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The degradable poly (lactic acid)/MOFs nanocomposites exhibiting good mechanical, flame retarded and dielectric properties for the fabrication of disposable electronics Xiaowei Shi, Xiu Dai, Yu Cao, Jiawei Li, Changan Huo, and Xinlong Wang Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.6b04204 • Publication Date (Web): 21 Mar 2017 Downloaded from http://pubs.acs.org on March 22, 2017

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Industrial & Engineering Chemistry Research

The degradable poly (lactic acid)/MOFs nanocomposites exhibiting good mechanical, flame retarded and dielectric properties for the fabrication of disposable electronics Xiaowei Shi, Xiu Dai, Yu Cao, Jiawei Li, Changan Huo, Xinlong Wang* School of Chemical Engineering, Nanjing University of Science & Technology, Nanjing 210094, China

﹡Corresponding Author. E-mail: [email protected]. Tel.: +86 25 8431 5949.

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Abstract: The nano metal-organic frameworks (ZIF-8) particles were synthesized and the poly (lactic acid) (PLA)/ZIF-8 nanocomposite films were prepared by solution blending and film casting method. The addition of nano ZIF-8 particles improved the mechanical properties and had an impact on the crystallization of PLA. The electrical properties of the PLA/ZIF-8 nanocomposites were found to be dependent on the frequency and the ZIF-8 content. The prepared PLA/ZIF-8 films had good transparency even as the content of the nano ZIF-8 particles was up to 3 wt%. Compared with 21.5% of pure PLA, the limited oxygen index value of the nanocomposite film containing 1wt% ZIF-8 reached 26.0%. Therefore, it is proposed that the prepared nanocomposites can be used to make the disposable electronics as the substrates and dielectric. The char residues after burning were studied by SEM, Raman and XPS in detail and the flame retarded mechanism was also discussed. Keywords: Poly (lactic acid), ZIF-8, mechanical properties, electrical properties, flame retardancy


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1. Introduction In the past few years, the upgrading of electronic products is getting faster and faster even to average of several months, which leads to the e-waste problem.1, 2 At present, more than 50 million tons of electronic and electrical appliance are no longer used and become garbage within a year. For example, nearly 47.5% domestic harmful waste in UK comes from the discarded electronic products and plastics.3 It is also noteworthy that more plastic waste will be produced along with the development of the plastic electronic products. Therefore, the green electronic products, which are made of environmentally friendly and disposable materials such as the degradable polymers, are needed to solve the e-waste problem.4, 5, 6 Many degradable polymeric materials have been exploited to manufacture the environmentally-friendly and disposable electronic device as the substrates and dielectric as shown in Figure 1. Among those, poly (lactic acid) (PLA) has received considerable attention. PLA is a commercially aliphatic polyester and has some similar properties with traditional polymers such as polystyrene (PS) and poly(ethylene terephthalate) (PET), which makes it widely to be used in packaging, electronic and automobile industries.7, 8, 9 However, there are very few examples of the PLA’s application in the making of electronic devices heretofore. The very low glass transition temperature (Tg), brittleness, unsatisfactory dielectric property and high combustibility of PLA could partially prevent PLA from applications in electronic devices.10, 11 Géczy et al.12 reported that PLA could be used as the substrate of copper-clad plate. Mattana et al.13investigated the fabrication of all-solution-processed organic electronic devices using the spin-coated PLA thin films as the substrates.

Figure 1. Structure of the electronic device Generally, adding nano fillers is one of the efficient methods to improve the performances of polymers.14 Poly(vinyl acetate)/Cadmium sulfide (PVA/CdS) nanocomposites containing varying



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weight percentages of CdS nanoparticles prepared by J. Koteswararao showed that the dielectric constant depended not only on the frequency, but also on the CdS concentration. The dielectric constant decreased with increase in frequency and CdS concentration.15 Rao16 investigated the structural and dielectric properties of the CuO-PVA composite films. The results showed that both the dielectric constant and the dielectric loss were reduced with increase in CuO concentration. The results from dynamic mechanical analysis of PLA/graphene oxide-ZnO nanocomposites exhibited a significant enhancement in Tg. Bourbigot showed that incorporating the multi-wall carbon nanotube (MWNT) into PLA by reactive extrusion method can improve the flame retardancy of PLA nanocomposites.17 Recently, nano metal-organic frameworks (MOFs) have drawn a growing interest among the researchers of various fields.18, 19 MOFs are formed through coordination bonds between organic binding ligands and metal ions.20 Compared with traditional particles, nano MOFs particles are well crystalline crystals with high specific surface and flexible structures,21 and that results in better affinity with polymer chains since the organic linkers in MOFs can provide stronger interaction with polymer chains.22 Elangovan et al23 investigated the optical, physical, thermal, mechanical and thermomechanical properties of the PLA/MOFs nanocomposites. Nevertheless, the effects of nano MOFs particles on mechanical, flame retarded and dielectric properties of PLA have not been evaluated systematically yet. In this paper, the nano ZIF-8 particles (NZP) were prepared and blended with PLA by solution-blending to prepare the PLA/ZIF-8 nanocomposites. The full mechanical, electrical, and flame retardance characterizations of the prepared nanocomposites shown that they exhibit good mechanical, dielectric and flame retardant properties and then suits the fabrication of disposable electronics as the substrates and dielectric. 2. Experimental 2.1 Materials Poly (lactic acid) (Haizheng 290) was purchased from Haizheng Biological Materials Co. (Zhejiang, China). 2-Methyl imidazole (98%) was purchased from Aladdin Industrial Corporation (Shanghai, China). Zn(NO3)2·6H2O and methanol (CH3OH) were provided by Sinopharm Chemical Reagent Co., Ltd. (China). Chloroform (99%) was supplied by Shanghai Lingfeng Chemical Reagent Co. (Shanghai, China). 2.2 Preparation of NZP


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2-Methyl imidazole (1.95 mmol, 1.602 g) was dissolved in methanol (100 mL) at room temperature. Zn(NO3)2·6H2O (5 mmol, 1.487 g) dispersed in methanol (100 mL) was added to the above solution with magnetic stirring. Then, the mixture was stirred for 1 h (25 oC). The obtained white solid was centrifuged, washed with CH3OH (3*30 mL) and then dried at 80 oC. 2.3 Preparation of the PLA/ZIF-8 nanocomposites PLA was dried at 50oC for 24 h. Then, PLA was dissolved in 40 mL chloroform with magnetic stirring for 2 h at room temperature. NZP were dispersed in chloroform to form a uniform dispersion, which was then blended with PLA solution. The mixture was stirred for 4 h and then was cast to a thin film by using the automatic coating machine (MRX-TMH250, Shenzhen Ming Rui Xiang Automation Equipment Co. Ltd, China). The PLA/MOFs film with thickness of ~0.15 mm was obtained after the evaporation of the solvent at room temperature. Finally, the film was dried in an oven at 60 °C for 48 h to further remove the residual solvent further. For the sake of brevity, we have named nanocomposites PLA, PLA-1, PLA-2, PLA-3 and PLA-4, in which the content of NZP was 0, 0.2, 0.5, 1 and 3 wt%, respectively. The thicknesses of the films after drying in oven were about 0.140mm±0.002mm (the film thickness of the PLA, PLA-1, PLA-2, PLA-3 and PLA-4 is 0.141mm, 0.140mm, 0.139mm, 0.142mm, and 0.138mm, respectively). The formulations of the PLA/ZIF-8 nanocomposites under investigation are listed in Table 1. Table 1. Formulations and DSC parameters of the PLA/ZIF-8 nanocomposites Samples

PLA(wt%)

NZP(wt%)

Tc(oC)

Tg(oC)

Tm1 (oC )

Tm2 (oC)

Xc(wt%)

PLA

100

0

-

56.5±0.1

-

174.0±0.1

0

PLA-1

99.8

0.2

114.6±0.1

72.7±0.3

170.0±0.1

176.5±0.2

43.6±0.1

PLA-2

99.5

0.5

114.8±0.2

71.8±0.1

167.5±0.1

174.8±0.3

43.2±0.1

PLA-3

99

1

113.2±0.3

71.4±0.1

165.1±0.2

172.7±0.1

58.2±0.2

99

1

111.1±0.1

71.2±0.2

160.3±0.3

168.8±0.2

63.8±0.2

PLA-4

2.4 Measurement and characterization X-ray diffraction (XRD) measurements were carried out by Bruker D8 Advance diffractometer at 40 KV and 40 mA with Cu Kα radiation (=0.15418 nm). Its scanning speed was 30°/min. The morphologies of ZIF-8 and the fracture surfaces of PLA-2 and PLA-4 were investigated by Hitachi S-4800 Scanning electron microscopy (SEM). All samples were plated with gold before the test. The thickness of gold coating was about 10nm.



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DSC measurement was investigated by a Q80 DSC Apparatus (TA Instruments, America). The sample weight was kept about 5 mg. At first, the samples were heated at 220oC for 3 min to remove the crystallization thermal history. The samples were then quenched from 220oC down to 30oC at cooling rates of 10oC/min, followed by a re-heating scan up to 220oC at a heating rate of 10oC/min. Three replicas of measurement were performed. The crystallinity (Xc) was obtained from the equation as follows: Xc =△Hc/△Hm0 (1-φ) Where △Hc is the crystallization enthalpy (J/g), the Hm0 is the melting enthalpy of the 100% crystallized PLA (93.6 J/g), and φ is the weight fraction of the dispersed phase in composites. Limiting oxygen index (LOI) tests were performed on a JF-3 oxygen index meter (Jiangning Analysis Instrument Co., China) according to ASTM D2863-97 for five times. The UL-94 vertical test was measured by CZF-3 type instrument (Jiangning Analysis Instrument Co., China) according to ASTM D3801. Five replicas of measurement were performed. All the relevant experimental data were obtained through statistical analysis. Tensile testing measurements were measured by Instron1121 machine at the rate of 10mm/min at room temperature according to ASTM D638. Condition the test specimens at 23±2°C and 50 ±5% relative humidity for not less than 40h prior to test. The values were averaged over five measurements. A Shimadzu UV-2101PC spectrophotometer equipped with an integrating sphere was used to obtain the UV-visible spectra of the samples. The thicknesses of the tested films were kept about 0.140mm±0.002mm. Air was used as a reference during the UV-vis transmittance spectra measurement. The electrical characterization of the nanocomposites was performed at room temperature and high frequency LCR meter (TH2816) with a frequency range from 1 kHz to 150 KHz was employed. The electrical characterizations of the nanocomposites were determined by the method of parallel plate capacitor. In the process of testing, the thickness of the films was kept at 0.140mm±0.002mm measured by a digital display micrometer (SHAHE, China), and the tightening force was constant to avoid changing the thickness of the films. The permittivity (εr) was calculated from the relation as follows: εr = C*d/A*ε0


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Where A is the area of the electrode, ε0 is the dielectric constant of the vacuum (ε0 = 8. 854187817 × 10-12 F/ m), d is the thickness of the film after drying in oven. The capacitance (C) and the dielectric loss tangent (tan δ) were read directly by high frequency LCR meter (TH2816). Raman spectra were obtained on a Renishaw Invia laser Raman spectrometer (England) using He laser beam excitation, and the wavenumber ranges from 500 cm-1-3000 cm-1. The X-ray photoelectron spectroscopy (XPS) analysis was carried out on a PHI5300 spectrometer (ELMER, America) with Al Kα as the excitation radiation. 3. Results and discussion 3.1 General characterization of NZP The X-ray diffraction pattern of NZP is shown in Figure 2 (a). All peaks are in agreement with the previous reports, confirming the formation of pure crystalline ZIF-8 phase. One intensive and sharp peak is observed at around 2θ=7.36°, which reveals the high crystallinity of the synthesized NZP.24 Figure 2 (b) shows the SEM image of NZP and the spherical shape nanoparticles with the narrow size distribution are observed. The average diameter of NZP is about 102 ± 22 nm (analyzed by Nano Measurer 1.2).

Figure 2. XRD (a) and SEM image (b) for ZIF-8 3.2 SEM of the PLA/ZIF-8 nanocomposites In order to study the dispersion of NZP in the polymer matrix, the cross-sections of the PLA and PLA/ZIF-8 nanocomposites films are observed by SEM. Figure 3 shows the higher and lower magnification images of SEM for PLA, PLA-2 and PLA-4. In Figure 3 (a) and (b), pure PLA shows a flat and smooth section owing to the brittle failure behavior. With the content of 0.5 wt%, NZPs are well embedded and dispersed homogeneously in PLA matrix without significant agglomeration as shown in Figure 3 (c) and (d). Such dispersion is possibly owing to the good interfacial affinity between ZIF-8 and PLA. As a matter of fact, there exist numerous interactions between the ester groups on the chain of PLA and the surface of NZP.25 However, when the NZP



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content is increased to 3 wt%, agglomeration appears (see the black arrows in the Figure 3 (f)).

Figure 3. SEM images for the nanocomposites (a and b: PLA; c and d: PLA-2; e and f: PLA-4) 3.3 The effect of ZIF-8 on crystallization and Tg of the PLA/ZIF-8 nanocomposites Figure 4 (a) and 4 (b) show the DSC non-isothermal thermograms of the PLA/ZIF-8 nanocomposites during cooling step and reheating step at a rate of 10oC/min, respectively. The relevant data for all samples is summarized in Table 1. In Figure 4 (a), it can be seen that pure PLA does not exhibit the exothermic process during the cooling scan, suggesting that the used PLA is difficult to crystallize in the non-isothermal process. On the contrary, there is an obvious exothermic peak for the PLA/ZIF-8 nanocomposites, which shows that NZP could act as the nucleation agent and accelerate crystallization of PLA. On the basis of cooling enthalpies, the percentage crystallinity (Xc) for the PLA/ZIF-8 nanocomposites is calculated, and compared with the 0 of pure PLA, it also can be seen that incorporating NZP into the PLA matrix results in increasing Xc as shown in Table 1. Figure 4 (b) displays that all samples have the glass transition and melting behavior. However, only pure PLA has cold crystallization manifesting that the PLA/ZIF-8 nanocomposites have finished crystallization procedure during the cooling step. The results in Table 1 show that the addition of NZP increases the glass transition temperature (Tg) of o

o

the PLA/ZIF-8 nanocomposites evidently. The Tg values increase from 56.5 C for PLA to 71.8 C for PLA-2. The PLA chain mobility is reduced on account of the large specific surface area and the reinforcing effect of NZP.26 The Tg influences the applications of the PLA/ZIF-8


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nanocomposites in electronics. Nevertheless, as can be seen from Figure 3 and Table 1, the melting peak temperatures (Tm) of the PLA/ZIF-8 nanocomposites are reduced, compared with pure PLA. This can be accomplished by the phase equilibrium theory of thermodynamics which ZIF-8 acts as an impurity to decrease the melting point.27 The small melting peak at lower temperature for the nanocomposites is owing to the less organized crystals.28

Figure 4. DSC for the nanocomposites: (a) cooling, (b) reheating 3.4 The electrical properties of the PLA/ZIF-8 nanocomposites In order to investigate the insulation characteristics of the PLA/ZIF-8 nanocomposites films, we measured its permittivity (εr) and dielectric loss tangent (tan δ) in the frequency ranging from 1 kHz to 150 kHz. The electrical properties of the nanocomposites films are shown in Figure 5 (a) and (b). In Figure 5 (a), it can be seen that εr of the nanocomposites films decreases as the measuring frequency increasing. At low frequencies, the electronic, ionic, dipolar, and interfacial or surface polarization are beneficial for the reducing εr of the nanocomposites.15 However, with the increase of the working frequency, only the electronic part plays an important part. In addition, the reduction of εr with increase in frequency could also be attributed to the fact that less time will be used for the interfacial dipoles to orient themselves in the direction of the alternating field at high frequencies.29 It is also observed that εr value gradually decreases with NZP loading from 0.2 to 3 wt% in Figure 5(a). Since the air has a low εr (close to 1), the most effective method to reduce the εr of the nanocomposites is to introduce nano/microvoids in the matrix.30 As one of the most important ZIF members, ZIF-8 is the porous material and has larger pore sizes compared with zeolites which is helpful in reducing εr of the nanocomposites. The tanδ is resulted from consumption of energy of the alternating electric field which turns into heat and dissipate. Generally, the dielectric loss is caused by the distortional, dipolar, interfacial, and conduction loss. At low frequencies, the four interactions have equal contributions. With the increase of frequency,



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the dielectric loss is mainly owing to the interfacial loss. 31Figure 5 (b) shows the effects of frequency and ZIF-8 on tan δ of the PLA/ZIF-8 nanocomposites. It can be seen that tan δ decreases with the incorporation of NZPs. This may be explained by the uniform dispersion of NZPs in the insulating matrix and these nanoparticles can make electron to tunnel through in turn, impeding the charge carrier of the whole system to migrate directionally by the action of electric field.32

Figure 5. Permittivity (a) and dielectric loss tangent (b) for the nanocomposites 3.5 The mechanical properties of the PLA/ZIF-8 nanocomposites Figure 6 shows the mechanical properties of the nanocomposites and it is obvious that addition of NZP influences the mechanical properties of the nanocomposites evidently. In Figure 6(a), the tensile strength of PLA-2 containing 0.5 wt% NZP is 58.25 MPa, while the value of pure PLA is about 53.15 MPa. With increasing amount of NZP, the tensile strength of the samples decreases and the value of PLA-4 with 3 wt% NZP is 51.99 MPa. The tensile strength of nanocomposites is related to the dispersion effects of the nano fillers in matrix33 as well as the interfacial interactions between matrix and fillers.34 The improvement of the tensile strength for the nanocomposites could be due to the good dispersion of NZP, the good interfacial adhesion between NZP and PLA as shown in SEM as well as the reinforcing effects of NZP.35 Besides, NZP also have nanometer effect, unique surface structure and very high surface area, which can absorb and disperse impact energy.23 The decrease of tensile strength at high loading of NZP can be explained by aggregation and then the cracks formed. The aggregation and the cracks make the prepared nanocomposites more vulnerable to rupture.36 The elongation at break and modulus of nanocomposites are also shown in Figure 6 (a) and 6 (b), and their variation trends are similar to that of the tensile strength. The reasons for these variation trends are similar that of the tensile strength and the aggregation of NZP, which leads to the decrease of modulus for the PLA-3 and PLA-4 compared with PLA-2.


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Figure 6. Tensile strength, elongation (a) and modulus (b) for the nanocomposites 3.6 Optical properties of the PLA/ZIF-8 nanocomposites Figure 7 shows the UV-vis transmittance spectra of the PLA/ZIF-8 nanocomposites and all the nanocomposites show high transparency. The good compatibility between the PLA and NZP, the good dispersion of NZP in the PLA matrix as well as the high transparency of NZP can be proved by the high transparency.37 For the nano-filled materials, the good compatibility between the nano-fillers and the polymer matrix could lead to the good dispersion of nano-fillers in the matrix. The good dispersion of nano-fillers could have few effect on the transmittance of the nanocomposites, and therefore the prepared nanocomposites exhibit high transparency.38 Besides, as can be seen from Figure 7, the transmittance of the films decreases with increasing amount of ZIF-8. It can be explained by the facts that the aggregation and the crystallization effects of the NZP influence the transparency of the films.39 Figure 8 gives the photographs of the PLA/ZIF-8 films. It can also be seen that all the films have excellent transparency. And even the content of NZP reaches 3wt%, the background “NJUST” can still be clearly observed. The transparency of the films is very important to their application.

Figure 7. UV-vis transmittance spectra of the nanocomposites



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Figure 8. Photographs of the nanocomposites 3.7 The flame retardancy of the PLA/ZIF-8 nanocomposites The LOI values and the UL-94 levels of the PLA/ZIF-8 nanocomposites are displayed in Table 2. Table 2 shows the average (Avg) and the standard deviation (SD) of all the data. The results show that the LOI value of pure PLA is 20.5% and cannot pass the UL-94 test, which proves that PLA is a flammable polymer. The increase in the LOI values of the nanocomposite is observed and the presence of NZP makes the self-extinguish time shorter. When the content of NZP rises to 0.2 wt%, the LOI value increases to 23.5% and its average burning time is 15.80s. With the amount of 0.5, 1, 3 wt% of ZIF-8, the LOI values of the nanocomposites are 23.5%, 24.5%, 26.0% and the average burning periods are 4.35 s, 4.28 s, 2.90 s, respectively. In summary, a very small amount of NZP can achieve a relatively good flame retardant effect for the PLA/ZIF-8 nanocomposites. Table 2. Flame retardancy of the PLA/ZIF-8 nanocomposites Samples

UL-94 rating

LOI (%)

Average burning time(s)

Flaming dripping

VTM Rating

0.37

Yes

Failed

15.8

0.13

Yes

VTM-2

0.09

4.4

0.26

Yes

VTM-2

26.0

0.29

4.3

0.19

Yes

VTM-2

22.5

0.18

2.9

0.22

Yes

VTM-2

(n=5)

Avg

SD

Avg

SD

PLA

20.5

0.30

20.9

PLA-1

23.5

0.14

PLA-2

24.5

PLA-3 PLA-4

The SEM micrograph of the residual char for PLA-3 is given in Figure 9 (a). Because pure PLA does not leave any residual char after combustion, the melt dripping residue of PLA is given in Figure 9 (b) for comparison. It can be observed in Figure 9 (a) that the char is tight and coherent, indicating that a coherent char layer for the nanocomposites can be formed by the addition of NZP.40 This char layer is positive for thermal and oxygen blockage and then could prevent the fire from spreading.


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Figure 9. SEM image of residue for the PLA-3 (a) and the photograph of melt dripping residue for pure PLA (b) Figure 10 (a) shows the Raman spectra of the char residues. Two intensive and sharp peaks are observed at around 1376 cm-1 and 1592 cm-1, and the other small peak is presented at 1121 cm-1. The peak at about 1121 cm-1 is assigned to the stretching vibrations of C-N left by the incomplete combustion of NZP.41 The peak at about 1376 cm-1 corresponds to D band, which is due to the carbon atoms in disordered graphite. The other peak at about 1592 cm-1 corresponds to G band, which is assigned to the oriented graphitic structure. The overall XPS spectrum (b) and O1s spectrum (c) for the char residues are shown in Figure 10. In Figure 10 (b), it can be observed that the residues are composed of C, N, O and Zn elements. In O1s spectrum, the peak at 530.8 eV is attributed to =O in carbonyl and the peak at 532.2 eV is owing to C-O and C=O groups of PLA.42 The peak at 530.2 eV is assigned to the Zn-O bond.43



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Figure 10. Raman spectra (a), overall XPS spectra (b) and O1s (c) of residues for the PLA-3 The flame retardancy contribution for each type of nanoparticles varies and strictly depends on its chemical structure and geometric shape. Three widely investigated nanoparticles in flame retardancy are layered materials, such as nanoclays, fibrous materials such as carbon nanotubes and particulate materials such as aluminum hydroxide and spherical silica nanoparticles.44 ZIF-8 is composed of Zn-O-Zn dinuclear units and imidazole units containing large amount of nitrogen.45 As we know, nitrogen-containing compounds are usually used as the flame retardants and the Zn-containing compounds, for example, ZnO can also be applied as the flame retardants or the synergistic flame retardants.46 Besides, as the well crystalline crystals, NZP could act as the nano flame retardant. The probable flame retardant mechanism of NZP is presented in Figure 11 and the NZP may play a role in the gas phase and/or solid phase. Firstly, NZP is comprised of imidazolate, which means ZIF-8 contains large amount of nitrogen. Therefore, the nanocomposites could give off N2 and NH3 during burning which releases energy and dilutes the ignitable gas.47 Secondly, the


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improved flame retardancy of nanocomposites could be caused by the restriction of the mobility of polymer chains from the strong interactions between PLA and the NZP surface. Thirdly, known as a class of crystalline microporous materials, NZP shows high chemical catalytic activity. The char formation during combustion has been explained the dehydrogenation and crosslinking reactions catalyzing by NZP or the decomposition products of NZP such as ZnO.

Figure 11. The flame retardant mechanism of NZP 4. Conclusions The nano ZIF-8 particles were successfully synthesized and then added into PLA. DSC analysis showed that NZP could reduce Tc and Tm of the prepared nanocomposites, whereas the Tg and Xc (wt%) of the nanocomposites were improved. Dielectric constant and tan δ were decreased with increasing frequency and ZIF-8 concentration. The tensile strength and modulus of the PLA/ZIF-8 film containing 1wt% ZIF-8 were about 56.83 MPa and 4.04MPa, respectively. UV-vis transmittance spectra and photographs of the nanocomposites showed that all films had good transparency. The flame retarded results revealed that ZIF-8 can be used as an efficient flame retardant and may be active both in the condensed and vapor phase. Based on comprehensive performance of the prepared nanocomposites, we assumed that PLA-3 is the optimal formulation, which has good electrical, transparency, mechanical properties and the best flame retardancy. Therefore, it could be applied to disposable electronics. Acknowledgements This work was supported by Science and Technology Support Program (Social Development) of Jiangsu Province of China (BE 2013714) and Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD). References (1) Ramesh, B. B.; Parande, A. K.; Ahmed, B. C. Electrical and electronic waste: a global environmental problem. Waste. Manage. Res. 2007, 25, 307-318. (2) Ongondo, F. O.; Williams, I. D.; Cherrett, T. J. How are WEEE doing? A global review of the management of



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Acrylonitrile–Butadiene–Styrene

Terpolymer with Metal Hypophosphites: Flame Retardance and Mechanism Research. Ind. Eng. Chem. Res. 2014, 53, 2299-2307.



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Degradable Poly(lactic acid) - American Chemical Society

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