| JPH10273555A | 1998-10-13 |
This invention relates to a reinforcing fibre, a process for making a reinforcing fibre, a process for making a plurality of reinforcing fibres, a reinforcing fibre for a curable resin made by the process of the invention, a cured composite, a curable composite, a process for making a cured composite, a method of applying a composite to a surface, and a method of moulding a composite.
When fibre reinforced vinyl functional/free radical initiated resins such as Unsaturated Polyester or Vinyl Ester resins are applied to an open mould, they require mechanical consolidation to remove entrapped air. There are two reasons for removing air. The first is to optimize the mechanical strength of the composite, and the second is to improve the chemical resistance. This is also true for epoxy resin composite laminates.
The present art is to
1. spray chopped glass rovings into the resin fan before deposition, or
2. to apply sheets of fabric reinforcement to the mould and then to wet these out with resin, or
3. to pre impregnate the fabric reinforcement with resin prior to placing it on the mould.
All these procedures require some form of mechanical consolidation of the applied laminate to remove entrapped air.
In the current art it is not desirable that the fibres are intimately bonded to the resin matrix. All that is required is that there is sufficient bonding so that the applied stresses can be transmitted to the fibres.
A large proportion of the fibres are held in position by mechanical friction. They are free to slide relative to the resin matrix when the composite is strained sufficiently. One can hear this slipping with the aid of a microphone. When the composite ruptures there are an abundance of fibres protruding from the ruptured surfaces. The sizing on glass rovings interferes with glass to matrix bonding.
The reason the current art performs is due largely to the length of the fibres. Typically fibre length ranges from 12 mm to tens of meters in the case of filament winding and pultrusion and woven rovings. If one hammer mills these reinforcements to less than 4 mm and incorporates them into a UPE or VE laminating resin by conventional processes the resulting composite has poor physical properties.
Typically tensile strength is bellow 65 MPa and it has minimal resistance to crack propagation.
The tensile strength of the resin matrix is greater than the tensile strength of the composite.
This comes about by the fact that the reinforcement is too short to be mechanically locked into the matrix. There is little resistance to crack propagation and such composites are not only weak but are also brittle and have very poor impact resistance.
In the literature there is mentioned the CRITICAL LENGTH of a fibre incorporated in a composite. For fibreglass, the critical length is about 2 mm +-1 mm. The critical length is the minimum length of a bonded fibre that will break in a composite due to applied strain.
Crack propagation in short fibre composites is a problem, because using standard laminating resins stress fields are very concentrated. When rupture occurs in brittle matrix short fibre composites the component suffers brittle failure, the part having poor impact resistance.
In Summary
1. The current surface treatment of fibres is inadequate for short fibre composites.
2. Brittle laminating resins do not provide adequate impact resistance.
3. For optimum chemical/environmental resistance non air inhibited resins are preferred for method 2 composites.
Objects of this invention include providing a reinforcing fibre, a process for making a reinforcing fibre, a process for making a plurality of reinforcing fibres, a reinforcing fibre for a curable resin made by the process of the invention, a cured composite, a curable composite, a process for making a cured composite, a method of applying a composite to a surface, and a method of moulding a composite.
According to one embodiment of this invention there is provided a reinforcing fibre, wherein
said fibre has a surface which is substantially coated with a coupling agent for coupling said fibre with a resin when cured so as to improve impact resistance, tensile strength, and flexural strength of a cured composite comprising said resin when cured, said coupling agent being selected from the group consisting of a polymerizable coupling agent and a polymerized coupling agent and said cured composite further comprising a plurality of said fibres coated with the polymerized coupling agent incorporated in said cured resin.
In one particular form there is provided a reinforcing fibre, wherein
said fibre has a surface which is substantially coated with a polymerized coupling agent for coupling said fibre with a resin when cured so as to improve impact resistance, tensile strength and flexural strength of a cured composite comprising said resin when cured and said polymerized coupling agent incorporated in said cured resin.
According to another embodiment of this invention there is provided a process for making a reinforcing fibre, said process comprising:
substantially coating the surface of the fibre with a polymerizable coupling agent for coupling said fibre to a resin so as to improve impact resistance, tensile strength, and flexural strength of a cured composite comprising the resin when cured, and
polymerizing the polymerizable coupling agent.
Depending on the type of fibre and the type of coupling agent it may be necessary to pretreat the surface of the fibre to enable it to be coated with the coupling agent. For example, where the fibres comprise mica platelets such platelets are usually coated with a metal oxide coating (e.g. iron oxide or other metal oxide) prior to coating with the polymerizable hydrophilic coupling agent.
According to another embodiment of this invention there is provided a process for making a plurality of reinforcing fibres, said process comprising:
mixing the plurality of fibres with a liquid comprising a polymerizable coupling agent for coupling said fibre to a resin so as to improve impact resistance, tensile and flexural strength of a cured composite comprising the resin when cured, and polymerizing the polymerizable coupling agent in the liquid so as to substantially coat the surfaces of the plurality of fibres with polymerized coupling agent.
Depending on the type of fibre and the type of coupling agent it may be necessary to pretreat the surface of the fibre to enable it to be coated with the coupling agent. For example, where the fibres comprise mica platelets such platelets are usually coated with a metal oxide coating (e.g. iron oxide or other metal oxide) prior to the mixing step.
The process may further comprise the step of separating the plurality of fibers from the liquid.
The process may further comprise the step of sieving the separated plurality of fibers.
According to a further embodiment of this invention there is provided a reinforcing fibre for a curable resin made by the process of the invention.
According to an additional embodiment of this invention there is provided a cured composite comprising:
a cured resin incorporating a plurality of reinforcing fibres each of said reinforcing fibres having a surface which is substantially coated with a coupling agent for coupling said fibre with the cured resin so as to improve impact resistance, tensile, and flexural strength of said cured composite, said coupling agent comprising a polymerized coupling agent
According to an additional embodiment of this invention there is provided a curable composite comprising:
a curable resin incorporating a plurality of reinforcing fibres each of said reinforcing fibres having a surface which is substantially coated with a coupling agent for coupling said fibre with the resin when cured so as to improve impact resistance flexural strength, and tensile strength of said composite when cured, said coupling agent comprising a polymerized coupling agent.
According to another embodiment of this invention there is provided a process for making a cured composite comprising:
preparing a curable composite by combining a curable resin and a plurality of reinforcing fibres each of said reinforcing fibres having a surface which is substantially coated with a coupling agent for coupling said fibre with the resin when cured so as to improve impact resistance, flexural and tensile strength of a cured composite comprising the cured resin, said coupling agent comprising a polymerized coupling agent, and curing said curable composite.
According to another embodiment of this invention there is provided a method of applying a composite to a surface said method comprising:
preparing a curable composite by combining a curable resin and a plurality of reinforcing fibres each of said reinforcing fibres having a surface which is substantially coated with a coupling agent for coupling said fibre with the cured resin so as to improve impact resistance, flexural strength and tensile strength of a cured composite comprising the cured resin, said coupling agent comprising a polymerized coupling agent;
applying the curable composite to the surface; and
curing said curable composite.
The step of applying can be by painting, pumping, brushing, wiping, streaking, pouring, rolling, spreading or other suitable applying methods used in fibreglass fabrication. By choosing fibres of mean length less than about 4 mm the resin having said plurality of reinforcing fibres can be applied to the surface by spraying.
A composite which is the subject of this invention can utilize fibres the maximum mean length of which is about 3-4 mm more typically about 3 mm (the composite which is the subject of this invention can be pumpable and/or sprayed using current fibreglass deposition equipment a requirement that restricts mean fibre length to a maximum 4 mm). A critical fibre length of the same order of magnitude was unacceptable for these particular applications. Thus for these applications it was of paramount importance to reduce the critical fibre length to under 1 mm. This is achieved by improving coupling and reducing interfacial stresses by plasticizing the interface by thoroughly coating the fibre with coupling agents such as silane coupling agents or suitable organo metal ligands, such as transition metal acrylates.
According to another embodiment of this invention there is provided a method of moulding a composite said method comprising:
preparing a curable composite by combining a curable resin and a plurality of reinforcing fibres each of said reinforcing fibres having a surface which is substantially coated with a coupling agent comprising a polymerized coupling agent for coupling said fibres with the cured resin so as to improve impact resistance, tensile strength, and flexural strength of the composite when cured;
locating the curable composite in a mould; and
curing said curable composite in the mould.
The step of locating the curable composite in the mould may comprise pumping it, pouring it or otherwise placing it, in the mould. Where the moulding process involves injection moulding the step of locating the curable composite in the mould comprises injecting the curable composite into the mould.
This invention teaches the use of resins including flexible resins and resins with moderately high elongation at break to overcome the poor impact resistance.
Throughout this specification it is to be understood that a unique aspect regarding coupling agents used to coat the fibres in this patent is that coupling agents are polymerized before and/or during the coupling process. It is of paramount importance to have a preponderance of polymers adhering to the surface as the presence of these polymers effectively stress relieve the interface during curing of the composites which can be short fibre composites. Two or more different coupling agents may be used.
Usually the fibres do not have sizing agents of any sort on the surface of the fibres. In order to obtain such fibres from standard fiberglass fibres which come coated with sizing agents it is necessary to remove such sizing agents from the fibres before coating the fibres with a coupling agent. In addition, the density of coupling agents on the surface of the fibres is extremely high—usually the polymerization of the coupling agent is performed to a substantial extent. For example, the step of polymerizing the coupling agent comprises polymerizing the coupling agent for a period in the range 5-60 hours, typically a period in the range 10-30 hours, 12-30 hours, 15-30 hours, 15-30 hours or 20-30 hours. Typically the step of polymerizing the coupling agent comprises polymerizing the coupling agent for a period such as 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 hours.
Thixatropes such as fumed silica/inorganic thixatropes interfere with the resin bonding to fibres, by adding to interfacial stresses. Organic thixatropes especially the amide type such as Thixatrol Plus and glyceryl stearate products help plasticize then interface and therefore improve bonding. These are preferred products when optimum strength of the composite is required.
Usually the entire external surface of a fiber is substantially coated with the coupling agent.
Examples of Materials
The following list is by way of exemplification only and is by no means an exhaustive list.
Monomers and Oligomers Mono and di and trifunctional acrylates and methacrylates, styrene, and polyallyl ethers.
GP UPE Laminating Resins
Eterset 2504 PT orthophthalic ethylene glycol fumaric acid resin, Eterset 2597 PT orthophthalic ethylene glycol fumaric acid resin, and NAN YAR LA111 orthophthalic ethylene glycol fumaric acid resin.
Chemical Resistant UPE Resins
Eterset 2733 Ortho NPG fumaric acid chemical resistant resin,
Eterset 2731 Iso NPG fumaric acid chemical resistant resin, NAN YAR GL316 Iso NPG fumaric acid chemical resistant resin, Swancor 901 45, Swancor 911 45, Hetron 922. and Derakane 411 45.
Flexible Resins
SYN6311 Cray Valley, F61404-30 NUPLEX, Swancor 980 Toughened VE
Swancor 981 Flexible VE, and Aromatic Corp flexible VE.
Cure In Air UPE Resins
ROSKYDAL 500A, and VUP4732 SOLUTIA.
Toughening Additives
SARTOMER CN962 URETHANE ACRYLATES, SARTOMER CN964 URETHANE ACRYLATES, SARTOMER CN965 URETHANE ACRYLATES and HYCAR REACTIVE LIQUID POLYMER 1300X33 VTBNX.
Plasticizers
PALAMOL ADIPATES, and DI BUTYL PHTHALATE.
Cure In Air Additives
SANTOLINK XI 100, PMMA, and PS
Thixatropes
Rheox THIXIN E, Rheox THIXATROL+, FUMED SILICAS Cabot, Wacker, and TREATED CLAYS.
Promoters
COBALT OCTOATE, COBALT OXALATE, POTASSIUM OCTOATE, ZIRCONIUM OCTOATE, VANADIUM NAPHTHENATE, COPPER NAPHTHENATE, ZINC OCTOATE, and DMA.
Inhibitors
ACETYL ACETONE, HYDROQUINONE, and TBHQ.
Air Release Agents
BYK A515 AND 510. SWANCOR 1317, BEVALOID 6420 and EFKA20.
Leveling Agent
EFKA 777
Catalysts
MEKP, CHP, and benzoyl peroxide
Fibres
Milled glass fibres made from (Vetrotex, Camalyef, SUR100,HPR800), Kevlar/aramid fibres, Wollastonite fibres, Nylon fibres, and calcined surface treated micas
Fillers
Zenospheres, PVC Powder, and treated organo clays.
Coupling Agents
Silanes/acrylic functional, silanes/vinyl functional, silanes/styrene functional, silanes and zinc diacrylate.
The advantages of this Technology over the current art are:
The invention provides amongst other things a sprayable/pumpable reinforced resin composite that does not require mechanical consolidation. This composite can be used for fabricating FRP objects such as swimming pools, boats, baths, spas, liquid storage tanks, fibreglass panels, cowlings, etc. It can be used with foaming resins to add mechanical strength, and it is ideally suited to resin injection molding.
Modification of the Surface of Fibres and Methods of Forming Composites
The standard surface treatment of fibres is not satisfactory. The silane coupling agents used are not applied thoroughly in the case of glass rovings. Commercially available milled glass rovings are manufactured from continuous rovings which have been coated with a sizing material such as EVA or PVA emulsion. This sizing must be removed from the milled glass prior to coating the fibre with coupling agent. And in the case of mineral fibres the coupling agents on commercially available fibres are too low in molecular weight and density on surface of the fibres.
In order to optimize the performance of the composites it is necessary to optimize the application of silanes to modify the chemistry and therefore the forces at the interface of the fibres with the resin. This may be achieved by partially polymerizing the silane coupling agents prior to bonding them to the fibres.
In one form this may be achieved by allowing the silanes in aqueous solution to polymerize at suitable pH (pH 7 or greater) for a suitable time, prior to acidification and coupling.
It is theorized that the reaction rate of the higher molecular weight silanes bonding to the fibres is considerably slower due to, among other influences, steric hindrance. For this reason fibres are left soaking in the aqueous silane for up to a day or longer to optimize the population of higher molecular weight silanes on the surface.
The aim is to improve bonding, and stress relieve the interface during polymerization of the resin matrix.
Reducing interfacial stress is critical to optimize the performance of the short fibre composite.
Alternatively (where the fibres are not coated with acid soluble materials such as iron oxides), the coupling agent may be mixed with the fibres at acidified pH (e.g. about pH 3) and the pH gradually raised over 10-36 hours to pH 7+/−1 pH unit. Where the fibres are not coated with acid soluble materials such as iron oxides, the coupling agent may be mixed with the fibres at neutral pH (e.g. about pH 7) and the pH maintained or gradually raised over 10-36 hours to pH 9+/−1 pH unit.
Throughout this specification the terms fibre and fibres are to be taken to include platelet and platelets respectively. Surface treated mineral fibres such as Wollastonite, and ceramic fibres such as glass fibres are the most suitable fibres for this invention however surface treated synthetic fibres can be used (e.g. surface treated aramid fibres, mylar fibres, nylon fibres, linear polyethylenes, linear polypropylenes, polyesters and carbon fibres). Maximum fibre length 6 mm, mean fibre length 4 mm or less. Alternatively, surface treated platelets such mica platelets (if precoated with a suitable metal oxide such as iron (III) oxide, iron (II) oxide, titanium dioxide, tungsten oxide, hafnium dioxide, nickel oxide, cobalt oxide, manganese dioxide, chromium trioxide, vanadium pentoxide, zinc oxide, molybdenum trioxide, tin dioxide, indium trioxide, niobium pentoxide, tantalum pentoxide, zirconium dioxide etc).
Resins with an elongation to break of greater than 6% are preferred. The most suitable resins are those which are naturally tough and with an elongation at break greater than 10%.
For lining of concrete vessels, and steel vessels to improve their chemical resistance, resins with low elongation at break are suitable.
However for load bearing structures the resins with higher elongation at break give best performance.
As mentioned before the more “elastic” the resin is the stronger and more serviceable the composite.
As the % of reinforcement increases so do the mechanical properties of the composite up to a point, and then the tensile strength of the laminate begins to fall.
Until better bonding is achieved between the resin and the reinforcement, fibre contents of around 30% to 50% by weight appear optimum.
The most suitable resins are epoxy vinyl ester resins, tough vinyl functional urethane resins, tough vinyl functional acrylic resins, and flexible polyester resins—the non plasticized type.
| % by Weight | |
| Formulation Space (a) for Method 1 | |
| Resin | 20% to 89.999% |
| Reactive monomers and or oligomers | 0% to 30% |
| Fibres coated with or oxide coated platelets | 10% to 60% |
| coated with Coupling Agents Silanes, | |
| and or Organo-Metal Compounds | |
| Promotors/Catalysts | 0.001% to 10% active |
| ingredient | |
| Thixatropic Agents | 0% to 30% |
| Pigments | 0% to 35% |
| UV Stabilizers | 0% to 20% |
| Formulation Space (b) for Method 1 | |
| Reactive Diluents (Vinyl functional monomers | 20% to 89.999% |
| and oligomers) | |
| Non Reactive Diluents | 0% to 30% |
| Fibres coated with or oxide coated platelets | 10% to 60% |
| coated with Coupling Agents Silanes, | |
| and or Organo-Metal Compounds | |
| Promotors/Catalysts | 0.001% to 10% active |
| ingredient | |
| Thixatropic Agents | 0% to 30% |
| Pigments | 0% to 35% |
| UV Stabilizers | 0% to 20% |
| Formulation Space (c) for Method 1 | |
| Resin + Reactive Diluents (Vinyl functional | 20% to 89.999% |
| monomers + oligomers) | |
| Non Reactive Diluents | 0% to 30% |
| Fibres coated with or oxide coated platelets | 10% to 60% |
| coated with Coupling Agents Silanes, | |
| and or Organo-Metal Compounds | |
| Promotors/Catalysts | 0.001% to 10% active |
| ingredient | |
| Thixatropic Agents | 0% to 30% |
| Pigments | 0% to 35% |
| UV Stabilizers | 0% to 20% |
These formulations can be sprayed using conventional fibreglass depositors. For Example Glasscraft, Venus Gussemer, Binks Sames, etc.
One typical process for coating glass and/or wollastinite fibres comprises:
Coupling solution: to water add 0.1-1 wt % silane coupling agent, adjust pH to pH 3 typically using acetic acid or equivalent, add 50 parts by weight of uncoated glass fibres and/or wollastinite fibres, agitate slowly just to suspend fibres, slowly raising the pH over 24 hours to pH 7, then filter fibres, then dry to >0.1 wt % at about 110° C. Sieve dried, coated fibres through 800 μm+/−200 μm screen. Avoid agglomeration of fibres prior to adding to resin. Incorporate fibres into resin gradually to optimise wetting of individual fibres and so as to avoid clumping in the resin. Add promoter and initiator and optionally air release agent(s) and thixotrope(s) and allow a composite to form. The resultant composite, when cured, has improved impact resistance, tensile and flexural strenght as compared to fibre composites where the fibres have not been treated as described above.
Another typical process for coating glass and/or wollastinite fibres comprises:
Coupling solution: to water add 0.1-1 wt % silane coupling agent, adjust (if necessary) pH to pH 7+/−1 pH unit to allow partial polymerisation of coupling agent and then adjust to pH 3 typically using acetic acid or equivalent, add 50 parts by weight of uncoated glass fibres and/or wollastinite fibres, agitate slowly just to suspend fibres, slowly raisng pH over 24 hours to pH 7, then filter fibres, then dry to >0.1 wt % at about 110° C. Sieve dried, coated fibres through 800 μm+/−200 μm screen. Avoid agglomeration of fibres prior to adding to resin. Incorporate fibres into resin gradually to optimise wetting of individual fibres and so as to avoid clumping in the resin. Add promoter and initiator and optionally air release agent(s) and thixotrope(s) and allow a composite to form. The resultant composite has improved impact resistance, flexural strength, and tensile strength as compared to fibre composites where the fibres have not been treated as described above.
A further process for coating glass and/or wollastonite fibres comprises:
Coupling solution: to water add 0.1-1 wt % silane coupling agent, adjust (if necessary) pH to pH 7+/−1 pH unit to start polymerisation of coupling agent, add 50 parts by weight of uncoated glass fibres and/or wollastonite fibres, agitate slowly just to suspend fibres stir slowly for about 24 hours, then filter fibres, and dry to >0.1 wt % at about 110° C. Sieve dried, coated fibres through 800 μm+/−200 μm screen. Avoid agglomeration of fibres prior to adding to resin. Incorporate fibres into resin gradually to optimise wetting of individual fibres and so as to avoid clumping in the resin. Add promoter and initiator and optionally air release agent(s) and thixotrope(s) and allow a composite to form. The resultant composite has improved impact resistance, flexural and tensile strength as compared to fibre composites where the fibres have not been treated as described above.
One typical process for coating mica platelets (5 microns to 4000 microns) comprises:
Precipitate iron hydroxide from an iron (III) containing solution (eg 0.01-1M ferric chloride) by adjusting the pH to about > pH 9 onto mica platelets. Filter platelets an dry at 400° C. Coupling solution: to water add 0.1-1 wt % silane coupling agent, adjust pH to pH 7, add 50 parts by weight of Fe2O3 coated mica platelets, agitate slowly just to suspend platelets. Slowly agitate platelets in solution for 24 hrs, then filter platelets, then dry to >0.1 wt % at about 110° C. Sieve dried, coated platelets through suitable aperture screen to break up agglomerates. Avoid agglomeration of platelets prior to adding to resin. Incorporate platelets into resin gradually to optimize wetting of individual platelets and so as to avoid clumping in the resin. Add promoter and initiator and optionally air release agent(s) and thixotrope(s) and allow a composite to form. The resultant composite has improved impact resistance, tensile strength, and flexural strength as compared to platelet composites where the platelets have not been treated as described above.
Another typical process for coating mica platelets comprises:
Precipitate iron hydroxide from an iron (III) containing solution (eg 0.01-1M ferric chloride) by adjusting the pH to about > pH 9 onto mica platelets. Filter platelets and dry at 400-600° C. Allow to cool then mill to mean particle size in the range 3 mm-1 μm and then sieve. Coupling solution: to water add 0.1-1 wt % silane coupling agent, adjust (if necessary) pH to pH 7+/−1 pH unit to allow partial polymerisation of coupling agent add 50 parts by weight of calcined mica platelets, agitate slowly just to suspend platelets, slowly for 24 hours, then filter platelets, then dry to >0.1 wt % moisture at about 110° C. Sieve dried, coated platelets through suitable screen to break up agglomerates. Avoid agglomeration of platelets prior to adding to resin. Incorporate platelets into resin gradually to optimise wetting of individual platelets and so as to avoid clumping in the resin. Add promoter and initiator and optionally air release agent(s) and thixotrope(s) and allow a composite to form. The resultant composite has improved impact resistance, tensile strength, and flexural strength as compared to composites where the platelets have not been treated as described above.
A further process for coating process for coating mica platelets comprises:
Precipitate iron hydroxide from an (III) containing solution (eg 0.01-1M ferric chloride) by adjusting the pH to about > pH 9 onto mica platelets. Filter platelets and dry at 400° C.-600° C. Coupling solution: to water add 0.1-1 wt % silane coupling agent, adjust pH to pH 7 to start polymerisation of coupling agent, add 50 parts by weight of calcined mica platelets, agitate slowly just to suspend platelets stir slowly for about 48 hours, then filter platelets, and dry to >0.1 wt % at about 110° C. Sieve dried, coated platelets through 800 μm+/−200 μm screen. Avoid agglomeration of platelets prior to adding to resin. Incorporate platelets into resin gradually to optimise wetting of individual platelets and so as to avoid clumping in the resin. Add promoter and initiator and optionally air release agent(s) and thixotrope(s) and allow a composite to form. The resultant composite has improved impact resistance, tensile strength, and flexural strength as compared to composites where the platelets have not been treated as described above.
Fibre Length Specification
Fibre length maximum 6 mm, typically less than 2 mm. Fibre length distribution in the range 6 mm to 1 μm.
| Fibre Length Disitribution Space | Wt % | |
| >=4 mm | 0% to 20% | |
| <4 mm, >=2 mm | 0% to 35% | |
| <2 mm, >=1 mm | 0% to 50% | |
| <1 mm | 0% to 100% | |
A typical fibre length space for swimming pools or liquid storage tanks
| >=4 mm | Less than 2% by Wt fibres |
| <4 mm but >=2 mm | Between 5% and 50% by Wt fibres |
| <2 mm | Between 5% and 50% by Wt fibres |
| Typical Tensile Strength of Method | 60 to 100 MPa |
| 1 laminates | |
| Typical Flexural Strength | 80 to 150 Mpa |
Method 2 Applying a laminate that contains chopped rovings but does not require mechanical consolidation.
Method 2 relies on a resin being non air inhibited. This can be achieved in two ways. By incorporating a suitable thermoplastic polymer at approximately 0.3% to 1% by weight of total vinyl functional constituents. Or by adding suitable allyl crosslinkers that stop air inhibition. These are added at concentrations between 4% and 35% of total vinyl functional constituents.
Method 2 allows for fibres to be sprayed onto the mould with the non air inhibited resin as chopped rovings in the normal way. However it is best if the resin contains approximately 15% by volume short fibre liquid composite described in method 1, this is because the short fibre composite has good mechanical properties.
Much less chopped rovings are required to achieve adequate strength when combined with the short fibre composite.
This allows for “resin to glass” ratios greater than 3 to 1. The excess resin available is used to hose down “furries” that is chopped rovings protruding from the wet laminate.
This laminate does not require mechanical consolidation and is potentially stronger than the Method 1 Laminate.
Deposition is as follows
1. Spray a bed with the liquid composite about 0.1 mm to 0.3 mm deep.
2. Then spray liquid composite and chopped rovings together thinly leaving about 5% to 10% of the first layer visible
3. Spray the “dry” rovings with liquid composite until completely wetted.
4. Spray rovings and liquid composite as in 2.0 then spray “dry” rovings as in 3.
5. Repeat step 4. until the required thickness is achieved.
6. Allow to cure and demold if necessary.
Please note that this procedure does not require laminating.
If the laminate needs to be chemically resistant then step one above can he repeated until 1.5 two 2.5 mm of liquid composite is deposited prior to building up the laminate.
In Method 2. the resin in the liquid composite can be a standard laminating resin as the average composite fibre length is much greater than 4 mm.
| Typical Tensile Strength of Method 2 laminates | >100 MPa | |
| Typical Flexural Strength | >150 MPa | |
Composite/Laminate Thickness
Any thickness of composite can be achieved simply by applying multiple passes. It is best to use a build between 0.5 mm and 1.0 mm per pass, this minimizes air entrapment.
Laboratory test laminates have been sprayed using a Binks Sames pressure pot Binks hand-piece internal catalyst mix. Robinson catalyst system. Operating pressure 80 psi—air nebulized.
Mold waxed melamine board.
Small spa mould.
Test sample mold
A small two person spa was made using a Robinson depositor and the resin formulated below.
The coping was reinforced with the Method 2 laminate. The product was successfully demolded. It was able to hold a full volume of water unsupported.
Sprayed and test molded panels have been tested to required ASTM test methods for Tensile Strenght, Tensile Modulus, Flexural Strength, and Flexural Modulus.
Typical results for Method 1 laminates are
Flexural Strength 80 MPa to 160 MPa
Flexural Modulus 5 Gpa to 6 Gpa
Tensile Strength 60 Mpa to 110 Mpa
Tensile Modulus 5 GPa to 6 GPa.
| Typical composite | ||
| Swancor 981 flexible Vinyl Ester resin | 100 parts | |
| Styrene | 10 parts | |
| Thixatrol + amide thixatrope | 3 parts | |
| Cobalt octoate 6% solution | 0.5 parts | |
| Di methyl analine | 0.15 parts | |
| Treated wollastonite fibres | 38 parts | |
| Air release agent Swancor 1317 | 0.7 parts | |
| Summary of test results | |
| Type 2 Composite | |
| The weight % for test samples are as follows | |
| 10% silane/acrylic surface treated wallstonite or milled glass fibres for composites | |
| made using a combination of chopped fibreglass rovings and liquid composite. Resin | |
| composite to chopped rovings ratio (equivalent to resin to glass ratio) 3.5:1 Resins used: | |
| Impact tests | |
| 1. Swancor 980 toughened VE resin | 25 kg/cm2 Charpy ASTM D256 |
| 2. Swancor 981 flexible VE resin | 22 kg/cm2 Charpy ASTM D256 |
| 3. F61404/30 Nuplex Flexible UPE resin | 19 kg/cm2 Charpy ASTM D256 |
| 4. 2504 Eterset GP laminating resin | 8 kg/cm2 Charpy ASTM D256 |
| Tensile test ASTM D638M | |
| 1. Swancor 980 toughened VE resin | 158 MPa |
| 2. 2. Swancor 981 flexible VE resin | 134 MPa |
| 3. F6140/30 Nuplex Flexible UPE resin | 65 MPa |
| 4. 2504 Eterset GP laminating resin | 109 MPa |
| Test Results for Method 1 Composites | |
| Liquid Composite 35% W.V. Silane treated fibres | |
| Impact Tests | |
| 1. Swancor 980 toughened VE resin | 22 kg/cm2 Charpy ASTM D256 |
| 2. Swancor 981 flexible VE resin | 21 kg/cm2 Charpy ASTM D256 |
| 3. F61404/30 Nuplex Flexible UPE resin | ??kgcm/cm2 Charpy ASTM D256 |
| 4. 2504 Eterset GP laminating resin | 5 gcm/cm2 Charpy ASTM D256 |
| Tensile Strength Tests ASTM D638M | |
| 25% W.V. Silane acrylic coated fibres | |
| LA111 NanYar GP laminating resin | 60 MPa |
| Swancor 981 | 88 MPa |
| F61404 Nuplex flexible UPE | 45 MPa (Necking resin too elastic) |
| Swancor 980 | 93 MPa |
| Flexural Strength ASTM D790M | |
| 40% Silane styrene functional coated fibres | |
| Swancor 980 | 152 MPa |
| G16404/30 | ??MPa (Indeterminate too flexible) |
Dated Nov. 7, 2001 | |