Evaluation of Interactions Between Compatibilizers and Photostabilizers in Coir Fiber Reinforced Polypropylene Composites.
Nowadays, there has been a search for economically viable and sustainable products in different market segments. Lighter materials that can be recycled have become a strategic issue for many industries, which seek the development and manufacturing of products that meet the economic expectations of the company, and contribute to the preservation of the environment. In this context, natural fibers (especially, lignocellulosic fibers) have stood out as potential substitutes of synthetic fibers due to the fact that they are abundant, non-abrasive (which reduces the wear on processing equipment), have low relative density and low cost, in addition to being recyclable, biodegradable and having excellent specific mechanical properties, offering a wide range of reinforcing properties because the numerous sources of collection [1-4].
Due to the benefits of using natural fibers, the academic and technological studies have advanced over the past few decades. These studies have shown that due to the low degradation temperatures of lignocellulosic fibers, the matrices used should be limited to polymers with melting temperatures lower than their degradation temperature (around 200[degrees]C), such as polypropylene (PP), polyethylene (HDPE or LDPE), poly(lactic acid), among others. In the case of polyolefins, the differences between the polarities of polymers (apolar) and lignocellulosic fibers (polar) create the need to use compatibilizers and/or coupling agents, or surface treatments to the fibers, to make their phases compatible. Performance of a composite can be improved by increasing the mechanical stress transfer from the polymer matrix to the fiber, which has greater mechanical strength and will, therefore, reinforce the polymer. When polypropylene is used as matrix, improved adhesion has been obtained mainly by adding compatibilizers, such as polypropylene grafted with maleic anhydride (PPMAH) [2-8].
The addition of a compatibilizer favors the processing and improves the dispersion of fibers in the polymer matrix, in addition to reducing composite water absorption and increasing tensile strength, bending strength and the mechanical properties in the long term, such as fatigue [9, 10]. However, increasing the concentration of compatibilizers is not sufficient to increase the mechanical properties, reaching a percentage limit, depending on the matrix and the reinforcement . There is therefore optimal relative concentrations of coir fiber/compatibilizers. High levels of coir fiber require higher concentrations of compatibilizers, according to Ayrilmis , who studied coir fiber reinforced polypropylene composites hot-pressed, in which the coir fiber content varied between 40 wt% and 70 wt% and the compatibilizer concentration was fixed at 3wt%. The authors show that increasing of concentration of fibers increased mechanical properties such as tensile and flexural strength up to 60 wt% with subsequent reduction.
Among the possible alternatives to increase interfacial adhesion between matrix polymer and coir fiber, is the chemical treatment of the fibers [12, 13]. Zaman and Beg  evaluated the effect of coir fiber content and treatment with stearic acid on the properties of unidirectional coir fiber reinforced polypropylene composites obtained by compression molding and found that the chemical treatment was efficient in enhancing mechanical properties such as tensile strength, impact resistance and reducing water absorption.
The use of these composites in outdoor applications, both in the automotive and construction industries, requires that these materials are resistant to weathering in the long term, especially to UV radiation. However, both the polymer and the fiber components (cellulose, lignin and hemicellulose) undergo photooxidative degradation. Wood-Plastic (HDPE and PP) composites (WPC) were evaluated during their natural and accelerated aging and it has been observed an intense degradation in these composites, evaluated in terms of mechanical properties, scanning electron microscopy (SEM) analysis and color changes [14-17]. In order to prevent and/or reduce the effects of photo-oxidative aging on the properties of lignocellulosic fiber reinforced composites, stabilizing additives, such as hindered amines light stabilizer (HALS), UV absorbers and light screeners have been added and their effects were analyzed after aging [16. 18-23].
Stark and Matuana  evaluated the effect of adding UV absorbers and pigment (zinc ferrite pigment) on the lightness and flexural properties, when HDPE/WF (wood flour) composites were submitted to accelerated aging in xenon-arc-type light exposure apparatus. According to the authors, the results showed that both ultraviolet absorbers and pigments provide protection against weathering of wood plastic composites. Different pigments were evaluated as light screeners in the outdoor weathering of PP/wood composites compatibilized with PPMAH [20, 21]. Composites containing darker pigments indicated greater color stability, and those with larger amounts of wood flour indicated higher surface deterioration, observed by scanning electron microscopy (SEM). Muasher and Sain  compared the performance of different hindered amines light stabilizer and UV absorbers as photostabilizers in HDPE/wood composite, when subjected to natural weathering for 2,000 h. As a result, the composites experienced color fading and yellowing. The authors suggested that the formation of paraquinones, from lignin redox reactions, and their conversion into hydroquinones would be the possible causes of the greater photodegradation of the composites. Diester-based HALS would have no initial action in suppressing the formation of paraquinone chromophoric groups, but would be effective in capturing the free radicals formed and reduce the formation of hydroquinones, thus reducing photobleaching. A synergistic effect was observed in the reduction in color fading when both stabilizers, UV absorbers and diester-based HALS, were added to the composites.
PP/date palm fiber composites, uncompatibilized and compatibilized with PPMAH, underwent natural and accelerated weathering and HALS-based stabilization systems were evaluated . According to the authors, the composites were more stable than the PP, under severe aging conditions, both natural and accelerated. In addition, uncompatibilized composites showed higher stability than those compatibilized with PPMAH. The evaluated stabilizers appeared to be efficient stabilizers.
In order to evaluate and understand the influence of photo stabilizers in the aging of coir fiber reinforced polypropylene composites, as well as their possible interactions with the compatibilizer, PPMAH. a systematic study was conducted, which evaluates the influence of a hindered amine light stabilizer (HALS) and/or a UV absorber, in the presence and absence of PPMAH, in the mechanical, morphological and optical properties. The research will be divided into three parts, and, in this study, the influence of these additives will be evaluated in short-term tests in order to check whether the presence of these additives affect these properties. Weathering methods, both in Xenon Equipment (xenon lamps) and Q-UV (ultraviolet B lamps), will be presented subsequently.
MATERIALS AND METHODS
Polypropylene homopolymer, under code HP550K (melt flow rate = 3.5 g/10 min), was supplied by Braskem. All formulations were stabilized with 0.2% of Irganox B 215, a 2:1 blend of Irgafos 168 (secondary antioxidant based on phosphite--hydro peroxide decomposer) and Irganox 1010 (phenolic antioxidant, Hdonor). The coir fiber was supplied by Inbrasfama, in milled condition, with suitable size distribution (Lw/Ln=1.6) and without chemical treatment. Average measurements of tensile strength and elongation at break of coir fiber were 109.2 MPa and 9%, respectively, as determined in previous study ,
The compatibilizer used was maleic anhydride grafted polypropylene, PPMAH, under code Polybond 3200 (MFI 110 g/10 min at 190[degrees]C and 2.16 kg and nominal content of maleic anhydride of 1.0%, in mass), supplied by Crompton-Uniroyal Chemical.
The UV light stabilizing additives used were Tinuvin 791, supplied by BASF [R], and Hostavin ARO 8, supplied by Clariant [R] Tinuvin 791 is a commercial blend of two hindered amines light stabilizers (HALS), with different molar masses: Chimassorb [R] 944 (Mn = 2,000-3,100 g/mol) and Tinuvin 770 (Mn = 481 g/ mol). The additive Hostavin ARO 8 (2-Hydroxy-4-n-octyloxybenzophenone) is a benzophenone-based UV stabilizer. The chemical structures of the additives are presented in Fig. 1.
Preparation of the PP/Coir Fiber Composite
The composites were prepared in a co-rotating twin-screw extruder IMACOM, model DRC 30:40 IF, with L/D = 40 and a 30 mm screw diameter. The processing conditions were as follows: temperature profiled 10[degrees]C, I30[degrees]C, 180[degrees]C, 185[degrees]C, 190[degrees]C, 190[degrees]C, 190[degrees]C, 185[degrees]C, 185[degrees]C e 190[degrees]C; screw rotation of 200 rpm and mass flow rate of 12kg/h. The coir fibers have been previously dried at 80[degrees]C for 4 h.
Table 1 shows the compositions of the formulations studied. As mentioned above, all formulations were additionally stabilized with 0.2% of Irganox B 215 (2:1 blend of Irgafos 168 and Irganox 1010).
Type 1 tensile specimen, according to ASTM D638:2014, were injected into an injection machine ROMI PRATICA 130, with 50 mm diameter, 130 t clamping force and maximum torque of 80kgf.m, coupled to a mold cooling and heating unit. The composites were dried for 4 h at a temperature of 80[degrees]C and injected under the following conditions: temperature profile of 75[degrees]C, 180[degrees]C, 180[degrees]C, 190[degrees]C and 190[degrees]C; 80 bar injection pressure, volumetric flow rate of 30 [cm.sup.3]/s, mold temperature of 50[degrees]C, cooling time of 25 s and 6 bar counter-pressure.
Mechanical, Thermal and Morphological Characterization
Tensile tests were performed in a Universal Testing Machine EMIC DL 10000, following ASTM D638 standard, with a speed of 5 mm/min. The cryo-fractured surfaces of the specimen of the composites obtained were previously coated with a thin layer of gold and evaluated by scanning electron microscopy (SEM), in an FEI Inspect S50 microscope. Thermal analysis were performed by Differential Scanning Calorimetry in DSC Q100 of TA Instruments under the following thermal program: heating from 30[degrees]C to 190[degrees]C at 10[degrees]C/min; 3 min isotherm; cooling from 190[degrees]C to 30[degrees]C at 10[degrees]C/min; re-heating from 30 to 190[degrees]C at 10[degrees]C/min. Degree of crystallinity of the samples was calculated from melting enthalpy ([DELTA][H.sub.m]) of each sample using Equation 7, where [[chi].sub.PP] is the mass fraction of PP in the composites, ([DELTA][H.sup.0.sub.m] the melting enthalpy for hypothetically 100% crystalline PP ([DELTA][H.sup.0.sub.m] = 209 J/g) .
%C = [DELTA][H.sub.m]/[[chi].sub.PP][DELTA][H.sup.0.sub.m] (1)
The effects of the presence of coir fiber, compatibilizers and the several additives on the mechanical e thermal properties were evaluated by analysis of variance (ANOVA) and Tukey's multiple comparison test. All statistical analyses were performed using 5% significance level (a = 0.05).
Evaluation of the Interaction between Additives (FTIR)
In order to investigate the possible interactions and/or reactions between compatibilizer (PPMAH) and hindered amine stabilizers (Tinuvin791), four formations without coir fiber were studied, as shown in Table 2. The compositions were obtained in a torque rheometer (ThermoScientific Haake Polylab QC Rheometer), equipped with a Rheomix 600QC/QC610 mixing chamber, roller-type rotors, at the following process conditions: temperature 180[degrees]C, rotation of 100 rpm and reaction time 2 min. After processing in the rheometer, the samples were pressed into films in a hotpress at 200[degrees]C and 2 ton. In order to assess possible reactions/interactions, the samples was analyzed by infrared spectroscopy in a Nicolet 4700 FTIR spectrophotometer (Thermo Scientific) with a resolution of 2 [cm.sup.-1] and 128 scans per spectrum.
RESULTS AND DISCUSSION
Table 3 shows the results of tensile tests, after the composition process in the extruder, of the polypropylenes (Group 1) and coir fiber reinforced PP composites, uncompatibilized (Group 2) and compatibilized with PPMAH (Group 3).
As it can be seen in Table 3, the incorporation of coir fibers into polypropylene, in the absence of compatibilizer, causes reductions in the tensile strength and elongation at break and the increase in the tensile modulus for significance level of 5%. Although the coir fiber present higher strength than the PP matrix, the chemical and polarity differences between the components do not allow an adequate load transfer between the phases and thus, the fibers act as stress concentrators, which can be seen by the tensile strength reduction. Furthermore, the incorporation of the coir fibers reduces the mobility of PP chains, making them more rigid, regardless of whether or not there is adhesion between the phases.
As it can be seen by comparing the samples of Group 2 and Group 3 in Table 3, adding the compatibilizer (PPMAH) to the PP/CF composites increases the adhesion between the phases of PP and coir fibers, and consequently, it increases tensile strength due to the adequate load transfer between phases, since it is a maleic anhydride grafted polypropylene, whose anhydride phase may react and/or interact with the hydroxyls of the fiber surface. These results show the importance of incorporating compatibilizers in incompatible systems, using PP as the matrix, as it has been extensively shown in the literature[3, 6, 9, 10].
These facts can be corroborated by the scanning electron microscopy images, shown in Fig. 2. As it can be seen by the micrographs (a) and (c), uncompatibilized PP/CF composites present voids, caused by pullout of the fibers from PP matrix, indicating poor fiber-matrix adhesion (as evidenced by the fibers outside the break plan). In contrast, PP/FCo composites, compatibilized with PPMAH (micrographs (b) and (d)), indicate fibers well adhered to the matrix, ruptured flush with the polymer surface, showing no disengagement, confirming the tensile strength results caused by the appropriate transfer between phases.
As to the tensile modulus, it can be seen that, by adding the PPMAH, the tensile modulus does not statically significant for [alpha] = 0.05. This result is in line with previous studies [7, 25, 26] that found that the rigidity of these composites is not significantly affected by the adhesion between the phases.
Table 3 show that adding stabilizers HALS and/or UV absorbers to the uncompatibilized PP/FC composites does not significantly change the tensile strength of the composites. However, when analyzing the PP/FC composites, compatibilized with PPMAH, it can be seen that the presence of the hindered amine light stabilizer (HALS, Tinuvin" 791) reduces tensile strength significantly by approximately 14% and 17%, when HALS is the only additive and when both HALS and UV absorber are incorporated into the composite, respectively. With respect to the other properties, the elongation at break is significantly reduced when the amines are incorporated into the compatibilized composites, but tensile modulus is not changed statically.
To understand the reasons underlying the changes in mechanical properties, we investigated two hypotheses:(a) the change of properties would be the result of changes in the degree of crystallinity of composites in the presence of additives or (b) reactions and/or interactions between the compatibilizer and the hindered amine light stabilizer would be reducing the compatibilizing effect through the inactivation of the compatibilizer.
To analyze the first hypothesis, DSC analyses were conducted and the results are shown in Table 4.
In order to evaluate whether possible variations in the degree of crystallinity would have an effect on the tensile properties of the formulations with the addition of the various types of additives, the analyses were first evaluated in the first heating. As it can be seen, the variations of the degree of crystallinity, within the Group 3 (with the variation of the type of additive), are very small, and statically equal (for the significance levels of 5%), and cannot be responsible for the changes in tensile strengths (within the Group 3) shown in Table 3. Therefore, this hypothesis was discarded.
To evaluate the influence of the incorporation of fibers, compatibilizer and additives in the degree of crystallinity and Tm we also evaluated the analyses of these quantities in the second heating. By analyzing Table 4, it can be seen that, the melting temperature experienced no significant changes between the formulations studied. There has been a slight increase in the composite crystallization temperature after adding coir fiber and compatibilizer. In addition, both uncompatibilized and compatibilized composites indicated higher degree of crystallinity in relation to polypropylene, and these increases were higher for compatibilized composites.
Several studies [27-29] have shown that adding natural fibers to PP increases the crystallization temperature (Tc) and the degree of crystallinity of PP due to heterogeneous nucleation, which induces crystallization in the polymer matrix. The polymer crystallization on the fiber surface is called transcrystallinity. This effect is more pronounced in compatibilized composites, mainly due to the increased interactions between the fiber and the matrix . Harper and Wolcott  showed that the presence of wood fiber in polypropylene blends has a effect on the crystallization and morphology of the matrix crystals, providing surface area for nucleation of polypropylene crystals in a different morphology. Furthermore, the addition of compatibilizers in composites leads to increased nucleation on the surface of the wood fiber.
By observing the degree of crystallinity of PP/CF/PPMAH composites, without additives and with the HALS-type additive, it can be seen that in the presence of the additive there is a small reduction in the degree of crystallinity, when measured on the second heating. This small difference could contribute to a lower composite strength. However, the same behavior was not noticed when the analyses were conducted in the injected specimen, during the first heating, which would be the appropriate assessment when evaluating tensile strength properties.
To evaluate the hypothesis that a reduction in tensile strength could be associated with some sort of reaction and/or interaction between HALS, which is a hindered amine light stabilizer, and the compatibilizer PPMAH, which is a maleic anhydride grafted he polypropylene, reducing action thereof, the adhesion between phases was verified through scanning electron microscopy analyses of the fractured surfaces of uncompatibilized and compatibilized composites and through infrared analysis.
The micrographs obtained via SEM are shown in Fig. 3. As it can be seen, the inclusion of Tinuvin[R] 791 (HALS), reduces the adhesion between PP and coir fiber phases (Fig. 3b and e). Although the presence of compatibilizer (PPMAH) causes a significant improvement in the adhesion between phases (Fig. 3df), it can be seen that adding amine (HALS) to the compatibilized composite, PP/CF/PPMAH (Fig. 3e), reduces the adhesion of the fibers in the PP matrix, as evidenced by the presence of voids between the fibers and by fiber pullout from the matrix. When the UV absorber additive is added to the PP/CF composite compatibilized with PPMAH, it does not affect the adhesion, as shown in Fig. 3f, when compared to the PP/CF/PPMAH composite, without additives (Fig. 3d).
Thus, it was supposed that the tensile strength reduction in the compatibilized composites is mainly caused by possible interactions and/or reactions of the compatibilizer, PP-g-MAH, with the sterically hindered amine.
Reactions between the amine group of the stabilizer (Tinuvin[R]) and succinic anhydride/succinic acid of the compatibilizer (maleic anhydride grafted polypropylene) are possible at high temperatures, such as those at which the preparation of the composites were conducted. These reactions or interactions between such groups could reduce the effectiveness of both additives, thus reducing the adhesion due to the reduction in the effective concentration of the compatibilizer and the efficiency of amine as a stabilizer to weathering.
Seeking to look for evidence of reactions and/or interactions between succinic anhydride/succinic acid and amine groups, samples of PP, PP/PPMAH, PP/TIN (HALS) and PP/PPMAH/ TIN (HALS) were processed in Haake Torque Rheometer at the same processing temperature and with the same concentrations used; films of these samples were obtained through pressing and analyzed via infrared. Figure 4 shows the infrared spectrum for the formulations processed, in the region of interest (1,860 [cm.sup.-1] and 1,515 [cm.sup.-1]). As it can be seen, the infrared spectra of the various samples are very similar, differing primarily by the absorption of carbonyl at 1,737 [cm.sup.-1] and a peak at 1,633 [cm.sup.-1]. Absorbance at wavenumber 1,737 [cm.sup.-1] refers to the ester carbonyl stretching vibrations and appears in the PP + Tinuvin and PP + Tinuvin + PPMAH samples. As shown in Fig. 1, Tinuvin 770 is a hindered amine light stabilizer, which has ester bond, and therefore, the spectrum of the samples in which this additive is present indicates ester carbonyl vibration. In the spectrum containing both additives, Tinuvin (HALS) and compatibilizer (maleic anhydride grafted polypropylene, PPMAH), the absorption is at 1,633 [cm.sup.-1], which does not appear in the other formulations. Although this variation is small, it may be an indication of tertiary amide formation.
Hindered amines light stabilizers are efficient additives because they have H labile, bonded to N, which is easily abstracted by thermal energy or radiation. In the presence of oxygen, they form nitroxyl radicals that are able to capture the polymer radicals generated during the degradation.
The assertion that anhydride/succinic acid of PPMAH may have reacted with amine is hard to confirm, since the system is complex, in which there is, in addition to the additives and materials involved, residuals maleic anhydride and maleic anhydride oligomers, resulting from an inefficient reaction of maleic anhydride grafting in PP, by reactive extrusion, for the production of PPMAH [31, 32]. The presence of maleic acid/anhydride may catalyze possible hydrolysis reactions of esters and therefore reduce the molar mass of Tinuvin, which may lead to other parallel reactions between the acids generated during the hydrolysis with the amine grouping of the additive.
Moreover, it is worth noting that in the formulations prepared in the torque rheometer, we used the same concentrations as those used during the extrusion (0.2% HALS and 3% PPM AH), which generates great difficulty in obtaining more intense spectra. Therefore, there is a suggested reaction or even interaction between the components.
The use of compatibilizers in PP/coir fiber composites is essential for generating adhesion between the composite phases and enhances their tensile strength. In the absence of this additive, natural fibers act as stress concentrators, thereby reducing the tensile strength of the composite in relation to pure PP. The compatibilization of PP composites increases tensile strength by approximately 20% in relation to pure PP and 30% in relation to uncompatibilized PP composites, in formulations without protection additives.
The inclusion of photostabilizing additives, such as HALS, may compromise the mechanical properties of PP/CF composites, compatibilized with maleic anhydride grafted polypropylene, PPMAH, producing composites with tensile strength lower than those obtained without the incorporation of such additives. The same behavior does not occur when PP/CF composites are not compatibilized. The analyses of the mechanical and morphological properties, obtained via SEM, point to a reduced adhesion between the fibers and the matrix when the HALS-type additive is incorporated into the formulation. The presence of the hindered amine light stabilizer in combination with PPMAH, a compatibilizer that contains anhydrides and/or acids, may reduce the efficiency of the latter through the inactivation of part of its groups, which should establish reactions and/or interactions with the hydroxyls of the fibers.
The addition of hydroxybenzophenone UV absorbers, however, does not interfere with the adhesion of PP/CF composites, either compatibilized or uncompatibilized with PPMAH, keeping the mechanical properties at the same levels than in its absence.
The choice of additives in multiphase systems should, therefore, take into account other possible constituents of the system seeking to keep their actions.
[1.] K. Grison, V. Pistor, L.C. Scienza, and A,J. Zattera, J. Appl. Polym. Sci., 133 (2016).
[2.] A. Espert, W. Camacho, and S. Karlson, J. Appl. Polym. Sci., 89, 2353 (2003).
[3.] S.H.P. Bettini, B.C. Bonse, E.A. Melo, and P.A.R. Munoz, Polym. Eng. Sci., 50, 978 (2010).
[4.] S.H.P. Bettini, A.T. Uliana, and D. Holzschuh, J. Appl. Polym. Sci., 108, 2233 (2008).
[5.] M.N. Ichazo, C. Albano, J. Gonzales, R. Perera, and M.V. Candal, Compos. Struct., 54, 207 (2001).
[6.] T. Keener, R. Stuart, and T. Brown, Compos. Part Appl. Sci. Manuf., 35, 357 (2004).
[7.] S.H.P. Bettini, A.B.L.C. Bicudo, I.S. Augusto, L.A. Antunes, P.L. Morassi, R. Condotta, and B.C. Bonse, J. Appl. Polym. Sci., 118, 2841 (2010).
[8.] S.H.P. Bettini, A.C. Biteli, B.C. Bonse, A. de, and A. Morandim-Giannetti, Polym. Eng. Sci., 55, 2050 (2015).
[9.] S.H.P. Bettini, M.C. Antunes, and R. Magnabosco, Polym. Eng. Sci., 51, 2184 (2011).
[10.] M.C. Antunes, D.V.O. Moraes, R. Magnabosco, B.C. Bonse, and S.H.P. Bettini, Polym. Eng. Sci. 53, 2159 (2013).
[11.] N. Ayrilmis, S. Jarusombuti, V. Fueangvivat, P. Bauchongkol, and R.H. White, Fibers Polym., 12, 919 (2011).
[12.] M. Haque, E. Ali, M. Hasan, N. Islam, and H. Kim, Ind. Eng.Chem. Res., 51, 3958 (2012).
[13.] H.U. Zaman and M.D.H. Beg, Fibers Polym., 15, 831 (2014).
[14.] P. Pages, F. Carrasco, J. Saurina, and X. Colom, J. Appl. Polym. Sci., 60, 153 (1996).
[15.] M.D.H. Beg and K.L. Pickering, Polym. Degrad. Stab., 93, 1939 (2008).
[16.] J.S. Fabiyi, A.G. McDonald, M.P. Wolcott, and P.R. Griffiths, Polym. Degrad. Stab., 93, 1405 (2008).
[17.] K. Rajakumar, V. Sarasvathy, A. Thamarai Chelvan, R. Chitra, and C.T. Vijayakumar, J. Polym. Environ., 17, 191 (2009).
[18.] R. Bouza, M.J. Abad, L. Barral, A. Lasagabaster, and S.G. Pardo, J. Appl. Polym. Sci., 120, 2017 (2011).
[19.] M. Muasher and M. Sain, Polym. Degrad. Stab., 91, 1156 (2006).
[20.] S. Butylina, M. Hyvarinen, and T. Karki, Compos. Appl. Sci. Manuf., 43, 2087 (2012).
[21.] S. Butylina, M. Hyvarinen, and T. Karki, Polym. Degrad. Stab., 97, 337 (2012).
[22.] N.M. Stark, and L.M. Matuana, Polym. Degrad. Stab., 91, 3048 (2006).
[23.] B. Abu-Sharkh, and H. Hamid, Polym. Degrad. Stab., 85, 967 (2004).
[24.] W. Kaminsky, Macromol Chem Phys, 209, 459 (2008).
[25.] P. Wambua, J. Ivens, and I. Verpoest, Compos. Sci. Technol., 63, 1259 (2003).
[26.] M.H. Ishizaki, L.L. Visconte, C.R. Furtado, M. Leite, and J.L. Leblanc, Polimeros Cienc. E Tecnol, 16, 182 (2006).
[27.] D. Ndiaye, L.M. Matuana, S. Morlat-Therias, L. Vidal, A. Tidjani, and J.L. Gardette, J. Appl. Polym. Sci., 119, 3321 (2011).
[28.] M. Pracella, M.M.U. Haque, and V. Alvarez, Polymers, 2, 554 (2010).
[29.] P.V. Joseph, K. Joseph, S. Thomas, C.K.S. Pillai, V.S. Prasad, G. Groeninckx, and M. Sarkissova, Compos. Appl. Sci. Manuf., 34, 253 (2003).
[30.] D. Harper, and M. Wolcott, Composites: Part A, 35, 385 (2004).
[31.] S.H.P. Bettini, and J.A.M. Agnelli, J. Appl. Polym. Sci., 74, 247 (1999).
[32.] S.H.P. Bettini, and J.A.M. Agnelli, J. Appl. Polym. Sci., 85, 2706 (2002).
Lucas H. Staffa, (1, 2) Jose Augusto M. Agnelli, (1) Miguel L. de Souza, (2) Silvia H. P. Bettini (1)
(1) Department of Materials Engineering, Universidade Federal de Sao Carlos, Rod. Washington Luiz, km 235, CEP 13565-905, Sao Carlos - SP, Brazil
(2) Newtech Assessoria, Consultoria de Serviqos S/S LTDA, Rua Dom Pedro II, 676, CEP 13560-320, Sao Carlos - SP, Brazil
Correspondence to: S.H.P. Bettini; e-mail: firstname.lastname@example.org
Caption: FIG. 1. Chemical Structures of the additives (a) Tinuvin [R]770, (b) Chimassorb[R] 944 S and (c) Hostavin ARO 8.
Caption: FIG. 2. SEM micrographs of the fractured surfaces of the samples: (a,c) PP/CF and (b,d) PP/CF/PPMAH, with different magnifications.
Caption: FIG. 3. SEM micrographs of the fractured surfaces of the samples: (a) PP/CF, without additives; (b) PP/CF, with Tinuvin 791 (HALS); (c) PP/CF with Hostavin ARO 8 (UV absorber); (d) PP/CF/PPMAH. without additives; (e) PP/ CF/PPMAH with Tinuvin 791 and (f) PP/CF/PPMAH with Hostavin ARO 8.
Caption: FIG. 4. FTIR spectra of the samples: PP (black line); PP/Tinuvin 791 (red line); PP/PPMAH (blue line) and PP/PPMAH/Tinuvin 791 (purple line). [Color figure can be viewed at wileyonlinelibrary.com]
TABLE 1. Nominal composition, in mass, of the formulations. Nomenclature of PP FCo Irganox compositions (%) (Coir Fiber)(%) B214 (%) PP 99.8 -- 0.2 PP/Tin 99.6 -- 0.2 PP/Tin/Hos 99.4 -- 0.2 PP/Hos 99.6 -- 0.2 PP/CF 69.8 30 0.2 PP/CF/Tin 69.6 30 0.2 PP/CF/Tin/Hos 69.4 30 0.2 PP/CF/Hos 69.6 30 0.2 PP/CF/PPMAH 66.8 30 0.2 PP/CF/Tin/PPMAH 66.6 30 0.2 PP/CF/Tin/Hos/PPMAH 66.4 30 0.2 PP/CF/Hos/PPMAH 66.6 30 0.2 Nomenclature of PPMAH Tinuvin 791 Hostavin compositions (%) (%) AR08(%) PP -- -- -- PP/Tin -- 0.2 -- PP/Tin/Hos -- 0.2 0.2 PP/Hos -- -- 0.2 PP/CF -- -- -- PP/CF/Tin -- 0.2 -- PP/CF/Tin/Hos -- 0.2 0.2 PP/CF/Hos -- -- 0.2 PP/CF/PPMAH 3 -- -- PP/CF/Tin/PPMAH 3 -- -- PP/CF/Tin/Hos/PPMAH 3 0.2 -- PP/CF/Hos/PPMAH 3 -- 0.2 Tin = Tinuvin 791 (HALS); Hos = HostavinAro 8 (UV Absorber); PPMAH = Maleic anhydride grafted polypropylene (Compatibilizer). TABLE 2. Formulations obtained in a Haake rheomether. Nomenclature of [C.sub.PP] [C.sub.PPMAH] [C.sub.Tin] compositions (wt.%) (Wt.%) (wt.%) PP 100 -- -- PP/Tin 99.8 -- 0.2 PP/Tin/PPMAH 96.8 3 0.2 PP/PPMAH 97 3 -- TABLE 3. Results of the mechanical properties obtained by tensile tests. Groups Compositions Elongation at break (%) 1 PP > 350 PP/Tin > 350 PP/Hos > 350 PP/Tin/Hos > 350 2 PP/CF 3.69 [+ or -] 0.40 PP/CF/Tin 3.47 [+ or -] 0.12 PP/CF/Hos 3.61 [+ or -] 0.33 PP/CF/Tin/Hos 3.75 [+ or -] 0.29 3 PP/CF/PPMAH 4.71 [+ or -] 0.08 PP/CF/Tin/PPMAH 3.50 [+ or -] 0.14 PP/CF/Hos/PPMAH 4.53 [+ or -] 0.19 PP/CF/Tin/Hos/PPMAH 3.67 [+ or -] 0.25 Groups Compositions Tensile Strength (MPa) 1 PP 35.06 [+ or -] 0.24 PP/Tin 33.63 [+ or -] 0.86 PP/Hos 32.43 [+ or -] 0.31 PP/Tin/Hos 32.08 [+ or -] 0.20 2 PP/CF 30.03 [+ or -] 0.33 PP/CF/Tin 30.19 [+ or -] 0.40 PP/CF/Hos 29.11 [+ or -] 0.06 PP/CF/Tin/Hos 30.10 [+ or -] 0.74 3 PP/CF/PPMAH 43.69 [+ or -] 0.26 PP/CF/Tin/PPMAH 37.53 [+ or -] 0.25 PP/CF/Hos/PPMAH 42.68 [+ or -] 0.31 PP/CF/Tin/Hos/PPMAH 36.35 [+ or -] 0.36 Groups Compositions Tensile Modulus (MPa) 1 PP 1788 [+ or -] 64 PP/Tin 1647 [+ or -] 104 PP/Hos 1583 [+ or -] 27 PP/Tin/Hos 1511 [+ or -] 80 2 PP/CF 2288 [+ or -] 88 PP/CF/Tin 2288 [+ or -] 107 PP/CF/Hos 2193 [+ or -] 54 PP/CF/Tin/Hos 2289 [+ or -] 110 3 PP/CF/PPMAH 2418 [+ or -] 68 PP/CF/Tin/PPMAH 2361 [+ or -] 77 PP/CF/Hos/PPMAH 2210 [+ or -] 172 PP/CF/Tin/Hos/PPMAH 2185 [+ or -] 186 Tin = Tinuvin 791 (HALS); Hos = HostavinAro 8 (UV Absorber): CF = Coir Fiber: PPMAH = Maleic anhydride grafted polypropylene (Compatibilizer). TABLE 4. Melting temperature (Tm), crystallization temperature (Tc) and degree of crystallinity (%C) of the samples. First heating Compositions Tm ([degrees]C) %C PP 167.6 [+ or -] 0.1 41.1 [+ or -] 1.5 PPATin 166.7 [+ or -] 0.4 42.2 [+ or -] 1.9 PP/Hos 166.4 [+ or -] 0.2 43.3 [+ or -] 1.2 PP/Tin/Hos 167.3 [+ or -] 0.9 41.4 [+ or -] 1.9 PP/CF 166.1 [+ or -] 0.5 37.4 [+ or -] 1.5 PP/CF/Tin 165.8 [+ or -] 0.4 36.4 [+ or -] 2.4 PP/CF/Hos 166.2 [+ or -] 0.5 39.9 [+ or -] 2.3 PP/CF/Tin/Hos 165.5 [+ or -] 0.4 39.0 [+ or -] 0.6 PP/CF/PPMAH 165.6 [+ or -] 0.5 40.9 [+ or -] 3.3 PP/CF/Tin/PPMAH 164.9 [+ or -] 1.2 40.6 [+ or -] 4.0 PP/CF/Hos/PPMAH 166.0 [+ or -] 0.2 43.9 [+ or -] 3.4 PP/CF/Tin/Hos/PPMAH 165.8 [+ or -] 0.5 40.0 [+ or -] 3.8 Cooling Second heating Compositions Tm ([degrees]C) Tm ([degrees]C) PP [+ or -] 166.1 [+ or -] 0.2 PPATin 117.8 [+ or -] 0.4 165.0 [+ or -] 0.3 PP/Hos 120.2 [+ or -] 0.5 164.9 [+ or -] 0.2 PP/Tin/Hos 117.5 [+ or -] 0.7 166.1 [+ or -] 0.8 PP/CF 120.3 [+ or -] 0.2 164.7 [+ or -] 0.9 PP/CF/Tin 120.1 [+ or -] 0.4 164.0 [+ or -] 0.4 PP/CF/Hos 120.7 [+ or -] 0.2 164.6 [+ or -] 0.4 PP/CF/Tin/Hos 120.4 [+ or -] 0.1 164.0 [+ or -] 0.4 PP/CF/PPMAH 120.7 [+ or -] 0.2 163.9 [+ or -] 0.6 PP/CF/Tin/PPMAH 119.9 [+ or -] 0.1 164.0 [+ or -] 0.2 PP/CF/Hos/PPMAH 120.9 [+ or -] 0.2 164.2 [+ or -] 0.1 PP/CF/Tin/Hos/PPMAH 120.5 [+ or -] 0.2 164.1 [+ or -] 0.6 Second heating Compositions %C PP 47.2 [+ or -] 0.3 PPATin 47.4 [+ or -] 0.8 PP/Hos 48.6 [+ or -] 2.0 PP/Tin/Hos 51.1 [+ or -] 1.0 PP/CF 52.2 [+ or -] 3.8 PP/CF/Tin 51.2 [+ or -] 0.2 PP/CF/Hos 51.1 [+ or -] 0.4 PP/CF/Tin/Hos 52.9 [+ or -] 4.0 PP/CF/PPMAH 54.0 [+ or -] 3.7 PP/CF/Tin/PPMAH 52.5 [+ or -] 2.6 PP/CF/Hos/PPMAH 57.0 [+ or -] 0.5 PP/CF/Tin/Hos/PPMAH 57.9 [+ or -] 3.6
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|Author:||Staffa, Lucas H.; Agnelli, Jose Augusto M.; de Souza, Miguel L.; Bettini, Silvia H.P.|
|Publication:||Polymer Engineering and Science|
|Date:||Nov 1, 2017|
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