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Effects of Extensional Flow on Properties of Polyamide-66/ Poly(2,6-dimethyl-1,4-phenylene oxide) Blends: A Study of Morphology, Mechanical Properties, and Rheology.

INTRODUCTION

Poly amide (PA), as one of the most important engineering plastics, displays excellent chemical resistance and processability. However, most PAs have disadvantages such as poor dimensional stability due to high moisture absorption and low impact strength [1, 2], In contrast, poly(2,6-dimethyl-l,4-phenylene oxide) (PPO) exhibits high-dimensional stability and good thermal properties and, however, has some limitations, such as high brittleness, poor solvent resistance, and low processability [3-5], Thus, the inherent properties of PA and PPO indicate that their combination should produce materials with balanced properties, provided that the advantages from one component are able to compensate for the deficiencies of the other providing mutually complementary properties.

However, PA/PPO blends are highly immiscible because of large differences in polymer polarities and high interfacial tensions. Attributed to the viscosity difference and incompatibility of PA/PPO, simple blending of the two polymers results in the materials with poor mechanical properties owing to the ill dispersion and lack of adequate interfacial adhesion. This leads to poor control of morphology and stress transfer under loading in the solid state. Thus, compatibilization of incompatible and immiscible polymer blends has attracted significant attention in recent years. For this reason, copolymers containing maleic anhydride (MA) or glycidyl methacrylate (GMA) as compatibilizers have been added into PA/PPO blends [6-9]. The use of polystyrene grafted MA (SMA) could successfully reduce the particle size and improve the mechanical properties of PA66/ PPO blends. Functionalized PPO is another typical modifier to compatibilize PPO/PA blends. The PPO grafted with MA (PPOg-MA) is an effective compatibilizer, and specifically, the anhydride group on PPO-g-MA can react with the amine end-group of PA6 to form chemical bonds that improve the interfacial adhesion [10, 11]. The mechanical properties can be optimized when the contents of PPO-g-MA and PPO are equal [12]. However, according to the literature [13-15], the compatiblized PPO/PA6 blends still exhibited poor impact strength due to the rigidity of both the phases. Therefore, elastomers and rubbers such as styrene-butylene-styrene (SBS) block copolymer, styrene-ethylene-butylene-styrene (SEBS) block copolymer, and ethylene-propylene-diene terpolymer (EPDM) have been successfully used to toughen PPO/PA6 blends.

Furthermore, the mechanical properties of PA/PPO blends are also dominated by their morphological structures, in particular, the dispersed phase morphology, which is strongly influenced by the processing conditions [16]. In previous studies, PA/PPO blending was processed with the twin screw extruders (TSEs) or batch mixers governed by conventional shear flow. However, these PA/PPO blends, even with the addition of modifier, were still found to be at high viscosity ratio ([[eta].sub.d]/[[eta].sub.c], dispersed phase viscosity over continuous phase viscosity). As reported, melt drops of high viscosity ratio blends are more efficiently broken under an extensional flow than under a shear flow [17-21], The flow field of TSE is usually dominated by shear flow, but special screw elements or configurations could enhance the elongational effect [22, 23], In general, the generation of an extensional flow is based on converging channels; however, most of these flow fields are local or fixed [24-26]. The triangle-arrayed triple-screw extruder (TTSE) is a novel polymer processing equipment that generates a complicated flow field by three mesh zones and a convergence-divergence central zone (Fig. 1) [27]. The melts in the central zone are simulated to have large axial flow velocities, which force the fluid to flow out depending on the axial pressure gradient. Moreover, some of the melts in the central zone are dragged by screw tips into the mesh zones. The materials in TTSE would experience a shear-extensional alternating effect. Furthermore, the good melt conveying properties of TTSE could shorten the thermal processing duration and improve blending performance (28, 29], These characteristics indicate that the TTSE with an extensional effect is more efficient in blending immiscible polymers at a high viscosity ratio.

In this study, we investigated mechanical properties and phase morphology of PA66/PPO binary blends processed with TTSE and TSE to evaluate the mixing efficiency of different extruders. Moreover, PPO-g-MA and SEBS were introduced to improve the mechanical properties of PA66/PPO blends. The toughening mechanism of PA66/PPO/PPO-g-MA/SEBS blends was further explored. The main objectives of this study were to investigate the effects of extensional flow in processing with TTSE on the mechanical properties, phase morphology, and rheology of PA66/PPO blends; and provide an experimental background for simulation of flow field in TTSE.

EXPERIMENTAL

Materials

PA66 (trademark EP[R.sup.2]7), with a relative viscosity of 2.67, was supplied by Shenma Industrial Co., Ltd. PPO (trademark LXR45), made by China National Bluestar Co., Ltd., had an intrinsic viscosity 0.45 [+ or -] 0.2 dL/g measured in chloroform at 25[degrees]C. SEBS (Kraton G1651) was obtained from Shell Chemical Co. It contained 29 wt% styrene with a number average molecular weight of 29,000 in the PS blocks and 116,000 in the EB block. MA and dicumyl peroxide (DCP) (analytical grade reagents) were supplied by Beijing Chemical Industry Group Co., Ltd.

Equipment

The TTSE used in this study was self-designed with a screw diameter of 35.2 mm and a length-diameter ratio (L/D) of 28. A Coperion TSE (ZSK 26 Mc) with a screw diameter of 25 mm and a L/D of 40 was set for comparison. The ZSK 26 Mc TSE is a commercial extruder for products with a high torque requirement. The max torque of TSE is 140 Nm per shaft, and the specific torque is 15 Nm/[cm.sup.3]. The screw configurations of two extruders were designed similar for good comparison, as shown in Fig. 2.

Sample Preparation

PPO was grafted with MA via reactive melt extrusion. Briefly, powders of PPO, MA, and DCP were premixed at a ratio of 100/2/0.1 in a homogenizer at 70[degrees]C for 10 min. The mixture was extruded by a Coperion TSE at 180/260/270/290/290/290/ 290/280[degrees]C and a screw speed of 120 rpm. This grafting reaction was studied by Fourier transform infrared (FTIR) spectrometry analysis and titration analysis. The grafted MA content in PPOE-MA was about 0.5-0.6 wt%.

The weight ratios of PA66/PPO binary blends were set to be 70/30 and 50/50. The weight ratios of compatibilized PA66/ PPO/PPO-g-MA blends were set to be 90/5/5, 80/10/10, 70/15/ 15, 60/20/20, and 50/25/25, respectively, and another 5 wt% SEBS was added as toughening agent. All the mixtures were dried at 80[degrees]C for 8 h and premixed for 5 min prior to extrusion. The processing conditions of TTSE and TSE are listed in Table 1. The screw speeds were set different for same mean shear rate in flow fields, according to the following equation:

[??] = [pi] x D x n/[h.sub.a] x 60 (1)

where D is the external screw diameter (m); n is the screw speed (r/min); and [h.sub.a] is depth of flow channel (m).

The extruded blends were dried in a vacuum oven at 80[degrees]C for 8 h and then molded into standard specimens by using a HAITIAN SA900/260 injection molding machine, which operated at the barrel temperature of 270/280/285/290/280[degrees]C and injection pressure of 60 MPa.

Characterization

Mechanical Properties. The tensile (ISO-8256-2005) and flexural (ISO-178-2010) properties were measured using a universal testing instrument (XWW; Chengde Jinjian Testing Instruments Co., Ltd.) at a crosshead speed of 50 and 2 mm/min, respectively. The number of specimens was five per sample in the test. Notched impact strengths (ISO-179-2010) were measured using a pendulum impact tester (ZBC 1400-2, Shenzhen Sans Material Test Instrument Co., Ltd.) at room temperature, and the impact energy was 4 J. The number of specimens was 15 per sample in the impact strength test.

Morphology. The morphologies of the blends were examined by scanning electron microscopy (SEM) using a Hitachi-S4700 microscope at an accelerating voltage of 20 kV. All the measurements were performed on the fractured surface of impacted specimens. The surfaces were etched in chloroform for more than 8 h to selectively dissolve PPO. Moreover, some of the toughened specimens were etched with boiled n-hexane for 3 h to remove SEBS domains with a Soxhlet extractor. Subsequently, the etched surfaces were preserved overnight in vacuum at 80[degrees]C, and then coated with gold prior to SEM observations.

The volume average particle diameter [[bar.d].sub.v], number average particle diameter [[bar.d].sub.n], particle size distribution (PSD) of dispersed phase, and PSD index U were analyzed by an image analyzer (Image J 1.41) and calculated by using Eqs. The smaller the particle size of the dispersed phase, the better mixing effect of the blends; and the smaller the value of U, the more homogenous the mixing.

[[bar.d].sub.v] = [summation] [N.sub.i][d.sup.4.sub.i]/[summation] [N.sub.i][d.sup.3.sub.i] (2)

[[bar.d].sub.n] = [summation] [N.sub.i][d.sub.i]/[summation] [N.sub.i] (3)

U = [[bar.d].sub.v]/[[bar.d].sub.n] (4)

where [N.sub.i] is the number of particles with diameter [d.sub.i], and [[bar.d].sub.n] is the number average particle diameter. The number of particles was 400-500 per sample during the analysis.

Dynamic Mechanical Analysis. A dynamic mechanical analyzer (DMA7E, Perkin Elmer Inc.) was employed to study different effects of the two extruders on dynamic mechanical properties of the toughened PA66/PPO blends. The samples were molded into rectangular strips of dimensions 35 X 6 X 2 [mm.sup.3]. The experiment was performed at a frequency of 1 Hz with a stretching ratio of 0.1%. The samples were heated from room temperature to 250[degrees]C at a heating rate of 5[degrees]C/min.

Rhelogical Measurements. A HAAKE MARS-III rheometer with a parallel-plate geometry (diameter = 20 mm; gap = 1 mm) was used for dynamic rheological measurements. It collected the dynamic rheological behavior of all blends as a function of frequency declining from 100 to 0.01/s at 280[degrees]C under nitrogen.

The reason that we used parallel-plate geometry instead of capillary was that the viscosity of PPO is very high, thus the capillary rheological measurement is not suitable. The complex viscosities of PA66, PPO, and PPO/PA66 blends were obtained through dynamic rheological data. The conversion of complex viscosity [absolute value of [eta] *] to apparent viscosity [eta] was based on the CoxMerz theory [30].

RESULTS AND DISCUSSION

PA66/PPO Binary Blending

Contrasting views related to PA66/PPO blends with different PPO contents extruded by TTSE and TSE are shown in Figs. 3 and 4. PPO is in the dispersed phase of all specimens because of its high viscosity. The SEM micrographs indicate that the particle size increases with the increase in PPO content (Fig. 3). This change was attributed to the merging of small particles, caused by the increasing content of dispersed phase. The low interfacial adhesion could not maintain the small size of the PPO particles during processing. However, the PA66/PPO blends extruded by TTSE exhibit a smaller particle size and narrower particle size distribution than those of blends extruded by TSE, in particular, at higher PPO content (Fig. 4). This phenomenon indicated that the morphology of blends was significantly affected by the processing conditions, in particular, at a high content of dispersed phase and at a high viscosity ratio.

The mechanisms of polymer blending clearly indicate that dispersed drop is easier to break under an extensional flow than under a shear flow when the (dispersion/matrix) viscosity ratio is higher than 4 [17, 18]. Based on the viscosities of PA66 and PPO (Fig. 5), the viscosity ratio of PA66/PPO blends was found to be higher than 4 at the shear rates of 100/s during extrusion, indicating that the reduction in particle size in PA66/PPO blends was largely caused by the extensional effect in TTSE.

Table 2 lists the mechanical properties, volume average particle diameters, and PSD index U of PA66/PPO blends extruded by TTSE and TSE. The samples processed by TTSE exhibit smaller particle size and U than those of TSE-blended samples, fig. 7. Tensile strengths of PA66/PPO/PPO-g-MA blends extruded by TTSE and TSE. [Color figure can be viewed at wileyonlinelibrary.com] which was consistent with the result of the above mentioned morphological analysis. Furthermore, attributed to the incompatibility between PA66 and PPO, the mechanical properties of the PA66/PPO blends were weakened sharply compared to those of pure PA66 or PPO and were reduced with the increase in PPO content because of the poor dispersion. However, the TTSE-extruded blends exhibited superior mechanical properties, in particular, tensile strength, compared to the TSE-extruded blends. This superiority was attributed to the smaller particle size and narrower particle size distribution, which reduced the stress concentration in blends. Furthermore, as PA66 was easily oxidized during processing, the strong melt conveying property of TTSE could shorten the thermomechanical history of blends, which would reduce the degradation of PA66. These phenomena indicated that TTSE was more effective than the traditional TSE in PA66/PPO blending.

Toughened PA66/PPO/PPO-g-MA Blends

Mechanical Properties. The notched impact strengths of PA66/ PPO/PPO-g-MA blends extruded by TTSE and TSE are shown in Fig. 6. The notched impact strength of PA66/PPO/PPO-g-MA blends is significantly improved at high PPO/PPO-g-MA content due to the reactive compatibilization caused by PPO-g-MA. Moreover, the addition of SEBS could make the dispersed phase act as toughening particles of the blends, because of that SEBS was found to be compatible with PPO due to PS blocks. Noteworthy, the impact strengths of both specimens increased sharply at a certain content of PPO phase, which signified the occurrence of brittle-ductile transition. The impact strength of blends extruded by TSE was improved drastically from 9.2-15.2 kJ/[m.sup.2] at the PPO/PPO-g-MA content of 40 wt%. Nonetheless, the brittle-ductile transition of blends extruded by TTSE occurred at the PPO/PPO-g-MA content of 30 wt%. The impact strength increased from 10.2 to 15.6 kJ/[m.sup.2]. In other words, the extensional effect of TTSE efficiently lowered the threshold content of compatibilizer for toughening PA66/PPO blends. This improvement indicated that the interface and morphology of blends might have significantly changed by TTSE, which are discussed in the following section.

The tensile strengths and flexural strengths of PA66/PPO/ PPO-g-MA blends extruded by TTSE and TSE are shown in Figs. 7 and 8. The tensile strength and flexural strength of blends decreased with the increasing content of dispersion. These reductions were attributed to the tenacity improvement of blends. According to the mechanical data, the tensile strength and flexural strength curves were not significantly affected by the mixing equipment. Notably, the TTSE-extruded PA66/PPO blends maintained higher tensile strength and flexural strength compared to the TSE-extruded blends; however, the impact strength was still significantly improved. This phenomenon was attributed to the extensional effect and conveying property of TTSE, which reduced the particle size of dispersive phase and degradation of PA66. Moreover, the finer morphology promoted the formation of reticular structure of dispersed phase and thereby improved the tensile strength of blends.

Figure 9 demonstrates the dynamic mechanical properties of binary PA66/PPO (50/50) blends and compatibilized blends in the presence of 50 wt% PPO/PPO-g-MA. Clearly, two major glass transition temperatures ([T.sub.g]) are observed for all blends (Fig. 9a). Table 3 lists the [T.sub.g] and storage modulus (E') of different samples. The TSE-extruded blends show a [T.sub.g] at 211.1[degrees]C for PPO phase and a [T.sub.g] at 60.TC for PA66. The [T.sub.g] of PPO and PA66 in TTSE-extruded blends appear at 209.3[degrees]C and 62.4[degrees]C, respectively. The gap ([DELTA][T.sub.g]) between two glass transition temperatures decreased after processing by extensional flow, which indicated an improvement in the compatibility of PA66/PPO blends. This phenomenon was attributed to the finer morphology and stronger interfacial adhesion of blends extruded by TTSE than those of blends extruded by TSE. The shorter thermohistory achieved by TTSE maintained more copolymer characteristics of PA66/PPO-g-MA compared to TSE. Moreover, in the temperature range 20[degrees]C-120[degrees]C, the storage modulus (E') of blends extruded by TTSE was significantly higher than that of TSE-processed blends (Fig. 9b). This was attributed to the fact that the well compatibilized blends reduced the phase separation and thereby maintained the rigidity of the blend. These results were consistent with the results of the comparative analysis of mechanical properties of the blends processed by different extruders.

Morphology and Toughening Mechanism. As neither PPO nor PPO-g-MA is elastomer, it is unusual that the toughness of blends improved with the increase in PPO content. Thus, to investigate the toughening mechanism and improvement in brittle-ductile transition, the morphology of PA66/PPO/PPO-g-MA blends was observed by SEM. Figure 10 illustrates the morphology of blends at PPO/PPO-g-MA content of 30 wt%. According to the abovementioned results, the impact strength of blends extruded by TTSE was significantly improved; however, TSE-extruded blends were still brittle. The particle size decreased significantly by TTSE compared to TSE. The volume average particle sizes of dispersion in blends are listed in Table 4. The volume average particle sizes [[bar.d].sub.v] decreased dramatically at 30 and 40 wt% of dispersion for TTSE and TSE, respectively. This phenomenon was attributed to the improvements of interfacial adhesion with increasing compatibilizer content, which narrow the particle size distribution. Moreover, it indicated that the brittle-ductile transition and particle size were closely related. In general, more particles and good distribution result in the formation of more crazes around the tenacity particles, which help to transfer the impact energy and induce the plastic deformation of the matrix. Moreover, the compatibilization effect of MA group could enhance the interfacial adhesion and reduce the phase separation. Thus, the change in particle size was consistent with the previous analysis of mechanical properties.

In order to further explore the toughening mechanism of PA66/PPO/PPO-g-MA blends, we observed and analyzed the morphology of brittle fractured surface of blends etched by n-hexane. The "-hexane, which is a good solvent for SEBS; however, a poor solvent for PPO and PA6, could remove SEBS phase. Figure 11 exhibits the morphology of n-hexane-etched blends, indicating that SEBS is mainly located in the PPO phase, which is ascribed to the good compatibility between PS block and PPO. According to the literature [31], the PPO/SEBS blends showed excellent impact strength with the addition of only 10 wt% SEBS. This indicated that the dispersed phase acted as toughened particles to toughen the PA66 matrix.

According to Wu's theory, the interparticle distance ([tau]) between toughened particles is a key factor for material toughening [32]. The brittle-ductile transition occurs at a critical value ([[tau].sub.c]), which is an intrinsic property of matrix. For the PA66 matrix, the [[tau].sub.c] is about 0.3 [micro]m and [tau] could be calculated by using the following equation:

[tau] = d [[([pi]/6[phi]).sup.1/3] - 1] (5)

where d is the particle diameter of dispersed phase and [PHI] is the volume fraction of the dispersed phase. According to the SEM micrographs, the brittle-ductile transition was calculated to occur at the dispersed phase contents of 30 and 40 wt% for the TTSE-extruded and TSE-extruded samples, respectively. These results were in well agreement with the impact strength curves of blends extruded by TSE and TTSE (Fig. 12).

Rheological Properties. Figure 13 displays the viscosity curves of PA66/PPO/PPO-g-MA blends extruded by TSE. Clearly, the viscosity of blends increases with increasing content of PPO/ PPO-g-MA because of the high melt viscosity of the dispersed phase and the increased content of compatibilizer. Moreover, the viscosity of blends at low shear rates obviously increases with the addition of 40 wt% PPO/PPO-g-MA. As stated earlier, a brittle-ductile transition occurred at the dispersed phase content of 40 wt% for the TSE-extruded blends. This indicated that the toughening effects significantly increased the viscosity of blends. This phenomenon might be attributed to the following two major causes: (a) phase structural transformation and (b) molecular weight increase caused by the formation of copolymers and corresponding improvement in the interfacial adhesion. The comparison of viscosities for blends extruded by different extruders is shown in Fig. 14. Higher viscosity of the TTSE-extruded blends was observed in the presence of 30 wt% dispersed phase compared to the case of TSE, which was consistent with the previous analysis. Thus, the excellent mixing effect and conveying properties of TTSE resulted in the generation of a fine morphology structure, which efficiently improved the modification of PA66/PPO blends.

CONCLUSIONS

The mechanical properties of PA66/PPO blends extruded by TTSE were improved significantly compared to those of blends extruded by TSE due to the homogeneous morphology. The particle size of binary blends with high viscosity ratio was reduced after TTSE processing, which confirmed the effects of extensional flow in TTSE. Moreover, The TTSE-extruded samples exhibited narrower particle size distributions than those of TSE. Furthermore, in contrast to the brittle-ductile transition in impact test of TSEextruded toughened blends, the transition of TTSE-extruded samples occurred at the lower content of toughened particles, which was attributed to the finer morphology and stronger interfacial adhesion. Thus, TTSE with an extensional effect was proved to be highly efficient in blending of high viscosity ratio polymers.

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Kunxiao Yang, (1) Chunling Xin, (1) Ying Huang, (1) Lilong Jiang, (1) Yadong He (1,2)

(1) College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China

(2) The Engineering Research Center of Polymer Processing Equipment at Ministry of Education, Beijing 100029, People's Republic of China

Correspondence to: Y. He; e-mail: heyd@mail.buct.edu.cn

Contract grant sponsor: National Natural Science Foundation of China; contract grant number: 51273019.

DOI 10.1002/pen.24484

Published online in Wiley Online Library (wileyonlinelibrary.com).

Caption: FIG. 1. Structure of TTSE and its central zone. [Color figure can be viewed at wileyonlinelibrary.com]

Caption: FIG. 2. Screw configurations of TTSE and TSE.

Caption: FIG. 3. SEM micrographs of blends etched by chloroform, PA66/PPO: (a and b) 70/30 and (c and d) 50/50. (a) and (c) are blends extruded by TTSE, and (b) and (d) are blends extruded by TSE.

Caption: FIG. 4. Particle size distribution of PA66/PPO blends at weight ratio of: (a and b) 70/30 and (c and d) 50/50. [Color figure can be viewed at wileyonlinelibrary.com]

Caption: FIG. 5. Apparent viscosities of PA66 and PPO at varying shear rates. [Color figure can be viewed at wileyonlinelibrary.com]

Caption: FIG. 6. Notched impact strengths of PA66/PPO/PPO-g-MA blends extruded by TTSE and TSE. [Color figure can be viewed at wileyonlinelibrary. com]

Caption: FIG. 8. Flexural strengths of PA66/PPO/PPO-g-MA blends extruded by TTSE and TSE. [Color figure can be viewed at wileyonlinelibrary.com]

Caption: FIG. 9. (a) Loss factor and (b) storage modulus of PPO PA66/PPO/PPO-g-MA (50/25/25) blends extruded by TTSE and TSE. [Color figure can be viewed at wileyonlinelibrary.com]

Caption: FIG. 10. SEM micrographs of PA66/PPO/PPO-g-MA (70/15/15) blends extruded by (a) TTSE and (b) TSE, etched by chloroform.

Caption: FIG. 11. SEM micrographs of brittle fracture surfaces of PA66/PPO/PPO-g-MA (50/25/25) blends etched by boiled n-hexane.

Caption: FIG. 12. Interparticle distance (t) and notched impact strengths of PA66/ PPO/PPO-g-MA blends extruded by TTSE and TSE. [Color figure can be viewed at wileyonlinelibrary.com]

Caption: FIG. 13. Plots of complex viscosity versus shear rate at 280[degrees]C for PA66/ PPO/PPO-g-MA blends extruded by TSE. [Color figure can be viewed at wileyonlinelibrary.com]

Caption: FIG. 14. Comparison plots of complex viscosity for PA66/PPO/PPO-g-MA blends extruded by TTSE and TSE at 30-40 wt% content of PPO/PPO-g-MA. [Color figure can be viewed at wileyonlinelibrary.com]
TABLE 1. Processing parameters of TSE and TTSE.

Processing    Screw speed    Mean shear    Output       Barrel
equipment        (rpm)       rate (1/s)    (kg/h)    temperatures
                                                     ([degrees]C)
TSE               305            100         10         240-285
TTSE              195            100         10         240-285

TABLE 2. Mechanical properties, [[bar.d].sub.v] and U of
PA66/PPO blends extruded by TTSE and TSE.

Composition          [[sigma].sub.t]     [[epsilon].sub.b]
TTSE                       (MPa)                (%)
  PA66/PPO = 70/30   48.4 [+ or -] 3.6    2.5 [+ or -] 0.5
  PA66/PPO = 50/50   41.7 [+ or -] 2.3    2.7 [+ or -] 0.5
TSE
  PA66/PPO = 70/30   36.5 [+ or -] 4.5    1.5 [+ or -] 0.4
  PA66/PPO = 50/50   28.5 [+ or -] 1.3    1.6 [+ or -] 0.3
  PA66                     80.2                 35.2
  PPO                      72.1                 12.8

Composition          [[sigma].sub.i]     [[sigma].sub.f]
TTSE                  (kJ/[m.sup.2])          (MPa)
  PA66/PPO = 70/30   4.6 [+ or -] 0.3   72.1 [+ or -] 0.8
  PA66/PPO = 50/50   3.7 [+ or -] 0.8   68.2 [+ or -] 0.4
TSE
  PA66/PPO = 70/30   3.9 [+ or -] 0.2   73.2 [+ or -] 2.8
  PA66/PPO = 50/50   2.8 [+ or -] 0.5   65.6 [+ or -] 2.5
  PA66                     9.1                71.8
  PPO                      5.7                 83

Composition          [[bar.d].sub.v]     U
TTSE                    ([micro]m)
  PA66/PPO = 70/30         2.03         1.32
  PA66/PPO = 50/50         2.84         1.47
TSE
  PA66/PPO = 70/30         2.34         1.75
  PA66/PPO = 50/50         4.57         1.81
  PA66                      --           --
  PPO                       --           --

[[sigma].sub.t], tensile strength; [[epsilon].sub.b], elongation
at break; [[sigma].sub.i], notched Izod impact strength;
[[sigma].sub.f], flexural yield strength; [[bar.d].sub.v],
volume average particle diameter; U, particle size distribution index.
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Author:Yang, Kunxiao; Xin, Chunling; Huang, Ying; Jiang, Lilong; He, Yadong
Publication:Polymer Engineering and Science
Article Type:Report
Date:Oct 1, 2017
Words:4762
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