Compact compound comprising silanized hydroxyl graphene with thermosetting polymer

Abstract

The present invention relates a compact compound and their preparation and more particularly to such compact compound prepared from hydroxyl graphene functionalized and combinations with thermosetting polymer with particular particles of specified size, shape and properties. The present invention relates generally to field of nanomaterials and preparation of nanomaterials as well as use of nanomaterials in architecture, engineering and interior design.

Claims

1. A compact compound comprising: a) hydroxyl graphene functionalized with silane; b) a thermosetting polymer; wherein the percentage of hydroxylation in the graphene unfunctionalized is between 90% and 100% by the presence of the singlet at 533.4 eV as measured by XPS; and wherein the amount of the thermosetting polymer is between 40% and 99% in weight with respect the compact compound.

2. The compact compound according to claim 1, wherein the hydroxyl graphene is monolayer or multilayer.

3. The compact compound according to claim 1, wherein the thermosetting polymer is selected from bis-phenol-A glycidyl ether, novalic glycidil ethers, aliphatic glycidyl ethers, hydantoin glycidyl ethers, cycloaliphatic epoxides and brominated modifications of thereof, epoxy acrylate resin, orthophtalic polyester resin, isophtalic polyester resin, polyether polyols, and polyalkylene glycols.

4. The compact compound according to claim 1, wherein the silane is 3-methacryl oxypropyl-trimethoxysilane.

5. The compact compound according to claim 1, wherein further comprising a reinforcement material selected from silica, quartz, glass, clay, aluminium, alumina trihydrate, cristobalite, carbon fiber, glass fiber woven sheets and any combination thereof, and wherein the reinforcement material average size is between 1 nm and 5000 μm.

6. The compact compound according to claim 1, wherein further comprising a fire-retardant additive selected from ATH, ammonium polyphosphate, magnesium hydroxide, Magnesium aluminum-layered double hydroxide (LDH), LDH carbonate, d-LDH, aluminium diethyl phosphinat and melamine polyphosphate.

7. The compact compound according to claim 1, further comprising a pigment with an average size of between 1 nm and 5000 μm and selected from: metal oxides, wherein the metal is selected from aluminium, iron, copper, titanium, manganese, cobalt, cadmium, zinc and any combination thereof; metal salt, wherein the metal is selected from aluminium, iron, copper, titanium, manganese, cobalt, cadmium, zinc and any combination thereof; and any combination thereof.

8. A method for obtainment the compact compound according to claim 1 comprising the following steps: a) Obtaining the hydroxyl graphene from graphite, wherein the percentage of hydroxylation in the graphene is between 90% and 100% by the presence of the singlet at 533.4 eV as measured by XPS; b) Silanization of the hydroxylate graphene obtained in step (a) with sonication and mechanical agitation; c) Dispersing the precursor of the thermosetting polymer into the silane-functionalized hydroxylate graphene obtained in step (b) by mechanical agitation and sonication, and polymerizing; and d) Curing by thermal treatment of the product obtained in step (c).

9. The method according to claim 8, wherein the obtainment of the hydroxyl graphene of step (a) is performed by following the following steps: a1) mixing an amount of between 99 g and 101 g of graphite, and amount of between 8 g and 12 g of 2M NaOH in a volume of between 250 mL and 350mL of H.sub.2SO.sub.4 98%, and adding an amount of between 70 g and 90 g of KMnO.sub.4 to the mixture at a temperature of between 1° C. and 10° C. with stirring for a time of between 30 min and 40 min, a2) injecting the mixture obtained in step (a1) in a Couette—Taylor flow reactor, and mixing for a time period of between 1 h and 1,2 h at a rotating speed of the inner cylinder between 900-1100 rpm, a3) 400-450 ml of purified water and 90-100 ml of peroxide, H.sub.2O.sub.2 30%, is added to the mixture obtained in step (a2), and then stirred for 45-50 min, and precipitating out the non- or under-hydroxilated graphitic particles by further centrifugation at 4000 rpm for 30 min; a4) purifying the slurry obtained in the step (a3) for a period time of between 1 h and 3 h by centrifugation at a revolution of between 3700 rpm and 4200 rpm for a time of between and filtering the particles formed after centrifugation by press filter, wherein distilled water is continually fed into the reactor; and a5) dispersing in water the remaining solid obtained in step (a4) and filtering in a membrane with a pore of 1 μm or less, and drying the recovered solid after filtration.

10. The method according to claim 8, wherein the obtainment of the hydroxyl graphene functionalized with silane of step (b) is performed by the following steps: b1) hydrolysing an organosilane in a water solution b2) adding progressively the dry hydroxyl graphene obtained in step (a) into the water solution obtained in step (b1) maintain the magnetic agitation for at least 15 min., b3) sonicating the mixture obtained in the step (b2) for a period of time of between 30 min and 60 min with a frequency of between 20 kHz and 40 kHz; and b4) drying the solid obtained in step (b3) at a temperature of between 100° C. and 150° C. for a period of time of between 4 h and 6 h.

11. The method according to claim 8, wherein step (c) is performed by the following steps: c1) dispersing the precursor material of the thermosetting polymer for at least 15 min on the hydroxylate graphene functionalized with silane obtained in step (b) under magnetic vibration; c2) adding an initiating polymerization agent and a catalytic drier into the mixture obtained in step (c1) stirring for at least 2 min at a temperature of between 30° C. and 50° c; and c3) sonicating the mixture obtained in the step (c2) for a period of time of between 30 min and 60 min with a frequency of between 20 kHz and 40 kHz.

12. The method according to any of claim 8, wherein the curing of step (d) is performed at a temperature of between 15° C. and 25° C. for a time period of between 20 h and 28 h.

13. The method according to claim 12, wherein an additional post cured is performed at a temperature of between 55° C. and 75° C. for a time period of between 3 h and 6 h.

14. An overcoat painting comprising the compact compound of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1. Raman spectrums of G-OH and f-G-OH of samples.

(2) FIG. 2. SEM images showing the functionalized graphene coated with the polymer.

(3) FIG. 3. SEM images of graphene sheets and polymer lamellas intermingled.

(4) FIG. 4. SEM images of a graphene crystal without functionalization shows not adherence to the matrix polymer.

(5) FIG. 5. SEM images of a graphene crystal adhered to the polymer matrix.

(6) FIG. 6. EDX spectrum in the adherence zone

(7) FIG. 7. SEM images of the nanocomposite showing few layers graphene sheets linked with the polymer matrix.

(8) FIG. 8. SEM image showing the functionalized graphene coated with the polymer before UV treatment,

(9) FIG. 9. SEM image showing the functionalized graphene coated with the polymer after UV treatment.

EXAMPLES

Example 1

(10) Obtaining of the Hydroxylate Graphene.

(11) Graphite flakes were processed using a Couette-Taylor flow reactor. In an embodiment, 100 g of graphite flakes and 10 g of 2M NaOH were added to 300 ml of sulfuric acid (H.sub.2SO.sub.4 98%). Then, 80 g of potassium permanganate (KMnO4) was slowly added to this mixture at 10° C. or lower and the mixture was stirred for 30 min. The mixture was injected into the flow reactor. The rotating speed of the inner cylinder was 1000 rpm during 60 min to obtain a brown-colored pasty slurry. For a workup, 400 ml of purified water and 100 ml of peroxide, H.sub.2O.sub.2 30%, were added to the mixture, and then stirred for 45 min. For purification, a filter press system was used to separate hydroxylate graphene (G-OH) and impurities. Then, non- or under-hydroxilated graphitic particles were precipitated out by further centrifugation at 4000 rpm for 30 min. G-OH slurry and a large volume of distilled water was continually fed into the system until the water and impurities is squeezed out. The purification step was done for 2 h. The remaining G-OH solids were collected and dispersed in water. The supernatant containing single- or few-layer G-O was filtered over a PTFE membrane with a 1 μm pore size and vacuum- or freeze-dried for characterization.

(12) Elemental analysis, size and number of layers was characterized by X-ray diffraction (XRD) using a powder diffractometer D4 Endeavor, Bruker-AXS with Bragg-Brentano θ/2θ geometry with Cu X ray tubes, Raman spectrum with the NRS-3100 (Jasco), and surface area analyzer Gemini V (Micrometrics), and Leica-Zeiss LEO 440 scanning electron microscope (SEM). Results confirmed the exclusive formation of C—OH groups in G-OH due to the hydroxylation process performed. Table 1 shows the elements average values in atomic percentage:

(13) TABLE-US-00001 TABLE 1 Elemental analysis Element Atomic fraction % C 79.8 H 9.8 O 9.8 Others <0.4

Example 2

(14) Silanization of the Hydroxylate Graphene

(15) Firstly, the organosilane 3-methacryl oxypropyl-trimethoxysilane (MEMO) obtained from Dynasilan was hydrolysed in a water solution in acid environment through the addition of between 0.05 ml and 0.015 ml HCl 33% to achieve pH=1. In this case, 3 g of MEMO was dispersed in 150 ml of distilled water and 1-4 drops of HCl 33% are added. The aqueous solution is agitated during 10 minutes. Next, 150 g of G-OH were added progressively maintain the magnetic agitation during 15 minutes. Then, the combination was realized through a 30 minutes process of sonication (with 20 kHz frequency) maintaining the mixture in vibration. Said 30 minutes process are achieved by following fifteen times alternation of 2 minutes cycles of operation and shutdown.

(16) After silane hydrolisis and bonding with the hydroxil graphene (G-OH), a nanohybrid silane functionalizated graphene (f-G-OH) of size 20-30 nm is obtained.

(17) The resulting functionalized G-OH (f-G-OH) with silane was dried at 125° C. during 5 hours. The FIG. 1 shows the Raman spectrums of the G-OH the f-G-OH. The characteristic D-Band (between 1321-1322 cm.sup.−1) and G-band (between 1565-1571 cm.sup.−1) of graphene are visible in both samples. The shift in the position and intensity of the peaks provides insights into the effect of silanization. The presence of Si—O—Si and Si—O—C bands at 1144 and 1113 cm.sup.−1 confirms the presence of MEMO showing the inter-linkages occurring between the Si—O and C of graphene.

Example 3

(18) Synthesis of the Thermosetting Polymer with the Silane-Functionalized Hydroxyl Graphene (f-G-OH) with Different Wt % of the (f-G-OH) Used.

(19) To prepare the composite at different wt % (f-G-OH), polyester resin (ISO-NPG provided by SUMARCOP,) was bonded with functionalized G-OH (f-G-OH) according to the table 2 to obtain samples with different percentage of the silanizated G-OH relative to the polymeric resin.

(20) TABLE-US-00002 TABLE 2 Examples prepared Resine f-G-OH f-G-OH pMEK Co-Octo sample (g) (g) % (g) (ml) 1 130 0  0% 2.6 0 2 130 1.3  1% 2.6 0 3 130 13 10% 2.6 0 4 130 26 20% 2.6 0 5 130 39 30% 2.6 0.3 6 130 52 40% 2.6 0.5 7 130 59 45% 2.6 3.5 8 130 65 50% 2.6 5

(21) The resin was dispersed progressively during 15 minutes under magnetic vibration. To initiate the polymerization reactions, methyl ethyl ketone (pMEK type K1 from AKZO) and 1-5 wt % of Cobalt Octoate 6% are added (depending on the G-OH proportion), and stirred during 2 minutes at 40° C. The combination was sonicated during 30 minutes (with 20 kHz frequency) maintaining the mixture in vibration. Said 30 minutes process are achieved by following fifteen times alternation of 2 minutes cycles of operation and shutdown, and maintaining the temperature controlled.

(22) After curing for 24 hours at 20° C., each composite sample is post cured during 4 hours at 65° C. in order to increase the polymer vitrification and to obtain the resulting nanocomposite.

Example 4

(23) Nanocomposite microstructure characterization of the samples obtained in example 3. To characterize the resulting microstructure, several samples fractured after tensile tests were analysed with SEM. The microstructure is characterized by the presence of graphene sheets and graphene crystal bonded with the polymer through the silica bridges.

(24) As a consequence of the degree of dispersion achieved, the graphene sheets are well distributed throughout the polymer matrix as can be observed in FIG. 2. Image in FIG. 2 shows that the f-G-OH is well coated with the polymer making the bonds even stronger which also contribute to improve the physical-mechanical properties of the composite. Moreover, the composite also shows clear and good dispersion between all of the particles.

(25) Also, the SEM analysis shows that the polyester and graphene sheets are intermingled. FIG. 3 shows some large few layers graphene sheets (A) and polymer lamellas (B) adhered to them.

(26) The presence of amorphous silica (from silane) crystals confirms its contribution within the composite as a functionalization moiety, thus resulting in successful functionalization of particles within the polymer matrix layers. Images in FIG. 4 shows a graphene crystal in one sample without silane functionalization. It can be observed as the graphene crystal rest on the polymer matrix without adherence. In contrast, in FIG. 5 it can be observed that a crystal of similar size of f-G-OH is clearly bonded to the polymer matrix.

(27) The presence of silica moieties along with graphene showed the presence of dangling bonds resulted in the capture/attraction of silane particles, thereby resulting in the formation of continuous linkages. These linkages provide higher adhesion between the layers, making the composite stronger.

(28) The SEM analysis also shows the presence of exfoliated sheets with a vertical height of 3-4 nm and stacks of just 3-6 layers (FIG. 6).

Example 5

(29) Tensile Tests of the Thermosetting Polymer with the Silane-Functionalized Hydroxylate Graphene.

(30) Tensile tests of the composite of unsaturated polyester with silanizated hydroxyl graphene were performed using a universal testing machine (UTM) (Instron 8841, Norwood, Mass., USA). At least five specimens were tested for each case to ensure the reliability of the test results. The tensile strength, modulus and elongation at break of each sample were measured. Specimens of 3 mm thick and 20 mm in width were prepared for the test. The initial gauge length and cross-head speed was set at 50 mm and 0.5 mm/min, respectively. It was found that the resisting properties of the resulting compound were noticeably higher than the unsaturated polyester resin (table 3).

(31) TABLE-US-00003 TABLE 3 Tensile strenght Sample σ max (Mpa) 1 50.7 2 60.9 3 62.6 4 65.3 5 65.6 6 66.2 7 67.0 8 67.3

(32) Results showed significant improvement due to the dispersion (arriving up to 50% of graphene wt %) and the interfacial interactions between the nanohybrid and the polymer composite arising from the covalent bonding between the functionalized graphene and the polymer matrix. Table 3 shows improvement of the tensile strength up to 33% over the raw unsaturated polyester sample (sample 1). Furthermore, the toughness of the new composite was increased between 1.7 and 2-times that of the unmodified case. These results show that silane functionalization groups offer increased interfacial reactivity between G-OH and matrix.

Example 6

(33) Blackness after UV Radiation of the Thermosetting Polymer with the Silane-Functionalized Hydroxyl Graphene.

(34) The samples were subject to a UV doses of 9500 MJ/cm2 during seven days (168 hours) using a UV Xenon lamp in the spectral regime around 365 nm and power density 80-120 W/cm. The original and UV-irradiated samples were measured four times, using a SP60 sphere spectophotomer X-rite (D65/10), and averaged to obtain final colorimetric data. The chromatic information for some of the samples is given in the table 4. The data include a black solid surface considered as best practice technology (Δh) (benchmark) for comparison purposes.

(35) TABLE-US-00004 TABLE 4 Spectophotometric results (CIE 1976 L*a*b*) sample L* a* b* h* C* Δh* benchmark 28.53 −1.04 −1.24 −2.44 1.62   14% benchmark UV 28.76 −0.71 −1.92 −2.79 2.05 sample 2 28.56   0.20   0.29   0.60 0.35 −90% sample 2 after UV 29.93   0.04   0.69   0.06 0.69 sample 5 31.23   0.24   0.31   0.66 0.39 −51% sample 5 after UV 34.39   0.13   0.39   0.32 0.41

(36) Surface degradation is a common problem in polymeric composites when they are exposed to sunlight, altering its mechanical and aesthetical properties. Ultraviolet (UV) radiation is an efficient catalyst of organic polymer decomposition generating mass loses and generating colour modifications such as yellowing or whitening as a function of UV exposure time. Several studies show that the perception of blackness depend basically on the hue (h*), when comparing different black objects. A hue (h*) value of cero is associated with the more blackness object.

(37) With the state of the technique it is expected an increase in the absolute value of h* after UV treatment. Results obtained for the benchmark composite are in line with the assumed behaviour of current materials with an 14% increment in the h* value.

(38) Surprisingly, the samples of the material of this invention show the opposite behaviour, getting closer to cero. Remarkably, sample 2 (with 1% of G-OH) reduces its hue (h*) to almost cero after UV treatment, with a 90% reduction.

(39) At the contrary of other black composites, which loss blackness with solar radiation exposure, the perceived blackness of the invention increases after UV radiation. This is considered an exceptional and unexpected behaviour. FIG. 7 shows how the UV exposure degrades the polymer emerging the graphene crystals.

Example 7

(40) Tribological Analysis of the Thermosetting Polymer with the Silane-Functionalized Hydroxyl Graphene.

(41) Friction and wear testing were done according to DIN 50324 with a T79 multi-axis tribometer in pin on disc mode at 5N load 20 rpm using samples 20 mm long and 8 mm of diameter with a total distance of 50 m for each sample. The average friction coefficient (μ) decreases as the content of graphene increases (table 5) due to the auto-lubricant propriety of the material.

(42) TABLE-US-00005 TABLE 5 Friction coefficient improvement μ average sample (x100) 1 68.98 2 67.65 3 61.11 4 54.07 5 43.84 6 39.97 7 36.59 8 31.23

(43) The average mass lose was computed to obtain indicative abrasion resistance data. Table 6 shows the reduction in mass loses in comparison with sample 1 (the resin without graphene). Abrasion data shows a tendency to increase abrasion resistance as the wt % of f-G-OH increases, until the sample 7 (45% wt % of f-G-OH). Sample 8 (50% wt % of f-G-OH) still shows a elevated resistance.

(44) TABLE-US-00006 TABLE 6 Average improvement in mass loses sample average 2 18% 5 66% 6 74% 7 86% 8 79%

Example 8

(45) When an XPS measured is done to the product obtained in example 1, the spectrum shows only a singlet at 533.4 eV which indicates the exclusive existence form of oxygen-containing groups is hydroxy. This can be read in Sun et al. (2016) [Sun, J. Deng, Y., Li, J., Wang, G., He, P., Tian, S., . . . & Xie, X. (2016), A new graphene derivative: hydroxylated graphene with excellent biocompatibility. ACS applied materials & interfaces, 8(16), 10226-10233]. Besides, the exclusive presence of OH functional groups can easily re-confirm obtaining iodine-graphene (G-I) by hydrothermal reaction of G-OH in Kl aqueous solution (3.5 mM) under 120° C. for 24 h. The reaction is reversible through halogenating and hydrolysis reaction cycles. It is well known, that the hydroxyl group is easily substituted by I.sup.−.

(46) The absence of O signal in the XPS spectrum for G-I indicates that all the C—OH groups are replaced by the C-I groups. Moreover, using the habitual techniques EDS and FTIR spectrum is possible to double confirm these results. However due to the experimental error, always present, we assume a small percentage of other than OH groups.