WO2018084694A1

WO2018084694A1 - Polyisoprene latex graphene composites and methods of making them

Info

Publication number: WO2018084694A1
Application number: PCT/MY2017/000039
Authority: WO
Inventors: Fook Peng LENG; Lai Peng LIM; Leng Kian GOH; Yi Yee LOH; Joon Ching JUAN; Nay Ming HUANG
Original assignee: Karex Holdings Sdn Bhd.
Priority date: 2016-11-03
Filing date: 2017-10-31
Publication date: 2018-05-11
Also published as: EP3535317A1; US11214664B2; CN109923159B; US11827765B2; EP3535317B1; US20190270863A1; CN109923159A; US20220089834A1; WO2018084694A8; US20240043653A1; EP3535317A4; MY194301A

Abstract

The present Invention' relates to a method of preparing reduced grapheme oxide, Incorporation of the adduced graphene oxide into polysioprene latex to provide a polyisoprene latex graphene composite and elastomerk articles prepared using the polyisoprene latex- graphene composite. In particular, the reduction of -graphene oxide is accomplished without the use of strong reducing agents and organic solvents and incorporation of die reduced graphene oxide into polyisoprene latex Is accomplished using room temperature latex mixing method or hot maturation. The resultant composite exhibits good colloid stability and. polyisoprene latex films produced from the composite exhibit good mechanical properties with improved ageing resistance.

Description

FOLYISOFRENE LATEX 6RAFBI E COMFOSiTES ANB METHODS OF

M AKING THEM

Field of the Invention

[0001 ] The presen invention relates to a method of preparing reduced graphene oxide, incorporation of the reduced graphene oxide into polysioprene latex to provide a polyisoprene late graphene composite and elastonieric articles prepared using the poiyisoprene latex graphene composite. In- particular, the reduction of graphene oxid is accomplished without the use of strong reducing argents and organic solvents and incorporation of the reduced graphene oxide into polyisoprene latex is accomplished using room temperature latex mixing method or hot maturation. The resultant composite exhibits good colloid stability and polyisopre-ne latex films produced from die composite exhibit good mechanical properties with im roved ageing resistance.

Backg ound of the invention

[00021 Graphene and its derivatives such as graphene mde, have attracted tremendou attention and research interest since the discovery of graphene in 2004 due to their exceptional thermal, mechanical and barrier properties [Johnson et «„ Current Opinion in Colloid & Interface Science, 2015, 20, 367-382], Polymer nanocomposiies (polymer matrix composites with -incorporated .nanoscale filler materials) are one of the most studied applications for graphene oxide. This could be attributed to the variety of chemical functional groups available and their relatively low cost as compared to pristine graphene. Graphene-polymer nanocomposites show significant mechanical property enhancements at much lower loadings than -conventional fillers composite. [fCashyap et .,. J, Alloys and Compounds, 2016, ό84_> 254-260, doi;

10.1016/|,i lkom.2016,05.16¾

[0003] General approaches or strategies employed to prepare conventional graphene- polymer nanocomposites involve solution mixing, melt blending and in-siiu

polymerisation methods. Performance of graphene-polymer nanocomposites is dependent on the dispersion of graphene in the polymer matrix.

[0004] Hence modification of graphene oxide has been widely studied to ensure uniform distribution of graphene oxide in the polyme matrix and at- the sane time improve the interfaeia! adhesion between graphene oxide and polymer. [0005] The two eon nen Bi thods sed to roduce reduce graphene oxide are chemical reduction and thermal reduction. Chemical reduction of graphene oxide is normally achieved through, addition of ^; reducing agents, such as hydrazine hydrate, sodium bcsfohydride, hydroi.|uinone_? citric acid and aseorbie acid, etc, Chemical 5 reduction of graphene oxide Usually results in a black precipitation iroru the original yellow-brown suspension,

[0006] Despite various approaches that have been explored, the process to make a homogenous and stable dispersion of graphene xide in the po!yisoprette latex matrix remains a major challenge in this field.

].o [0007] The present inventors have found a method of producing reduced graphene oxide without the use of a strong reducing agent, The inventors have also found a method of achieving homogeneity of the composite dispersion without the use of high shear mixing or ultrasonic mixing. Colloidal stability of ^'the latex was also improved wit current invention, ¾thermore_» eiastomerie film produced from the composite

1 s exhibits good physical properties and improved resistance to ageing.

Summary of the Invention

[0008] In a first aspect, the present invention provides a polyisoprene latex graphene composite composition comprising:

20 i polyisoprene latex

it) at least one stabilizer;

i,u)at least one curing agent; and

tv) graphene oxide.

[0009] in some embodiments, more than one curing agent is present. In some

25 embodiments, the graphene oxide is reduced, graphene oxide .

[00010] In another aspect of the invention there is provided a method of preparing reduced graphene oxide comprising:

a) adjusting the pH.of a graphene oxide composition to between about .8 and 12 b) adding to the pH adjusted graphene oxide composition one or more curing c) mixing the graphene oxide composition b slow agitation at a t mperature in the range of from about 20 *€ to about SO °C for a time period in the range of about 4 to about 24 bouts.

[00011 ] in some embodiments, more than one curing agent is added to the pH

5 adjusted graphene oxide composition. I some embodiments, one or more stabilizers are added at step a).

[00012 J In a further aspect of the invention, there is provided a method o preparing a poiyisoprene latex graphene composite composition comprising*

a) preparing a composition of reduced graphene oxide by

i o i) adjusting the pH of a graphene oxide composition to in the range of about 8 and 12;

ii) adding to the pH adjusted graphene oxide composition at least one

curing: agent

in) mixing the graphene oxide composition by slo w agitation at a

15 temperature in the range of from about 20 *C to about 80 °C for a period in the range of about 4 to about 24 hours;

b) preparing a stabilized poiyisoprene latex composition by mixin poiyisoprene latex with at least one stabili er under slow agitation for a time period in the range of about 4 to about 24 hours; and

£0 e) combi ning, the reduced graphene oxide composition of step a) with the

stabilized poiyisoprene latex composition prepared in ste b) and mixing.

[00013] In some embodiments, the mixing at step c) is carried out at room

temperature, in other embodiments, the mixin at step c) is carried out by slo agitation at a temperature in the range of 4 *€ to about 70 ⁰<X

25· [00014] in yet another aspect of the present invention, there is provided a method of making an elastomeric article comprising;

a) preparitig poiyisoprene late graphene composite composition of the

present invention;

b) dipping a former into the poiyisoprene iatex graphene composite composition s Q to form an eiastomeric film on the former; and

c) curing the elastomeric film. [000 I 5] In yet a further aspect of the invention, the present in vention pro vides an el&stomeric article .made by the method of the invention.

[00016] in some embodiments, the elastomerie articl is a condom, glove, probe cover, finger cot, catheter, tubing o a balloon for a catheter. la a particular

s embodiment, the e!astom tic article is a condom.

Brief Description of the Figures

[000 i 7] Figure 1 provides photographic representations (A) an unfilled, vulcanised (cored) polyisoprene latex film (without, grapheme oxide) and <B) a latex film of the present invention comprising reduced graphene oxide and prepared using the room i o temperature latex mixing method .

Detailed Description of the Invention

[00018] ef ii

[00019] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as com.mo.niy understood hj those of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used m the practice or testing of the present invention, preferred methods and materials are described,

[00020] The articles "a" and "an" are used herein to refer to one or to more than one (i.e. to at least one) of the grammatical object of the article. By way of example, " element" means one element or more than one lement

[00021 J As used herein, the term "'about^'5 refers to a quantity, level, value, dimension, size or amount that varies by as much as 30%, 25%, .20%, 15% or 10% to a reference quantity, level, value,, dimension, stee or antpuni

[00022] Except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the in vention,

[00023] The term "consisting, essentially of^* or variations such as "consists essentially of^' to require the listed components to be present and exclude other components from being present with the exception of that inactive compounds, such as impurities, may be present. [00024] CompasUfans eftke Invention

[00025] In a first: aspect, the present Invention provides a poiyisoprene latex grapiieiie composite composition comprising:

0 poiyisoprene latex

It) at least one stabilizer;

Si) at least one curing agent; and

iv) Graphene oxide.

[00026] In some embodiments, the poiyisoprene latex is natural poiyisoprene latex (rubber), in other embodiments, the poiyisoprene latex is ^'synthetic poiyisoprene latex. Synthetic poiyisoprene latex is a synthetic predominantly stereoregular polymer- that resembles, natural rubber in molecular structure and properties. Polymerisation of isoprene may result in four possible types of repeating units, 1 _f2 "poiyisoprene, 3» « poiylsoprene, imns~l ,4-poi isoprene and cis- 1 ,4-polyisoprene. in some emhodmwnis., the synthetic poiyisoprene latex used has a high proportion of £·,¾ !, 4-polyisoprene, such as greater than S5%_> more especially greate than 90%, even more especially greater than 95% cis*l, 4-polyisoprene. Suitable synthetic poiyisoprene latexes include Cariilex® 1RQ401. and BSTS IRL 701.

[00027} in some embodiments, the at least one stabilizer is selected from a metal hydroxide, mi. anionic surfactant and air anionic dispersant or a combination thereof_* Suitable metal hydroxides include, but are not limited to, potassium hydroxide, sodium hydroxide or aluminium hydroxide. Suitable anionic surracianis include, but are not limited to, alkyi sulfates and_. aikyl. benzene sulfonates and salts thereof, where the alky! group may be linear or branched,, especially « to C_!8 alkyi sulfates and€§ to Cis a!kyl benzene sulfonates and salts tliereo.il more especially Ci to C alkyi suliaies and€¼ to Gi alkyi benzene: sulfonate or salts. hereof,, mos especially alkyi sulfates and C n- alkyi benzene sulfonates and salts thereof, such as sodium dodeeyl (lanryi) sulfat (SLS) and sodium dodeeyl benzene sulfonate (SDBS). Suitable anionic dispersants include, but are not limited to, sulfonated naphthalene and salts thereof, more especiall polymerized alkyi naphthalene sulfonic acids and salts thereof, such, lis sodium salt of polymerized aikyl naphthalene sulfonic acids.

[00028] In some embodiments, the amount ofat least one stabilizer in the composite corn positio n i s from about 0> 1 ph to about 5.0 phr, especially from about 0, 10 plir to: abotit 3,0 phr, more especiall from .0,1 phr to 2.0 phr. In particular embodiments, the at least one stabilizer comprises potassium .hydroxide in: an amount of from: about 0.01 phr t about 0.50 phr, in some embodiments, the at least one stabilizer comprises sodium dodecyl sulfate in an amount of irora about 0,50 phr to about 2,0 phr- in some embodiments,, the at least one stabilizer comprises sodium salt of polymerized alky! naphthalene sulfonic acids in an amount of from about 0.10 phr to about 1 , phr.

[00029] in some em bodiments, the graphene oxide consists essentially of oxidized graphene sheet (or 'graphene oxide sheets') having their basal planes decorated with epoxide and. hydroxy! groups, in addition to catbonyl and eafboxyl groups located at the, edges (Lerf-Sinowski model) |Chua and Pumeim Chem. Comm., 2016, 52, 72-75]. The^■amount of graphene oxide .is the composite composition is irom about 0.01 to 1.0 phr. Once the graphene oxide comes into contact with the coring agent, at least some -of the hydroxy! groups and caxboxyiic acid groups are reduced to provide a partially reduced graphene oxide.

[00030] The caring agent is present to assist in curing the elastoraerie oomposition when required. ^'However, it is also proposed that the curing agent assists in the reduction of the graphene oxide. In particular embodiments, the at least one curing agent comprises at least one of sulfur, a ihioearbajnate such as zinc dihuiyl

ditliiocarbamate (ZDBC) and zinc diethyl dithiocarbamate (ZDEC) a thioiam such as dipentamethylene thiuram tetxasu! 14e_»..tetrabe«2:yl thiuram disulfide, tetraethyl t-ilurarn disulfide, tetram.ethyi thiuram disulfide, teirahutyl thiuram disulfide and■ tetraisobutyl thiuram disulfide; a thiourea such as ethyl thiourea (ETU) and diphenylt ourea

(DPTU); tiiiazoles such as meteapto henzothi&zoks (K4.BT), mercapto beuzotliiazole disulfide (MBTS) and zinc 2-mereaptobenzothiazole (ZMBT) goanidmes such as diphenylgtianidine; aldehyde/auiine based accelerators such as hexamei&ylene- tetrainine; metal oxides such as lead oxide, magnesium oxide, barium oxide, zinc oxide, manganese oxide, copper oxide, nickel Oxide and aluminium oxide, metal hydroxides such as barium hydroxide, manganese -.hydroxide, copper hydroxide, nickel hydroxide, aluminium hydroxide; or mixtures -thereof. In particular embodiments, the at least one curing agent comprises at least one curing agent selected from sulfur,, a

dithiocarbomate- a tbiazole and a metal oxide, in some embodiments, the at least one curing agent is a combination of sulfur, a dithiocarbamate, a thiazole and a metal oxide. In some embodiments, the at least one curing agent consists essentially of a

combination of suite, zinc diethyiditniocarha aie, zinc dIbui iditi¾ocarbar«.ate, zinc- 2- ntercaptobenzothiaa-ole and z nc oxide.

00 311 hi some embodiments, the amount of at least one curing agent in the.

i> composite composition is front aboai 0.50 phr to about 8.0 phr, especially from about 0,50 phr to about 5.50 phr. hi particular embodiments, the at least on coring agent comprises sulfur in an amount of from about 0.3 phr to about 1.5 phr. In some embodiments, the at feast one curing agent comprises dithiocarbam es in an amount of from about 0.1 phr to about 2.0 phr, hi some embodiments, the at feast one curinQ agent comprises thiazok in ait -amount of from about .0.0 phr to about 1.0 phr. In some embodiments, the at least one curing agent comprises metal oxide; in an amount of from about 0,1 phr to about !.0 phr.

[00032] ^'The composition- of the invention may als include additional optional components such as pH adjusters, antioxidants, aatfozonants and solvents.

¾ [00033] The pH adj aster is used to maintain the grapheme oxide and composite

composition at the required , The pH of the composite composi tion is suitably adjusted to be in the range of about 8,5 to about 13.5, especially in the range of about 9 to about 12,0. Exemplary -pH adjusters incl de potassium hydroxide, sodium hydroxide and/or .ammonium hydroxide, especially ammonium hydroxide. The amount of pH8 adjuster cat range from about 0,1 to 3. hr, 0J to 2,5 phr, 0.1 to 2.0 phr, 0.1. to 1,5 phr, 0.1 to 1.0 phr, 0.1 to 0,5 phr, 0.1 to 0.3 phr, 0,2 to 3,0 phr, 0.2: to 2.5 phr, 0.2 to 2,0 phr, 0.2 to 1.5 phr, 0.2 to 1 ,0 phr, 0.2 to 0.5 phr, 0,2 to 0.3 phr, 0.5 to 3.0 phr, 0.5 to 2,5 phr, 0.5 to 2.0 phr, 0.5 to 1.5 phr or 0.5 t 1.0 phr,

[00034] An antioxidant may be added to the composite composition of the. present 5 invention. Suitable antioxidants include hindered arylamines or polymeric hindered phenols, and iagstay I or Ral x LC (the product of reaction of p-cresol and diey opentadiene). The antioxidant may, for ex-am le, he added in ah ^'.amount ranging from about 04 to about 3.0 phr, such as about 0.1 to about 2.0 phr, a out 0.5 to about 3 ,5 phr or about 0.5 to about 1 , phr, o [00035] Antiozonants may be Used In the eiastometic eomposite .composition,

Suitable amtosxHtants include paraffinic vvaxes, microcrystallioe waxes and

intermediate types (which are blends of ^'both paraft nic and macrocrystalline waxes). The amount o antiossonant. may range From about 0, i to about 5.0 p¼ 0,1 to about 3.0 phr, about 0.1. to- about 1.5 phr, about 0.5 to about 5.0 phr, about 0.5 to about 3.0 phr, or about 0,5 to about 1.5 phr.

[0003 ] The_.elastome.rie composition may also comprise a solvent, ϊη some embodiments, the solvent is an aqueous solvent such as water or ammoiHated -water, in some^■embodiments, the water content is 30 to 65%, especially 35 to 55%, more especially 40 to 45 % w w of the composition, in particular embodiments,_, the pH of the composition is in .the range of 9 to 13 , especially 10 to 12,

[00037] The total solids content of the composition is m tlie range of 30 to 80 %, especially 40 to 50 % or 50 to 65%, in, some embodiments, the total solids content is in the range of 40 to 55%.

Methods of preparing reduced graptiene oxi e

[00038] In another aspect of the invention there is provided a method of preparing reduced graphene oxide comprising:

a) adjusting the pH of a graphene oxide composition to between abou 8 and 12; h) adding to tlie pi t adjusted graphene oxide composition at least one curing agent;

c) mixing the graphene oxide composition by slow agitation at a temperature in the range of from about 20 °G to about 8 °C for a period in tlie range of about 4 to about 24 hours, 0003 ] The pH adjuster is used to maintain the graphene oxide composition at the required pH. The pH of the graphene oxide composition is suitably adjusted to be in the range of about 8,0 to about especiall in the range of about 9 to about 12.0. Exemplary pH adjusters include potassium hydroxide, sodium h roxide andlor ammonium hydroxide, especially ammoftitim hydroxide. The amount of pH adjuster can range from about 0.1 to 3,0 phr, 0.1. to 2,5 phr, 0.1 to 2.0 phr, 0.1 to 1.5. hr, 0,1 ^'to 1 ,0 phr, 0. i to 0.5 phr. 0.1 to 0.3 phr, 0.2 to 3.0 phr, 0.2 to 2,5 phr, 0,2 to 2.0 phr. 0.2 to 1_.4 phr, 0.2 to 1.O phr, 0.2 to 0.5 phr, 0.2 to 0.3 phr, 0.5 to 3,0_.phr 0,5 t 2. phr, 0.5 io 2.0 phr, 0,5 to 1 ,5 -phr or 0,5 to 1,0 phr. - 8 - 000 0] in particular embodiments, the at least one curing agent comprises at least ne of sulfur, a thiocarba ate such as zinc dihutyl dithioeatbam e (Z BG) and zinc diethyl ditbiocarbama e (ZDEC); a ihiurain such as dipentamoifeylene ihittram fstrasulfide, teirahemyl -thiuram disulfide_., teiraeih lt uram disulfide, tetramethyl thiur&m disulfide, teirabntyl thiurara disulfide and tettaisoburyl ibiuram disulf e; a thiourea such as ethyl thiourea .(BTU) and diplienyiihiourea (OPTO); ihiazoles such as meteapto benzothiazolss (MBT), mereapto benzothiazole disulllde ( 8TS) and zinc-2~ meroapt0ben¾oiliia¾>le (ZMB^'t) guanidines such s dtphenylguanidme;

aldebyde/amine based accelerators such as hexamethylene-tetra ine; metal oxides such as lea oxide, magnesium oxide, barium oxide, .zinc oxide, manganese oxkie, copper oxide, nickel oxide and aluminium oxide, metal hydroxides such as bari «m hydroxide, manganese hydroxide^ copper hydroxide, nickel hydroxide, aluminium ^'hydroxide; or mixtures 'thereof.. In particular embodiments, the at least one curing agent comprises at least one curing agent selected H ^' orn suifutva dithioearbamate, a tMazele and a metal oxide. M some embodiments, the at least one curing agent is a combination, of sulfur, a dithioearbamate, a thi.azoie and a metal oxide. In some embodiments, the at least one curing agent consists essentially of a combination of sniiur₅ zinc

diemy Idithiocarbamate, mm dibntyldithioca bamaie, zinc 2-:mereaptehenzaihia¾oie_: and, ;dnc oxide.

[000 1 J i some embodiments, the amount of at least one curing agent in the-, composite composition is from about O_>$0 phr to about S,0 phr_s especially from about 0.50 phr to about 5,50 phr. In particular embodiments, the ai least one curing agent comprises sulfur in an amount of fi¾m about 0.3 phr to about 1.5 phr. In some embodiments, the at least one curing -agent comprise dithioearbamates in a . amount of iro * about: 0.1 phr to about 2,0 phr. In some embodiments, the at. least. one caring agent comprises a thia ole in an amount of from about 0.01 phr to about 1.0 phr. In- some embodiments, the at least one curing agent comprises a metal oxide in an: amount of from about 0.1 phr to about 1.0 phr.

[00042] In some embodiments, at least one stabilize is added at step a). In some embodiments, the at least one stabilizing agent is an anionic c&persaft In particular embodiments, the anionic dispersant is selected from a sulfonated naphthalene and salts thereof, more especially polymerized alky! naphthalene sulfonic; aeMs md salts thereof, such as soditun salt of polymerized aJkyl naphthalene sulfonic acids.

[00043] The at. le st one stabilize Is present in an am unt in the range of 0.1 phr to 2.0 ph , !n. some embodiments_* the at least one stabiliser com rises sodium salt of polymerized aikyi naphthalene siiifbrsie acids in an amount of from about 0.10 phr to about 1,0 pkr,

[00044] The r¾duc¾g effect of the: curing agents on the grapbene oxide increases with temperature and with time agitated. As the temperature of the reaction is: increased, the reducing effect is increased. Furthermore, the longer me reaction is agitated, the mor reducing effect is observed. As the reaction progresses, the mixtur changes from brown colour to black colour. The temperatiire of the reaction mixture and the time agitated, for may be adj usted to provide the desired extern of reduction of the graphene oxide. ¾ articular emboduirents, the graphene oxide is partially reduced, In some embodimen ts, the reaetion mixture i s agitated for a period of time in the range of 10 to 24 hours, especially 15 to 2 hours, in some embodiments, the mixture is agitated at a temperature of20 ^aC to 80 ^aC, especially 30 °Cto 50 *€.■

Methods of preparing a po!yisopreEfe latex grap&eae composite eoiflposstioM

[00045] In one aspec t of the invention, there Is: provided method of preparing a poiyisoprene latex graphene com posite composition comprising:

a) Preparing, a composition of reduced graphene oxide b

i) adjusting the pH of a graphene oxide composition to in the range of: about 8 and 12;

ii) adding to the pH adjusted grapbene oxide composition at least o-ue

euring agent;

ill) mixing the graphene oxide composition by slow agitation at a temperature in the range f from, about 20 °C to about 80. °C for a; period In the range of about to about 24 hours;

b) preparing, a stabilized poiyisoprene latex composition by mixing a

poiyisoprene late with at least one stabilizer under slow agitation for a time period in the range of about 4 to about 24 hours; and c) eoaib ia the reduced graphene oxide composition of step a) with the stabilized poiyisoprene latex composition prepared in step h) and mixing, 00046] in some m o imen s, the reduced graphene oxide^■■composition is prepared as described above,

[00047] In some embodiments, the pi^-st bllized poiyisoprene latex is stabilized by at least one -stabilizer selected from a metal hydroxide, an anionic surfactant arid art anionic dispersant or a combination thereof, especially metal bydroxide and/or art anionic surfactant Suitable metal hydroxides include,, but are not limited to* potassium hydroxide, sodium hydroxide or aluawnium hydroxide. Suitable anionic surfactants include, bui are not limited to, alkyl sulfates and alkyl benzene sulfonates and. salts thereof, where the alkyl gr u may be linear or branched, especially C¾ to€** alfeyi sulfates aad C_$ to alkyl benzene sulfonates and salts thereof;, more especially€¾¾ to Ci alkyl sulfates and C so to C 54 alkyl benzene sulfonates or salts tlier-e-of most especially Cu alkyl sulfates and ¾ alkyl benzene sulfonates and salts thereof, such a -sodium dodeeyl (lauryl) sulfate (SL-S) and -sodium dodeeyl benzene sulfonate (SOBS), In some embodiments, the stabilizer is combination of metal hydroxide and aniorae surfactants, especially a combination of potassium hydroxide and sodium dodecy I sulfate.

[0004S] In some embodiments,: the -.amount of at least one stabilizer in the stabilized poiyisoprene latex composition is from, about 0.01 phr to about 5.0 phr, especially l¼m about Ci.lO phr to about 3.0 phr, more especially from 0.1 phr to 2.0 phr. In particular embodiments, the at least one stabilizer comprises potassium hydroxide in an amount of from about 0,01 phr to about 0,50 phr. Irs. some embodiments, the at least one stabilizer comprises sodium dodeeyl sulfate man/amount of from about 0,50 phr to about 2.0 phr, [00049] In step e) the reduced graphene oxide composition and the. stabilized poiyisoprene latex composition ar combined. The reduced graphene oxide

composition may be added to the poiyisoprene latex composition or the poiyisoprene latex composition may be added to the reduced graphene oxide conipositi on, I general , the reduced graphene latex composition is a smaller volume and is therefore conveniently added to the poiyisoprene latex composition.

[000501 i^¾ some embodiments, the mixing at step c) is carried out at- room

temperature- (room temperature latex mixing). In other embodiments., the mixing at step c) is carried out by slow agitation at a temperature in the range of 40 °C to about 70 especially 40 °C to 60 °C, (hot. maturation) for a period of about 8 to about 24 hours especially about 12 t 1.6 hours.

[00051] In s ep c), the pGiyisopfene-latex composition is slow agitated until the components have been mixed uniformly or to homogeneity, in some embodiments, this requires 8 to 24 hours of slow agitation.

[00052] After mixing- at room temperature, the composition is allowed to mature at room temper&iure until it has reached a pre-eure of 80 - 1 0 % swell in toluene, GeneraU %.:ntatUfation_: -occurs- over.a period -of from about 1 to 15 days especially from about 5 to 10 days. As maturation occurs, the % toluene swell drops, indicating at least some cross-linking of the polyssoprene latex has taken place.

[00053 ] After use of the hot maturation process f slow agitation at 40 °C t about 70 °C. especially 40 °C to 60 °C for a period of about 8 to about 24 hours, especially about 12 to 16^■ hours, the composite composition will have attained -a prc-cure of SO - 1.00% swell in toluene and will be ready to u e.

[00054] In general, colloidal stability of the polyisoprene latex, tends to. decrease with increasing age of latex. Destabllizaiioir of colloidal latex is normally indicated by increasing viscosity and decreasing mechanical stability after compounding.

Incompatibility between reduced grapheme oxide aid polymer matrixes could further aggravate fee stability of the latex. In the present invention, colloidal stability of the composite significantly improved even with the use of older age latex.

[00055] The reduced graphene oxide showed. good compatibility with polyisoprene latex as homogeneous dispersion of graphene in the latex ilm is observed. Figure I shows network visualization of the latex film cast f om the composites_* Distortion of the _: latex particles adjacent to the reduced graphene oxide is obse ve , this indicates that the reduced graphene oxide particles are connected to or crossllnked with the latex particles.

[00036] Preparation of the composite composition is accomplished by using a normal latex . mixing method without the need of n!trasoni cation or high shear mixing.

Furthermore, the reduced graphene oxide Is prepared; without the need of strong inducing agent or organic solvent. Elastomerk articles asd methods for inaksag theirs

[00057] In yet another: aspect of th present inv.eatk¾¾ there is provided a method of making an efastemeti.e article cos'iprisiagr

a) preparing a polyisopren latex graphene. composite composition, as described above;

b) dipping a former into ^'the polyisoprene latex graphene composite compos tion to form arc^■elastomeric film on the former; and

c) curing the eiastornerie film.

[00058] In yet another aspect, there. is provided an elastomeric article prepared by d e above method.

[00059] The elastomeric article may be prepared using conventional equipme t. |O0O6O] In particular embodiments, the elastomeric article is selected foam a condom, a glove, a probe cover, finger cots, catheters, tubing, balloons for catheters and the like, in particular embodiments the elastomeric article is a condom.

[00061] The former suitab le to make the ei.asiom.erie article of choice is dipped into the elastomeric composition described above.

[00062] In some embodiments, the former, typically glass or ceramic, is cleaned and dried prior to dipping in the elastomeric composition. .Cleaning i an important process to avoid imperfections such as pin holes in the elastomeric articles. Cleaning may be performed in alkaline solution, for ex m le_s with sol utions of ammonia, sodium carbonate (soda ash) or sodium hydroxide. After wasrhng with alkaline .solution, the former is rinsed clean with water and dried. The former may be dried by brashing, with an air curtain or with hot air. The former is then allowed to come to room temperature before the dipping ste is performed.

[00063 ] The former is dipped k the polyisoprene latex graphene composite composi tion for an. amount of time to ensure the former is evenly coated, but not so long as to develop a thicker than necessar coating. The time in which the former is in the elastomeric composition depends on the desired thickness of the polyi oprene latex graphene composite iilm. Typical times in which the former is held, in the elastomeric. compositio include from about 1 to about 60 seconds, for example, between about 1 and about 50 seconds, about 1 ahout 40 seconds or about 1 to about 30 seconds. In particular embodiments, the dipping process is a continuous process. In some enfoodinients, the time- between immersion and withdrawal of the former from the poiyisoprene latex graphene composite composition is about 1 to 5 seconds.

[00064] in some embodiments, the e!asteffierlc composition is .maintained at a temperature between 20^'3C and 30^"SG- during the dipping step,

[00065] In some embodiments, the poiyisoprene latex graphene composite

composition is constantly mixed to ensure good homogeneity of the composition during the dipping process,

[00066] The poiyisoprene latex graphene composite coating on the dipped former is then allowed to at least partially dry. The drying step may be carried out at room .temperature or may be carried out at elevated temperature for a time sufficient to. at least partiall dry the poiy isoprene latex graphene composite coating. In .particular embodiments, the poiyisoprene latex graphene composite coating is fully dried. For example, in a particular embodiment, the poiyisoprene latex graphene composite coating on the former is dried at about 40^<5C to about 10O°C for about i to abou 10 minutes, especially about 50*C to about 90^SC for about I to about 8 minutes or about 60°C to about 0°C for about 1. to abou ? minutes or about 70°C to about 90°C fo about ! to about 5 minutes.

[00067] Optionally th steps of dipping the former into an poiyisoprene latex graphene composite composition and at least partially drying the poiyisoprene latex graphene composite coating are repeated one or more times to provide two or more coats of eks tomeric compositi on on the first coating of poiyisoprene latex graphene composite composition. In some embodiments, in the first dipping step and the second dipping, step and any subsequent dipping step, the elastomerie composition into which the former is dipped- Is the same poiyisoprene latex graphene composite composition, in some embodiments, the second drying step Is performed at a temperature and for a time sufficient to at least partially dry the second poiyisoprene latex graphene composite coating, in some embodiments, the second drying step is the same as the first drying step, i other .embodiments.- the second ^'drying step is different from the first drying step. For example, the second ^"drying step may occur at a temperature lower than the first drying step wher the poiyisoprene latex graphene composite coating on the former is dried, at about 30*C to about 90^dC for about 1 to about 10 minutes, especially about 40°C to about 80°C for about 1 to about 8 minutes or about 50°C to about 80°C for 2 to 6 mmuteS In some emlx>dJmenis_? onl one pping and drying ste Is used to form the elastomeric article. In other embodiments, more than one dippin and dry ng: step are used to form the ekstomerie article.

[00068] Ik former and^' dried polyisoprene latex gntphene composite coating m y be used directly in the next-step or may be cooled to room temperature, The former and polyisoprene latex grapheme composite coating may he cooled to a desired temperature if a further dipping ste is .performed. The Conner and polyisoprene latex gfaphene composite coating may be used directl in the curing step if no further dipping step is performed,

[00069] Once the desired number of layers of pol i soprene latex grapheme composite coating has been achieved, the polyisoprene latex graphene composite coating is cured to form the elastomeric article. The earing step may be performed i an oven at a temperature between -about 60*C and about I 20°C, especially at a temperature of about ^'60°C .to about it °C_s about 60 C to about HKPC or about 60°C to about 90°C. The curing may be performed for a time that provides effective cross! inking between synthetic poiyisopreoe particles in the polyisoprene latex graphene composite coating and in some embodiments erosslinkiiig between the graphene oxide particles and the polyisoprene latex particles. For example, curing may occur over about 10 to about 60 otinutes, especially about 10. to about 50 minutes, more especially about 10 to about 40 minutes, more especially about 10 to about 30 minutes. In some embodiments, ^' the. curing step is .performed using hoi air, in other embodiments, the curing s e is performed usin - infrared radiation,

[00GTO] The elastorneric article can be subjected to one or more furthe process steps prior to stripping of the film or article from the former. These optional steps Include cooling, chlorinatiom post-curing rinsing, polymer coating, powder coating and additional dry ing steps. The use of these steps may depend on the elastomeric article being produced,

[000 ? 1 J A- post-curi ng rinse and leaching step may be performed to remove extraetable components, for example, unwanted or unreacted components such as surfactants and salts, in some embodiments, the elastomeric article -on the former is soaked in wate to leach any soluble components. In other embodiments,, the elastomeric article on the former is soaked in ammoniated water, weak potassium hydroxide or weak sodium hydroxide '.solutions, for example, otassium or sodiuin hydroxide solutions that are about 0.5 to 1.5%. The rinsing or leachmg solution may be carried out at ambient temperature or at elevated temperature. For example the riming or leaching solution may be at a temperature between ambient temperature- and about SO S °C, such as about 40 °C to about 80 °C, about 50 °C to about 80 °C or about 55 °C to about 75 *C. The elastomeric film and former may be dipped In the rinsing or leaching solution for a time sufficient, to remove the desired amount of soluble components. For example, a suitable time is about 1 to about 30 minutes, especially abou 1 to about 20 minutes, more especially about 1 to about 10 minutes, most especially about 1 to about0 5 minutes.

[00072] The elastomeric article may be stripped from the former using known techniques_* For example_* the elastomeric article ma be stripped by the former using an •alkaline water and/o powder. slurry and/or brushing. The powder slurry coatains silica and/or calcium, earbouate and has a alkaline pH in the. range of about 8.0 to 10.0.5 [00073] Once the elastomeric- .article is stripped from the former, it is washed ^'before being dried, Suitably, the elastomeric article is washed with a slurry comprising silica a&d/or magnesium carbonate and or calcium carbonate and/or modified cornstarch -and/or with a silicone emulsion. Suitable slurries are commercially available. A •suitable drying step would be to tumble -dry the^■elastomeric articles at. a suitable0 temperature for suitable time. Typically, the elastomeric articles are tumble- dried at a temperature between about 90 °C and about 1 10 ^CC for a time between about 3.0 to about 60 minutes.

[00074] Additional steps may be included in the method of making the elastomeric article as required and as known in the art. For example, in the manufacture, of some 5 elastomeric articles, such as gloves and catheters, the former may be initially dipped in •a coagulant solution, in the manufacture of condoms, alter the dipping steps are complete and before the curing^' step, a ring ma be formed on the condom and after curing, the condom may be electronically tested for pinholes, lubricated, roiled and packaged in foil Gloves may be subjected to beading/cuffing to create a bead or cuff at¾ the wrist edge of the gl ve,

[QQ075] in the case of condoms, In particular embodiments,, after the condom is removed from the former and dried, It is subjected to electronic testing on a high voltage pin.*hole machine as known in the ait, Bor example, the condom is put cm an. ■aluminium mandrel manually and the mandrel Is rot ted against a counter rotating conductive rubber brush, A high voltage current is then applied via the co ductive brush. As the condom is m de of rubbe latex, which- ^'has an insulativ roperty, an ¾ pin-bole present on t e surfac will trigger the test m chine to remo e it automatically to the reject bin, The remaining condoms are then rolled up and collected for foiling.

[00076] Foiling of condoms is done by methods known in the art.: For example, th rolled condoms are placed o a feeding belt, transported, and automatically squeeze int the cells of sealing cytkders. The condoms are prefabricated with lubricant such xo as optionally flavored silicone fluid white on the feeding belt of the foiling machine.

During the placement In the sealing cylinders, the condom has direct : contact with the foil, which is a heat-sealahie film, taken from two reels and surrounding the condom. The edges of the film are then hermetically sealed,

[00077] la some embodiments,, particularly those -^'where the elastomeric article Is a 15 glove or catheter, the optional step of dipping the former into a coagulant solution -is performed before the former is dipped in the eiastomeric composition. The ; clean forme is dipped into a coagulant solution to provide a thin coating of coagulant on the former. In some embodiments, the coagulant is a salt solution containing Ions. In this embodiment, dipping the former into the coagulant leaves a thin coating of the charged -2-0 ions on the surface of the former. The charged ion. coating can. assist In controlling the amount eiastomeric composition tha will subsequently remain on the surface of the former after dipping into the composition,, through. charge interactions.

[00078] The coagulant composition may include ions that are eatiome or anionic. Generally metal Ion solutions .containing cations are suited to a broad range of

25 eiastdmerie polymers. Examples of such metal salt ions are sodium:, calci m,

magnesium, barium,, zinc, and aluminium. The counter ions may be halides (such as chloride), nitrate, acetate or sulfate, .amongst others. In the ease of calcium ion- contalnirtg coagulants, the calcium Ions can be provided as a solution of calcium nitrate or calcium chloride.

30 [60079] The coagulant may also include any other agents,, such as wetting_, agents (such as fatiy-alebhoi poxide^' or Other suitable surfactants), anti-tack agents, anti- foaming agents and/or mould release agents_f such as silicon emulsions, polymer release ageiiis_:ai¾$ metallic stearates, examples of whic are zim, calcium and^■potassium, siearafes,

[00080] The ^' concentratiotvof ions in the coagulant can broadly be in the range of 0,0 ~ 50% by weight of the coagulaa solu io (me snred as the com onnd of the multivalent. 5 ion in the solution of the multivalent ions), depending on the desired thickness of the eiastomedc film layers and the number of layers to b applied. ,(i,e. one layer or two or oiore layers) , In "the case of thinner layers,, the concentration . is suitably in the range o

0.0 ~ 20%, 0.0 - 15%, 0.0 - 12%, 1,5 - 20%,, 1.5 15%, 1 ,0 ~ 1:0 15 ~ 10%, 4 -

10%, 3 - 10%, 5 - 35%, 10 ~ 30%, 7 ~ 40 , 8 - 50% and 5 43%, Preferably, the i (5 concentration is in the range- f 1.0. - 30%.

[000811 The coagulant may also inel ude, metal! Ie stearates in a concentration in the range of about 0,1-5.0% by weight, suitable "wetting a e s: in .a concentration in tlie range of about 0.001 -1.0%, and/or anttfoammg agents in a concentration in the range of 0,00! -1.0% by weight.

15· [00082] The former may be d pped . into the coagulant com osition lor a period of about 1 to about 30 seconds, for .example, about 5 to about 20 seconds, about 5 to abont } 5 seconds : o about 1 to 10 seconds,

[00083] The ekstOmerie article may be made from one layer or ^'multiple layers of the composite,

2¾ [00084] The thickness of the final elastomeric film will depend on the number of layers of polyisoprene latex graphene composite composition used it make! the elastornsfic article. The thickness of the final film can: be i the range of 0.01-3 mm, for example, 0.01-3,0 mm, such as 0,01-2,5 rao 0,01 -2,0 ntm, 0.014.5 mm, 0.01-1.0 mm, 0.01-0,5 mm, 0.01-0.4 mm, 0.01-0,3 mm, 0,01-0,2 ram, 0,02~0»2 mm,.0.01~0.I0

2¾ mm, 0.03-3,0 mm, 0.03-2.5 mm, 0.03-2.0 mm, 0,03-1.5 mrm 0.03-1,0 mm, 0.03-0,5: m¾ 0.03-0.4 mm,. 0,03-0.3 mm, 0.03-0.2 mm, 0.03-0.10 mm, 0,05-3,0 mm, 0.05-2.5 mm, 0,05-2.0 nun, 0,05-1.5 mm, 0.05-1.0 mm, 0.05-0.5 mm, 0,05-0,4 mm, 0.05-0.3 mm, 0.05-0.2 mm, 0,05-0.10 mm, 0.08-3.0 mm, 0.08-2.5 mm,_: 0,08-2,0 mm, 0.08-1,5 mm, O.08- 1.0 mm, 0.08-0.5 mm, 0,08-0.4 mm, 0.08-0.3 mm, 0.08-0.2 mm, O.OS-O.IO

30 mm, 0.1.-3.0 mm, 0.1-2,5 m , 0,1-2,0 mm, 0,1-1,5 mm,, 0,1- 1,0 min, 0.1-0,5 nun, 0.1- 0,4 mm, 0,1-0.3 », 0,1,-0.2 mm, 0,15-3,0 mm, 0.15-2.5 mn 0,15-2,0 mm, 0,154,5 mm, 0.15- i .0 mm, 0. 5-03 mm, 0,15-0.4 mm, 0,1 -0, mm, 0, 15-0.2 mm. 0.02-0.08 mm, 0.03-0.08 mm, or 0.05-O.0S xrnn. in particular embodiments, the elasiomerie article ^'has a thickness of 0.05: ΐο 0ΛΟ mm,

[00085] The elastornerie articles of the present invention. &&v& good _: or enhanced mechanical properties,

5 100086 to some embodiments, the elastometfc articles of the invention ave a^■ higher tensile strength, a higher modulus at 300%, 500% and 700%, sii¾iiar elongation to break when com ared to elastonieoc articles produced from aoitlied, vulc nis d (cured} p lyisopreae latex. The tensile strength, modulus at 300%, modulus si 500%,. modulus at 700% and eloagaiiori to break can be measured using standard methods.

1.0 known in the art such as ASTM Test Method D412~06 (2013).

[00087] The elastonierie articles of the present invention also have good ageing resistance. This was tested by accelerated aging procedures to determine whether the elaslomeric articles would deteriorate upon storage, in the present case, elastoraeiie articles made by the methods of the present invention were subj ect to heat aging for -22

I s ho ars at iOO *C, The heat aged samples were tested, for tensile strength, modulus .at 300%, modulus at 500%, modulus at 700% and elongation to break and found to have better physical, properties and retention as compared to unfilled, vulcanized

polyisoprene latex and composite prepared using normal mixing method,

[00088] Without wishin to be bound by theory, it is believed that the improved

20 mechanical properties^' could ¼ attributed to the ^'bondmg/cotmecti0a cros§linkt«g

between the rubber (polvisoprene latex) particles and re uced graphene oxide.

[00089] in order that the invention be readily understood and pu into practical effect, •particular embodiments -will-now be described by way of the following non-limiting examples,

EXAMPLES

Exam le J

a) polyisoprene latex graphene composite graphene composite having the components set forth in Table I was formuiated as follows All. components set forth in 3D Tabl 1 are reported as parts per hundred rubber (phi).

h) ^"The :.pH .of the. grapheme oxide of Part B of Table 1 s adjusted to about 10 using, a 0,5% ammonium hydroxide solution. The pH adjusted graphene oxide was then misecl with the other co«noneMS listed in ^'P rt C of Table 1 wider slo agitation at 30 - 35 *C fot 16 hours. During this %im the com osition changed ...colour from light brown t dark brown/black,

c) The polyisopretie latex composition was prepared by mixing the components of Pari A in Tabl 1 for 12 to 16 hours at room temperatu e_*

d) The polyisoprerie gFaphene composite was prepared by adding the reduced, graphsne composition prepared in h) above to the jx iyisoprene latex composition of c) above and stirring slowly at room temperahite (Method 1). fable 1 Rubber graphene c mposite eowpositions

e The composite prepared by using room temperature mixing preparation methods, with about to about 1.00% swell in toluene were used to produce latex films wiih thickness between 0.050: - 0.070 nan.. An unified, vulcanised polyisoprene latex film was prepared using the components of parts A and C of Table L. The ^'"films were prepared by dipping a former -into the composite. The former m dipped into the composite twice with about 2 to 3 second dwell time in the composite. The first layer of the dip film was partially dried at about 70*0 for 1 - 2 minute before the second dip occurred. Bach of the films was then cured at about JOC C for 15 .minutes-. The tensile 5 strength, 300% modulus, -500% oiodulus, 7©0% modulus and elongation of each cured film wer tested in accordance with AST Test Method D412-06a (2013) "Standard Test Methods for Vulcanized Rubber and T!iemioplastic Elastomers— ensioii". The^' results are set. forth in Table 2,

Table 2 Physical properties of latex films prepared usin composite i o compositions

br ak, % ) The initial physical properties i.e tensile strength, 300% modulus, 500%. .modulus, 700% modal-Us and elongation of the elastonierio articles from the present iriverasoii is higher compared to unfilled, vulcanized latex films. About 6% to -about 27% isserease on various properties observed for Method 1.

g) The latex films also subjected to accelerated ageing at I0Q-C for 22 honrs, The heat-aged samples were tested for tensile strength... 300% modulus, 500% modulus. 700% modulus and elongation pplying ASTM Test Method D412-06a (2013). Percentage retention on the physical properties of the composite is higher as compared ^•to unfilled, vulcanized latex film. Percentage -of^■ retention for tensile strength, ^'300% modulus, 500% modulus .and 700% modulus increased by 4%, 10%, 8% and 20% respectively for Method 1 ,

Example 2

a) Polyisoprene late graphene composite having the com onents set. forth in Table 1 was formulated, as follows. All components set forth In Table I are reported as parts per hundred rubber (phr),

b) The polyisoprene latex composition was prepared by mixing the components of Part A. in Table I for 12 to 1.6 hours at room temperature,

e) The pH of the .graphene oxide of Part: B of Table 1 was adjusted to about 12 using a 25% ammonium hydroxide solution.

d) The pB adjusted graphene oxide was then mixed with the other c mponents listed in Part C of Table I under glow agitation at 35 °€ fo 16 hours. During this time, the composition change colour from light brown to dark hrowi¾'¾laek.

e) The poiyisoprene graphene composite was prepared by adding the .reduced graphene composition prepared in d) above to the poiyisoprene latex composition of b) above and stirring slowl -at .45 - SO ¾ (Method 2),

The composite prepared by hot maturation attained about: SO to about 90% swell after 16 hours of -matu tion, ^'fhe composite late were used to produce _: latex -films- with. hiekfiess between 0.050 - 0.070 m. The films were -prepared and tested using the same methods as c) in E am pie 1. The results are set forth- it* Table 2 above.

Exam le 3

Colloidal properties of the composite formulated by methods known in the art is s shown in Table 3,

Viscosity of the composite compositions compound d- using about 3 month, old latex is summarized m Table 3, Based on the results, viscosity of the composite prepared by the methods of -the invention showed the lowest value. This indicates that the composite prepared by the method of invention is stable.

Claims

Ϊ . A poiyisoprene late graphene composite composition comprising:

a, poiyisoprene latex;

b. at least one stabilizer;

5 c, at least one curing agent; and

d. graphene oxide,.

2, The composition according to claim 1 wherein the at least one stabilizer is

selected: liom a n eial hydroxide, an anionic surfactant, m anionic dispersant or a combination thereof

i o 3, The composition according to claim 2 ^'wherein the at least one stabilizer is

selected iron) potassimn hydroxide, sodtura dodecyl sulfate, sodium salt of polymerized alkyl naphthalene sulfonic acid, and mixtures thereof 4, Hie composition according to any one of claims 1 to 3 wherein the at least one stabilizer is present in an amount of from about 0.01 phr to 5.0 phr.

15 5- The composition according to any one of claims .1 to 4 wherein the at least one curin agent is sulfur, dithmcarbaraates, thiazol s, zinc oxide or mixture thereof.

6. The composition according to claim 5 wherein the dithiocarbaraates are selected from zinc diemydiihioearbamate and zinc - dib tyldithiocarbamate or a

20 combination thereof.

7. The composition according to claim. 5 and claim 6 wherein the thiazole is _: zinc.2- mercapiobenzothiazole.

$. The composi tion accordin to any one of claims 1 to 7 wherei the at least one curing agent s present in an amount of from 0.5 t 8.0 phr.

5 9, The composition according .to any one of claims 1 to 8 further comprising an antioxidant

10, The composition according to claim^' 9 wherein the antioxidant is a hindered ajylamin©^' or a polymeric hindered phenol or the reaction product of p-eresoi and dieyclopeniadiene.

30 1 1 , The composition according to claim. 9 or claim 10 wherein the antioxidant is present in an amount of from^' OJ to 3,0 phr.

12. A composition according to any one of claims ! to 1.1 further comprising pH adj lister.

13. A com position according to claim 12 wherein the pH is in the range of from 8.5 to 13.5.

14. A composition according to any one of claims 1 to 13 wherein the graphene oxide is present in am amount of from 0.01 to. about 1.0 phr.

ί 5. A method of preparing reduced graphene oxide comprising:

a) adjusting the pH of a graphene oxide composition to between about S and 12;

b) adding to the pH adjusted graphene oxide composition at least one^'0 curing agent; and

e) mixing the graphene oxide composition by slow agitation at a temperature in the range of from about 20 °C to about 80 °C for time period in the range of about 4 to about 24 hours,

16, The method according to claim 15 wherein the pH adjuster is selected from s potassium ^'hydroxide, sodium hydroxide and ammonium hydroxide.

17, The method according to claim 16 wherein the pH adjuster is ammonium

hydroxide.

18, The method according to an one of claims 1 S to 17 wherein the pH adjuster is present in an amount of from 0.1 phr to 3,0 phr.

0 1 . The method according to any one of claims 15 to 18 wherein the at least one curing agent is selected from sulfur, at least one diihiocarbamaie, a ihiazole, zinc oxide or a mixture thereof

20, The method according to claim 19 wherein the dithioearbarnate is selected item zinc diethydiiMocar hamate and zinc dlbutyidithiocarbantate or a combination 5 thereof^*

21 , The method according to claim 19 and 20 wherein the thiazole is zinc 2- mefcaptobenzotbiazole,

22, The method according to any one of claims 15 to 2 wherein the caring agent is present in an amount -of from 0.1 phr to 3.0 phr,

0 23, The method according to any one of claims 15 to 22 further comprising a

stabilising agent.

24. The method according to claim 23 wherein the stabilizing agent i s a polymerized a!kyl naphthylene sulfonic acid.

25. The method according to claim.23 or claim 24 wherein the stabilizing agent is present: in an amount of from 0.1 phr to 2,0 phr,

26. A method of preparing a pelyisoprene latex graphene composite composition ¾ comprising:

a) preparing a composition of reduced graphene oxide according to any One of claims 15 to 25;

h) preparing a stabilized polyisopreiie latex composition by mixing

poiyisoprene latex with, at least one stabilizer under slow agitation for a time .t o period in the range of about 4 to about 24 hours; and

c) combining the reduced grapheme oxide composition of step a) with the stabilized poiyisoprene latex composition prepared in step b) and mixing.

27. The method according to claim 26 wherein the stabilizer is selected from a metal hydroxide and an anionic surfactant

!.¾ 28. The method according to claim 27 wherein the metal oxide is potassium

hydroxide.

29. The method according to claim 27 wherein the anionic surfactant is selected from sodium dodecyi sulfate and sodium .dodecyi benzene sulfonate.

30. The method according to any one of c laims 26 to 29 wherein the stabilizer is ao present in an amount of from OX) 1 phr to 5. phr,

31.. The method according to any one of claims 26 to 30 wherein th mixing at step c) occurs at room temperature under slow agitation.

32 , The method according to claim 31 wherein the compositio is mixed for a

period of time from about 8 to about 24 hours,

25 3, The method, according to claim 31 or claim 32 further comprising maturing, the composition.

34. The method according to claim 33 wherein maturation occurs at room

temperature over 1 to 13 days.

35. The method according to any one of claims 2 t 30 wherein the mixing at. step 30 c) occurs a a temperature of 40°C to ?§

36. The method according to claim 35 wherein the mixing occurs for a period of time of from about 8 to 24 hours. A method of preparing an e!astomeric article comprising.

a) preparing a polyisoprenc latex graphene composite composition by method according to any on of data 26 to 3 ;

b) dipping a Ibr er into the polyisoprene latex graphene eomposite composition to form an elastoffiertc film on the f rtner and

c) curing the elastoraerie film,

T¾e method / ccor ing to claim 3? wherein the elasteaerie article is selected .from a condom,, a glove, a pro.be cover or a catheter.

An elastonierie article prepared by the method, according of claim 37.

An elastooierie article according to claim 39 hich is a condom, a. love_* a probe cover or a catheter.

An elastorner!c article according to claim 40 which is a condom.

An elastonierie article according_: to any one of claims 39 tp 1 having interpartlcie crossllnking between reduced graphene oxide particles and the polyisoprene latex particles.