Structure and Mechanical Properties of Composites of Poly(6‐hexanelactam) Combining Solid Tribological Additives and Reinforcing Components

Abstract

Summary: Three types of composites of polyamide 6 (PCL) with hybrid tribological additives were synthesized via anionic adiabatic “in situ” polymerization of 6‐hexanelactam (ε‐caprolactam) initiated with metallic sodium and activated with either cyclic trimer of phenyl isocyanate or diphenylmethane 4,4′‐diisocyanate. Combinations of the additives and their maximum applied concentrations (in wt.‐%) were the following: MoS2/graphite(G)/oil(O) (5/16/9), short carbon fibers (CF)/G/O (5/20/10), and copper phthalocyanine (CPC) (7). Dynamic mechanical thermal analysis (DMTA) indicates a secondary (β) transition at about −65 °C and the main (α) transition at temperatures close to 20 °C; the storage modulus passes through a shallow maximum as a function of the total content of additives. Tensile creep and indentation creep concurrently evidenced some increase in compliance with rising fraction of incorporated compounds. Stress‐strain tests in flexure show that flexural strength and toughness monotonically decreased with the content of MoS2/G/O or CF/G/O, whereas the flexural modulus passed through a flat maximum. On the other hand, the strength and modulus were decreasing with CPC content, while toughness and Charpy impact tests showed some improvement.

Modelling of mechanical properties of Pa6 based reinforced graphite and graphite nano platelets composites using different aspect ratio

“…Figure 3 is a comparison of tensile moduli normalised by the modulus of the individual PA6 matrix of PA6/G composites from the literature. The literature-based composites show that TM increase is much lower than the increase in the G20/20 and G40/10 systems of the present study at the same or equivalent filler loading (Horský et al , 2004; Horský et al , 1999; Kim and Jeong, 2010). At the highest loading of 25 G Wt.%, the relative modulus of 3.12 obtained in the G20/20 system is 136% higher than the 1.32 obtained at 16 G Wt.% as reported by Horský et al (2004), and 122% lower than the 2.92 obtained at 20 G Wt.% loading in the G20/20 system.…”

“…The literature-based composites show that TM increase is much lower than the increase in the G20/20 and G40/10 systems of the present study at the same or equivalent filler loading (Horský et al , 2004; Horský et al , 1999; Kim and Jeong, 2010). At the highest loading of 25 G Wt.%, the relative modulus of 3.12 obtained in the G20/20 system is 136% higher than the 1.32 obtained at 16 G Wt.% as reported by Horský et al (2004), and 122% lower than the 2.92 obtained at 20 G Wt.% loading in the G20/20 system. When compared with the modulus of 2.76 for 15 G Wt.% [close to 16 G Wt.% of Horský et al (2004)], the modulus is still 109% higher.…”

“…At the highest loading of 25 G Wt.%, the relative modulus of 3.12 obtained in the G20/20 system is 136% higher than the 1.32 obtained at 16 G Wt.% as reported by Horský et al (2004), and 122% lower than the 2.92 obtained at 20 G Wt.% loading in the G20/20 system. When compared with the modulus of 2.76 for 15 G Wt.% [close to 16 G Wt.% of Horský et al (2004)], the modulus is still 109% higher. Horský et al (1999) used pure G to make PA6/G composites for which the highest normalised TM obtained was 1.19 at 20 G Wt.% loading.…”

“…These values are still higher than the literature values at equivalent loadings. At 20 G Wt.%, the relative TM of 2.12 in G40/10 is 72% higher than the value of 1.23 obtained at 19.2 G Wt.% loading of Horský et al (2004). While the steady increase in modulus with G loading in G20/20 may be attributed to good dispersion, increased interfacial area and the intrinsic modulus of G, the lower modulus values obtained at equivalent loading in the G40/10 system are possibly because of three main reasons.…”

“…Increasing the degree of crystallinity (Gubbels et al , 1995) of composites (with a semi-crystalline matrix) can also serve the same purpose. During crystal growth, fillers are pushed aside into the amorphous phase as to constitute the excluded volume (Horský et al , 2004). Modified forms of carbon such as the GNP are preferentially used in place of G to attain the same result.…”