Outgassing specific rate

The walls of a vacuum system have a surface area of 4 m2. The specific outgassing rate ( lh) is 4 x lO PanPs-1 m-2 and a = 1. If it is assumed that there are no other significant gas sources, calculate the pumping speed necessary to achieve lO mbar after 55 min. 

Polymer applications of DSC are numerous and concern the determination of Tm (ASTM E 794), Tg (ASTM E 1326-03, ISO/FDIS 11357-2), specific heat capacity of a material (ASTM E 1269, ASTM D 4816), crystallisation temperature upon cooling (ASTM E 794), transition temperatures (ASTM D 3418, ASTM D 4419, ASTM D 4591), purity of a material [79,80], contamination outgassing (ASTM E 1559), reaction rates, sample composition, reaction kinetic constants (ASTM E 698), reaction mechanisms, thermal stability (ASTM E 537), minimum processing temperatures, heat of fusion and crystallisation (ASTM D 3417), heat of crystallisation (ASTM E 793), additive effects on a material, quality control of raw materials [25], discrimination between materials, detection of polymorphism [81], characterisation of thermally and UV cured materials (cure state, degree of cure) (ASTM D 2471, ASTM D 5028), oxidative stability testing, QIT (ASTM D 3895, ASTM D 3012, ASTM E 1858-03), etc. 

The vapor pressure of materials as well as the desorption rate of adsorbates increase with rising temperature. Therefore, once closed, UHV chambers are subjected to a bake-out procedure, that is, the whole vacuum system is heated to 150-250 °C for many hours while pumping. Likewise, filaments and the samples themselves have to be preheated to temperatures higher than in the following experiments in order to outgas unwanted contaminants (specific sample cleaning, see Section 3.1.4.1). Obviously, bake-out and outgassing temperatures put constraint on the materials that can be used for and in a UHV system. 

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