BS EN ISO 7808:1999 pdf free.Plastics – Thermosetting moulding materials – Determination of transfer flow.
BS EN ISO 7808 specifies a method for measuring the transfer flow of thermosetting moulding materials during a specified moulding process. It is intended only for production control and should not be used as part of a mandatory material specification.
2 Principle
The method determines the percentage mass of moulding material that is transferred through two apertures in the punch of a disc mould during a moulding process carried out under defined conditions.
3 Apparatus
3.1 Balance, to weigh 50 g to within ± 0,1 g.
3.2 Hydraulic press, with a capacity of at least 125 kN, fitted with a controlled variable pressure-reducing valve. The press closing time, between loading the powder into the mould until pressure first shows on the gauge, shall not exceed 10 s.
The final speed of closure shall be adjusted so as to avoid displacement of powder from the mould.
3.3 Moulding tool (see Figure 1), the moulding cavity of which has a diameter of 90 mm and a depth of 25 mm ± 5 mm (the depth of the cavity may be increased if necessary to accommodate bulky materials). The punch shall have two recesses 2,45 mm ± 0,01 mm deep and 7,5 mm ± 0,5 mm high diametrically opposite each other; their profile is shown in detail A of Figure 1.
The clearance between the male and female mould parts shall not exceed 0,05 mm (moulds wear with use and the tolerance should be checked frequently).
4 Test portion
The test portion shall be a 50 g ± 0,5 g portion of a sample of the moulding material to he tested.
5 Procedure
5.1 Adjust the temperature of the mould (see 3.3) to the value specified in Table 1 for the particular material to be tested.
5.3 Place the test portion (see clause 4) inside the mould cavity and immediately close the press (3.2).
5.4 Allow sufficient time for the material to cure, open the press, remove the moulding, detach the extrudate, allow the moulding to cool to room temperature and then weigh it to the nearest 0,1 g.
5.5 Calculate the transfer flow of the test portion as described in 6.1. Repeat the test until the numerical values of two consecutive transfer flows so obtained do not differ by more than 10 % of the numerical value of their mean.BS EN ISO 7808 pdf download.