Construction Panel Having Improved Fixing Strength

Abstract

A method of producing a gypsum product comprises the steps of: □preparing a stucco slurry; □adding starch-containing flour to the slurry in an amount of at least 2% relative to the dry weight of the stucco; and □allowing the stucco slurry to set.

Claims

1. A method of producing a gypsum product comprising the steps of: preparing a stucco slurry; adding starch-containing flour to the slurry in an amount of at least 2% relative to the dry weight of the stucco; and allowing the stucco slurry to set.

2. A method according to claim 1, wherein the flour is added in an amount of at least 4% relative to the dry weight of the stucco.

3. A method according to claim 1, wherein the flour is wheat flour.

4. A method according to claim 1, further comprising the step of adding fibres to the slurry.

5. A method according to claim 4, wherein the fibres are glass fibres.

6. A method according to claim 4, wherein the fibres are added in an amount of at least 1% relative to the dry weight of the stucco.

Description

DETAILED DESCRIPTION

[0025] The invention will now be described by way of example only.

[0026] Gypsum plasterboards were prepared using the following general methodology:

[0027] Stucco and other dry additives were weighed into a bag and shaken to mix them. Water and wet additives were weighed into a bowl and mixed using an electric mixer for 60 s.

[0028] The dry powdered additives were added to the wet additives in the bowl and mixed in with the electric mixer for 30 s.

[0029] The resultant slurry was sandwiched between two sheets of paper liner and allowed to hydrate for 25 minutes measured from the time of mixing. The board was then dried in an oven for 1 hour at 160° C.

[0030] The board thickness was 12.5 mm and the board density was 950 kg/m.sup.3.

EXAMPLE 1

[0031] A gypsum plasterboard was prepared from a slurry containing the following ingredients: [0032] stucco; [0033] wheat flour from Jackering in an amount of 6 wt % relative to the stucco; [0034] glass fibre in an amount of 2 wt % relative to the stucco.

COMPARATIVE EXAMPLE 1

[0035] A gypsum plasterboard was prepared from a slurry containing the following ingredients: [0036] stucco; [0037] corn starch (trade name: Merifilm) in an amount of 6 wt % relative to the stucco; [0038] glass fibre in an amount of 2 wt % relative to the stucco.

[0039] Fluidity

[0040] It was observed that the slurry prepared during Example 1 was more fluid than that prepared during Comparative Example 1.

[0041] Expansion with Humidity

[0042] Expansion with humidity was measured according to ASTM D1037 from initial conditions of 23° C. and 50% relative humidity to final conditions of 20° C. and 90% relative humidity. The samples were 200 mm long and 50 mm thick. The results are set out in Table 1.

TABLE-US-00001 TABLE 1 Expansion Example with humidity Example 1 0.052 Comparative 0.071 example 1

[0043] Screw Pull-Out Strength

[0044] Screw pull-out tests were carried out on samples measuring 100 mm by 100 mm that had been conditioned at a temperature of 23° C. and a relative humidity of 50%. A 50 mm single thread wood screw was inserted into the sample, passing through a metal load transfer element positioned on the surface of the sample. The load transfer element has a first portion that is configured to lie between the screw head and the surface of the sample, and a second portion that is configured to engage with a testing machine so as to allow a load to be applied to the screw along the axis of the screw. The screw was tightened to a torque of 1 Nm.

[0045] The specimen was then mounted in a Zwick Universal Testing Machine and a 10N pre-load applied to the screw along the axis of the screw. Subsequently, the load was increased by setting a constant cross-head speed of 10 mm/minute until pull out was achieved.

[0046] The results are set out in Table 2. These are averages, each taken from 8 samples.

TABLE-US-00002 TABLE 2 Average screw pull-out Example strength N Example 1 561 ± 58 Comparative 606 ± 65 example 1