scholarly journals Enhancing Chain Mobility of Ultrahigh Molecular Weight Polyethylene by Regulating Residence Time under a Consecutive Elongational Flow for Improved Processability

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2192
Author(s):  
Xiaochuan Chen ◽  
Xiaotong Wang ◽  
Yanhong Feng ◽  
Jinping Qu ◽  
Dingshan Yu ◽  
...  
Keyword(s):  
Residual Stress ◽  
Molecular Weight ◽  
Residence Time ◽  
Elongational Flow ◽  
Ultrahigh Molecular Weight Polyethylene ◽  
Polymeric Chain ◽  
Thermal Oxidative Degradation ◽  
Chain Entanglement ◽  
Chain Mobility ◽  
Ultrahigh Molecular Weight

Improving the processability of ultrahigh molecular weight polyethylene (UHMWPE) and understanding the effect of the polymeric chain mobility has long been a challenging task. Herein, we show that UHMWPE without any processing aids can be processed at a lower temperature of 180 °C compared to conventional processing temperatures (~250 °C) under a continuous elongational flow (CEF) by using an eccentric rotor extruder (ERE). By probing the effect of the residence time of UHMWPE samples under a CEF on the morphology, rheological behavior and molecular orientation, we find that the long polymer chains of UHMWPE are apt to orientate under a consecutive volume elongational deformation, thereby leading to a higher residual stress for the extruded sample. Meanwhile, the residence time of samples can regulate the polymeric chain mobility, giving rise to the simultaneous decrease of the melting defects and residual stress as well as Hermans orientation function with increasing residence time from 0 to 60 s. This also engenders the enhanced diffusion of UHMWPE segments, resulting in a defect-free morphology and higher entanglement with lower crystallinity but without causing obvious thermal oxidative degradation of UHMWPE. This interesting result could originate from the fast chain entanglement and particle welding enabled by a desirably short residence time, which could be explained by the empirical, entropy-driven melting explosion mechanism.

scholarly journals Elongational Flow Field Processed Ultrahigh Molecular Weight Polyethylene/Polypropylene Blends with Distinct Interlayer Phase for Enhanced Tribological Properties

Polymers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1933
Author(s):  
Xiaochuan Chen ◽  
Xiaotong Wang ◽  
Changlin Cao ◽  
Zhongke Yuan ◽  
Dingshan Yu ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Shear Flow ◽  
Flow Field ◽  
Tribological Properties ◽  
Elongational Flow ◽  
Ultrahigh Molecular Weight Polyethylene ◽  
Wear Loss ◽  
Fatigue Wear ◽  
Ultrahigh Molecular Weight ◽  
Processing Modes

Herein, we produced a series of ultrahigh molecular weight polyethylene/polypropylene (UHMWPE/PP) blends by elongational-flow-field dominated eccentric rotor extruder (ERE) and shear-flow-field dominated twin screw extruder (TSE) respectively and presented a detailed comparative study on microstructures and tribological properties of UHMWPE/PP by different processing modes. Compared with the shear flow field in TSE, the elongational flow field in ERE facilitates the dispersion of PP in the UHMWPE matrix and promotes the interdiffusion of UHMWPE and PP molecular chains. For the first time, we discovered the presence of the interlayer phase in blends with different processing modes by using Raman mapping inspection. The elongational flow field introduces strong interaction to enable excellent compatibility of UHMWPE and PP and induces more pronounced interlayer phase with respect to the shear flow field, eventually endowing UHMWPE/PP with improved wear resistance. The optimized UHMWPE/PP (85/15) blend processed by ERE displayed higher tensile strength (25.3 MPa), higher elongation at break (341.77%) and lower wear loss of ERE-85/15 (1.5 mg) compared to the blend created by TSE. By systematically investigating the microstructures and mechanical properties of blends, we found that with increased content of PP, the wear mechanism of blends varies from abrasive wear, fatigue wear, to adhesion wear as the dominant mechanism for two processing modes.

scholarly journals Gamma Rays Induced Modification in Ultrahigh Molecular Weight Polyethylene (UHMWPE)

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Suveda Aarya ◽  
Pawan Kumar ◽  
Mamta Bhatia ◽  
Sanjeev Kumar ◽  
Jyotsna Sharma ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Gamma Ray ◽  
Polymeric Materials ◽  
Ultrahigh Molecular Weight Polyethylene ◽  
Oscillatory Behavior ◽  
Morphological Properties ◽  
Polymeric Chain ◽  
X Ray Diffraction ◽  
Ultrahigh Molecular Weight ◽  
Radiation Induced

Modifications taking place in ultrahigh molecular weight polyethylene (UHMWPE) films due to gamma ray radiation-induced and investigated in correlation with the applied doses. Films were irradiated in a vacuum at room temperature by a 1.25 MeV Co60 a source with doses ranging from 0 to 300 kGg. The optical, chemical, structural, and surface morphological properties of the irradiated and unirradiated UHMWPE films were investigated by UV-Visible, FTIR, XRD, and SEM, respectively. The band gap E g decreases with increasing radiation dose and coloration effects have been seen at higher doses. FTIR spectra show an oscillatory behavior in the transmittance intensities without affecting in their peak positions. Number of small absorption peaks can be seen clearly which may be due to the cross-linking of the polymeric chain. No significant change in crystalline peak has been found in the X-ray diffraction pattern indicating the structural stability of the polymer. The morphology of the smooth topography of the polymer samples to change rougher one polymeric sample shows the formation of microvoids on the surface of the polymeric materials with the increase of the doses from 0 to 300 kGy.

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