Compatibilization of PE/PS and PE/PP blends. I. Effect of processing conditions and formulation

The objective of this work was to study the effectiveness of low‐cost commercial compatibilizers and several processes (internal mixer, single‐ and twin‐screw extruders) for two types of plastic blends: high‐density polyethylene/polypropylene and high‐density polyethylene/polystyrene blends, to gain insight into the recycling of wastes from those frequently encountered mixed plastics. Blends going from a pure A to a pure B component, with and without a compatibilizer, were prepared using an internal mixer, a corotating twin‐screw extruder, as well as a single‐screw extruder to follow an industrial‐convenient process. In both cases, the analyses of blend morphologies highlighted the poor adherence between the two phases in the uncompatibilized blends. Compatibilized blends display better adherence between phases and the ability to process blends made from both single‐ and twin‐screw extruders. When adding a compatibilizer, the viscosity of each blend (PE/PP or PE/PS) increased due to a better adhesion of the phases. Charpy impact tests showed that the presence of the compatibilizer in PE/PS blends increased their impact properties. Indeed, the improvement of the adhesion between the two phases enabled stress transfer at the interface. A single‐screw extruder seems to be efficient as a processing method on an industrial scale when a compatibilizer is used. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2475–2484, 2003     

Mechanical properties and morphology of polylactide,linear low‐density polyethylene,and their blends

Melt blending of linear low density polyethylene (LLDPE) and polylactide (PLA) was performed in an extrusion mixer with post extrusion blown film attachment with and without compatibilizer‐grafted low density polyethylene maleic anhydride. The blend compositions were optimized for tensile properties as per ASTM D 882‐91. On the basis of this, LLDPE 80 [80 wt % LLDPE and 20 wt % poly(L ‐lactic acid) (PLLA)] and MA‐g‐low‐density polyethylene 80/4 (80 wt % LLDPE, 20 wt % PLLA, and 4 phr compatibilizer) were found to be an optimum composition. The blends were characterized according to their mechanical, thermal, and morphological behavior. Fourier transform infrared spectroscopy revealed that the presence of compatibilizer enhanced the blend compatibility to some extent. The morphological characteristics of the blends with and without compatibilizer were examined by scanning electron microscopy. The dispersion of PLLA in the LLDPE matrix increased with the addition of compatibilizer. This blend may be used for packaging applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Morphological stability of postconsumer PET/HDPE blends

Summary The morphological stability and the mechanical properties of postconsumer polyethylene terephthalate (PET) and high density polyethylene (HDPE), at different composition with and without compatibilizer were investigated. The blends were prepared in an internal mixer and in a twin screw-extruder at different stretching ratio. For uncompatibilized blends, (previously prepared by extrusion), the particle size of the dispersed phase increases after being reprocessed in an internal mixer. However, in the case of compatibilized blend the particle size remains constant. Consequently, the compatibilizer reduces interfacial mobility, coalescence effects and stabilizes the morphology. The mechanical properties are also modified by the presence of the compatibilizer, mainly the elongation at break. Received: 14 January 2000/Accepted: 16 August 2000     

Morphological factors affecting the permeation resistance of nanocomposite blend films

The micro‐ and nanoscale morphologies of thin nanocomposite films comprising an immiscible nylon 6/polyethylene blend reinforced with modified sodium montmorillonite were found to substantially affect water vapor transmission rates (WVTRs). Maleic anhydride‐grafted high‐density polyethylene was incorporated as a compatibilizer between the nylon and polyethylene phases. Preferential incorporation of an organosilicate nanoclay in the nylon phase had a secondary effect on the overall blend morphology and thermal properties. Different degrees of phase continuity in the nanocomposite blend system were studied for their effect on WVTRs by varying the relative viscosities of the polymer phases. Transmission electron and atomic force microscopy were utilized to reveal the morphologies of the nanocomposite blends. POLYM. ENG. SCI., 54:1341–1349, 2014. © 2013 Society of Plastics Engineers     

Highly filled polyolefin plastomer formulations for possible PVC replacement in flooring

Calcium carbonate highly filled composites of a polyolefin plastomer (POP), and its blends with postconsumer linear low‐density or high‐density polyethylene (PC‐LLDPE or PC‐HDPE) were prepared and evaluated. The mechanical properties of compounded POP and its blends were compared with those of a PVC–calcium carbonate formulation used for flooring applications. Tensile and impact properties of calcium carbonate‐filled POP composites compare very favorably to the PVC‐based formulation at filler loadings as high as 200 phr. Moreover, postconsumer LLDPE or HDPE can replace at least 50% of the POP in these composites without affecting their main properties. DSC analyses indicate that the synergism occurring in mechanical properties for some of the blend compositions, may be related to the ability of the individual polymers to cocrystallize in the respective blends. This article presents the results of a preliminary study. Continued research is expected to contribute toward a complete characterization of the compounded POP/postconsumer PE blends to establish if they can replace plasticized PVC compounds in some or all flooring applications. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1156–1168, 1999     

Low‐density polyethylene/plasticized tapioca starch blends with the low‐density polyethylene functionalized with maleate ester: Mechanical and thermal properties

In this study, the mechanical and thermal properties of low‐density polyethylene (LDPE)/thermoplastic tapioca starch blends were determined with LDPE‐g‐dibutyl maleate as the compatibilizer. Mechanical testing for the evaluation of the impact strength and tensile properties was carried our as per standard ASTM methods. Thermogravimetric analysis and differential scanning calorimetry were also used to assess the thermal degradation of the blends. Scanning electron micrographs were used to analyze fracture and blend morphologies. The results show significant improvement in the mechanical properties due to the addition of the compatibilizer, which effectively linked the two immiscible blend components. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1109–1120, 2006     

Morphological and rheological properties of (low‐density polyethylene)/thermoplastic starch blend: investigation of the role of high elastic network

Rheological and morphological properties of low‐density polyethylene (LDPE) and thermoplastic starch (TPS) with low‐density polyethylene‐grafted‐maleic anhydride as a compatibilizer were investigated. The results showed that the circularity of the droplets decreased with increasing TPS content. The presence of compatibilizer led to finer morphology and higher continuity. The rheological analyses showed that TPS and compatibilizer can increase elasticity and viscosity of the blend dramatically. In addition, the compatibilizer enhanced the compatibility of the blends, as evidenced by the shifting of the relaxation time peak of TPS to longer times. The rheological properties of the neat components and their blends were discussed by the Carreau‐Yasuda and fractional Zener models. The fractional Zener model results proved the existence of network structure in the compatibilized blends. The transient properties of blends showed that TPS and compatibilized blends had strong overshoot compared with the uncompatibilized blend, owing to the formation of high elastic network in their structure. J. VINYL ADDIT. TECHNOL., 20:250–259, 2014. © 2014 Society of Plastics Engineers     

Blends of polyamide 6 with low‐density polyethylene compatibilized with ethylene–methacrylic acid based copolymer ionomers: Effect of neutralizing cations

Blends of polyamide 6 with low‐density polyethylene compatibilized with sodium‐, zinc‐, and lithium‐neutralized ethylene—methacrylic acid ionomers were investigated at 11, 33, and 55 wt % neutralization of the ionomers. Blends of polyamide 6 with low‐density polyethylene without a compatibilizer had poor properties characteristic of incompatible polymer–polymer blends. After the addition of a compatibilizer, tensile properties improved, the modulus drop associated with melting increased to higher temperatures, and the dispersed phase size decreased. The improvement of the mechanical properties and thermomechanical properties was less with the acid copolymer than with the ionomers. Overall, ionomers neutralized with sodium, zinc, or lithium showed little difference in their compatibilization efficiency. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The effect of zinc oxide addition on the compatibilization efficiency of maleic anhydride grafted high‐density polyethylene compatibilizer for high‐density polyethylene/polyamide 6 blends

A high‐density polyethylene with grafted maleic anhydride units has been investigated as a compatibilizer for high‐density polyethylene with polyamide 6. The material acts as an effective compatibilizer, causing a marked reduction in dispersed phase size as well as an increase in tensile strength and toughness. Compatibilizer also affects the glass‐transition temperature, crystallization kinetics, and amount of crystalline material for certain blend compositions. The addition of zinc cations, which are effective in increasing ethylene‐acid copolymer compatibilizer performance in low‐density polyethylene/polyamide blends, has little, if any, effect on compatibilizer performance in these high‐density polyethylene/polyamide blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3871–3881, 2007     

The Effect of Epoxidized Natural Rubber (ENR-50) or Polyethylene Acrylic Acid (PEA) as Compatibilizer on Properties of Ethylene Vinyl Acetate (EVA)/Natural Rubber (SMR L) Blends

The effect of epoxidized natural rubber (ENR) or polyethylene acrylic acid (PEA) as a compatibilizer on properties of ethylene vinyl acetate (EVA)/natural rubber (SMR L) blends was studied. 5 wt.% of compatibilizer was employed in EVA/SMR L blend and the effect of compatibilizer on tensile properties, thermal properties, swelling resistance, and morphological properties were investigated. Blends were prepared by using a laboratory scale of internal mixer at 120°C with 50 rpm of rotor speed. Tensile properties, thermal properties, thermo-oxidative aging resistance, and oil swell resistance were determined according to related ASTM standards. The compatibility of EVA/SMR L blends with 5 wt.% of compatibilizer addition or without compatibilizing agent was compared. The EVA/SMR L blend with compatibilizer shows substantially improvement in tensile properties compared to the EVA/SMR L blend without compatibilizer. Compatibilization had reduced interfacial tension and domain size of ethylene vinyl acetate (EVA)/natural rubber (SMR L) blends.     

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

Poly(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     

Dynamic mechanical behavior of high‐density polyethylene/ethylene vinyl acetate copolymer blends: The effects of the blend ratio,reactive compatibilization,and dynamic vulcanization

The effects of the blend ratio, reactive compatibilization, and dynamic vulcanization on the dynamic mechanical properties of high‐density polyethylene (HDPE)/ethylene vinyl acetate (EVA) blends have been analyzed at different temperatures. The storage modulus of the blend decreases with an increase in the EVA content. The loss factor curve shows two peaks, corresponding to the transitions of HDPE and EVA, indicating the incompatibility of the blend system. Attempts have been made to correlate the observed viscoelastic properties of the blends with the blend morphology. Various composite models have been used to predict the dynamic mechanical data. The experimental values are close to those of the Halpin–Tsai model above 50 wt % EVA and close to those of the Coran model up to 50 wt % EVA in the blend. For the Takayanagi model, the theoretical value is in good agreement with the experimental value for a 70/30 HDPE/EVA blend. The area under the loss modulus/temperature curve (LA) has been analyzed with the integration method from the experimental curve and has been compared with that obtained from group contribution analysis. The LA values calculated with group contribution analysis are lower than those calculated with the integration method. The addition of a maleic‐modified polyethylene compatibilizer increases the storage modulus, loss modulus, and loss factor values of the system, and this is due to the finer dispersion of the EVA domains in the HDPE matrix upon compatibilization. For 70/30 and 50/50 blends, the addition of a maleic‐modified polyethylene compatibilizer shifts the relaxation temperature of both HDPE and EVA to a lower temperature, and this indicates increased interdiffusion of the two phases at the interface upon compatibilization. However, for a 30/70 HDPE/EVA blend, the addition of a compatibilizer does not change the relaxation temperature, and this may be due to the cocontinuous morphology of the blends. The dynamic vulcanization of the EVA phase with dicumyl peroxide results in an increase in both the storage and loss moduli of the blends. A significant increase in the relaxation temperature of EVA and a broadening of the relaxation peaks occur during dynamic vulcanization, and this indicates the increased interaction between the two phases. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2083–2099, 2003     

Use of zinc‐neutralized ethylene/methacrylic acid copolymer ionomers as blend compatibilizers for nylon 6 and low‐density polyethylene

The effect of the composition on the morphologies and properties of uncompatibilized and compatibilized blends of nylon 6 and low‐density polyethylene were studied over a wide range of weight fractions. The uncompatibilized blends had substantially reduced mechanical properties after mixing, and this was almost certainly due to poor interfacial adhesion between the two polymers. The addition of a zinc‐neutralized poly(ethylene‐co‐methacrylic acid) ionomer (Surlyn® 9020) as a compatibilizer improved the mechanical properties in comparison with those of the material blended without the compatibilizer. The clearest evidence of this improvement came from dynamic mechanical studies; for selected blends with high polyethylene contents, the drop in the modulus corresponding to the transition of a solid to a melt occurred at higher temperatures with the added compatibilizer. This improvement in the properties was accompanied by a reduction in the dispersed‐phase size due to the interaction between the ionic part of the ionomer and the amide groups of nylon 6, especially when nylon 6 was the dispersed phase of the blend. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 620–629, 2003     

Correlation between the morphology and dynamic mechanical properties of ethylene vinyl acetate/linear low‐density polyethylene blends: Effects of the blend ratio and compatibilization

The effects of the blend composition and compatibilization on the morphology of linear low‐density polyethylene (LLDPE)/ethylene vinyl acetate (EVA) blends were studied. The blends showed dispersed/matrix and cocontinuous phase morphologies that depended on the composition. The blends had a cocontinuous morphology at an EVA concentration of 40–60%. The addition of the compatibilizer first decreased the domain size of the dispersed phase, which then leveled off. Two types of compatibilizers were added to the polymer/polymer interface: linear low‐density polyethylene‐g‐maleic anhydride and LLDPE‐g phenolic resin. Noolandi's theory was in agreement with the experimental data. The conformation of the compatibilizer at the blend interface could be predicted by the calculation of the area occupied by the compatibilizer molecule at the interface. The effects of the blend ratio and compatibilization on the dynamic mechanical properties of the blends were analyzed from ?60°C to +35°C. The experiments were performed over a series of frequencies. The area under the curve of the loss modulus versus the temperature was higher than the values obtained by group contribution analysis. The loss tangent curve showed a peak corresponding to the glass transition of EVA, indicating the incompatibility of the blend system. The damping characteristics of the blends increased with increasing EVA content because of the decrease in the crystalline volume of the system. Attempts were made to correlate the observed viscoelastic properties of the blends with the morphology. Various composite models were used to model the dynamic mechanical data. Compatibilization increased the storage modulus of the system because of the fine dispersion of EVA domains in the LLDPE matrix, which provided increased interfacial interaction. Better compatibilization was effected at a 0.5–1% loading of the compatibilizer. This was in full agreement with the dynamic mechanical spectroscopy data. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4526–4538, 2006     

Use of poly(ethylene‐co‐vinyl alcohol) as compatibilizer in LDPE/thermoplastic tapioca starch blends

Poly(ethylene‐co‐vinyl alcohol) (EVOH) was used as a compatibilizer to make blends of low‐density polyethylene (LDPE) and plasticized starch (TS). The tensile properties and impact strength were measured and compared with those of neat LDPE. The morphology of the blend specimens, both fractured and unfractured, was observed by scanning electron microscopy. Comparison of the properties showed that the impact strength of the blend improves significantly by the addition of a compatibilizer even with a high TS loading of 40 and 50% (by weight). A high elongation at break almost matching that of neat polyethylene was also obtained. The blend morphology of the etched specimens revealed fine dispersion of the starch in the polyethylene matrix, while the fracture surface morphology clearly indicate that the failure of compatibilized blends occurs mainly by the ductile mode. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3126–3134, 2002     

Comparison of olefin copolymers as compatibilizers for polypropylene and high‐density polyethylene

Some polyolefin elastomers were compared as compatibilizers for blends of polypropylene (PP) with 30 wt % high‐density polyethylene (HDPE). The compatibilizers included a multiblock ethylene–octene copolymer (OBC), two statistical ethylene–octene copolymers (EO), two propylene–ethylene copolymers (P/E), and a styrenic block copolymer (SBC). Examination of the blend morphology by AFM showed that the compatibilizer was preferentially located at the interface between the PP matrix and the dispersed HDPE particles. The brittle‐to‐ductile (BD) transition was determined from the temperature dependence of the blend toughness, which was taken as the area under the stress–strain curve. All the compatibilized blends had lower BD temperature than PP. However, the blend compatibilized with OBC had the best combination of low BD temperature and high toughness. Examination of the deformed blends by scanning electron microscopy revealed that in the best blends, the compatibilizer provided sufficient interfacial adhesion so that the HDPE domains were able to yield and draw along with the PP matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

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.     

Morphology and properties of nylon 6 and high density polyethylene blends in presence of nanoclay and PE‐g‐MA

In this study, we report the synergistic effect of nanoclay and maleic anhydride grafted polyethylene (PE‐g‐MA) on the morphology and properties of (80/20 w/w) nylon 6/high density polyethylene (HDPE) blend. Polymer blend nanocomposites containing nanoclay with and without compatibilizer (PE‐g‐MA) were prepared by melt mixing, and their morphologies and structures were examined with scanning electron microscopy (SEM) and wide angle X‐ray diffractometer (WAXD) study. The size of phase‐separated domains decreased considerably with increasing content of nanoclay and PE‐g‐MA. WAXD study and transmission electron microscopy (TEM) revealed the presence of exfoliated clay platelets in nylon 6 matrix, as well as, at the interface of the (80/20 w/w) nylon 6/HDPE blend–clay nanocomposites. Addition of PE‐g‐MA in the blend–clay nanocomposites enhanced the exfoliation of clays in nylon 6 matrix and especially at the interface. Thus, exfoliated clay platelets in nylon 6 matrix effectively restricted the coalescence of dispersed HDPE domains while PE‐g‐MA improved the adhesion between the phases at the interface. The use of compatibilizer and nanoclay in polymer blends may lead to a high performance material which combines the advantages of compatibilized polymer blends and the merits of polymer nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Thermoplastic elastomers based on epoxidized natural rubber and high‐density polyethylene blends: Effect of blend compatibilizers on the mechanical and morphological properties

Epoxidized natural rubber (ENR) with a level of epoxide groups of 20 mol % was prepared via the performic epoxidation method. It was then used to blend with high‐density polyethylene (HDPE) at various blend ratios. Three types of blend compatibilizers were prepared. These included a graft copolymer of HDPE and maleic anhydride (MA; i.e., HDPE‐g‐MA) and two types of phenolic modified HDPEs using phenolic resins SP‐1045 and HRJ‐10518 (i.e., PhSP‐PE and PhHRJ‐PE), respectively. We found that the blend with compatibilizer exhibited superior tensile strength, hardness, and set properties to that of the blend without compatibilizer. The ENR and HDPE interaction via the link of compatibilizer molecules was the polar functional groups of the compatibilizer with the oxirane groups in the ENR molecules. Also, another end of the compatibilizer molecules (i.e., HDPE segments) was compatibilizing with the HDPE molecules in the blend components. The blend with compatibilizer also showed smaller phase morphology than the blend without compatibilizer. Among the three types of the blend compatibilizer, HDPE‐g‐MA provided the blend with the greatest strength and hardness properties but the lowest set properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008