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Reduction of the elongation at break of thermoplastic polyolefins through melt blending with polylactide and the influence of the amount of compatibilizers and the viscosity ratios of the blend components on phase morphology and mechanics.

INTRODUCTION

Polylactide (PLA) became an important biopolymer in recent years [1] due to its properties like high strength, high modulus, high transparency, good availability, and its price being competitive to commodity polymers [2]. However, PLAs brittleness, its low deformability and low impact resistance is a limiting factor for a lot of applications. For reducing the brittleness and increasing the deformability of PLA, melt blending is the most effective method. A lot of research was and is done with the result of being able to adjust the properties to specific requirements, for example, by blending PLA with poly(ether)urethane elastomer for toughening PLA [1], Finding the right mixing conditions in melt blending is difficult, since most polymers are immiscible. The immiscibility of polymers is due to the negligibly small entropy of mixing in polymer blends [3]. The miscibility of immiscible polymer blends can be improved by adding compatibilizers. Some of them react or interact with functional groups of the blend components at the interface. That leads to a narrow size distribution of the domains, reduced coalescence, reduced polarity differences, low interfacial tension, and improved interfacial adhesion [4].

Thermoplastic polyolefins (TPO) are good materials for flexible foils with high elongations at break, have a good melt strength and can be extruded. Some applications for foils require less elongation at break and still good manufacturing conditions like a good melt strength. The present experiments investigate the possibility to reduce the elongation at break of TPO foils with PLA through melt blending. Applications for this new foil material are decorative surfaces for automotive interior. It might be used, after appropriate examination, as a decorative surface of an instrument panel. In case of an accident, a smoothly airbag deployment from the instrument panel is caused by the surface material with reduced elongations at break. Therefore, the technical advantage of that blend foil is an elongation at break of [greater than or equal to] 200% and <500% to meet the requirements of a product for decorative surfaces like an instrument panel. In other words the material is optimized for breaking at rather lower elongations compared to pure TPO foils with elongations at break of > 530%. In this case the disadvantage of PLA, its brittleness is an advantage. Since TPO is matrix polymer, TPOs high melt strength is still present and therefore good processing conditions for film extrusion are given even with TPO/PLA blends. Further the blend foil has to show rather isotropic material behavior, which means equal elongations at break in machine direction (md) and cross direction (cd).

The focus on recently studied PLA blends was mostly on reducing the brittleness and increasing the toughness of PLA with PLA being the matrix polymer. Park et al. [5] investigated among other things the effect of compatibilizers of polypropylene (PP)/ethylene-propylene-diene monomer rubber (EPDM)/PLA blends. The blend composition ranged from 0 to 1 weight fraction of PLA. The tensile strength increased and the impact strength decreased with increasing PLA amount in the blend without compatibilizer. A reinforcement of PP with PLA took place while PP was the matrix polymer. There are many reports on the modification of PLA to synthesize copolymers as compatibilizers for PLA blends [6-10]. The compatibilizers in the blends caused a more homogeneous distribution of domain size, a lowering of the fraction of large domains [6-9] and toughening of PLA [6-8, 10]. Unfortunately, no PLA copolymers are commercially available up to now. There have also been several reports of PLA blends with compatibilizers that are not PLA copolymers but rather commercially available compatibilizers. Some of those compatibilizers used in the PLA blends increased the blends toughness and reduced the size of the dispersed particles [3, 5, 7, 11, 12].

Kim et al. [3] succeeded in preparing a blend of poly(l-lactide) (PLA) and low density polyethylene (LDPE) by melt mixing that led to a reduced brittleness compared to PLA. An olefinic copolymer with glycidyl methacrylate as functional groups reduced the domain size of the dispersed phase and enhanced the tensile properties of the PLA/LDPE blends. Liu et al. [2] reported the compatibilization effects of PLA which was blended with an ethylene/n-butyl acrylate/glycidyl methacrylate (EBA-GMA) terpolymer and a zinc ionomer of ethylene/ methacrylic acid (EMAA-Zn). An optimum range of particle sizes of the dispersed phase for high impact toughness was detected for this blend system with approximately 0.7-0.9 [micro]m. Djellali et al. [13] examined blends of LDPE and PLA with and without a compatibilizer. As compatibilizer a copolymer (ethylene-co-glycidyl methacrylate) (EGMA) was used. LDPE/PLA blend compatibilized with EGMA showed reactions between glycidyl groups of EGMA and PLA endgroups (hydroxyl and carboxylic groups) through FTIR analysis. Blending 20 wt% PLA with 80 wt% LDPE the elongation at break was reduced to 48.6 [+ or -] 1.45% compared to 302.7 [+ or -] 20% of pure LDPE. As'habi et al. [14] prepared polylactide (PLA)/linear low density polyethylene (LLDPE) blends with two types of organoclays. As reactive compatibilizer a terpolymer of ethylene, butylacrylate (BA), and glycidyl methacrylate (GMA) was used. Tensile tests showed a decrease of elongation at break and tensile strength with both types of organoclays present compared to blends without. A blend of 24 wt% PLA, 71 wt% LLDPE, 5 wt% compatibilizer and no organoclay showed 207% elongation at break compared to 510% elongation at break of pure LLDPE. Djellali et al. [15] investigated rheological properties and viscoelastic behavior of polyethylene (PE)/poly (lactic acid) (PLA) blends. The melt flow index (MFI) of LDPE, PLA, and their blends showed rising values with increasing PLA amount. Zhao et al. [16] mixed ultrafine full-vulcanized powdered ethyl acrylate rubber with PLA. By mixing those materials, PLAs tensile toughness could be improved as well as PLAs strain at break. Balakrishnan et al. [17] examined PLA/LLDPE blends. 10 wt% LLDPE in PLA increased the tensile strength of the blend by 53%. Anderson et al. [10] examined PLA-PE block copolymers as compatibilizers in PE/PLA blends. PLAs toughness was increased by blending PLA, LLDPE, and PLA-PE block copolymer. Singh et al. [18] blended LLDPE and PLA with and without low density polyethylene maleic anhydride (M-g-L) as compatibilizer. The results showed that with the addition of compatibilizer the dispersion of PLA in the LLDPE matrix increased. Yoo et al. [19] examined among other things the influence of styrene-ethylene-butylene-g-maleic anhydride (SEBS-g-MAH) in polypropylene (PP)/polylactide (PLA) blends (80/20) regarding tensile strength and impact strength before and after hydrolysis. The results showed a reduced tensile strength of the PP/PLA blend (80/20) with 3 phr SEBS-g-MAH before hydrolysis and increased impact strength after hydrolysis. Based on the results, SEBS-g-MAH served as impact modifier in the PP/PLA blend. Lee et al. [20] blended PP with PLA and investigated the influence on morphology and mechanical properties of various compatibilizers. The blend with 3 wt% glycidyl methacrylate-g-polyethylene (GMA-g-PE) showed higher elongations at break compared to the blend compatibilized with maleic anhydride-g-polyethylene (MAH-g-PE). Ebadi-Dehaghani et al. [21] worked out that by adding 5 wt% of a terpolymer (ethylene butylacrylate and glycidyl methacrylate) the sizes of the dispersed PLA phases in a blend with 75 wt% PP and 25 wt% PLA was reduced by 100%, compared to the sizes of the dispersed PLA phases in the uncompatibilized blend.

Everaert et al. [22] investigated the influence of the meltviscosity ratio on the phase morphology development in immiscible polymer blends. The experiments showed, that the finest dispersion in the matrix was observed at p = 1 where p = [[eta].sub.d]/[[eta].sub.m] is the viscosity ratio of the viscosity of the dispersed polymer ([[eta].sub.d]) and the viscosity of the matrix polymer ([[eta].sub.m]). Favis and Chalifoux [23] studied polypropylene/polycarbonate blends with the focus on viscosity ratios below 1 and PP as matrix polymer. The minimum particle size was achieved with p = 0.15. Gonzales-Nunez et al. [24] reported the influence of the morphology of the dispersed phase in immiscible polymer blends with respect to the final physical properties. They came to the conclusion that the combination of lower viscosity ratio and increased shear stress results in a significant deformation of the dispersed phase for the compatibilized polymer blend. The influence of viscosity ratio in relation to phase inversion and cocontinuity in immiscible polymer blends was investigated by Miles and Zurek [25] and Furgiuele [26]. Miles and Zurek [27] calculated the point of phase inversion with respect of the blend components viscosities. It was possible to calculate the cocontinuity due to the results of the verifications that Miles and Zurek made.

Here the influence of different TPO matrix viscosities was studied regarding the blend morphologies, dispersed phase size, and mechanical properties with respect to elongations at break. Further the influence of the amount of ethylene/n-butyl acrylate/glycidyl methacrylate terpolymer (PVM) as compatibilizer, which was used since TPO and PLA are very incompatible based on a big difference in polarity, was studied. The objective is the reduction of TPOs elongation at break by blending TPO with PLA and developing a blend foil with elongation at break-[greater than or equal to] 200% and <500% and with isotropic material behavior regarding the elongation at break. Ethylene/n-butyl acrylate/glycidyl methacrylate terpolymer was chosen due to its reactive glycidyl groups and its polar n-butyl acrylate groups. The reactions between glycidyl groups of PVM and PLA endgroups (hydroxyl and carboxylic groups) has been reported by Djellali et al. [13], The morphologies and the mechanical properties of the TPO/PLA blends in the presence and absence of the compatibilizer were investigated. Compatibilizer is used for narrowing the size distribution of the dispersed phase, reduced coalescence, reduced polarity differences and reduced interfacial tension. Morphology and the dispersed phase size were characterized by environmental scanning electron microscopy (ESEM). The shapes and sizes of the dispersed PLA phases visible through ESEM images were analyzed with a program for image evaluation (Image J). To detect and locate the compatibilizer in the blend AFM images of the TPO/PLA blends in the presence and absence of the compatibilizer were recorded and analyzed.

EXPERIMENTAL

Materials and Sample Preparations

Three TPO types were used for melt blending with PLA. The main difference in those TPO types is the viscosity or the melt flow index (MFI). Relevant information and abbreviations about the used blend components are listed in Table 1 and the chemical structures of the polymers are presented in Fig. 1. Melt blending was performed using a corotating twin-screw extruder (KraussMaffei Berstorff ZE34x46D, L/D ratio 46:1, screw diameter 34 mm) at a screw speed of 200 RPM. The temperature profile of the extruders heating elements was 20/220/220/220/200/200/ 200/200[degrees]C from the feeding zone to the die. The sample preparation was performed in two steps. At first the blend components were extruded and granulated and in a second step the polymer blends present in the form of granules were extruded into a film in a corotationg twin-screw extruder (Brabender DSE25x28D, L/ D ratio 28:1, screw diameter 25 mm) and a screw speed of 200 RPM. The temperature profile of the second extruders heating elements was 200/200/220/200/200[degrees]C from the first element after the feeding zone to the sheet die. The width of the sheet die was 350 mm and the extruded film had a thickness of about 0,6 mm. The fraction of PLA was fixed for all blends at 30 wt % of the total blend weight. The fraction of TPO was varied from 60, 65, and 70 wt %, while PVM was added in 10, 5, or 0 wt%, respectively. All blends with different combinations of components were processed under the same conditions, first extrusion of granules and in the second step film extrusion. All blend components and their specifications are listed in Table 1.

Mechanical Tests

Tensile tests were performed on a testing machine (Zwick Z2,5/TN) according to DIN EN ISO 527-3. The length of the dumbbell specimen was 100 mm, the web width of 4 mm and a gauge length of 25 mm. The specimen were punched out of the extruded foils, stored for 24 h under norm conditions and were tested with 0,1 N pre load and crosshead speed of 500 mm/min under norm conditions. Every blend was measured eight times in machine direction (md) and cross direction (cd).

Morphological Characterization

Environmental Scanning Electron Microscopy. The morphologies of the dispersed phases in the blends were obtained by environmental scanning electron microscopy (ESEM) (Quanta 250FE from FEI with an Oxfort EDX system). The films were prepared in cross section in machine direction (md). For imaging the morphology, the samples were cut in md at -120[degrees]C with a diamond knife to get an even sectioned surface for ESEM measurements. With a vCD detector for backscattered electrons under 100 Pa [H.sub.2]O atmosphere and 5kV accelerating voltage the images were taken. The morphological blend structure could be detected due to material contrasts. A computer program for image analysis (ImageJ) was used for analyzing the pictures regarding the quantification of sizes and shapes of the dispersed PLA phases.

Atomic Force Microscopy. The morphologies of the dispersed phases in the blends were obtained by atomic force microscopy (AFM). The films were prepared in cross section in machine direction (md). For imaging of bulk morphology, the samples were cut in md at--120[degrees]C and a diamond knife to get an even sectioned surface for AFM measurements. All images were acquired with MultiMode AFM and a Nanoscope Ilia controller (Veeco DI Instruments) under ambient conditions in tapping mode. Si-Cantilevers of super sharp type, with about 2-10 nm radius of curvature and 160 kHz resonance frequency, were used. Standard parameters were applied and varied to get optimized image quality. According to the used parameter and cantilevers, the darker color in the phase images is related to the softer component in the polymer blends.

RESULTS AND DISCUSSION

Different Viscosity Ratios

The influence of different viscosity ratios in polymer blends was tested. Therefore, three blend films were extruded from formulations that varied in the type of TPO but all had 60 wt% TPO, 30 wt% PLA, and 10 wt% PVM. The different viscosities (r/) of the components are listed in Table 1. For characterizing the blend films prepared from formulations with different viscosity ratios of the blend components, tensile tests in machine direction (md) and cross direction (cd) were carried out. The data of the tensile strength for three formulations (A), (B), and (C) in md and cd, Fig. 2, indicate that this property is not very much affected by the viscosity ratio. Thus, the tensile strength is not sensible to mixing under different conditions and the different phase morphology. Tensile modules of the three formulations (A), (B), and (C) are shown in Fig. 3. With decreasing viscosity ratios of the blend components, from sample (A) to (C), the tensile modulus increases slightly. The elongation at break is a good indicator for the blend regarding the phase morphology and interfacial adhesion. Figure 4 shows the nominal elongation at break for three samples (A), (B), and (C) in md and cd. The nominal elongations at break of the blend components are shown in Fig. 5 for comparison to the results of the blends. Sample (A) in Fig. 4 has the lowest elongation at break with 34% in cd and 109% in md. The elongation at break in cd and md of that sample are < 200%. Those results of sample (A) can be explained by the viscosity ratio of p= 0.13, the furthest from 1 of the tested blends (1 means that the viscosities of matrix and dispersed phase are equal). The morphology of this blend is shown in Fig. 6A). Here the dispersed phase is PLA (white) and the matrix is TPOl (black). The ESEM image shows elongated PLA phases stretching through the blend foil in md. While stretching the sample, the PLA phases break and therefore form predetermined breaking points in the sample. With further elongation, the sample breaks. Stretching the film in cd, the PLA phases break forming predetermined breaking points. With further elongation of the sample, the rupture takes place along the brittle and elongated PLA phase inducing the low nominal elongations at break in cd. The elongations at break for sample (B) and (C), Fig. 4, are higher than for sample (A). The viscosity ratios of (B) with p = 0.48 and (C) with p = 0.78 are closer to 1 than the one with p = 0.13 of sample (A). Again the morphologies of the blends as shown in Fig. 6 can explain the behavior: The PLA phases of (B) and (C) are much smaller and more spherical as for (A). A difference in phase morphology of (B) and (C) is also visible in the ESEM images. The PLA phases in (C) are more spherical than in (A) and (B), which explains the highest elongation at break for (C), since the applied stress can be transferred around the spherical dispersed PLA phases across the matrix. That behavior results in increased nominal elongation at break since the applied stress can be optimally transferred through the matrix. Han et al. [27] explained different morphologies in PS/PE blends by the viscosity ratios. They found elongated droplets when the PS as dispersed phase had a lower viscosity than the PE matrix. However, the droplets are less elongated having low viscous PS as matrix polymer and high viscous PE as dispersed phase. This behavior was ascribed to the flow field in the melt processing [27]. The investigations of Han et al. [27] can be transferred to the present observations of droplet formation as consequence of the different viscosity ratios and the process of film extrusion. The distribution curves of the form factors F = 4[pi]A/[P.sup.2] [26], with A being the area and P the perimeter of the dispersed phase for the samples shown in Fig. 7. A form factor of 1 is a perfectly round sphere. Figure 7 shows that with equalizing viscosities of matrix and dispersed phase, the maximum of the form factors is getting closer to 1 thus the PLA phases become more spherical. The effect can also be visualized by investigating the perimeter of the droplets. The data for the average perimeter and the form factor are compiled in Table 2. Looking at picture (A) in Fig. 6 and comparing the results of the perimeter measurement is stunning at the first point since it is 10.75 [+ or -] 45.18 [micro]m but (A) shows phases reaching over the whole image. The mean perimeter of (A) with 10.75 [+ or -] 45.18 [micro]m is caused by the many small dispersed PLA phases in the sample and the large standard deviation is caused by a few dispersed particles in the samples with big perimeters. The mean perimeter was calculated based on number and since the majority of the dispersed phases have small perimeters, the few large values cause the large standard deviation. Quantifications of sizes and shapes of the dispersed PLA phases in Fig. 7 show right-skewed distributions, caused by a few large dispersed PLA phases besides mostly small phases in every sample. Djellali et al. [13] investigated particle size distributions of LDPE/PLA blends (80/20 and 20/80). Both of them are right-skewed distributions [13]. Investigations of the influence of different viscosity ratios of blend components made clear that small and spherical droplets of dispersed PLA phase in TPO matrix are achieved if the viscosities of the matrix and dispersed phase polymers adjust. Those rather spherical droplets cause a high nominal elongation at break. In spite of the works objective, reducing TPOs elongation at break by blending it with PLA, the blend sample with TPO3 shows the best results regarding its morphology and elongation at break. The elongations at break in md and cd have high values and are roughly isotropic. High nominal elongations at break as a good result seem contradicting at first with respect of the objective but the morphology of that sample shows the finest dispersion of PLA regarding the form factor and perimeter. Therefore, the blend with TPO3 and PLA shows the best mixing results. The nominal elongation at break of TPO3 has been reduced by approximately 150-200% compared to pure TPO3 and its nominal elongation at break is within [greater than or equal to] 200% and < 500%.

Different Amount of Compatibilizer

TPO3 which has the lowest viscosity ([[eta].sub.TPO3] = 630 Pa*s) has given the best results in the experiments before, regarding the form factor of the dispersed PLA phase and its roughly isotropic nominal elongations at break (md and cd) between [greater than or equal to] 200% and < 500%. Therefore, TPO3 was used for further tests to examine the influence of the amount of compatibilizer in TPO/PLA blends. Here three amounts of compatibilizer (PVM) 0 wt%, 5 wt% and 10 wt% were tested with a constant amount of 30 wt% PLA and the rest was TPO3. The use of compatibilizer in the blend seems contradicting at first with respect to the objective. Compatibilizer increases mechanical properties of a blend by reducing interfacial tension and improving interfacial adhesion. Both are needed in a blend with good interaction between the interfaces for transferring the applied stress across the interface of the blend components. PVM was chosen for determining its effect on the morphology and the elongation at break of the blends with TPO3 and PLA. The elongations at break have to be between < 500% and [greater than or equal to] 200%. Thus three formulations were used: 70TPO3/30PLA/0PVM (D), 65TPO3/30PLA/5PVM (E), and 60TPO3/30PLA/10PVM (F). In Fig. 8, the nominal elongations at break of the samples are shown. Sample (D) with no PVM has the lowest nominal elongation at break. Again there is a difference in the test results in md and cd caused by the phase morphology of the sample as shown in the ESEM images (Fig. 9D). The dispersed PLA phase (white) in the TPO3 matrix (black) forms rather big droplets and some of them are elongated in md. This might be caused by poor interfacial adhesion, high interfacial tension and also by the film extrusion process. In comparison to sample (D) the nominal elongations at break are high for (E) and (F) which both have PVM in the formulation. The difference between (E) and (F) is not big, an increase from 5 wt% to 10 wt% PVM does not bring a big increase in nominal elongation at break. It should be pointed out, that F and C have the same formulation. Comparing the nominal elongations at break of C (358% in cd and 426% in md, Fig. 4) and F (327% in cd and 417% in md. Fig. 8) thus, the formulations are reproducible and give constant values. Figure 10 shows the right-skewed distribution curves of the form factors and the perimeters of sample (D), (E), and (F). Increasing the PVM amount from 0 to 5 wt% the form factor increases which means that with increasing amount of PVM (from 0 wt% to 5 wt%) the PLA droplets become more spherical. Increasing the amount of PVM further from 5 to 10 wt% the form factor decreases slightly, Table 3. The illustration of the perimeter shows that the droplets do not change in perimeter with an increasing amount of PVM from 5 to 10 wt%. As expected from the similarity in the morphology the increase from 5 wt% to 10 wt% PVM in the formulation does not result in a significant increase in the nominal elongation at break. Figure 11 shows the tensile strengths and Fig. 12 the tensile modules of the samples (D), (E), and (F). Tensile strengths do not vary significantly with increasing amount of PVM. Tensile modules show fairly high scattering about the mean values. With increasing amount of PVM (0 to 10 wt%), no significant change in tensile modulus can be reported.

AFM. On the basis of AFM images it is attempted to locate the PVM in the TPO3/PLA blend. Formulations (G) to (I) differ in the amount of PVM from 0, 5, and 10 wt% (Fig. 13). Since the imaging of the samples was done in tapping mode, the different rigidities of the blend samples show different colors. The darker color in the phase images should be the softer component in the polymer blends, see the colored bar in Fig. 13. Image (G), Fig. 13, shows the blend without any compatibilizer. At the top of the image a curved hard phase is partially visible and in the lower left corner is another piece of a dispersed hard phase in the matrix. Those phases are the harder PLA phases dispersed in the softer TPO3 matrix. The rest around the PLA phases is the TPO3 matrix. Since TPO3 is a polypropylene/ethylene-propylene-rubber (PP/EPR) the structures in the matrix are ethylene and propylene domains, whereat the lighter domains are the harder crystalline propylene and the darker domains are the softer EPR. Figure 14(J) shows an AFM image of TPO3. Comparing that image with the matrix in image (G) it becomes clear, that the matrix is the TPO3 consisting of EPR (dark) and propylene (light) domains. Comparing the three images of Fig. 13 the roundish dispersed PLA phases are visible in the TPO3 matrix in all three images. A difference in the blend structure can be found at the interface of PLA phase and TPO3 matrix, marked with an arrow in Fig. 13. Picture (G) shows that there is no layer between PLA phase and TPO3 matrix. However in the images for (H) and (I) a darker ring around the PLA phase is observed. The width of the ring increases with increasing amount of PVM. A TPO3/PVM blend is shown in Fig. 14K). The image shows, that the PVM2 is mixed with the rubbery EPM domains of TPO3, which means, that the PVM mixes with the TPO3 quite well. The samples were analyzed with differential scanning analysis (DSC) to compare the glass transition temperatures ([T.sub.g]) of the TPO3 in the blends with the [T.sub.g] of pure TPO3 and pure PVM. The data is not shown here since no displacements of the values were detected and therefore the DSC measurements gave no indication of PVM mixing with the rubbery EPM domains of TPO3.

With the AFM images it was not possible to detect and identify the compatibilizer but the AFM images clearly show changes in the morphology of the blend and a change of the interface. Having formulations with PVM, soft rubbery layers around the dispersed PLA phases are observed. Increasing the PVM amount, a soft shell around the PLA phase develops and its thickness increases with increasing PVM amount. The AFM images could not clarify if that soft shell is PVM, a mixture of the ethylene domain of TPO3 and PVM or if it is the soft EPR domain of TPO3.

CONCLUSIONS

TPO/PLA blend foils have been obtained by film extrusion with TPO as matrix material and PLA as dispersed phase to decrease the elongation at break of the foil. The influence on one hand of different viscosity ratios of the blend components and on the other hand of different amounts of compatibilizer on mechanical properties and the morphology of the blend foils were tested. The results showed the big influence of the viscosity ratio of the blend components on the morphology and on the elongation at break of a blend foil. By blending TPO3 with PLA and PVM the elongation at break (md and cd) of a blend foil was reduced by 100-150%. The morphology revealed a good dispersion of the dispersed PLA phase in the TPO3 matrix. With viscosity ratios of TPO3 and PLA close to 1, the dispersed PLA phases became more spherical and smaller. An increasing amount of compatibilizer increased the surfaces of the dispersed PLA phases by reducing the size of the dispersed PLA phases and increased a spherical geometry. AFM images of the TPO/ PLA blend films with different amounts of compatibilizer showed a change in the morphology around the PLA phases. A rubbery softer layer is found around the PLA phases. On the basis of the AFM images it cannot be verified that the rubbery ring is the compatibilizer around the PLA phases or if it is a mixture of PVM and the rubbery part of the TPO.

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Carolin Vogt, (1) Hans-Josef Endres, (2) Jurgen Buhring, (1) Henning Menzel (3)

(1) Research and Development, Benecke-Kaliko AG, Beneckeallee 40, Hannover, D-30419

(2) Institute for Bioplastics and Biocomposites, Hochschule Hannover, Heisterbergallee 12, Hannover, D-30453

(3) Institut Fur Technische Chemie, Abt. TC Makromolekularer Stoffe, Technische Universitat Braunschweig, Hans-Sommer-Strasse 10, Braunschweig, D-38106

Correspondence to: C. Vogt; e-mail: caro.vogt@gmx.net

DOI 10.1002/pen.24319

TABLE 1. Characteristics of materials.

Polymer                  Abbreviation            Specifications

Polylactide              PLA            MFI (230[degrees]C, 2.16 kg)
                                          = 19 g/10 min
                                        Viscosity (shear rate 10 1/s)
                                          = 490 Pa s specific
                                          gravity = 1.2 g/[cm.sup.3]
                                        [M.sub.w/LS] = 162 [+ or -]
                                          3 Kg/mol
                                        [T.sub.g] (DSC) =
                                          60[degrees]C, [T.sub.m]
                                          (DSC) = 153[degrees]C

Polypropylene/           TPO1           MFI (230[degrees]C, 2.16 kg)
  ethylene-propylene-                     = 0.6 g/10 min
  rubber (PP/EPR)                       Viscosity (shear rate 10 1/s)
                                          = 3830 Pa s specific
                                          gravity = 0.9 g/[cm.sup.3]
                                        [M.sub.w/LS] = 423 [+ or -]
                                          12 Kg/mol
                                        [T.sub.g] (DSC) = -
                                          33[degrees]C, [T.sub.m]
                                          (DSC) = 143[degrees]C

Polypropylene/           TP02           MFI (230[degrees]C, 2.16 kg)
  ethylene-propylene-                     = 8 g/10 min
  rubber (PP/EPR)                       Viscosity (shear rate 10 1/s)
                                          = 1015 Pa s specific
                                          gravity = 0.9 g/[cm.sup.3]
                                        [M.sub.w/LS] = 216 [+ or -]
                                          15 Kg/mol
                                        [T.sub.g] (DSC) = -
                                          32[degrees]C, [T.sub.m]
                                          (DSC) = 144[degrees]C

Polypropylene/           TPO3           MFI (230[degrees]C, 2.16 kg)
  ethylene-propylene-                     = 14 g/10 min
  rubber (PP/EPR)                       Viscosity (shear rate 10 1/s)
                                          = 630 Pa s specific
                                          gravity = 0.9 g/[cm.sup.3]
                                        [M.sub.w/LS] = 192 [+ or -]
                                          12 Kg/mol
                                        [T.sub.g] (DSC) = -
                                          34[degrees]C, [T.sub.m]
                                          (DSC) = 142[degrees]C

Ethylene/n-butyl         PVM            MFI (230[degrees]C, 2.16 kg)
  acrylate/glycidyl                       = 20 g/10 min specific
  methacrylate                            gravity = 0.9 g/[cm.sup.3]
  terpolymer                            [T.sub.g] (DSC) =
                                          -49[degrees]C, [T.sub.m]
                                          (DSC) = 70[degrees]C
                                        Glycidyl methacrylate = 1.6
                                          mol%
                                        Butylacrylate = 5.3 mol %

TABLE 2. Morphological parameters of the dispersed PLA phase
based on the ESEM images of blend films in md with
60TPOX/30PLA/10PVM with X being: (A) TPO1 ([[eta].sub.TPO1] =
3830 Pa s), (B) [[eta].sub.TPO2] (t/TPO2 = 1015 Pa s), (C)
TPO3 ([[eta].sub.TOP3] = 630 Pa s), [[eta].sub.PLA] = 490 Pa s.

                                A                     B

Form factor             0.67 [+ or -] 0.27    0.76 [+ or -] 0.21
Perimeter [[micro]m]   10.75 [+ or -] 45.18   6.54 [+ or -] 5.64

                                C

Form factor             0.81 [+ or -] 0.17
Perimeter [[micro]m]    6.52 [+ or -] 4.76

TABLE 3. Morphological parameters of the dispersed PLA phase
based on the ESEM images of blend films in md with 30 wt%
PLA, the rest TPO3 + PVM with (D) 0 wt% PVM, (E) 5 wt% PVM,
(F) 10 wt% PVM.

                                 D                     E

Form factor             0.66 [+ or -] 0.29    0.84 [+ or -] 0.15
Perimeter [[micro]m]   29.06 [+ or -] 32.69   8.23 [+ or -] 5.79

                                 F

Form factor             0.75 [+ or -] 0.21
Perimeter [[micro]m]    8.20 [+ or -] 7.66


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Please note: Some tables or figures were omitted from this article.
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Author:Vogt, Carolin; Endres, Hans-Josef; Buhring, Jurgen; Menzel, Henning
Publication:Polymer Engineering and Science
Article Type:Report
Date:Aug 1, 2016
Words:5755
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