Study the Morphological and Mechanical Properties of Ultra-high Molecular weight polyethylene UHMWPE : Polytetrafluroethylene PTFE binary blends

In this research, it has been investigated the effect of addition High performance polymer Polytetrafluroethylene (PTFE) on the Ultra-high molecular weight polyethylene (UHMWPE) mechanical and physical properties. It has been prepared three types of blends (95:5, 90:10 and 85:15) of UHMWPE: PTFE by compression method. Stress-Strain curves of polymer blends have been showed that higher ultimate strength and Young modulus were at 95:5 and decreased gradually as wt. % PTFE increased. FTIR inspection has been also accomplished. Finally SEM results showed incompatibility between the polymers with presence of boundaries between the binary polymers phases.

Ultra-high molecular weight polyethylenediffers from the other Polyethylene types in its average molecular weight which is nearly higher than 10 6 , which can be known from measurement of viscosity [6,7].UHMWPEis a marvelous polymer with excellent physical and mechanical properties such as wear and abrasion resistance, chemical inertness, lubricity, impact toughness [8].Thein Kyu prepared three types of polymer blends from types of polyethylene; blends of different grades of polyethylene have been prepared (Ultra high molecular weight polyethylene, linear low density polyethylene, low density poly ethylene and high density polyethylene).DSC results of blends showed that compatibility between them in the melting stat which indicates that they form miscibility also UHMWPE with linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) showed some co crystallinity this is interpreted to the long chain branching of conventional LDPE.Results of stress-strain of the above blends show some linearity relationship with composition, except in the last blend UHMWPE-LDPE [9].
A new approach in science and technology developed by blending two different polymers in a way to tailor their both properties in a one single material.The developed characteristics of blends depend strongly on morphology which usually defined by size and shape of distributed . With above literature it can be found that most of them tries to improve the performance of polymer matrix using reinforcement materials usually ceramics but in this study the goal was to investigate the effect of high performance polymer addition to another matrix polymerthrough mechanical and morphological inspections.

Materials and Experimental procedure
Ultra-high mw polyethylene was acquired in powder form JIUJIANG ZHONGKE XINXING NEW MATERIAL CO., LTD China, model No. XH-804 and the mechanical properties of UHMWPE grade were shown in table (1).Polytetraflouroethylene polymers provided from ZIBO BAINAISI CHEMICAL CO., LTD-China some mechanical and physical properties are shown in table (2).properties, which is the incompatibility that led tothe segregation that shown below which corresponding with MohdAmran research [14] in the immiscibility between PP and PTFE.Also it may be seen that PTFE flakes imbedded in UHMWPE matrix and tries to expand to be mixed and united with the other polymer phase without melting since the difference in melting point between the two polymers, still the need for copolymers is necessary to enhance the compatibility and strengthening the boundaries between them.Moreover, it should be noted that some PTFE particles are deformed into a fibrous shape owing to the applied squeeze flowas well as the localized shear deformation and this can be seen in photograph (4.c) below.7) and the reason also will be the same .Table (4) shows ultimate strength and young modulus values of the blends.

Conclusion
It has been concluded that the effect of PTFE was not so good in improvement the mechanical properties including ultimate strength and Young modulus since there were decrement in both of them which can be interpreted to the incompatibility between the two polymers leading to immiscibility phenomena, which has been proved by SEM.
Still the change in the behavior of UHMWPE from soft and ductile into stiff and brittle is pronounced due to the difference structure of PTFE polymer as compared with simple structure of PE.Moreover FTIR results showed appearance of both polymers peaks with no shifting.

Where
Polymer blends have been prepared by mixing the two polymers in Nano ball mill for 15 minutes to have homogeneous mixture then placed in a stainless steel mold (150*50*4) mm preparing for hot pressing at 190 ˚C for 45 minutes and pressure 10 MPa for ten minutes to have blocks of polymer blends.Mechanical testSamples were prepared for the tensile test in accordance with ASTM D638-87[14].A computerized universal testing machine model (WDW-200D Jinan Shijin Group companychina) was used to conduct a test at a constant cross head speed of the order 5 mm/min at room temperature.Tensile load wasapplied till the failure of the sample and stress -strain curve was obtained.The modulus of elasticity was evaluated using the following equation:  =    −     ⁄ … … .(1) Study the Morphological and Mechanical Properties of Ultra-  is the stress at yield, L is the length of sample at yield and Lo is the initial length.Scanning Electron Microscope (SEM), model (Tescan VEGA-SB) made in Belgium available in Nanotechnology and Advanced Materials Research Center/ University of Technology is used to examine the morphology of polymer blends.Finally, FTIR test is performed according to (ASTM E1252) by using Fourier transform infrared spectrometer instrument (available in Material Engineering Department model (TENSOR 27) made in Germany, by (Bruker Optics Company).
Ultra-High Molecular Weight PE shows the main five peaks (2912.87,2843.92,1470.46,729 and 718 cm-1) as shown in fig (1) which indicates to Asymmetric stretching of the -CH2, symmetric stretching of the-CH2 aliphatic groups , C-H bending deformation, =CH2 out-of-plane bending and C-H rocking deformation respectively as shown in table (3)[11].
fig (4 a, b and c).Results interpreted the reasons of the in improvement in mechanical

Figure
Figure (4a,b and c) shows SEM images ofpolymer blends.