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Artificial weathering was performed for 4000 h to evaluate the light stability of postused, CaCO3-filled polypropylene material recycled from garden chairs. The old chair material was recycled by applying the remelting–restabilization technique while using different stabilization systems in selected concentrations. To study the role of restabilization in the material performance, the tensile impact strength was monitored during the artificial weathering exposure. The data were compared to microphotographs of the specimens' surfaces. The effect of light on the material was further studied through yellowness index (Y.I.) determinations. The results revealed that the appropriate restabilization of the postconsumer chair material is mandatory for improving its light stability, ensuring its reuse in the original application. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1311–1318, 2003

The long-term thermal stability of postused CaCO3-filled Polypropylene was evaluated through accelerated heat aging tests for about 2000 h. The material from old garden chairs was recycled by applying the remelting-restabilization technique while using different stabilization systems in selected concentrations. To study the effect of heat aging on the material properties, crystallinity content, tensile strength, and tensile impact strength together with time to embrittlement were monitored. The results illustrate that the restabilization recipe is of crucial importance for improving the long-term thermal stability of the postused chair material, ensuring its reuse in the original application. Best long-term performance is achieved by combining a filler deactivator with appropriate heat and light stabilizer systems. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3033–3044, 2003

A remelting-restabilization technique was applied for the recycling of post-used, yellow pigmented high density polyethylene (HDPE) bottle crates. In order to evaluate the potential of the recyclate to be used in the original application, the most important parameters were investigated: processing stability, long-term heat stability and light stability. A multiple extrusion cycles procedure at different reprocessing temperatures was performed for monitoring the processing stability of the restabilized and non-restabilized material. Oven aging was applied for about 8 800 h (i.e., more than one year) to evaluate the long term thermal stability of the crate material, as manifested by melt flow rate, tensile impact strength, and time until embrittlement measurements. To evaluate the light stability of the recycled material artificial weathering was applied for about 8 000 h, whereas the tensile impact strength was monitored. The latter data were enriched with microphotographs of the specimens surface. Finally, repigmentation was used to investigate the role of new pigments on the final performance of the recycled product. The results illustrate that restabilization is mandatory for the quality improvement of post-used crates ensuring its re-use in the original application and thus making closed loop recycling possible. Autoxidation cycle of polymeric materials.

A remelting–restabilization technique was applied to evaluate the closed-loop recycling of postused, white pigmented, garden chairs made from CaCO3-filled polypropylene (PP). Analysis of the randomly collected postused chairs showed only an insufficient quantity of residual active stabilizers. Different stabilization systems in selected concentrations were employed to investigate the optimum restabilization recipe for eliminating degradation effects during reprocessing. For monitoring the processing stability of the restabilized and nonrestabilized material a multiple extrusion procedure at two different reprocessing temperatures was performed. Furthermore, a repigmentation step was applied to investigate the role of the additional pigment on the processing stability of the recycled product. Finally, mechanical tests were carried out, for studying further the effect of restabilization on the mechanical performance of the recycled material. The results lead to the conclusion that restabilization for quality improvement of postused filled PP chair material during reprocessing is permitting its reuse in the original application. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2472–2485, 2002

Postconsumer recycled polypropylene, filled with 15% CaCO3was restabilized at various degrees utilizing different processing stabilizers, one of which is especially prepared to counter the deactivating effects of fillers and other moieties. The polymer was then subjected to multiple extrusion cycles for the purpose of studying the effects of the extent and temperature of reprocessing on its chemical stability. The relative effectiveness of the various restabilization recipes used was also examined. The process‐induced material degradation is primarily due to chain scission, which causes an average molecular weight reduction; its progression was monitored by measuring the decrease in viscosity. It is determined that degradation increases linearly with the extent of reprocessing while its activation energy is roughly equal to 30 kJ/mol. A simple model is built and used to quantitatively evaluate the potency of each additive used; it presumes that the protection of each individual stabilizer may be explicitly factored out in a product expression. These results suggest useful ways of optimizing stabilization according to the particular processing and product requirements. © 2002 Wiley Periodicals, Inc. Adv Polym Techn 21: 260–267, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10026

A selective dissolution/reprecipitation technique was applied for the effective recovery of Polyamide 6 (PA 6) and Polyamide 6 6 (PA 6 6) from their mixtures. The proposed process comprises mainly selective polyamide dissolution in an appropriate solvent at a specific temperature, reprecipitation of the polymer from the solution by addition of a nonsolvent, washing, and drying. A model mixture of virgin PA 6 and PA 6 6 pellets was initially tried, whereas in a following stage the selective dissolution technique was applied for the recovery of a PA-copolymer layer from a three-layered bottle end product also containing HDPE and EVA. End-group analysis, dilute solution viscometry, and differential scanning calorimetry were used to assess the molecular weight preservation and crystallizability of the recycled polyamides. The recycled materials demonstrated excellent retention of the properties studied, although in the copolymer case, due to hydrolysis, a molecular weight decrease was detected, accompanied with a slight compositional shift, favoring the PA6 6 presence in the final product. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1924–1930, 2002

Post-use high-density polyethylene, almost devoid of any stabilizing agents, was restabilized in various degrees and subjected to multiple extrusion cycles at different reprocessing temperatures for assessing its chemical stability. The process-induced material degradation was attributed primarily to long-chain branching caused by crosslinking. It was monitored by an increase in viscosity and evaluated on the basis of an approximate expression derived using fundamental principles of macromolecular rheology. It was determined that long-chain branching increases with temperature and the extent of processing, while decreasing with the amount of restabilizing agent added. A simple model was developed to quantitatively describe the progress of the chemical change by relating it to key material and operational variables. Besides constituting a useful method of monitoring and controlling polymer modification during processing, this model suggests ways of optimizing stabilization according to the particular processing and product requirements. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2207–2217, 2001

Artificial weathering was applied for about 8000 h to evaluate the light stability of postconsumer high-density polyethylene (HDPE) material recycled from bottle crates. For recycling the remelting-restabilization technique was applied. To study the effect of the restabilization, the tensile impact strength was monitored during the artificial weathering exposure. The data were compared with microphotographs of the specimens' surface. Repigmentation was used to evaluate the role of new pigments on the final performance of the recycled material. The repigmented grades were further studied by colorimetric determinations of the color difference (ΔE) during artificial weathering. The results illustrate that the restabilization is mandatory for improving the light stability of the postconsumer crate material, ensuring its re-use in the original application. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1118–1127, 2000

A remelting–restabilization technique was applied for the recycling of postused, yellow-pigmented high-density polyethylene (HDPE) bottle crates. Multiple extrusion cycles procedure, at different reprocessing temperatures, was performed for monitoring the processing stability of the restabilized and nonrestabilized material as reference. In addition, mechanical properties measurements were carried out, to study further the effect of restabilization on the performance of the recycled material. Finally, repigmentation was used to investigate the role of new pigments on the final recycled product. The results illustrate that restabilization of postused crates leads to careful reprocessing without severe degradation, which is an essential prerequisite for reuse in the original application. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1775–1785, 1999