DSpace at VNU: Enhanced mechanical and thermal properties of recycled ABS nitrile rubber nanofil N15 nanocomposites

DSpace at VNU: Enhanced mechanical and thermal properties of recycled ABS nitrile rubber nanofil N15 nanocomposites tài...

Enhanced Mechanical and Thermal Properties of Recycled ABS/Nitrile Rubber/

Nanofil N15 Nanocomposites

Nguyen Dang Mao, Tran Duy Thanh, Nguyen Thi Thuong, Anne-Cécile Grillet, Nam

Hoon Kim, Joong Hee Lee, Prof

PII: S1359-8368(16)30063-4

DOI: 10.1016/j.compositesb.2016.03.039

Reference: JCOMB 4140

To appear in: Composites Part B

Received Date: 27 November 2015

Revised Date: 25 January 2016

Accepted Date: 13 March 2016

Please cite this article as: Mao ND, Thanh TD, Thuong NT, Grillet A-C, Kim NH, Lee JH, Enhanced Mechanical and Thermal Properties of Recycled ABS/Nitrile Rubber/Nanofil N15 Nanocomposites,

Composites Part B (2016), doi: 10.1016/j.compositesb.2016.03.039.

This is a PDF file of an unedited manuscript that has been accepted for publication As a service to our customers we are providing this early version of the manuscript The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Nguyen Dang Mao, a Tran Duy Thanh, a,b Nguyen Thi Thuong,c Anne-Cécile Grillet,d Nam

Hoon Kim, b Joong Hee Leeb,e*

*Corresponding author Tel.: 82-63-270-2342; Fax: 82-63-270-2341

E-mail address: jhl@chonbuk.ac.kr (Prof Joong Hee Lee)

-

Abstract: Hybrid materials based on recycled acrylonitrile butadiene styrene (re-ABS) and

nitrile rubber (NBR) upgraded by montmorrilonite nanofil 15 (N15) were prepared by melt processing The morphology and structure of the nanocomposites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM) analyses As revealed by SEM, NBR and N15 were homogeneously dispersed in the re-ABS matrix The XRD and TEM studies demonstrated that N15 was mainly located in the re-ABS matrix in the form of an intercalated-exfoliated mixed structure that led to

an increase of the melting viscosity of the materials The mechanical properties of the nanocomposites showed a good balance when adding 1 phr (parts per hundred parts of resin) of N15 into the re-ABS/NBR (90/10) blend Furthermore, the thermal stability of the nanocomposites was also improved in the presence of NBR and N15

Keywords: A Polymer-matrix composites (PMCs); B Mechanical properties; B Thermal

properties; E Recycling

Blending of immiscible thermoplastics is a traditional tool to balance mechanical parameters, mostly to improve the toughness Various efforts have been focused on the blending of the ABS with soft polymers and elastomers [6-9] Among various usable elastomers, acrylonitrile butadiene rubber (NBR) as known as nitrile rubber has gained much interest because it not only enhances toughness of polymers effectively but also provides required properties for specific applications NBR has been also successfully utilized to yield novel polymeric blends with high performance of chemical resistance [10] and to improve flame retardancy [11] due to the presence of the polar groups on structure

However, in order to obtain good behavior of polymer blending, some crucial parameters, such

as phase separation, interfacial adhesion, and physical and chemical interactions should be considered The properties can be improved by the addition of compatibilizers, which effectively enhances the interfacial adhesion of blends [12-14] In most cases with and without compatibility components, blending also results in a reduction of the modulus value of the

on the affinity between the nanofillers with the matrix and minor phase, nanofillers could preferably locate in the matrix [25-28], in the minor phase [28], or exist at the interfacial region [29, 30] It appears that the best balance of mechanical properties (stiffness and toughness) results from well-dispersed nanofillers throughout both the matrix and interfacial region [31-33].

Clays are really environmentally friendly, readily available in large quantities, low-cost, and exceptional mechanical properties of each individual layer compared to conventional fillers [34] The enhancement of the clay-filled polymer is achieved by breaking down clay particle aggregates into individual nanolayer with 1 nm thickness and 200 nm lateral dimensions at very low content [34] Furthermore, the functional groups attached on the clay surfaces act as effective sites to improve compatibility between clay and polymer [29-33] Therefore, clay has attracted increasing interests for polymer nanocomposites both in academia and industry during last decade

In this work, the first attempt to re-use re-ABS was carried out by combining re-ABS with nitrile butadiene rubber (NBR) and montmorrilonnite nanofil 15 (N15) Although a numerous

of the hybrid material Since the virgin ABS is expensive, these nanocomposites become economically attractive and thus they can be extensively used for the applications required for high mechanical properties and low material cost

2 Experimental methods

2.1 Materials

Recycled ABS (re-ABS) pellets (density of 1.05 g/cm3) from electronic equipment were supplied by Nhua Tai Sinh Co., Ltd (Vietnam) The nitrile-butadien rubber (KNB 35L), a cold emulsion copolymer of acrylonitrile and butadiene (density of 0.98 g/cm3 and 34 wt% bound acrylonitrile), was provided by Kumho Petrochemical Co., Ltd (Korea) Nanofil 15 (N15), a distearyldimethylammonium chloride exchanged montmorrilonite with an average grain size

of 25 µm, was provided by Sued-Chemie AG Co (Germany) Photograph of the samples and chemical structures of the re-ABS, NBR and nanofil N15 are shown in Fig.1

2.2 Preparation of re-ABS, re-ABS/NBR, and re-ABS/NBR/N15

Prior to processing, re-ABS was dried at 80°C for 48 hours The samples of re-ABS, re-ABS/NBR, and re-ABS/NBR/N15 were prepared using an internal mixer (Haake Polydrive, Germany) at 190°C and 45 rpm for 7 min Then, the molten samples were placed in a mold with dimensions of 12 cm x 12 cm x 2 mm and compressed between two hot plates at 190°C under a pressure of 1,500 psi for 5 min The samples were then cooled to room temperature using cooling water Finally, the samples were taken out and cut into suitable shapes for the various

2.3 Measurements and characterizations

Fourier transform infrared (FTIR) spectra were conducted using a NICOLET 6700 spectrometer (Thermo Scientific Co., USA) from 400 to 4,000 cm-1 with a resolution of 1 cm-1

Scanning electron microscopy (SEM) images were used to observe the phase structure in the

polymer blends and nanocomposites Cryo-fractured samples were obtained using liquid nitrogen and were analyzed by SEM (JSM 6600, JEOL Co., Japan) to examine the dispersion

status of NBR and N15 in the re-ABS matrix Transmission electron (TEM) measurements

were carried out on JEM-1400 Philips microscope (JEOL Co., Japan) to investigate the dispersion status of N15 in the resin matrix Specimens were microtomed using a Leica Ultracut UCT Wide angle X-ray diffraction (WAXD) patterns of samples were recorded in a 2θ angular range of 1.5-20° on a D8 Advance diffractometer (Bruker Co., Germany) employing Ni-filtered CuKߙ radiation with a wavelength of 1.54 Å at 40 kV and 40 mA Differential scanning

calorimetric (DSC) measurements were conducted in DSC 1 equipment (Mettler Toledo Inc.,

USA) with a nitrogen flow rate of 30 cm3/min and heating rate of 10oC/min The thermal stability of the samples was carried out using TGA Q500 analyzer (TA Instruments Ltd., USA) All samples were heated under a nitrogen atmosphere in the temperature range of 25-700 oC at a heating rate of 10 oC/min

The tensile strength of all samples was evaluated by an AG-Xplus Series Precision Universal Tester (Shimadzu Inc., Japan) For the tensile test, the samples were prepared according to the ASTM D638 (type IV) standards All samples were kept in a desiccator under vacuum for 24 hour before the measurements At least 8 specimens were tested for each composition to obtain mean values of mechanical parameters by employing statistical analysis

The impact strength of all samples was measured according to ASTM D256 standards, using

a Model IT504 Impact Tester (Tinius Olsen Inc., USA) At least 8 notched test specimens for each composition were used for Izod measurement The impact strength value is calculated as the ratio of impact energy absorption to cross-section area of test specimen The impact strength (toughness) indicates the ability of a material to absorb shock and impact energy before breaking

The rheological properties of polymers provide necessary information of flow behavior regarding their process-ability Thus, the torque-rheometer analysis is an effective method to qualitatively study melt viscosity, viscosity-temperature dependence, degradation, and crosslinking of polymer based materials such as polymer blends, composites, and nanocomposites In this work, the torque values are monitored as a function of time during the melt mixing of materials using the Hakee Polydrive under typical processing conditions The torque essential to rotate the blades is measured using a dynamometer in terms of the viscosity of materials

3 Results and Discussion

3.1 Morphology and mechanical performance of the re-ABS/NBR blend

The mechanical properties of the re-ABS/NBR blends with the various NBR contents are shown in Fig 2 The tensile modulus and strength were found to decrease remarkably with the addition of NBR into the re-ABS matrix (Fig 2A) This behavior generally occurs in polymer blends based on the addition of an elastomer into a thermoplastic matrix because of the soft nature and diluting effect of the disperse phase [6-9] In contrast, the addition of NBR caused a significant improvement of the impact strength of the blend (Fig 2B) In particular, the impact strength of the blends increased and reached a maximum value of 52.7 KJ/m2 at a NBR of 10 wt% when compared to neat re-ABS (34 KJ/m2) In order to determine the possible reasons

3.2 Morphology, structure, and properties of re-ABS/NBR/N15 nanocomposites

3.2.1 Mechanical performance

Fig 4 shows the mechanical properties of the re-ABS/NBR blend and re-ABS/NBR/N15 nanocomposites with different N15 contents (1, 3, and 5 phr) The addition of N15 into the re-ABS/NBR blend resulted in a significant change of the mechanical behavior of the nanocomposites The tensile modulus of the nanocomposites was improved compared to that of the re-ABS/NBR (90/10) blend and it tended to increase when the N15 content was increased from 1 to 5 phr This result could be a consequence of the hindering effect on the mobility of matrix chains [39] and the high mechanical parameter of rigid nanofillers [40].In addition, the tensile strength and impact strength of the nanocomposites also increased and the best value was obtained with 1 phr N15 The values of the tensile strength and impact strength were 6% and 8% higher, respectively, compared to the re-ABS/NBR (90/10) blend These results are in

observed in studies conducted by Deeptimayee Mahanta et al and Mohammad Rahimi et al to

recycle ABS [41, 42]

3.2.2 XRD analysis

XRD was employed to evaluate the dispersibility of N15 in the nanocomposites (Fig 5) The observation of dispersion and distribution of N15 can help in understanding the mechanism for the morphological change with the addition of N15 The primary diffraction of neat N15 was observed at 2.75o, corresponding to an interlayer spacing of 3.23 nm In the case of the re-ABS/N15 and NBR/N15 nanocomposites (Fig 5A), the diffraction positions respectively appeared at 2.50 o and 2.26 o which were lower than that of neat N15, indicating that NBR and ABS chains are intercalated into the interlayer spacing of the N15 tactoids [39] This also implies that N15 exhibited a slightly, although not significantly, better affinity with NBR than the re-ABS chains In the case of re-ABS/NBR/N15 nanocomposites, the diffraction position shifted toward lower angles for all nanocomposites when compared to that of N15, exhibiting

an increased d-spacing (Fig 5B) These results indicate that polymer chains were intercalated between the clay galleries to form an intercalated structure Furthermore, it was observed that the d-spacing in the intercalated tactoids depends on the N15 loading and the best value was obtained with 1 phr N15 Poorer dispersion of N15 occurred when the clay loading was

3.2.3 TEM and SEM analyses

In order to investigate the detailed dispersion status of N15, TEM and HR-TEM characterizations of the nanocomposites with 1, 3, and 5 phr N15 were carried out and the results are shown in Fig 6 For the nanocomposites containing 1 phr (Fig 6A, D, and G) and 3 phr (Fig 6B, E, and H) N15, the dark lines represent the N15 layers which appear to be well dispersed throughout the matrix resin Exfoliation of the individual layers and intercalated layers were observed This reveals that intercalated-exfoliated mixed structures were formed within the resin However, the layers were rather intercalated and a reduced exfoliation state was observed for the nanocomposites with 3 phr N15 (Fig 6B, E, and H) In particular, some larger intercalated tactoids and the formation of aggregates were observed in the nanocomposites with 5 phr N15 (Fig 6C, F, and K)

Furthermore, the fractured surfaces of the re-ABS/NBR/N15 nanocomposites containing 1, 3, and 5 phr N15 were also evaluated by SEM, as shown in Fig 7 The addition of N15 into the re-ABS/NBR blend caused an evident effect on the phase morphology of the blends It was determined that the distributive size of the NBR component was not noticeable Furthermore, an increase of the roughness of the surface was observed because of the homogeneous dispersion status of N15 particles within the blend This morphological characteristic was similar to results

recently reported by Kim et al [39]

3.2.4 Torque analysis

Fig 8 shows the torque values as a function of time for re-ABS, re-ABS/NBR, and re-ABS/NBR/N15 nanocomposites containing 1, 3, and 5 phr N15 obtained while mixing in the Hakee Polydrive It can be seen that the torque values were constant after the seventh minute of processing for all samples, indicating that homogeneous nanocomposites were

of the N15 dispersion in the polymer matrix At 3 and 5 phr, it seems that the agglomerates of N15 were large enough to restrict interactions between nanofillers and polymer chains Therefore, this led to a reduction of the lubricating effect of nanofillers as well as an increase

of the effect of the formation of the nanomaterial network in the nanocomposite, which favors

an increase of the viscosity [43] The change of the melting viscosity of a polymer due to adding N15 into blends may also effectively facilitate well dispersion of NBR in the re-ABS matrix during the mixing process [39] as shown in Fig 7

3.2.5 FT-IR analysis

The FT-IR technique was used to study the interaction between NBR and re-ABS in the re-ABS/NBR blends with and without N15 The FT-IR spectra of the re-ABS, NBR, N15, re-ABS/NBR (90/10), re-ABS/NBR/N15 (90/10/1), and re-ABS/NBR/N15 (90/10/3) samples

in the wavenumber range of 800-4000 cm-1 are shown in Fig 9 In the case of re-ABS, the spectrum showed a sharp and intense band at 2928.7 and 2239.5 cm-1, corresponding to the vibration of the -CH and -CN group [42] The characteristic bands at 1495.0 cm-1 and 966.0

cm-1 are due to the specific C=C stretching of the benzene ring and =CH stretching, respectively [44] Furthermore, a certain level of degradation was found in the IR spectrum of the re-ABS due to the existence of carbonyl groups at around 1776 cm-1 and hydroxyl groups

at around 3,461 cm-1 [45-47] The ester groups generated during degradation was also

corresponding to -CH stretching, -CN stretching of the nitril group and =CH stretching, respectively [49] The FT-IR spectrum of the N15 shows three main bands at 3625.9 (*), 2928.7 (♦) and 1028.9 (•) cm-1 which are attributed to the Si-OH stretching, -CH stretching from modifier, and Si-O-Si stretching, respectively [50] In the case of the re-ABS/NBR blend and re-ABS/NBR/N15 nanocomposites, the very low intensity of the ester groups and the disappearance of the carbonyl groups and hydroxyl groups indicated that the addition of NBR and N15 filler into re-ABS enhanced the thermal stability of the materials The change of the peak position of -CN and =CH vibrations as compared to pure re-ABS was not clear in the re-ABS/NBR blend However, in the case of the re-ABS/NBR/N15 nanocomposites, the peak positions of the -CN and =CH vibrations in re-ABS shifted by about 6 and 5 cm-1, respectively, towards the higher energy region when compared to that of pure re-ABS and the re-ABS/NBR blend This may be attributed to the enhanced interaction between re-ABS and NBR phases in re-ABS/NBR/N15 nanocomposites [51, 52] due to presence of N15, which facilitates finer dispersion of NBR into re-ABS, as observed in the SEM images in Fig 7

3.2.6 DSC analysis

Fig 10 shows the glass transition temperatures (Tg) of the various systems and the results are also summarized in Table 2 The phase separation of the system was characterized by the change of the Tg of re-ABS In the case of the re-ABS/NBR (90/10) blend, a reduction of Tg

was observed due to the partial compatibility between NBR and the re-ABS matrix, as shown in SEM images in Fig 3B and D In the case of the re-ABS/NBR/N15 nanocomposites, the reduction of Tg was significant for all N15 contents when compared to re-ABS and the

3.2.7 TGA analysis

The thermal properties of re-ABS, the re-ABS/NBR blend, and re-ABS/NBR/N15 nanocomposites are presented in Fig 11 Fig 11A clearly shows that neat re-ABS exhibits the lowest thermal stability compared to the re-ABS/NBR blend and nanocomposites Decomposition of neat re-ABS began at 380 oC, whereas the degradation temperatures of the other samples started around or above 400 °C Therefore, the TGA results obviously indicate that the thermal stability of re-ABS was dramatically improved with the addition of NBR and N15 The corresponding derivative TGA (DTG) curves of all samples are also presented in Fig 11B The re-ABS sample showed the lowest peak positon of the maximum weight loss temperature (Tmax) among all samples With the incorporation of NBR and N15 into re-ABS, the peak position shifted to higher temperatures These results further confirmed that the thermal stabilities of the blend and nanocomposites were enhanced The mechanism of this behavior was suggested to be similar to the case of Dikobe’s research [56] A probable reason

of the lower thermal stability of re-ABS can be explained in terms of the presence of numerous

5 phr N15 increased by about 4, 5, and 3oC, respectively, when compared to that of the re-ABS/NBR blend This was also previously observed where this behavior was demonstrated

to be due to the oxygen and heat barrier mechanism of nanofillers [57, 58] However, NBR seems to be the predominant factor supporting the enhanced thermal behavior of such nanocomposites

[3] Arnold JC, Alston S, Holder A Void formation due to gas evolution during the recycling

of Acrylonitrile-Butadiene-Styrene copolymer (ABS) from waste electrical and electronic

equipment (WEEE) Polym Degrad Stabil 2009; 94: 693-700

[4] Bai X, Isaac DH, Smith K Reprocessing acrylonitrile–butadiene–styrene plastics: structure–property relationships Polym Eng Sci 2007; 47: 120-30

acrylonitrile–butadiene–styrene (ABS) blends Polym Degrad Stabil 2002; 76: 425-34

[7] Sithornkul S, Threepopnatkul P Morphology of Electrospun Natural Rubber with

Acrylonitrile-Butadiene-Styrene Adv Mater Res 2009; 79-82: 1583-6

[8] Wu DY, Bateman S, Partlett M Ground rubber/acrylonitrile-butadiene-styrene

composites Compos Sci and Tech 2007; 67: 1909-19

[9] Zhang N, Bao XX, Tan ZY, Sun SL, Zhou C, Yang HD, Zhang HX Morphology and mechanical properties of ABS blends prepared from emulsion-polymerized PB-g-SAN

impact modifier with AIBN as initiator J Appl Polym Sci 2007; 105: 1237-43

[10] Ismail H, Supri, Yusof AMM Blend of waste poly(vinylchloride) (PVCw)/acrylonitrile butadiene-rubber (NBR): the effect of maleic anhydride (MAH) Polym Test 2004; 23: 675-83

[11] Mousa A, Ishiaku US, Ishak ZAM The effect of prolonged thermo-oxidative ageing on the mechanical properties of dynamically vulcanized Poly(Vinyl Chloride)/Nitrile butadiene rubber thermoplastic elastomers Int J Polym Mater Po 2005; 55: 235-53

[12] Wei D, Hua J, Wang Z Dynamically vulcanized acrylonitrile-butadiene-styrene terpolymer/nitrile butadiene rubber blends compatibilized by chlorinated polyethylene J Appl Polym Sci 2014; 131:1-8

[13] Patel AC, Brahmbhatt RB, Sarawade BD Devi S Morphological and mechanical

properties of PP/ABS blends compatibilized with PP-g-acrylic acid J Appl Polym Sci

2001; 81: 1731-41

[14] Kum CK, Sung YT, Kim YS, Lee HG, Kim WN, Lee HS, Yoon HG Effects of compatibilizer on mechanical, morphological, and rheological properties of

[16] Quaresimina M, Bertani R, Zappalorto M, Pontefisso A, Simionato F, Bartolozzi A Multifunctional polymer nanocomposites with enhanced mechanical and anti-microbial

properties Compos Part B-Eng 2015; 80: 108-15

[17] Zhang X, Wang J, Jia H, You S, Xiong X, Ding L, Xu Z Multifunctional nanocomposites between natural rubber and polyvinyl pyrrolidone modified graphene Compos Part B-Eng 2016; 84: 121-9

[18] Uddin ME, Layek RK, Kim NH, Hui D, Lee JH Preparation and properties of reduced graphene oxide/polyacrylonitrile nanocomposites using polyvinyl phenol Compos Part B-Eng 2015; 80: 238-45

[19] Dueramae I, Jubsilp C, Takeichi T, Rimdusit S High thermal and mechanical properties enhancement obtained in highly filled polybenzoxazine nanocomposites with fumed silica Compos Part B-Eng 2014; 56: 197-206

[20] Schlea MR, Meree CE, Gerhardt RA, Mintz EA, Shofner ML Network behavior of thermosetting polyimide/multiwalled carbon nanotube composites Polymer 2012; 53: 1020-7

[21] Reddy KR, Sin BC, KS Ryu, Kim JC, Chung H, Lee Y Conducting polymer functionalized multi-walled carbon nanotubes with noble metal nanopartcles: Synthesis, morphological characteristics and electrical properties Synthetic Met 2009; 159: 595-603