Recycled Poly Research Articles

Rheological and Thermal Behavior of Recycled PET Modified by PMDA

In this work pyromellitic dianhydride (PMDA) was used as the chain extender to increase the molecular weight of the recycled poly(ethylene terephthalate) (R-PET) and improve the rheological properties of the R-PET. The reaction was performed in a Brabender torque rheometer. The rheological and thermal characterization were performed by means of a fusion index instrument and a differential scanning calorimeter (DSC ) to compare the effectiveness of the chain extending reaction of different percentages of PMDA. The experimental results showed that compared with the unmodified R-PET, the addition of PMDA decreased the melt flow index and increased the viscosity of the R-PET. In addition, increased crystallization temperatures ( ) were observed with the modified R-PET. It was also found that the modified R-PET with the concentration of 1.0wt% PMDA exhibited the lowest MFI.

Compatibilization of recycled poly(ethylene terephthalate) and polypropylene blends: Effect of polypropylene molecular weight on homogeneity and compatibility

AbstractThe effectiveness of compatibilizers in enhancing the dispersion of polypropylene (PP) at various molecular weights in recycled polyethylene terephthalate (RPET) was elucidated. The idea of incorporating PP of different molecular weights evolved from the intention of simultaneously recycling the PET bottles together with the PP‐based bottle caps, which are often of low molecular weight (Mw). Three grades of PP with known molecular weights were blended with RPET at various loadings of compatibilizers. Morphological analyses suggest that the dispersion of the PP particles was more homogeneous, and the average particle size was smaller when low Mw PP was incorporated. This indicates that the interaction between the compatibilizer and PP particles was more intense with the presence of a large number but shorter PP molecular chains. Moreover, specimens containing low Mw PP were found to remain homogeneous regardless of compatibilizer and PP content in the RPET/PP blends. The homogeneity of the blends significantly affected their mechanical performance as well. Higher stiffness, yield strength, deformability, and toughness were observed when low Mw PP was incorporated, regardless of PP and compatibilizer loadings. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Effects of different types of polyethylene on the morphology and properties of recycled poly(ethylene terephthalate)/polyethylene compatibilized blends

AbstractRecycled poly(ethylene terephthalate) (R‐PET) was blended with four types of polyethylene (PE), linear low density polyethylene (LLDPE; LL0209AA, Fs150), low density polyethylene (LDPE; F101‐1), and metallocene‐LLDPE (m‐LLDPE; Fv203) by co‐rotating twin‐screw extruder. Maleic anhydride‐grafted poly(styrene‐ethylene/butyldiene‐styrene) (SEBS‐g‐MA) was added as compatibilizer. R‐PET/PE/SEBS‐g‐MA blends were examined by scanning electron microscopy (SEM), differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), and mechanical property testing. The results indicated that the morphology and properties of the blends depended to a great extent on the miscibility between the olefin segments of SEBS‐g‐MA and PE. Due to the proper interaction between SEBS‐g‐MA and LDPE (F101‐1), most SEBS‐g‐MA, located at the interface between two phases of PET and LDPE to increase the interfacial adhesion, lead to better mechanical properties of R‐PET/LDPE (F101‐1) blend. However, both the poor miscibility of SEBS‐g‐MA with LLDPE (LL0209AA) and the excessive miscibility of SEBS‐g‐MA with LLDPE (Fs150) and m‐LLDPE (Fv203) reduced the compatibilization effect of SEBS‐g‐MA. DSC results showed that the interaction between SEBS‐g‐MA and PE obviously affected the crystallization of PET and PE. DMA results indicated that PE had more influence on the movement of SEBS‐g‐MA than PE did. Copyright © 2010 John Wiley & Sons, Ltd.

Composites of Recycled PET Reinforced with Short Glass Fiber

Composites of recycled poly(ethylene terephthalate) (PET) and short glass fibers (GFs) in different compositions (0, 20, 30, and 40 wt% of GFs) with optimized microstructures and high mechanical performance were obtained through melt processing. Composites showed appropriate dispersion and distribution and suitable bonding of the GF throughout the PET matrix, using either recycled bottle-grade PET in its degraded form or in a solid-state polymerized (SSP) form and GFs treated with either aminosilane or epoxysilane coupling agents. The high level of reinforcement of these PET/GF composites was confirmed by comparison of the experimental elastic modulus values of PET/GF composites with theoretical ones obtained using the Halpin–Tsai model. An important aspect highlighted by this study is that although it has been stated in the literature that this is only possible with the use of twin-screw extruders, these PET/GF composites with optimized microstructure and with high mechanical performance were compounded using a single-screw extruder with a double-flight barrier screw. In general, slightly better mechanical strengths were achieved for the composites based on the SSP recycled PET, which may be associated with its highly entangled amorphous phase arising from its higher molecular weight.

The role of crystalline, mobile amorphous and rigid amorphous fractions in the performance of recycled poly (ethylene terephthalate) (PET)

The action of thermo-mechanical degradation induced by mechanical recycling of poly(ethylene terephthalate) was simulated by successive injection moulding cycles. Degradation reactions provoked chain scissions and a reduction in molar mass mainly driven by the reduction of diethyleneglycol to ethylene glycol units in the flexible domain of the PET backbone, and the formation of –OH terminated species with shorter chain length. The consequent microstructural changes were quantified taking into account a three-fraction model involving crystalline, mobile amorphous (MAF) and rigid amorphous fractions (RAF). A remarkable increase of RAF, to a detriment of MAF was observed, while the percentage of crystalline fraction remained nearly constant. A deeper analysis of the melting behaviour, the segmental dynamics around the glass-rubber relaxation, and the macroscopic mechanical performance, showed the role of each fraction leading to a loss of thermal, viscoelastic and mechanical features, particularly remarkable after the first processing cycle.

One step forward to a sustainable green solution for extruded foam PVC building products

AbstractThis paper is dedicated to the development of a robust and cost‐effective formulation to maximize the use of recycled poly(vinyl chloride) (PVC) back into its virgin compounds. This study concludes that a balanced stabilizer and lubricant formulation will overcome the detrimental effects of repeated heat history on the recycled/regrind PVC. The developed formulation using up to 70% of recycled/regrind PVC has been successfully implemented in the extrusion process for manufacturing high‐quality foam PVC profiles for the building industry. As a result, this study takes a huge step forward toward a green and sustainable solution for PVC applications. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers

Influence of the Recycling Process on the Fire‐Retardant Properties of PP/EPR Blends

AbstractThe fire‐retardant properties of a recycled poly(propylene)‐based material were investigated and compared to the non‐recycled formulation. An intrinsic intumescent system and zinc borate were used to flame‐retard these polymers. By mass loss calorimetry, the best results were obtained with 20 wt.‐% of additives. Synergisms between AP765 and ZB were observed in the non‐recycled blends but not in the recycled ones. Solid‐state NMR showed that chemical reactions during the decomposition process were leading to the formation of borophosphates, reinforcing the efficiency of the intumescent char. From a ‘physical’ point of view, it was shown that the fire retardant properties of the materials are related to the formation speed of the intumescent structure and not on the char thickness. magnified image

Processing and characterization of recycled poly(ethylene terephthalate) blends with chain extenders, thermoplastic elastomer, and/or poly(butylene adipate‐co‐terephthalate)

AbstractPoly(ethylene terephthalate) (PET) resin is one of the most widely used thermoplastics, especially in packaging. Because thermal and hydrolytic degradations, recycled PET (RPET) exhibits poor mechanical properties and lacks moldability. The effects of adding elastomeric modifiers, chain extenders (CE), and poly(butylene adipate‐co‐terephthalate), PBAT, as a toughener to RPET on its moldability and mechanical property were investigated. Melt blending of RPET with CE, thermoplastic elastomer (TPE), and/or PBAT was performed in a thermokinetic mixer (K‐mixer). The blended materials were then injection molded to produce tensile specimens. Various techniques were used to study the mechanical properties, rheological properties, compatibility, and crystallization behavior of the RPET blends. By melt blending with proper additives, recycled PET regained its moldability, thereby enabling the recycling of RPET. Furthermore, the addition of CE greatly enhanced the mechanical properties of RPET. While the RPET and TPE blends also showed improved mechanical properties, the improvement was less significant and the blends were often immiscible due to the difference in polarities between RPET and TPE. Finally, it was found that the mechanical properties of RPET blends depended on the prior thermal history of the material and could be improved with an extra annealing step that increased the degree of crystallinity. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Morphology and Properties of Injection-Moulded Recycled Poly(Ethylene Terephthalate)/Poly(Ethylene Octene) Blends

Recycled poly(ethylene terephthalate) (r-PET) was blended with poly(ethylene octene) (POE) and glycidyl-methacrylate-grafted poly(ethylene octene) (mPOE). The morphology and thermal properties of injection-moulded blends through the thickness of impact specimens were investigated. A remarkable difference was found in the through-thickness morphology and thermal properties of the injection-moulded blends. The three-layered structure (namely the skin, subskin, and core layers) showed a hierarchical structure. Scanning electron microscopy showed that the orientation of the dispersed-phase particles in the skin and subskin layers was much higher than that in the core layer. Differential scanning calorimetry indicated that the skin and core layers had the same component content, but the core layer had a higher degree of crystallinity than the skin layer.

Influence of the reactive processing of recycled poly(ethylene terephthalate)/poly(ethylene‐co‐glycidyl methacrylate) blends

AbstractThe effect of the amount of reactive additive and screw speed during extrusion on the morphological characteristics and mechanical performance of recycled poly(ethylene terephthalate)(RPET) was investigated. With an increase in the ethylene–glycidyl methacrylate copolymer (E–GMA) additive content, a gradual increase in the Izod impact strength of the RPET/E–GMA blends was initially recorded. Subsequent increases in the E–GMA content to above 13.5 wt % led to a drastic enhancement in the toughness of the blends. Meanwhile, the density of the blends decreased with increasing amount of the additive E–GMA. The toughness and density of the blends were found to be dependent on the screw rotation speed during the extrusion. In addition, ductile and microporous structures were observed on the Izod impact fracture surfaces. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Preparation of Recycled Polyvinyl Alcohol) (PVA)/Iodine Polarizing Film

To precisely identify the effect of preparation conditions on the polarizing efficiency (PE) of recycled poly(vinyl alcohol) (PVA)/iodine complex film, PVA film and PVA/iodine polarizing film were prepared by using recycled nonwoven PVA with a number-average degree of polymerization (Pn) of 1700, syndiotactic diad (s-diad) content 54.6%, and degree of saponification (DS) 97.6%. We investigated the effects of various conditions such as soaking time, temperature of I2/KI aqueous solution, draw ratio, and temperature of aqueous boric acid solution on the transmittance and PE of recycled PVA/iodine complex film. Maximum transmittance and PE values of recycled PVA/iodine complex film were 41.2% and 99.8%, respectively. It was found that the recycled PVA/iodine polarizing film showed effective transmittance and PE values comparable with those of commercial PVA/iodine polarizing film.

Role of a compatibilizer in the structure and micromechanical properties of recycled poly(ethylene terephthalate)/polyolefin blends with clay

AbstractThe comparison of the degree of crystallinity and the micromechanical properties in the blends of recycled amorphous poly(ethylene terephthalate) (PET) with isotactic polypropylene (iPP) and high‐density polyethylene (HDPE) with a compatibilizer in different proportions is reported. The physical study of the composites of the compatibilized blends and clay is also discussed. The analysis, performed by means of wide‐angle X‐ray scattering and differential scanning calorimetry techniques, permits us to describe, at microscale level, the role of the compatibilizer on the structure and microhardness of the polymer blends that we studied. The results reveal that PET was incompatible with both iPP and HDPE. However, the presence of the compatibilizer, a styrene–ethylene/butylene–styrene block copolymer grafted with maleic anhydride, allowed the compatibilization of these polymers. In the PET/iPP blends, the clay seemed to have a nucleating effect on the iPP and also induced a hardness increase in the compatibilized blends. On the other hand, in case of PET/HDPE, the crystallinity of these samples (pure blends, blends with compatibilizer, and blends with compatibilizer plus clay) only depended on their composition. Similarly to the PET/iPP blends, the addition of clay induced an increase in the hardness of the compatibilized blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Effect of flyash content, particle size of flyash, and type of silane coupling agents on the properties of recycled poly(ethylene terephthalate)/flyash composites

AbstractRecent time's polymer waste disposal is a challenging task as the quantity of polymer waste is increasing day by day. Here particulate composites have been developed from recycled poly(ethylene terephthalate) filled with flyash. Flyash of different particle sizes have been used, and effect of particle size and flyash content on the mechanical properties of composites has been analyzed. Tensile and flexural properties of the composites are found to increase with increase in filler content up to 15% and after that decreases due to the agglomeration of flyash particles. SEM studies also showed good dispersion at lower loadings. The use of silane coupling agents was found to increase the flyash/WPET interaction there by increase in mechanical properties is observed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Toughening of recycled poly(ethylene terephthalate) with clay‐compatibilized rubber phase

AbstractRecycled bottle‐grade PET (rPET) is a valuable low‐cost polymeric material. However, enhancement of its mechanical properties is necessary for many applications. This work is focused on clay‐reinforced/compatibilized rPET/elastomer system. Although the clay addition to various rPET/elastomer blends caused a remarkable refinement of structure, more pronounced for clay with less polar modification, both a gain or decrease in strength and toughness occurred, whereas an increase in modulus was found for all systems. This is a consequence of simultaneous complex affecting many parameters by clay and both antagonistic and synergistic combination of respective effects. Best results were found for low contents of EPR rubber and its preblending with clay. The presented results indicate that a suitable combination of nanosilicates with rubber can lead to rPET materials with fairly enhanced properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Superficial modification in recycled PET by plasma etching for food packaging

AbstractAn oxygen plasma treatment has been used to improve the adhesion of amorphous hydrogenated carbon (a‐C:H) films onto surfaces of recycled poly(ethylene terephthalate) (PET). Modifications produced by the oxygen plasma on the PET surface in chemical bonds and morphology were investigated by X‐ray photoelectron spectroscopy and atomic force microscopy, respectively. Contact angle measurements were used to study the changes in the surface wettability. Adhesion of the a‐C:H film onto the PET surface was investigated by the tape test method. It was observed that the improvement in film adhesion is in good correlation with the increase in surface roughness, due to plasma etching, and with the appearance of oxygen‐related functional groups at the surface. The results of this study indicate that a‐C:H‐coated recycled PET can be used in food packaging. The a‐C:H film could be used as a functional barrier to reduce or prevent migration of contaminants from the polymer to the package content. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Recycled poly(ethylene terephthalate)/linear low‐density polyethylene blends through physical processing

AbstractPoly(styrene‐ethylene/butylene‐styrene) (SEBS) was used as a compatibilizer to improve the thermal and mechanical properties of recycled poly(ethylene terephthalate)/linear low‐density polyethylene (R‐PET/LLDPE) blends. The blends compatibilized with 0–20 wt % SEBS were prepared by low‐temperature solid‐state extrusion. The effect of SEBS content was investigated using scanning electron microscope, differential scanning calorimeter, dynamic mechanical analysis (DMA), and mechanical property testing. Morphology observation showed that the addition of 10 wt % SEBS led to the deformation of dispersed phase from spherical to fibrous structure, and microfibrils were formed at the interface between two phases in the compatibilized blends. Both differential scanning calorimeter and DMA results revealed that the blend with 20 wt % SEBS showed better compatibility between PET and LLDPE than other blends studied. The addition of 20 wt % of SEBS obviously improved the crystallizibility of PET as well as the modulus of the blends. DMA analysis also showed that the interaction between SEBS and two other components enhanced at high temperature above 130°C. The impact strength of the blend with 20 wt % SEBS increased of 93.2% with respect to the blend without SEBS, accompanied by only a 28.7% tensile strength decrease. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Effect of Clay Content and Speed Screw Rotation on the Crystallization and Thermal Behaviors of Recycled PET/Clay Nanocomposites

Nanocomposites of recycled poly(ethylene terephthalate) (rPET) containing 2.5 wt% and 5.0 wt% of montmorillonite modified with organophilic quaternary ammonium salt (DELLITE 67G) were prepared by melt compounding using a co-rotating twin-screw type extruder with two organoclay contents were used: 2.5 wt% and 5.0 wt% and were prepared using two different rotation speeds: 150 and 250 rpm. Thermal characterization (analysis) of the nanocomposites was performed using differential scanning calorimetry (DSC) analysis. The results from DSC measurements showed that the addition of organoclay affects recycled PET's crystallization for two screw rotation speeds studies. The nucleating effect of organoclay was investigated. Morphological analysis using Transmission Electron Microscopy (TEM) revealed the presence of fully exfoliated clay platelets in samples prepared at 150 rpm.

Morphology and properties of microfibrillar composites based on recycled poly (ethylene terephthalate) and high density polyethylene

Microfibrillar composites (MFCs) from recycled high density polyethylene (R-HDPE)/recycled poly (ethylene terephthalate) (R-PET) (75/25 w/w) were made through reactive extrusion and post-extrusion strand stretching. The resultant MFCs could be processed at HDPE processing temperature. The compatibility between microfibers and R-HDPE matrix was improved through compatibilizers. Of the three compatibilizers evaluated, ethylene glycidyl methacrylate copolymer (E–GMA) performed the best. The addition of compatibilizers did not obviously change the size of R-PET fibers in MFCs. The toughness of MFC was significantly enhanced, and R-PET phase did not crystallize when 5% E–GMA was used. The process of manufacturing MFCs provides a way to recycle commingled plastics, and MFCs would be potential matrices for natural fiber polymer composites.

Influence of chain extension on the compatibilization and properties of recycled poly(ethylene terephthalate)/linear low density polyethylene blends

Polymeric methylene diphenyl diisocyanate (PMDI) was added as chain extender to a blend of recycled poly(ethylene terephthalate) (R-PET) and linear low density polyethylene (LLDPE) with compatibilizer of maleic anhydride- grafted poly(styrene–ethylene/butadiene–styrene) (SEBS- g-MA). Hydroxyl end groups of PET can react with both isocyanate groups of PMDI and maleic anhydride groups of SEBS- g-MA, which are competing reactions during reactive extrusion. The compatibility and properties of the blends with various contents of PMDI were systemically evaluated and investigated. WAXD results and SEM observations indicated that chain extension inhibits the reaction between PET and SEBS- g-MA. As the PMDI content increased, the morphology of dispersed phase changed from droplet dispersion to rodlike shape and then to an irregular structure. The DSC results showed that the crystallinity of PET decreased in the presence of PMDI, and the glass transition temperature ( T g) of PET increased with addition of 0–0.7 w% PMDI. The impact strength of the blend with 1.1 w% PMDI increased by 120% with respect to the blend without PMDI, accompanied by only an 8% tensile strength decrease. It was demonstrated that the chain extension of PET with PMDI in R-PET/LLDPE/SEBS- g-MA blends not only decreased the compatibilization effect of SEBS- g-MA but also hindered the crystallization of PET.

Influence of liquid crystalline polymer and recycled PET as minor blending components on rheological behavior, morphology, and thermal properties of thermoplastic blends

AbstractIn this study, the potential of recycled poly(ethylene terepthalate) (rPET) as a well‐defined reinforcing material for the in situ microfibrillar‐reinforced composite (iMFC) was investigated in comparison with that of liquid crystalline polymer (LCP). Each dispersed phase (LCP or rPET) was melt blended with high density polyethylene (PE) by using extrusion process. The rheological behavior, morphology, and the thermal stability of LCP/PE and rPET/PE blends containing various dispersed phase contents were investigated. All blends and LCP exhibited shear thinning behavior, whereas Newtonian fluid behavior was observed for rPET. The incorporation of LCP or rPET into PE significantly improved the processability. A potential of rPET as a processing lubricant by bringing down the melt viscosity of the blend system was as good as LCP. The elongated LCP domains were clearly observed in as‐extruded strand. Although the viscosity ratio of the rPET/PE system was lower than that of the LCP/PE blend system, most rPET domains appeared as small droplets. An addition of LCP and rPET into the PE matrix improved the thermal resistance significantly in air but not in nitrogen. The obtained results suggested the high potential of rPET as a processing aid and good thermally resistant material similar to LCP. Copyright © 2009 John Wiley & Sons, Ltd.