The Ultra High Molecular Weight Polyethylene (UHMWPE) has a number of remarkable properties that make it suitable for wide range of applications in industry and medicine. It is a proper material for manufacturing various parts of machines, mechanisms and devices, shoulder and hip implants and for defective bone replacement along with PTFE [
1,
2,
3,
4,
5,
6]. UHMWPE is highly resistant to impact, so it is also used for protection against penetration by metallic projectiles, especially when it is reinforced with various additives and inserts [
7,
8,
9,
10].
Since the 1960s large-scale industrial production of bulk material from UHMWPE powder is based on methods of compression molding, ram extrusion, gel extrusion and spinning, etc. [
1]. These technologies are complex and expensive, but they enable producing products of sufficiently large sizes. Not so long ago, in 2007, a new method for producing bulk material from UHMWPE powder was proposed, based on cyclic impact on the powder [
11]. Later, the authors of this work used this method in the manufacture of compacts both from pure UHMWPE and with various additives and reinforcing metal inserts [
10,
12,
13,
14].
Researchers and technologists use various additives in order to improve certain operational properties of UHMWPE, as well as other polymers. One of the types of promising additives are various forms of carbon, such as graphene particles, carbon fibers, carbon nanotubes, etc. The literature provides various, sometimes opposite, data on the effect of carbonaceous additives in UHMWPE. For example, in [
15], due to the addition of graphene nanoparticles, it was possible to achieve a reduction in the coefficient of friction by 10% and an increase in hardness by 30% compared to pure UHMWPE. In [
16], due to the addition of 10% carbon fibers to UHMWPE, the coefficient of friction was reduced by about 20%, but the wear resistance herewith fell by about 36%. Meanwhile, in [
17], due to the addition of 0.5% carbon nanofibers, the friction coefficient of UHMWPE was reduced by half (from 0.1 to 0.05), and the wear resistance was increased by 2.7 times. Obviously, the tribological characteristics of the composite significantly depend on both the content and size of carbon fibers. In [
16], fibers with a diameter of 7 microns and a length of 28 microns, and in [
17] with a diameter of 60 nm and a length of 2 microns were used. The studies described in [
18] have shown that the reinforcement of UHMWPE with carbon nanotubes (CNTs) leads to a decrease in its wear resistance. Both single-wall and multi-wall CNTs were used. In pin-on-disk tests, a layer of perfluoropolyether was applied to the surface of the UHMWPE as a lubricant. Based on the test results, the authors of [
18] suggested that CNTs act as third abrasive body to increase wear once CNT is released from bulk polymer during friction. As well as tribological properties, the mechanical characteristics of UHMWPE are also sensitive to carbon additives. According to [
19], due to the addition of 1% multi-walled carbon nanotubes (MWCNTs) to UHMWPE, the Young modulus of the material increases by 1.4 times, and the yield stress by 1.5 times. Note that in [
19], the tested material was prepared in a special way in the form of a thin (several microns thick) film. Again, in [
20] it was shown, that the addition of 0.5% carbon nanofibers to the polymer composite UHMWPE/HDPE leads to an increase in tensile strength by 32%. Let's add that in work [
21], due to the addition of 1% MWCNTs to UHMWPE, its abrasive resistance was increased by 37%, the elongation increased by 2.4 times (from 290 to 700%), and the tensile strength decreased by 27% (from 30 to 22 MPa).