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Synthesis and characterization of CuMoO4/Zn-Al layered double hydroxide hybrids and their application as a reinforcement in polypropylene Biao Wang, Keqing Zhou, Bibo Wang, Zhou Gui, and Yuan Hu Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/ie502232a • Publication Date (Web): 08 Jul 2014 Downloaded from http://pubs.acs.org on July 18, 2014

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Industrial & Engineering Chemistry Research

Synthesis and characterization of CuMoO4/Zn-Al layered double hydroxide hybrids and their application as a reinforcement in polypropylene Biao Wang, † Keqing Zhou, † Bibo Wang, † Zhou Gui, *, † Yuan Hu*,†,‡ †

State Key Laboratory of Fire Science, University of Science and Technology of

China, 96 Jinzhai Road, Hefei, Anhui 230026, People's Republic of China ‡

Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute for Advanced Study,

University of Science and Technology of China, 166 Ren’ai Road, Suzhou, Jiangsu 215123, People's Republic of China * To whom correspondence should be addressed. Tel.: +86-551-3601288; fax: +86-551-3601669; E-mail address: [email protected]. [email protected].

ACS Paragon Plus Environment


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ABSTRACT CuMoO4/Zn-Al layered double hydroxide hybrids were synthesized via an ion exchange and precipitation route. X-ray diffraction (XRD), Transmission electron microscopy-Energy dispersive X-ray spectroscopy (TEM-EDX) analyses results demonstrated the successful fabrication of CuMoO4/LDH hybrids. Subsequently, CuMoO4/LDH hybrids with different loadings were introduced into polypropylene (PP) matrix via a masterbatch-based melt blending method for properties enhancement. With the loading of 5.0 wt% of CuMoO4/LDH hybrids, the initial decomposition temperature of the PP composite was increased by 61oC. Differential scanning calorimetry (DSC) results showed the glass transition temperature (Tg) and the melting temperature (Tm) were both increased for PP composites. Moreover, incorporation of CuMoO4/LDH hybrids markedly reduced peak heat release rate (pHRR) and total heat release (THR) values from micro-combustion calorimeter (MCC) results. Laser Raman spectroscopy (LRS) and Scanning electron microscopy (SEM) images of the char residues of PP composites showed the addition of CuMoO4/LDH hybrids into PP matrix result in the formation of more stable and continuous char than LDH. The dramatical properties enhancement of PP composites is primarily due to the synergistic effects between CuMoO4 and LDH nanosheets: the adsorption and barrier effect of LDH nanosheets slowed down the thermal degradation of the polymer matrix, inhibited the heat and flammable gas release, while CuMoO4 catalyzed the formation of more stable and graphitized char which further improved the thermal and flame retardant properties of PP composites.


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Keywords: Hybrids; Dispersion; Interface interactions; Synergistic effects



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1. INTRODUCTION Polymer nanocomposites containing inorganic additives with layered structures have been an area of both significant academic interest and commercial importance due to their enhanced features compared to conventional composite materials.1-3 The additional of highly dispersed layered inorganic matrices in organic polymers have been shown to dramatically enhance the gas permeability, flame retardancy, and thermal stability of the base polymer.4-6 Polypropylene (PP) is the most widely used polymer matrix due to its ready availability, excellent processability, and relatively low cost.7,8 However, PP is highly combustible, and so an improvement to the flame retardation is urgently required in order to expand its potential applications. In order to improve the flame-retardant properties of polymers, many organic and inorganic flame retardants have been developed, including different kinds of LDHs and molybdates.9,10 Layered double hydroxides (LDHs), also known as anionic clays, make up a class of host-guest material that has positively charged brucite-like sheets, between which intercalated anions and, in general, some water molecules are located.11 The charge on the octahedral sheets is created by substituting some divalent cations with their suitable trivalent alternatives. The charge-balancing anions, such as inorganic acids,12 amino acids,13-15 and anionic polymer,16,17 are encapsulated in the interlayer space and easily exchanged with various anions. The specialities make LDHs have many applications on precursors to CO2 adsorbents, catalysts, thermal stabilizers, IR absorbers, UV absorbers, and nanofillers in polymer/LDH nanocomposites.18-23 As


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flame retardant nanofillers, LDHs have been shown to offer good flame retardancy and smoke suppression properties due to their unique chemical composition and structure.24,25

During combustion, LDHs lose the interlayer water, intercalated

anions, and dehydroxylate to a mixed metal oxide. These processes adsorb huge amount of heat, dilute the concentration of O2, promote the formation of an expanded carbonaceous coating or char on the polymer, protecting the bulk polymer from being exposed to air, and suppress smoke production.26,27 Therefore, LDHs have been regarded as a promising new type of environmentally friendly flame retardant for polymer materials. LDHs also show to be a good absorbent for MoO42-.28,19 On the other hand, Metal molybdates have been recognized for years as effective char formers in polymers. Mechanistically, molybdates promote char formation by a Friedel-Crafts alkylation of alkene linkages formed during polymer thermolysis .30,31 LDHs and molybdates each shows advantages as flame retardant nanofillers in polymers, but to the best of our knowledge, no investigates about the synergistic effects between the LDHs and molybdates on flame retardant PP system have been reported. Herein, in this paper, CuMoO4/Zn-Al layered double hydroxide hybrids were synthesized via the route as shown in Scheme 1 and characterized by XRD, TEM and SEM. Afterwards, CuMoO4/LDH hybrids were used as flame retardant nanofillers in PP to prepare corresponding polymer composites by masterbatch-based melt blending method. In comparison, the corresponding polymer composites based on SDS modified Zn-Al LDH with the loading of 5 wt% were synthesized in parallel. The



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synergistic effects between CuMoO4 and Zn-Al LDH in PP matrix were investigated by TG-DTG, MCC, DSC, LRS and TG-IR. 2. Experimental section 2.1.

Materials.

Zn(NO3)2.6H2O,

Al(NO3)3.9H2O,

NaOH,

Na2MoO4.2H2O,

Cu(NO3)2.3H2O, NaC12H25SO3 (SDS), xylene were all purchased from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China). PP (F401) was supplied as pellets by Liaoning Huajin Chemicals (China). All chemicals were used as received without further purification. The distilled water was produced in our laboratory. 2.2. Synthesis of CuMoO4/Zn-Al LDH hybrids. SDS modified Zn-Al-NO3 LDH was synthesized by a traditional co-precipitation method. In brief, 3.75 g of Al(NO3)3.9H2O, 8.91 g of Zn(NO3)2.6H2O and 5.4 g of SDS were dispersed in 250 ml of deionized water in a three-neck flask with vigorous stirring. The pH of the precipitation solution was controlled at 8.0 using a NaOH (2 M) solution. During the whole synthesis, the system was maintained at 65 °C and protected with N2 gas to prevent the contamination by atmospheric CO2. The precipitated LDH slurry was filtered and washed with H2O until pH = 7. The washed LDH slurry was dispersed in 250ml of deionized water again. Then 100 ml of Na2MoO4.2H2O (0.01 M) aqueous solution was added into the above solution drop-wise under vigorous stirring and N2 protection. After 10 h stirring, the slurry was washed with deionized water several times to remove the redundant MoO42-, and then dispersed in 250 ml of deionized water followed by addition of 100 ml of Cu(NO3)2.3H2O (0.01 M) aqueous solution drop-wise. Afterwards, the obtained green products were separated by filtration,


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washed with deionized water and dried at 60 oC overnight. For comparison, bare SDS modified Zn-Al LDH was also prepared. 2.3. Preparation of (CuMoO4/Zn-Al LDH)/PP nanocomposites.

20 g of PP was

added to a 500 mL round-bottom flask containing 200 mL of xylene and heated to 135 °C. The mixture was dissolved in xylene with the assistance of strong mechanical stirring. After PP was dissolved completely, 4 g of the synthesized CuMoO4/Zn-Al LDH hybrids were added into the mixture. Finally, the viscous green slurry was dried in air at 80 °C for 12 h to remove the xylene. PP nanocomposites were prepared by melt blending at 185 °C using the masterbatch and PP on a twin-roller mill (roller speed of 60 rpm, 8 min mixing), the components were shown in Table 1. 2.4. Characterization. Wide-angle X-ray diffraction patterns of the samples were recorded on an X-ray diffractometer (Rigaku Dmax/rA, Japan), using Cu Ka radiation (0.15418 nm) at 40 kV and 20 mA. The powdery samples were tested in reflection mode. Transmission electron microscopy-Energy dispersive X-ray spectroscopy (TEM-EDS) analysis was conducted using a JEOL JEM-2100 instrument with an acceleration voltage of 100 kV. Scanning electron microscopy (SEM) image was taken using a DXS-10 scanning electron microscope produced by Shanghai Electron Optical Technology Institute. Thermogravimetric analysis (TGA) of samples was carried out with a Q5000 thermal analyzer (TA Co., USA) from 30 °C to 800 °C at a heating rate of 20 oC min-1 in air atmosphere (flow rate of 100 ml min-1). Microscale combustion colorimeter (MCC-2) was used to investigate the flammability



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characteristics of PP nanocomposites according to ASTM D7309-07. Samples of about 5 mg were heated in nitrogen atmosphere at a constant heating rate of 1 oC s-1 from room temperature to 650 oC. The decomposition products were mixed with oxygen (20 mL min-1) and then combusted in the combustion furnace (900 oC). Differential scanning calorimetry (DSC) was performed using a Perkin-Elmer Pyris Diamond DSC-7. Samples (2–4 mg) were heated from 0 to 200 oC at a linear heating rate of 10 oC min-1; the temperature was kept at 200 oC for 10 min and then decreased from 200 to 0 oC at a linear rate of 10 oC min-1. This heating-cooling cycle was repeated, and the data obtained from the second heating section were plotted. Laser Raman spectroscopy (LRS) measurements were carried out at room temperature with a SPEX-1403 laser Raman spectrometer (SPEX Co., USA) with excitation provided in back-scattering geometry by a 514.5 nm argon laser line. Thermogravimetric analysis/infrared spectrometry (TG-IR) of the samples was performed using a TGA Q5000 IR thermogravimetric analyzer that was interfaced to the Nicolet 6700 FTIR spectrophotometer through a Thermo-Nicolet TGA special connector. The stainless steel transfer pipe and gas cell were heated at 200 oC, to avoid the condensation of volatile compounds. 3. Results and discussion 3.1. Characterization of CuMoO4/Zn-Al LDH hybrids and (CuMoO4/Zn-Al LDH)/PP composites. Fig. 1 present the XRD patterns of SDS modified Zn-Al LDH, CuMoO4 and CuMoO4/LDH hybrids. SDS modified Zn-Al LDH shows peaks at 2̀θ= 7.4o, 14.8o, 22.4o, which can be assigned to the (003), (006), (012) reflections of


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Zn-Al LDH. From the (003) diffraction peak, the interlayer distance can be calculated to be 1.18 nm, larger than the 0.88 nm of pure LDH,32 which is beneficial for ion exchange. The diffraction peaks of CuMoO4 match well with the standard card of CuMoO4 (JCPDS card No. 36-0405). All of the major peaks of both CuMoO4 and Zn-Al LDH can be observed in the XRD patterns of CuMoO4/LDH hybrids which indicates the successful synthesis of CuMoO4/LDH hybrids, additionally no redundant peaks have been observed suggesting that CuMoO4/LDH hybrids are of high purity. Besides XRD, TEM-EDX was used to characterize the synthesized CuMoO4/LDH hybrids, as shown in Fig. 2. Fig. 2a and b present the TEM images of SDS modified LDH and CuMoO4/LDH hybrids, respectively. Fig. 2a shows highly transparent thin layers of LDH, the LDH layers disperse well in alcohol though there are still some layers stacking together. As for CuMoO4/LDH hybrids, Fig. 2b shows CuMoO4 nanocrystallines disperse well on the LDH nanosheets. EDX was conducted to identify the existence of CuMoO4, and elements of Zn, Al, Mo, Cu have been detected which further confirm the formation of CuMoO4/LDH hybrids. The influence of CuMoO4 on the thermal stability of Zn-Al LDH was investigated by TGA analysis. Fig. 3 presents the TGA curves of SDS modified Zn-Al LDH, CuMoO4 and CuMoO4/LDH hybrids. CuMoO4 shows a slight weight loss at the range of 350 °C to 400 °C, and Zn-Al LDH displays a three-step thermogravimetric profile corresponding to physisorbed water (from room temperature to 150 °C), chemisorbed water (150–250 °C) and the water arising from the dehydroxylation of the layers (250– 450 °C), respectively. CuMoO4/LDH hybrids exhibit a similar thermogravimetric



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profile, while compared to LDH, the degradation temperatures of three stages are all decreased. It indicates CuMoO4 promotes the degradation of Zn-Al LDH. The fractured surfaces of pure PP and PP composites were characterized by SEM to investigate the inner structure of the composites. Fig. 4 shows CuMoO4/Zn-Al LDH layers disperse well in all the PP nanocomposites, resulting from the introduction of SDS and CuMoO4. Most of the layers are inserted into the PP matrix indicating that CuMoO4/Zn-Al LDH hybrids have good interfacial adhesion with PP matrix in the composites. As to observe the dispersion of LDH and CuMoO4/LDH hybrids in PP matrix directly, TEM micrographs of PP3 and PP4 are shown in Fig. 5. It is clearly observed that the LDH layers are randomly dispersed in PP matrix. Both SEM and TEM images show LDH and CuMoO4/LDH have a good dispersion in PP matrix. 3.2. Thermal analysis. The thermal stability of (CuMoO4/Zn-Al LDH)/PP composites were calculated by TGA under nitrogen atmosphere. Fig .6 illustrates the TGA curves of pure PP and PP composites. The temperature corresponding to 10 wt% weight loss (T0.1) which is defined as the onset degradation temperature and 50 wt% weight loss (T0.5) are also reported in Table 1. It is noted that both PP and PP composites show a one stage thermal degradation process. T0.1s and T0.5s of the PP composites are all higher than those of pure PP, and increase from PP0 to PP3 with the increased loading of CuMoO4/Zn-Al LDH hybrids. Compared to pure PP, the T0.1 and T0.5 increase by 61 and 56 oC for PP3, which are all higher than PP4. Table 2 shows the Char residue date of LDH, LDH-CuMoO4 and PP nanocomposites, the char residue yield and the accretion yield of PP3 at 650 oC are 6.7 % and 1.5%, higher than


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5.5 % and 0.6% of PP4, which indicates CuMoO4/Zn-Al LDH hybrids catalyze generating more char residue than pure LDH. From the TGA results, both LDH and CuMoO4/Zn-Al LDH hybrids enhance the thermal stability of PP, while CuMoO4/Zn-Al LDH hybrids are more effective and PP3 has the best thermal stability. This significant improvement in thermal stability of PP3 could be attributed to four factors; CuMoO4/Zn-Al LDH hybrids disperse evenly in PP matrix; the strong interaction between CuMoO4/Zn-Al LDH hybrids and PP polymer chains; the physical barrier effect of LDH layers; CuMoO4/Zn-Al LDH hybrids catalyze the formation of more char residue. Fig. 7 plots the DSC curves of PP and PP composites, and the Tm values calculated from the DSC curves were presented in Table 3. It shows when Zn-Al LDH and CuMoO4/Zn-Al LDH hybrids were incorporated into PP matrix, the Tm were increased as the additive content increased. Compared to PP4, PP3 has a higher Tm value. The reasons for PP composites have the increased Tm values, especially for PP3 has the highest values can be conclude as: LDH layers limit the motions of PP chains; CuMoO4/Zn-Al LDH hybrids have a better dispersion in PP matrix than Zn-Al LDH. 3.3. Fire resistance of the composites. MCC was used to investigate the fire resistance properties of PP composites. Fig. 8 presents the HRR and THR curves of PP and PP composites, and the corresponding combustion data are listed in Table 4. The MCC results show incorporating Zn-Al LDH and CuMoO4/Zn-Al LDH hybrids into PP matrix both reduce the pHRR and THR values significantly. The addition of



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Zn-Al LDH and CuMoO4/Zn-Al LDH hybrids (5 wt%) gives rise to a 40% and 29% reduction in pHRR, 11% and 8% reduction in THR, respectively. The mechanism of CuMoO4/Zn-Al LDH hybrids in reducing the flammability of PP is probably attributed to creation of a barrier effect on the surface of the polymers which could slow down the heat and mass transfer between gas and condensed phases, and prevent the underlying material from further combustion. 3.4. Mechanism analysis. In order to explore the flame retardant mechanism of PP composites, analyzation of the char residues obtained from calcining of 30 g PP and PP composites at 600 oC for 10 min under air atmosphere and the gas products generated during the thermal degradation process were performed via LRS and TG-IR. The corresponding SEM images of the char residues are shown in Fig. 9. With the incorporation of Zn-Al LDH and CuMoO4/Zn-Al LDH hybrids, the residues become more compact, especially for PP3 and PP4. While, obviously, PP3 obtains much more continuous char than PP4, which would be explained by the LRS results. Raman spectra of the residues of PP3 and PP4 are presented in Fig. 10, two typical peaks at 1355 and 1596 cm-1 can be observed which indicate the char structures. The former band (D-band) is associated with vibration of carbon atoms with dangling bonds in the plane terminations of disordered graphite or glassy carbons. And the latter (G-band) corresponds to an E2g mode of hexagonal graphite and is related to the vibration of sp2-bonded carbon atoms in a graphite layer. The graphitization degree of the char can be estimated by a ratio of the intensity of the D and G bands (ID/IG), where ID and IG are the integrated intensities of the D and G bands, respectively.


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Basically, the lower the ratio of ID/IG, the better the structure of the char is. According to Fig. 10, the ID/IG ratio follows the sequence of PP3 (3.9) < PP4 (5.9), indicating a higher graphitization degree and the more thermally stable char structure of the PP3.33 The result of LRS confirms the graphitization degree of the residual char of the PP3 is higher than PP4, which agrees well with the SEM images of the char residues FTIR spectra of the gas products of PP0, PP3 and PP4 at different stages of thermal decomposition are presented in Fig. 11. Some small molecular gaseous decomposition products evolved from PP and PP composite are identified unambiguously by characteristic strong FTIR signals, such as –C–H groups for allyl alcohol, acetone, ethers and various hydrocarbons (3100–2800 cm-1), CO2 (2360 cm-1), CO (2180 cm-1) and aromatic compounds (1605, 1510 and 1460 cm-1).34-36 The spectra of both PP and PP composites are similar, while the peak intensity of PP composites is lower than pure PP, except for the peak at 2360 cm-1 corresponding to CO2. The absorbance of gas products for PP and PP composites versus temperature are presented in Fig. 12. As can be observed, PP composites get lower absorbance intensity of the pyrolysis products (hydrocarbon, CO, aromatic compounds) than pure PP, while higher absorbance intensity of CO2, especially for PP3. The increase of the non-flammable CO2 will dilute the flammable gases which is helpful to retard the thermal degradation. Furthermore, the reduction of toxic CO in smoke and gases will be beneficial for fire rescue when an accident happens. Obviously, there is an evident synergistic effects between CuMoO4 and Zn-Al LDH for reducing CO and improving fire resistance and thermal stability of the PP composites.



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4. Conclusion In this paper, CuMoO4/Zn-Al LDH hybrids were synthesized via an ion exchange and precipitin route, characterized by XRD, SEM and TEM-EDX.

TEM images show

that CuMoO4 nanocrystallines randomly disperse on the LDH nanosheets. Then PP composites with different loadings of CuMoO4/LDH hybrids and LDH of 5.0 wt% were prepared via a masterbatch-based melt blending method. The results exhibit PP composites have higher T0.1, Tg, Tm values and lower pHRR, THR values than pure PP. The T0.1 of PP3 and PP4 increases by 61 oC and 42 oC compared to that of the pure PP, respectively. Moreover, the pHRR and THR values reduced by 40% and 11% for PP3, 29% and 8% for PP4, compared to those of pure PP. The notable improvement of the fire retardant properties is mainly attributed to the synergistic effects between CuMoO4 and Zn-Al LDH: in gas phase, the presence of CuMoO4 / Zn-Al LDH hybrid acts as a physical barrier that could slow down and reduce the release of combustible gas and CuMoO4 is benefit for oxidating CO; in the condensed phase, the addition of CuMoO4 / Zn-Al LDH hybrid resulted in the formation of a compact and insulating char layer to protect the inner polymer matrix from further burning. This work provide a way to combine the application of LDHs used as MoO42- adsorbent and flame retardant nanofillers. Acknowledgements This work was supported by National Natural Science Foundation of China (No.51036007) and China Postdoctoral Science Foundation (No. 2013M531523).


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(21) Evans, D. G.; Duan, X. Preparation of Layered Double Hydroxides and Their Applications as Additives in Polymers, as Precursors to Magnetic Materials and in Biology and Medicine. Chem. Commun. 2006, DOI: 10.1039/B510313B, 485−496. (22)

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Scheme 1. Illustration of the preparation process of CuMoO4/Zn-Al layered double hydroxide hybrids. Figure captions Figure. 1. XRD patterns of LDH, CuMoO4, and CuMoO4/Zn-Al LDH hybrids. Figure. 2. TEM observation of LDH (a), CuMoO4/Zn-Al LDH hybrids (b) (the picture inside b is the corresponding EDS analysis). Figure. 3. TG/DTG curves of LDH, CuMoO4, and CuMoO4/Zn-Al LDH hybrids. Figure. 4. SEM Images for pure PP and PP composite of the fractured surfaces cryogenically broken after immersion in liquid nitrogen. Figure. 5. TEM observations of ultrathin sections obtained from PP3 (a) and PP4 (b). Figure. 6. TGA/DTG curves of PP and PP composites in nitrogen condition. Figure. 7. DSC curves of PP and PP composites. Figure. 8. HRR and THR curves of PP and PP composites.


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Figure. 9. SEM images of the char residue of PP composites. Figure. 10. Raman curves of the residue of PP3 and PP4. Figure. 11. FTIR spectra of pyrolysis products for PP0, PP3 and PP4 at different stages of decomposition. Figure. 12. Absorbance of pyrolysis products forPP0, PP3 and PP4 vs. temperature.

Sample PP0

Component PP

T0.1 (℃)

T0.5 (℃)

298

336

PP1

PP/CuMoO4-LDH (1%)

342

377

PP2

PP/CuMoO4-LDH (3%)

351

394

PP3

PP/CuMoO4-LDH (5%)

360

391

PP4

PP/LDH (5%)

341

379

Table 1. Formation and TGA data of PP composites in nitrogen atmosphere.



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Samples LDH LDH-CuMoO4 PP0 PP1 PP2 PP3 PP4

Char yield at 650 Char yield at 650 oC Char yield at 650 oC o C (%. calculated) (%. measured) (%. accretion) 50.8 55.4 2.6 3.1 4.1 1.0 4.2 5.0 0.8 5.2 6.7 1.5 5.0 5.6 0.6

Table 2. Char residue date of LDH, LDH-CuMoO4 and PP nanocomposites in nitrogen atmosphere.


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Sample PP0 PP1 PP2 PP3 PP4

Tm (℃) (±1%) 169 173 174 177 175

Table 3. DSC data of PP and PP composites.



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HRC (J g-1 K)

THR (k J g-1)

pHRR (W g-1)

(±5%)

(±5%)

(±5%)

PP0

1042

34.5

1059

PP1

874

31.8

891.2

PP2

781

30.5

793.1

PP3

632

30.6

641.1

PP4

735

31.6

746.4

Sample

Table 4. MCC combustion date of pure PP and PP composites.


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Scheme 1. Illustration of the preparation process of CuMoO4/Zn-Al layered double hydroxide hybrids.



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Figure. 1. XRD patterns of LDH, CuMoO4, and CuMoO4/Zn-Al LDH hybrids (

correspond the peaks of LDH,

correspond to CuMoO4)


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Figure. 2. TEM observation of LDH (a), CuMoO4/Zn-Al LDH hybrids (b), (c) and the EDS analysis of CuMoO4/Zn-Al LDH hybrids (d).



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Figure. 3. TG/DTG curves of LDH, CuMoO4, and CuMoO4/Zn-Al LDH hybrids.


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Figure. 4. SEM Images for PP0 (a), PP1 (b), PP2 (c), PP3 (d), PP4 (e) of the fractured surfaces cryogenically broken after immersion in liquid nitrogen.



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Figure. 5. TEM observations of ultrathin sections obtained from PP3 (a) and PP4 (b).


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Figure. 6. TGA/DTG curves of PP and PP composites in nitrogen condition.



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Figure. 7. DSC curves of PP and PP composites.


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Figure. 8. HRR and THR curves of PP and PP composites.



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Figure. 9. SEM images of the char residue of PP1 (a), PP2 (b), PP3 (c), PP4 (d).


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Figure. 10. Raman curves of the residue of PP3 and PP4.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 ACS Paragon Plus Environment

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Figure. 11. FTIR spectra of pyrolysis products for PP0, PP3 and PP4 at different stages of decomposition.

Figure. 12. Absorbance of pyrolysis products forPP0, PP3 and PP4 vs. temperature.


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