Development of Tensile Properties and Crystalline Conformation of Recycled Polypropylene by Re-Extrusion Using a Twin-Screw Extruder with an Additional Molten Resin Reservoir Unit

Plastic mechanical recycling is an attractive method for reducing the amounts of waste plastics. However, the alterations in the mechanical properties (degradation) in recycled plastics is a limitation to the material’s mechanical recycling. In this study, the mechanical recycling was enhanced by the addition of a “molten resin reservoir” unit at the end of the twin-screw extruder. Recycled polypropylene (RPP) obtained from a household was re-extruded with this developed extrusion unit. The tensile properties, type of crystalline, and conformation of polypropylene polymorphs were evaluated and compared for virgin polypropylene (VPP), recycled polypropylene (RPP) without extrusion (RPP-original), and RPP with extrusion by using a new type of extruder (RPP-extrusion). It could be found that the tensile properties of RPP-extrusion were improved, so as to be similar to those of VPP. In addition, the conformation of RPP-extrusion was similar to that of VPP by increasing the ratio between the helix and parallel band. This study succeeded in regenerating the tensile properties and inner structures in recycled PP, which could prolong the used lifetime and decrease the amount of waste from single-use plastic.

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Effects of a Twin-Screw Extruder Equipped with a Molten Resin Reservoir on the Mechanical Properties and Microstructure of Recycled Waste Plastic Polyethylene Pellet Moldings

Polymers ◽

10.3390/polym13071058 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1058

Author(s):

Hikaru Okubo ◽

Haruka Kaneyasu ◽

Tetsuya Kimura ◽

Patchiya Phanthong ◽

Shigeru Yao

Keyword(s):

Mechanical Properties ◽

Mechanical Performance ◽

Value Added ◽

Industrial Applications ◽

Twin Screw Extruder ◽

Screw Extruder ◽

Polymer Properties ◽

Wide Range ◽

Twin Screw ◽

Recycled Plastics

Each year, increasing amounts of plastic waste are generated, causing environmental pollution and resource loss. Recycling is a solution, but recycled plastics often have inferior mechanical properties to virgin plastics. However, studies have shown that holding polymers in the melt state before extrusion can restore the mechanical properties; thus, we propose a twin-screw extruder with a molten resin reservoir (MSR), a cavity between the screw zone and twin-screw extruder discharge, which retains molten polymer after mixing in the twin-screw zone, thus influencing the polymer properties. Re-extruded recycled polyethylene (RPE) pellets were produced, and the tensile properties and microstructure of virgin polyethylene (PE), unextruded RPE, and re-extruded RPE moldings prepared with and without the MSR were evaluated. Crucially, the elongation at break of the MSR-extruded RPE molding was seven times higher than that of the original RPE molding, and the Young’s modulus of the MSR-extruded RPE molding was comparable to that of the virgin PE molding. Both the MSR-extruded RPE and virgin PE moldings contained similar striped lamellae. Thus, MSR re-extrusion improved the mechanical performance of recycled polymers by optimizing the microstructure. The use of MSRs will facilitate the reuse of waste plastics as value-added materials having a wide range of industrial applications.

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Preparation of Polypropylene/Sisal Fiber Composites and Study on the Fiber Orientation

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.989-994.581 ◽

2014 ◽

Vol 989-994 ◽

pp. 581-586

Author(s):

Rong Yuan Chen ◽

Zan Huang ◽

Wei Zou ◽

Hai Chen Zhang ◽

Jin Ping Qu

Keyword(s):

Tensile Properties ◽

Fiber Orientation ◽

Extrusion Direction ◽

Tensile Tests ◽

Fiber Composites ◽

Sisal Fiber ◽

Twin Screw Extruder ◽

Screw Extruder ◽

Twin Screw ◽

Better Than

The polypropylene/sisal fiber composites were prepared by twin screw extruder and vane extruder, respectively. The tensile test specimens perpendicular to the extrusion direction and parallel to the extrusion direction were prepared from the extruded composites, respectively. SEM observation showed that fiber orientation of sisal fiber in the composites was not obvious when the content of sisal fiber not more than 15wt%. When the content of sisal fiber was 15wt%, the ability to orientate of sisal fiber in the composite prepared by vane extruder was better than that of in the composite prepared by twin screw extruder, which the fiber orientation of sisal fiber was obvious along the extrusion direction in the composite. Tensile tests showed that the tensile properties of the composite parallel to the extrusion direction with 15wt% sisal fiber prepared by vane extruder were the best compared with other composites in this work. The results illustrated that the orientation of sisal fiber in the composites was beneficial to the improvement of the tensile properties of the composites.

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Degradation of Styrenic Plastics during Recycling: Accommodation of PP within ABS after WEEE Plastics Imperfect Sorting

Polymers ◽

10.3390/polym13091439 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1439

Author(s):

Charles Signoret ◽

Pierre Girard ◽

Agathe Le Guen ◽

Anne-Sophie Caro-Bretelle ◽

José-Marie Lopez-Cuesta ◽

...

Keyword(s):

Response Surface Methodology ◽

Design Of Experiments ◽

Tensile Properties ◽

Response Surface ◽

Impact Resistance ◽

Average Diameter ◽

Contamination Rate ◽

Twin Screw Extruder ◽

Screw Extruder ◽

Twin Screw

With the development of dark polymers for industrial sorting technologies, economically profitable recycling of plastics from Waste Electrical and Electronical Equipment (WEEE) can be envisaged even in the presence of residual impurities. In ABS extracted from WEEE, PP is expected to be the more detrimental because of its important lack of compatibility. Hence, PP was incorporated to ABS at different rates (2 to 8 wt%) with a twin-screw extruder. PP was shown to exhibit a nodular morphology with an average diameter around 1–2 µm. Tensile properties were importantly diminished beyond 4 wt% but impact resistance was decreased even at 2 wt%. Both properties were strongly reduced as function of the contamination rate. Various potential compatibilizers for the ABS + 4 wt% PP system were evaluated: PPH-g-MA, PPC-g-MA, ABS-g-MA, TPE-g-MA, SEBS and PP-g-SAN. SEBS was found the most promising, leading to diminution of nodule sizes and also acting as an impact modifier. Finally, a Design Of Experiments using the Response Surface Methodology (DOE-RSM) was applied to visualize the impacts and interactions of extrusion temperature and screw speed on impact resistance of compatibilized and uncompatibilized ABS + 4 wt% PP systems. Resilience improvements were obtained for the uncompatibilized system and interactions between extrusion parameters and compatibilizers were noticed.

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Tensile Properties and Morphology of Polylactic Acid (PLA)/Ethylene Vinyl Acetate (EVA)

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.735.57 ◽

2015 ◽

Vol 735 ◽

pp. 57-60

Author(s):

Abdul Manan Siti Najihah ◽

Zurina Mohamad

Keyword(s):

Mechanical Properties ◽

Tensile Properties ◽

Polylactic Acid ◽

Vinyl Acetate ◽

Ethylene Vinyl Acetate ◽

Morphological Properties ◽

Twin Screw Extruder ◽

Screw Extruder ◽

Twin Screw ◽

The One

In this study, ethylene vinyl acetate (EVA) was blended with Polylactic acid (PLA) in order to enhance the mechanical properties of PLA. PLA/EVA blend was melt blended in a twin screw extruder and compression molding with various EVA content (0-20% by weight) and the tensile and morphological properties were examined. The morphological behaviours play an important role in influencing the tensile properties of PLA. The smaller discrete EVA particle in PLA matrix had increased the properties of PLA compared with the one with elongated morphology.

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