BS EN 302-6-2004 pdf download.Adhesives for load-bearing timber structures Test methods Part 6: Determination of the conventional pressing time.
This part of EN 302 specifies a method for determining the conventional pressing time at three temperatures for adhesives for load-bearing timber structures.
This document is only intended for obtaining a reliable basis for comparison of conventional pressing time between adhesives. The method gives results which cannot be applied to the safe manufacture of timber structures without modifications for the influences of timber density/absorbency, moisture content, factory temperature and relative air humidity.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
EN 302-1:2004, Adhesives for load-bearing timber structures — Test methods — Part 1: Determination of longitudinal tensile shear strength.
EN 923:1998, Adhesives — Terms and definitions.
3 Terms and definitions
For the purposes of this part of EN 302-1:2004, the terms and definitions given in EN 923:1998 and the following apply.
3.1
conventional pressing time
shortest pressing time (expressed as the mean of 10 individual results) that gives a tensile shear strength of at least 4 N/mm2 at a given temperature
NOTE The test procedures are those descnbed in this document.
4 Principle
Standard beech lap joints are tested in tensile shear after various curing times until it is found that the strength has reached a value of 4 N/mm2.
5 Safety
Persons using this document shall be familiar with normal laboratory practice.
6 Apparatus
6.1 Temperature cabinet, capable of maintaining the air at a temperature of(15 ± 2) °C.
NOTE It is important to test the adhesive at this temperature although EN 386 specifies a higher temperature during the curing of structural adhesives.
6.2 Temperature cabinet, capable of maintaining the air at a temperature of (20±2) °C
6.3 Temperature cabinet, capable of maintaining the air at a temperature of (30±2) °C.
7 Procedure
7.1 Sufficient beech panels shall be prepared in accordance with EN 302-1:2004, Clause 6.1 to enable
12 sets each of 10 test specimens with (0,2 ± 0,1) mm glue lines to be manufactured.
7.2 After conditioning to (12 ± 1) % moisture content, the panels shall be divided into three equal groups and wrapped so that they are airtight, to prevent further change in their moisture content. Each group of the panels shall be transferred to an atmosphere at one of the test temperatures described in Table 1. The components of the adhesive system to be used shall also be stored under these three temperatures respectively.
7.3 After at least 12 h conditioning at the test temperature, the panels shall be glued and pressed. The test pieces shall not be removed from the test temperature during the pressing period. Unless otherwise stated by the manufacturer, the clamping pressure shall be 0,8 N/mm2 Table 1 gives the pressing time for each pair of panels.
NOTE 1 It is a common practice, before bonding is started, to store the adhesive components and the timber overnight at the specified temperature whereby the timber shall be packaged hermetically (air-tight) to prevent changes of moisture content,
NOTE 2 Because wood temperature is difficult to measure, It is a common practice to remove the test pieces from the conditioning cabinet immediately before applying the adhesive to them.
7.4 Immediately after the pressing time has elapsed, the panels shall be unclamped and 10 test specimens cut from each of the bonded panels according to EN 302-1:2004. Clause 6.2. They shall be tested according to EN 302-1:2004, Clause 6.5 without delay.
7.5 The conventional pressing time shall be calculated by linear interpolation of those pressing times and
their related tensile shear strength that are most near to the time corresponding to a tensile shear strength of
4 N/mm2. The tensile shear strength at the shortest pressing time for each temperature shall be less than
4 N/mm2. If needed, use shorter pressing times than those given in Table 1. The calculated conventional
pressing time shall be expressed to the nearest 15 mm rounded off to the next higher value.
EXAMPLE A pressing time ol 4 h pives a mean tensile shear strength of 3 N/mm2. while the mean tensile shear strength for 8 h pressing time is 6 NImm . The result of the linear interpolation for 4 N/mm2 is 5 h 20 mm. This calculated value will be rounded off to 5 h 30 min
8 Test report
The test report shall contain the following information:
a) a reference to this document (EN 302-6);
b) identification of the adhesive system tested:
c) proportions taken when mixing the adhesive for use;
d) value of the conventional pressing times for the three air temperatures respectively:
e) date of testing.BS EN 302-6-2004 pdf download.