The properties of recycled PVC bottle compounds. 2: Reprocessing stability

Abstract

Following a study of the mechanical properties of recycled W C recovered from post-consumer bottles, this study focuses on the effects of recycled material on processing. In particular, the effects of multiple recycling were studied to investigate any problems that may arise due to the repeated incorporation of recycled material into the processing stream. Batches of recycled flake and powder as well as pure but processed bottle flake material were subjected to simulated multiple recycling using a Torque Rheometer. Ten minutes at 170°C followed by granulation represented one recycle. Molecular weight and Infi-ared analyses were performed to assess the degree of degradation occurring during reprocessing. The results indicated a rapid degradation of the two recycled grades when compared with the purer bottle flake W C . Further multiple recycling was then performed on bottle flake mixed with 0.2Oh polyethylene, which showed that the PE impurities accelerate the degradation process. Finally, the effects of restabilizing by adding new bottle flake material at each step were investigated. It was shown that surprisingly small levels of new material (30?h) prevented degradation, even after 15 recycle steps. IlWTRODUCTION n a previous paper (11, the mechanical behavior of I recycled post-consumer W C material was studied.The recycled material was obtained from the Reprise bottle separating plant, operated by EVC compounds Ltd. Two forms of the recycled material were studied: granules and pulverized powder. In addition, the behavior of virgin WC and pure but reprocessed bottle flake were studied as a comparison. It was found that the strength, ductility, fatigue, and Esc resistance of the recycled flake were considerably reduced compared with the virgin W C . i-effect predominantly due to the presence of large mpurity particles. Pulverization of the material did improve the performance but not to the levels of the virgin material. GPC analysis showed that there were no significant Werences in the molecular weight distributions of the three materials, and an impurity analysis showed that the levels of impurity were 0.3% by weight, mainly of PET, PE, and paper.In this study, attention turns to the reprocessing behavior of these materials. If recycled PVC is to be incorporated into the raw material stream in greater quantities, it will be important to fully understand the effects it has on processing behavior. There are cer-tainly concerns about the possibility of accelerated degradation during processing caused by recycled material, and so this part of the study is aimed at addressing these concerns, determining the causes of any accelerated degradation, and assessing the degree of restabilization that may be needed.There has been a large amount of work performed on the thermal, oxidative, and thenno-mechanical degradation of W C . It has been found that with predominantly thermal degradation, where little oxygen is present, the degradation proceeds by a process of dehydrochlorhation, which leads to the formation of conjuga...

Effect of wood sawdust content on rheological and structural changes, and thermo‐mechanical properties of PVC/sawdust composites

“…This is probably another reason for the decrease in mechanical properties of the composites, as previously discussed. In this work, we did not attempt to measure the carbonyl content as a parameter to monitor a change in thermal stability, since the carbonyl groups in the PVC/sawdust composites could be derived from various sources, namely from oxidation reactions in PVC molecules,11 from decompositions of lignin in sawdust,21 and from stabilizers in PVC compound 22…”

Processability, rheology, and thermal, mechanical, and morphological properties of postconsumer poly(vinyl chloride) bottles and cables

“…The torque value for the RB recyclate increased at the initial stage (0–4 min) and then decreased before approaching a steady state. Work by Arnold and Maund6 suggested that the increase in the torque of a PVC compound indicated some degradation (after three or four recycling passes) with the formation of polyene sequences. However, this was not the case in our work.…”

“…In this work, peaks at three different wave numbers were of interest: (1) 2916 cm −1 for CH stretching, (2) 1720 cm −1 for carbonyl groups, and (3) 1579 cm −1 for polyene sequences. Equations (1) and (2) were used to determine the carbonyl and polyene indices, the details being given elsewhere:6 …”

“…The study suggested that the reclaimed PVC bottles were recyclable at real processing times. Arnold and Maund6 studied the multiple recycling of PVC bottles through molecular weight determination and IR analysis. The results indicated that the degradation of PVC could be detected by the formation of polyene sequences, dehydrochlorination, and crosslinking, the degradation accelerating with small polyethylene (PE) contents and the depletion of the stabilizer contents.…”

Effect of Additives on Weathering

“…The properties of recycled PVC bottles were dramatically and adversely affected because of contamination with polyethylene which accelerated thermal degradation during processing. 219 …”