Nanostructure Evolution Mechanisms During Slow Load‐Cycling of Oriented HDPE/PA Microfibrillar Blends as a Function of Composition

Oriented precursors of MFCs consisting of HDPE and PA6 or PA12 are studied during strain‐controlled slow load‐cycling. In the PA6‐containing blends a strongly retarded nanostrain response is detected. Compatibilization induces nanostrain heterogenization. Stress fatigue is lower in the PA12 blends, but hardly decreased by the compatibilizer. Selective migration of the compatibilizer into a disordered semi‐crystalline fraction of the HDPE matrix can explain the findings. The semi‐crystalline HDPE entities in PA6 blends appear more disordered than in PA12‐blends. An analysis of the HDPE nanostructure evolution during cycling reveals epitaxial strain crystallization. Uncompatibilized PA6 blends cycled about high pre‐strain show plastic flow but nanoscopic shrinkage in the semi‐crystalline stacks.

     

Effect of Compatibilizer Concentration on Rheological Behavior,Morphologies, and Mechanical Properties of PVDF/TPU Blends

The rheological behavior, morphologies, and tensile properties of reactively compatibilized PVDF/TPU blends are reported. Using PVDF‐g‐AAc as the compatibilizer, PVDF/TPU 90/10 and 10/90 blends are prepared. The carboxylic acid groups of PVDF‐g‐AAc react with the urethane linkages of TPU during melt blending to generate in situ PVDF‐g‐AAc‐g‐TPU which leads to compatibilization of PVDF/TPU blends. The introduction of PVDF‐g‐AAc into the PVDF/TPU blends causes an increase in viscosity. The rheological behavior of the compatibilized PVDF/TPU 90/10 and 10/90 blends are well described by the generalized Zener model. The addition of the compatibilizer PVDF‐g‐AAc reduces the dispersed‐phase domain size and narrows the size distribution. ?Author: The summary has been shortened to comply with the maximum of 700 characters. Pls check/confirm changes!?

     

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.     

Compatibilization of Poly(propylene)/Polyamide 6 Blends with Functionalized Poly(propylene)s Prepared with Metallocene Catalyst

Summary: Propylene was copolymerized with 10‐undecen‐1‐ol using dimethylsilanylbis(2‐methyl‐4‐phenyl‐1‐indenyl)zirconium dichloride as catalyst and MAO and TIBA as cocatalysts. Comonomer incorporations from 0.1 to 0.9 mol‐% (0.5 to 3.6 wt.‐%) were obtained. These hydroxyl functionalized copolymers were applied as compatibilizers to PP/PA6 blend with a composition of 70/30. For comparison, hydroxyl functionalized polyethylene prepared with metallocene catalyst and commercial MAH grafted ethylene butyl acrylate (E/BA/MAH) and poly(propylene) (PP‐g‐MAH) were also used as compatibilizers. Effects of the compatibilizers on morphology and mechanical and thermal properties of the blends were studied. Enhanced adhesion between the blend components was observed in morphology and dynamic mechanical studies. Although improvement in toughness was not as pronounced as expected, there were indications that the hydroxyl functionalized propylene copolymers prepared with metallocene catalysts could serve as a new type of compatibilizer in polymer blends.

SEM micrograph (5 000×) of an PP/PA6/PP‐co‐OH4 blend.     

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.     

Extrusion Foaming of Poly (lactic acid)/Soy Protein Concentrate Blends

Poly(lactic acid) (PLA) and soy protein concentrate (SPC) were compounded using poly(2‐ethyl‐2‐oxazoline) as compatibilizer by twin‐screw extrusion, and the resulting blends were foamed by a chemical blowing agent (CBA) using the same extruder. Effects of foaming temperature and CBA content on cell density and foam density were investigated. Polymeric methylene diphenyl diisocyanate (pMDI) as a co‐compatibilizer was added prior to foaming extrusion and its effects on foam morphology and properties were also studied. The results showed that cell density and foam density were greatly influenced by foaming temperature and CBA content. Using the strong interfacial modifier pMDI in PLA/SPC blends resulted in high‐cell density and low‐foam density when CBA concentration was low.

     

Intercalated Polycarbonate/Clay Nanocomposites: Nanostructure Control and Foam Processing

Intercalated polycarbonate (PC)/clay nanocomposites (PCCN)s have been prepared successfully through the melt intercalation method in the presence of a compatibilizer. The internal structure and morphology of the PCCNs has been established by using wide‐angle X‐ray diffraction (WAXD) analyses and transmission electron microscopic (TEM) observations. The morphology of these nanocomposites and degradation of the PC matrix after nanocomposites preparation can be controlled by varying surfactants used for the modification of clay and compatibilizer. The intercalated PCCNs exhibited remarkable improvements of mechanical properties when compared with PC without clay. We also discuss foam processing of one representative PCCN using supercritical CO₂ as a foaming agent.

TEM bright field image of intercalated polycarbonate/synthetic fluorohectorite nanocomposite.     

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.     

Reactive Compatibilizer Precursors for LDPE/PA6 Blends, 4

Summary: The effectiveness of some thermoplastic elastomers grafted with maleic anhydride (MA) or with glycidyl methacrylate (GMA) as compatibilizer precursors (CPs) for blends of low density polyethylene (LDPE) with polyamide‐6 (PA) has been studied. The CPs were produced by grafting different amounts of MA or GMA onto a styrene‐block‐(ethylene‐co‐1‐butene)‐block‐styrene copolymer (SEBS) (KRATON G 1652), either in the melt or in solution. A commercially available SEBS‐g‐MA copolymer with 1.7 wt.‐% MA (KRATON FG 1901X) was also used. The effect of the MA concentration and of other characteristics of the SEBS‐g‐MA CPs was also studied. The specific interactions between the CPs and the blends components were investigated through characterizations of the binary LDPE/CP and PA/CP blends, in the whole composition range. It was demonstrated that the SEBS‐g‐GMA copolymers display poor compatibilizing effectiveness due to cross‐linking resulting from reactions of the epoxy rings of these CPs with both the amine and the carboxyl end groups of PA. On the contrary, the compatibilizing efficiency of the MA‐grafted elastomers, as revealed by the thermal properties and the morphology of the compatibilized blends, was shown to be excellent. The results of this study confirm that the anhydride functional groups possess considerably higher efficiency, for the reactive compatibilization of LDPE/PA blends, than those of the ethylene‐acrylic acid and ethylene‐glycidyl methacrylate copolymers investigated in previous works.

SEM micrograph of the 75/25 LD08/PA blend (with 2 phr SEBSMA1).     

The Solid State Postcondensation of PET, 2

Summary: A process for the solid state polycondensation of PET is proposed. It is shown that by correctly choosing the prepolymerisation conditions it is possible to crystallise the product and to directly polymerise it in a dispersed phase. This process is significantly faster than the “standard” PET processes, and allows one to obtain high molecular weights directly from a prepolymer without the need to use an intermediate solution polymerisation step.

Reactor set‐up for precursor preparation and dispersed phase prepolymerisation.     

Use of SEBS/EPR and SBR/EPR as Binary Compatibilizers for PE/PP/PS/HIPS Blends: A Work Oriented to the Recycling of Thermoplastic Wastes

Recycling of thermoplastic wastes consisting of PE/PP/PS/HIPS blends was investigated by using SEBS/EPR and SBR/EPR as compatibilizers. The effect of the binary compatibilizer systems and processing conditions on the mechanical properties and morphology of the blends are discussed. The SEBS/EPR system allowed blends with better mechanical properties to be obtained than the SBR/EPR system; this was attributed to the chemical structure similarity between compatibilizers and recycled materials. The optimal conditions for processing of the recycled thermoplastics (blends) were found to be 190 °C, 14 min of processing time and 3.5 wt.‐% of compatibilizer. The morphology and mechanical properties of the blends were discussed using theoretical phase diagrams and models proposed in the literature, and good agreements between these properties were found.

     

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).     

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.     

Using Nanosilica to Fine‐Tune Morphology and Properties of Polyamide 6/Poly(propylene) Blends

The effect of hydrophilic and hydrophobic nanosilica on the morphological, mechanical and thermal properties of polyamide 6 (PA) and poly(propylene) (PP) blends is investigated by extrusion compounding. Depending on the difference between the polymer/nanoparticle interfacial tensions, different morphologies are obtained as highlighted by TEM and SEM. Hydrophobic nanosilica migrates mainly at the PA/PP interface, which leads to a clear refinement of PP droplet size. The macroscopic properties of the hybrid blends are discussed and interpreted in relation with the blend morphology and melt‐mixing procedure. The control over coalescence allows a morphology refinement of the blends and improves mechanical properties.

     

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.     

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.     

Preparation and Combustion Properties of Flame Retardant Nylon 6/Montmorillonite Nanocomposite

Flame retardant Nylon 6 (PA6)/montmorillonite (MMT) nanocomposites have been prepared using direct melt intercalation technique by blending PA6, organophilic clay and conventional fire retardants, such as the melamine cyanurate (MCA) and the combination of decabromodiphenyl oxide (DB) and antimony oxide (AO). Their morphology and combustion properties are characterized by XRD, transmission electron microscopy (TEM), UL‐94 test and Cone Calorimeter experiments. The flame retardant nanocomposites with MCA or DB and AO show lower heat release rate (HRR) peak compared to that of conventional flame retardant PA6. Meanwhile, the synergetic effect was studied between clay and DB‐AO.

TEM of PA‐n nanocomposite.     

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.     

Reactive Blending of Polyamides with Different Carbonyl Containing Olefin Polymers

In this paper the blending of polyamides nylon 6 and nylon 12, with a perfectly alternating ethylene/CO copolymer containing 50 mol‐% carbonyl groups (polyketone) is investigated in comparison to blends of the same polyamides with polyolefins containing varying degrees of carbonyl group incorporation. These include a poly[ethylene‐co‐(methyl acrylate)] copolymer containing 1.9 mol‐% methyl ester groups and poly[ethylene‐co‐(ethyl undecylenate)] copolymers with between 0.20 and 1.25 mol‐% ester incorporation. Blends were obtained of polyamides and the polyolefins in compositions between 20/80 and 80/20 in solution and in a Brabender mixer. SEM studies together with TGA, DSC and FTIR measurements show excellent compatibilization for both polyketone and poly[ethylene‐co‐(methyl acrylate)] copolymers with the nylons. The poly[ethylene‐co‐(ethyl undecylenate)] polymers displayed much less compatibilization although they still performed significantly better compared to pure polyethylene. The difference in compatibilization is discussed with respect to the importance of both the number of interactive groups present in the polyolefin and the steric requirements of hydrogen bond formation.

SEM micrograph of the fracture surface of the blend nylon 6/polyethylene 70:30.     

High Compatibility and Improved Barrier Performance in Blends Based on a Copolyester Modified with a Poly(amino ether) Resin

Summary: The structure and properties of blends of a PCTG and a PAE resin obtained by direct injection molding have been studied. The blends were almost immiscible, and were composed of a nearly pure PAE phase and a mixed PCTG‐rich phase containing minor PAE amounts. Electron microscopy observations showed a high intermixing level between both components. The permeability data indicated an improved barrier protection of PCTG upon PAE addition. The Young's modulus and the yield stress of the blends followed a linear behavior with respect to composition, while values close or slightly below linearity were observed for the break properties. The combined effects of the small dispersed particle size and the proposed good interfacial adhesion are stated as the main factors responsible for the positive mechanical behavior. The impact strength showed an unexpected variability for PCTG‐rich blends, which is attributed to a ductile‐brittle transition of PCTG.

Ductility of PCTG/PAE blends vs. composition.