BACKGROUND OF THE INVENTION Natural rubber has been used for a variety of purposes over time however, there are some properties which make rubber more difficult to use in industrial processes and/or make it unsuitable for certain applications. These properties include having a high molecular weight, high viscosity, often being contaminated with naturally occurring proteins and often having a high dirt content. Additionally rubber as it is generally used is cross linked by vulcanisation. These cross-links are difficult to reverse and as a consequence recycling of used rubber products is difficult to satisfactorily achieve.

Natural rubber also has some very desirable properties compared to plastics and some other rubbers which properties include, toughness, dynamic sealing properties, resilience, flex fatigue life, low compression and tension set, and low flex modulus and creep. There has been a desire therefore to blend natural rubber and certain thermoplastics to make a composite having the desirable properties of rubber but processable and reprocessable as thermoplastics.

A considerable amount of work has been conducted into blending natural rubber with a variety of plastics to enhance the properties of natural rubber. The great difficulty witn this blending is that natural rubbers are substantially non-polar and cannot give an effective blend with some plastics. Additionally the high molecular weight and the variation of molecular weight of natural rubber make uniform blending difficult. The greatest success has been in the blending of natural rubbers with a limited range of plastics including polypropylene, polyethylene, polystyrene, methyl-methacrylate, ethyl vinyl acetate and polyvinyl acetate. However limited success has been had blending with increasingly popular plastics including polyamides, polyurethanes, polyesters and acrylonitrile butadiene styrene (ABS). Similar blends have been attempted with synthetic rubbers such as butadiene rubbers and isoprene rubbers.

Blends between thermoplastics and natural or synthetic rubbers have been facilitated in the past in a number of ways by introducing polar compounds into the natural or

synthetic rubber and one such approach has been to introduce acrylonitrile into natural rubbers and synthetic rubbers to facilitate such a blending.

There is, to the knowledge of the inventor, no available system that provides for the capacity to reliably blend natural rubber with a large range of thermoplastics.

OBJECT OF THE INVENTION It is an object of the present invention to provide a rubber matrix that permits the formation of composites of any one or more of a wide range of thermoplastics with natural rubber.

SUMMARY OF THE INVENTION In one broad form of a first aspect the invention could be said to reside in a rubber matrix including a) natural rubber 10-90% (v/v) b) one or more first compatabilisers selected from a group of polymers containing either i) a nitrile group, ii) a halogen, iii) an acetate group, iv) an epoxide, v) a styrene, or vi) an acrylate c) one or more second compatabilisers which are interfacial copromoters selected from a group comprising either i) polyvinyl acetate, ii) ethylene vinyl acetate, iii) polyacrylonitrile or high nitrile resin, iv) acrylamide or polyacrylamide, v) a phenolic resin, vi) an acrylate polymer, vii) a halogenated polymer, viii) maleic anhydride or polymaleic anhydride, or

ix) a bismaleimide.

The rubber matrix may be mixed with a range of thermoplastics to form thermoplastic rubber composites. The thermoplastic may be selected from one or more of the group including, but not limited to polyolefins, polyamides, polyesters, polyurethanes, polystyrene, acrylonitrile butadiene styrene, all of which will be described in detail later.

Preferably the first and second compatabilisers are different.

An advantage of thermoplastics is that they are recyclable and/or reprocessable and can be re-moulded. Preferably the thermoplastic rubber composite formed by mixing the rubber matrix of the present invention with a thermoplastic can similarly be recycled, reprocessed, and/or re-moulded.

The natural rubber is preferably selected from the grades known as deproteinated natural rubber (DP-NR), oil extended natural rubber (OE-NR), peptised natural rubber, superior processing rubber (SP or PA), standard Malaysian rubber (SMR) constant viscosity (SMR-CV), low viscosity (SMR-LV), or general purpose (SMR-GP) grades or ISNR LCV grades. These grades tend to have a low protein and low dirt content.

Most preferably SMR or ISNR LCV grades are used.

The content of natural rubber in the rubber matrix may be between 10 phr and 90 phr (parts per hundred rubber). Preferably the rubber matrix has between 35 phr to 40 phr natural rubber for the desirable elastoplastic properties of the natural rubber to be transferred to a final product. If less than 10 phr of natural rubber is used in the rubber matrix the desirable properties of natural rubber tend not to be inherent in the final product.

It may be desired to replace up to 50% of the total quantity of rubbers with reclaimed rubbers from a variety of sources including but not limited to car tyres. It may also be desired to replace at least a part of the plastic component of the thermoplastic rubber composite with graded recycled plastics.

The molecular weight of natural rubber is high and it is a highly viscous and resilient rubber. The normal process involved with blending natural rubber with plastics is to

break down the molecular weight of natural rubber so as to match it with the size of the plastic in order to get effective blending. However the present invention is believed to work at least in part by preventing the natural rubber, which is a highly resilient material and normally regains its molecular weight, from creating a discontinuous phase between the blending plastic and that of the natural rubber. In the present case it is thought that this problem is overcome by the addition of a polar rubber which also has a lower molecular weight and creates a better base and a better match between the rubber and the plastic phases. The lower molecular weight is thought to reduce and stabilise the viscocity of the rubber phase, which in turn increases the flow characteristics. The polar compounds also are also thought to increase the attractive forces between the plastics and rubber phases. In addition the polar groups increase the resistance of natural rubber to oils and polar petrochemical based fluids.

Depending on the thermoplastic used and the ratios of the components of a final composition, a range of thermoplastic compositions each having different properties may be formed. The properties may be tailored to suit a particular application. Thus a range of soft composites may be formed by compounding the rubber matrix with polyolefins, polyvinyls or polyurethanes for example. In contrast intermediate composites may be produced by compounding the rubber matrix with polyurethanes, polyamides, polyvinyls or polyesters for example. Rigid composites may be produced by compounding the rubber matrix with polyolefins, polyurethanes or polyamides for example.

When the rubber matrix is to be used for soft composites, such as with polyolefins, the natural rubber content in the rubber matrix is preferably about 20-70% and most preferably about 40%, with the rubber matrix and plastics preferably being blended in relative proportions of 5-70 parts to 95-30 parts to a total of 100 parts respectively.

Generally, if the rubber matrix comprises more than 75 parts per hundred of the total composite the flow of the composite will be restricted and a continuous phase may not form in the composite. The plastics in such soft composites might be selected from the group comprising polypropylene, polyethylene, polyvinyl acetate, ethylene vinyl acetate, ethylene propylene plastic (Engage; DuPont), polyurethanes or polyvinyl chloride.

The first compatabiliser is selected to have good natural rubber blending properties, and also to present a polar group for attraction by the second compatabiliser. The first

compatabiliser is also thought to stabilise the viscosity of natural rubber. At least some of the properties of the first compatabiliser will be transferred to the final composition, the degree of which will be determined in part by the amount of first compatabiliser in the final composition.

A nitrile based first compatabiliser may be selected from: an acrylonitrile diene rubber such as nitrile isoprene rubber or nitrile butadiene rubber; nitrile natural rubber; polyacrylonitrile; high nitrile polymer. The amount of nitrile based compatabiliser added to the rubber matrix will be determined by the desired properties of the final composition, but is preferably greater than 10% of the rubber matrix.

The nitrile butadiene, nitrile isoprene and nitrile natural rubber preferably has an acrylonitrile content of over 20%. The nitrile content will improve the oil and fuel resistance of the rubber. Further, the elastic behaviour of the nitrile rubbers becomes poorer as the nitrile content increases however at the same time the polymer becomes more thermoplastic which is advantageous regarding the processability of the compounds. The compatibility with polar plasticisers or polar plastics improves with increasing nitrile content.

High nitrile polymers having a nitrile content of more than about 50% may also be used. For example Barex 210 (B-210) (BP America Inc) is a commercially available acrylonitrile-methyl acrylate-butadiene (70: 21: 9 parts by weight) polymer. These polymers have excellent barrier properties and are useful in packaging solids, liquids and gases of various types.

A halogenated first compatabiliser may be a halogenated polymer selected from: chlorinated rubber; polyvinyl chloride; polychloroprene (Neoprene; DuPont); vinyl diene fluoride. Chlorinated polyethylene or chlorosulphonated polyethylene (e. g.

Hypalon; DuPont) are slow curing polymers that are also suitable halogenated first compatabilisers when used in conjunction with polychloroprene. Alternatively the rubber matrix may be halogenated in situ by the addition of a halogen source such as N- bromosuccinimide. A further alternative is to introduce halogen into the composition by the inclusion of chlorinated paraffin oil. Preferably the halogenated compatabiliser is used in conjunction with a nitrile compatabiliser.

To retain at least some of the desirable properties of the halogenated compatabiliser preferably the halogen containing polymer comprises greater than 15% of the rubber matrix. A rubber matrix containing a halogen based first compatabiliser will be particularly suited to blending with polyvinyl chloride, polyamides, polyurethanes and/or polyesters.

An epoxide based first compatabiliser may be an epoxidised natural rubber preferably formed by the reaction of natural rubber with hydrogen peroxide/formic acid/acetic acid.

Preferably the epoxide based compatabiliser has an epoxide content of 20 to 50% to give a rubber matrix having an epoxide content of 10 to 25%.

An acetate containing first compatabiliser may be selected from: polyvinyl acetate; ethylene-vinyl acetate containing a relatively high vinyl acetate content; a vinyl acetate rubber. Preferably the acetate polymer comprises 20 to 50% of the rubber matrix and more preferably comprises 30%, and the rubber matrix has a vinyl acetate content of greater than 20%.

An acrylate based first compatabiliser may be selected from: an acrylic rubber such as Vamac (Dupont), or one formed from the following monomers: ethyl acrylate; methyl acrylate; methyl methacrylate. Preferably the acrylate compatablilser is used in conjunction with a nitrile compatabiliser in about equal ratios. The combination of acrylic and nitrile first compatabilisers is particularly suited to blending with polyamides or acrylates.

A styrene based first compatabiliser may be selected from: styrene natural rubber; styrene butadiene rubber; styrene isoprene styrene block coploymer (SIS) (e. g. Kraton; Shell); styrene ethyl butylene styrene block copolymer (SEBS). A rubber matrix containing a styrene based first compatabiliser may be particularly suited to blending with a styrene thermoplastic such as polystyrene or an acrylonitrile butadiene styrene (ABS).

A combination of more than one of the first compatabilisers may be used in the rubber matrix so as to impart at least some of the characteristics of each of the compatabilisers onto the rubber matrix. For example nitrile rubbers may impart a degree of swell resistance to the rubber matrix such that a final composition may have increased resistance to oils, fuels and fats. Similarly halogenated rubbers, and in particular

chlorinated rubbers, are fire resistant and therefore incorporation of them into the rubber matrix will increase the fire resistance as well as the swell resistance of the final product. Thus, a preferred combination of first compatabilisers is a nitrile rubber and a chlorinated rubber which will tend to increase the resistance of a final composition to fire and to petrochemical based solvents and oils.

The second compatabiliser is chosen to provide a greater polarity or charge density within the rubber phase of a composite to facilitate blending with thermoplastics that do not readily blend with the first compatabiliser. The choice of second compatabiliser is not restricted to those compounds that can interact with the largely non-polar rubber and still present a polar group. They are selected so as to be able to interact with, for example the polar group presented by acrylonitrile, and then present a further polar group with greater polarity or charge density to thereby increase the range of plastics that can be mixed with the rubber matrix. It has been found that in many instances natural rubber is incompatible with, for example, a nitrile rubber-polar thermoplastic blend. However upon addition of a second compatabiliser it is possible to incorporate natural rubber and achieve a continuous phase thermoplastic elastomer composition.

When polyvinyl acetate, ethylvinyl acetate, acrylamide or polyacrylamide, polyacrylonitrile or high nitrile resin, an acrylate polymer, a halogenated polymer, maleic anhydride or polymaleic anhydride, or a bismaleimide is used as a second compatabiliser it is possible to achieve good compounding with the group including but not limited to polyamides, polyurethanes, polyesters, polystyrene including high impact polystyrene, acrylonitrile butadiene styrene, as well as the more readily blended plastics such as the polyolefins.

Aspects of the present invention involve the formation of two phases, a rubber matrix as a rubber phase and a thermoplastics component in a plastics phase, and the invention thus involves a first mixing of components to form the rubber matrix. Combining the rubber matrix with the plastics phase involves a second mixing of the rubber matrix (rubber phase) with the plastics phase. The rubber matrix is substantially a rubber phase and acts as an intermediate. The rubber matrix can be tailored to be combined with any one of a number of different thermoplastics. Preferably the ratio of rubber phase to plastic phase is between 5: 95 and 90: 10, however compositions having greater than about 75% rubber phase tend to have a high viscosity and do not flow easily and therefore may be of limited use. To achieve thermoplasticity in the final composition

the composition is required to have a continuous plastic phase and therefore the plastic phase should comprise at least 10% of the final composition. These portions are necessary to provide sufficient rubber to give elastomeric compositions and sufficient plastic to provide thermoplasticity. The ratio of rubber to plastic can be altered within these limits to form a composition having the desired characteristics.

The rubber phase (or rubber matrix) is formed first and includes the steps of mixing components of the rubber phase including a) the natural rubber; b) a first compatabiliser and, c) a second compatabiliser and d) any further additives that might be required. The rubber phase is formed in a cold mixing process. Such a cold mixing process will typically be performed at a temperature of less than about 120°C. The cold mixing is thought to reduce the particle size of the natural rubber to below about 501l thus forming an intimate mixture of natural rubber particles dispersed in the rubber matrix. After mixing or masticating the rubber phase is normally viscosity stabilised once it is formed and may be left to mature before inclusion in a second mixing as described below.

The first compatabiliser, apart from providing polarity to the rubber matrix, in particular is thought to stabilise the viscosity of the natural rubber in the matrix and prevent the normal tendency of the rubber to regain its molecular weight thus creating a discontinuity between the plastics phase and the natural rubber. The second compatabiliser is then thought to provide further polarity to the matrix so that a range of polar thermoplastics are compatible with the matrix.

A second mixing may be carried out using any of the known methods such as melt mixing or dynamic vulcanisation. Dynamic vulcanisation is preferred and may be carried out using conventional masticating equipment, for example a Banbury mixer, Brabender mixer, mixing extruder or a twin screw extruder. The conditions of high shear provided under dynamic vulcanisation conditions provides for dispersal of the rubber phase and plastics phase. Thus the mixture of rubber and plastics phases are treated under temperature and time conditions that result in the desired level of crosslinking between the rubber and the plastic. The thermoplastic composition is formed by mixing the plastics phase and the rubber phase and masticating the mix at a temperature sufficient to at least soften the plastic, but more preferably a temperature above the melting point of the plastic. So as to minimise thermal degradation of the rubber matrix it is preferable that the plastic melts at less than 205°C. Representative temperatures may include but are not limited to: for polypropylene 170°C; polyethylene

130-150°C; polyamide 180-200°C; thermoplastic polyurethane 180-200°C; polyester 200°C. It is preferable that the melt temperature of the plastic is less than 205°C because the natural rubber will tend to degrade above this temperature. Heating and masticating at these temperatures is usually sufficient to allow cross link formation.

Compositions of the invention may also be prepared by methods other than dynamic vulcanisation. Thus a fully vulcanised rubber phase may be powdered and mixed with the plastics phase and provided that the rubber particles are small and there is sufficient match between the size of the rubber particles and the plastics, a composition having rubber particles well dispersed in the plastics phase can be formed.

The mixing of the rubber matrix with the plastics phase will require the addition of a curative agent to allow the formation of cross links within the rubber matrix. However it will be understood that when certain plastics such as ethylene vinyl acetate or polyethylene are used there may be some cross linking of the plastic with itself and/or with the rubber matrix. Any of the curative systems typically used in rubber vulcanisation can be used. Thus the curative system may be selected from the group comprising but not limited to: a dimethylol phenol system (e. g. SP1045; Schenctady); a bismaleimide system (HVA2); a bismaleimide MBTS system; a bismaleimide peroxide system; an organic peroxide system; an accelerated sulphur system; a urethane system (e. g. Novar 924); a borane system; a radiation system. Preferably the curative agent is a cross linking agent such as a peroxide bismaleimide system. Alternatively, or in addition, the curative may include an interfacial promoter such as for example phenylene bismaleimide (HVA2, Dupont), ethylene glycol dimethacrylate (Perkalink 401; Akzo Nobel), trimethylo propane trimethacrylate (Perkalink 400; Akzo Nobel), triallyl isocyanourate (Perkalink 300; Akzo Nobel) or triallyl cyanourate (Perkalink 301; Akzo Nobel). The interfacial promoter may also act as stabilisers in an overall peroxide/urethane cross linking system.

An advantage of a peroxide curative system may be the creation of cross links between the plastic and rubber phases when the peroxide is used in conjunction with SARET/HVA2, and use of a peroxide curative system may lead to a composite having improved tensile strength and improved high temperature strength. However peroxide curative systems can not be used in direct contact with polypropylene due to the action of peroxide degrading the plastic, however they may be used in a rubber matrix which is subsequently mixed with polypropylene. Further, it may not be possible to use

peroxide curing systems with maleic anhydride in an open system due to potential for ignition in contact with air. Peroxide curative systems are preferably not used with chloroprene rubbers, in which case magnesium oxide or zinc oxide may be used as curatives preferably in conjunction with phenolic resins.

Any of the peroxide curative systems known in the art may be used in the present invention. The peroxide may be chosen from the group including, but not limited to, dicumyl peroxide, di-tert-butyl peroxide, di (2-tert-butyl peroxy isporopyl) benzene.

The peroxides may be supported on an inert carrier. Peroxide curative systems are less commonly used when the total rubber content in the final composition is less than 15% unless HVA2 or SARET are present. Typically when the total rubber content in the final composition is less than 15%, HVA2 may provide sufficient cross linking however small amounts of peroxide may be used to assist in the cross linking. If HVA2 or SARET are not present the peroxides are likely to degrade the polypropylene and thus the composition may lose the desirable properties.

A sulphur based curative system will not create cross links between the plastic and rubber phases and the resultant composition will have a lower compression set and better tensile properties than a composition having the rubber and plastics phases cross linked.

In compositions where the total rubber matrix is greater than 20% of the overall composition, the curative agents are preferably added to the rubber matrix while masticating, that is at the first mixing stage. In the case where the rubber matrix content is between 10% and 20% of the total composition the HVA2 should be added to the plastic phase and the peroxide to the rubber phase. When there is less than 10% rubber matrix in the total composition peroxide should not be used and other curatives such as an accelerated sulphur system or a phenolic system may be used if required.

The properties of the thermoplastic rubber composition may be modified by the inclusion of additives which are conventional in the compounding of rubbers and/or thermoplastics. Additives that might be used could include heat stabilising chemicals, flame retarding chemicals, peptising agents, fillers, extenders, plasticisers, pigments, accelerators, stabilisers, antidegradants such as anti-oxidants and UV filters, processing aids and extender oils.

Where halogen containing radicals such as tin chloride or chlorinated paraffin oil are used in a composition, magnesium oxide or maleic acid may be added to the composition to act as scavengers and/or pH stabilisers.

Suitable UV filters may be selected from one or more of the group including, but not limited to, Tinuvan P (Ciba Geigy), titanium dioxide or carbon black. Tinuvan P is preferably added according to the manufacturers directions. Titanium dioxide or carbon black are preferably added at about 2.5 parts per hundred parts of the final composition.

Suitable plasticisers may be selected from one or more of the group including, but not limited to, aromatic, naphthenic and paraffinic extender oils, phthalate plasticisers, sulphonamide plasticisers, adipate plasticisers or phosphate plasticisers. Preferred plasticisers are dehydrated castor oil which may be added at 0.8 phr of rubber content, and cumarone and indene resins are ideally suited for the compositions of the present invention at levels up to 5 phr.

Processing aids may include internal lubricants to increase flow and enhance mixing particularly during the mastication stage. Suitable lubricants may include zinc or magnesium salts. Preferably the lubricant is zinc stearate which is added during mastication. The zinc stearate is readily added in the form of zinc oxide (e. g. from about 5 to about 15 phr) plus stearic acid (e. g. from about 1 to about 5 phr). The rest of the curing system is ordinarily kept apart from the elastomer until just prior to curing.

Reinforcing fillers may be selected from the group comprising, but not limited to, carbon black, clays, minerals such as talc and silica. Fillers tend to increase the tensile strength of the final composition. Fillers may be added up to levels of 30phr.

Loadings beyond this level tend to impair the flow of the composite. Polypropylene homopolymer may also be added to balance mould shrinkage caused by the addition of fillers.

Heat stabilising additives may be selected from the group comprising, but not limited to, phenolic resins (e. g those available from Hylam Bakelite); Flectol H; chlorinated rubbers.

Suitable antioxidants may be selected from one or more of the group including, but not limited to, Wingstay L/100 (Goodyear); di-naphthyl-p-phenylene diamine (Santowhite

CI, Monsanto); styrenated phenol (Montaclere-SE, Monsanto); 2,5-di (tert-amyl) hydroquinone (Santovar-A, Monsanto); 4,4'-butylidenebis- (6-tert-butyl-m-cresol) (Santowhite, Monsanto); tributyl thiourea (Santowhite-TBTU, Monsanto); 6-tert-butyl- m-cresol/sulfur dichloride (Santowhite-MK, Monsanto); trinonyl phenylene phosphate (TNNP; Ciba Geigy). Preferably antioxidants are added at 1 to 2 % of the total composition.

Antidegradants that may be added could include ethylene propylene diene terpolymer (EPDM) rubbers. These can be added at 5% of the total composition to improve the weatherability of the composition. Levels over 5% may have an adverse impact on curing because EPDM are slow curing rubbers.

Peptising agents may be selected from any of those known in the art, such as Renacit 11 (Bayer). These agents are preferably added at about 0.07 % of the total composition.

In a second aspect the invention might also be said to reside in a natural rubber thermoplastics composite of a rubber matrix of the first aspect of the invention blended with any one or more of the thermoplastics selected from the group comprising polyolefins, polyurethanes, polyesters, polyamides, acrylates, acrylonitrile butadiene styrene (ABS).

Thus in one broad form of a second aspect the invention could be said to reside in a natural rubber thermoplastics composite including a) natural rubber 10-90% (v/v) b) one or more first compatabilisers selected from a group of polymers containing either i) a nitrile group, ii) a halogen, iii) an acetate group, iv) an epoxide, v) a styrene, or vi) an acrylate

c) one or more second compatabilisers which are interfacial copromoters selected from a group comprising either i) polyvinyl acetate, ii) ethylene vinyl acetate, iii) polyacrylonitrile or high nitrile resin, iv) acrylamide or polyacrylamide, v) a phenolic resin, vi) an acrylate polymer, vii) a halogenated polymer, viii) maleic anhydride or polymaleic anhydride, or ix) a bismaleimide d) one or more thermoplastics selected from a group comprising either i) polyurethanes, ii) polyesters, iii) polyamides, iv) acrylates, v) acrylonitrile butadiene styrene, vi) polyolefins, or vii) cellulose esters.

Most preferably the thermoplastic is more polar than natural rubber, such thermoplastics including polyurethanes, polyesters, polyamides, acrylates, acrylonitrile butadiene styrene or celluloses. It will be appreciated that some slow curing rubbers such as butyl rubber may not be particularly suitable in the practice of this invention because of their undesirable curing properties. Further, when the thermoplastic is selected from the group of polyolefins and the first compatabiliser is selected from the group of halogenated polymers, then preferably the second compatabiliser is not a phenolic resin or a halogenated polymer.

Optionally, a least part of the thermoplastic used in the composite may be derived from recycled thermoplastics.

Suitable polyolefins may be selected from the group including but not limited to high density polyethylene (HDPE), linear low density polyethylene (LLDPE), polypropylene homo polymer (PPHP), polyproylene copolymer (PPCP), poly (ethylene-co-propylene)

(PEP). Polyolefins may be chosen for their high chemical resistance, electrical properties, high impact strength and low cost.

Suitable thermoplastic polyamides include those that are crystalline or resinous high molecular weight copolymers or terpolymers. Polyamides may be prepared by polymerisation of one or more lactams such as caprolactam, pyrrolidinone, lauryllactam, or by condensation of diamines with diacids. Suitable polyamides include polymeric amides having recurring amide groups as part of the polymer backbone and may be chosen form the list including but not limited to polycaprolactam (Nylon-6), polylauryllactam (Nylon-12), polyhexamethyleneadipamide (Nylon-6,6), polyhexamethyleneazelamide (Nylon-6,9), polyhexamethylenesebacamide (Nylon- 6,10), polyhexamethyleneisophthalamide (Nylon-6, IP), the condensation product of 11-aminoundecanoic acid (Nylon-11) and the product of reaction between castor oil and sebasic acid. Suitable polyamides also include copolymers with other monomers.

Polyamides may be chosen for their high impact strength, shock resistance, high tensile strength, ability to absorb moisture and/or their flame resistance.

Suitable polyurethanes may include but are not limited to thermoplastic polyurethane resins based on caprolactam, ethylene glycol or ethyl or propyl adipate reacted with isocyanates and having a Shore A hardness of 80 to 90. Polyurethanes may be chosen for their desirable properties that may include their toughness and abrasion resistance.

Many commercially available thermoplastic polyesters may be suitable and the polyesters may be prepared by condensation of one or more dicarboxylic acids, anhydrides or esters and one or more diol. Cellulosic polyesters are particularly suitable for the present invention and suitable cellulosics can include but are not limited to polymers of cellulose acetate, cellulose acetobutyrate or cellulose propionate.

Suitable polyesters may also include polycarbonates.

Suitable acrylic thermoplastics may include polymethyl methacrylate and these may be added to improve heat stability and coulourability of a final composition. Further, acrylics tend to be highly crystalline and therefore they are preferable when a highly crystalline final composition is required.

The rubber thermoplastic compositions of the present invention may be divided into one of four classes depending upon the properties of the composition, namely rigid, toughened, semi-toughened or soft natural rubber thermoplastic compositions.

The rubber thermoplastic compositions of the present invention are intended for use as thermoplastic elastomers that are processable and can be fabricated into parts by conventional techniques used for thermoplastic materials. The mechanical properties of the compositions of the present invention may be determined using the standard test procedures used in the rubber and thermoplastics industries.

Thermoplastic rubber compositions of the present invention may be used for making articles used in the mechanical, automotive, construction, textile, sports goods, irrigation, cable, agriculture, footwear, pipe/hose and tyre and wheel industries. The articles may be made by extrusion, injection moulding or compression moulding.

In a third aspect the invention might also be said to reside in an article made from a thermoplastic composite of the present invention, which article may be formed by any suitable method used in the thermoplastics industries, which methods may include extrusion, injection moulding or compression moulding.

In a fourth aspect the invention might also be said to reside in a method of forming a natural rubber thermoplastics composite, including the steps of forming a rubber matrix of the first aspect of the invention, and combining the rubber matrix with a plastics phase under conditions of dynamic vulcanisation.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding, the invention will now be described with reference to a number of examples which are also represented in the Figures wherein, Figure 1 shows weight loss versus temperature results of differential scanning calorimetry of a sample'soft'grade sample of natural rubber/nitrile rubber/polyolefin, Figure 2 shows heat flow versus temperature results of differential scanning calorimetry of a sample'soft'grade sample of natural rubber/nitrile rubber/polyolefin,

Figure 3 shows loss modulus versus temperature results of dynamic mechanical analysis of a sample'soft'grade sample of natural rubber/nitrile rubber/polyolefin, Figure 4 shows weight loss versus temperature results of differential scanning calorimetry of a sample'intermediate'grade sample of natural rubber/nitrile rubber/polyolefin, Figure 5 shows heat flow versus temperature results of differential scanning calorimetry of a sample'intermediate'grade sample of natural rubber/nitrile rubber/polyolefin, Figure 6 shows loss modulus versus temperature results of dynamic mechanical analysis of a sample'intermediate'grade sample of natural rubber/nitrile rubber/polyolefin, Figure 7 shows weight loss versus temperature results of differential scanning calorimetry of a sample'rigid'grade sample of natural rubber/nitrile rubber/polyolefin, Figure 8 shows heat flow versus temperature results of differential scanning calorimetry of a sample'rigid'grade sample of natural rubber/nitrile rubber/polyolefin, and Figure 9 shows loss modulus versus temperature results of dynamic mechanical analysis of a sample'rigid'grade sample of natural rubber/nitrile rubber/polyolefin.

DETAILED DESCRIPTION OF THE INVENTION Described below are a number of compositions made in accordance with this invention.

It will be understood that these are exemplary and that the invention is not to be limited to any one of them or to the examples collectively.

EXAMPLE I-General Procedureforformation of composites The following is a general procedure for the formation of composites of the present invention. Quantities of individual components are given in the specific examples outlined below.

Procedure: The natural rubber is pre-masticated in an internal mixer or a mill together with the first and second compatabilisers and peptisers (if required) for about 5 minutes or less, although if a mill is used the process may take more than 10 minutes. The time is dependent upon the viscosity of the rubber. The temperature during mixing or milling preferably should not exceed 120°C. Any additives such as fillers are added during the mastication. After mixing, the stock is normally viscosity stabilised, slabbed and left to mature with polyethylene sheets between each patch. The maturation period may be 6-12 hours. The rubber matrix is then cut into strips and added to a Branbury mixer or mixer extruder (e. g. twin screw with dosing system) at between 130°C and 205°C depending on the melt temperature of the thermoplastic. The thermoplastics are then added and in teh case of a Branbury mixer after mixing for 5 minutes an antioxidant is added and after a further 1 minute the resulting composite is fed onto an extruder in a hot condition and extruded and pelletised. The product is then extruded and pelletised on a strand pelletiser or a die face cutter.

EXAMPLE 2.1-Rubber thermoplastic compositions with nitrile first contpatabiliser and thermoplastics The composites in Table 1 were made according to the procedure of Example 1.

Table 1 /PA-6NRNIR PVA ZincHVA2DCPAntiTin NBR resin Chloride Stearate oxidant 5 25 70 5 5 0. 5 1 0. 75 0. 05 I 10 30 60 5 5 0. 5 1 0. 75 0. 06 1 20 30 50 5 5 0.5 1 0. 750.07 1 -30 30 140 5 5 0. 5 1 0.75 0. 08 1 30550.510.750.0914030

NR Natural Rubber: SMRCV/ISNRCV or equivalent with low dirt content NIR/NBR Acrylonitrile isoprene rubber with a nitrile content of 40% or acrylonitrile butadiene rubber with a nitrile content of 40% or a 50: 50 ratio of them.

PA-6 Polycaprolactam (Nylon-6): mfi 3, shore hardness 80A.

PVA Polyvinyl acetate Phenolic resin Phenolic formaldehyde resin for heat stability/hardness (Hylak; Bakelite) Tin chloride Stannous (II) chloride: a selection from commercial grades available Zinc stearate Commercial grade HVA2 Bismalemide (DuPont) DCP Dicumyl peroxide (Akzo Perkadox 14 S) v Antioxidant: Wingstay 100 (Goodyear) Dehydrated castor oil (DCO) may also be added if a plasticiser is required.

EXAMPLE 2.2 thermoplasticcompositionswithnitrilefirstcompatabiliserRubbe r and polyolefin thermoplastics The composites in Tables 2 and 3 were made as described below.

Table 2 Soft grades Shore NR NBR LLDPE EVA Engage HVA, Peroxide MBTS Zinc Anti Hardness stearate Oxidants 65A 15 30 10 35 10 0.75 0. 07 0. 25 I 1 60A 15 30 10 30 15 0 75 0. 07 0 25 l 30525200.750.0750.251155A15 50A 15 30 5 20 25 0 75 0. 075 0 25 45A 15 30 5 10 30 0. 75 0.08 0.25 1 1 40A 15 30 5 5 35 0. 75 0. 08 0. 25 1 1 Table 3 Intermediate grades Shore NR NIR/HDPE EVA LLDPE HVA, Peroxide MBTS Zinc Anti Hardness NBR Stearate oxidants 90A 15 25 40 20 0. 75 0. 06 0.25 l 85A 15 25 30 25 5 0. 75 0. 06 0 25 l _ 80A 20 30 20 20 10 1 1 75A 20 30 10 20 20 0.75 0. 07 0. 25 70A 5 10 3510300.750.080.251165A25

NR Natural Rubber: SMRCV/ISNRCV or equivalent with low dirt content NIR/NBR Acrylonitrile isoprene rubber with a nitrile content of 40% or acrylonitrile butadiene rubber with a nitrile content of 40% or a 50: 50 ratio of them.

HDPE High Density polyethylene: melt flow index (mfi) 3; moulding grade.

EVA Ethylene vinyl acetate: preferred grade 28% vinyl acetate content; mfi 2 LLDPE Linear low density polyethylene: moulding grade; mfi 3 (Exxon) Engage Ethylene propylene plastic HVA2 Bismalemide (DuPont) Peroxide Isopropyl benzene peroxide (EIFATO Therm/AKZO Nobel) Antioxidant: Wingstay 100 (Goodyear) Process: NR, NIR and/or NBR, HDPE and EVA were masticated in a Barbender mixer at 80 rpm and 100°C. The masticated rubber matrix along with LLDPE, HVA2, peroxide and zinc stearate are blended in an internal mixer (Branbury) at 180-190°C. Antioxidant is added at the end of the blending process. The material is extruded and pelletised as in Example 1.

EXAMPLE 2.3-Rubber thermoplastic compositions with nitrile first compatabiliser and polyolefin thermoplastics and a bismaleimide compatabiliser The composites in Table 4 were made as described below.

Table 4 Shore Natural NIR PPHP PPCP HMH-LDPE HVA, Peroxide Zinc Anti hardness rubber NBR DPE Stearate oxidant 24040150.751160D3 22550100.751155D3 50D 6 4 30 30 30 0. 75 0. 03 l i 45D 9 6 30 30 25 0.75 0. 04 1 1 40D 12 8 30 30 20 0.75 0.05 1 1 35D 15 10 30 30 15 0 75 0.06 1 1 30D I H 12 30 20 20 0. 75 0. 07 1620202025D24 110.08 202015150.750.081120D30 NR Natural Rubber: SMRLCV or ISNRLCV or equivalent; low protein and low dirt grades are preferable.

NIR/NBR Acrylonitrile isoprene rubber with a nitrile content of 40% or acrylonitrile butadiene rubber with a nitrile content of 40% or a 50: 50 ratio of them.

PPHP Polypropylene homopolymer: mfi 3; general purpose (Shell) PPCP Polypropylene co-polymer: mfi 3; general purpose (Shell) HMHDPE High molecular weight high density polyethylene: mfi 2 (Exxon) LDPE Low density polyethylene: general purpose; mfi 2 (Exxon) HVA2 Bismalemaleimide (Dupont) Peroxide Isopropyl benzene peroxide (Elf Atochem/AKZO Nobel)-should be added to run while masticating Zinc stearate a selection from commercial grades available Anti-oxidant Wingstay L/100 (Goodyear) or Santowhite (Monsanto) 2% Titanium dioxide, carbon black or Tunivan (P) [Ciba Geigy (Novartis) can be added for additional UV protection.

PPHP-can be substituted by PPCP, PPHP to balance mould shrinkage.

Vanillin (1-2 phr) of can be added to the compound for odour.

Fillers like CaC03/talc can be loaded up to 30%.

Process: Rubbers are masticated with 10 parts of paraffinic oils, 0.08 parts of Renacit-11 (Bayer) and/or 0.04 parts of DCO (Dehydrated Castor oil). The masticated rubber along with polyolefins, HVA2, peroxide and zinc stearate are blended in an internal mixer at 180-190°C. Antioxidant is added at the end of the blending process. The same material is extruded and pelletised according to Example 1. It is desired that the material is allowed to expand to the maximum to avoid future mould shrinkage. EXAMPLE 3.1-Compositions and properties of rubber thermoplastic polyamide composites with nitrile based first compatabiliser Component Amount Amount Sourcelgrade (kg) (kg) Natural rubber 20 30 SMR-LCV Malaysia Nitrile butadiene 20 30 JSR-N ACN content 50%; Japan rubber Polyamide-6 60 40 Polycaprolactam SRF MFI 3 Polyvinyl acetate Commercial5 Dimethylol phenol SP1045:SchenectadyChemicals1 Tin chloride Commercial1 Zinc stearate 2 2 Commercial Bismaleimide HVA2:DuPont(USA)1 Peroxide 0. 4 0. 6 t-Butylisopropyl benzene; (Perkadox 14-40A, Akzo Nobel) Dehydrated castor oil Generic Antioxidant 2 2 Wingstay-I 00 (Goodyear) Properties Units Test Metlzod Shore Hardness 70 D 50 D ASTM D 2240 Density 1. 14 1.12 gm/cc ASTM D 792 Tensile Strength 780 670 kg/cm2 ASTM D 638 Elongation at Break 350 380 % ASTM D 638 Flexural Modulus 2400 2000 kg/cm2 ASTM D 638 Brittle -40°CASTMD746-40 Impact Strength 34 NB kg. cm/cm2 ASTM D 256 Heat Deflection Temp > 160 > 160 ASTM D 648 (4.6 kg/cm2) EXAMPLE 3.2-Compositions and properties of rubber thermoplastic polyester composites with nitrile based first compatabiliser Component Amount Amount Sourcelgrade (kg) (kg) Natural rubber 20 20 SMR-LCV Malaysia Nitrile butadiene 20 20 JSR-N ACN content 50%; Japan rubber Ethylene acrylate-20 VAMAC (DuPont) rubber Polyester (Cellulose) 60 40 Eastacel (Eastmann Chemical Products.USA) Polyvinyl acetate 5 5 Generic Dimethylol phenol SP1045(SchenectadyChemicals)1 33Hylak(HylanBakelite)Phenolformaldehyde Tin chloride Commercial1 Zinc stearate 2 Commercial Bismaleimide 1 1 HVA2: DuPont (USA) Zinc oxide 0.6 0. 5 Generic Dehydrated castor oil 0.8 1. 0 Generic Antioxidant 1 1 Winestay-100 (Good ear) TestMethodPropertiesUnits Shore Hardness 60 D 40 D ASTM D 2240 Density 1.20 1. 18 gm/cc ASTM D 792 Tensile Strength 480 420 kg/cm2 ASTM D 638 Elongation at Break 250 270 % ASTM D 638 Flexural Modulus--k/cm2 ASTM D 638 Brittle Point-30-30 °C ASTM D 746 Impact Strength kg. cm/cm ASTM D 256 Heat Deflection Temp > 180 >180 °C ASTM D 648 (4.6 kg/cm2) EXAMPLE 3.3- propertiesofrubberthermoplasticpolyurethaneand composites with nitrile basedfirst compatabiliser Component Amount Amount Sourcelgrade (kg) (kg) Natural rubber 20 20 SMR-LCV Malaysia Nitrile butadiene rubber 20 20 JSR-N ACN content 50%: Japan Polychloroprene-20 Neoprene (DuPont) Thermpolastic 60 40 Despiopan (Bayer); Hardness 30 polyurethane Shore D 5-GenericPolyvinylacetate Polyvinvl chloride-5 Occidental : paste grade compound Phenol formaldehyde 3 3 Hylak (Hylan Bakelite) 11SP1045(SchenectadyChemicals)Dimethylolphenol Tin chloride i Commercial Zinc -2 Commercial Bismaleimide I I HVA2 ; DuPont (USA) Zinc 5Commercial- -Dicumylperoxide(AkzoNobel)Peroxide0.4 Dehydrated castor oil Generic1.0 AntioxidantAntioxidant2 2 (Goodyear) Properties Units Test Method Shore Hardness 90 A 80 A ASTM D 2240 Density 1.20 1. 18* gm/cc ASTM D 792 (1.28) Tensile Strength 520 460 kg/cm2 ASTM D 638 Elongation at Break 400 480 % ASTM D 638 Flexural -kg/cm2ASTMD638- Brittle -50-50 °C 746D Im act Strength NB NB kg. cm/cm2 ASTM D 256 Heat Deflection Temp NA NA °C ASTM D 648 (4.6 kg/cm2)

NB-No break; NA-Not applicable * density given is measured by displacement, and value in brackets are empirical values EXAMPLE 3.4 andpropertiesofrubberthermoplasticpolyolefinCompositions compositeswith nitrile basedfirst compatabiliser AmountAmountAmountAmountAmountSource/gradeComponentAmount (kg) (kg) (kg) (kg) (kg) (kg) Natural rubber 3 9 18 25 30 15 SMR-LCV Malavsia Nitrite-2 6 20 20 15 JSR-N ACN content butadiene 50%: Japan rubber ---1515Chlorinated- polyethylene JSR; Low 23 --- viscocity lowEPDM1 ethylene content Magnesium----5 5 Commercial oxide Epoxidised 1 2 3 5 - - Epoxide level 50%; natural rubber Guthrie (Malaysia) -----Shell;mfi3Polypropylene40 homopolymer Polypropylene 40 30 Shell ; mfi 4 copolymer -2520---Lowdensity polyethylene Linear low--20 10 5 Exxon density polyethylene Engage 10 25 DuPont Zinc stearate 2 2 2 3 3 3 Commercial Bismaleimide 0.75 0.75 0.75 0.75 0.75 0.75 HVA2; DuPont (USA) Peroxide - 0. 04 0.07 0.08 0.08 0.8 PERKADOX 14- 40A (Akzo Nobel) Chlorinated 2 4 7 7 5 Commercial paraffin oil Antioxidant 2 2 3 3 3 3 Wingstay-100 (Goodyear) Properties Units Test Method Shore Hardness 60 D 45 D 90 A 75 A 65 A 50 A-ASTM D 2240 Density 0.91 0.92 0.93 0.97 0.97 0.98 gm/cc ASTM D 792 Ultimate 24 16 12 9 7.9 4.8 MPa ASTM tensile strength D 638 Ultimate 550 450 374 480 460 358 % ASTM elongation D 638 Tear 76.144.728.332.6725.5N/mm102.6 100% Modulus 14.1 11.9 6.5 3.1 3.4 1.9 MPa ASTM D 638 Brittle Point-52.5-57.5-57.5-57.5-60-60 °C ASTM D 746 Abrasion 115 95 60 84 47 60 mg/Tabor resistance 1000 test rev Impact 30 35 NA NA NA NA kg. cm/ ASTM Stren th cm2 D 256 Heat 130 130 120 NA NA NA °C ASTM Deflection D 648 Temp (4.6 kg/cm2) EXAMPLE 4-Compositions and properties of rubber thermoplastic composites with nitrile and acrblate based, first compatabilisers Component Amount Amount Amount Amount Source%grade (kg) (kg) (kg) (kg) Natural rubber 25 25 25 25 SMR-LCV Malaysia Nitrile butadiene 15 15 15-JSR-N ACN content rubber50% : Japan Ethylene acrylate 10 10 10 10 Vamac ; DuPont rubber --15Neoprene;DuPontPolychloroprene- Polyvinyl acetate 5 5 5-Generic 45--PA-6;mfi3Polyamide- Thermoplastic--45 45 Bayer: Hardness urethane 80A Polymethyl 45---PMMA : Moulding methacrylategrade Polyvinyl --5- Compound paste grade : Occidental Dehydrated castor 2 2 2 - Generic oil Chlorinated paraffin---3 Commercial oil Zinc stearate 2 2 2 2 Commercial Thiurad (Monsanto) TMTD 0.10.10.1 Commercial Magnesium oxide 4 4 4 4 SP1045; Phenolic resin 10.5Schenectady1 Acrylamide 0.5 0.5 0.5-Commercial Wingstay-100 Antioxidant 2 2 2 2 (Goodyear) Properties Units Shore Hardness 90 A 80 A 60 A 60 A Density 1.01 1.02 1.04 1.24* gm/cc Tensile strength 410 430 380 380 kg/cm2 Elongation at break 300 380 420 420 % Tension set 33 31 29 28 % * empirical values EXAMPLE 5-Compositions and properties of rubber thermoplastic composites with firstcompatabiliserschlorinebased Component Amount Amount Amount Amount Sourcelgrade (kg) (kg) (kg) Natural rubber 25 25 25 25 SMR-LCV Malaysia Polychioroprene 25 25 15 15 Neoprene: DuPont Chlorinated--10-Bayer CM polyethylene --10Hypalon;DuPontChlorosulphonated- polyethylene Ethylene vinyl - - 5 5 Mitsui DuPont acetate Polyvinyl chloride 5 35--Compound : 70 Shore A hardness Thermpolastic 45 -Bayer;80ShoreA- urethane Low density--45 45 mfi 5 moulding polyethylene grade Phenolic resin 22SP1045;2 Schenectady Zinc stearate 3 3 3 3 Commerical Bismaleimide 0.3 0.3 0.3 0.3 HVA2: DuPont Masnesium oxide 5 5 5 5 Commercial Chlorinated 3 3 3 3 Commercial paraffinoil Antioxidant 22Wingstay-1002 (Goodyear) Properties Units Shore Hardness 60 A 55 A 80 A 80 A Density 1. 20* 1.20* 1.8* 1.8* gm/cc Tension set 28 32 33 32 % Elongation at 430 410 380 360 % break * empirical values EXAMPLE 6-Compositions and properties of rubber thermoplastic composites with epoxide basedfirst compatabilisers Component Amount Amount Amount Source/grade (kg) (kg) (kg) Natural rubber 25 25 50 SMR-LCV Malavsia Epoxidised natural 25 30 - ENR at 50% epoxy rubber levels EVA 10 10 10 Mitsui DuPont Polypropylene 40 40 40 Shell KMT 6100; 4copolymermfi 11HVA2;DuPontBismaleimide1 Peroxide 0.06 0.06 0.06 Perkadox 14S (Akzo Nobel) Naphthalic oil 3 3 3 Commercial Antioxidant 1Wingstay-1001 (Goodvear) Properties Units Shore Hardness 80 A 85 A 80 A Density 0.93 0.93 0.93 gm/cc Tensile strength 490 510 490 kg/cm2 Tension set 30 30 27 % Elongation at 380 400 400 % break

EXAMPLE 7-Properties of rubber thermoplastic composition with nitrilefirst compatabiliser and polyolefin thermoplastics A'soft'grade composition comprising: natural rubber (15 parts), nitrile butadiene rubber (30 parts), linear low density polyethylene (5 parts), ethylvinyl acetate (25 parts), engage (20 parts), HVA2 (0.75 parts), peroxide (0.075 parts), MBTS (0.25 parts), zinc stearate (1 part) and antioxidant (1 part) was subjected to thermogravimetric analysis, differential scanning calorimetry and dynamical mechanical analysis as described.

METHODS Thermogravimetric analysis (TGA) T. A. Instruments TGA 2950 connected to a Thermal Analyst 2200 Controller was used to perform experiments and record the results. Prior to and during each thermogravimetric analysis, the system was purged with high purity nitrogen at a rate of 50 ml/min. Once the sample was loaded, the sample was heated with heating ramp of 5°C/min up to 600°C. Weight was recorded versus temperature on a continuous basis for analysis.

Ditferential scanning calorimetry (DSC) DSC was conducted using DSC 2920 from TA Instruments. A weighed amount of sample was analysed from-100°C to 400°C under nitrogen flow, and heating rate of 10°C/min.

Dynamicmechanical analyser (DMA) DMA was carried out using DMA 2980 (TA Instruments) operating in tension mode from-140°C to 100°C at 1 Hz frequency and 0.08% strain amplitude, at programmed heating rate of 2°C/min. Liquid nitrogen was used to achieve sub-ambient conditions.

Glass transition temperature (Tg) of the samples was determined from tana curves.

RESULTS TGA: Figure 1 shows weight loss versus temperature of the sample. The results show the approximate composition of 53% rubber (PU added), 25% plastic, 13% plasticiser and 9% other material.

DSC: Figure 2 shows two melting points and two broad endothermic decompsoitions.

The first metling point is broad at temperature 118°C with heat of fusion of 3.66J/g.

The second melting point is at 157°C with heat of fusion of 6.47 J/g.

DMA: The glass transition temperature was selected as the peak position of the tana when plotted vs temperature. From Figure 3 two sharp glass transitions can be noticed, the first at-60°C and the second glass transiton at-21°C. The graph indicates a storage modulus of 18.59 MPa at 25°C.

EXAMPLE 8-Properties of rubber thermoplastic composition with nitrile first compatabiliser and polyolefin thermoplastics An'intermediate'grade composition comprising: natural rubber (20 parts), nitrile butadiene rubber (30 parts), high density polyethylene (10 parts), ethylvinyl acetate (20 parts), linear low density polyethylene (20 parts), HVA2 (0.75 parts), peroxide (0.07 parts), MBTS (0.25 parts), zinc stearate (1 part) and antioxidant (1 part) was subjected to thermogravimetric analysis, differential scanning calorimetry and dynamic mechanical analysis using the methods as described in Example 7.

RESULTS TGA: Figure 4 shows weight loss versus temperature of the sample. The results show a first step of natural rubber weight loss that is not a sharp peak and the total amount is

26% mixture of natural rubber and other rubber. A second step is the decompositions of plastics in the amount of 71% and a residue of 3%.

DSC: Figure 5 shows two melting points and two broad endothermic decompsoitions.

The first metling point is at temperature 125°C with heat of fusion of 15.10J/g. The second melting point is at 162°C with heat of fusion of 36.32 J/g.

DMA: The glass transition temperature was selected as the peak position of the tana when plotted vs temperature. From Figure 6 two sharp glass transitions can be noticed, the first a sharp peak at-58°C, which represents that glass transition of the natural rubber and nitrile rubber indicating their compatability. A second broad glass transiton at 0.8°C is indicative of partially miscible polyolefins. The graph indicates a storage modulus of 298.85 MPa at 25°C.

EXAMPLE 9-Properties of rubber thermoplastic composition with nitrile first compatabiliser and polyolefin thermoplastics A'rigid'grade composition comprising: natural rubber (6 parts), nitrile butadiene rubber (4 parts), polypropylene homopolymer (30 parts), polypropylene copolymer (30 parts), high molecular weight high density polyethylene (30 parts) HVA2 (0.75 parts), peroxide (0.03 parts), zinc stearate (1 part) and antioxidant (1 part) was subjected to thermogravimetric analysis, differential scanning calorimetry and dynamic mechanical analysis using the methods as described in Example 7.

RESULTS TGA: Figure 7 shows weight loss versus temperature of the sample. The results show a first step of natural rubber weight loss and the amount is 9%. A second step is the decompositions of polypropylene and polyethylene in the amount of 90% and a residue ouf 1%.

DSC: Figure 8 shows two melting points and a broad endothermic decomposition with several shoulders. The first metling point is at tempaerature 126°C with heat of fusion of 18.61J/g. The second metlting point is at 165°C with heat of fusion of 40.93 J/g.

DMA: The glass transition temperature was selected as the peak position of the tana when plotted vs temperature. From Figure 9 two broad glass transitions can be noticed, the first at-52°C, and the second broad glass transiton at 9.7°C in indicative of partially miscible polyolefins. The graph indicates a storage modulus of 630 MPa at 25°C.