Morphology and Properties of Polyolefin Elastomer/Polyamide 6/Poly(lactic Acid) In Situ Special-Shaped Microfibrillar Composites: Influence of Viscosity Ratio

In Situ microfibrillation is an easy and economical processing method, which has drawn wide concern in recent years. In Situ special-shaped microfibrillar composites, which with poly(lactic acid)/polyamide 6 (PA6/PLA) together formed special-shaped microfibrils in polyolefin elastomer (POE) matrix, were successfully prepared by using multistage stretching extrusion technology. Four types of PA6 with different viscosity were utilized to investigate the effect of viscosity ratio of PA6 to PLA on the structure evolution of special-shaped microfibrils and the mechanical properties of POE/(PA6/PLA) composites. The morphological observation showed that the viscosity ratio was closely associated to the size and shape of PA6 and greatly affected the microfibrillar morphology of PLA/PA6. When the viscosity ratio of PA6 to PLA was less than 2.2, the “gourd-skewers-like” structure microfibrils were obtained. When the viscosity ratio of PA6/PLA to 14.2 was further increased, the “trepang” structure microfibrils were dominant. The “gourd skewers” structure microfibrils were favorable to improvement the tensile strength, Young’s modulus, and viscoelastic properties of POE/(PA6/PLA) blends compared to the “trepang” structure microfibrils. In addition, the morphology of microfibrils exhibited a negligible effect on the melting and crystallization temperature and crystallization degree of PLA and POE matrix. This work provides a new strategy for designing the in situ special-shaped microfibrillar composites with improved mechanical properties.


Introduction
The conventional composite reinforced by the adding of a reinforcing filler (e.g., glass fiber or carbon filler) is typically an organic-inorganic system [1,2]. The adding of filler can effectively improve the mechanical properties of matrix material, which are increasingly attracting the interest of researchers [3][4][5]. In Situ microfibrillar composites (MFCs) are a type of polymer-polymer composites, in which the dispersed component develop microfibrils in situ and distribute uniformly in the matrix during the blending process [6][7][8][9]. MFCs, providing a potential, economical way of tailoring the properties of the polymer blend's product according to the desired application, which has been widely concerned in recent years [10][11][12]. Xie et al. [13] prepared the Poly(lactic acid) (PLA)/Poly (butylene succinate) (PBS) MFCs and found that the dispersed phase PBS developed in situ nanofibrillar PBS and dramatically improved the strength, modulus, and ductility of composites compared with pure PLA. This phenomenon was found in many composites systems, such as PLA/polyamide 6 (PA6) composites [14], Polyolefin elastomer (POE)/poly(trimethylene terphthalate) (PTT) composites [15,16], and poly(ethylene terephthalate) (PET)/isotatic polypropylene(iPP) composites [17]. Sun et al. [18] prepared POE/PLA MFCs and found of POE and PLA were given in Table 1 and the physical parameters of PA6 was given in Table 2.

Specimen Preparation
First, PLA and PA6 were dried in a vacuum oven at 80 • C and 100 • C, respectively, for 12 h. Then, the PA6/PLA master batches with weight ratios of 1/1 were extruded by the twin-screw extruder (CTE-20, Nanjing Jieya Extruded Equipment Co., China). The screw speed was 200 rpm and the temperatures from the hopper to the exit of the extruder were 225-230 • C. Finally, the POE/(PLA/PA6) composites with the weight ratio of 75/25 were extruded by the multistage stretching extrusion assembly, which contained a twinscrew extruder (SHJ-30, Nanjing Jieya Extruded Equipment Co., China), an extrusion die with an assembly of laminating-multiplying elements (LMEs). The screw speed was 250 rpm and the temperature from the hopper to the exit of the extruder was 50-230 • C. The temperature of LMEs was 230 • C. After the POE/(PLA/PA6) melt flowed from the extruder die, the extrudate was further stretched at rate of 80 rpm to obtain MFCs. The in situ POE/(PA6/PLA) MFCs with different viscosity ratio (the ratio of PA6 viscosity to the PLA viscosity at the same temperature) were coded as MFCs-xx, where xx represented the viscosity ratio of PA6 to PLA.

Characterization
A field emission scanning electron microscope (SEM, QUANTA FEG 250, FEI Company, USA) was employed to observe the microstructure of the composites. The composite sheets were placed in liquid nitrogen for 2 h, finally the samples were cryogenically fractured along to extrusion direction or perpendicular to extrusion direction. The smooth fractured surfaces can then be taken for SEM observation or the further etching process. For the etching, the fractured surfaces were immersed in hot xylene at 80 • C for 12 h to dissolute POE, after which it was cleaned by ethyl alcohol, and then immersed in dichloromethane (CH 2 Cl 2 ) at 20 • C for 1 h to dissolute PLA. Note that all etched surfaces were cleaned by using distilled water prior to SEM observation.
Thermal analysis of the samples were studied by DSC (Q10, TA Company, New Castle, DE, USA) under N 2 atmosphere. The dynamic scanning was applied at a heating rate of 10 • C/min from 5 • C to 240 • C for MFCs. After holding the sample at a high temperature for 5 min, it was then cooled down to 5 • C at a heating rate of 10 • C/min to analyze the crystallinity behavior.
The crystallinity of PA6 and POE were calculated using the following equation: The crystallinity of PLA was calculated using the following equation: In Equations (1) and (2), ∆H m and ∆H c were the enthalpies of melt crystallization and cold crystallization, respectively. The ∆H 0 m was the melting enthalpy for 100% crystallinity. The ∆H 0 m values of PA6, PLA, and POE were 230 J/g [51], 93.7 J/g [52], and 205 J/g [53], respectively. The symbol ϕ represented the mass percentage of the PA6, PLA, or POE in the MFCs.
The dynamic rheological experiments of PLA, PA6, and POE/(PLA/PA6) MFCs were studied by Rotational rheometer (MARS60, USA), using parallel-plate geometry with a diameter of 25 mm. The dynamic viscoelastic properties were determined with frequencies from 0.05 to 100 rad/s at 1% strain amplitude. The measured temperature of PLA and PA6 were fixed at 230 • C, which was the processing temperature. The measured temperature of POE/(PLA/PA6) MFCs was fixed at 130 • C, which was lower than the melting temperature of PLA/PA6. According to ASTM standard D638, tensile tests were made by a universal testing machine (CMT6104, China) with a crosshead speed of 500 mm/min and a gauge length of 25 mm. Specimens for tensile test were cut from the extrusion sheet along or perpendicular to the extrusion direction. The width and the thickness of specimens were measured before tensile test. All measurements were repeated at least five times and the average values were reported. Figure 1 shows the storage modulus(G ), loss modulus(G ), and complex viscosity(η*) of PA6 and PLA and the viscosity ratio of PA6/PLA as a function of frequency. It can be seen that the G of PA6 increased with the increasing of viscosity of PA6 at identical frequencies. These results can be attributed to the restriction of the PA6 chain's mobility, which can improve the capability of storing the deformation energy over extended periods of time (increasing the relaxation time) [14]. The G of PA6 increased with the increasing of PA6 viscosity (Figure 1b). This can be attributed to the increasing of energy consumption of PA6 chain's slippage in unit time [40]. In addition, with the increasing of frequencies, the η* of PA6 and PLA decreased continuously (Figure 1c), implying that the PA6 and PLA were non-Newtonian fluids and all followed the shear thinning behavior [34]. When the frequency was 1, the viscosity ratio of PA6 to PLA was 0.5, 2.2, 5.3, and 14.2. The G , G , and η* of PLA was only greater than the PA6-2.0 at identical frequencies and the viscosity ratio of PA6-2.0/PLA was lower than 1.  Figure 2a-d, it can be seen that, after hot stretching, the dispersed phase (PA6 and PLA) was fully extended into special-shaped structure microfibrils in the POE matrix. As compared with the regular cylinder-shaped microfibrils in the POE/PLA composites [18], the special-shaped microfibrils had an uneven diameter. When the viscosity ratio of PA6/PLA was 0.5, the gourd-skewers-like structure microfibrils were dominance. The gourd-skewers-like microfibrils had many knots with a larger diameter connected by the skewer with smaller diameter. With the viscosity ratio of PA6 to PLA increased, the diameters of knots and the distance between knots all tended to decrease. When the viscosity ratio of PA6 to PLA increased to 5.3, the microfibrillar morphology appeared in "trepang" structure (red dotted circle). Further increasing the viscosity ratio of PA6/PLA to 14.2, the "trepang" structure microfibrils were dominant. The trepang-like microfibrils had a large diameter with many small knots on their surfaces. From Figure 2e-h, it can be seen that when the viscosity ratio of PA6 to PLA was 0.5, the PA6 phase presented short rod-like microfibrils, ellipsoid particle, and spherical particle after etching PLA. With the increasing of PA6 viscosity, spherical particles were dominant and the diameter of ellipsoid particle and spherical particles decreased gradually (red dotted circle). The average diameter of PA6 decreased from 3.47 µm to 1.77 µm and the diameter distribution of PA6 became narrow with the increasing of viscosity of PA6 (Figure 2i-l), revealing that the deformation degree of PA6 phase became lower with the increasing of viscosity of PA6 during the hot stretching.   Figure 2a-d, it can be seen that, after hot stretching, the dispersed phase (PA6 and PLA) was fully extended into special-shaped structure microfibrils in the POE matrix. As compared with the regular cylinder-shaped microfibrils in the POE/PLA composites [18], the special-shaped microfibrils had an uneven diameter. When the viscosity ratio of PA6/PLA was 0.5, the gourd-skewers-like structure microfibrils were dominance. The gourd-skewers-like microfibrils had many knots with a larger diameter connected by the skewer with smaller diameter. With the viscosity ratio of PA6 to PLA increased, the diameters of knots and the distance between knots all tended to decrease. When the viscosity ratio of PA6 to PLA increased to 5.3, the microfibrillar morphology appeared in "trepang" structure (red dotted circle). Further increasing the viscosity ratio of PA6/PLA to 14.2, the "trepang" structure microfibrils were dominant. The trepang-like microfibrils had a large diameter with many small knots on their surfaces. From Figure 2e-h, it can be seen that when the viscosity ratio of PA6 to PLA was 0.5, the PA6 phase presented short rod-like microfibrils, ellipsoid particle, and spherical particle after etching PLA. With the increasing of PA6 viscosity, spherical particles were dominant and the diameter of ellipsoid particle and spherical particles decreased gradually (red dotted circle). The average diameter of PA6 decreased from 3.47 μm to 1.77 μm and the diameter distribution of PA6 became narrow with the increasing of viscosity of PA6 ( Figure  2i-l), revealing that the deformation degree of PA6 phase became lower with the increas- The evolution mechanism of special-shaped microfibrils was shown in Figure 3. when the PA6/PLA master batches were feed into the twin screw extruder, the particles of PA6/PLA master batches broke up to form droplets under the action of shear stress. Under the action of the shear and stretch stress, the dispersed droplets occurred deformed, making the dispersed transformed from droplets to the final fibril [19,27]. When the viscosity ratio of PA6 to PLA was 0.5, due to the PA6 generated short rod-like microfibrils and ellipsoid particle with a larger diameter during the hot stretching, the gourd-skewers-like microfibrils had knots with larger diameter and length. With the viscosity ratio of PA6 to PLA increasing to 2.2, the diameter and length of knots of the gourd-skewers-like microfibrils decreased due to diameter of the PA6 particles decreased. Further increasing the viscosity ratio of PA6/PLA to 14.2. the microfibrils morphology turned into the "trepang" structure. Figure 4 shows the dependence of storage modulus(G ), loss modulus(G ), and complex viscosity (η*) on angular frequency(ω) for in situ POE/(PA6/PLA) MFCs at 130 • C. It was evident that the G and G of all the specimens increased with increasing angular frequency (Figure 4a,b). At low frequencies, the G , G of POE/(PA6/PLA) blends increased linearly. At high frequencies, the frequency-dependence of G , G was substantially weakened and a small platform appeared due to the frequency's response difference of PA6/PLA microfibrils physically entangled network. The information of situ microfibrils made effective contributions for not only the elastic behavior, but also the viscous behavior. Sun et al. [18] had the similar conclusion about the research of POE/PLA microfibrillar composites fabricated through multistage stretching extrusion. From Figure 4c, it can be seen that all the specimens exhibited shear thinning behavior, indicating that the in situ POE/(PA6/PLA) blends were non-Newtonian fluids, which was similar to the POE/PTT microfibrillar composites [15]. With the increasing of ω, the η* of POE/(PA6/PLA) blends decreased continuously. This result can be ascribed to the de-entanglement of POE chain and the PA6/PLA microfibril remain highly oriented (PA6/PLA microfibrils were solidstate at 130 • C). In addition, with the increasing of viscosity ratio of PA6 to PLA, the G , G and η* of POE/(PA6/PLA) blends increased firstly and then decreased at the same ω. When the viscosity ratio of PA6 to PLA was 2.2, the viscoelastic properties of POE/(PA6/PLA) blends was maximum, revealing that the "gourd skewers" structure microfibrils with a small diameter and length of knots was favorable to improvement the viscoelastic properties of POE/(PA6/PLA) blends than the "trepang" structure microfibrils. The viscoelastic properties of PA6-3.2 were maximum ( Figure 1). On the contrary, the minimum value of viscoelastic properties were obtained at the viscosity ratio of 0.5, which was due to the decreased of PA6-2.0 viscoelastic properties ( Figure 1) and the larger diameter of gourd-skewers structure microfibrils. The evolution mechanism of special-shaped microfibrils was shown in Figure 3. when the PA6/PLA master batches were feed into the twin screw extruder, the particles of PA6/PLA master batches broke up to form droplets under the action of shear stress. Under the action of the shear and stretch stress, the dispersed droplets occurred de-    Figure 4 shows the dependence of storage modulus(G′), loss modulus(G″), and complex viscosity (η*) on angular frequency(ω) for in situ POE/(PA6/PLA) MFCs at 130 °C. It was evident that the G′ and G″ of all the specimens increased with increasing angular frequency (Figure 4a,b). At low frequencies, the G′, G″ of POE/(PA6/PLA) blends increased linearly. At high frequencies, the frequency-dependence of G′, G″ was substantially weakened and a small platform appeared due to the frequency's response difference of PA6/PLA microfibrils physically entangled network. The information of situ microfibrils made effective contributions for not only the elastic behavior, but also the viscous behavior. Sun et al. [18] had the similar conclusion about the research of POE/PLA microfibrillar composites fabricated through multistage stretching extrusion. From Figure 4c, it can be seen that all the specimens exhibited shear thinning behavior, indicating that the in situ POE/(PA6/PLA) blends were non-Newtonian fluids, which was similar to the POE/PTT microfibrillar composites [15]. With the increasing of ω, the η* of POE/(PA6/PLA) blends decreased continuously. This result can be ascribed to the de-entanglement of POE chain and the PA6/PLA microfibril remain highly oriented (PA6/PLA microfibrils were solid-state at 130 °C). In addition, with the increasing of viscosity ratio of PA6 to PLA, the G′, G″ and η* of POE/(PA6/PLA) blends increased firstly and then decreased at the same ω. When the viscosity ratio of PA6 to PLA was 2.2, the viscoelastic properties of POE/(PA6/PLA) blends was maximum, revealing that the "gourd skewers" structure microfibrils with a small diameter and length of knots was favorable to improvement the viscoelastic properties of POE/(PA6/PLA) blends than the "trepang" structure microfibrils. The viscoelastic properties of PA6-3.2 were maximum (Figure 1). On the contrary, the minimum value of viscoelastic properties were obtained at the viscosity ratio of 0.5, which was due to the decreased of PA6-2.0 viscoelastic properties ( Figure 1) and the larger diameter of gourd-skewers structure microfibrils.   Figure 5 shows the DSC curves of in situ POE/(PA6/PLA) MFCs. It can be seen that the peak melting temperature of PLA at about 169 °C and that of PA6 at about 223 °C were not affected by the viscosity ratio of PA6/PLA. In addition, the melting enthalpy of PLA was almost constant, while that of PA6 decreased with increasing the viscosity ratio of PA6/PLA. These results indicated that the morphology of PLA/PA6 microfibrils ("gourd skewers" or "trepang") had negligible effect on the melting temperature of both PLA and PA6. Due to the poor crystallization kinetics of pure PLA, there was not crystallization behavior during the cooling process (Figure 5d) [54]. However, an obvious cold crystallization peak with the peak temperature of about 100 °C can be seen during the heating cycle, which was used to calculate the crystallization degree of PLA. In addition, the crystallization temperature of PA6 decreased, while that of POE were almost constant with the viscosity ratio of PA6/PLA increased (Figure 5e-f). This result indicated that the morphology of PLA/PA6 microfibrils had negligible effect on the melting temperature of matrix POE. The decreased of crystallization temperature of PA6 can be ascribed to the decreased of the PA6 molecular chain's the mobility with the increasing viscosity of PA6. Figure 6. shows the crystallization degree of PLA, PA6, and POE in MFCs. It can be seen that the crystallization degree of PLA was 28.0% and POE was 2.2%, respectively, and were hardly affected by the viscosity ratio of PA6/PLA. In addition, the crystallization  Figure 5 shows the DSC curves of in situ POE/(PA6/PLA) MFCs. It can be seen that the peak melting temperature of PLA at about 169 • C and that of PA6 at about 223 • C were not affected by the viscosity ratio of PA6/PLA. In addition, the melting enthalpy of PLA was almost constant, while that of PA6 decreased with increasing the viscosity ratio of PA6/PLA. These results indicated that the morphology of PLA/PA6 microfibrils ("gourd skewers" or "trepang") had negligible effect on the melting temperature of both PLA and PA6. Due to the poor crystallization kinetics of pure PLA, there was not crystallization behavior during the cooling process (Figure 5d) [54]. However, an obvious cold crystallization peak with the peak temperature of about 100 • C can be seen during the heating cycle, which was used to calculate the crystallization degree of PLA. In addition, the crystallization temperature of PA6 decreased, while that of POE were almost constant with the viscosity ratio of PA6/PLA increased (Figure 5e-f). This result indicated that the morphology of PLA/PA6 microfibrils had negligible effect on the melting temperature of matrix POE. The decreased of crystallization temperature of PA6 can be ascribed to the decreased of the PA6 molecular chain's the mobility with the increasing viscosity of PA6. Figure 6. shows the crystallization degree of PLA, PA6, and POE in MFCs. It can be seen that the crystallization degree of PLA was 28.0% and POE was 2.2%, respectively, and were hardly affected by the viscosity ratio of PA6/PLA. In addition, the crystallization degree of PA6 decreased with the viscosity of PA6 increasing. These results can be ascribed to the increased of the restrictions effect of crystal nucleus formation with the increasing viscosity of PA6.

Thermal Characterization
behavior during the cooling process (Figure 5d) [54]. However, an obvious cold crystallization peak with the peak temperature of about 100 °C can be seen during the heating cycle, which was used to calculate the crystallization degree of PLA. In addition, the crystallization temperature of PA6 decreased, while that of POE were almost constant with the viscosity ratio of PA6/PLA increased (Figure 5e-f). This result indicated that the morphology of PLA/PA6 microfibrils had negligible effect on the melting temperature of matrix POE. The decreased of crystallization temperature of PA6 can be ascribed to the decreased of the PA6 molecular chain's the mobility with the increasing viscosity of PA6. Figure 6. shows the crystallization degree of PLA, PA6, and POE in MFCs. It can be seen that the crystallization degree of PLA was 28.0% and POE was 2.2%, respectively, and were hardly affected by the viscosity ratio of PA6/PLA. In addition, the crystallization degree of PA6 decreased with the viscosity of PA6 increasing. These results can be ascribed to the increased of the restrictions effect of crystal nucleus formation with the increasing viscosity of PA6.   Figure 7 shows the stress-strain curves and tensile properties of POE/(PA6/PLA) MFCs along to extrusion direction. It was seen that the stress-strain curve of POE/(PA6/PLA) blends showed typical response of elastomeric materials. With the increasing of viscosity ratio of PA6/PLA, the special-shaped microfibrillar composites appeared multiple-yield behavior during the tensile test. As shown in Figure 7b, the tensile strength of MFCs increased firstly and then decreased with the viscosity ratio of PA6/PLA, which agreed with Young's modulus of POE/(PA6/PLA) (Figure 7a). When the viscosity ratio of PA6/PLA was 2.2, the POE/(PA6/PLA) MFCs had the highest tensile strength and Young's modulus. This result revealed that "gourd skewers" with small diameter and length of knots were favorable to improvement the strength and modulus of POE/(PA6/PLA) blends compared to the "trepang" structure microfibrils. In addition, the elongation at break of MFCs decreased firstly and then increased with increasing the viscosity ratio of PA6/PLA. When the viscosity ratio of PA6/PLA was 0.5, the maximum value of elongation at break can be obtained. This result can be ascribed to the large specific surface area of "gourd skewers" was favorable to the transfer of stress.  Figure 7 shows the stress-strain curves and tensile properties of POE/(PA6/PLA) MFCs along to extrusion direction. It was seen that the stress-strain curve of POE/(PA6/PLA) blends showed typical response of elastomeric materials. With the increasing of viscosity ratio of PA6/PLA, the special-shaped microfibrillar composites appeared multiple-yield behavior during the tensile test. As shown in Figure 7b, the tensile strength of MFCs increased firstly and then decreased with the viscosity ratio of PA6/PLA, which agreed with Young's modulus of POE/(PA6/PLA) (Figure 7a). When the viscosity ratio of PA6/PLA was 2.2, the POE/(PA6/PLA) MFCs had the highest tensile strength and Young's modulus. This result revealed that "gourd skewers" with small diameter and length of knots were favorable to improvement the strength and modulus of POE/(PA6/PLA) blends compared to the "trepang" structure microfibrils. In addition, the elongation at break of MFCs decreased firstly and then increased with increasing the viscosity ratio of PA6/PLA. When the viscosity ratio of PA6/PLA was 0.5, the maximum value of elongation at break can be obtained. This result can be ascribed to the large specific surface area of "gourd skewers" was favorable to the transfer of stress.

Mechanical Property
creasing of viscosity ratio of PA6/PLA, the special-shaped microfibrillar composites appeared multiple-yield behavior during the tensile test. As shown in Figure 7b, the tensile strength of MFCs increased firstly and then decreased with the viscosity ratio of PA6/PLA, which agreed with Young's modulus of POE/(PA6/PLA) (Figure 7a). When the viscosity ratio of PA6/PLA was 2.2, the POE/(PA6/PLA) MFCs had the highest tensile strength and Young's modulus. This result revealed that "gourd skewers" with small diameter and length of knots were favorable to improvement the strength and modulus of POE/(PA6/PLA) blends compared to the "trepang" structure microfibrils. In addition, the elongation at break of MFCs decreased firstly and then increased with increasing the viscosity ratio of PA6/PLA. When the viscosity ratio of PA6/PLA was 0.5, the maximum value of elongation at break can be obtained. This result can be ascribed to the large specific surface area of "gourd skewers" was favorable to the transfer of stress.     Figure 8b, the tensile strength and elongation at break of MFCs decreased firstly and then increased with the increase of viscosity ratio of PA6/PLA. When the viscosity ratio of PA6/PLA was 0.5, the tensile strength and elongation at break of POE/(PA6/PLA) MFCs obtained a maximum value. This result can be ascribed to enhance of interfacial adhesion between microfibrils and POE matrix due to the large specific surface area of "gourd skewers".
Polymers 2022, 14, x FOR PEER REVIEW 10 of 12 ratio of PA6/PLA. As shown in Figure 8b, the tensile strength and elongation at break of MFCs decreased firstly and then increased with the increase of viscosity ratio of PA6/PLA. When the viscosity ratio of PA6/PLA was 0.5, the tensile strength and elongation at break of POE/(PA6/PLA) MFCs obtained a maximum value. This result can be ascribed to enhance of interfacial adhesion between microfibrils and POE matrix due to the large specific surface area of "gourd skewers".

Conclusions
In this work, the POE/(PA6/PLA) MFCs based on the bends of POE as matrix and PA6/PLA master batches as dispersed phase were successfully fabricated by using multistage stretching extrusion technology. The viscosity ratio of PA6 to PLA plays an important role in the morphology of PA6/PLA microfibrils during stretching. When the viscosity ratio of PA6/PLA was less than 2.2, the "gourd-skewers-like" structure microfibrils were obtained. Further increased the viscosity ratio of PA6/PLA to 14.2, the "trepang" structure microfibrils were obtained. The "gourd skewers" microfibrils with small diam-

Conclusions
In this work, the POE/(PA6/PLA) MFCs based on the bends of POE as matrix and PA6/PLA master batches as dispersed phase were successfully fabricated by using multistage stretching extrusion technology. The viscosity ratio of PA6 to PLA plays an important role in the morphology of PA6/PLA microfibrils during stretching. When the viscosity ratio of PA6/PLA was less than 2.2, the "gourd-skewers-like" structure microfibrils were obtained. Further increased the viscosity ratio of PA6/PLA to 14.2, the "trepang" structure microfibrils were obtained. The "gourd skewers" microfibrils with small diameter were favorable to improvement mechanical properties and viscoelastic properties of POE/(PA6/PLA) blends compared to the "trepang" structure microfibrils.