Method of Producing A Product Formed from Cementitious Material

Abstract

A method of producing a product formed from cementitious material having an enhanced strength due to carbonation, comprises providing a polymeric carbonate composition, and mixing the polymeric carbon

Description

The present invention relates to a method of producing a product formed from cementitious material, such as concrete, mortar, cement paste, or grout, for example, having an enhanced strength due to carbonation, as well as a concrete product formed in accordance with the method. The main binder component of concrete is cement or cementitious material which typically constitutes around 10-15 wt% of the concrete. When the cementitious material hydrates, large quantities of calcium silicate hydrate materials are formed from, for instance, tricalcium silicate, dicalcium silicate, tricalcium aluminate, tetracalcium aluminoferrite, or gypsum. This forms the main binder element of the concrete. tricalcium silicate + water —> calcium silicate hydrate + calcium hydroxide + heat 2 CasSiOs + 7 H2O —> 3 CaO.2SiO2.4H2O + 3 Ca(OH)2 When water is added to the cementitious material, the tricalcium silicate rapidly reacts to release calcium ions, hydroxide ions, and a large amount of heat. The pH quickly rises, typically in excess of 12, due to the release of the hydroxide ions from the calcium hydroxide. This reaction continues slowly, producing calcium and hydroxide ions until the system becomes saturated. Once this occurs, the calcium hydroxide starts to crystallise. Simultaneously, calcium silicate hydrate begins to form, precipitating out of solution and accelerating the reaction of tricalcium silicate to calcium and hydroxide ions, in accordance with Le Chatelier's principle. The evolution of heat is then dramatically increased. The formation of the calcium hydroxide and calcium silicate hydrate crystals provide seeds upon which more calcium silicate hydrate can form. When cement is hydrated in the first stage, hydrolysis of the cement compounds occurs rapidly with a temperature increase of several degrees. This is typically within the first 15 minutes of curing. The second stage is known as the dormancy period. The evolution of heat slows dramatically in this stage. The dormancy period can last from one to three hours. During this period, the concrete is in a plastic state which allows the concrete to be transported and placed without any major difficulty. This is particularly important for the construction trade who must transport concrete to the job site. It is at the end of this stage that initial setting begins. In the third and fourth stages, the concrete starts to harden and the heat evolution increases due primarily to the hydration of tricalcium silicate. The fifth stage is reached after 36 hours. The slow formation of hydrate products occurs and continues as long as water and unhydrated silicates are present. Concrete-setting accelerators are designed designed to move the stage 3 and 4 of the curing process earlier, hence they do not change the overall final strength of concrete but rather achieve this strength more quickly. However, this actually negatively affects the strength of concrete as they rapidly consume the portlandite (calcium hydroxide) available in the cement. This leads to the CO2 to reacting immediately with the tricalcium silicate (C3A) and dicalcium silicate (C2A). This leads to the weakening of concrete due to the reaction affecting crystal and calcium silicate hydrate gel formation. The concrete can also be de-calcinated, in which calcium ions are consumed from the calcium silicate hydrates which weakens the final concrete. 2(3CaOSiO2) + 3CO2 + 3H2O - 3CaO-2SiO2-3H2O + 3CaCO3 2(2CaO SiO2) + CO2 + 3H2O 3CaO-2SiO2-3H2O + CaCO3 The present invention seeks to improve the strength of concrete products by control of the availability of CO2 during the curing stage. The same considerations apply for other cementitious materials as apply for concrete. According to a first aspect of the invention, there is provided a method of producing a product formed from cementitious material having an enhanced strength due to carbonation, the method comprising the steps of: a] providing a polymeric carbonate composition; b] mixing the polymeric carbonate composition with a freshly prepared cementitious material, wherein the polymeric carbonate composition is provided in an amount of 0.05-20.00wt.% of the cementitious material; and c] curing the cementitious material with aggregate material, wherein a duration of the curing step exceeds 24 hours, and more preferably exceeds 7 days. The present invention produces carbonate ions in cementitious conditions using a slow-release mode of action. It has been unexpectedly determined that overall strength of concrete or other cementitious products can be enhanced by slow release of carbonate into the mixture over an extended duration. This avoids the issues with curing accelerators which cause consumption of the portlandite early in the curing process which can reduce the strength of the resultant material. The use of polymeric carbonates which degrade over a period of many days has been shown to increase strength permanently. The polymeric carbonate composition may preferably be an aliphatic carbonate composition. More preferably, this applies to any aliphatic carbonate having up to seven carbon atoms, in addition to any applicable heteroatom content. Preferably, the polymeric carbonate composition may have the formula: Ri / 2= Alkyl derivative (uptoC5), carboxylic acid or other cross-linker where n >1. Optionally, the polymeric carbonate composition is any of: polypropylene carbonate; polyethylene carbonate; polycyclohexane carbonate; copolymers thereof; or a combination thereof. The polymeric carbonate composition may be a solid polymeric carbonate composition having a particle size in the range of 1pm to 1000pm. Modification of particle size alters the rate of degradation of the polymeric carbonate composition. Smaller particles seem to produce a greater overall increase in compressive strength when compared with ordinary Portland cement (OPC). This in turn allows for control of the curing time of the cementitious material for various different applications, while maintaining the mechanical and physical properties of the cementitious material in line with targeted species in the cementitious material for reaction with CO2. Other factors that affect the rate of degradation include molecular weight, formulation, end caps, intrinsic viscosity and CO2 content. The polymeric carbonate composition may be a solid polymeric carbonate composition having a particle size in the range of 10pm to 500pm, and more preferably in the range of 50pm to 250pm. In one preferred embodiment, the polymeric carbonate composition may be provided in powder form. In an alternative embodiment, the polymeric carbonate composition may be provided in fibre form. The use of solid polymeric additions can be mixed into cement having a size similar to the grains in the cement mixture itself, and therefore may be more straightforward to disperse through a cement mixture. In an alternative embodiment, the polymeric carbonate composition may be encapsulated or coated by a protective degradable layer. The encapsulation reduces the rate of polymeric decomposition and availability of the carbonate ions to carbonate cementitious materials. The encapsulation methods used may include but are not limited to spray drying, fluidised bed coating, pan coating, coacervation, extrusion, in-situ polymerisation, melt encapsulation, spray chilling / solidification and physical vapour decomposition, such as plasma and / or polymer evaporation. The coatings include but are not limited to: poly(lactic acid) (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), polyhydroxybutyrate (PHB), poly(lactic-co-glycolic acid) (PLGA), cellulose acetate (CA), hyaluronic acid (HA), poly(ethylene glycol) (PEG), polyanhydrides, chitosan, fluoropolymers, silicone polymers, cyclic polyolefins, polyarylene ethers, highly cross-linked polymers, phosphonated polymers and silane-based polymers. Alternatively, the polymeric carbonate composition may be provided as a liquid solution. Liquid dispersions may advantageously be an easier way of storing and metering the polymeric carbonate composition for mixing into cement materials without adversely affecting the curing properties. Optionally, the polymeric carbonate composition may have a molecular weight of between 0.1-1000kDa. More preferably, the polymeric carbonate composition may have a molecular weight of between 1-500kDa. The polymeric carbonate composition may comprise 0.05% to 10.00wt% of the cementitious material. During step c], the curing may occur in a chamber, bath, open conditions or any other standard curing techniques used by the concrete industry at 30- 90% relative humidity. Preferably, during step c], the duration of the curing step may exceed 14 days. Optionally, the cementitious material is a concrete binder mixture which may comprise any of: cement, limestone, supplementary cementitious material, sand, aggregate, water, and one or more admixtures. Preferably, the polymeric carbonate composition may release between 20-60% by mass of carbonate during the curing step c]. Advantageously, the polymeric carbonate composition may release not more than 5% by mass of carbonate during the first 24 hours of the curing step c]. Limited release of carbonate release during the initial stages of curing enables the slow strengthening process of the present invention to be achieved. Optionally the polymeric carbonate composition may release between 5-10% by mass of carbonate during the first 7 days of the curing step c]. Preferably, the polymeric carbonate composition may release not more than 95% by mass of carbonate during the first 28 days of the curing step c]. During step c], decomposition conditions of the polymeric carbonate composition may be selected to achieve a preferred CO2 release rate. Optionally, the decomposition conditions may include at least one of: temperature; humidity; particle size of the polymeric carbonate composition. Optionally, the predetermined amount of carbon dioxide may be up to 20% carbon dioxide relative to a weight of cement binder in the concrete-carrier mix within 24 to 1344 hours to increase the compressive strength of the concrete material by between 20 and 100%. Optionally, the compressive strength of the concrete material is increased by between 20 and 100%. Preferably, the predetermined amount of carbon dioxide may be 1 - 3% carbon dioxide relative to a weight of cement binder in the concrete-carrier mix within 24 to 1344 hours to increase the compressive strength of the concrete material by between 5 and 25%. Optionally, the compressive strength of the concrete material is increased by between 5 and 25%. Alternatively, a weight of binder in the concrete-carrier mix may be reduced by between 2 and 50% relative to a standard concrete mix. Alternatively, a weight of binder in the concrete-carrier mix may be reduced by between 5 and 35% relative to a standard concrete mix. Alternatively, a weight of binder in the concrete-carrier mix may be reduced by between 5 and 20% relative to a standard concrete mix. A standard concrete mix would usually include binder, such as cement, in a weight of 10 to 20% of the weight of the concrete mix. Optionally, the carbon dioxide decomposition / release rate of the carrier may be in the range of 0.043 to 0.1454 mmol / g / h. Optionally, the carbon dioxide decomposition / release rate of the modified carrier may be in the range of 0.0145 to 0.0582 mmol / g / h. Preferably, the carbon dioxide decomposition / release rate of the modified carrier may be in the range of 0.0016 to 0.0290 mmol / g / h. Preferably, the carbon dioxide decomposition / release rate of the modified carrier may be in the range of 0.0016 to 0.0145 mmol / g / h. Optionally, a rate of carbon dioxide uptake in the concrete material may be less than 0.0014 mmol / g / h, by the weight of concrete reactive material agent from the binder of the concrete mix. Preferably, the carrier may comprise of carbon dioxide is selected so as to release a predetermined amount of carbon dioxide during the curing process over a predetermined time period, to thereby achieve a desired increase in compressive strength and / or carbonation of the concrete material. Preferably, the predetermined amount of carbon dioxide may be a percentage by weight of carbon dioxide relative to a weight of cement in the concrete-carrier mix. It is desirable to specifically modify the carrier being used, within the present invention, to achieve specific advantageous properties of the concrete that is subsequently formed. The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a graph identifying the decomposition extent of a polymeric carbonate composition used in a method in accordance with the first aspect of the invention over time for polyethylene carbonate having a particular size ~200pm and having a molecular weight of 183kDa, where the decomposition extent is equivalent to CO2 release based on the decomposition mechanism, and as measured by monitoring the total release of propylene glycol by 1H NMR; and Figure 2 shows a graph comparing the decomposition extents of four polymeric carbonate compositions formed polyethylene carbonate (solid line), polypropylene carbonate (dotted line), polypropylene carbonate / polycyclohexane carbonate copolymer (long dashed line), and polycyclohexane carbonate (short dashed line). The present invention is directed towards the controlled, slow release of CO2 in a concrete mixture during the curing or setting process, so as to improve the strength of the finished concrete product by carbonation. Whilst reference is made to a concrete product, the disclosure applies equally to other products formed from cementitious materials. This is achieved by the use of polymeric decomposition materials that degrade to release CO2 for the carbonation reaction. Polymeric carbonate compositions are used, preferably aliphatic polycarbonates, and more preferably having the following structure: B Ri / 2= Alkyl derivative (uptoC5), carboxylic acid or other cross-linker where n >1. The polymers may be comprised of repeating units of a single or multiple monomeric species to form the carbonate. Figure 1 shows an exemplary graph of decomposition rate over time for polyethylene carbonate. Such polymers may be produced through copolymerisation with one or more aliphatic diols, such as propylene glycol, 1,2-cyclohexane-diol, ethylene glycol, and CO2. Desirable features of the polymer include: water insolubility; one or combination therof polymers and co-polymers where the polymer decompose to provide CO2 that can carbonate the cementitious phase of concrete; measurable degradation in an alkaline environment such as cement over a period of 28 days, preferably of at least 20 wt%, to release carbonate ions and the respective diol; measurable degradation in an alkaline environment such as cement over a period of 24 hours of less than 10 wt%; particle size or fibre diameter in the range of 1pm to 1000pm, more preferably 10pm to 500pm, and most preferably 125pm to 250pm; and / or a molecular weight in the range of 0.1 kDa to 1000kDa, and more preferably 1kDa to 500kDa. The mode of release of carbonate ions is as illustrated below, with decomposition occurring in alkaline conditions. The carbonate results in production of carbonated mineral phases within the cementitious material which persist throughout its lifetime and thus improve the strength of the concrete product formed. The polymer structures may be purely homo-polymeric (e.g., AAAAAA structure) or as an alternating (e.g., ABABAB) or block (e.g., AAAABBBB) copolymer. There is a relationship between hydrophilicity of the monomeric species and hydrolysis rates in alkaline environments. For instance, a copolymer of polypropylene and polycyclohexane carbonate results in an approximately four times slower hydrolysis rate in solution compared with the homo-polymeric equivalents. Different degradation rates are preferred for different cementitious materials, and therefore it is desirable to select the characteristics of the polymeric carbonate composition prior to use. For instance, different base monomers may be used to alter degradation rates, as may different particle or fibre sizes of the polymeric carbonate composition. For instance, CO2 release rates are attuned through the incorporation of other monomeric units into the polymeric structure, including C2-C8 cyclic and linear hydrocarbons and those containing other functional groups or by co-processing individual copolymers of the aliphatic carbonate family together through extrusion, blending or milling. Figure 2 shows examples of how degradation rate can be altered by using different copolymers. Four copolymer carbonates are shown, indicating the rates of decomposition with respect to pure polypropylene carbonate. Polyethlene carbonate (183 kDa) - solid black line, Polypropylene carbonate (190 kDa) - dotted black line, Polycyclohexene carbonate / polypropylene carbonate copolymer (162 kDa) - long dashed line, Polycyclohexene carbonate (152 kDa) - short dashed line. Different criteria may apply depending on whether the polymeric carbonate composition is provided in solid form, such as a powder or fibre, or whether it is provided as a liquid dispersion in a solvent such as a glycol solvent, including but not limited to propylene glycol, ethylene glycol, or polyethylene glycol. Where powders or fibres are used, effective dispersal of the polymeric carbonate composition in ready-mix cement powder may be achievable by maintaining a particle size or particle diameter within the range of cement grain sizes, typically 1-100pm. Dispersal agents such as bentonite can be used to create a more stable mixture. Where liquid dispersions are used, the polymeric carbonate composition will immediately precipitate out of solution upon addition to cement, and therefore the liquid dispersion may be a more convenient means of storing the polymeric carbonate composition. Solvents of, for example, polypropylene carbonate can be used in cement without significant negative effect, in addition to superplasticisers such as polyethers, whilst still remaining insoluble or substantially insoluble in water. Examples Example 1 Polypropylene carbonate (Mn ~ 55kDa, Mw = 240kDa) was provided in pellet form and ground to a powder having a particle size dispersion of 0.2mm average diameter. Thermogravimetric Analysis (TGA), Fourier Transform IR spectroscopy (FTIR), and Gas Phase Chromatography (GPC) were used to inspect the molecular weight post-grinding, which was found to have reduced by approximately 5%. The polypropylene carbonate was mixed with cement binder in a ratio of 1-5wt% containing a water / cement ratio (w / c) of 0.4:1, and was then cast into cubes of concrete for evaluation of compressive strengths of the binder material and chemical analysis. The cubes were demoulded after 1 day, and then measurements taken at 7 days, and 28 days. Concrete blocks made in this manner were found to have a 10-25% increase in compressive strength compared with a mixture containing ordinary Portland cement (OPC) only. The additional CO2 content, as measured by TGA-FTIR and X-ray diffraction, was 1.7wt.% after 7 days in the form of non-crystalline calcium carbonates, and 5wt.% in the form of calcite after 28 days, dependent on formulation. Example 2 Polypropylene carbonate (Mn ~ 55kDa, Mw = 240kDa) was provided in pellet form and ground to a powder having a particle size dispersion of 0.1mm average diameter. Thermogravimetric Analysis (TGA), Fourier Transform IR spectroscopy (FTIR), and Gas Phase Chromatography (GPC) were used to inspect the molecular weight post-grinding, which was found to have reduced by approximately 5%. The polypropylene carbonate was mixed with cement binder in a ratio of 1-5wt.% containing a water / cement ratio (w / c) of 0.4:1, and was then cast into cubes of concrete for evaluation of compressive strengths of the binder material and chemical analysis. The cubes were demoulded after 1 day, and then measurements taken at 7 days, and 28 days. Concrete blocks made in this manner were found to have a 10-30% increase in compressive strength compared with a mixture containing ordinary Portland cement (OPC) only. The additional CO2 content, as measured by TGA-FTIR and X-ray diffraction, was 1wt.% after 7 days in the form of non-crystalline calcium carbonates, and 4.5wt.% in the form of calcite after 28 days, dependent on formulation. Example 3 Polypropylene carbonate (Mn ~ 55kDa, Mw = 240kDa) was provided in pellet form and ground to a powder having a particle size dispersion of 0.5mm average diameter. Thermogravimetric Analysis (TGA), Fourier Transform IR spectroscopy (FTIR), and Gas Phase Chromatography (GPC) were used to inspect the molecular weight post-grinding, which was found to have reduced by approximately 5%. The polypropylene carbonate was mixed with cement binder in a ratio of 2wt.% containing a water / cement ratio (w / c) of 0.4:1, and was then cast into cubes of concrete for evaluation of compressive strengths of the binder material and chemical analysis. The cubes were demoulded after 1 day, and then measurements taken at 7 days, and 28 days. Concrete blocks made in this manner were found to have a 5-15% increase in compressive strength compared with a mixture containing ordinary Portland cement (OPC) only. The additional CO2 content, as measured by TGA-FTIR and X-ray diffraction, was 0.2wt.% after 7 days in the form of non-crystalline calcium carbonates, and 2wt.% in the form of calcite after 28 days, dependent on formulation. Example 4 Polypropylene carbonate (Mn ~ 55kDa, Mw = 240kDa) was provided in pellet form and dissolved in polyethylene glycol at60wt.% polypropylene carbonate. The solution was mixed with a mortar mix in a polypropylene carbonate to cement ratio of 0.05:1 and containing 12% Portland cement, containing a water / cement ratio (w / c) of 0.4:1, under consistent mixing conditions. The polypropylene carbonate precipitated into particles of 10-80pm. The mixture was then cast into cubes of concrete for evaluation of compressive strengths of the binder material and samples of cement paste were retained for chemical analysis, the cement paste samples containing the same ratio of superplasticiser to polypropylene carbonate. Following 28-day curing time, final strengths of the concrete blocks were found to be 16% stronger, in comparison to reference blocks containing only standard superplasticizer. Chemical analysis demonstrated additional 2.3wt.% of CO2 retained as Calcite within the cement paste binder samples with respect to a comparative reference. Example 5 Polypropylene carbonate (Mn ~ 5kDa, Mw = 240kDa) was provided in pellet form and dissolved in propylene glycol at 70wt.% polypropylene carbonate. The solution was mixed with a mortar mix in a polypropylene carbonate to cement ratio of 0.05:1 and containing 12% Portland cement, containing a water / cement ratio (w / c) of 0.4:1, under consistent mixing conditions. The polypropylene carbonate precipitated into particles of 10-80pm. The mixture was then cast into cubes of concrete for evaluation of compressive strengths of the binder material and samples of cement paste were retained for chemical analysis, the cement paste samples containing the same ratio of superplasticiser to polypropylene carbonate. Following 28-day curing time, final strengths of the concrete blocks were found to be 10-18% stronger, in comparison to reference blocks containing only standard superplasticizer. Chemical analysis demonstrated additional 3.8wt.% of CO2 retained as Calcite within the cement paste binder samples with respect to a comparative reference. Whilst the polymeric carbonate composition is described as being added in powder or solution forms to a cement mixture, it will be possible to deposit the polymeric carbonate composition onto a supplementary cementitious material, such as a pozzolan, which will allow for effective storage and delivery of the CO2 releasing agent. It is therefore possible to provide a method of producing a concrete product having an enhanced strength due to carbonation is provided. The method comprises the steps of providing a polymeric carbonate composition, and mixing the polymeric carbonate composition with a freshly prepared concrete binder mixture. The polymeric carbonate composition is provided in an amount of 0.05-20.00wt.% of the concrete binder mixture. The concrete binder mixture is then cured with aggregate material, wherein a duration of the curing step exceeds 7 days for slow release of CO2 into the concrete product and improve strength. The words ‘comprises / comprising’ and the words ‘having / including’ when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps, or components, but do not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. The embodiments described above are provided by way of examples only, and various other modifications will be apparent to persons skilled in the field without departing from the scope of the invention as defined herein.

Claims

1. A method of producing a product formed from cementitious material having an enhanced strength due to carbonation, the method comprising the steps of:a] providing a polymeric carbonate composition;b] mixing the polymeric carbonate composition with a freshly prepared cementitious material , wherein the polymeric carbonate composition is provided in an amount of 0.05-20.00wt.% of the cementitious material; andc] curing the cementitious material with aggregate material, wherein a duration of the curing step exceeds 24 hours.

2. A method as claimed in claim 1, wherein the polymeric carbonate composition is an aliphatic carbonate composition.

3. A method as claimed in claim 1 or claim 2, wherein the polymeric carbonatecomposition has the formula:A BRi / 2= Alkyl derivative (uptoC5), carboxylic acid or other cross-linkerwhere n >1.

4. A method as claimed in any one of the preceding claims, wherein the polymeric carbonate composition is any of: polypropylene carbonate; polyethylene carbonate; polycyclohexane carbonate; copolymers thereof; or a combination thereof.

5. A method as claimed in any one of the preceding claims, wherein the polymeric carbonate composition is a solid polymeric carbonate composition having a particle size in the range of 1pm to 1000pm.

6. A method as claimed in claim 5, wherein the polymeric carbonate composition is a solid polymeric carbonate composition having a particle size in the range of 20pm to 500pm.

7. A method as claimed in claim 6, wherein the polymeric carbonate composition is a solid polymeric carbonate composition having a particle size in the range of 50pm to 250pm.

8. A method as claimed in any one of claims 5 to 7, wherein the polymeric carbonate composition is provided in powder form.

9. A method as claimed in any one of claims 5 to 7, wherein the polymeric carbonate composition is provided in fibre form.

10. A method as claimed in any one of the preceding claims, wherein the polymeric carbonate composition is encapsulated or coated by a protective degradable layer.

11. A method as claimed in any one of claims 1 to 4, wherein the polymeric carbonate composition is provided as a liquid solution.

12. A method as claimed in any one of the preceding claims, wherein the polymeric carbonate composition has a molecular weight of between 0.1-1000kDa.

13. A method as claimed in claim 11, wherein the polymeric carbonate composition has a molecular weight of between 1-500kDa.

14. A method as claimed in any one of the preceding claims, wherein the polymeric carbonate composition comprises 0.05% to 10.00wt% of the cementitious material.

15. A method as claimed in any one of the preceding claims, wherein during step c], the curing occurs in a chamber, bath, open conditions or any other standard curing techniques used by the concrete industry at 30-90% relative humidity.

16. A method as claimed in any one of the preceding claims, wherein during step c], the duration of the curing step exceeds 14 days.

17. A method as claimed in any one of the preceding claims, wherein the cementitious material is a concrete binder mixture which comprises any of: cement, supplementary cementitious material, limestone, sand, aggregate, water, and one or more admixtures.

18. A method as claimed in any one of the preceding claims, wherein the polymeric carbonate composition releases between 20-60% by mass of carbonate during the curing step c],19. A method as claimed in any one of the preceding claims, wherein the polymeric carbonate composition releases not more than 10% by mass of carbonate during the first 8 hours of the curing step c],20. A method as claimed in any one of the preceding claims, wherein the polymeric carbonate composition releases between 5-50% by mass of carbonate during the first 7 days of the curing step c],21. A method as claimed in any one of the preceding claims, wherein the polymeric carbonate composition releases not more than 95% by mass of carbonate during the first 28 days of the curing step c],22. A method as claimed in any one of the preceding claims, wherein during step c], decomposition conditions of the polymeric carbonate composition are selected to achieve a preferred curing condition.

23. A method as claimed in claim 22, wherein the decomposition conditions include at least one of: temperature; humidity; particle size of the polymeric carbonate composition.

Images