Plasticity retention index

Plasticity Retention Index. The oxidation behavior of natural mbber may affect both the processing characteristics and final vulcanizate performance, and the plasticity retention index (PRI) test can be used to give an indication of both. Natural antioxidants present in natural mbber give some protection and a measure of the efficacy of protection is given by PRI. PRI% = P q j Pq x 100, where Pq is the initial Wallace plasticity and P q is the... 

There are some aspects in the raw dry NR grades for adhesive manufacturing to be considered. NR tends to suffer oxidative degradation catalyzed by metals (mainly copper). The susceptibility of NR to oxidation can be measured using the plasticity retention index. The better grades of rubber have the higher plasticity retention index. 

A convenient term for the rheological properties of an unvulcanised elastomer (see Rheology). It has been defined as the susceptibility to, and retentivity of deformation , and also the degree of flow which takes place under given conditions of temperature and pressure . The use of the term viscosity is a more appropriate description. Plasticity Retention Index... 

Abbreviation for plasticity retention index. Printers Blanket... 

In addition SMR is characterised by the plasticity retention index, which gives opportunity for close control of processing and properties. 

Plastic bags Plastic beads Plastic bearing materials Plastic cements Plastic drums Plastic electronic packagf Plastic encapsulant Plastic fibers Plastic films Plastic hardcoats Plasticity Plasticity index Plasticity retention index Plasticization... 

By weighing the first and last passes, the mill homogenization procedure is also use to measure volatile matter content. Samples are then allocated to such tests as are required in accordance with ISO methods. In particular, it is specified that volatile matter is measured according to the oven method of ISO 24813. Apparently, we have two measures of volatile matter Mooney viscosity and plasticity retention index are measured as discussed later in the chapter. Although the title and the procedure indicate that the method is intended for raw rubber, it is also specified that vulcanization characteristics are measured. 

For synthetic rubbers, the mill homogenization is generally omitted, although it is specified as an alternative where the appropriate evaluation procedure requires it before measuring Mooney viscosity. Different conditions are given for specific polymers. The mill method of ISO 248 for determining volatile matter is specified but the oven method may be substituted if the material sticks to the mill rolls. Regardless of which volatile matter method is used, the mill procedure is required to dry samples for any chemical tests needed - unless this is not possible. To the uninitiated at least, this is not a model of clarity. Vulcanization characteristics are determined for synthetic rubbers, but not plasticity retention index. 

Most ageing tests are carried out on vulcanised or thermoplastic compounds, but there has been a need to assess the oxidative effects of storage on natural rubber. Various accelerated procedures using ovens or infra-red lamps have been used with visual assessment of deterioration. A more satisfactory procedure based on the measurement of plasticity after oven ageing has been standardised as ISO 293033 and the result is known as the plasticity retention index. 

ISO 2930,1995. Rubber, Raw Natural - Determination of plasticity retention index (PRI). 

ASTM D3194, 2004. Test method for rubber from natural sources - Plasticity retention index (PRI). 

Solution adhesive is obtained from solid rubber obtained by coagulation of latex as acquired from the tree. The coagulation is effected by dilute aqueous solution of organic acids. The solid rubber can be graded in terms of dirt content, ash content, nitrogen content, and volatile matter. It can also be categorized by plasticity retention index and Mooney viscosity. To maintain uniformity it is necessary to choose solid natural rubber of known characteristics. 

NR, as a specific example is often selected according to its oxidation resistance. This may be assessed by measurement of its plasticity retention index (where Wallace rapid plasticity is measured before and after heat ageing at 140 °C, e.g., ASTM D3194-99 [21]). The drop in plasticity found after ageing is an indicator of this polymer s oxidation resistance. 

ASTM D3194-99, Standard Test Method for Rubber From Natural Sources-Plasticity Retention Index (PRI), 1999. 

V erformung sfahigkeit, Deformationsfahigkeit plasticity retention index (PRI) Plastizitats-Retentionsindex plasticization/plastification Weichmachung... 

The plasticity retention index (PRI) is a measure of the susceptibility of the raw rubber to oxidative degradation. Oxidation is catalyzed by some metals such as copper, so that the PRI test gives an indirect indication of the presence... 

The effect is examined of tetramethyl thiuram disulphide (TMTD) on the heat ageing and oxidation of clay-filled NR, with reference to the plasticity retention index of NR, using thermal analysis and scanning electron microscopy test methods. The results showed that heat and oxygen resistant properties could be obtained when the clay-filled natural rubber compound was cured by semi-effective or effective curing systems, with 1.5 phr or 3.0 phr of TMTD. 3 refs. 

---