Chain extension of polyamide 6/organoclay nanocomposites

Abstract

Thermal degradation of polyamide 6 (PA6)/organoclay nanocomposites is a serious impediment to wider applications of these nanocomposites. In this study, a solution is proposed based on the well‐established use of chain extenders. As in PA6, thermal degradation, in the absence of moisture, produces broken polymer chains with amide end groups, a chain extender with anhydride functionalities, known to be strongly reactive with amide groups, was used to reconnect the chains. Experiments conducted using a laboratory twin‐screw extruder were first checked, through transmission electron microscopy observations, to have produced good organoclay intercalation and exfoliation into PA6. Following from this, samples with the chain extender added were produced and characterized. The data obtained were conclusive in the effectiveness of the chain extender: for the chain extended nanocomposites, there is an enhancement in the value of the complex viscosity by 7 times and in the storage modulus by 88 times, while the tensile modulus increased by 57% compared with the neat PA6. The nonchain extended nanocomposite achieved in comparison an enhancement of 2 times the value of the complex viscosity and 19 times the storage modulus while the tensile modulus increased by 53% compared to the neat PA6. These data provide conclusive proof on the rationale that anhydride functionalities should be sought when developing chain extenders for PA6 nanocomposites. POLYM. ENG. SCI., 59:1233–1241 2019. © 2019 Society of Plastics Engineers

Chain extension of recycled PA6

“…In the absence of water as it is the case in practice during industrial extrusion, scission of the thermally weakest bond, the alkyl‐amide linkage, occurs resulting in amide end group (OCNH 2 ) and vinyl end group (CHCH 2 ) smaller chains . All the evidence to date from previous research and our most recent work is that the amide functionality is the one which is the most reactive (see work by Loontjens and Plum , Buccella et al , and Tuna ). Thus, an effective chain extender for PA6 thermally degraded in the absence of water is one that has high amide reactivity.…”

“…The recycled pellets were then dried in a vacuum oven at 80°C for 12 h ready for chain extension in the twin extruder. The chain extender‐PA6 dosage was kept constant at 1 wt% deemed to be sufficient from previous work , noting that the stochiometry of the polymer chain extension reaction is such that very little chain extender is required. Also from preliminary trials, zones temperature profile of 230–260–260–260–260°C and screw speed of 100 rpm were found to produce stable extrusion conditions.…”

Investigation of Effects of a Polymeric Chain Extender on the Properties of Recycled Poly (Butylene Terephthalate)

“…PBT/1.5 EPO örneğinde karbonil grubuna ait 1711cm -1 'deki pikin (C=O gerilmesi) yüksekliğinde azalma, diğer örneklerin spektrumlarında ise değişimin olmadığı görülmektedir. Bu bulgu, termal bozunma ve düşük zincir uzatıcı konsantrasyonlarının örneklerin FTIR spektrumunda değişimlerin izlenmesine olanak vermemesi şeklinde yorumlanabilir [33,34]. Gd.…”

Long‐chain branching of polyethylene terephthalate: Rheological/thermal properties of polyethylene terephthalate/carbon nanotube nanocomposite

“…The results showed that the nanocomposites produced in the presence of a chain extender had a significant increase in the complex viscosity and the storage modulus. [ 24 ]…”