GB2539484A

GB2539484A - Method of joining a bonded particulate surface

Info

Publication number: GB2539484A
Application number: GB1510736.0A
Authority: GB
Inventors: Cullen Terry
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-06-18
Filing date: 2015-06-18
Publication date: 2016-12-21
Also published as: GB201510736D0

Abstract

The method includes: (i) preparing a first mixture by mixing a particulate material with a polymeric bonding agent comprising a precursor component and a hardener component; (ii) applying the first mixture to a substrate to form a first uncured surface 4; (iii) identifying an edge 6 of the first uncured surface; (iv) preparing a second mixture by mixing the particulate material with the precursor material of the polymeric binder and either no hardener or insufficient hardener to cure the precursor component of the polymeric bonding agent within a pre-determined time; (v) forming a border region 8 of the second mixture along the edge of the first uncured surface such that a first portion of the second particulate mixture is intermixed with a portion of the first mixture and a second, opposed portion 10 of the second mixture is exposed; (vi) allowing or causing the precursor component of the first mixture to cure or partially cure to provide a first bonded particulate surface; (vii) preparing a third particulate mixture by mixing the particulate material with the polymeric bonding agent comprising the precursor component and the hardener component; and (viii) joining a second bonded particulate surface 12 to the first bonded particulate surface by intermixing a portion of the third particulate mixture with the exposed portion of the second particulate mixture such that the hardener component of the third particulate mixture is able to cure the precursor component of both the second and third particulate mixtures.

Description

Method of joining a bonded particulate surface The present invention relates to a method of joining a second bonded particulate surface to a first bonded particulate surface. In particular the method allows the surfaces to be joined without a visible join or seem between them.

Bonded particulate surfaces provide an aesthetically pleasing and hard-wearing surface as an alternative to loose gravel, tarmac, concrete or paved surfaces. The bonded particulate surface typically comprises a particulate mixture which is coated with a bonding agent that is allowed or caused to cure.

To prepare a bonded particulate surface, the particulate mixture is mixed with a polymeric bonding agent and the coated particulate mixture is spread over an area of a substrate to the required depth. The polymeric bonding agent is then allowed or caused to cure, which forms the final bonded particulate surface.

For substrate areas which are relatively small, it is possible to cover the substrate in a day or less and there is no need to include any joints in the surface. Thus, the surface has the appearance of a single continuous surface. The appearance of a single continuous surface is aesthetically desirable.

However, for larger areas or in cases where the required quantities of materials has been incorrectly calculated, joints are required, as it is not possible to cover the entire surface of the substrate in a single application step and the polymeric bonding agent will have cured or hardened before a second application step can be started. The joints in these cases are visible and aesthetically undesirable.

The present invention sets out to provide a method in which a second bonded particulate surface can be seamlessly joined to a first particulate surface. In other words to join two separately formed surfaces in such a way that the joint is either not visible or has a reduced visual impact compared to known methods of joining two bonded particulate surfaces.

According to a first aspect of the invention, there is provided a method of joining a bonded particulate surface, the method including (i) preparing a first particulate mixture by mixing a particulate material with a polymeric bonding agent comprising a precursor component and a hardener component; (ii) applying the first particulate mixture to a substrate to form a first uncured surface; (iii) identifying an edge of the first uncured surface to be joined; (iv) preparing a second particulate mixture by mixing the particulate material with the precursor material of the polymeric bonding agent and either no hardener or insufficient hardener to cure the precursor component of the polymeric bonding agent within a pre-determined time; (v) forming a border region of the second particulate mixture along the edge of the first uncured surface such that a first portion of the second particulate mixture is intermixed with a portion of the first particulate mixture and a second, opposed portion of the second particulate mixture is exposed; (vi) allowing or causing the precursor component of the first particulate mixture to cure or partially cure to provide a first bonded particulate surface; (vii) preparing a third particulate mixture by mixing the particulate material with the polymeric bonding agent comprising the precursor component and the hardener component; and (viii) joining a second bonded particulate surface to the first bonded particulate surface by intermixing a portion of the third particulate mixture with the exposed portion of the second particulate mixture such that the hardener component of the third particulate mixture is able to cure the precursor component of both the second and third particulate mixtures.

Polymers, such as polyurethane, typically comprise a precursor material, such as one or more monomers and/or functionalised polymers, which is then reacted or chemically altered to achieve the final polymeric bonding agent. The conversion of the precursor material into the final form of the polymeric bonding agent is referred to herein as "curing". The curing step includes the addition of what is termed herein a hardener. The hardener may be a catalyst (i.e. a reagent that is not incorporated into the final polymeric product), a reactive component (i.e. a compound or mixture of compounds which are incorporated in to the final polymeric product) or a combination of both a reactive component and a catalyst. The curing step may also include heat and/or UV light.

Reference herein to the precursor component of the second particulate mixture not being cured within a pre-determined time allows the users of the method a period of time within which the second bonded particulate surface can be seamlessly joined to the first bonded particulate surface. The time may allow the work to continue over a two day period where the substrate to be covered has a surface area which is greater than the area that can be covered in a single day. In such embodiments, the period of time may be at least 12 hours. Alternatively, in embodiments in which an insufficient quantity of material has been obtained, the time period allows for further material to be obtained. Again, this time period may be at least 12 hours or it may be at least 18 hours or at least 24 hours. Thus, the second particulate mixture may include insufficient hardener to cure the precursor component of the second particulate mixture within a 12 hour period, optionally within an 18 hour period, further optionally within a 24 hour period.

When the polymeric bonding agent is a polyurethane material, the precursor material typically comprises a polyol component containing on average two or more hydroxyl groups per molecule. The hardener for polyurethanes is typically an isocyanate component which contains two or more isocyanate groups per molecule. A catalyst may also be added to the mixture of the precursor component and the hardener. The catalyst may comprise a tertiary amine or a metallic compound. In an embodiment of the invention, the polymeric bonding agent is a polyurethane material, the precursor component comprises a polyol component and the hardener is an isocyanate component. The hardener component of a polyurethane bonding agent may further include a catalyst.

The precursor component may be a single agent or a mixture of two or more agents.

The particulate material may be selected from an aggregate, marble elements, glass elements, quartz elements, rubber elements and mixtures thereof. In the context of the present invention, aggregate is a particulate material formed from small stones, stone pieces and/or stone chippings.

The particulate material of the invention suitably has an average diameter from 0.1mm to 50mm, where the diameter is defined as the longest dimension of the particle and the average is a number average. Furthermore, the particulate material may be coated or coloured to provide a desired appearance or physical property. Suitably, the particle diameter is from 1 to 40mm, optionally from 1 to 30mm.

The border region of the second particulate mixture may have a width of 1 to 20cm. The minimum width of the border region may be 2, 3 or 4cm and the maximum width of the border region may be 15, 10 or 5cm. If the border region has a width of less than 1cm, the intermixing between the second and the first particulate mixtures may be sufficient that the hardener from the first particulate mixture is able to cure the precursor material of the second particulate mixture to an extent that the third particulate mixture is unable to intermix with the border region formed by the second particulate mixture. Similarly, if the border region has a width of greater than 20cm, the third particulate mixture may not be capable of intermixing with the second particulate mixture of the border region sufficiently that the hardener of the third particulate mixture is capable of properly curing the precursor component of the second particulate material.

In an embodiment of the invention, the border region may include a sacrificial portion, whereby step (v) includes forming a border region of the second particulate mixture including a sacrificial portion of the mixture; and step (viii) includes the step of removing the sacrificial portion prior to intermixing a portion of the third particulate mixture with the exposed (remainder) portion of the second particulate mixture. In this embodiment, the width of the remaining border region (i.e. after the removal of the sacrificial portion) may be 1 to 20cm for the reasons given above. The minimum width of the remaining border region may be 2, 3 or 4cm and the maximum width of the remaining border region may be 15, 10 or 5cm. Accordingly, reference herein to the width of the border region includes the width of the remaining border region after a sacrificial portion has been removed.

Thus, the width of the initial border region may be greater than 20cm in embodiments where the initial border region includes a sacrificial portion that may be removed in step (viii) to provide a remaining border region having a width which is 20cm or less.

Step (iii) may include identifying one or more edges to be joined. For example, Step (iii) may include identifying two, three or four edges to be joined. In such embodiments, Step (v) includes forming a border region along each edge.

The method may include the further step of causing or permitting the precursor component of the second and third particulate mixtures to cure. This further step results in a second bonded particulate surface seamlessly joined to the first bonded particulate surface.

Suitably, the bonded particulate surfaces are liquid permeable. Thus, the particulate surfaces may include voids or interstices between the particulate material. In this way, water and other liquids may be capable of draining through the particulate surfaces to the substrate beneath in order to prevent flooding or the formation of sitting water.

In certain embodiments of the invention, the hardener may be a two component system comprising a reagent component (i.e. which is incorporated into the final cured polymer) and a catalyst (i.e. which is not incorporated into the final cured polymer). In such an embodiment, step (iv) may comprise the omission of one or both of the hardener components or the inclusion of an amount of one or both of the hardener components which is insufficient to cure the precursor component of the polymeric bonding agent within the pre-determined time.

According to a second aspect of the invention, there is provided a method of joining a bonded particulate surface, the method including (i) preparing a first particulate mixture by mixing a particulate material with a polymeric bonding agent comprising a precursor component and a two-part hardener component; (ii) applying the first particulate mixture to a substrate to form a first uncured surface; (iii) identifying an edge of the first uncured surface to be joined; (iv) preparing a second particulate mixture by mixing the particulate material with the precursor material of the polymeric bonding agent and (a) neither part of the hardener component, (b) one part of the two-part hardener component provided that the one part of the two-part hardener component is insufficient to cure the precursor component within a predetermined time, or (c) both parts of the two-part hardener component in an amount which is insufficient to cure the precursor component within a pre-determined time; (v) forming a border region of the second particulate mixture along the edge of the first uncured surface such that a first portion of the second particulate mixture is intermixed with a portion of the first particulate mixture and a second, opposed portion of the second particulate mixture is exposed; (vi) allowing or causing the precursor component of the first particulate mixture to cure or partially cure; (vii) preparing a third particulate mixture by mixing the particulate material with the polymeric binder comprising both parts of the two-part precursor component and the hardener component; and (viii) joining a second bonded particulate surface to the first bonded particulate surface by intermixing a portion of the third particulate mixture with the exposed portion of the second particulate mixture such that the second part of precursor component present in the third particulate mixture intermixes with the second particulate mixture of the border region and both the second and third particulate mixtures are capable of being cured to form bonded particulate surfaces.

It will be appreciated that in the second aspect of the invention, the second particulate mixture omits both parts or one part of the two-part hardener component. This prevents the second particulate mixture from curing or being cured in the same way that the omission (or reduction) of the hardener in the first aspect of the invention prevents the second particulate mixture from curing or being cured. The omitted part or parts of the hardener component is provided by the third particulate mixture and when the third particulate mixture is intermixed with the border region, the omitted part or parts of the hardener material is incorporated into the second particulate mixture and permits both the second and the third particulate mixtures to cure or be cured.

For example, where the polymeric bonding agent is a polyurethane, the hardener may comprise an isocyanate reagent and a catalyst. According to the second aspect of the invention, the second particulate mixture may omit both the reagent and the catalyst. In this embodiment, the precursor material clearly would not cure to form the final polymeric bonding agent. Alternatively, the second particulate mixture may omit the reagent or the catalyst. In this embodiment, the omission of the reagent (e.g. the isocyanate), but the inclusion of the catalyst would result in the precursor material not being cured. Depending on the reactive nature of the precursor component and the reagent of the hardener component, the omission of the catalyst may or may not prevent the precursor material from being cured within a pre-determined period of time. In such an embodiment, the user would have to determine if a reduced amount of the reagent would be required as well as the omission of the catalyst to prevent the precursor component being able to cure within the pre-determined time period. In a further alternative embodiment, both parts of the hardener component may be included in the second particulate mixture, but in reduced amounts such that the precursor component is not able to cure or be cured within the pre-determined period of time.

The optional features discussed above in connection with the first aspect of the invention may form part of the second aspect of the invention. Thus, all such features are also considered to be optional features of the second aspect of the invention.

According to a third aspect of the invention, there is provided a kit of parts including a particulate material, a precursor component of a polymeric bonding agent, a hardener of the polymeric bonding agent, a set of instructions for preparing a first and third particulate mixtures comprising the particulate material, the precursor component and the hardener, and a set of instructions for preparing a second particulate mixture comprising the particulate material, the precursor material and either no hardener or insufficient hardener to cure the precursor material within a pre-determined time.

As noted above, the optional features discussed above in connection with the first aspect of the invention may form part of the third aspect of the invention. Thus, all such features are also considered to be optional features of the third aspect of the invention.

According to a fourth aspect of the invention, there is provided a kit of parts including a particulate material, a precursor component of a polymeric bonding agent, a two-part hardener of the polymeric bonding agent, a set of instructions for preparing a first and third particulate mixtures comprising the particulate material, the precursor component and the two-part hardener, and a set of instructions for preparing a second particulate mixture comprising the particulate material, the precursor material and (a) neither part of the two-part hardener, (b) one part of the two-part hardener provided that the one part of the two-part hardener component is insufficient to cure the precursor component within a predetermined time, or (c) both parts of the two-part hardener component in an amount which is insufficient to cure the precursor component within a pre-determined time.

Again, the optional features discussed above in connection with the first aspect of the invention may form part of the fourth aspect of the invention. Thus, all such features are also considered to be optional features of the fourth aspect of the invention.

According to a fifth aspect of the invention, the second particulate mixture is prevented from curing within a pre-determined time by the absence of heat energy. As noted above, the curing of a polymeric bonding agent may require heat and the curing of a second particulate mixture may be prevented or delayed if insufficient heat energy is provided. Thus, the fifth aspect of the invention provides a method of joining a bonded particulate surface, the method including (i) preparing a first particulate mixture by mixing a particulate material with a polymeric bonding agent comprising a precursor component and a hardener component; (ii) applying the first particulate mixture to a substrate to form a first uncured surface; (iii) identifying an edge of the first uncured surface to be joined; (iv) preparing a second particulate mixture by mixing the particulate material with the precursor material of the polymeric bonding agent and the hardener component; (v) forming a border region of the second particulate mixture along the edge of the first uncured surface such that a first portion of the second particulate mixture is intermixed with a portion of the first particulate mixture and a second, opposed portion of the second particulate mixture is exposed; (vi) preventing or delaying the curing of at least the second particulate mixture by maintaining the temperature of the second particulate mixture below a minimum temperature required to cure the polymeric bonding agent of the second particulate mixture; (vii) preparing a third particulate mixture by mixing the particulate material with the polymeric bonding agent comprising the precursor component and the hardener component; and (viii) joining a second bonded particulate surface to the first bonded particulate surface by intermixing a portion of the third particulate mixture with the exposed portion of the second particulate mixture and allowing the temperature of the second and third particulate mixtures to rise above the minimum temperature to cure the precursor component of both the second and third particulate mixtures.

Once again, the optional features discussed above in connection with the first aspect of the invention may form part of the fifth aspect of the invention. Thus, all such features are also considered to be optional features of the fifth aspect of the invention.

The skilled person will appreciate that the features described and defined in connection with the aspect of the invention and the embodiments thereof may be combined in any combination, regardless of whether the specific combination is expressly mentioned herein. Thus, all such combinations are considered to be made available to the skilled person.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figures la and lb illustrate the process of joining a second bonded particulate surface to a first bonded particulate surface; and Figures 2a, 26 and 2c illustrate the process of joining three bonded particulate surfaces.

For the avoidance of doubt, the skilled person will appreciate that in this specification, the terms "up", "down", "front", "rear", "upper", "lower", "width", etc. refer to the orientation of the components as found in the example when installed for normal use as shown in the Figures.

Figure la shows a substrate 2 upon which a first bonded particulate surface 4 has been applied. The bonded particulate surface is formed by mixing a suitable aggregate with a polyurethane polymer available from Apollo Construction Solutions to form a first particulate mixture. The polyurethane polymer comprises a polyol precursor component (A9298) and an aromatic isocyanate hardener component (A9578). The polymer remains fluid for about 35 minutes after mixing the polyol precursor with the isocyanate hardener and takes about 3 hours at 20°C to cure. A catalyst may be added to reduce the time to cure.

Towards the end of the working day a leading edge 6 of the uncured first surface 4 is identified. A second particulate mixture is prepared which comprises the aggregate and the polyol precursor component (A9298), but no isocyanate hardener component (A9578). The second particulate mixture is applied to the substrate 2 to form a border 8 along the leading edge 6 of the uncured first surface 4. The application process causes a portion of the border 8 adjacent to the leading edge 6 to become intimately intermixed with the uncured first mixture of the first surface 4 and results in an exposed edge 10 of the border 8.

The uncured first surface 4 and the border 8 are left overnight during which time the isocyanate hardener component (A9578) and the precursor polyol component (A9298) of the first mixture react together to form a cured polyurethane polymer and results in the formation of the first bonded particulate surface. However, the second mixture, which is intimately mixed with the first bonded particulate surface and which has no isocyanate component remains in its pliable, uncured state.

In the morning a third particulate mixture is prepared which is identical to the first particulate mixture. Additionally, a portion of the border 8 which is distal to the leading edge 6 is removed such that the border 8 has a width of about 20mm.

The third particulate mixture is then applied to the substrate 2 and the portion of the applied third particulate mixture adjacent to the exposed edge 10 of the border 8 is intimately mixed with the second particulate mixture forming the border 8.

As shown in Figure lb, the third mixture is applied to the substrate to form a second uncured surface 12, which is then allowed to cure to form a second bonded particulate surface. The intimate mixing of the third particulate mixture with the border 8 effectively adds an amount of the isocyanate hardener component to the second particulate mixture which forms the border 8. This subsequent addition of the isocyanate component causes the second mixture to cure at the same time as the third particulate mixture.

As the leading edge 6 of the first surface is intimately mixed with one side edge portion of the border 8 and the exposed edge 10 of the border is intimately mixed with the adjacent edge of the second surface, there are no visible joins between the first surface 4 and the border 8 or between the border 8 and the second surface 12. The overall impression is that the first surface 4, the border 8 and the second surface 12 together form a single, continuous surface.

Figures 2a, 2b and 2c show a similar process, but in the context of a substrate 102 that has a surface area which requires three days to cover it with the bonded particulate surface.

As shown in Figure 2a, a first particulate surface 104 is applied to the substrate 102 in the same way as described above. In this case, the first surface defines two leading edges 106a, 106b. A border 108 of a second particulate mixture which again has the isocyanate hardener component omitted is formed along both the leading edges 106a, 106b. The first particulate surface 104 and the border 108 are left overnight during which time the precursor polyol component and the isocyanate hardener component of the first particulate mixture react with each other to form a cured polyurethane polymer while the second mixture which forms the border 8 remains in an uncured state.

Figure 2b shows the second day's work, which involves the addition of a second particulate surface 112 to the substrate 102. The second particulate surface is applied adjacent to the border 108 such that the third particulate mixture which forms the second particulate surface is intimately intermixed with the uncured border 108.

A fourth particulate mixture is prepared which is identical to the second particulate mixture and a second border 116 is applied adjacent to a leading edge 114 of the second particulate surface 112. The substrate is again left overnight, during which time, the third particulate mixture which forms the second surface 112 and the second particulate mixture which forms the first border 108 both cure, but the second border 116 remains in its uncured stated as the fourth particulate mixture which forms the second border 116 does not include the isocyanate hardener component necessary to cure the polyol precursor component.

Figure 2c shows the third day's work which comprises the preparation of a fifth particulate mixture that is identical to the first and third particulate mixtures and the application of the fifth particulate mixture to the remainder of the substrate 102 to form a third particulate surface 120.

As noted above, the fifth particulate mixture is intimately intermixed with the fourth particulate mixture which forms the second border 116. This results in the fourth particulate mixture of the second border 116 becoming cured as the polyol precursor component and the isocyanate hardener component of the fifth particulate mixture cures.

The interlinked arrangement between the first particulate surface 104, the first border 108, the second particulate surface 112, the second border 116 and the third particulate surface together forms an arrangement that gives the appearance of a single continuous surface with no visible joints or seams.

Claims

Claims 1. A method of joining a bonded particulate surface, the method including (i) preparing a first particulate mixture by mixing a particulate material with a polymeric bonding agent comprising a precursor component and a hardener component; (ii) applying the first particulate mixture to a substrate to form a first uncured surface; (iii) identifying an edge of the first uncured surface to be joined; (iv) preparing a second particulate mixture by mixing the particulate material with the precursor material of the polymeric binder and either no hardener or insufficient hardener to cure the precursor component of the polymeric bonding agent within a pre-determined time; (v) forming a border region of the second particulate mixture along the edge of the first uncured surface such that a first portion of the second particulate mixture is intermixed with a portion of the first particulate mixture and a second, opposed portion of the second particulate mixture is exposed; (vi) allowing or causing the precursor component of the first particulate mixture to cure or partially cure to provide a first bonded particulate surface; (vii) preparing a third particulate mixture by mixing the particulate material with the polymeric bonding agent comprising the precursor component and the hardener component; and (viii) joining a second bonded particulate surface to the first bonded particulate surface by intermixing a portion of the third particulate mixture with the exposed portion of the second particulate mixture such that the hardener component of the third particulate mixture is able to cure the precursor component of both the second and third particulate mixtures.
2. A method according to Claim 1, wherein the polymeric bonding agent is a polyurethane, the precursor component includes a polyol, and the hardener includes an isocycanate.
3. A method according to Claim 2, wherein the hardener further includes a catalyst selected from a tertiary amine and metallic compound.
4. A method according to any of Claims 1 to 3, wherein the particulate material comprises aggregate, marble, glass, quartz, rubber or mixtures thereof.
5. A method according to any of Claims 1 to 4, wherein the particulate material has an average diameter of from 0.1mm to 50mm.
6. A method according to Claim 5, wherein the average diameter is from 1mm to 20mm. 5
7. A method according to any of Claims 1 to 6, wherein the border region is formed with a width of 1 to 20cm.
8. A method of joining a bonded particulate surface, the method including (i) preparing a first particulate mixture by mixing a particulate material with a polymeric bonding agent comprising a precursor component and a two-part hardener component; (ii) applying the first particulate mixture to a substrate to form a first uncured surface; (iii) identifying an edge of the first uncured surface to be joined; (iv) preparing a second particulate mixture by mixing the particulate material with the precursor material of the polymeric bonding agent and (a) neither part of the hardener component, (b) one part of the two-part hardener component provided that the one part of the two-part hardener component is insufficient to cure the precursor component within a predetermined time, or (c) both parts of the two-part hardener component in an amount which is insufficient to cure the precursor component within a pre-determined time; (v) forming a border region of the second particulate mixture along the edge of the first uncured surface such that a first portion of the second particulate mixture is intermixed with a portion of the first particulate mixture and a second, opposed portion of the second particulate mixture is exposed; (vi) allowing or causing the precursor component of the first particulate mixture to cure or partially cure; (vii) preparing a third particulate mixture by mixing the particulate material with the polymeric binder comprising both parts of the two-part precursor component and the hardener component; and (viii) joining a second bonded particulate surface to the first bonded particulate surface by intermixing a portion of the third particulate mixture with the exposed portion of the second particulate mixture such that the second part of precursor component present in the third particulate mixture intermixes with the second particulate mixture of the border region and both the second and third particulate mixtures are capable of being cured to form bonded particulate surfaces.
9. A method according to Claim 8, wherein the polymeric bonding agent is a polyurethane, the precursor component includes a polyol, and the hardener includes an isocycanate and a catalyst.
10. A method according to Claim 9, wherein the catalyst is selected from a tertiary amine and metallic compound.
11. A method according to any of Claims 8 to 10, wherein the particulate material comprises aggregate, marble, glass, quartz, rubber or mixtures thereof.
12. A method according to any of Claims 8 to 11, wherein the particulate material has an average diameter of from 1mm to 50mm.
13. A method according to any of Claims 8 to 12, wherein the border region is formed with a width of 1 to 20cm.
14. A kit of parts including a particulate material, a precursor component of a polymeric bonding agent, a hardener of the polymeric bonding agent, a set of instructions for preparing a first and third particulate mixtures comprising the particulate material, the precursor component and the hardener, and a set of instructions for preparing a second particulate mixture comprising the particulate material, the precursor material and either no hardener or insufficient hardener to cure the precursor material within a predetermined time.
15. A kit of parts including a particulate material, a precursor component of a polymeric bonding agent, a two-part hardener of the polymeric bonding agent, a set of instructions for preparing a first and third particulate mixtures comprising the particulate material, the precursor component and the two-part hardener, and a set of instructions for preparing a second particulate mixture comprising the particulate material, the precursor material and (a) neither part of the two-part hardener, (b) one part of the two-part hardener provided that the one part of the two-part hardener component is insufficient to cure the precursor component within a predetermined time, or (c) both parts of the two-part hardener component in an amount which is insufficient to cure the precursor component within a pre-determined time.