Reactive mixing of PET and PET/PP blends with glycidyl methacrylate–modified styrene‐b‐(ethylene‐co‐olefin) block copolymers

Styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene (SEBS) and styrene‐b‐(ethylene‐co‐propylene) (SEP, SEPSEP) block copolymers with different styrene contents and different numbers of blocks in the copolymer chain were functionalized by melt radical grafting with glycidyl methacrylate (GMA) and employed as compatibilizers for PET‐based blends. Binary blends of PET with both functionalized (SEBS‐g‐GMA, SEP‐g‐GMA, SEPSEP‐g‐GMA) and neat (SEBS, SEP, SEPSEP) copolymers (75 : 25 w/w) and ternary blends of PET and PP (75 : 25 w/w) with various amounts (2.5–10 phr) of both modified and unmodified copolymers were prepared in an internal mixer, and their properties were evaluated by SEM, DSC, melt viscosimetry, and tensile and impact tests. The roles of the chemical structure, grafting degree, and concentration of the various copolymers on blend compatibilization was investigated. The blends with the grafted copolymers showed a neat improvement of phase dispersion and interfacial adhesion compared to the blends with nonfunctionalized copolymers. The addition of grafted copolymers resulted in a marked increase in melt viscosity, which was accounted for by the occurrence of chemical reactions between the epoxide groups of GMA and the carboxyl/hydroxyl end groups of PET during melt mixing. Blends with SEPSEP‐g‐GMA and SEBS‐g‐GMA, at concentrations of 5–10 phr, showed a higher compatibilizing effect with enhanced elongation at break and impact resistance. The effectiveness of GMA‐functionalized SEBS was then compared to that of maleic anhydride–grafted SEBS. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2201–2211, 2005     

Rheology‐morphology correlation in PET/PP blends: Influence of type of compatibilizer

Rheological and morphological properties of melt processed poly(ethylene terephthalate) (PET)/polypropylene (PP) blends are presented. Two types of compatibilizer namely, PP‐g‐MA <MA= maleic anhydtide> and Elvaloy PTW, an n‐butyl acrylate glycidyl methacrylate ethylene terpolymers, were incorporated at different levels to the PET/PP blend system. Scanning electron microscopy revealed that the dispersed particle sizes were smaller in PET‐rich blends than PP‐rich blends. With increasing compatibilizer level, the refinement of morphology was observed in both the systems. However, the blends compatibilized with PTW showed a more refined (smaller) particle size, and at high PTW content (10 wt%), the morphology changed towards monophasic. The significant changes in morphology were attributed to the highly reactive nature of PTW. Investigation of rheological properties revealed that the viscosity of the PET/PP blends followed typical trends based on mixing rule, which calculates the properties of blends based on a linear average. Incorporation of PP‐g‐MA into the blends resulted in a negative deviation in the viscosity of the system with respect to that of the neat blend. With increasing PP‐g‐MA level, the deviation became more pronounced. Although incorporation of the compatibilizer into the PET/PP blends refined the morphology, it led to a drastic drop of viscosity, which could be attributed to inherently lower molecular weight of the compatibilizer. In the case of the blends compatibilized by PTW, a strong positive deviation in rheological properties was observed that confirmed the stronger interaction between the blend components due to reactive compatibilization process, which led to the more refined morphology in this series of blends. J. VINYL ADDIT. TECHNOL., 19:25–30, 2013. © 2013 Society of Plastics Engineers     

Valorization of poly(butylene terephthalate) wastes by blending with virgin polypropylene: Effect of the composition and the compatibilization

Blends of recycled poly(butylene terephthalate) (PBT) parts obtained from scrapped cars, and virgin polypropylene (PP), were prepared in a twin‐screw extruder at different compositions. Selected compositions were also prepared with the presence of ethylene‐co‐glycidyl methacrylate copolymer (E‐GMA) and ethylene/methyl acrylate/glycidyl methacrylate terpolymer (E‐MA‐GMA) compatibilizers. The effect of the composition and the type of compatibilizer, as well as the mixing conditions, on the morphology phase, thermal, viscoelastic behavior, and mechanical properties of the blends has been investigated. Blends PP/PBT of various composition exhibit a coarse morphology and a poor adherence between both phases, resulting in the decrease of ductility, whereas at weak deformation, PBT reinforced the tensile properties of PP. Addition of E‐GMA and E‐MA‐GMA to the PP/PBT blend exhibited a significant change in morphology and improved ductility because of interfacial reactions between PBT end chains and epoxy groups of GMA that generate EG‐g‐PBT copolymer. Moreover, thermal and viscoelastic study indicated that the miscibility of PP and PBT has been improved further and the reactions were identified. The E‐MA‐GMA results in the best improvement of ductility. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Compatibilization and toughening of immiscible ternary blends of polyamide 6, polypropylene (or a propylene—Ethylene copolymer), and polystyrene

In this work, typical ternary blends of three versatile polymers—polyamide 6, a propylene–ethylene copolymer (co‐PP), and polystyrene—were studied. As a compatibilizer, co‐PP with randomly dispersed minor ethylene units was multimonomer‐melt‐grafted in the presence of maleic anhydride, styrene, and dicumyl peroxide. The influence of the ethylene content in co‐PP and the blend composition on the performance was investigated. Scanning electron microscopy images showed an obvious decrease in the droplet size of the dispersed phase with increases in the compatibilizer content and number of ethylene units in co‐PP. Peaks of tan δ/temperature curves approaching the glass‐transition temperatures of the components were observed with dynamic mechanical thermal analysis. The improved mechanical properties implied good compatibility of the components in the blends. Significant toughening was achieved when the concentration of co‐PP was increased from 15 to 25 wt %: the elongation at break of the compatibilized blends increased dozens of times in comparison with the elongation at break of the uncompatibilized blends. The introduction of the multimonomer‐melt‐grafted co‐PP was shown to be an effective approach for improving immiscible multipolymer blends and to have practical potential. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Compatibilization of polypropylene/ poly(3‐hydroxybutyrate) blends

Blending polypropylene (PP) with biodegradable poly(3‐hydroxybutyrate) (PHB) can be a nice alternative to minimize the disposal problem of PP and the intrinsic brittleness that restricts PHB applications. However, to achieve acceptable engineering properties, the blend needs to be compatibilized because of the immiscibility between PP and PHB. In this work, PP/PHB blends were prepared with different types of copolymers as possible compatibilizers: poly(propylene‐g‐maleic anhydride) (PP–MAH), poly (ethylene‐co‐methyl acrylate) [P(E–MA)], poly(ethylene‐co‐glycidyl methacrylate) [P(E–GMA)], and poly(ethylene‐co‐methyl acrylate‐co‐glycidyl methacrylate) [P(E–MA–GMA)]. The effect of each copolymer on the morphology and mechanical properties of the blends was investigated. The results show that the compatibilizers efficiency decreased in this order: P(E–MA–GMA) > P(E–MA) > P(E–GMA) > PP–MAH; we explained this by taking into consideration the affinity degree of the compatibilizers with the PP matrix, the compatibilizers properties, and their ability to provide physical and/or reactive compatibilization with PHB. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Interface modification of compatibilized polyethylene terephthalate/polypropylene blends: Effect of compatibilization on thermomechanical properties and thermal stability

Polyethylene terephthalate (PET) and polypropylene (PP) are incompatible thermoplastics because of differences in chemical structure and polarity, hence their blends possess inferior mechanical and thermal properties. Compatibilization with a suitable block/graft copolymer is one way to improve the mechanical and thermal properties of the PET/PP blend. In this study, the toughness, dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA) of PET/PP blends were investigated as a function of different content of styrene‐ethylene‐butylene‐styrene‐g‐maleic anhydride (SEBS‐g‐MAH) compatibilizer. PET, PP, and SEBS‐g‐MAH were melt‐blended in a single step using the counter rotating twin screw extruder with compatibilizer concentrations of 0, 5, 10, and 15 phr, respectively. The impact strength of compatibilized blend with 10 phr SEBS‐g‐MAH increased by 300% compared to the uncompatibilized blend. Scanning electron microscope (SEM) micrographs show that the addition of 10 phr SEBS‐g‐MAH compatibilizer into the PET/PP blends decreased the particle size of the dispersed PP phase to the minimum level. The improvement of the storage modulus and the decrease in the glass transition temperature of the PET phase indicated an interaction among the blend components. Thermal stability of the PET/PP blends was significantly improved because of the addition of SEBS‐g‐MAH. J. VINYL ADDIT. TECHNOL., 23:45–54, 2017. © 2015 Society of Plastics Engineers     

PET/PP blending by using PP‐g‐MA synthesized by solid phase

In attempts to improve the compatibility of polypropylene (PP) with polyethylene terephthalate (PET), a maleic anhydride grafted PP (PP‐g‐MA) was evaluated as a compatibilizer in a blend of 30/70 wt % PP/PET. PP‐g‐MA was produced from isotactic homopolymer PP utilizing the technique of solid phase graft copolymerization. Qualitative confirmations of the grafting were made by Fourier transform infrared spectroscopy (FTIR). Three different weight percent of compatibilizer, PP‐g‐MA, i.e., 5, 10, and 15 wt % have been used in PP/PET blends. The compatibilizing efficiency for PP/PET blend was examined using differential scanning calorimetry (DSC), optical microscopy (OM), scanning electron microscopy (SEM) of crycrofractured surfaces, and energy dispersive X‐ray spectrum (EDAX). The results show that the grafted PP promotes a fine dispersed phase morphology, improves processability, and modifies the crystallization behavior of the polyester component. These effects are attributed to enhance phase interaction resulting in reduced interfacial tension. Also, the results show that the compatibilizing effects of the three amounts of grafted PP in blend are different and dependent on the amount used. Adding 10 wt % of compatibilizer into blend produced the finest dispersed morphology. Elemental analysis results show that PP is matrix. DSC determination revealed that the melting temperature (T_m) of the PET component declined to some extent by comparison with neat PET. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104, 3986–3993, 2007     

Effect of prior photodegradation on the biodegradation of polypropylene/poly(3‐hydroxybutyrate) blends

In this work, the effect of blend composition and previous photodegradation on the biodegradation of polypropylene/poly(3‐hydroxybutyrate) (PP/PHB) blends was studied. The individual polymers and blends with or without the addition of poly(ethylene‐co‐methyl acrylate‐co‐glycidyl methacrylate) [P(E‐MA‐GMA)] as a compatibilizer (in the case of 80/20 blend) were exposed to UV light for 4 weeks and their biodegradation was evaluated. The biodegradation of PHB phase within the blends was hindered as PHB was the dispersed phase and PP fibrous particles were observed at the surface of the blend samples after biodegradation. Previous photodegradation lessened PHB biodegradation but enhanced the biodegradation of PP and the blends within the biodegradation time studied. Photodegradation resulted in cracks at the surface of PP and the blends, which probably facilitated the biotic reactions due to an easier access of the enzymes to deeper polymer layers. It also resulted in a decrease of molecular weight of PP phase and formation of carbonyl and hydroxyl groups which were consumed during biodegradation. Size exclusion chromatography analysis revealed that only the short chains of PP were consumed during biodegradation. POLYM. ENG. SCI., 53:2109–2122, 2013. © 2013 Society of Plastics Engineers     

Acrylonitrile–butadiene rubber functionalization for the toughening modification of recycled poly(ethylene terephthalate)

The incorporation of functionalized acrylonitrile–butadiene rubber (NBR) into recycled poly(ethylene terephthalate) (PET) was introduced as an effective route for modifying the properties of PET and as a new method for PET recycling as well. To achieve modified NBR, glycidyl methacrylate (GMA) was grafted onto NBR with optimized reactive mixing, in which the highest grafting degree and lowest gel content were generated. PET/NBR blends with and without GMA functionalization were produced by melt mixing, and the mechanical properties, dynamic mechanical thermal properties, and phase morphologies of the systems were determined and compared. We found that low amounts of peroxide initiator (dicumyl peroxide) and high levels of the GMA monomer in the presence of the styrene comonomer led to the maximum grafting degree and suppressed the competing rubber crosslinking and GMA homopolymerization reactions. The blend compatibility with PET determined from dynamic mechanical thermal analysis spectra and scanning electron microscopy images was greatly improved when the NBR‐grafted GMA was used instead of the neat NBR in the blend recipes. As a result, the rubber phase dispersed in the PET matrix more finely, and the impact strength of the blend advanced very significantly. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40483.     

Toughening of recycled poly(ethylene terephthalate)/glass fiber blends with ethylene–butyl acrylate–glycidyl methacrylate copolymer and maleic anhydride grafted polyethylene–octene rubber

The aim of this study was to improve the toughness of recycled poly(ethylene terephthalate) (PET)/glass fiber (GF) blends through the addition of ethylene–butyl acrylate–glycidyl methacrylate copolymer (EBAGMA) and maleic anhydride grafted polyethylene–octene (POE‐g‐MAH) individually. The morphology and mechanical properties of the ternary blend were also examined in this study. EBAGMA was more effective in toughening recycled PET/GF blends than POE‐g‐MAH; this resulted from its better compatibility with PET and stronger fiber/matrix bonding, as indicated by scanning electron microscopy images. The PET/GF/EBAGMA ternary blend had improved impact strength and well‐balanced mechanical properties at a loading of 8 wt % EBAGMA. The addition of POE‐g‐MAH weakened the fiber/matrix bonding due to more POE‐g‐MAH coated on the GF, which led to weakened impact strength, tensile strength, and flexural modulus. According to dynamic rheometer testing, the use of both EBAGMA and POE‐g‐MAH remarkably increased the melt storage modulus and dynamic viscosity. Differential scanning calorimetry analysis showed that the addition of EBAGMA lowered the crystallization rate of the PET/GF blend, whereas POE‐g‐MAH increased it. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Phase structure and viscoelastic properties of compatibilized blends of PET and HDPE recyclates

Immiscible blends of recycled poly(ethylene terephthalate) (R‐PET), containing some amount of polymeric impurities, and high‐density polyethylene (R‐PE), containing admixture of other polyolefins, in weight compositions of 75 : 25 and 25 : 75 were compatibilized with selected compatibilizers: maleated styrene–ethylene/butylene–styrene block copolymer (SEBS‐g‐MA) and ethylene–glycidyl methacrylate copolymer (EGMA). The efficiency of compatibilization was investigated as a function of the compatibilizer content. The rheological properties, phase structure, thermal, and viscoelastic behavior for compatibilized and binary blends were studied. The results are discussed in terms of phase morphology and interfacial adhesion among components. It was shown that the addition of the compatibilizer to R‐PET‐rich blends and R‐PE‐rich blends increases the melt viscosity of these systems above the level characteristic for the respective binary blends. The dispersion of the minor phase improved with increasing compatibilizer content, and the largest effects were observed for blends compatibilized with EGMA. Calorimetric studies indicated that the presence of a compatibilizer had a slight affect on the crystallization behavior of the blends. The dynamic mechanical analysis provided evidence that the occurrence of interactions of the compatibilizer with blend components occurs through temperature shift and intensity change of a β‐relaxation process of the PET component. An analysis of the loss spectra behavior suggests that the optimal concentration of the compatibilizers in the considered blends is close to 5 wt %. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1423–1436, 2001     

Synthesis and application of MDPE‐g‐GMA as reactive compatibilizer in blends of MDPE/PET and MDPE/PA6

In the present study, glycidyl methacrylate (GMA) grafted medium density polyethylene (MDPE‐g‐GMA) was synthesized in the molten state and applied as a reactive compatibilizer in MDPE/polyamid6 (PA6) and in MDPE/poly(ethylene terephtalate) (PET) blends. Graft copolymerization of GMA onto MDPE was performed in presence and absence of styrene, with different concentrations of dicumyl peroxide (DCP) as a radical initiator. In the presence of styrene, the MDPE‐g‐GMA with 6% GMA was obtained by addition of only 0.1 phr of DCP. Furthermore, the maximum grafting was reached when 0.6 and 0.7 phr concentration of DCP for styrene containing and styrene free samples were used, respectively. Torque‐time measurement showed faster grafting reaction rate in the presence of styrene. Four MDPE‐g‐GMA samples were selected as compatibilizers in the blends. Furthermore, the effects of melt flow index and grafting content of compatibilizers on mechanical properties and morphology of the blends were investigated through tensile tests and SEM analysis. Tensile test results indicated that the presence of compatibilizers in the blends led to 250 and 133% increase in elongation at break for PA6 and PET blends, respectively. Moreover, the best tensile results for blends were obtained using MDPE‐g‐GMA with high flow ability. The average particle size of the dispersed phase decreased by 350% for PA6 and 300% for PET blends compared with nonreactive blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and evaluation of compatibilizer based on interpenetrating polymer networks (IPN) for PET/LDPE blends

The present work considers the evaluation of recycled polymers, which are generally incompatible and are degraded during recycling with fatal consequences to their thermal and mechanical properties. Regarding this subject, the synthesis of a new compatibilizer in network form was carried out in order to counter such incompatibility. In this sense, low density polyethylene (LDPE) and poly(ethylene terephthalate) (PET) were compatibilized via the implementation of an interpenetrating polymer network (IPN), which was specifically synthesized to possess chemical groups that are akin to both plastics, PET and LDPE. The effects of the relative amount of poly(acrylic acid) (PAA) in the compatibilizer and the amount in the blends of PET/LDPE were evaluated. The results show that mechanical properties and interfacial adhesion of PET/LDPE blends were modified and improved with the addition of the synthesized compatibilizer compared with a commercial compatibilizer (polyethylene grafted with maleic anhydride, PE‐g‐AA). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43704.     

Effect of a hybrid compatibilizer on the mechanical properties and interfacial tension of a ternary blend with polypropylene,poly(lactic acid), and a toughening modifier

This study examined the effect of three compatibilizers, namely, a hybrid compatibilizer composed of polypropylene‐maleic anhydride (PP‐g‐MAH) and polyethylene‐glycidyl methacrylate (PE‐g‐GMA), a single compatibilizer composed of PP‐g‐MAH, and a single compatibilizer composed of PE‐g‐GMA, on the mechanical, morphological, and rheological properties of a ternary blend of polypropylene (PP), poly(lactic acid; PLA), and a toughening modifier. The results of tensile strength, flexural strength, and impact strength tests for the ternary blends before and after hydrolysis, revealed that the ternary blend with a hybrid compatibilizer content of 3 phr exhibited better material properties than the blend containing a single compatibilizer. In the weighted relaxation spectra of the ternary blend using the Palierne emulsion model, the ternary blend containing the hybrid compatibilizer, exhibited only one relaxation spectrum peak at ∼ 0.16 s. This result suggests that the ternary blend with the hybrid compatibilizer exhibits uncharacteristic morphological properties, that is, a single‐phase microstructure. The above results suggest that the hybrid mixture is an effective compatibilizer for the ternary blend of PP, PLA, and a toughening modifier. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Effect of inclusions and blending on the mechanical performance of recycled multilayer PP/PET/SiOx films

Extending the useful life of materials through recycling has proven to be an efficient means of reducing natural resource use and limiting the production of waste. In the case of polymer‐based materials, in general, and of packaging materials, in particular, material recovery is complicated by the presence of incompatible polymers, as well as a priori undesirable contaminants such as inorganic inclusions. This article investigated the recycling of multilayer packaging material systems, based on polypropylene and silicon oxide‐coated poly(ethylene terephthalate). In particular, the effect of a compatibilization of the blend using maleic anhydride‐grafted polypropylene on the mechanical properties of the recycled material was examined. Without a compatibilizer, and at low compatibilizer concentrations, the blend exhibits a coarse morphology and is brittle. At a concentration of 5% wt of the compatibilizer, a fine morphology is obtained, and the blend shows excellent ductility. Beyond this concentration, a brittle interphase forms between the blend constituents, with a corresponding decrease in ductility. These results were confirmed by a study of strain‐induced crystallization in the blend. Furthermore, the size of the SiO_x inclusions, resulting from the fragmentation of the oxide coating during reprocessing, had no detectable influence on the mechanical properties of the recycled blend, providing that their concentration is lower than 2 × 10⁻³. This study showed that a control of both the microstructure and interface properties considerably improves the mechanical properties of the recycled material, leading to high added‐value applications. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 910–918, 2000     

Effect of the type of nylon chain‐end on the compatibilization of PP/PP‐GMA/nylon 6 blends

Polyamide and polypropylene (PP) are two important classes of commercial polymers; however, their direct mixing leads to incompatible blends with poor properties. Polypropylene functionalized with glycidyl methacrylate (PP‐GMA) was used as a compatibilizer in blends of PP and nylon 6, because of the possible reaction of ? NH₂ and ? COOH groups with the epoxide group of GMA. Two types of nylon 6 with different ratios between ? NH₂ and ? COOH groups were used. The one with higher concentration of ? COOH groups was less compatible with PP in a binary blend. When PP‐GMA was used as a compatibilizer, a better dispersion of nylon in the PP matrix was obtained together with better mechanical properties for both nylons used in this work. © 2001 Society of Chemical Industry     

Recycling PET beverage bottles and improving properties

Recycling PET from bottles has been carried out by three different extrusion methods. Under optimized processing conditions, a virgin poly(ethylene terephthalate (PET), recycled PET and a mixture of virgin and recycled PET, with and without the modifier polypropylene functionalized with maleic anhydride [PP‐graft‐MA]), were processed. Different methods were used to characterize the processed products. The results showed that the intrinsic viscosity and molecular weight decreased as the blend ratio of recycled PET was increased. This was due to thermal exposure as well as shear degradation of recycled PET. Thermal cycles of the processes used for recycling PET and its blending specimens with virgin PET show the importance of the thermal treatment in the improvement of mechanical strength and increased crystallinity. Nevertheless, the properties of the functionalized blends were improved. This behaviour is attributed to a series of chemical and physico‐chemical interactions taking place between the two components. Copyright © 2004 Society of Chemical Industry     

New synthesis methods for polypropylene‐co‐ethylene‐propylene rubber

In this research, the reinforcement of polypropylene (PP) was studied using a new method that is more practical for synthesizing polypropylene‐block‐poly(ethylene‐propylene) copolymer (PP‐co‐EP), which can be used as a rubber toughening agent. This copolymer (PP‐co‐EP) could be synthesized by varying the feed condition and changing the feed gas in the batch reactor system using Ziegler–Natta catalysts system at a copolymerization temperature of 10°C. The ¹³C‐NMR tested by a 21.61‐ppm resonance peak indicated the incorporation of ethylene to propylene chains that could build up the microstructure of the block copolymer chain. Differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and dynamic mechanical analysis (DMA) results also confirmed these conclusions. Under these conditions, the morphology of copolymer trapped in PP matrix could be observed and the copolymer T_g would decrease when the amount of PP‐co‐EP was increased. DMA study also showed that PP‐co‐EP is good for the polypropylene reinforcement at low temperature. Moreover, the PP‐co‐EP content has an effect on the crystallinity and morphology of polymer blend, i.e., the crystallinity of polymer decreased when the PP‐co‐EP content increased, but tougher mechanical properties at low temperature were observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3609–3616, 2007     

Impact modification of waste PET by polyolefinic elastomer

Waste poly(ethylene terephthalate) [PET] and a polyolefinic elastomer (POE), Engage? 8150, were melt blended in a co‐rotating twin screw extruder having initial distributive mixing followed by high shearing/stretching. Compositions having POE up to 10% with and without poly(ethylene‐co‐acrylic acid), as a compatibilizer were studied. The blends were characterized for mechanical, thermal and rheological properties as well as for morphological characteristics. Incorporation of POE improved the impact properties of PET very significantly. © 2003 Society of Chemical Industry     

The Use of Ethylene/Propylene Copolymers as Compatibilizers for Recycled Polyolefin Blends

Compatibilizing effects of ethylene/propylene (EPR) diblock copolymers on the morphology and mechanical properties of immiscible blends produced from recycled low‐density polyethylene (PE‐LD) and high‐density polyethylene (PE‐HD) with 20 wt.‐% of recycled poly(propylene) (PP) were investigated. Two different EPR block copolymers which differ in ethylene monomer unit content were applied to act as interfacial agents. The morphology of the studied blends was observed by scanning‐ (SEM) and transmission electron microscopy (TEM). It was found that both EPR copolymers were efficient in reducing the size of the dispersed phase and improving adhesion between PE and PP phases. Addition of 10 wt.‐% of EPR caused the formation of the interfacial layer surrounding dispersed PP particles with the occurrence of PE‐LD lamellae interpenetration into the layer. Tensile properties (elongation at yield, yield stress, elongation at break, Young's modulus) and notched impact strength were measured as a function of blend composition and chemical structure of EPR. It was found that the EPR with a higher content of ethylene monomer units was a more efficient compatibilizer, especially for the modification of PE‐LD/PP 80/20 blend. Notched impact strength and ductility were greatly improved due to the morphological changes and increased interfacial adhesion as a result of the EPR localization between the phases. No significant improvements of mechanical properties for recycled PE‐HD/PP 80/20 blend were observed by the addition of selected block copolymers.