| 1. | 1 A composite coated wooden post comprising an outer layer of fibre reinforced thermosetting polyester resin wrapped around a wooden inner core to form laminations that completely cover the wooden core, enhancing the physical properties of the post. |
| 2. | A post according to claim 1 wherein the wooden core can be made from any timber, including composite timber, laminated timber, and compressed fibres. |
| 3. | A post according to claim 1 wherein the resin matrix consists of a base polymer resin and additives where the additives are but not limited to monomers, initiators, promoters, inhibitors, thixotropes, UV inhibitors, fillers and pigments. |
| 4. | A post according to claim 3 wherein the fibres within the matrix consist of glass or organic fibres predominantly in the form of a woven cloth but not limited to yarn, chopped strand, milled, mat, woven fabric, woven roving, or surfacing mat. |
| 5. | A post according to claims 1 and 3 wherein the outer coating is in the form of a gel coat or top coat which consists of a base resin and additives which include but are not limited to thixotropic agents, fillers, pigments, UV inhibitors, initiators, promoters, monomers, and inhibitors. |
| 6. | A post according to claim 1 wherein the final product forms a solid structural member over the full length of the product. |
| 7. | A post according to claim 5 wherein the finished product will have a coloured outer coating. |
BACKGROUND OF THE INVENTION Timber is widely used throughout a large cross section of industry. In agriculture, timber products are used for vine trellising, fence posts and many other applications. In the building and construction area it is used extensively from outdoor leisure to scaffolding.
Timber in general has the disadvantages of being attacked by various insects and is susceptible to weathering and rotting. Over the years there has been extensive use of chemical treatments to slow down the weathering and rotting of timber and the infestation of insects. In general boost of these chemicals over the last several decades have been banned or substantially reduced in their uses due to toxicity and carcinogenic properties.
For example, in the wine industry, there is currently extensive use of CCA treated pine trellis posts. CCA is now being banned in many countries throughout the world, due to its heavy metal contamination of the environment.
In the building industry, treated pine is used to mike outdoor leisure structures such as gazebos, pergolas, children's playgrounds, just to name a few. The controversy surrounding the chemical treatment of timbers and their interaction with human beings is still cause for concern. There is no real alternative other than expensive and limited hardwood timbers for these applications.
Throughout the world there are extensive plantations of softwood timbers. These plantations provide fast growing timbers that can be used in a variety of applications, including everything from pine ceiling beams to medium density fibreboard. The advantage of softwood plantations is the rate at which the trees grow, making them very economical in comparison to hardwood timber.
The disadvantages, apart from rotting, weathering and insect infestation, are their limited structural ability, their soft compressive nature, and their inability to take wear and tear. The treated pine trellis posts used throughout the wine industry are exposed to mechanical harvesting and suffer breakages as a result.
An example of a softwood timber referred to above is Paulownia.
This particular timber can be harvested before the tree reaches 6 years of age. This timber is extremely lightweight, typically 250-280kg per cubic metre, and is used for making crates and simple furniture but is very limited in its structural ability.
Fibre reinforced thermosetting polyester composites are widely used in many applications, e. g. marine, automotive, transportation, construction, food production, electrical, consumer and industrial goods.
Composite materials are known to have advantages of high strength, light weight, design flexibility, dimensional stability and corrosion resistance over traditional construction materials such as metal, ceramics and wood.
Thermosetting polyester resins are selected on the basis of performance, adaptability to the moulding process and cost. The most common resins are: unsaturated polyester, vinyl ester, epoxy, polyurethane and acrylic.
The polymer backbone refers to the specific type of molecule that is the basic building block of the resin system. The chemical designation of the polymer backbone is typically used to describe resin formulations. Categories of polyester resin are: Orthophthalic Isophthalic Dicyclopentadiene Chlorendics Bisphenol-A
In the formation of the matrix, the unsaturated polyester resin is blended typically with one or more monomers capable of cross- linking with the backbone polymer. Styrene and methyl methacrylate (MMA) are the most common monomers used with polyester and vinyl ester resin systems. Other less common monomers include: vinyl toluene, alpha-methyl styrene, paramethyl styrene and diallylphthalate.
The matrix requires the use of initiators (catalyst) such as ketone peroxides, acetylacetone peroxides, benzoyl peroxides, and cumine hydroperoxide. Promoters are metal salts or amine compounds; the most common promoter used with MEKP initiator is cobalt napthenate (CoNap) or cobalt octoate. In the case of BPO initiator, amine promoters such as dimethylaniline (DMA), diethylaniline (DEA) and dimethylacetoaceta-mide (DMAA) are used. Amine promoters can also be used in conjunction with cobalt promoters in an MEKP system to produce a rapid cure following getation.
There are a number of additives that are used to modify and enhance resin properties. These additives include: Thixotropes Fillers Pigments Fire Retardants Suppressants UV Inhibitors Conductive Additives Thixotropes are important in the open moulding process to limit the resih draining from the laminate before it gels ; the most common thixoptrope in polyester resin is fumed silica.
A Gel coat is a specialized polyester resin that will provide an outer surface on the composite matrix and provide weatherability for the coated timber post. Gel coat consists of a base resin and additives.
The base resin may be a variety of polyester or vinyl ester resins which are for a specific end-use. Base resin additives include thixotropic agents, fillers and pigments.
Predominantly E type (lime aluminum borosilicate) glass fibres will be used in the matrix in the form of a woven fabric or woven roving.
Alternate fibres such as organic fibres can also be used in the same forms within the matrix.
In an attempt to overcome the disadvantages associated with chemical treatments of timber and the harvesting of hardwood timber from naturally occurring forests, composite manufactured timber products can be used as an alternative.
In a process of combining the advantages of fibre reinforced thermosetting composites and timber, an emerging product can be used to satisfy a large market of existing timber products.
SUMMARY OF INVENTION A composite coated wooden post comprising an outer layer of fibre reinforced thermosetting polyester resin wrapped around a wooden inner core to form laminations that completely cover the wooden core, enhancing the physical properties of the post.
The object of the invention is to use any wooden or fibre material that can form the shape of a timber product like a post or beam and permit that product to form the core of this invention.
The wooden core can be wrapped in composite materials via hahd laying or by machine.
The invention will increase the structural properties of the core timber.
The wooden core is completely covered in a fibre matrix, enhancing its properties of rot and insect penetration, ultra violet degradation and weathering.
In the drawing: Fig 1 shows the layers of fibre reinforced polyester plastic encapsulating the wooden core, illustrating the principles of the invention.
Description of the invention Figure 1 illustrates the various layers that form the composite coated wooden post in that the post consists of outer layers of fibre reinforced thermosetting polyester resin wrapped around a wooden inner core to form laminations that completely cover the wooden core.
The wooden core 2 of this invention will form a mandrill or blank in the manufacturing process. This core 2 can be comprised of any timber product which includes sawn timber, laminated timber and composites of timber including compressed fibres. The fibres can be palm fibres or from products formed from cellulose fibres. The core 2 will determine the length and overall dimensions of the final product.
This core 2 is initially pre-coated with an unsaturated thermosetting polyester resin to penetrate the timber blank to form a tack surface in order to apply the woven fibres.
The Composites 4 are a combination of fibre reinforcement in a polymer matrix 3. The matrix 3 is a resin that transfers the load to the reinforcement fibre and protects the fibre from environmental effects.
The unsaturated polyester resins used in the invention are known in the prior art. In a preferred form of the invention the base resins will be selected from a group containing Orthophthalics Isophthalic, Dicyclopentádiene, Chlorendics or Bisphenol-A.
The monomers will be selected from a group containing styrene, methyl methacrylate, vinyl toluene, alpha-methyl styrene, paramethyl styrene and diallylphthalate.
The initiators from a group containing: ketone peroxides, acetylacetone peroxides, benzoyl peroxides, and cumine hydroperoxide.
Promoters from: cobalt napthenate (CoNap), cobalt octoate, dimethylaniline (DMA), diethylaniline (DEA) and dimethylacetoaceta-mide (DMAA).
The additives that will be used to modify and enhance resin properties will be selected from: thixotropes, fillers, pigments, fire retardants, suppressants and UV inhibitors.
Predominantly E type (lime aluminum borosilicate) glass fibres will be used in the matrix 3 in the form of a woven fabric or woven roving.
Alternate fibres such as organic fibres can also be used in the same forms within the matrix 3.
The core 2 is then laminated in a continual process of wetting out the woven fibres with a desired mixture of unsaturated polyester resin until the desired amounts of laminations are formed. The number of laminations and the direction of the fibres can be modified to form a specific or desired strength in any one direction. The combination of this process results in the formation composite matrix 4.
The outer coating 6 of the invention is a gel coat or top coat which consists of a base resin and additives to form the outer matrix 5. The base resin may be a variety of polyester or vinyl ester resins which are specified for a specific end-use. Base resin additives include thixotropic agents, fillers, UV inhibitors and pigments. The exterior gel/top coat 6 will form a tough UV stabilized coloured coating, completely sealing the inner core 2.
Soft wood plantation timber can be upgraded to a structural rating using the principles of this invention. For example Paulownia has no structural rating. It is very soft and is easily dented and broken. A test of the invention was conducted using Paulownia timber in the form of a wine grape trellis post. The test was conducted using the standards expressed in AS/NZS4063: 1992.5 samples were tested and the test results were compared to standard treated pine poles that are used for vine trellis posts, the samples achieved structural strength rating higher than 35Mpa or F 11. The comparison was rhatched to a pine post having an average diameter of 75 mmi with the Paulownia posts wrapped in composite having a square section of 50mm. The composite post achieved an equivalent strength of the pine post even given its smaller cross-section. The samples tested showed a significant advantage in flexibility compared to pine posts. The samples showed a tip deflection 6 times greater at failure than a standard pine post with an equivalent force being applied.
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