Performance grading

Modification of physicochemical property of the existing excipient has been the most successful strategy in the development of new excipients in the past three decades (24). This model has been successfully adopted for the introduction of excipients with better performance grades, such as pregelatinized starch, croscarmellose sodium, and crospovidone (25). However, the quantum of functionality improvement is limited due to a restricted range of possible modifications. 

Native and microcrystalline cellulose precoated plates are used in the life sciences for the separation of polar compounds (e.g. carbohydrates, carboxylic acids, amino acids, nucleic acid derivatives, phosphates, etc) [85]. These layers are unsuitable for the separation of compounds of low water solubility unless first modified, for example, by acetylation. Several chemically bonded layers have been described for the separation of enantiomers (section 10.5.3). Polyamide and polymeric ion-exchange resins are available in a low performance grade only for the preparation of laboratory-made layers [82]. Polyamide layers are useful for the reversed-phase separation and qualitative analysis of phenols, amino acid derivatives, heterocyclic nitrogen compounds, and carboxylic and sulfonic acids. Ion-exchange layers prepared from poly(ethyleneimine), functionalized poly(styrene-divinylbenzene) and diethylaminoethyl cellulose resins and powders and are used primarily for the separation of inorganic ions and biopolymers. 

Another recent development has been the introduction of Polyethersulphone with performance at temperatures higher than that of the 300P grade. One of these high performance grades,... 

In many respects PES is an ideal material for use in electrical connectors as it can be moulded to close tolerances and maintains structural and electrical integrity to high temperatures. Multipin connectors based on a jdnstic dielectric retention system for use in supersonic aircraft and where a 10,000 hour lifetime at 400°F is required,are a possible application for the high performance grade 720P. 

The extensive Strategic Highways Research Program, completed in the United States in 1993, concluded in performance graded (PG) specifications for bitumens (asphalt binders) known as Superpave (superior performing pavements) specification. These specifications were first introduced by Asphalt Institute (Asphalt Institute SP-1) and soon became an AASHTO standard (AASHTO M 320) and ASTM standard (ASTM D 6373 2007). 

The specified properties per performance grade asphalt binders (bitumens) are given in Table 3.8. A similar table is also provided by ASTM D 6373 (2007), which incorporates practice D 6816 (2011) for determining the critical low cracking temperature using a combination of test method D 6648 (2008) and test method D 6723 (2012) test procedures. According to ASTM D 6373 (2007), if no table is specified, the default is Table 3.8. 

Source Reprinted from ASTM D 6373, Standard specification for performance graded asphalt binder, West Conshohocken, Pennsylvania, US ASTM International, 2007. With permission ( ASTM International). 

Asphalt Institute SP-1.2003. Superpave Performance Graded Asphalt, Binder Specification and Testing, 3rd Edition. Lexington, KY Asphalt Institute. 

ASTM D 6816. 2011. Standard practice for determining low-temperature performance grade (PG) of asphalt binders. West Conshohocken, PA ASTM International. 

The rotational viscometer test is specified by ASTM D 6373 (2007) as a standard test for performance-graded asphalt binders and is carried out at 135°C. 

ASTM D 6373 (2007), for performance-graded bituminous binders, requires that the creep stiffness [S (t) or S t)] does not exceed 300 MPa at 60 s and the m-value is SO.300, at any test temperature. 

This section summarises the tests required by ASTM 6373 (2007) or AASHTO M 320 (2010) for performance-graded bituminous binders, also known as Superpave tests (Asphalt Institute SP-1 2003). 

Table 4.2 Performance-graded asphait binder tests...

AASHTO M 320.2010. Performance-graded asphalt binder. Washington, DC American Association of State Highway and Transportation Officials. 

The asphalt cement binder should conform to ASTM D 6373 (2007) (performance grade) or ASTM D 3381 (2012) (viscosity grade), to ASTM D 946 (2009) (AASHTO M 320 2010)... 

The binder should be selected on the basis of ambient temperature, traffic and the expected functional performance of the OGFC mixture. The selected bituminous (asphalt) binder should satisfy the requirements of ASTM D 6373 (2007) (performance-graded asphalt binder). However, other grades of asphalt binders, such as penetration grade (ASTM D 946 2009) or viscosity grade (ASTM D 3381 2012), may be suitable. 

A performance grade of binder should be selected in accordance with Section 5 of A ASHTO M 323 (2013) considering the environment and the traffic volume at the project site. 

Isotropic pitches are used to make a general purpose (GP) grade of pitch carbon fiber, which is not graphitic and has poorer properties than the high performance grade (HP), which requires a special treatment process to convert the pitch to a mesophase grade, i.e., an optically anisotropic and graphitic material. 

---