Photo-oxidation behaviour of polyethylene/polyamide 6 blends filled with organomodified clay: Improvement of the photo-resistance through morphology modification

The impact of small amounts of organomodified clay (OMMT) on the photo-degradation behaviour of two blends obtained by mixing either low-density polyethylene (LDPE) or high density polyethylene (HDPE) with polyamide 6 (PA6) (LDPE/PA6 and HDPE/PA6 75/25 wt-%) was studied. The complex photo-degradation behaviour was followed by monitoring the main physical-mechanical properties of the blends. In particular, mechanical and spectroscopic tests were performed in conditions of accelerated artificial aging. An accurate mechanical and morphological characterization was previously carried out. The presence of the OMMT promotes the unexpected formation of a co-continuous morphology for the HDPE/PA6 blend without significantly improving the interfacial adhesion. Differently, the OMMT-filled LDPE/PA6 blend exhibits a finely distributed morphology, and some apparent improvement of the interfacial adhesion was noticed. Probably due to these differences in microstructure, a different impact of the nanoparticles on the photo-resistance behaviours was observed for the two families of samples. In particular, the HDPE-based nanocomposite blend exhibits an improved photo-resistance, while the opposite occurs for the LDPE-based system.     

Fractionated crystallization of compatibilized LDPE/PA6 blends

The paper presents differential scanning calorimetry and electron microscopy of the fractionated crystallization and polydispersity of the dispersed PA6 phase in compatibilized LDPE/PA6 75/25 w/w blends. The compatibilizers used were (i) an acrylic acid functionalized polyethylene, Escor 5001 (EAA); (ii) an ethylene-glycidylmethacrylate copolymer, Lotader GMA AX8840 (EGMA); (iii) a polystyrene-poly(ethylene-butylene)-polystyrene triblock copolymer comprising 2 wt.% maleic anhydride grafts, Kraton FG 1901X (SEBS-g-MA). The compatibilizer SEBS-g-MA has the strongest reduction effect upon the size of PA-6 droplets. Its implementation provides the best fractionated crystallization. The fractionated crystallization has not been observed for the blend compatibilized with EGMA. The results show that the degree of compatibilization could be evaluated qualitatively by the progress of the fractionated crystallization. So, the three compatibilizers could be rated according to their effectiveness as follows: SEBS-g-MA > EAA > EGMA. The self-nucleation experiments have demonstrated that the lack of active nuclei in the finely dispersed PA6 droplets is the determining factor for the fractionated crystallization at high supercooling, and not the considered absolute particle size. The measurement of the Vickers microhardness of the compatibilized blends confirms that the compatibilizing activity of SEBS-g-MA and EAA is stronger than that of EGMA.     

Microhardness and thermal stability of compatibilized LDPE/PA6 blends

Microhardness tests, water absorption and thermogravimetric measurements have been performed on blends of low density polyethylene (LDPE) with different molar mass and polyamide 6 (PA6) compatibilized with 2 pph poly(ethylene-co-acrylic acid) (Escor 5001 by Exxon). The negative deviation of Vickers microhardness from the additivity has been interpreted by changes in the crystallinity of the blend components. The hardness values of the compatibilized blends that are lower than those of the corresponding uncompatibilized blends have been explained by the decrease of the degree of crystallinity of PA6 phase in the presence of Escor. The molar mass of LDPE almost does not influence on the hardness values. The lower water absorption of the compatibilized blends, caused by the formation of a copolymer between PA6 and the compatibilizer leads to microhardness values of the wet compatibilized blends higher than those of the corresponding uncompatibilized blends. The thermogravimetric measurements demonstrate that the thermal stability of blends increases in the presence of 2 pph Escor 5001. The results confirm the compatibilizing efficiency of Escor 5001 towards LDPE/PA6 blends in a wide composition range.     

Influence of microstructure and deformation behavior on toughening of reactively compatibilized polyamide 6 and poly(ethylene-co-butyl acrylate) blends

Influence of microstructure on impact toughness and fracture behavior of PA6 and EBA blends reactively compatibilized by EBA-g-MAH was quantitatively studied. The reactively compatibilized blends showed better distribution of elastomeric EBA particles in the PA6 matrix and the presence of EBA-g-MAH resulted in considerable reduction of interfacial tension between the component polymers. The interfacial adhesion between the PA6 and EBA phase in the compatibilized blends was enhanced by the interfacial reaction between the amide end-groups of PA6 and maleic anhydride group of EBA-g-MAH compared to uncompatibilized blends. The matrix ligament thickness and particle diameter values were lower than the predicted critical values and were responsible for the ductile behavior of the compatibilized blends. Stress whitening around the notch occurred in all the compatibilized blends which was the major energy dissipation zone in the blends. Matrix shear yielding or plastic flow without crazing was the dominant deformation mechanism in the tough compatibilized blends. There was no sign of shear yielding during impact fracture of the uncompatibilized blends where the elastomeric particles were completely dislodged from the matrix.     

A study on melt grafting of maleic anhydride onto low‐density polyethylene and its blend with polyamide 6

Graft copolymerization of low‐density polyethylene (LDPE) with a maleic anhydride (MAH) was performed using intermeshing corotating twin‐screw extruder in the presence of benzoyl peroxide (BPO). The LDPE/polyamide 6 (PA6) and LDPE‐g‐MAH/PA6 blends were prepared in a corotating twin‐screw extruder. The melt viscosity of the grafted LDPE was measured by a capillary rheometer. The grafted copolymer was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microcopy (SEM). The influence of the variation in temperature, BPO and MAH concentration, and temperature on the grafting degree and on the melt viscosity was studied. The grafting degree increased appreciably up to about 0.45 phr and then decreased continuously with an increasing BPO concentration. According to the FTIR analysis, it was found that the amount of grafted MAH on the LDPE chains was ～5.1%. Thermal analysis showed that melting temperature of the graft copolymers decreases with increasing grafting degree. In addition to this, loss modulus (E″) of the copolymers first increased little with increasing grafting and then obviously decreased with increasing grafting degree. Furthermore, the results revealed that the tensile strength of the blends increased linearly with increasing PA6 content. The results of SEM and mechanical test showed that the blends have good interfacial adhesion and good stability of the phase structure, which is reflected in the mechanical properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 267–275, 2010     

Impact properties,phase structure,compatibility, and fracture morphology of polyamide‐1010/thermoplastic poly(ester urethane) elastomer blends

Blends of polyamide‐1010 (PA1010) and a thermoplastic poly(ester urethane) elastomer (TPU) were prepared by melt extrusion. The impact properties, phase structure, compatibility, and fracture morphology under impact were investigated for PA1010/TPU blends. The results indicated that TPU enhanced the impact strength of PA1010, and the best impact modification effect of the blends was obtained with 20 wt % TPU. The phase structure was investigated with scanning electron microscopy, and the compatibility was investigated with dynamic mechanical analysis and small‐angle X‐ray scattering. The study of the fracture morphology of PA1010/TPU blends indicated that the fracture surface of the blends had special features, consisting of many fibrillar elastomer particles and a conglutination–multilayer structure, as well as many small tubers on this structure. These fracture phenomena could not be found on the fracture surface of pure PA1010. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1177–1185, 2005     

SYNERGISTIC MODIFICATION OF EPDM AND CROSSLINKING AGENT IN IMMISCIBLE BLENDS OF POLYVINYL CHLORIDE WITH LOW DENSITY POLYETHYLENE

The synergism of ethylene-propylene-diene monomer copolymer （EPDM） and dicumyl peroxide （DCP, a crosslinking agent） in low density polyethylene （LDPE）/poly（vinyl chloride） （PVC） blends was investigated. When EDPM and DCP are added to the blends simultaneously, the tensile properties could be improved significantly, especially for the blends with LDPE matrix. For example, incorporation of 10/1 （mass ratio） EPDM/DCP improves the tensile strength of the LDPE/PVC （mass ratio 80/20） blend from 7.9 MPa to 8.5 MPa and the elongation at break from 25% to 503%. Results from selective extraction, phase-contrast microscopy and thermal analysis reveal that the improvement in the tensile properties of the blends with LDPE matrix is principally due to the formation of a fine crosslinking network of the LDPE and EPDM phase. The outstanding modification effect of EPDM is explained by its dual functions： molecular entanglement with LDPE and the enhanced efficiency of DCP in the blends.     

Effects of poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] on the charge distributions of low‐density polyethylene/polystyrene blends

The effect of the triblock copolymer poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) on the formation of the space charge of immiscible low‐density polyethylene (LDPE)/polystyrene (PS) blends was investigated. Blends of 70/30 (wt %) LDPE/PS were prepared through melt blending in an internal mixer at a blend temperature of 220 °C. The amount of charge that accumulated in the 70% LDPE/30% PS blends decreased when the SEBS content increased up to 10 wt %. For compatibilized and uncompatibilized blends, no significant change in the degree of crystallinity of LDPE in the blends was observed, and so the effect of crystallization on the space charge distribution could be excluded. Morphological observations showed that the addition of SEBS resulted in a domain size reduction of the dispersed PS phase and better interfacial adhesion between the LDPE and PS phases. The location of SEBS at a domain interface enabled charges to migrate from one phase to the other via the domain interface and, therefore, resulted in a significant decrease in the amount of space charge for the LDPE/PS blends with SEBS. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2813–2820, 2004     

Thermomechanical study of low-density polyethylene, polyamide 6 and its blends

By using thermomechanical analysis (TMA) multiple relaxation transitions in the amorphous part of semi-crystalline polymers and their blends can be found. These result from differences in the interaction energies between segments of macromolecules, and as a result, in molecular mobility. TMA shows essential changes in the structure of low-density polyethylene (LDPE) resulting from the grafting of a maleic anhydride (LDPE-g-MAH) onto this semi-crystalline polymer. The grafting process did not suppress the ability of polyethylene to crystallize. Essential changes were found in molecular weight distribution and relaxation transitions of the ternary blends LDPE/PA6 (polyamide 6, PA6)/LDPE-g-MAH studied. For a concentration of PA6 up to 30 wt.%, a single relaxation transition is visible, which testifies that the components are miscible in the amorphous region. For blends with 40 and 50 wt.% of PA6, this structure was transformed and two relaxation transitions are visible. From the results obtained in this study it is concluded that the introduction 5 wt.% of grafted polyethylene is sufficient to produce a PA6/LDPE blend only for PA6 concentration up to 30 wt.% which is homogenous on “molecular” level. The transformation of the structure of the ternary polymer blend was explained by the interaction of the components during the melt mixing and changes in the structure of its amorphous regions.     

EFFECTS OF COMPATIBILIZERS ON THE MECHANICAL PROPERTIES OF LOW DENSITY POLYETHYLENE/LIGNIN BLENDS

Low density polyethylene(LDPE)/lignin blends were prepared using melt blending.Two kinds of compatibilizers, ethylene-vinylacetate(EVA) which is softer than LDPE and polyethylene grafted with maleic anhydride(PE-g-MA) which is harder than LDPE were used to improve the interfacial adhesion.Scanning electron microscope(SEM) was used to investigate the dispersion of lignin in LDPE matrix.The results showed that both of the compatibilizers could improve the interaction between the low density polyethylene an...     

Phase morphology development in PP/PA6 blends induced by a maleated thermoplastic elastomer

The effects of maleated thermoplastic elastomer (TPEg) on morphological development of polypropylene (PP)/polyamide 6 (PA6) blends with a fixed PA6 content (30 wt %) were investigated. For purpose of comparison, nonmaleated thermoplastic elastomer (TPE) was also added to the above binary blends. A comparative study of FTIR spectroscopy in above both ternary blends confirmed the formation of in situ graft copolymer in the PP/PA6/TPEg blend. Dynamic mechanical analysis (DMA) indicated that un‐like TPE, the incorporation of TPEg remarkably affected both intensity and position of loss peaks of blend components. Scanning electron microscopy (SEM) demonstrated that PP/PA6/TPE blends still exhibited poor interfacial adhesion between the dispersed phase and matrix. However, the use of TPEg induced a finer dispersion and promoted interfacial adhesion. Transmission electron microscopy (TEM) for PP/PA6/TPEg blends showed that a core‐shell structure consisting of PA6 particles encapsulated by an interlayer was formed in PP matrix. With the concentration of TPEg increasing, the dispersed core‐shell particles morphology was found to transform from discrete acorn‐type particles to agglomerate with increasing degree of encapsulation. The modified Harkin's equation was applied to illustrate the evolution of morphology with TPEg concentration. “Droplet‐sandwiched experiments” further confirmed the encapsulation morphology in PP/PA6/TPEg blends. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1050–1061, 2006     

Specific properties of in situ ruthenium‐catalyzed polyamide 12/polydimethylsiloxane compatibilized blend

The main objective of this work focused on the chemical modification of polyamide 12 (PA12) properties through the reaction with a hydride‐terminated polydimethylsiloxane (PDMS‐SiH). The investigated PA12/PDMS‐SiH blend was compatibilized by ruthenium derivative catalyzed hydrosilylation reaction in molten state. This original route enhanced interfacial adhesion and avoid PDMS‐SiH leaching phenomenon between the two immiscible phases. More specifically, the size of PDMS‐SiH domains in the blend decreased from around 4 μm to 800 nm and from 30 to 1 μm after compatibilization with 10 and 20 wt % PDMS‐SiH, respectively. For the best compatibilized PA12/PDMS‐SiH blend, the introduction of PDMS lowered the surface free energy and the PA12‐based blend turned from hydrophilic to hydrophobic behavior, as evidenced by the water contact angle measurements. Gas permeability and CO₂/H₂ and CO₂/He gas selectivity were also improved with the increase in PDMS content. Besides, the mechanical properties were enhanced with 13% increase in Young's modulus after in situ compatibilization with 15 wt % PDMS‐SiH. Thermal stability was also improved after compatibilization as the initial degradation temperature of reactive blends obviously increased compared with nonreactive ones. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 978–988     

Biosourced Poly(lactic acid)/polyamide-11 Blends: Effect of an Elastomer on the Morphology and Mechanical Properties

Fully biobased polylactide (PLA)/polyamide-11 (PA11) blends were prepared by melt mixing with an elastomer intermediate phase to address the low elasticity and brittleness of PLA blends. The incorporation of a biobased elastomer made of poly(butylene adipate-co-terephthalate) (PBAT) and polyethylene oxide (PEO) copolymers was found to change the rigid interface between PLA and PA11 into a much more elastic/deformable one as well as promote interfacial compatibility. The interfacial tension of the polymer pairs and spreading coefficients revealed a high tendency of PEO to spread at the PLA/PA11 interface, resulting in a complete wetting regime (interfacial tension of 0.56 mN/m). A fully percolated rubbery phase (PEO) layer at the PLA/PA11 interface with enhanced interfacial interactions and PLA chain mobility contributed to a better distribution of the stress around the dispersed phase, leading to shear yielding of the matrix. The results also show that both the morphological modification and improved compatibility upon PEO addition (up to 20 wt %) contributed to the improved elongation at break (up to 104%) and impact strength (up to 292%) of the ternary PLA/PA11/PEO blends to obtain a super-tough multiphase system.     

Effect of ethylene-acrylic acid copolymer on flame retardancy and properties of LLDPE/EAA/MH composites

Halogen-free flame retardant linear low density polyethylene (LLDPE)/ethylene-acrylic acid copolymer (EAA) blends were prepared in a melt process using magnesium hydroxide (MH) as flame retardant. The effect of EAA on flame retardancy and properties of LLDPE/EAA/MH composites was studied. The flammability of composites was investigated using Limiting Oxygen Index (LOI) and Cone calorimeter test. The results showed that the introduction of EAA into composites apparently increased LOI from 28% to 39%, meanwhile, reduced heat release rate (HRR) and smoke production rate (SPR) according to Cone calorimeter results, which was mainly due to the uniform dispersion of MH as a result of hydrogen bonding and acid-base reaction between MH and EAA. This improved interfacial adhesion was confirmed by Scanning Electronic Microscopy (SEM). Thermogravimetric analysis (TGA) showed that EAA could enhance the thermal oxidative stability of composites. It was attributed to the formation of a stable barrier to prevent the heat and mass transfer in fire, which was confirmed by the observation of fire performance with Cone calorimeter. The crystallization and rheological behaviour of composites were studied using Differential scanning calorimeter (DSC) and oscillatory rheological measurements. Mechanical test results indicated that the addition of EAA could increase the elongation at break and impact strength of composites.     

磨盘碾磨制备PA6/PP/SBS共混物的结构与性能

采用磨盘形力化学反应器,在室温下制备了PA6/PP超细混合粉体,与SBS共混制得PA6/PP/SBS共混物,测定了材料的力学性能并用TEM研究了材料在不同加工温度下相结构的变化.结果表明,通过固相力化学粉碎制备的PA6/PP混合微粉,改善了PA6与PP和SBS的相容性,促进了PA6及PP的分散和与SBS的相界面结合.在微粉填充量为4%～8%(质量分数)时,材料的拉伸强度大幅度提高,扯断伸长率保持不变.加工温度变化引起材料相结构的变化对材料性能产生显著影响.在PP熔融温度下加工,PP粒子产生粘连形成链状结构,可提高材料的力学性能.     

Reactive compatibilization of PA12/plasticized starch blends: Towards improved mechanical properties

Glycerol-plasticized starch (TPS)/polyamide 12 (PA12) blends were processed by melt mixing using two types of interfacial agent, i.e. diglycidyl ether of bisphenol A and a poly(ethylene-co-butyl acrylate-co-maleic anhydride) copolymer. Morphologies of the blends were tailored from the nature and amount of the interfacial agents. The average size of the dispersed phase was shown to decrease with the incorporation of the reactive agents and was proved to respect models, usually employed for conventional blends, for size predictions of the dispersed phase. By means of rheological experiments, it has been investigated whether the size reduction of the dispersed phase was coming from the compatibilization of the blend or from the viscosity changes due to chain extension in the matrix. The influence of the coupling agents on the viscoelastic behavior of the blend was characterized. Both interfacial agents led to increase the absolute complex viscosity but in the case of diepoxy reactive agent, the Newtonian flow behavior of complex viscosity totally disappeared in the low-frequency region. Mechanical properties of the TPS/PA12 blends were characterized and were proved to be strongly impacted by the use of interfacial agents. Elongation at break was enhanced as a consequence of a better adhesion between the matrix and the dispersed phase, whereas a decrease of the Young’s modulus was observed with increasing DGEBA content. Polyamide 12 crystallization in TPS/PA12 blends was found to be strongly dependent on DGEBA content while the introduction of maleic anhydride-grafted copolymer had no influence.     

Polymer blends of sPS/PA6 compatibilized by sulfonated syndiotactic polystyrene

Syndiotactic polystyrene (sPS) and polyamide-6 (PA6) are immiscible and incompatible and have been recognized. In this study, sulfonated syndiotactic polystyrene (SsPS-H) is employed as compatibilizer in the blend of sPS/PA6. During melt blending, the sulfonic acid groups of the SsPS-H can interact strongly with the amine end-groups of PA6 through acid-base interaction. In addition, SsPS-H is miscible with sPS when SsPS-H content is less than 20 wt.%. Therefore, the addition of SsPS-H to sPS/PA6 blends reduces the dispersed phase size and improves the adhesion between the phases. The glass transition temperatures of the PA6 component in the compatibilized blends shift progressively towards higher temperature with the content of SsPS-H-12 increase, indicating enhanced compatibility. On the other hand, the progressive lowering of the melting point and crystallization temperatures of PA6 in the blends with increasing SsPS-H contents compared to the incompatibilized blend, provide some insight into the level of interaction between the PA6 and SsPS-H. The compatibilized blends have significantly higher impact strength than the blends without SsPS-H. The best improvement in the impact strength of the blends was achieved with the content of the SsPS-H (11.9 mol%) about 5 wt.%.     

The compatibilization effect of ethylene/styrene interpolymer on polystyrene/polyethylene blends

In this study, ethylene/styrene interpolymer (ESI) was used as compatibilizer for the blends of polystyrene (PS) and low‐density polyethylene (LDPE). The mechanical properties including impact, tensile properties, and morphology of the blends were investigated by means of uniaxial tension, instrumented falling‐weight impact measurements, and scanning electron microscopy. Impact measurements indicated that the impact strength of the blends increases slowly with LDPE content up to 40 wt %; thereafter, it increases sharply with increasing LDPE content. The impact energy of the LDPE‐rich blends exceeded that of pure LDPE, implying that the LDPE polymer can be further toughened by the incorporation of brittle PS minor phase in the presence of ESI. Tensile tests showed that the yield strength of the PS/LDPE/ESI blends decreases considerably with increasing LDPE content. However, the elongation at break of the blends tended to increase significantly with increasing LDPE content. The compatibilization efficiency of ESI and polystyrene‐hydrogenated butadiene‐polystyrene triblock copolymers (SEBS) for PS/LDPE 50/50 was further compared. Mechanical properties show that ESI is more effective to achieve a combination of LDPE toughness and PS rigidity than SEBS. The correlation between the impact property and morphology of the ESI‐compatibilized PS/LDPE blends is discussed. The excellent tensile ductility of the LDPE‐rich blends resulted from shield yielding of the matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2136–2146, 2007     

PA6/HIPS/PP-g-(GMA-co-St)反应共混体系的研究

通过扫描电镜、热分析、熔体流动速率、熔融扭矩和力学性能等测试方法研究了甲基丙烯酸缩水甘油酯(GMA)和苯乙烯(St)多单体熔融接枝聚丙烯[PP-g-(GMA-co-St)]对PA6/HIPS共混物的熔融流变性能、结晶行为、相形态和力学性能的影响.结果表明,在熔融共混过程中,PP-g-(GMA-co-St)中的环氧基与PA6的端氨基原位生成的接枝共聚物有效地降低了共混物的界面张力,提高了共混物的界面粘着力,使共聚物的流动速率降低,熔融扭矩提高;PA6分子链的规整性降低,结晶完善性变差.在PP-g-(GMA-co-St)的质量分数为10%时,共混物分散相的尺寸明显减少,力学性能得到较大提高;其中冲击强度超过纯PA6,达到HIPS水平.通过反应共混,制备了力学性能均衡的PA6/HIPS/PP-g-(GMA-co-St)共混物合金.     

刚性粒子增韧尼龙1010体系的研究

采用扫描电镜和动态力学等研究了在磺化聚苯乙烯（ＨＳＰＳ）作用下，尼龙１０１０（ＰＡ１０１０）／聚苯乙烯（ＰＳ）共混物的形态及相容性。结果表明，ＨＳＰＳ的加入显著改善了ＰＳ与ＰＡ１０１０的相容性，加强了界面粘结，使共混物缺口冲击明显提高，实现了ＰＳ增韧ＰＡ１０１０的目标。偏光显微竟结盟表明，ＨＳＰＳ的加入对共混物中ＰＡ１０１０的结晶形态有明显影响，使ＰＡ１０１０球晶细化且不完善。