Field of the invention

The present invention relates to a novel type of sensor and sensor material; detection and fuse module that is integrated within an electronic monitoring system for detecting the presence of materials (e.g. contaminants), such as hydrocarbons used as solvents, fuels, cleaners, oils and greases.

A novel type of chemically sensitive electroconductive sensor and fuse element is described including methods of use and manufacture thereof and the use of the sensor device in the monitoring of pollution, e.g., hydrocarbon pollution.

Background of the invention

In 1999 there were over 5000 pollution incidents in England alone, which caused the contamination of land, running water or drainage systems. Soil contamination is defined as, inter alia, the introduction to the soil environment of chemical compounds, such as hydrocarbons or other materials, which negatively affect or alter soil function. Soil contamination can occur through deposition from the atmosphere (e.g. acid rain), deliberate application (e.g. fertiliser) but most commonly through spillage, leakage or illegal dumping, Hydrocarbon pollution is commonly found during the removal of underground storage tanks, at redundant fuel filling stations.

The Institute of Petroleum has produced guidelines for soil, groundwater and surface water protection at petrol filling stations. Hydrocarbon fuel entering the soil may have a detrimental or fatal effect on flora and fauna within the contaminated area. Furthermore, soil and the substrate beneath it may contain water that ultimately feeds a water supply for people or animals or other aquatic habitats or wetlands. In addition, some components of motor fuels have significant solubility in water and can therefore pollute significant volumes of water once dissolved.

In Europe EC Directive 80/60 EEC specifies that there should be no entry of substance such as mineral oils and hydrocarbons into groundwater. In the UK, DEFRA issued guidance in a Code of Practice Groundwater Protection at petrol stations and other fuel dispensing facilities involving underground storage tanks. According to the Institute of Petroleum the principle sources of loss of product containment, and run off to water courses involves:

Leaks from:

• Under dispenser valves and flexible couplings.

· Pipe work

• Tanks and offset fill pipes.

• Faulty oil/water separator operation.

Spills from:

· Customer refueling, including leaking car fuel tanks.

• Filling of petrol station underground storage tanks directly or below ground level offset fill points.

• Filling of petrol filling station underground storage tanks via above ground level offset fill points.

* Overfilling of portable containers. Various approaches aimed at detecting leakage of potentially harmful liquid pollutants based on pollutant-sensitive materials have been reported including those described in US Patent No. 4,351,642; US Patent application No. 2002/063629; US Patent No. 5,514,338 and US Patent No. 4,682,156. There are various monitors and leak detection systems available, the most effective of which generally monitor air pressure or vacuum between the skins of a double skinned pipe or tank. However, such monitors are unsuitable in detecting spills and leaks from valves and the like. Other monitors analyse the rate of change in the contents of a tank however, these again are unsuitable in detecting spills and may have a slow reaction time, depending upon how frequently the data is gathered. In addition, their performance is often unsatisfactory when a tank is in use, e.g. in the dispensing of fuel.

In respect of the continuous monitoring and detection of hydrocarbon leaks, various approaches are known. Continuous oil sensing cable can be laid to cover pipelines and storage facilities and an alarm can be triggered if a leak is detected. Cables vary in length depending on the total coverage that is needed and such systems can be built with location- detection functionality. The complexity and cost of continuous sensors can be high and difficulties can be encountered if small sections malfunction or become damaged. The installation of long lengths of detection cable can also be prohibitively costly.

There is therefore a need for an alternative form of monitoring device or system, which overcomes or mitigate the problems of existing systems. Summary of tie Invention

la order to provide a cost-effective and versatile detection system that obviates the need for continuous sensing cables and enables sensor modules to be quickly removed, replaced or repositioned, we have designed a sensor material, system and method that may be utilised within a small "fuse" module that is designed to be installed as part of a distributed network of sensors protecting critical installations. In certain embodiments, each fuse module resembles a domestic electrical fuse wherein there is positioned a thin polymer electroconductive fuse element held firmly at its extremities by connectors. The fuse module may be designed in such a manner that an aperture is provided through which a sample is able to pass to contact the fuse element Alternatively, the sensor material may be delivered as an exposed strip that can come into contact with the sample.

Thus, according to a first aspect of the invention there is provided a fuse module for detecting a presence of a contaminant comprising:

an electroconductive fuse element comprising a base polymer that is degradable in the presence of the contaminant and an electroconductive polymer dispersed within the base polymer;

wherein the electroconductive polymer is effective to provide a change in an electrical property of the electroconductive fee element indicative of the presence of the contaminant.

The fuse module of the invention is desirably replaceable and inter-changeable. The invention especially provides a replaceable and inter-changeable fuse module as hereinbefore described wherein the contaminant is a hydrocarbon. The sample for use with the devices and methods described herein may be in a liquid, vapour, semi-solid, or solid state, as is appropriate for the particular application. In one embodiment, the device is configured for detection of a contaminant in a liquid or vapour state. The fuse module or element forms part of an electronic circuit, which is energised by an appropriate power supply including that provided by an integrated photovoltaic cell or a low cost battery. The electronic circuit may be linked to a transmitter/transponder, which transmits a remote signal to a control centre, person, vehicle, building, etc. The fuse element may form part of a wireless sensor network built from multiple nodes where each node is connected to one or more sensors. Each sensor network node typically consists of a radio transceiver with an internal antenna or connection to an external antenna, a microcontroller, an electronic circuit for interfacing with the sensors and an energy source, usually a battery or alternative power supply.

The telemetry system is capable of signalling the detection time, magnitude, species (i.e. type of hydrocarbon) and location identifying date for the sensor. The telemetry system may be based on any suitable data transfer mechanism including but not limited to wireless systems (e.g. those using radio or infrared systems), telephone or computer network, optical link or other wired communications. The system can utilise GSM (Global System for Mobile communications) networks by means of SMS (Short Message Service) to receive and transmit telemetry data.

The fuse element for use in the fuse module of the present invention is novel per se.

Thus, according to a further aspect of the invention mere is provided an electroconductive fuse element for use, inter alia, in a fuse module as hereinbefore described. The fuse element is sufficiently robust to withstand environmental degradation (e.g. UV exposure, temperature extremes, weathering, mechanical handling as well as the drag force of liquid medium, for example, over its exposed surface.

The amount of electrically conductive polymer present in the composite (electroconductive fuse element) may vary and may depend upon, inter alia, the required sensitivity of the sensor. However, in one aspect of the invention the amount of electroconductive polymer present is < 15% w/w. In a particular aspect of the invention the composite may comprise from about 2 to about 15% w/w of the electroconductive polymer, alternatively from about 5 to about 15% w/w of the electroconductive polymer, or from about 8 to about 15% w/w of the electroconductive polymer, e.g. from about 8 to about 13% w/w of the electroconductive polymer. It will be understood by the person skilled in the art that any conventionally known conductive polymer may be used in the composite material of the invention. Indeed, it is within the scope of the present invention for a mixture of electroconductive polymers to be used. Examples of the electroconductive polymers include, but shall not be limited to, polyaniline, poly(para-phenylene), poly(para-phenylenevinylene), polythiophene, polyfuran, polypyrrole, polyselenophene, poly i sothianaphthene, polyphenylene sulphide, polyacetylene, polypyridylvinylene and polyazine, which are electroconductive and are either substituted or non-substituted, and combinations thereof. A preferred group of electroconductive polymers is polythiophene, polypyrrole, PEDOT/PSS (poly(3,4- emylenedioxythiophene) poly(styrenesulfonate)) and polyaniline. However, in a preferred aspect of the invention the electroconductive polymer is a polyaniline. The polyaniline used in this aspect of the invention is commercially available or may be synthesised using conventional methods known per se.

In order to provide a system capable of acting as a mechanically robust electroconductive sensor element in the form of a continuous filament, fibre, film or tape, the electroconductive sensor element comprises an intimate blend of a base polymer material, e.g., natural rubber (polyisoprene, typically poIy(cw- 1 ,4-isoprene) and an electrically conductive polymer, e.g., polyalinine (PANi). The presence of the electrically conductive polymer substantially increases the overall electrical conductivity of the sensor element as compared to the base polymer.

The electroconductive sensor described herein is capable of providing a timely and measurable change in properties in the presence of the contaminant In one embodiment, the electroconductive fuse element provides a rapid measurable change in resistance upon contact with the contaminant.

The base polymer material may alternatively be selected from another suitable polymer e.g. styrene butadiene rubber (SBR), butyl rubber (IRR - copolymer of isobutylene and 1 to 3% isoprene produced by cold cationic solution polymerization), EPDM (Ethylene Propylene Diene Monomer) rubber, thermosetting rubbers and RTV (room temperature vulcanizing) rubbers, e.g. silicone rubbers.

In certain embodiments, the base polymer material is degradable in the presence of a contaminant upon contact with the electroconductive element. By "degradable" as used herein, it is meant that the base polymer material is susceptible to a change in one or more physical and/or chemical properties upon contact with a sample comprising a contaminant. The change may be reversible or non-reversible. The change in physical and/or chemical properties may include, but is not limited to, a change in the structure of the base polymer material, including, but not limited to, the breakdown or cleavage of the bonds of the base polymer material, chemical composition, state (e.g. neutral to polar), etc. This breakdown of the base polymer by the contaminant causes a corresponding change in the electrical properties of the sample, namely, the electrical resistance of the base polymer and the electroconductive fuse element. The change of physical properties may further include, but is not limited to, a change in form, dimensions, shape, tensile strength, modulus, etc. The change may be reversible or non-reversible.

As used herein, the "contaminant" may be defined as a component that will cause a change in one or more chemical and/or physical properties of the base polymer and/or the electroconductive ruse element. For example, the present inventors have found that when hydrocarbons come into contact with natural and/or synthetic rubber materials, such materials will degrade and a corresponding change in a physical and/or chemical property of the natural rubber materials can be measured. When a conductive polymer is dispersed within the rubber material, the changes in electrical resistance and conduction of the combined materials in the electroconductive sensor can be more easily measured and with greater sensitivity.

As used herein, the term "hydrocarbon or hydrocarbons" refers to saturated and unsaturated hydrocarbons, cycloalkanes and aromatic hydrocarbons. Hydrocarbons include, but shall not be limited to, petroleum-based fuels, such as, gasoline, diesel fuel, kerosene, jet fuel, lubricants, greases, oils and the like, biofuels (e.g. bioethanol and biodiesel). Natural gas,

-S- LPG (Liquid Petroleum Gas) and fuel vafiours or ftimes are also included. However, the present invention is not so limited, and the electroconductive fuse element as described herein may be utilised to detect other contaminants that cause a change in one or more chemical or physical properties (degradation) of the base polymer material and/or electroconductive fuse element. In another embodiment, for example, the contaminant may be one or more organic solvents, for example, such as benzene, toluene, acetone, or the like.

The relative composition of the electroconductive fuse element is preferably in the proportion of from about 25:75 to about 96:4 base polymer material to electroconductive polymer material. In one embodiment, the relative composition comprises natural rubber (polyisoprene) and polyaniline in a ratio of from about 25:75 to about 96:4. The polymer fuse element of the present invention typically exhibits low electrical resistances before use of the order of 0.30-0.50±0.01 ΜΩ with electrical resistance increasing as a result of hydrocarbon degradation by oil, petroleum and other hydrocarbons as hereinbefore defined. The degradation can also lead to swelling and/or rupture as the mechanical properties of the fuse element deteriorate. In the case of rupture, the failure time of the sensor may be increased by pre-tensioning the fuse element such that the thickness of the fuse element is reduced. Initially, the fuse element is produced with thicknesses of the order of 15-100 μιη (without backing materials).

To increase the area over which the fuse system is able to detect hydrocarbons, porous fibre assemblies (e.g. fabrics), yarns or foams are provided that enable liquid hydrocarbons to be directionally transported towards the fuse element by means of capillarity (wicking)/or forced flow depending on the particular installation. This can perform a number of functions: it can provide a means of increasing the concentration of the contaminant reaching the sensor, it can increase the rate at which the contaminant reaches the sensor (depending on the wicking rate) and it can increase the overall area that can be monitored by a sensor element. Furthermore, it allows the area that can be monitored to be increased without increasing the physical dimensions of the sensor itself.

Nonwoven fabrics produced from glass fibre or polypropylene fibres are particularly suitable including SMS (spunbond-meltblown-spunbond) polypropylene nonwoven fabrics, provided as single fabrics or multi-layered fabrics. Staple and continuous filament yams are also suitable including braided yams comprised of hydrophobic polymers or glass fibre in which the constituent fibres are substantially oriented in the direction of the longitudinal axes of the yam.

In one aspect of the present invention, there is provided a sensor material and element. In a second aspect there is a replaceable and inter-changeable fuse module that is integrated within an electronic monitoring system for detecting the presence of a contaminant, e.g., hydrocarbons that consists of: an electroconductive fuse element comprising of a filament or thin film tape composed of a material consisting of at least two components. The first component is a supporting matrix of a hydrocarbon sensitive polymer and the second component is an electro-conductive polymer that is dispersed within the first component,

In a third aspect of this invention there is nodal/telemetry network that enables uni- or bidirectional signalling and/or control.

Furthermore, in another aspect of this invention, there is provided a porous oleophilic fabric or foam, through which a contaminant, e.g., a hydrocarbon liquid, may be directionally transported toward the electroconductive fuse element by means of capillary action. Additionally, a power supply, a digital detection circuit and/or a transponder unit enabling remote signalling and location detection to the electronic monitoring system may be provided.

The base polymer may be any suitable material that is susceptible to degradation in the presence of the contaminant. Thus, for example, for a hydrocarbon sensor, it is desirable that the base polymer is susceptible to hydrocarbon degradation. In one embodiment, the base polymer comprises an elastomer selected from one or more of polyisoprene (natural rubber), styrene-butadiene rubber, butyl rubber, chlorosulfonated polyethylene, silicone rubber, ethylene-propylene rubber, and mixtures thereof. Elastomer materials, such as natural rubber (including natural rubber in its synthetic form (polyisoprene)), are particularly suitable base polymers for the present invention when hydrocarbons are the targeted contaminant as elastomer materials, particularly natural rubber, have a particularly high rate of degradation in the presence of hydrocarbons.

The present inventors have found that polymers, particularly, polyaniline, are particularly useful as the electroconductive material because they do not significantly compromise the strength of the fibre or film-forming base polymer such that the resulting sensor material is sufficiently mechanically robust to withstand installation and use phase forces. While it is known to mix a carbon black material with rubber to form a device for sensing a hydrocarbon, as in US Patent No. 5,514,338, the presence of the carbon black filling material limits the strength of the rubber base material. Improved sensitivity and/or response time to the presence of the contaminant may be achieved by making the base material relatively thinner. However, prior art devices using carbon black in rubber are limited by the mechanical properties (e.g. strength) of the composite material. The present invention thus provides a capability for increased sensitivity and response time when compared to prior art devices. Furthermore, carbon black may not be useful for many applications because it is reactive and may become volatile in the presence of some contaminants or materials in the local environment In contrast, embodiments of the present invention utilise electroconductive polymers, which are selected to have no such adverse reaction to the contaminant being detected or to any material in the local environment. An important advantage of using polyamlme is that the classical Mgh percolation threshold for the onset of electrical conductivity associated with globular carbon black filled plastics, does not exist. Additionally, plasticised polyaniline compositions help to improve melt processing performance by reducing the melt-viscosity, reducing the processing temperature and shortening processing time. The improved melt flow properties axe beneficial for moulding and extruding thin films and products with complex shapes. Thus, it is particularly desirable for the hydrocarbon sensitive polymer used in the composite of the present invention to be an elastomer material, such as natural rubber (polyisoprene). The rubber may be one or more natural or synthetic rubbers and mixtures thereof. However, we have found that a material high in natural rubber achieves the desired sensitivity to hydrocarbons. It will be understood that a material comprising the synthetic form of natural rubber, polyisoprene, e.g. with a molecular weight of 100,000 to 1,000,000, may be suitable for use in the present invention. When using natural rubber as the base polymer material, the electroconductive sensor element may exhibit a rapid, measurable change in resistance in the presence of the hydrocarbons. The hydrocarbon sensitive polymer should be sensitive to one or more hydrocarbons. Preferably, the sensitivity should allow the hydrocarbon to be sensed when in different phases, optionally simultaneously. Thus, the hydrocarbon sensitive polymer may be sensitive to hydrocarbons in the liquid and/or vaporous state.

Natural rubber is advantageous in that, inter alia, when mixed with a compatible solution or dispersion of an electroconductive material a substantially uniform blend is achieved.

It is beneficial to have a uniform blend of the materials to ensure reproducible sensitivity for the system. Methods of ensuring uniform blending or composite formation using such materials as required for the blends or composites of the present invention will be known to those skilled in the art of polymer blending and composite formation.

Further components may be introduced to advantageously ensure the final sensor form is achieved and/or to enhance its properties, e.g. ternary mixtures of polymers. Additives used in rubber processing to assist in miscibility may also be used.

In one embodiment, ammonium hydroxide may be added to the blend of the base polymer material and the electroconductive material to prevent agglomeration of particles in the mixture, e.g., latex particles. Any workable amount of ammonium hydroxide may be utilized depending on amount of composite being formed. In one embodiment, 1-6% by volume of a 35% by volume ammonium hydroxide solution may be provided to the blend of the base polymer material and the electroconductive material. The sensor material of the invention may be extruded into a filament, fibre or a film. Especially preferred is an extruded film. It may also be coated, electrospun, electrosprayed, printed (including by means of digital ink jet printing), cast in to film, blown, moulded or formed in to foams, nonwoven or other textile assemblies.

In one embodiment of the invention the sensor material, e.g. an extruded film, is coated onto a support layer, such as, a woven, knitted, or nonwoven fabric. The support layer may comprise a variety of materials and may optionally be a composite of materials. One object of the support is to act as a wicking material for the hydrocarbon, thus increasing the area over which the sensor is operational. Another object is to absorb and retain hydrocarbon from the area surrounding the sensor element. A further object is to provide mechanical reinforcement of the sensor element. Thus, a porous support material that enables permeation and transport of liquids is especially desirable. The degree of porosity may vary, but may be from about 50 to about 99.5%, or from about 60 to about 99.5%, or from about 70 to about 90%, or from about 75 to about 85%. Preferably, the material surface is oleophilic. This may be imparted by appropriate selection of polymer material or by surface fictionalisation using coatings, plasma treatment or masterbatch additives that migrate to the surface of the material during processing. Alternatively, the sensor material is coated onto a reinforcing medium or scrim that is typically comprised of a woven, knitted, nonwoven or film. Once formed, this composite structure is attached or adhered to a secondary support layer that is capable of providing wicking and absorbency.

It is desirable for the support material to itself be resistant to hydrocarbons so that when the electroconductive composite material degrades the whole sensor remains intact. Although a variety of woven and/or nonwoven materials may be used, specific materials, which may be mentioned are glass, silica, polypropylene, polyamides, polycarbonates, metals, ceramics and mixtures thereof. A preferred group of support materials comprises one or more of polypropylene, polyamide and polycarbonate, and mixtures thereof. The thickness of the support material may vary, although varying the thickness of the support may affect the sensitivity of the sensor. Thus, an optimum thickness of the support may be from 0,05 to 1.0mm or 0.1 to 0,8mm or 0.25 to 0.5mm. In addition the use of a relatively thin support material allows the sensor, i.e. the electrocoeductive sensor element and the support, to be conformable and may therefore be used in such a way where it may be, for example, wrapped around a fuel pipe or storage tank.

In addition, natural robber is advantageous in that the sensor may be of tow density, lightweight, conformable and entirely polymeric in nature. One advantage of using natural rubber as the base polymer material is that, inter alia, it may be bonded to the support material without the need to use adhesives. Thus is advantageous in that the use of adhesive may binder the increase of resistance once the hydrocarbon sensitive polymer has degraded and/or interfere with the permeation of hydrocarbons to the sensor.

Furthermore, natural rubber is insensitive to water and therefore may be used in a situation where it is exposed to the environment without fear of degradation. For an "external" sensor such as this it may be desirable to include one or more UV absorbers, etc, to prevent unwanted degradation by UV light and other environmental agencies. The composite material may optionally be made using conventional methods known per se.

However, according to a yet further aspect of the invention we provide a method of making the composite material as hereinbefore described which comprises the steps of;

(i) mixing an electroconductive polymer with a base polymer such that the electroconductive polymer is dispersed within the base polymer; and

(ii) curing the mixture, optionally at elevated temperature to produce an electroconductive fuse element as hereinbefore described. The electroconductive material, e.g. a polyaniline, may comprise a solution, e.g. with an organic solvent; and the hydrocarbon sensitive polymer, e.g. natural rubber, may comprise, for example, an emulsion.

According to a further aspect of the invention there is provided a hydrocarbon sensor comprising an electroconductive fuse element as hereinbefore described consisting of an electroconductive polymer and a hydrocarbon sensitive base polymer.

According to a further aspect of the invention there is provided a sensor for detecting the presence of a contaminant material (gas, liquid and/or solid), which comprises a second material which is in contact with a third material, wherein a property and/or function of the second material is capable of being influenced by changes in a property and/or function of the third material when the third material comes into contact with the contaminant material to be detected. In preferred embodiments the third material is a base material or supporting matrix as hereinbefore described and the second material is an electroconductive material, preferably an electroconductive polymer as hereinbefore described. The sensor may be provided with a body, which is, for example, capable of being extended thereby allowing different depths to be monitored and also bore holes or surface water layers to be monitored.

According to a further aspect of the invention we provide an alarm system comprising a recognisable alert system in conjunction with a sensor as hereinbefore described.

In one embodiment of this aspect of the invention the sensor may, for example, be connected, optionally wirelessly, to a signal device, such as a transmitter or mobile phone signal (e.g. SMS), which may transmit an alert if a spill or a leak occurs. By such means location-detection is also enabled. Each sensor may be part of an array of sensors so that geographical extent of contamination can be determined.

Thus, features that may be incorporated into the alarm system of this aspect of the invention may include, for example, an audible alarm, a visual alarm; an SMS (short message service) alarm system and, optionally, connection to remote remediation techniques. The system may optionally be tuned to different hazardous chemicals types and also the speed of response may be altered. Additionally, the incorporation of several different detecting elements in one monitoring device to detect several different chemicals at the same time. The use of a range of sensitivities may also be used to give a traffic light system to the device. The system may incorporate a method whereby it would allow the system to be reused into different areas. The invention further provides a kit for detecting the presence of a hydrocarbon contaminant comprising an electroconductive fuse module as hereinbefore described or an electroconductive fuse element as hereinbefore described.

Thus, according to a further aspect of the invention there is provided a method of detecting a hydrocarbon leak or spill which comprises the use of a hydrocarbon sensor as hereinbefore described. Detailed Description of the Invention

The invention will now be described by way of example and with reference to the accompanying drawings in which: -

Figure 1 represents a monitoring device of the invention; and

Figure 2 represents detail of the conductive polymer chemical fuse.

In figure 1, an exemplary embodiment of a fuse module is shown as including a rechargeable battery and electronic circuitry, which are used as a power source and control for the unit. The battery utilises a solar cell, 7 _» to recharge the battery. This battery provides power for a circuit, which includes the conductive polymer fuse, 3. If this breaks an LED/audible alarm, 6 and a SMS signal 2, are triggered. The sensor pod body, 5, is inserted into the ground so that the body containing the fuse module, 4 is below ground.

Figure 2 shows detail of the conductive polymer fuse module at the tip of the sensor pod, which is inserted into the ground. The tip, 10, is a porous spike to allow the contaminant through to the porous layer, 9, at the bottom of the pod above the spike. The contaminant is drawn into contact with the conductive polymer fuse, 3, by a wicking material, 8, which draws the contaminant, e.g., a liquid hydrocarbon contaminant, in from the surrounding area. The rate of wicking of the target contaminant can be controlled by adjusting the surface energy of the support layer material, fibre orientation and pore radius in the fabric during its manufacture.

Various other foms of monitoring device are possible using the same basic approach to fuse module construction.

0063P.OB,Spec<2)