Reactive compatibilization of an immiscible polyester/polyolefin blend with PP‐g‐MAH and PMPI dual compatibilizers

Blends of a polyester hot melt resin and a poly‐α‐olefin hot melt resin were modified using the reactive compounding technique. The effects of the compatibilizers were evaluated by studying the mechanical properties, the morphology, and the thermal properties of the modified blends. A pronounced compatibilizing effect was obtained with dual compatibilizers composed of maleated polypropylene and poly[methylene (phenylene isocyanate)] (PMPI). The addition of 1 phr of PMPI was sufficient to improve the elongation and tensile strength. From the results, it is anticipated that PMPI can be used as an efficient coupler to enhance the compatibility of immiscible polyester/polyolefin blends. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40232.     

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     

Irradiation processing of immiscible PP/EOC blend: Morphology control and processability modification

In this study, applying electron beam irradiation method at a relatively low-irradiation dose (20 kGy) under the air atmosphere to prepare injectable polypropylene (PP)/ethylene-octene copolymer (EOC) blends with fine morphology and appropriate performance was investigated. For this purpose, an extrusion PP grade with an EOC grade suitable to improve its impact resistance was melting blended. Gel content and rheological measurements revealed long-chain branching is predominant phenomenon occurring during the irradiation process of EOC. Blend irradiation resulted in changing its melt flow index proper for injection molding. A fine morphology obtained for the unirradiated blend was preserved for the irradiated blend. Moreover, irradiation thermally stabilized the blend morphology. Blends linear viscoelastic behavior discussed by proper rheological models revealed the existence of interfacial interactions and a reduction of the interfacial tension between irradiated blend phases. No significant effect of irradiation on the crystallization characteristics of EOC and the blend was observed. The satisfying impact resistance of the irradiated blend was near to that of the unirradiated blend, although its tensile mechanical properties were less.     

Super toughened and highly ductile PLA/TPU blend systems by in situ reactive interfacial compatibilization using multifunctional epoxy-based chain extender

This study investigates the influence of using multifunctional epoxy Joncryl ADR 4468 chain extender (CE) on the properties of various polylactide (PLA)/thermoplastic polyurethane (TPU) (75 wt/25 wt) blend systems. The blends were based on two different TPU grades with ether- and ester-based soft segment as the dispersed phase (i.e., TPUether and TPUester) and an amorphous and a semicrystalline PLA grades as the matrix (i.e., aPLA and scPLA). PLA appeared to be more compatible with the TPUester, which caused the enhancement of the impact strength and strain at break values of the blends more remarkably. The dynamic rheological experiments also confirmed that the CE revealed a better reactivity with TPUester than TPUether. This further enhanced the interfacial compatibility between the PLA and TPUester and thereby dramatically improved the impact strength and ductility of the PLA/TPUester blends, specifically those with 0.5 wt% CE. Meanwhile, aPLA as the matrix reflected the TPUs toughening effect more efficiently than scPLA. This was due to the possible shrinkage caused by the crystallization of scPLA matrix, which could deteriorate the interfacial interactions between the phases in the corresponding blends.     

Highly-modified polylactide transparent blends with better heat-resistance,melt strength,toughness and stiffness balance due to the compatibilization and chain extender effects of methacrylate-co-glycidyl methacrylate copolymer

A core-shell modifier with the cross-linked acrylate and silicone copolymer as the core and polymethyl methacrylate (PMMA) as the shell (PASi-g-PMMA) was used to toughen the brittle polylactide (PLA). In addition, the copolymer of methyl methacrylate (MMA) and glycidyl methacrylate (GMA) (MG) was utilized to further enhance the modification efficiency of the PASi-g-PMMA. The MG copolymer played the double roles of compatibilizer and chain extender, which not only improved the interfacial adhesion between the PLA and PASi-g-PMMA particles, but also increased the molecular weight and chain entanglement of the PLA. Compared with the PASi-g-PMMA toughened PLA blend, the PLA/PASi-g-PMMA/MG blends showed much higher heat-resistance, melt strength, transparency, toughness and stiffness balance. When the PASi-g-PMMA content was 20 wt%, 20 wt% MG increased the glass transition temperature (T_g), complex viscosity (η*), transparency, impact and tensile strength of PLA/PASi-g-PMMA blend from 60.1°C, 1.9 × 10³ Pa·s, 76.1%, 748 J/m and 37 MPa to 71.5°C, 0.5 × 10⁴ Pa·s, 78.4%, 860 J/m and 45 MPa for the PLA/PASi-g-PMMA/MG blend. This research provided a facile and practical method to overcome the shortcomings of the PLA and promoted its application in broader fields.     

Compatibilization of Polyamide‐6/Polyarylate Blends by Means of an Ionomer

Summary: Polyamide‐6 (PA6)/polyarylate of bisphenol A (PAr) blends rich in PA6 and modified with an additional 15% poly[ethylene‐co‐(methacrylic acid)] partially neutralized with zinc (PEMA‐Zn) as a compatibilizer were obtained by melt mixing. Their phase structure, morphology, and mechanical performance were compared with those of the corresponding binary blends. The ternary blends were composed of a PA6 amorphous matrix and a dispersed PAr‐rich phase in which reacted PA6 and PEMA‐Zn were present. Additionally, minor amounts of a crystalline PA6 phase, and a PEMA‐Zn phase were also present. The chemical reactions observed led to a clear decrease in the dispersed particle size when PEMA‐Zn was added, indicating compatibilization. Consequently, the mechanical behavior of the blends with PEMA‐Zn improved, leading, mainly in the case of the blend with 10% PAr, to significant increases in both ductility and impact strength with respect to those of the binary blends. These increases were more remarkable than the slight decrease in stiffness as a consequence of the rubbery nature of the compatibilizer.

Cryogenically fractured surface of the PA6/PAr‐PEMA‐Zn 70/30‐15 ternary blend.     

Optimization of the thermal mending process in epoxy/cyclic olefin copolymer blends

Cyclic olefin copolymer (COC) is utilized as thermoplastic healing agent in an epoxy resin and the effect of mending temperature on the healing of resulting materials is investigated. Blends are prepared by adding 20 and 30 wt% COC powder in the epoxy resin. They are thermo-mechanically characterized and fractured samples are thermally mended at various temperatures to evaluate the healing efficiency of the repaired samples. Optical microscopy reveals a homogenous dispersion of COC domains within epoxy matrix, while thermogravimetric analysis shows improved thermal stability of the samples. The immiscibility of the two phases in the blends lead to a decrease of the mechanical properties under flexural and tensile loading modes with respect to neat epoxy. The fracture toughness increases upon COC addition at elevated amounts. Healing efficiency values up to more than 80% are obtained at the lowest investigated temperature of 145°C for samples with 30 wt% of COC.     

Novel reactive compatibilization strategy on immiscible polypropylene and polystyrene blend

Polypropylene (PP) and polystyrene (PS) are immiscible and incompatible. Since both PP and PS components possess no reactive functional group, reactive compatibilization of a PP/PS blend is impossible unless certain reactive functional groups are imparted to either PP or PS. In this study we provide a simple approach to reactively compatibilize the nonreactive PP/PS blend system by physically functionalizing PP and PS with the addition of maleic anhydride grafted PP (PP‐g‐MA) and styrene maleic anhydride random copolymer (SMA), respectively. An epoxy monomer, serving as a coupler and possessing four epoxy groups able to react with the maleic anhydride of PP‐g‐MA and SMA, was then added during melt blending. Observations of the finer PS domain sizes and improved mechanical properties support the plausibility of reactive compatibilization of this nonreactive PP/PS blend by combining physically functionalized PP and PS with tetra‐glycidyl ether of diphenyl diamino methane (TGDDM) in a one‐step extrusion process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

The effect of the addition of poly(styrene‐co‐glycidyl methacrylate) copolymer on the properties of polylactide/poly(methyl methacrylate) blend

The effect of the addition of poly(styrene‐co‐glycidyl methacrylate) P(S‐co‐GMA) copolymer on the properties of melt blended polylactide/poly(methyl methacrylate) (PLA/PMMA) 80/20 (wt %) composition was studied. In the literature high ductility levels were achieved by melt blending PLA with different additives. However, the gained ductility was counter balanced with drastic drops in strength and modulus values. The novelty of this work was the preparation of PLA‐based blends with polylactide content higher than 75 wt % which showed an impact resistance value improvement of about 60% compared with the neat PLA and maintained similar tensile strength and modulus values as well as glass transition temperature to neat PLA. The addition of only 3 pph of copolymer to PLA/PMMA blend improved the impact resistance almost 100%. The chemical reaction between PLA/PMMA blend and P(S‐co‐GMA) copolymer were analyzed by FTIR, rotational rheometry, and GPC/SEC. Phase structure and morphology were studied by Differential Scanning Calorimetry and Scanning Electronic Microscopy. Tensile and impact properties as well as thermal stability were also studied. Results showed that as the amount of copolymer in the blend was increased then higher was average molecular weight and polydispersity index. After the addition of P(S‐co‐GMA) copolymer to the PLA/PMMA blend the impact resistance, elongation at break and thermal stability were improved while tensile strength and elastic modulus remained almost unaltered. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43935.     

Compatibilization of polypropylene/polystyrene blends with poly(styrene-b-butadiene-b-styrene) block copolymer

The compatibilizing effect of the triblock copolymer poly(styrene-b-butadiene-b-styrene) (SBS) on the morphology and mechanical properties of immiscible polypropylene/polystyrene (PP/PS) blends were studied. Blends with three different weight ratios of PP and PS were prepared and three different concentrations of SBS were used for investigations of its compatibilizing effects. Scanning electron microscopy (SEM) showed that SBS reduced the diameter of the PS-dispersed particles as well as improved the adhesion between the matrix and the dispersed phase. Transmission electron microscopy (TEM) revealed that in the PP matrix dispersed particles were complex “honeycomblike” aggregates of PS particles enveloped and joined together with the SBS compatibilizer. Wide-angle X-ray diffraction (WAXD) analysis showed that the degree of crystallinity of PP/PS/SBS slightly exceeded the values given by the addition rule. At the same time, addition of SBS to pure PP and to PP/PS blends changed the orientation parameters A₁₁₀ and C significantly, indicating an obvious SBS influence on the crystallization process in the PP matrix. SBS interactions with PP and PS influenced the mechanical properties of the compatibilized PP/PS/SBS blends. Addition of SBS decreased the yield stress and the Young's modulus and improved the elongation at yield as well as the notched impact strength in comparison to the binary PP/PS blends. Some theoretical models for the determination of the Young's modulus of binary PP/PS blends were used for comparison with the experimental results. The experimental line was closest to the series model line. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 2625–2639, 1998     

A comparative experimental study of the hygroscopic and mechanical behaviors of electrospun nanofiber membranes and solution-cast films of polybenzimidazole

This article reports a comparative experimental study of the hygroscopic and mechanical behaviors of electrospun polybenzimidazole (PBI) nanofiber membranes and solution-cast PBI films. As-electrospun nonwoven PBI nanofiber mats (with the nanofiber diameter of ~250 nm) were heat-pressed under controlled temperature, pressure and duration for the study; lab-made solution-cast PBI films and commercially available PBI films (the PBI Performance Product Inc., Charlotte, NC) were used as the control samples. Thermogravimetric and microtensile tests were utilized to characterize the hygroscopic (moisture absorption) and mechanical properties of the PBI nanofiber membranes at varying heat-pressing conditions, which were further compared to those of solution-cast PBI films. Experimental results indicated that the PBI nanofiber membranes carried slightly higher thermal stability and less hygroscopic properties than those of solution-cast PBI films. In addition, heat-pressing conditions significantly influenced the mechanical properties of the resulting PBI nanofiber membranes. The stiffness and tensile strength increase with increasing either the heat-pressing pressure or duration, and relevant mechanisms were explored. The present study provides a rational understanding of the hygroscopic and mechanical behaviors of electrospun PBI nanofiber membranes and solution-cast PBI films that are beneficial to their reliable cutting-edge applications in high-temperature filtration, polymer electrolyte membranes (PEMs), etc.     

Lightweight polyethylene-hollow glass microspheres composites for rotational molding technology

Innovative composites based on polyethylene (PE) filled with hollow glass microspheres (HGMs) were formulated and successfully prepared as suitable plastic materials for rotational molding technology. The HGMs here used allow to attain lightweight materials with a reduced resin content and appealing aesthetical qualities. To enhance filler dispersion and phase adhesion, thus improving the ultimate properties of the composite materials, two compatibilization strategies were adopted: namely, surface modification of HGMs by dodecyl(triethoxy)silane or addition during mixing of a maleinized PE as in-situ coupling agent. The effectiveness of the surface treatments on HGMs was assessed by attenuated total reflectance Fourier-transform infrared spectroscopy and thermogravimetric analysis investigations. PE-based composites at various HGMs contents (5, 10, and 20 wt%) were prepared by melt blending. Morphology of untreated and modified HGMs, their dispersion in the composites as well as filler/matrix adhesion were investigated by SEM microscopy. Thermal, rheological and mechanical properties of the composites were studied in comparison with neat PE. Rotational molding tests carried out both in laboratory and industrial site demonstrated the feasibility of producing lightweight plastic items (weight reduction up to 17%) of excellent aesthetics on a large scale.     

Artificial weathering effect on the structure and properties of polypropylene/polyamide‐6 blends compatibilized with PP‐g‐MA

The degradation of uncompatibilized and compatibilized PP/PA‐6 (70/30 wt %) with PP‐g‐MA under accelerated UV light was investigated using Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy, melt flow index (MFI) tester, tensile test, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). FTIR analysis of the structure of the compatibilized and uncompatibilized blends after exposure to UV light showed the formation of photoproducts corresponding to both components. The MFI and mechanical results obtained revealed that photooxidation started primarily in PA‐6 rather than PP. In addition, the uncompatibilized blends exhibited a higher degradation rate compared to neat polymers for long exposure time, and the addition of PP‐g‐MA increased slightly their ageing rate in accordance with TGA data. Further, DSC analysis showed an increase in the crystallinity index and a decrease in the melting temperature of PP and PA‐6 after UV exposure either as neat polymers or as blend components. SEM micrographs of the cryo‐fractured surfaces of the samples illustrated the formation of cracks and fractures after UV irradiation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41722.     

Compatibilization of polypropylene/Poly(acrylonitrile‐butadiene‐styrene) blends by polypropylene‐graft‐cardanol

The polypropylene‐graft‐cardanol (PP‐g‐cardanol) was prepared by reactive extrusion with polypropylene (PP) and natural renewable cardanol which could increase the interfacial energy of PP and inhibit the degradation of PP during the process of reactive extrusion and usage. In this article, PP‐g‐cardanol and polypropylene‐graft‐maleic anhydride (PP‐g‐MAH) were used as compatibilizers of the polypropylene (PP)/poly(acrylonitrile‐butadiene‐styrene) (ABS) blends. PP/ABS (70/30, wt %) blends with PP‐g‐cardanol and PP‐g‐MAH were prepared by a corotating twin‐screw extruder. From the results of morphological studies, the droplet size of ABS was minimized to 1.93 and 2.01 μm when the content of PP‐g‐cardanol and PP‐g‐MAH up to 5 and 7 phr, respectively. The results of mechanical testing showed that the tensile strength, impact strength and flexural strength of PP/ABS (70/30) blends increase with the increasing of PP‐g‐cardanol content up to 5 phr. The complex viscosity of PP/ABS (70/30) blends with 5 phr PP‐g‐cardanol showed the highest value. Moreover, the change of impact strength and tensile strength of PP/ABS (70/30) blends were investigated by accelerated degradation testing. After 4 accelerated degradation cycles, the impact strength of the PP/ABS (70/30) blends with 5 phr PP‐g‐cardanol decrease less than 6%, but PP/ABS (70/30) blends with 5 phr PP‐g‐MAH and without compatibilizer decrease as much as 12% and 32%, respectively. The tensile strength of PP/ABS (70/30) blends has a similar tendency to that of impact strength. The above results indicated that PP‐g‐cardanol could be used as an impact modifier and a good compatibilizer, which also exhibited better stability performance during accelerated degradation testing. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41315.     

Compatibilization of a polyolefin blend through covalent and ionic coupling of grafted polypropylene and polyethylene. I. Rheological,thermal, and mechanical properties

A polypropylene/high‐density polyethylene blend containing 70 wt % polypropylene was prepared and compatibilized via the addition of maleic anhydride grafted polypropylene and polyethylene. The functionalized polymer chains were coupled with two types of coupling agents. Dodecane diamine formed covalent bonds with the maleic anhydride, whereas two metallic salts, zinc acetate and sodium hydrogenocarbonate, formed ionic interactions with the carboxylic functions produced by the hydration of the anhydride cycle. The coupling of the grafted polyolefin chains was successfully realized by a single operation in a twin‐screw extruder. The coupling agents were efficient in improving the elongation at break and impact properties of the studied blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 312–320, 2005     

Compatibilization of a poly(butylene terephthalate)/poly(ethylene octene) copolymer blends with different amounts of an epoxy resin

New toughened poly(butylene terephthalate) (PBT) materials were obtained by melt blending with 20 wt % poly(ethylene octene) (PEO) copolymer and different levels of a difunctional epoxy resin in a twin‐screw extruder followed by injection‐molding. The presence of neither PEO or epoxy influenced either the phase nature of the two amorphous phases of the blends or the crystallization process of PBT, despite the slight reaction of epoxy with PBT as stated by the observed torque increases. The addition of epoxy led to a decrease in the particle size that stopped due to the concomitant viscosity increase. Supertough PBT‐based blends with an impact strength more than 18‐fold that of PBT were obtained without previous chemical modification of any of the blend components at 1.0 wt % epoxy contents. The interparticle distance was the parameter that controlled notched toughness in these PBT/PEO blends. The adhesion at the interphase was the parameter on which the critical interparticle distance appeared to depend. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 260–269, 2004     

Compatibilization of regenerated low density polyethylene/poly(vinyl chloride) blends

The aim of this work is to study the valorization of regenerated low density polyethylene (rLDPE) by blending with PVC in the presence of chlorinated polyethylene (CPE) as compatibilizer. For this purpose, four rLDPE samples coming from neat or dirty wastes were used. They were obtained after milling, washing, and extrusion in a conventional recycling plant. They were first characterized in terms of physicochemical (density, melt flow index, water absorption, and level of oxidation by Fourier transform infrared spectroscopy) and mechanical (tensile and shore D hardness) properties. The effect of the ratio of PVC on these physical and mechanical properties was then investigated. These binary blends exhibited lower properties than those of the separated polymers. The addition of CPE to the binary blend with weight proportion of 50/50 leads to a substantial improvement of the considered properties which is due to a better interfacial adhesion between rLDPE and PVC as evidenced by the analysis of the morphology of the blends by scanning electron microscopy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Enhanced mechanical and anisotropic thermal conductive properties of polyimide nanocomposite films reinforced with hexagonal boron nitride nanosheets

To attain thermally conductive but electrically insulating polymer films, in this study, polyimide (PI) nanocomposite films with 1–30 wt% functionalized hexagonal boron nitride nanosheets (BNNSs) were fabricated via solution casting and following imidization. The microstructures, mechanical and thermal conductive properties of PI/BNNS nanocomposite films were examined by taking account of the relative content, anisotropic orientation, and interfacial interaction of BNNS and PI matrix. The scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffractometry data revealed that BNNSs with hydroxy and amino functional groups have specific molecular interactions with PI matrix and they form stacked aggregates in the nanocomposite films with high BNNS loadings of 10–30 wt%. The tensile mechanical strength/modulus, thermal degradation temperatures, and thermal conductivity of the nanocomposite films were found to be significantly enhanced with increasing the BNNS loadings. For the nanocomposite films with 1–30 wt% BNNS loadings, the in-plane thermal conductivity was measured to be 1.82–2.38 W/mK, which were much higher than the out-of-plane values of 0.35–1.14 W/mK. The significant anisotropic thermal conductivity of the nanocomposite films was found to be owing to the synergistic anisotropic orientation effects of both BNNS and PI matrix. It is noticeable that the in-plane and out-of-plane thermal conductivity values of the nanocomposite film with 30 wt% BNNS were ~1.31 and ~3.35 times higher than those of neat PI film, respectively.     

Melt rheology and mechanical crystal transformation in an immiscible blend with poly(vinylidene fluoride) matrix

Effect of immiscible polyamide 6 (PA6) on the melt rheology and stretch‐induced crystal transformation of poly (vinylidene fluoride) (PVDF) matrix is reported. PA6 is dispersed as submicron droplets in the PVDF matrix, responsible for significant enhancement in the melt elasticity. Nevertheless, crystallization habits of PVDF matrix from melt are little affected by submicron PA6 droplets, and the α‐form of PVDF prevails in the blends. Upon mechanical stretching, the α‐form is converted to the β‐form, which is remarkably reduced with the increasing of PA6 content in the blends. It could be correlated with the decreased tensile stress in the presence of submicron PA6 droplets that act as stress concentrators. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43499.     

Formation of branched polyethylenes by ethylene homopolymerization using LNiBr2 homo- and heterogeneous precatalysts: Interpretation of the polymer structures in comparison with commercial LLDPE

Comparative data on the micro-structures and properties of branched polyethylenes (BPE) produced via ethylene homopolymerization over homogeneous N,N-α-diimine LNiBr₂ complexes with different ligand composition (AlEt₂Cl as a cocatalyst) and corresponding supported catalysts LNiBr₂/SiO₂(Al) (Al[iso-Bu]₃ as a cocatalyst) are presented. Noticeable differences were observed between micro-structures of BPEs obtained using homo- and heterogeneous LNiBr₂ complexes as catalysts. Supported catalysts produce BPEs with the majority of methyl branches (17–18 CH₃(1000 C)⁻¹ characterized by different molecular masses (1800–210 kg mol⁻¹) and molecular weight distributions (M_w[M_n]⁻¹ = 5.9 and 2.6). Thermal and mechanical properties of these BPE samples obtained over supported Ni catalysts are similar to those of commercial LLDPE samples prepared with metallocene and Ziegler-Natta catalysts.