Technical field

The present invention relates to building material comprising a polyolefin mesh. Background art In the building industry, the development of improved cementitious building materials and method of making thereof continues. There are many studies of the improvement of flexural strength, impact strength, good appearance, and no early stage cracking.

EP2649252A2 disclose a reinforced cementitious board system comprising a core layer made of a cement composition and a coated fiberglass mesh or scrim on the opposing surfaces of the cement core to be embedded on or slightly into the cementitious core in the opposed planar surfaces of the core layer.

CN2041261 15U disclose a steel wire mesh cement wallboard comprising a board body, a wire mesh embedded into the board body and a layer of fiberglass mesh bonded on the upper surface of the board body.

Fiberglass has disadvantage of lacking resistance to alkali attack from the ingredients of cements, gypsum and plaster. To protect the fiberglass from degradation in these highly alkali condition, polymeric coatings have to be applied to the fiberglass. The integrity of the coating on the fiberglass is critical to the success of the building material. Furthermore, the coating rapidly degrades with heat, which typically occurs during the curing cement, gypsum and plaster. The fiberglass mesh is a woven material which lacks the shape stability of an extruded mesh and the ability to return to its original shape after the application of shear force.

The main disadvantage of steel mesh is sensitive to moisture which causes rust and thus decreasing in physical and mechanical properties of the steel wire mesh. Also, the steel mesh has high weight per area which leads to higher transportation cost and difficult to carry. In addition, steel is stiff so it is difficult to mold against existing freeform shapes and tends to spring back to its original form.

In addition, both fiberglass mesh and steel mesh are difficult to installation, high cost for both material cost and installation cost. Furthermore, they are quite not safe because they are broken into very small and sharp piece which can be harmful. It is therefore the object of the present invention to provide a building material comprising a polyolefin mesh which can increase the crack resistance of a brittle matrix and has high resistance to impact and increased flexural strength. In addition, the polyolefin mesh also has several advantages over the steel mesh and fiberglass mesh e.g. easy and quick installation to building material, lighter weight, easy to carry, safer, lower material and installation cost.

Summary of the invention

The present invention related to a building material comprising a polyolefin mesh, wherein the polyolefin mesh is arranged inside the building material and/or on at least one surface thereof. Brief description of the drawings

Figure 1 (a) shows cracking after accelerated cracking testing of the plaster without mesh.

Figure 1 (b) shows cracking after accelerated cracking testing of the plaster with steel mesh.

Figure 1 (c) shows cracking after accelerated cracking testing of the plaster with PP mesh having mesh size of 2 mm. Figure 2 (a) shows the appearance after Schmidt Hammer testing of the plaster without mesh.

Figure 2 (b) shows the appearance after Schmidt Hammer testing of the plaster with PP mesh having mesh size of 2 mm.

Figure 3 shows flexural strength of the plaster without mesh and the plasters supported by PP mesh, fiber glass mesh and steel mesh. Detailed description

The following details describe the specification of the invention.

The invention relates to a building material comprising a polyolefin mesh, wherein the polyolefin mesh is arranged inside the building material and/or on at least one surface thereof.

The term 'polyolefin' refers to any polymerized olefin, which can be linear, branched, cyclic, aliphatic, aromatic, substituted, or unsubstituted. The term 'building material' refers to any material which is used for construction purposes including naturally occurring substances, synthetic substances, man-made products, and building products.

In one embodiment, the polyolefin mesh preferably comprises polyolefin fibers extending in two directions and mesh-gaps.

In another embodiment, the mesh-gaps can be in various shapes such as square, rectangular, trapezoid, triangle or circle, preferable square mesh-gaps.

In preferred embodiment, the polyolefin mesh has a mesh size in a range of 0.2 - 2 cm, more preferably 0.5 - 2 cm. Smaller mesh size than 0.2 cm can cause the delamination between mesh and the building material. Larger mesh size than 2 cm can cause lower reinforcement for the building material because the distance between polyolefin fibers is too large to reinforce the building material appropriately.

In one embodiment, the thickness of the polyolefin fiber is preferably in a range of 0.2 - 0.7 mm, preferably 0.2 -0.3 mm. Higher thickness than 0.7 mm can cause the delamination between mesh and building material. Lower thickness than 0.2 mm make the polyolefin fiber can be torn easily.

In further embodiment, the polyolefin mesh comprises mesh knots. The thickness of mesh knot is in a range of 0.7 - 1.2 mm. Mesh knot acts as fixture to lock the position of mesh when it is installed inside building material and also reinforce the building material. In one embodiment, the polyolefin mesh is made from polyolefin.

In preferred embodiment, the polyolefin has a melt flow index (MI) in a range of 2-3 g/10 min. According to the invention, the melt flow index is determined according to ASTM D 1238.

In further preferred embodiment, the polyolefin has a flexural modulus (according to ASTM D 790) within a range of 10,000 to 20,000 kg/cm ² , more preferably 13,000 to 15,500 kg/cm ² .

A melt flow index and/or a flexural modulus in the preferred ranges results in a polyolefin suitable to form a mesh having an appropriate size and high strength. In one embodiment, the polyolefin is preferably selected from polyethylene (PE), polypropylene (PP), or mixture thereof, preferable polypropylene.

In one embodiment, the polyolefin can contain a wide variety of additives. For instance, the polyolefin can include processing aids, antioxidants, antiozonants, ultra violet light stabilizers, heat stabilizers, biocides, antifungal agents, viscosity modifiers, reinforcing additives, strength enhancers, colorants, pigments, and the like.

In one embodiment, the building material is preferably but not limited to Portland cement-based plaster or concrete, Portland cement-based board, gypsum-based plaster or plasterboard, any form of masonry units and jointing compounds, and solid and corrugated plastic boards and corresponding jointing compounds.

The invention relates in a preferred embodiment to a Portland cement or gypsum board comprising a polyolefin mesh, wherein the polyolefin mesh is arranged inside the Portland cement or gypsum board and/or on at least one surface thereof.

The invention relates in a preferred embodiment to a plaster wall comprising a polyolefin mesh, wherein the polyolefin mesh is arranged inside the plaster wall and/or on at least one surface thereof.

In one embodiment, the plaster wall comprising a polyolefin mesh is preferably prepared by (1) Plastering wall, (2) Installing polyproylene mesh (PP Mesh) on the wet plaster and/or directly nailed to the substrate, regardless of whether it is a Portland cement or gypsum board or a masonry wall. In preferred installation, the filament direction of PP mesh is aligned with the crack direction and/or potential crack forming direction, (3) Plastering on PP mesh and (4) Set and dry under ambient conditions.

The present invention will now be described in further detail with the following examples. However, these examples should not be construed as limiting the scope of the present invention.

Preparation of plaster samples

Plastering samples without mesh and with various mesh types as shown in Table 1 and Figure 1 - 3 are prepared as follows, 1. Mix one part by volume of a masonry cement with two parts by volume of sand. The sand is prepared by mixing sand size no. 50 and 100 at the ratio of 1 : 1

2. Put the mixture of step 1 in the first plexiglass mould (width 30 cm x length 30 cm) and leveling the mixture to be flush with the first plexiglass mould.

3. For the plaster samples having mesh, placing mesh on the plaster prior to set and trowel the surface smooth in order to have the mesh embeded into the wet plaster that was placed in step 2.

4. Put the second plexiglass mould on the first plexiglass mould.

5. Put the mixture of step 1 in the second plexiglass mould and trowel the mixture to be flat, smooth, and flush with the second plexiglass mould.

6. The plaster was set and dry at ambient condition for 7 days.

The polypropylene mesh (PP mesh) used in the present invention was made from a polypropylene having a melt flow index (ASTM D1238 at 230°C, 2.16 kg) 2.4 g/10 min and flexural modulus (ASTM D790) 14,250 kg/cm ² . The PP mesh was prepared by extruding PP at temperature in the range of 230°C to 250°C through die to form mesh. Then, the mesh is stretched in both directions (machine direction (MD) and transverse direction (TD)) to achieve required mesh size.

The inventive samples are the plasters supported by PP mesh having square mesh-gaps and mesh size 2 mm (PP 2 mm), 6 mm (PP 6 mm) and 20 mm (PP 20 mm).

The comparable samples are the plaster supported by fiberglass mesh having square mesh-gaps and mesh size 0.5 cm and the plaster supported by steel mesh having square mesh- gaps and mesh size 0.5 cm.

Example 1:

Accelerated cracking test

The samples as table 1 are prepared according to step 1 to 5 as described above. Then, when the plaster samples are setting, the drying process is accelerated by using a fan to blow across the exposed top surface of the plaster samples for 3 days. This will accelerate the development of drying shrinkage of the plaster samples. Crack width was measured by using crack comparator.

Table 1 shows crack width of the plaster samples supported by PP mesh (Samples 3 - 5) is less than plaster sample without mesh (Sample 1) and the plaster sample with steel mesh (Sample 2).

Figure 1 (a), (b) and (c) show the appearance of the plaster sample without mesh (Sample 1) and the plaster sample with steel mesh (Sample 2) having badly cracked whereas the appearance of the plaster sample with PP mesh size 2 mm (Sample 5) having not badly cracked.

Table 1 Crack width of plaster samples without mesh and with various mesh types

Example 2:

Impact resistance test (Schmidt Hammer test method)

The samples as table 2 prepared according to step 1 to 6 as described above are tested by using Schmidt Hammer test method according to ASTM C 805.

Table 2 shows the rebound number of Schmidt Hammer test method. Higher rebound number, higher resistance to impact of the plaster samples. The plaster samples with PP Mesh 20 mm (Sample 3) and 2 mm (Sample 5) have higher resistance to impact than the plaster without PP mesh (Sample 1).

Moreover, Figure 2 (a) and (b) show the appearance after Schmidt Hammer testing. The plaster without mesh (Sample 1) scatters after test whereas the plasters with PP mesh 2 mm (Sample 5) still remain the shape of plaster. Table 2 Rebound number of plaster samples without mesh and with PP mesh

Example 3: Flexural strength test The plaster samples as Figure 3 are prepared as described above. The samples are cut into size of 15 cm wide and 30 cm long by using a powered saw with a diamond blade for testing flexural strength according to BS EN 196 at support span of 100 mm and loading rate at lOON/second. The flexural strength is measured from the maximum load at which the macrocrack develops. The flexural strength shown in Figure 3 is the average value obtained from testing three to five test samples for each plaster samples.

Figure 3 shows that the average flexural strength of the plaster supported by PP mesh is higher than the plaster without mesh, the plaster with fiber glass mesh and the plaster with steel mesh.