Eccentric Rotor Extruder Research Articles

The study of the thermomechanical degradation and mechanical properties of PET recycled by industrial-scale elongational processing

Molecular weight degradation in a shear flow field is the main bottleneck restricting the reuse of poly(ethylene terephthalate) (PET). An innovative eccentric rotor extruder (ERE) dominated by an elongational flow field was introduced to melt, plasticize and transport PET in a simulation of the recycling process and compared with a conventional twin-screw extruder (TSE), which is based on a shear flow field. The reduction in molecular weight (Mw) induced by thermomechanical degradation in the ERE is evidently less than that in the TSE. Mechanical testing showed that compared with the recycled PET processed by the TSE, the recycled PET processed by the ERE achieved considerably higher tensile strength, while the toughness did not decline substantially. Therefore, the recycled PET processed by the ERE based on an elongational flow field still maintains a high molecular weight and excellent mechanical properties, which expands the recovery and processing performance of PET.

Short‐time fabrication of well‐mixed high‐density polyethylene/ultrahigh‐molecular‐weight polyethylene blends under elongational flow: morphology, mechanical properties and mechanism

AbstractAs linear polyethylenes, ultrahigh‐molecular‐weight polyethylene (UHMWPE) and high‐density polyethylene (HDPE) have the same molecular structure, but the large difference in viscosity between them makes it difficult to obtain well‐mixed blends. An innovative eccentric rotor extruder (ERE) generating an elongational flow was used to prepare HDPE/UHMWPE blends within short processing times. Compared with the obvious two‐phase morphology of a sample from a twin‐screw extruder observed with a scanning electron microscope, few small UHMWPE particles were observed in the HDPE matrix for a sample from the ERE, indicating the good mixing on a molecular level of HDPE/UHMWPE blends achieved by the ERE during short processing times. The morphological changes of blends prepared using the ERE evidenced the good integration of HDPE and UHMWPE even though the UHMWPE content is up to 50 wt% in the blends. Moreover, all blends retained most of the intrinsic molecular weight. The good mixing was further confirmed from the thermal, crystallization and rheological behaviors determined using differential scanning calorimetry and dynamic rheological measurements. Importantly, the 50/50 blend presented improved mechanical properties, especially super‐impact strength of 151.9 kJ m−2 with incomplete‐break fracture state. The strengthening and great toughening effects of UHMWPE on the blends were attributed to the addition of unwrapped UHMWPE long molecular chains. The effective disentanglement mechanism of UHMWPE chains under elongational flow was explained schematically by a non‐parallel three‐plate model. © 2019 Society of Chemical Industry

Properties of compression molded ultra‐high molecular weight polyethylene products pretreated by eccentric rotor extrusion

AbstractLow processing efficiency and fusion defects limit the application of ultra‐high molecular weight polyethylene (UHMWPE) in artificial joint implants. These problems result from the high melt viscosity of UHMWPE. Here, we use an eccentric rotor extruder (ERE) based on elongational flow to pretreat UHMWPE. Compression molded UHMWPE is obtained without and with ERE pretreatment (EP‐UHMWPE). The processing efficiency of EP‐UHMWPE is improved compared with direct compression molded UHMWPE. This is because the preheating time can be omitted during the molding process, and the residence time of UHMWPE in the extruder is less than 90 s. The mechanical properties and friction resistance of EP‐UHMWPE are significantly improved compared with those of direct compression molded UHMWPE. The yield strength increases from 21 MPa to 23 MPa, the tensile strength increases from 36 MPa to 46 MPa, the elongation at break increases from 610% to 700%, and the abrasion loss decreases from 1.73 mg/1000 r to 0.93 mg/1000 r when UHMWPE is subjected to ERE pretreatment. We attribute these improvements to the elongational flow enhancing the orientation and disentanglement of UHMWPE molecular chains, which in turn improves particle fusion. The molecular weight is well maintained when subjected to ERE pretreatment. UHMWPE components pretreated by ERE have good prospects in artificial joint implants. © 2019 Society of Chemical Industry

Structure-property relationship of polycarbonate/polypropylene alloys prepared via eccentric rotor extruder.

In this work, PC/PP alloys were respectively prepared by eccentric rotor extruder (ERE) and twin screw extruder (TSE). By analyzing the mechanical properties, morphology, rheological behavior and thermal properties of PC/PP alloys, the effects of processing methods on the two-phase structure and properties of PC/PP alloys were studied. The results showed that the size of the dispersed phase of PC/PP alloys was smaller and its distribution was more uniform under the elongational flow field provided by ERE. Compared to the typical sea-island phase structure provided by the shear flow field, the morphology of the alloys showed a “sea-island-fiber” phase structure under the elongational flow field. Compared to the TSE, the notched lzod impact strength of the PC/PP alloy prepared by ERE increased by 31.0%. ERE played a stronger effect on the dispersion and distribution of PC/PP alloys, which was also confirmed in the results of dynamic rheology analysis and differential scanning calorimetry. The blending method dominated by the elongational flow field could prepare PC/PP alloys with better properties.

UHMWPE/organoclay nanocomposites fabricated by melt intercalation under continuous elongational flow: Dispersion, thermal behaviors and mechanical properties

The preparation of ultra‐high‐molecular weight polyethylene (UHMWPE)/organoclay nanocomposites by continuous elongational flow technique was investigated in a novel eccentric rotor extruder (ERE). The distribution and dispersion morphologies of organo‐modified montmorillonite (OMMT) layers were revealed and observed by ash determination, wide angle X‐ray diffraction and transmission electron microscopy. The thermal and thermal‐mechanical behaviors were characterized by differential scanning calorimeter, thermal gravimetric analysis and dynamic mechanical thermal analysis. The mechanical performances was measured by tensile and impact test. The morphologies of the nanocomposites evidenced that the OMMT layers can be well intercalated or/and exfoliated by UHMWPE matrix, then the fabrication mechanism of intercalated and exfoliated OMMT structures under continuous elongational flow was discussed. The ideal dispersion of OMMT in UHMWPE matrix obviously improved the crystallinity and the mechanical properties at a certain concentration of OMMT loading, indicating that the lower OMMT addition can lead an effective strengthening and toughening for UHMWPE. POLYM. ENG. SCI., 59:547–554, 2019. © 2018 Society of Plastics Engineers

Super-toughened poly(lactic acid)/thermoplastic poly(ether)urethane nanofiber composites with in-situ formation of aligned nanofibers prepared by an innovative eccentric rotor extruder

In this work, an unprecedented methodology has been proposed to manufacture high-performance polymer composites, that is, a continuously and intensively elongational flow field created by an original and revolutionary eccentric rotor extruder (ERE) is implemented in the whole melting, plasticizing and blending process. Which subverts traditional processing methods of the shear flow field in twin-screw extruder and mixer. A super-toughed poly(lactide acid) (PLA)/thermoplastic poly(ester)urethane (TPU) nanofiber composites, possessing in-situ formed aligned TPU nanofibers (TNFs) and favorable interfacial adhesion, were prepared by the methodology, in which the TNFs could act as effective heterogeneous nucleating sites and elevate extraordinarily notch impact strength. When TPU content reaches to 25 wt%, the notch Izod impact strength reached to 73.5 and 58.3 kJ/m2 for the impact direction parallel and perpendicular to the TNFs, respectively, approximately being 30 and 20 times than that of neat PLA; and the elongation at break reach to 113%, approximately being 12 times. The unique PLA/TPU nanofiber composites manufactured in industrial approach with the novel structure of aligned TNFs is reported for the first time and exhibits prospect for development for miscellaneous functional applications.

Blown Film of m-LLDPE Using a Novel Eccentric Rotor Extruder

Metallocene linear low-density polyethylene (m-LLDPE) has superior physical and mechanical properties. While, the film blowing processability of m-LLDPE was very poor when processed under shear flow. To overcome this drawback, a novel device based on elongational flow was self-developed to process m-LLDPE. In order to investigate the effect of elongational flow on the processability improvement of m-LLDPE, five types PE were studied in this paper. All kinds of PE were prepared using this novel device and traditional single-screw extruder with molecular weight and its distribution, mechanical properties and WAXD characterization. Gel Pemeation Chromotographer (GPC) data shows that molecular weight of each resin prepared using this novel eccentric rotor extruder (ERE) is higher than that processed by traditional single screw extruder (SSE). Mechanical properties showed that tensile properties of all kinds of films blowing from ERE is better than the one from SSE. However, tear properties of m-LLDPE films made from ERE differ from LDPE or LLDPE. And had a relative low value than the one made from SSE. In addition, Wide-angle X-ray Diffraction (WAXD) results indicate that films blowing from ERE exist a partially ordered component in addition to the usual crystalline and amorphous components which can’t be achieved from SSE.

Numerical simulation of energy consumption in the melt conveying section of eccentric rotor extruders

AbstractThe polymer melt flow field in the melt conveying section of the eccentric rotor extruder was performed by the Fluid Dynamics software POLYFLOW. The rotor torque and the melt volume flow rate at each time were obtained by simulation analysis, and the energy consumption and the output in one cycle were computed with the support of the simulated data. Eventually, the specific energy consumption of the eccentric rotor, which was regarded as energy consumption evaluation index in the melt conveying process, could be calculated. The results showed that for different parameters, the eccentricity had the greatest impact on the specific energy consumption. With the increase in eccentricity, the energy consumption per unit melt transported decreased, and the extrusion output increased. The same tendency occurred for changing the pitch of the eccentric rotor, but the effect on the specific energy consumption was slight. When increasing the rotor speed and the rotor radius, the specific energy consumption increased. Experimental and theoretical methods were applied to compare the error of the simulation data under the same conditions, and the numerical simulation results were verified.

Dimensional impact of nanofillers on the micromorphology and rheology of PP/PS composites under continuous elongation flow

Three kinds of nanoscaled fillers, namely, zero‐dimensional nanosphere titanium dioxide (TiO2), one‐dimensional multi‐walled carbon nanotubes (MWCNTs), and two‐dimensional nanoplate montmorillonite (MMT), were added to the representative polypropylene (PP)/polystyrene (PS) blends by eccentric rotor extruder based on elongation flow. Confirmed from images of transmission electron microscopy and scanning electron microscopy, three kinds of nanofillers were uniformly dispersed in the blends under continuous elongation flow and the presence of nanofillers led to a marked decrease of dispersed phase size of PS. The dispersed PS particles were turned into spherical status in matrix with the addition of TiO2 and MWCNTs and showed irregular shapes in the composites with MMT. The PS particle size of PP/PS/MMT was decreased most obviously, dropping from 4.44 to 1.42 μm, which resulted in obvious improvements in storage modulus and complex viscosity of the composites. The results of wide‐angle X‐ray diffraction and dynamic mechanical analysis indicated that MMT nanoparticles were highly intercalated in PP/PS blends, which obviously improved compatibility of PP and PS. Our work certified that the two‐dimensional nanoplate MMT are better compatibilizers compared with the zero‐dimensional nanosphere TiO2 and one‐dimensional MWCNTs for PP/PS composites.

Effect of continuous elongational flow on structure and properties of poly(L‐lactic acid)/poly(ethylene glycol) blend and its organo‐modified montmorillonite nanocomposites

An innovative eccentric rotor extruder, which can generate continuous elongation flow, was used to fabricate the poly(L‐lactic acid) (PLLA)/poly(ethylene glycol) (PEG) blends and PLLA/PEG/organo‐modified montmorillonite (OMMT) nanocomposites in different PEG and OMMT content. The morphology was characterized by X‐ray diffractometer (XRD) and transmission electron microscope, showing that the OMMT nanoparticles were highly intercalated or/and exfoliated in the polymer matrix. The rheological behavior was investigated by dynamic rheological measurements, showing that the OMMT nanoparticles dispersed well in the matrix to form OMMT percolation network structure. The crystallization behavior and crystalline structures were studied by differential scanning calorimetry and XRD, respectively, showing that the addition of PEG significantly increased the crystallinity of PLLA and the presence of OMMT further speed up the crystallization rate of plasticized PLLA, which was also proved by the increasing spherulite growth rate and the formation of more perfect crystal structure acquired from polarizing optical microscopy test. However, the crystallization rate and crystallinity had a slight downward trend at high OMMT content because of the inhibition effect of OMMT percolation network structure. Moreover, the thermogravimetric analyzer measurement indicated that the presence of OMMT can significantly improve the thermal stability of PLLA/PEG blends. POLYM. COMPOS., 40:E617–E628, 2019. © 2018 Society of Plastics Engineers

Investigation on Properties of Polypropylene/Multi-walled Carbon Nanotubes Nanocomposites Prepared by a Novel Eccentric Rotor Extruder Based on Elongational Rheology

ABSTRACTThe properties of polymer matrix composites are related not only to the chemical composition of the materials but also to the processing equipment used for their preparation which has a direct influence on the microstructure of the composites. In this paper polypropylene (PP)/multi-walled carbon nanotubes (MWCNTs) nanocomposites were prepared by melt blending through a self-developed, eccentric rotor extruder (ERE). The structure and elongational deformation mechanism of an ERE were described in detail. The morphological, rheological, thermal and mechanical properties of the resulting PP/MWCNTs nanocomposites were investigated. Scanning electron microscopy (SEM) and rheological analysis showed that the MWCNTs were well dispersed in the PP matrix. The thermal stability was investigated by thermogravimetric analysis (TGA) and indicated that the addition of MWCNTs could effectively improve the thermal stability of pure PP. The percentage of crystallinity and tensile strength of the composites were improved as a result of the heterogeneous nucleation effect of the MWCNTs in the PP matrix. The research results revealed that the enhancement of the properties of PP/MWCNTs composites could be attributed to a better dispersion of the MWCNTs in the matrix as compared to samples prepared by conventional extrusion.

Linear low‐density polyethylene/poly(ethylene terephthalate) blends compatibilization prepared by an eccentric rotor extruder: A morphology, mechanical, thermal, and rheological study

ABSTRACTIn this study, various poly(ethylene terephthalate) (PET) and linear low‐density polyethylene (LLDPE) with maleic anhydride‐grafted LLDPE (LLDPE‐g‐MAH) compatibilizer were melt blended under an elongational flow. A novel extrusion device, eccentric rotor extruder (ERE), was developed to supply such flow during the process. Including morphology, mechanical properties, melting behavior, and rheological behavior were studied. The morphological study showed that the compatibility between LLDPE and PET was greatly improved with LLDPE loading up to 80 wt %. Mechanical tests indicated that LLDPE could toughen PET to some extent. Moreover, a comparison of samples prepared between ERE and conventional extruder was made and demonstrated the sample prepared by ERE can exhibit better mechanical properties. Differential scanning calorimetry results revealed that PET can promote the crystallinity of LLDPE. Rheological behavior indicated that the complex viscosity of the blends exhibited strong shear thinning phenomenon with increasing LLDPE content, particularly in high‐frequency range blend with the LLDPE weight ratio of 80 wt % was more sensitivity to shear rate than neat LLDPE. The G′‐G″ curves of the blends also revealed that the microstructure of the blends changed significantly with the addition of LLDPE which was consistent with the scanning electron micrographs that PET particles became smaller and distributed more uniform with increasing LLDPE content. Furthermore, the blends showed similar stress relaxation mechanism with adding LLDPE content from 60 to 100 wt %. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46489.

Structure-property relationships in polypropylene/poly(ethylene-co-octene)/multiwalled carbon nanotube nanocomposites prepared via a novel eccentric rotor extruder

Abstract In this work, polypropylene/poly(ethylene-co-octene)/multiwalled carbon nanotube (PP/POE/MWCNT) nanocomposites with different contents of MWCNTs were prepared by an eccentric rotor extruder to obtain engineering materials with excellent performance capability. Microphotographs (scanning electron microscopy and transmission electron microscopy) and dynamic mechanical analysis indicate that the MWCNTs were well dispersed in the polymer matrix under the elongation flow. The crystallization behavior was explored by X-ray diffraction and differential scanning calorimetry. The results show that MWCNTs promote heterogeneous nucleation and improve the T o, T c and T e values of the composites. On the basis of the rheology analysis, the complex viscosity of the PP/POE/MWCNT composites increased and formed an obvious Newton plat in the low-frequency range; both the G′ and G″ of all the samples increased monotonically, and a percolation threshold appeared for 1 wt% MWCNTs. Thus, the mechanical properties of the nanocomposites prepared under an elongation flow lead to an effective strengthening of PP/POE better than under a shear flow. This work provides a novel method based on elongational rheology to prepare engineered materials that possess excellent performance capabilities.

Preparation of poly(L-lactide)/poly(ethylene glycol)/organo-modified montmorillonite nanocomposites via melt intercalation under continuous elongation flow

Abstract An innovative eccentric rotor extruder (ERE), which can generate continuous elongation flow, was used to prepare the poly(L-lactide) (PLLA)/poly(ethylene glycol) (PEG)/organo-modified montmorillonite (OMMT) nanocomposites. The morphology was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and showed that the OMMT nanoparticles were uniformly dispersed in the matrix and mainly existed in intercalation mode. The influence of OMMT on the rheological behavior of plasticized PLLA was investigated by dynamic rheological measurements, showing greater improvement of rheological properties compared to that of PLLA/PEG blend. The crystallization behavior and crystalline structures were studied by differential scanning calorimetry (DSC) and XRD, respectively, and showed that the presence of OMMT further speeds up the crystallization rate of plasticized PLLA. However, the crystallization rate and crystallinity had a slight downward trend at high OMMT content because of the inhibition effect of the OMMT percolation network structure. Polarizing optical microscopy (POM) was further carried out and proved that the OMMT nanoparticles as a heterogeneous nucleating agent can increase the spherulite growth rate and nucleation density. The thermal stability was investigated by thermogravimetric analysis and indicated that the addition of OMMT at low concentration can improve the thermal stability of plasticized PLLA more effectively.

Structure and properties of ultrahigh molecular weight polyethylene processed under a consecutive elongational flow

Herein, a novel eccentric rotor extruder (ERE) capable of generating a continuous elongational flow was used to process ultrahigh molecular weight polyethylene (UHMWPE) without any processing aids and then compare with a conventional rotational batch mixer based on a shear flow. The morphological and rheological characterization verify that the technique based on the elongational flow could effectively reduce melting defects and yield more homogeneous morphology within the extruding samples relative to the conventional bath mixing based on a shear flow. The extrusion processing under an elongational flow can largely maintain the viscosity average molecular weight (Mη) of the UHMWPE nascent powder with only a 5.0% decrease at 200 °C, implying considerably low thermal oxidative degradation in sharp contrast to the conventional processing with significantly reduced Mη by 40.3%. Furthermore, the crystallinity for the sample prepared under an elongational flow is lower than that processed under a shear flow. These differences lies in the higher normal stress, rapider heat transfer and shorter duration generated by the ERE.

Polypropylene/polystyrene/clay blends prepared by an innovative eccentric rotor extruder based on continuous elongational flow: Analysis of morphology, rheology property, and crystallization behavior

The polypropylene (PP)/polystyrene (PS)/montmorillonite (MMT) blends were prepared by an innovative eccentric rotor extruder based on continuous elongational flow. Addition of MMT nanoparticles was found to reduce the PS droplet size and improve the compatibility of PP/PS. The MMT nanoparticles had clear intercalation and/or exfoliation structures and were located mostly at the interface of PP/PS. It was found that the intercalation and exfoliation of MMT was finished under the synergy of interfacial interaction and tensile deformation so that we called the mechanism as “MMT exfoliation mechanism induced by synergy of interface and tensile deformation”. The rheological analysis showed that incorporation of MMT led to an increase in complex viscosity to an optimum level (5 wt%), after which any further increase in MMT concentration decreased the complex viscosity. Moreover, the degree of crystallinity of blends was controlled by the heterogeneous nucleation effect of MMT and the inhibition effect of PS.

Morphology, rheology property, and crystallization behavior of PLLA/OMMT nanocomposites prepared by an innovative eccentric rotor extruder

An innovative eccentric rotor extruder, which can generate continuous elongation flow, was used to fabricate the poly(L‐lactide) (PLLA)/organo‐modified montmorillonite (OMMT) nanocomposites in different OMMT concentrations. The morphology of the nanocomposites was characterized by thermal gravimetric analyzer, X‐ray diffractometer, and transmission electron microscope. The results showed that the OMMT nanoparticles were uniformly dispersed in the PLLA matrix and mainly existed in intercalation mode. The intercalation and exfoliation process of OMMT in the eccentric rotor extruder may be a double‐side exfoliation, which is more effective than the layer‐by‐layer peeling mechanism based on the shear flow. The influence of OMMT on the rheological behavior of PLLA was investigated by dynamic rheological measurements, showing greater improvement of rheological properties for the nanocomposites. The thermo‐mechanical properties analysis indicated that significant enhancement of E′ can be seen for all the nanocomposites. Presence of intercalated OMMT platelets did not lead to a significant shift of the E″ and tan δ curves compared with that of pure PLLA. The crystallization and melting behavior was studied by differential scanning calorimetry, which indicated that the incorporation of OMMT nanoparticles slightly increased the crystallinity of PLLA matrix. The polarizing microscope was further carried out and showed that the dispersed OMMT nanoparticles acted as a heterogeneous nucleating agent to promote the crystallization of PLLA.