Polyurethane composites comprising nanocrystalline cellulose and method for improving properties of polyurethanes thereof

Abstract

A process for preparing polyurethane composites includes (i) providing a dispersion of nanocrystalline cellulose in (a) one or more polyols, (b) one or more isocyanates, or (c) one or more polyols and one or more isocyanate, mixed together; wherein the amount of water in the nanocrystalline cellulose is less than about 1% w/w; (ii) mixing the dispersion of (i)(a) with an isocyanate or (i)(b) with a polyol and a catalyst to allow polymerization; or mixing the dispersion of (i)(c) and a catalyst to allow polymerization; and (iii) isolating the polyurethane composite. A method for improving properties of polyurethanes includes dispersing nanocrystalline cellulose into one or both parts of a two part polyol/isocyanate precursors prior to allowing polymerization of the precursors, wherein the amount of water in the nanocrystalline cellulose is less than about 1% w/w; mixing the dispersion with a catalyst; and polymerizing the precursors to provide the polyurethane.

Claims

1. A process for preparing a polyurethane composite comprising: (i) providing a dispersion by (a) dispersing nanocrystalline cellulose into one or more polyols, (b) dispersing nanocrystalline cellulose into one or more isocyanates, or (c) dispersing nanocrystalline cellulose into one or more polyols and one or more isocyanates, separately or mixed together; (ii) mixing the dispersion of (a) with an isocyanate and a catalyst, mixing the dispersion of (b) with a polyol and a catalyst, or mixing the dispersion of (c) with a catalyst, to allow polymerization; and (iii) isolating said polyurethane composite, wherein the amount of water in said nanocrystalline cellulose is less than about 1% w/w.

2. The process of claim 1, wherein the isocyanate is an aromatic isocyanate.

3. The process of claim 1, wherein the isocyanate is an aliphatic isocyanate.

4. The process of claim 1, wherein the isocyanate is selected from the group consisting of a polymeric diphenylmethane diisocyanates, diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI); 1,6-hexamethylene diisocyanate (HDI), 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-cyclohexane (IPDI), 4,4′-diisocyanato dicyclohexylmethane; and a mixture thereof.

5. The process of claim 1, wherein the polyol for use in the process is comprising polyether polyols and polyester polyols.

6. The process of claim 1, wherein the catalysts is an amine compound or metal complex.

7. The process of claim 1, wherein the amount of nanocrystalline cellulose in said polyurethane composite is less than about 5% w/w.

8. The process of claim 1, wherein the amount of nanocrystalline cellulose in said polyurethane composite is less than about 1% w/w.

9. A method for modulating at least one property of a polyurethane, said method comprising: (i) providing a dispersion by (a) dispersing nanocrystalline cellulose into a polyol, (b) dispersing nanocrystalline cellulose into an isocyanate, or (c) dispersing nanocrystalline cellulose into a polyol and an isocyanate, (ii) mixing the dispersion of (a) with an isocyanate and a catalyst, mixing the dispersion of (b) with a polyol and a catalyst, or mixing the dispersion of (c) with a catalyst, to form a mixture; and (iii) polymerizing said mixture to provide said polyurethane, wherein the amount of water in said nanocrystalline cellulose is less than about 1% w/w.

10. The method of claim 9, wherein said property is one or more mechanical properties of the polyurethane selected from the group consisting of enhancement of elongation and tensile strength properties.

11. The method of claim 9 wherein said property is one or more mechanical properties selected from the group consisting of scratch resistance, abrasion resistance, hardness, impact resistance and a combination thereof.

12. The method of claim 9, wherein said polyurethane is a polyurethane which is used in elastomeric fibres, paints, solid polyurethane plastics thermoplastic and cast elastomers, adhesives and/or binders.

Description

EXAMPLE 1

Stability of Dispersion

(1) The first experiments determined the point at which a stable dispersed suspension of NCC in either the polyol or isocyanate phase could be achieved. With the particular polyol chosen, Table I shows that a stable suspension was obtained at a concentration of approximately 0.1% by weight in the polyol phase. The test used for this example was that dispersions were considered stable when there was no visible precipitation of NCC from the suspension. The dispersion is prepared by mixing at 800 rpm for 60 to 70 minutes in a planetary centrifugal mixer.

(2) TABLE-US-00001 TABLE I The stability of the NCC suspension over a 24 hour period at room temperature using Bayer Hyperlite E-824 Polyol, NCC, weight % weight % Stable over 24 hours 60 40 No 80 20 No 99 1 No 99.5 0.5 No 99.9 0.1 Yes

EXAMPLE 2

Elongation and Tensile Strength

(3) Table II shows that when dry NCC is added to the polyol phase that the resulting polyurethane has higher elongation and higher tensile strength than does the control without NCC but also when larger quantities of dry NCC are added into the polyol phase. The test that was used is ASTM D-638 . These results along with those in Table I indicate that it is important to form a suspension in the polyol where the nanoparticles are fully dispersed and not aggregated.

(4) TABLE-US-00002 TABLE II The increase in tensile strength and elongation in the formulation when NCC with 0% moisture is added to the polyol phase in Gyftane. NCC, Tensile strength, weight % Elongation, % psi 0 1160 1083 0.2 1218 1179 2 928 1024

(5) Table III shows the same results are obtained with a different polyol (Hyperlite E824) isocyanate (Mondur 445) combination. The choice of charges in this example shows that the advantage is again obtained at a low charge of NCC with the optimum in this case being at ˜0.1% when the NCC is added to the polyol phase.

(6) TABLE-US-00003 TABLE III The increase in tensile strength and elongation in the formulation when NCC with 0% moisture is added to the polyol phase. NCC, Tensile strength, weight % Elongation, % psi 0 175 149 0.05 205 165 0.09 280 225 0.185 252 203

EXAMPLE 3

Elongation and Tensile Strength

(7) Table IV shows that when dry NCC is added to the isocyanate phase that again the resulting polyurethane has higher elongation and higher tensile strength than does the control without NCC and again when larger quantities of dry NCC are added into the polyol phase. These results along with those in Table I indicate that it is important to form a suspension in the polyol where the nanoparticles are fully dispersed and not aggregated.

(8) TABLE-US-00004 TABLE IV The increase in tensile strength and elongation in the formulation when NCC with 0% moisture is added to the isocyanate phase (Gyftane). NCC, Tensile strength, weight % Elongation, % psi 0 1160 1083 0.2 1475 1349 0.5 1244 1193 2 1012 1027 4 1019 1016 10 1090 938

(9) Table V shows the same results are obtained with a different polyol (Hyperlite E824) isocyanate (Mondur 445) combination. The choice of charges in this example shows that the advantage is again obtained at a low charge of NCC with the optimum in this case being at ˜0.05 when the NCC is added to the isocyanate phase.

(10) TABLE-US-00005 TABLE V The increase in tensile strength and elongation in the formulation when NCC with 0% moisture is added to the isocyanate phase. NCC, Tensile strength, weight % Elongation, % psi 0 175 149 0.05 262 204 0.09 213 193 0.185 198 164

(11) This improvement that is obtained by adding dry NCC to the isocyanate phase over the polyol phase is directly shown in Tables VI and VII.

(12) TABLE-US-00006 TABLE VI Comparison of the effectiveness of adding NCC with 0% moisture to the isocyanate phase rather than the polyol phase. NCC, Tensile strength, weight % Elongation, % psi 0.2 (in isocyanate) 1475 1349 0.2 (in polyol) 1218 1179

(13) TABLE-US-00007 TABLE VII Comparison of the effectiveness of adding NCC with 0% moisture to the isocyanate phase rather than the polyol phase.* NCC, Tensile strength, weight % Elongation, % psi 0.05 (in isocyanate) 262 204 0.09 (in polyol) 280 225 *Polyol (Hyperlite E824)/isocyanate (Mondur 445) combination

(14) With the polyol—isocyanate combination in the example shown in Table VII, there is a different optimum NCC charge but the effectiveness per weight unit of NCC is greater when it was added to the isocyanate phase.

EXAMPLE 4

Elongation and Tensile Strength (5% Moisture)

(15) The importance of the removal of water is seen in Table VIII where there is significant variability and in general significant decreases in the physical strength parameters measured with this polyurethane formulation. In this example, the NCC was added to the isocyanate phase.

(16) TABLE-US-00008 TABLE VIII The limited effect of increasing the concentration of NCC in the formulation on tensile strength and elongation when the NCC has 5% moisture NCC, Tensile strength, weight % Elongation, % psi 0 1160 1083 0.5 1032 1248 2 811 933 5 1257 981

(17) While the disclosure has been described in connection with specific embodiments thereof, it is understood that it is capable of further modifications and that this application is intended to cover any variation, use, or adaptation of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure that come within known, or customary practice within the art to which the disclosure pertains and as may be applied to the essential features hereinbefore set forth, and as follows in the scope of the appended claims