...

Other Measurements. Other tests include free moisture content, rate of dissolution and undissolved residue in acids and alkaH, resin and plasticizer absorption, suspension viscosity, and specific surface area. Test procedures for these properties are developed to satisfy appHcation-related specifications. 

Typically, if oil absorption is low, the filler does not change the hot melt viscosity much. Because of this, oil absorption test is often used to characterize the effect of fillers on rheological properties of filled plastics. 

There arc several water absorption tests specified for plastics with various geometries and conditions. Generally they use times that would not result in equilibrium, and care needs to be taken in comparing results, particularly if surface area to volume ratios are different. Coated fabrics and textiles are normally relatively thin and hence there is less problem with very long times being needed to reach equilibrium. 

Designation system was developed for vinyl chloride thermoplastic resins which may be used as the basis of specification. In respect to plasticizers, the system allows to include in specification, plasticizer absorption at room temperature, viscosity of paste, and rheological behavior of paste. The second part of ISO standard gives a list of ISO standards used for testing of properties included in designation system and describes preparation of sample. 

Standard Test Method for Rubber Property - Vapour Transmission of Volatile Liquids Standard Test Method for Water Absorption of Plastics Standard Test Methods for Water Vapor Transmission of Materials... 

The need for more rapid evaluation of plastics and elastomers prompted the development of a sequential absorption test to provide useful information on the durability of these materials in a few weeks [34]. A refinement to this test was developed more recently [35,36]. 

PVC resins for general use—Determination of hot plasticizer absorption D 3367-75 (1989) Test method for plasticizer sorption of poly (vinyl chloride) resins under applied centrifugal force... 

Testing of phthalocyanines includes crystallization (qv), flocculation, and appHcation in paints, plastics (qv), and printing inks (1). The ASTM standard specifications include CuPc in dry powder form for various appHcations (153). The specifications cover color (qv), character or tint, oil absorption, reactions in identification tests, and dispersions and storage stabiUty. Quantitative deterrninations are possible with ceric sulfate (30) or sodium vanadate (154). Identification methods are given (155), including tests for different appHcations. 

Most of over six million dentures produced annually in the USA are made of acrylics (PMMAs) that includes full dentures, partial dentures, teeth, denture reliners, fillings and miscellaneous uses. Plastics have been edging into the dental market for over a half century. Even before the introduction of acrylics to the dental profession in 1937, nitrocellulose, phenol-formaldehyde and vinyl plastics were used as denture base materials. Results, however, were not wholly satisfactory because these plastics did not have the proper requisites of dental plastics. Since then, PMMAs have kept their lead as the most useful dental plastics, although many new plastics have appeared and are still being tested. Predominance of PMMAs is not surprising, for they are reasonably strong, have exceptional optical properties, low water absorption and solubility, and excellent dimensional stability. Most denture base materials, therefore, contain PMMA as the main ingredient. 

The moisture content of a plastic affects such conditions as electrical insulation resistance, dielectric losses, mechanical properties, dimensions, and appearances. The effect on the properties due to moisture content depends largely on the type of exposure (by immersion in water or by exposure to high humidity), the shape of the product, and the inherent behavior properties of the plastic material. The ultimate proof for tolerance of moisture in a product has to be a product test under extreme conditions of usage in which critical dimensions and needed properties are verified. Plastics with very low water-moisture absorption rates tend to have better dimensional stability. 

If a change occurs in the food product after storage in a plastic container, some part of the change could be caused by absorption in the container wall. The important components such as flavor oils or emulsifiers exist in relatively small quantities. The type and thickness of the polyethylene container can influence this variable. If the before and after taste test shows no difference between storage in the plastic container and storage in glass, absorption in the wall is considered insignificant. 

When water is used as the immersion liquid, the test is essentially the ASTM Standard Test Method (D570) for Water Absorption of Plastics.( ) Determinations of the relative rate of water absorption are important in evaluating the effects of moisture exposure on such properties as mechanical strength, electrical resistivity, dielectric... 

The antiinflammatory properties of such topical agents as halcinonide are usually determined by a vasoconstrictor assay. Topically applied corticosteroids cause a blanching at the site of application, which can be the forearm or the upper back of healthy adults where stratum corneum is removed with cellophane tape. ° The test areas, containing various concentrations of halcinonide, are occluded with plastic wrap and are evaluated on an all-or-none basis. Percutaneous absorption studies with 0.1%... 

The uses of IR spectra in identification, classification and mechanistic studies have been well documented. Tests for the identification of plastics utilized in Naval ordnance weaponry are discussed in Ref 21. Correlations between polymeric structure and ablative properties using IR spectroscopy have been obtained by monitoring changes in functional group absorption,properties.(Ref 12). The application of IR spectroscopy to the detection of more than 40 of the most common constituents of primers, tracers, igniters, incendiaries,... 

Although the perfume oil is usually the first suspect whenever odor or color changes occur in a finished product, it is not always the culprit. Odor and color changes in the product base itself may occur due to oxidation, hydrolytic breakdown, complex formation, bacterial decomposition, or other causes. Sometimes the causes for instability are hard to track down, as in a case in the experience of one of the authors, where an off-odor in a cream was due to microbial breakdown that was made possible by absorption and inactivation of the preservative by the plastic container. It is always advisable to conduct a stability test of the unperfumed product along with the test of the perfumed product. 

As a first step it is useful to test the interaction between the plastic and food simulants that differ as much as possible from the plastic in their polarities. A quick overview about the absorption behavior of the plastic is obtained by immersion of samples into olive or corn oil at the highest desired used temperature for 1-2 hours and then determining the amount of oil absorbed gravimetrically. 

In addition to those standardized tests, two other test methods, monotonic creep and microhardness, have been developed by Hough and Wright [48]. In the monotonic creep test, the strain response to a constant stress rate is monitored. The deviation of the stress-strain characteristics in air and in the fluid of interest is taken to be the initiation of ESC. This method is shown to differentiate to a high resolution between polymers, and in the short term, the ESCR of polymer/fluid pairs that exhibit mild/weak interactions can be distinguished. The microhardness method, in which a pyramidal diamond indentor is pressed into the surface of the polymer component at a known load and for a known time, has the potential for mass screening of plastic/fluid compatibility, including extraction as well as absorption, and should be of interest to polymer suppliers. 

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