Influence of carbon nanotube-polymeric compatibilizer masterbatches on morphological, thermal, mechanical, and tribological properties of polyethylene

Study was made of the effect of multiwall carbon nanotubes (MWCNTs) and polymeric compatibilizer on thermal, mechanical, and tribological properties of high density polyethylene (HDPE). The composites were prepared by melt mixing in two steps. Carbon nanotubes (CNTs) were melt mixed with maleic anhydride grafted polyethylene (PEgMA) as polymeric compatibilizer to produce a PEgMA-CNT masterbatch containing 20 wt% of CNTs. The masterbatch was then added to HDPE to prepare HDPE nanocomposites with CNT content of 2 or 6 wt%. The unmodified and modified (hydroxyl or amine groups) CNTs had similar effects on the properties of HDPE-PEgMA indicating that only non-covalent interactions were achieved between CNTs and matrix. According to SEM studies, single nanotubes and CNT agglomerates (size up to 1 μm) were present in all nanocomposites regardless of content or modification of CNTs. Addition of CNTs to HDPE-PEgMA increased decomposition temperature, but only slight changes were observed in crystallization temperature, crystallinity, melting temperature, and coefficient of linear thermal expansion (CLTE). Young’s modulus and tensile strength of matrix clearly increased, while elongation at break decreased. Measured values of Young’s moduli of HDPE-PEgMA-CNT composites were between the values of Young’s moduli for longitudinal (E₁₁) and transverse (E₂₂) direction predicted by Mori-Tanaka and Halpin-Tsai composite theories. Addition of CNTs to HDPE-PEgMA did not change the tribological properties of the matrix. Because of its higher crystallinity, PEgMA possessed significantly different properties from HDPE matrix: better mechanical properties, lower friction and wear, and lower CLTE in normal direction. Interestingly, the mechanical and tribological properties and CLTEs of HDPE-PEgMA-CNT composites lie between those of PEgMA and HDPE.     

Influence of reactive compatibilizers on the rheometrical and mechanical properties of PA6/LDPE and PA6/HDPE blends

In this work, the influence of reactive compatibilizers on the rheometrical and mechanical properties of polyamide 6/low density polyethylene (PA6/LDPE) and polyamide 6/high density polyethylene (PA6/HDPE) blends was investigated. Polyethylene grafted with maleic anhydride (PEgMA), polyethylene grafted with acrylic acid (PEgAA), and ethylene-methyl acrylate-glycidyl methacrylate (EMA-GMA) were used as compatibilizers. The blends were characterized by torque rheometry, mechanical properties, and morphology. Rheometrical properties results show that PEgMA and PEgAA compatibilizers are more reactive with PA6 than EMA-GMA. Mechanical properties and scanning electron microscopy analysis results show that EMA-GMA compatibilizer is as effective as PEgMA and PEgAA for PA6/LDPE blend. For PA6/HDPE blend, PEgAA and EMA-GMA compatibilizers proved to be as effective as PEgMA. For PA6/HDPE blend compatibilized with PEgAA, an intriguing “web” or “bridge” like structure was observed.     

The influence of the structure of starch on the mechanical,morphological and thermal properties of poly (ε-caprolactone) in starch blends

In this work, the influence of three starches (A₁, A₂ and A₃) on the mechanical, morphological and thermal properties of poly(ε-caprolactone) (PCL) was investigated in PCL/starch blends of 0/100, 75/25, 50/50 and 25/75 w/w%. The addition of starch to PCL reduced the tensile stress at break, the elongation at break and Young’s modulus. The starches with linear chemical structures (A₁ and A₃) had lower values of tensile strength and higher values of elongation at break. Light microscopy indicated that the starches and PCL were immiscible. Thermal analysis showed that the 75/25, 50/50, and 25/75 w/w% blends containing linear starches had greater crystallinity than branched starch, an arrangement that may favor their biodegradation.     

Influence of free volume on the mechanical properties of Epoxy/poly (methylmethacrylate) blends

Positron lifetime measurements have been performed to investigate the free volume dependence of the mechanical properties of Epoxy/poly methyl methacrylate (PMMA) blends of varying composition of PMMA (2.5, 5, 7.5, 10, 12.5, 15, and 17.5 wt%). The mechanical properties of the blends have been evaluated according to the (ASTM) standard. The positron results indicate that the mechanical properties like tensile strength and surface hardness have a significant dependence on the free volume of the blends. It is also found that the blends of the present study show positive deviation from the familiar linear additivity rule suggesting the immiscible nature of the blends. Further, up to 5-wt% of PMMA in the blend, an increase in relative fractional free volume correlates well with a decrease of tensile strength.     

Processing and thermal,mechanical and morphological characterization of post-consumer polyolefins/thermoplastic starch blends

Mixtures of high density polyethylene (HDPE) and polypropylene (PP), both post-consumer polymers were blended with thermoplastic starch (TPS). Corn starch plastification was carried out by extrusion with glycerin addition. The behaviour of TPS produced was investigated in the processing and thermal, mechanical and morphology characterization of post-consumer HDPE/PP blends (100/0, 75/25, and 0/100 wt.%) in different proportions of TPS (30%, 40% and 50% wt.%) by melting flow index (MFI), tensile property measurements, and scanning electron microscopy (SEM), respectively. The addition of TPS reduced the MFI of PP and increased of HDPE and HDPE/PP blends. TPS also decreased the tensile strength and elongation at break, and increased the rigidity of the materials. SEM showed separation of phase between the poliolefins and TPS.     

聚乙烯/废天然橡胶的老化和力学性能研究

通过汞灯辐射试验对制备的聚乙烯/废天然橡胶共混物进行了紫外老化试验,研究了防老剂4010对聚乙烯/废天然橡胶的紫外老化性能的影响。结果表明:老化初期聚乙烯/废天然橡胶(60/40)的拉伸强度提高,老化中后期聚乙烯/废天然橡胶拉伸强度下降。防老剂4010的加入提高了聚乙烯/废天然橡胶的紫外老化性能。     

Effect of stabilizer on the mechanical,morphological and thermal properties of compatibilized high density polyethylene/ethylene vinyl acetate copolymer/organoclay nanocomposites

In this work, the effects of a phosphate containing stabilizer on the mechanical, morphological and thermal properties of a compatibilized high density polyethylene (HDPE)/ethylene vinyl acetate (EVA) blend containing an ammonium quaternary salts modified montmorillonite were studied from both statistical and experimental aspects. According to the results obtained from simultaneous implementation of analysis of variance (ANOVA) and mean effect assessment, the formulations designed based on the optimized coupling of stabilizer into organoclay/compatibilizer system exhibited the highest tensile properties among the prepared samples. From experimental point of view, the d-spacing measurements and microscopy observations through X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively, revealed that the stabilizer not only favored the penetration of the polymeric chains between the silicate layers but also contributed to provide finer dispersion of the minor phase in the matrix. Thermal characterizations using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed that the stabilizer could play a role in prevention of the organic modifier of the nanoclay to undergo thermo-oxidative degradation by hindering the SN₂ nucleophilic substitution reactions between alkyl ammonium chains and oxygen molecules. This, we believe, is responsible for the properties enhancement, since the protective role of stabilizer might inhibit the formation of destructive degradation products which could collapse the organoclay tactoids and also deactivate the anhydride groups of the compatibilizer.     

Effect of the processing method on the mechanical properties and morphology of compatibilized PA6/LDPE blends

In this work, the effect of the processing method on the mechanical properties and morphology of compatibilized PA6/LDPE blends was investigated. The blends were prepared by two processing methods: Injection and Extrusion followed by Injection. The compatibilizers used were polyethylene grafted with acrylic acid (PEgAA) and polyethylene grafted with maleic anhydride (PEgMA). The results showed that in both processing methods the impact strength and elongation at break of the compatibilized blends were greater than those of the uncompatibilized ones. For the blends prepared by injection, the impact strength of PA6/PEgMA/LDPE blend was greater than that of PA6/PEgAA/LDPE blend. For the blends prepared by extrusion followed by injection, the impact strength of the PA6/PEgAA/LDPE blend was greater than that of PA6/PEgMA/LDPE blend. SEM analysis showed that the morphology of the PA6/PEgAA/LDPE blend prepared by extrusion followed by injection was more stable than that of the same blend prepared only by injection.     

Effect of high density polyethylene addition and testing temperature on the mechanical and morphological properties of polypropylene/ethylene-propylene diene terpolymer binary blends

High density polyethylene (HDPE) was added to the polypropylene (PP)/ethylene-propylene diene terpolymer (EPDM) binary blend, and the effect of testing temperatures on the modulus of elasticity, impact behavior and corresponding fracture morphology was analyzed. Modulus of elasticity generally decreased as the EPDM content increased regardless of the testing temperatures. However, it was found that the modulus of elasticity of PP/EPDM/HDPE ternary blend increased compared to PP/EPDM binary blend when tested at –30 and –60 °C. Notched Izod impact strength changed depending on the testing temperatures, however, there was not much difference between binary and ternary blends up to 20 wt% EPDM. However, at more than 30 wt% EPDM content, ternary blends showed higher impact strength compared to binary blends. Especially, at –30 °C, brittle-ductile transition was observed between 20 and 30 wt% EPDM. Subsurface morphology was also analyzed, and the relationship between the impact strength and the stress whitening zone was investigated. Scanning electron microscopy observation of impact fractured surfaces was conducted, and overall morphology was analyzed with respect to HDPE addition and testing temperature change.     

Electrospun PHBV/PEO co-solution blends: Microstructure,thermal and mechanical properties

Blending allows to tailor and modulate the properties of selected polymers. Blends of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polyethylene oxide (PEO) were fabricated by electrospinning in different weight ratios i.e. 100:0, 80:20, 70:30, 50:50, 0:100.In order to evaluate the influence of PEO addition on the final properties of PHBV, a complete microstructural, thermal and mechanical characterization of PHBV/PEO blends has been performed. The two neat polymeric membranes were also considered for the sake of comparison. The following characterization techniques were employed: scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy, simultaneous thermogravimetric and differential analyses (TG-DTA), differential scanning calorimetry (DSC), and uniaxial tensile tests.All electrospun mats consisted of randomly oriented and uniform fibers. It has been observed that the microstructure of PHBV/PEO was remarkably affected by blend composition. The average fiber size ranged between 0.5 μm and 2.6 μm. It resulted that the electrospun polymeric blends consisted of separate crystalline domains associated to an amorphous interdisperse phase. PHBV/PEO blends presented intermediate mechanical properties, in terms of tensile modulus and ultimate tensile stress, with respect to the two neat components.     

Influence of a fine talc on the properties of composites with high density polyethylene and polyethylene/polystyrene blends

Fine talc filled high density polyethylene (HDPE) and HDPE/polystyrene (PS) blends were extruded, injection moulded and characterized. Some of the mechanical properties of the talc filled HDPE and talc filled 75/25 HDPE/PS blend were deduced from stress–strain measurements. A comparison between the effect of the talc on the properties of the filled HDPE and filled 75/25 HDPE/PS blend showed that the mineral filler had the same effect on both systems provided that its array in the organic matrix is almost the same in both cases. In fact, the rheological results proved that the dispersion of talc in the HDPE matrix was not really affected by the presence of PS. The study particularly focused on the effect of talc on the ultimate tensile strength of the filled HDPE and that of the filled blend. It has been noted that the brittle nature of PS neutralizes, to a certain extent, the degrading effect of talc on this property. Furthermore, both PS and talc have a complementary effect on the stiffness and the resilience of HDPE/PS/talc blend composites.     

Influence of branched or un-branched alkyl substitutes of POSS on morphology,thermal and mechanical properties of polyethylene

Organic–inorganic hybrids comprising octakis(dimethylsiloxy)octasilsesquioxanes with linear (POSSl) and branched C5 substitutes (POSSb) and low density polyethylene (PE) were prepared by a melt mixing method. The influence of both structure and concentration of POSSs on the morphological, thermal and mechanical characteristics of PE/POSSs nanocomposites was investigated. QNM analysis showed a similar distribution of POSS fillers regardless their structure. XRD and DSC results indicated that the addition of POSS does not induce changes in the crystal structure of PE but influences the amorphous peak characteristics and crystallinity degree. TGA analysis revealed that the presence of POSS strongly improves the thermo-oxidative stability of PE, the thermal stabilization effect being nearly the same for both POSS types. Mechanical characterization showed significant improvement of tensile strength and elongation properties of PE/POSS nanocomposites as compared to neat PE, the enhancement of mechanical properties being more pronounced for nanocomposite containing POSSb.     

Effect of different polypropylenes and compatibilizers on the rheological,mechanical and morphological properties of nylon 6/PP blends

In this work, the rheological, mechanical and morphological properties of nylon 6/polypropylene compatibilized blends were investigated. Two types of polypropylene were used. One with MFI of 40 g/10 min (PP H103) and the other with MFI of 3.5 g/10 min (PP H503). The compatibilizers used were polypropylene grafted with 6% of acrylic acid (PPgAA) and polypropylene grafted with 1% of maleic anhydride (PPgMA). The blends composition was 80/20 (wt%) for the PA6/PP binary blends and 80/10/10(wt%) for the nylon 6/PPgAA/polypropylene and nylon 6/PPgMA/polypropylene ternary blends. Torque rheometry analysis showed that when PPgAA and PPgMA were added to nylon 6/polypropylene blends, there was an increase in the torque, indicating that reactive compatibilization has occurred. There is no influence of the polypropylene MFI on the mechanical properties of the uncompatibilized and compatibilized blends. The impact strength of the blends containing PPgMA were greater than those of the blends containing PPgAA. The blends containing PPgAA are unstable. SEM analysis showed that PPgMA improves considerably the adhesion between PA6/PP phases, leading to good mechanical properties.     

On nanoclay localization in polypropylene/poly(ethylene terephthalate) blends: Correlation with thermal and mechanical properties

A series of melt processed clay filled-PP/PET immiscible blends were analyzed in terms of thermal and mechanical properties combined with a theoretical analysis using a mechanical model for probing nanoclay localization in the blends influenced by blend composition, nanoclay content and type of matrix (PET-rich and PP-rich). According to the results obtained from DSC technique, it was shown that localization of nanoclay in the blend systems can be detected by analyzing changes in crystallization temperature and crystallinity of polymer components of the blend systems. From the tensile test results, it was revealed that tensile strength of the blend systems was affected by localization of nanoclay in the matrix phase, only. There was observed no compatibilization effect of nanoclay localized at interface of the blends, on mechanical properties improvement. Also, it was revealed that localization of nanoclay particles in matrix phase resulted in their more efficiency to increase tensile modulus than that localized in disperse phase. However, this efficiency was still dramatically low as compared to that predicted by Hui–Shia model.     

Influence of processing conditions on rheological and mechanical properties of polycarbonate/polypropylene blends

Rheological and mechanical data on polycarbonate/polypropylene blends are reported as a function of the blend preparation. Both kinds of properties depend on the properties of the homopolymers and on the processing conditions. In the molten state the blends are compatible at low content of polypropylene and incompatible at high content. The blends with intermediate compositions can be called semicompatible. Also in the solid state the blends with low content of polypropylene are compatible, while all other blends are incompatible.     

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and wheat straw fibre composites: thermal, mechanical properties and biodegradation behaviour

The thermal and mechanical behaviour of a biotechnological polyester (poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) reinforced with wheat straw fibres has been investigated. In order to improve chemico-physical interactions between the components, the reinforcing agent has been previously submitted to a treatment with high temperature steam leading to fibres richer in cellulose and more reactive. The addition of straw fibres has been found to increase the rate of PHBV crystallisation, while it does not affect the crystallinity content. Furthermore, the comparison of the mechanical properties has shown that the composites exhibit higher Young moduli and lower values of both the stress (_B) and strain (_B) to break than the neat matrix of PHBV. The biodegradability in different environments by means of short and long term tests has been studied. It has been observed that the presence of straw does not affect biodegradation rate evaluated in liquid environment and in long term soil burial tests. In the composting simulation test the rate of biodegradation is reduced for composites with more than 10% of straw content. The morphology of the composites has also been investigated and correlated to the biodegradation process.     

Latex derived blends of poly(vinyl acetate) and natural rubber: thermal and mechanical properties

Poly(vinyl acetate) (PVAc) and natural rubber blends (NR) were prepared by low shear blending of the corresponding lattices. Thin films were cast using a doctor blade technique. SEM and DMA confirmed the essential immiscibility of the two polymers. Even when the poly(vinyl acetate) forms the matrix phase, it still contains domains encapsulated by a rubber phase where particles that resemble the original latex are visible. This incomplete droplet coalescence of the poly(vinyl acetate) is attributed to the fact that the rubber latex droplets were an order of magnitude smaller than the poly(vinyl acetate) latex droplets. Tensile testing revealed a nonlinear dependence of tensile strength and elongation on blend composition. Surprisingly good tensile yield strengths were obtained at intermediate to high PVAc contents. Thermogravimetric analysis of degradation in air and nitrogen atmospheres indicated independent degradation of the parent polymers.     

Influence of physico-chemical,mechanical and morphological fingerpad properties on the frictional distinction of sticky/slippery surfaces

This study investigates how the fingerpad hydrolipid film, shape, roughness and rigidity influence the friction when it rubs surfaces situated in the slippery psychophysical dimension. The studied counterparts comprised two ‘real’ (physical) surfaces and two ‘virtual’ surfaces. The latter were simulated with a tactile stimulator named STIMTAC. Thirteen women and 13 men rubbed their right forefingers against the different surfaces as their arms were displaced by a DC motor providing constant velocity and sliding distance. Tangential and normal forces were measured with a specific tribometer. The fingerpad hydrolipid film was characterized by Fourier transform infrared spectroscopy. The shape and roughness of fingers were extrapolated from replicas. Indentation measurements were carried out to determine fingerpad effective elastic modulus. A clear difference was observed between women and men in terms of friction behaviour. The concept of tactile frictional contrast (TFC) which was introduced quantifies an individual''s propensity to distinguish two surfaces frictionally. The lipids/water ratio and water amount on the finger skin significantly influenced the TFC. A correlation was observed between the TFC and fingerpad roughness, i.e. the height of the fingerpad ridges. This is essentially owing to gender differences. A significant difference between men''s and women''s finger topography was also noted, because our results suggested that men have rougher fingers than women. The friction measurements did not correlate with the fingerpad curvature nor with the epidermal ridges'' spatial period.     

Effect of ion bombardment on the optical properties of LDPE/EPDM polymer blends

Ion bombardment is a suitable tool to improve the physical properties of polymers. In the present study, the effect of ion bombardment on the optical properties of low density polyethylene (LDPE)/Ethylene propylene diene monomer (EPDM) blend (LDPE/EPDM) was studied. Polymer samples was bombarded with 130 keV He and 320 keV Ar ions at fluencies levels ranging from 1 × 10¹³ to 2 × 10¹⁶ ions/cm². The untreated and ion beam bombarded samples were investigated using ultraviolet-visible (UV-Vis) spectrophotometry. The optical band gap (E_g), was decreased from ∼2.9 eV for the pristine sample down to 1.7 eV for the samples bombarded with He and Ar ions at the highest fluences. Change in the optical gap indicates the presence of a gradual phase transition for the polymer blends. Activation energy has been investigated as a function of the ion fluences. With increasing ion fluence, a decrease in both the energy gap and the activation energy was observed. The number of carbon atoms (N) in a formed cluster is determined according to the modified Tauc's equation.