On Toughness and Stiffness of Poly(butylene terephthalate) with Epoxide‐Containing Elastomer by Reactive Extrusion

Summary: To obtain a balance between toughness (as measured by notched impact strength) and elastic stiffness of poly(butylene terephthalate) (PBT), a small amount of tetra‐functional epoxy monomer was incorporated into PBT/[ethylene/methyl acrylate/glycidyl methacrylate terpolymer (E‐MA‐GMA)] blends during the reactive extrusion process. The effectiveness of toughening by E‐MA‐GMA and the effect of the epoxy monomer were investigated. It was found that E‐MA‐GMA was finely dispersed in PBT matrix, whose toughness was significantly enhanced, but the stiffness decreased linearly, with increasing E‐MA‐GMA content. Addition of 0.2 phr epoxy monomer was noted to further improve the dispersion of E‐MA‐GMA particles by increasing the viscosity of the PBT matrix. While use of epoxy monomer had little influence on the notched impact strength of the blends, there was a distinct increase in the elastic stiffness. SEM micrographs of impact‐fracture surfaces indicated that extensive matrix shear yielding was the main impact energy dissipation mechanism in both types of blends, with or without epoxy monomer, and containing 20 wt.‐% or more elastomer.

SEM micrographs of freeze‐fractured surfaces of PBT/E‐MA‐GMA blend illustrating the finer dispersion of E‐MA‐GMA in the presence of epoxy monomer.     

Blends of poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polyamide 6 toughened by maleated polystyrene‐based copolymers: Mechanical properties,morphology, and rheology

Poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polyamide 6 (PPO/PA6 30/70) blends were impact modified by addition of three kinds of maleated polystyrene‐based copolymers, i.e., maleated styrene‐ethylene‐butylene‐styrene copolymer (SEBS‐g‐MA), maleated methyl methacrylate‐butadiene‐styrene copolymer (MBS‐g‐MA), and maleated acrylonitrile‐butadiene‐styrene copolymer (ABS‐g‐MA). The mechanical properties, morphology and rheological behavior of the impact modified PPO/PA6 blends were investigated. The selective location of the maleated copolymers in one phase or at interface accounted for the different toughening effects of the maleated copolymer, which is closely related to their molecular structure and composition. SEBS‐g‐MA was uniformly dispersed in PPO phase and greatly toughened PPO/PA6 blends even at low temperature. MBS‐g‐MA particles were mainly dispersed in the PA6 phase and around the PPO phase, resulting in a significant enhancement of the notched Izod impact strength of PPO/PA6 blends from 45 J/m to 281 J/m at the MBS‐g‐MA content of 20 phr. In comparison, the ABS‐g‐MA was mainly dispersed in PA6 phase without much influencing the original mechanical properties of the PPO/PA6 blend. The different molecule structure and selective location of the maleated copolymers in the blends were reflected by the change of rheological behavior as well. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Relationship between structure and properties in high‐performance PA6/SEBS‐g‐MA/(PPO/PS) blends: The role of PPO and PS

This work aimed at studying the role of poly(phenylene oxide) (PPO) and polystyrene (PS) in toughening polyamide‐6 (PA6)/styrene‐ethylene‐butadiene‐styrene block copolymer grafted with maleic anhydride (SEBS‐g‐MA) blends. The effects of weight ratio and content of PPO/PS on the morphology and mechanical behaviors of PA6/SEBS‐g‐MA/(PPO/PS) blends were studied by scanning electron microscope and mechanical tests. Driving by the interfacial tension and the spreading coefficient, the “core–shell” particles formed by PPO/PS (core) and SEBS‐g‐MA (shell) played the key role in toughening the PA6 blends. As PS improved the distribution of the “core–shell” particles due to its low viscosity, and PPO guaranteed the entanglement density of the PPO/PS phase, the 3/1 weight ratio of PPO/PS supplied the blends optimal mechanical properties. Within certain range, the increased content of PPO/PS could supply more efficient toughening particles and bring better mechanical properties. Thus, by adjusting the weight ratio and content of PPO and PS, the PA6/SEBS‐g‐MA/(PPO/PS) blends with excellent impact strength, high tensile strength, and good heat deflection temperature were obtained. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45281.     

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.     

Toughening and compatibilization of polyphenylene sulfide/nylon 66 blends with SEBS and maleic anhydride grafted SEBS triblock copolymers

In this study, styrene‐b‐ethylene/butylene‐b‐styrene triblock copolymer (SEBS) and maleic anhydride grafted SEBS (SEBS‐g‐MA) were used as compatibilizers for the blends of polyphenylene sulfide/nylon 66 (PPS/PA66). The mechanical properties, including impact and tensile properties and morphology of the blends, were investigated by mechanical properties measurements and scanning electron microscopy. Impact measurements indicated that the impact strength of the blends increases slowly with elastomer (SEBS and SEBS‐g‐MA) content upto 20 wt %; thereafter, it increases sharply with increasing elastomer content. The impact energy of the elastomer‐compatibilized PPS/PA66 blends exceeded that of pure nylon 66, implying that the nylon 66 can be further toughened by the incorporation of brittle PPS minor phase in the presence of SEBS or SEBS‐g‐MA. The compatibilization efficiency of SEBS‐g‐MA for nylon‐rich PPS/PA66 was found to be higher than SEBS due to the in situ forming SEBS interphase between PPS and nylon 66. The correlation between the impact property and morphology of the SEBS‐g‐MA compatibilized PPS/PA66 blends is discussed. The excellent impact strength of the nylon‐rich blends resulted from shield yielding of the matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Polyolefin/Lignosulfonate Blends, 9

Summary: In the present study, the compatibility, properties and degradability of polyolefin/lignin blends have been studied. Blends of three maleic anhydride grafted copolymers of ethylene‐propylene rubbers containing various content of functional groups with epoxy‐modified lignosulfonate have been investigated by microscopy, X‐ray diffraction, surface and mechanical indices determination, electron spin resonance, IR spectroscopy, differential scanning calorimetry and thermogravimetry. To assess the environmental degradation characteristics, the behavior of the blends during soil burial test has been investigated. The influence of the buried polymer blends on the physiological vegetative processes of the Vicia X Hybrida hort plant has been monitored.

Optical microscopy images of blend EP‐g‐MA 0.3/5 LER, undegraded (left) and degraded (right).     

Study of the Fire Performance of Magnesium Hydroxide Sulfate Hydrate Whisker Flame Retardant Polyethylene

Summary: Halogen‐free, flame retardant low density polyethylene (LDPE) composites, using magnesium hydroxide sulfate hydrate (MHSH) whiskers as a flame retardant, combined with microencapsulated red phosphorous (MRP) as a synergist, have been prepared using a two‐roll mill. Their fire properties were determined by using the limiting oxygen index (LOI), the UL‐94 test and cone calorimetry. The results showed that MRP was a good synergist in improving the flame retardance of the LDPE/MHSH whisker system. Poly[ethylene‐co‐(vinyl acetate)] (EVA), used as a compatibilizer, increased the fire performance of LDPE/MHSH whisker composites.

HRR curves for LDPE/MHSH whisker composites.     

Preparation of New Bioactive Hybrid Bone Cements Containing Bis‐GMA Derivatives as a Prepolymer

Summary: Novel organic‐inorganic hybrid bioactive bone cements containing bisphenol‐A‐glycidyl methacrylate (Bis‐GMA) derivatives and a bioactive inorganic filler were prepared for orthopedic applications. The Bis‐GMA derivatives, such as 3MA and a 3MA mixture (3MA mix), were synthesized by blocking one or two of the hydroxyl groups of the Bis‐GMA so as to use it as a prepolymer. Four organic prepolymers, such as Bis‐GMA, 3MA, 3MA 50 and 3MA mix, and an inorganic filler, AW‐GC, were used for the preparation of the bioactive bone cements and their characteristics were evaluated. As compared with the Bis‐GMA control, the new bioactive bone cements containing the Bis‐GMA derivatives exhibited appropriate curing times, low polymerization shrinkage, low water absorption and solubility as well as high mechanical properties. In particular, the bioactive bone cement containing 3MA mix and AW‐GC had higher bending and compressive strengths than the Bis‐GMA one.

Curing time and polymerization shrinkage on various prepolymers of bioactive bone cements.     

Molecular and Morphological Characterization of Immiscible SAN/EPDM Blends Filled by Nano Filler

The compatibilizing effect of nano sized calcium carbonate filler on immiscible blends of styrene‐co‐acrylonitrile/ethylene propylene diene (SAN/EPDM) was examined. The surface energy of the calcium carbonate was modified by stearic acid. The compatibility of SAN/EPDM blends was studied by following the glass transition temperature T_g by DSC. SEM was used to observe the blend morphology and the X‐ray analyzer was used to detect the calcium from filler in samples. Mechanical properties of the blends were determined, and related to changes of polymer‐filler interactions and morphology. The results suggest that the morphology of the SAN/EPDM blends studied was affected by the reduction of surface energy of the filler.

SEM micrograph of an SAN/EPDM blend with 5% of maximally treated filler.     

Reactive Compatibilization of Polyamide 6 with Isocyanate Functionalized Ethylene‐Propylene Copolymer

Reactive compatibilization of ethylene‐propylene copolymer functionalized with allyl (3‐isocyanato‐4‐tolyl) carbamate (TAI) isocyanate (EPM‐g‐TAI) and polyamide 6 (PA6) was investigated in this paper. FTIR analysis revealed the evidence of a chemical reaction between the end groups of PA6 and EPM‐g‐TAI. Thermal, rheological, morphological, and mechanical properties of the resultant system were examined. DSC analysis indicated that the crystallization of PA6 in PA6/EPM‐g‐TAI blends was inhibited, due to the chemical reaction that occurs at the interface of PA6 and EPM‐g‐TAI. Rheological measurement showed that complex viscosity and storage modulus of PA6/EPM‐g‐TAI were both dramatically enhanced compared to those of PA6/EPM at the same blending composition. After examining the morphology of both blending systems, smaller particle size, more homogeneous distribution of domains and improved interfacial adhesion between matrix and domains were observed in the compatibilized system. Mechanical properties such as tensile strength, Young's modulus, flexural strength and modulus, as well as notched and un‐notched impact strength of PA6/EPM‐g‐TAI blends were also found to improve gradually with increasing the content of grafted TAI.

Tensile modulus of the blends versus rubber content.     

Use of Functionalized Metallocene Copolymers from Ethylene and Polar Olefins as Compatibilizers for Low‐Density‐Polyethylene/Starch and Low‐Density‐Polyethylene/Dextran Blends

Summary: Functionalized metallocene copolymers synthesized from ethylene with 5‐hexen‐1‐ol and ethylene with 10‐undecen‐1‐ol were used as compatibilizers in LDPE/starch and LDPE/dextran blends in order to improve the interfacial adhesion between hydrophobic LDPE and hydrophilic natural polymers. An increase in tensile modulus and a slight decrease in tensile strength was observed when poly[ethylene‐co‐(10‐undecen‐1‐ol)] was added to a 70:30 wt.‐% LDPE/dextran blend, whereas the addition of poly[ethylene‐co‐(5‐hexen‐1‐ol)] as compatibilizer resulted in obtaining a more rigid material with a slightly higher modulus. Scanning electron microscopy of modified dextran blends containing 3 wt.‐% of both compatibilizers showed some degree of phase cocontinuity. Enhanced interfacial adhesion and decrease in particle size of starch was observed when 5 wt.‐% of poly [ethylene‐co‐(5‐hexen‐1‐ol)] copolymer was used as the compatibilizer in starch blends. The crystallization temperature of LDPE, determined by DSC, was shifted to a slightly higher temperature as a consequence of the addition of the compatibilizers. The existence of phase segregation was also revealed by thermal analysis when 5 wt.‐% of the copolymers were used as blend modifiers.

SEM micrograph of 70:30 wt.‐% LDPE/dextran blend with added poly[ethylene‐co‐(5‐hexen‐1‐ol)] compatibilizer.     

The Effect of Phase Structure on the Tribological Properties of PA66/HDPE Blends

Summary: In this paper, immiscible, partially miscible and miscible blends of polyamide 66 (PA66) and high density polyethylene (HDPE) were obtained by changing compatibilizer concentrations. Mechanical and tribological properties of materials were tested. It was found that the addition of compatibilizer greatly improved the mechanical properties of PA66/HDPE blends. The wear of PA66/HDPE blends was strongly affected by the phase structure. The best blend for lower friction coefficient and higher wear resistance was the blend with a miscible structure, which significantly improved the tribological properties of PA66 and HDPE. SEM investigations on the worn surface and the steel counterface indicated that, for the immiscible and partially miscible blend systems, the dispersed HDPE particles were pulled out from the worn surfaces during sliding because of the poor adhesion between HDPE and PA66, while this was not observed in the miscible blend system.

SEM micrograph of the worn surface formed by PA66/HDPE blend without HDPE‐g‐MAH.     

On Blends of Polyamide 6 and a Hyperbranched Aramid

The hyperbranched (HB) aromatic polyamide synthesised by direct polycondensation of 5‐(4‐aminobenzoylamino)isophthalic acid (ABZAIA) has been solution‐ and melt‐ blended with polyamide 6 (PA6) incorporating different end groups. The concentration of p(ABZAIA) in PA6 has been varied from 5 to 30 wt.‐% in order to evaluate the influence of hyperbranched polymer content on blend properties. Viscosity and glass transition (T_g) data of the solution blends underlined the full miscibility between the components in the explored composition range. The miscibility was not related to any specific type of PA6 end group, thus suggesting a major role for its amide groups in interacting (presumably via hydrogen bonding) with HB functional end groups. Well‐separated powder particles have been obtained by precipitation from diluted solutions both for the neat polymers and for the blends. Also, in the case of blends prepared by melt mixing T_g linearly increased with the HB polymer content, again confirming full miscibility between the blend components. Blend characterisation, solubility tests and melt rheology supported the idea that p(ABZAIA) forms reactive blends with polyamide 6 by melt mixing. As a consequence of these reactions, the hyperbranched aramid strongly modified the rheological behaviour of PA6.

Formation of well dispersed spherical and homogeneous particles after precipitation of a PA6 dilute solution.     

Thermal Characterization of Upper Critical Solution Temperature m‐LLDPE/Poly(ethylene‐ran‐butene) Elastomer Blends

Summary: The phase and thermal characteristics of blends consisting of linear low‐density polyethylene (LLDPE) (0.7 mol‐% hexene copolymer) and poly(ethylene‐ran‐butene) (PEB) (26 mol‐% butene copolymer) have been investigated using optical microscopy (OM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). An upper critical solution temperature of 162 °C was exhibited. The addition of PEB not only slowed the overall crystallization rate of LLDPE but also changed the distribution of lamellar thickness or perfection of LLDPE crystals. The equilibrium melting temperature of LLDPE in the blends was reduced and kept relatively constant in the bi‐phase state. The blends showed a single‐stage degradation and an intermediate thermal stability between those of the individual components. It could be attributed to their homogeneous states at degradation temperatures and the similar decomposing mechanisms of two components. The kinetic analysis of thermal degradation also confirmed the above results.

Phase diagram of LLDPE/PEB blends.     

CO2‐Induced Mechanical Reinforcement of Polyolefin‐Based Nanocellular Foams

The effect of CO₂‐induced crystallization on the mechanical properties, in particular the yield and the ultimate stresses, of polyolefins is studied. PP and SEBS copolymer blends are used as examples and foamed after sorption of CO₂ at temperatures below T_m. CO₂ sorption thickens the crystalline lamellae and consequently increases T_m from 160 to 178 °C for both pure PP and PP/SEBS blend systems. Foams with an average cell size smaller than 250 nm retain the ultimate stress at the level of the polymer before foaming, even without the effect of CO₂‐induced crystallization. Including CO₂‐induced crystallization, the yield and the ultimate stresses of the foam can be improved by 30 and 50% over solid PP and by 22 and 40%, for solid PP/SEBS blends, respectively.

     

Formation of Thermosets via Molecular Pockets in Thermoplastic Chains: A Simple and Direct Way to Nanospherical Thermosets

By curing bisphenol A‐based benzoxazine in a thermoplastic polystyrene‐block‐poly (ethylene‐co‐1‐butene)‐block‐polystyrene (SEBS) block copolymer, nanospherical polybenzoxazines as small as 150 nm with narrow size distribution are obtained in high yield. This specific condition allows simple and direct formation of nano‐ or microspherical thermoset resins. A model of how the thermoplastic block copolymer chains act as a molecular pocket where the thermoset curing proceeds is presented. It is demonstrated that this mechanism requires (i) a particular block of thermoplastic copolymer which allows specific interaction with monomeric thermoset molecules, and (ii) the curing of thermosets in a molecular assembly structure to confine the phase separation of thermoset prepolymer during curing.

     

Use of Monomethyl Itaconate Grafted Poly(propylene) (PP) and Ethylene Propylene Rubber (EPR) as Compatibilizers for PP/EPR Blends

The use of grafted poly(propylene) (PP) and a random copolymer of ethylene and propylene (EPR) with an itaconic acid derivative, monomethyl itaconate (MMI), as compatibilizer for PP/EPR blends was analyzed. The grafting reaction was performed at 190 °C in a Brabender Plasticorder. 2,5‐Dimethyl‐2,5‐bis(tert‐butylperoxy) hexane was the radical initiator for the functionalization of PP; dicumyl peroxide was used as the radical initiator for the modification of EPR. The obtained degree of grafting was 1.5% by weight for PP and 1.2% by weight for EPR. The compatibilizing effect of modified polymers on the processability, morphology, and mechanical and thermal properties of the blends was of interest. Compatibilization substantially improved the toughness and deformation with little effect on the tensile modulus and strength. Moreover, this effect was particularly evident when both polymeric phases were grafted. Regarding compatibilization, the viscosity of the blends increased due to the high interfacial adhesion. Morphological studies showed that the particle size of the rubbery phase was reduced and the dispersion in the matrix improved by compatibilization. The grafted polymers behaved as nucleating agents, accelerating the PP crystallization.

Change in complex viscosity with angular frequency at 180 °C for unmodified and MMI‐functionalized PP/EPR (70/30) blends.     

Waste and Virgin LDPE/PET Blends Compatibilized with an Ethylene‐Butyl Acrylate‐Glycidyl Methacrylate (EBAGMA) Terpolymer, 1

Summary: This work is aimed at studying the morphology and the mechanical properties of blends of low density polyethylene (LDPE) and poly(ethylene terephthalate) (PET) (10, 20, and 30 wt.‐% of PET), obtained as both virgin polymers and urban plastic waste, and the effect of a terpolymer of ethylene‐butyl acrylate‐glycidyl methacrylate (EBAGMA) as a compatibilizer. LDPE and PET are blended in a single screw extruder twice; the first extrusion to homogenize the two components, and the second to improve the compatibilization degree when the EBAGMA terpolymer is applied. Scanning electron microscopy (SEM) analysis shows that the fractured surface of both the virgin polymer and the waste binary blends is characterized by a gross phase segregation morphology that leads to the formation of large PET aggregates (10–50 µm). Furthermore, a sharp decrease in the elongation at break and impact strength is observed, which denotes the brittleness of the binary blends. The addition of the EBAGMA terpolymer to the binary LDPE/PET blends reduces the size of the PET inclusions to 1–5 µm with a finer dispersion, as a result of an improvement of the interfacial adhesion strength between LDPE and PET. Consequently, increases of the tensile properties and impact strength are observed.

SEM micrographs of the fracture surface of a waste 70/30 LDPE/PET blend (R30) and of its blend with 15 pph of EBAGMA (R30C). Magnification × 1 000.     

Compatibilizing Effect of SEBS for Electrical Properties of LDPE/PS Blends

Summary: In the previous study, we observed compatibilizing effects of low density polyethylene (LDPE)/polystyrene (PS) with polystyrene‐block‐poly(ethylene‐co‐butylene)‐block‐polystyrene (SEBS), a triblock copolymer. Blends consisting of 70 wt.‐% LDPE and 30 wt.‐% PS were prepared with a SEBS concentration of up to 10 wt.‐%. This study examined the electrical properties such as the electrical breakdown, water tree length, permittivity and tan δ in the blends. The possibility of using these blends as insulating material substitutes for LDPE was investigated. The electrical breakdown strength reached a maximum of 66.67 kV/mm, which is superior to 50.27 kV/mm of the LDPE used as electrical insulators for cables. In addition, the water tree length decreased with increasing SEBS concentration. The water tree lengths of the blends containing SEBS were shorter than that of the LDPE. The permittivity of the blends was 2.28–2.48 F/m, and decreased with increasing SEBS concentration with the exception of S‐0. Tan δ of the blends increased smoothly with increasing SEBS content.

Breakdown strength , water tree length, permittivity and tan δ of the LDPE/PS/SEBS blends and raw materials.     

Elaboration of Poly(ε‐caprolactone)‐g‐TiNbO5 Nanocomposites via in situ Metal Complex Initiated Intercalative Polymerization

Summary: The preparation of poly(ε‐caprolactone)‐g‐TiNbO₅ nanocomposites via in situ intercalative polymerization of ε‐caprolactone initiated by an aluminium complex is described. These nanocomposites were obtained in the presence of HTiNbO₅ mineral pre‐treated by AlMe₃, but non‐modified by tetraalkylammonium cations. These hybrid materials obtained have been characterized by Fourier transform infrared absorption spectroscopy, wide‐angle X‐ray scattering, scanning electron microscopy, and dynamic mechanical analysis. Layered structure delamination and homogeneous distribution of mineral lamellae in the poly(ε‐caprolactone) (PCL) is figured out and strong improvement of the mechanical properties achieved. The storage modulus of the nanocomposites is enhanced as compared to pure PCL and increases monotonously with the amount of the filler in the range 3 to 10 wt.‐%.

SEM image of the fractured surface of a PCL‐TiNbO₅ nanocomposite film.