Phase segregation behavior in PE/DOP blends and glass‐transition temperatures of polyethylene

Phase segregation behavior in PEs/DOP blends, interactions between PEs and DOP, and glass‐relaxation transitions of PEs were investigated. FTIR, DSC, and TGA data demonstrated that molecular interactions were present between PEs and DOP. DMA data demonstrated that pure PEs each (except HDPE) exhibited two loss maxima at about ?20 and ?120°C but the PEs/DOP blends (including the HDPE/DOP blend) yielded one new loss maximum at about ?60°C. The glass‐relaxation transitions corresponding to the three loss maxima on the DMA curves were designated α (?20°C), β (?60°C), and γ (?120°C) transitions and were attributed to the relaxation of the amorphous phases in the interlamellar, interfibrillar, and interspherulitic regions, respectively, based on DMA, WAXD, SAXS, and POM measurements. The controversial T_g values of PEs and their origin were thus clarified in this study. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3591–3601, 2001     

High‐density polyethylene/cycloolefin copolymer blends. Part 1: Phase structure,dynamic mechanical,tensile, and impact properties

High‐density polyethylene (HDPE) was blended with “reinforcing” cycloolefin copolymer (COC) in order to produce polyolefin materials with increased stiffness, yield and tensile strength. Experimental data on tensile modulus E_b, creep modulus E_bcr, storage modulus E_b′, loss modulus E_b″, yield strength S_yb, and tensile strength S_ub of blends are in plausible accord with their simultaneous prediction based on a predictive format that operates with a two‐parameter equivalent box model and the data on the phase continuity of components obtained from modified equations of the percolation theory. Dependencies of these mechanical properties on blend composition indicate the critical volume fraction v_2cr = 0.16 of COC. Interfacial adhesion in the HDPE/COC blends is strong enough to transmit acting stress up to the break point. Strain at break, tensile energy to break and tensile impact strength show conspicuous drops in the interval 15–25% of COC in the blends, during which COC starts to form a co‐continuous brittle component. Further growth of COC fraction accounts for reduction of blend ultimate properties to values typical of brittle polymers. However, tensile impact strength shows a local maximum at HDPE/COC = 25/75, which probably corresponds to COC toughened with HDPE particles. POLYM. ENG. SCI. 45:817–826, 2005. © 2005 Society of Plastics Engineers     

Compatibilization effects of block copolymers in high density polyethylene/syndiotactic polystyrene blends

Three triblock copolymers of poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) of different molecular weights and one diblock copolymer of poly[styrene-b-(ethylene-co-butylene)] (SEB) were used to compatibilize high density polyethylene/syndiotactic polystyrene (HDPE/sPS, 80/20) blend. Morphology observation showed that phase size of the dispersed sPS particles was significantly reduced on addition of all the four copolymers and the interfacial adhesion between the two phases was dramatically enhanced. Tensile strength of the blends increased at lower copolymer content but decreased with increasing copolymer content. The elongation at break of the blends improved and sharply increased with increments of the copolymers. Drop in modulus of the blend was observed on addition of the rubbery copolymers. The mechanical performance of the modified blends is strikingly dependent not only on the interfacial activity of the copolymers but also on the mechanical properties of the copolymers, particularly at the high copolymer concentration. Addition of compatibilizers to HDPE/sPS blend resulted in a significant reduction in crystallinity of both HDPE and sPS. Measurements of Vicat softening temperature of the HDPE/sPS blends show that heat resistance of HDPE is greatly improved upon incorporation of 20 wt% sPS.     

Polyethylene toughened by caco3 particles—percolation model of brittle-ductile transition in hdpe/caco3 blends

The percolation model is used to interpret the brittle-ductile transition of HDPE/CaCO₃ blends. The percolation threshold (θ_sc) for HDPE/CaCO₃ blends is found to be 0.52, which is equal to π/6. The critical exponent (g) is found to be 0.83 for HDPE/CaCO₃ blends. The toughening efficiency of blends which have monodisperse, highly asymmetrical particles, strong interphase adhesion and high matrix toughness is greater. The brittle-ductile transition in polymer blends seems to be a universal percolation phenomenon.     

Viscoelastic,thermal, and morphological analysis of HDPE/EVA/CaCO<Subscript>3</Subscript> ternary blends

High density polyethylene (HDPE), calcium carbonate (CaCO₃), and ethylene vinyl acetate (EVA) ternary reinforced blends were prepared by melt blend technique using a twin screw extruder. The thermal properties of these prepared ternary blends were investigated by differential scanning calorimetry. The effect of EVA loading on the melting temperature (T _m) and the crystallization temperature (T _C) was evaluated. It was found that the expected heterogeneous nucleating effect of CaCO₃ was hindered due to the presence of EVA. The melt viscosities of the ternary reinforced blends were affected by the % loading of CaCO₃, EVA, and vinyl acetate content. Viscoelastic analysis showed that there is a reduction of the storage modulus (G′) with increasing of EVA loading as compared to neat HDPE resin or to HDPE/CACO₃ blends only. The morphology of the composites was characterized by scanning electron microscopy (SEM). The dispersion and interfacial interaction between CaCO₃ with EVA and HDPE matrix were also investigated by SEM. We observed two main types of phase structures; encapsulation of the CaCO₃ by EVA and separate dispersion of the phases. Other properties of ternary HDPE/CaCO₃/EVA reinforced blends were investigated as well using thermal, rheological, and viscoelastic techniques.     

Effect of confinement on glass dynamics and free volume in immiscible polystyrene/high‐density polyethylene blends

The effect of confinement on glass dynamics combined with the corresponding free volume changes of amorphous polystyrene (PS) in blends with semi‐crystalline high‐density polyethylene (HDPE) have been investigated using thermal analyses and positron annihilation lifetime spectroscopy (PALS). Two different glass transition temperatures (T_g) were observed in a PS/HDPE blend due to the dissimilarity in the chemical structure, consistent with an immiscible blend. However, T_g of PS in the incompatible PS/HDPE blend showed an upward trend with increasing PS content resulting from the confinement effect, while T_g of the semi‐crystalline HDPE component became lower than that of neat HDPE. Moreover, the elevation of T_g of PS was enhanced with a decrease of free volume radius by comparing annealed and unannealed PS/HDPE blends. Positron results showed that the free volume radius clearly decreased with annealing for all compositions, although the free volume hole size agreed well with linear additivity, indicating that there was only a weak interaction between the two components. Combining PALS with thermal analysis results, the confinement effect on the glass dynamics and free volume of PS phase in PS/HDPE blends could be attributed to the shrinkage of HDPE during crystallization when HDPE acted as the continuous phase. © 2015 Society of Chemical Industry     

The flame retardant and smoke suppression effect of fullerene by trapping radicals in decabromodiphenyl oxide/Sb2O3 flame‐retarded high density polyethylene

To improve the large release of smoke and heat for brominated flame retardants (BFRs) in fire hazard, fullerene (C₆₀) had been introduced in high density polyethylene (HDPE)/bromine flame retardant (Deca/Sb₂O₃, BFR in short) system in this study. The effects of C₆₀ on the thermal properties, flame retardant properties, rheological behaviors, and smoke release behaviors in HDPE/BFR blends were researched. During polymer thermal degradation, C₆₀ and BFR exhibited the trapping radical ability in condensed phase and gaseous phase, respectively. The intergrated effects of C₆₀ and BFR on the thermal stability and flammability of HDPE were studied by thermo‐gravimetry and cone calorimeter. It was indicated that the introduction of C₆₀ improved the thermal and thermo‐oxidative stability of HDPE/BFR blends. A remarkable advantage of adding C₆₀ was to reduce the peak heat release rate and the average specific extinction area, especially at higher concentration of C₆₀. The analysis of rheological behaviors and pyrolysis products revealed that C₆₀ can capture alkyl radicals, chain radicals, and bromine radicals in the condensed phase, which was in favor of terminating the thermo‐oxidative decomposition and inhibiting the heat and smoke release of HDPE/BFR blends during combustion.     

Phase structure and properties of poly(ethylene terephthalate)/high‐density polyethylene based on recycled materials

Blends based on recycled high density polyethylene (R‐HDPE) and recycled poly(ethylene terephthalate) (R‐PET) were made through reactive extrusion. The effects of maleated polyethylene (PE‐g‐MA), triblock copolymer of styrene and ethylene/butylene (SEBS), and 4,4′‐methylenedi(phenyl isocyanate) (MDI) on blend properties were studied. The 2% PE‐g‐MA improved the compatibility of R‐HDPE and R‐PET in all blends toughened by SEBS. For the R‐HDPE/R‐PET (70/30 w/w) blend toughened by SEBS, the dispersed PET domain size was significantly reduced with use of 2% PE‐g‐MA, and the impact strength of the resultant blend doubled. For blends with R‐PET matrix, all strengths were improved by adding MDI through extending the PET molecular chains. The crystalline behaviors of R‐HDPE and R‐PET in one‐phase rich systems influenced each other. The addition of PE‐g‐MA and SEBS consistently reduced the crystalline level (χ_c) of either the R‐PET or the R‐HDPE phase and lowered the crystallization peak temperature (T_c) of R‐PET. Further addition of MDI did not influence R‐HDPE crystallization behavior but lowered the χ_c of R‐PET in R‐PET rich blends. The thermal stability of R‐HDPE/R‐PET 70/30 and 50/50 (w/w) blends were improved by chain‐extension when 0.5% MDI was added. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Liquid-liquid phase separation in a polyethylene blend monitored by crystallization kinetics and crystal-decorated phase morphologies

A series of polyethylene (PE) blends consisting of a linear high density polyethylene (HDPE) and a linear low density polyethylene (LLDPE) with an octane-chain branch density of 120/1000 carbon was prepared at different concentrations. The two components of this set of blends possessed isorefractive indices, thus, making it difficult to detect their liquid-liquid phase separation via scattering techniques. Above the experimentally observed melting temperature of HDPE, T_m = 133 °C, this series of blends can be considered to be in the liquid state. The LLDPE crystallization temperature was below 50 °C; therefore, above 80 °C and below the melting temperature of HDPE, a series of crystalline-amorphous PE blends could be created. A specifically designed two-step isothermal experimental procedure was utilized to monitor the liquid-liquid phase separation of this set of blends. The first step was to quench the system from temperatures of known miscibility and isothermally anneal them at a temperature higher than the equilibrium melting temperature of the HDPE for the purpose of allowing the phase morphology to develop from liquid-liquid phase separation. The second step was to quench the system to a temperature at which the HDPE could rapidly crystallize. The time for developing 50% of the total crystallinity (t_1/2) was used to monitor the crystallization kinetics. Because phase separation results in HDPE-rich domains where the crystallization rates are increased, this technique provided an experimental measure to identify the binodal curve of the liquid-liquid phase separation for the system indicated by faster t_1/2. The annealing temperature in the first step that exhibits an onset of the decrease in t_1/2 is the temperature of the binodal point for that blend composition. In addition, the HDPE-rich domains crystallized to form spherulites which decorate the phase-separated morphology. Therefore, the crystal dispersion indicates whether the phase separation followed a nucleation-and-growth process or a spinodal decomposition process. These crystal-decorated morphologies enabled the spinodal curve to be experimentally determined for the first time in this set of blends.     

Study of the effect of branch content of octene‐based linear low‐density polyethylene on its melt miscibility with high‐density polyethylene by inverse gas chromatography

Inverse gas chromatography was used to measure Flory–Huggins interaction parameters (χ₂₃) for five binary blends consisting of high‐density polyethylene (HDPE) and octene‐based linear low‐density polyethylene (LLDPE) with different compositions at four elevated temperatures. The branch content of the LLDPE used in each pair of the blends ranged from 2 to 87 branches per 1000 backbone carbons. To obtain solvent‐independent χ₂₃, the data analysis approach recently proposed by Zhao and Choi (Polymer 2001, 42, 1075) was used. The results indicate that the higher the branch content of LLDPE, the higher the measured χ₂₃, signifying that HDPE/LLDPE blends with low branch content LLDPEs are relatively more miscible than those with high branch contents. In particular, when the branch content of LLDPE is higher than 50 branches per 1000 backbone carbons, phase separation may occur. This result is in good agreement with other researchers' results obtained from different techniques. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1927–1931, 2004     

Effect of addition of oligobetapinene on morphology,thermal and gas permeation properties in blends with HDPE

Binary blends of high density polyethylene (HDPE) and oligobetapinene (OBP) were prepared by melt mixing. The morphology, thermal and permeability properties of compression molded and slow cooled films are reported. Applying the first‐derivative procedure on differential scanning calorimetry (DSC) traces, we have detected the temperature of glass transition (T_g) of HDPE as a large peak centered from ?125 to ?100°C. In the blends, we observed that the OBP molecules were able to resolve the transition into two components. The lower one was ascribed to the γ‐transition of HDPE, and the upper one was attributed to its T_g. The OBP molecules also formed another transition at a higher temperature. The blends were composed at least of three distinct phases, likely composed of amorphous HDPE with some amount of OBP molecules, amorphous OBP with some polyolefin and crystalline HDPE. The scanning electron microscopy (SEM) investigations revealed segregation of the components. The permeation to CO₂ of plain HDPE and 90/10 blends was similar, but at higher concentrations of oligomer, the value was slightly higher than that of neat HDPE. The decrease of overall crystallinity was counterbalanced by the presence of an OBP rich phase in the blend and could explain the slight increase in permeability of the film blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 315–320, 2004     

Structure development and property changes in high‐density polyethylene/calcium carbonate blends during pan‐milling

A new self‐designed mechanochemical reactor, inlaid pan‐mill, was used in studying high density polyethylene (HDPE) and calcium carbonate (CaCO₃) blends. The effects of CaCO₃ on the crushing and structure of HDPE matrix and the properties of HDPE/CaCO₃ blends were investigated. Scanning electron microscopy, Fourier transformed IR spectroscopy, dynamical mechanical testing analysis, capillary rheometer, and Instron material testing system were used to characterize the structure of HDPE and evaluate the properties of HDPE/CaCO₃ blends. The introduction of calcium carbonate during milling improved milling efficiency, and time needed for each cycle was greatly reduced. Oxygen‐containing groups on HDPE chains, which were produced during milling, increased interfacial interactions and improved the dispersion and distribution of calcium carbonate particles in HDPE/CaCO₃ blends. Rheological, thermal, and mechanical properties were also improved. The elongation at break of milled blends with high concentrations of calcium carbonate was significantly higher than that of unmilled blends. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1459–1464, 1999     

Polyethylene toughened by CaCO3 particle: Brittle-ductile transition of CaCO3-toughened HDPE

The dependencies of the notched Izod impact toughness of HDPE / CaCO₃ blends on CaCO₃ particle concentration and particle size are analyzed. It was found that the notched Izod impact strength (S) of HDPE / CaCO₃ blends depends discontinuously on CaCO₃ particle concentration. A brittle-ductile transition occurs when the CaCO₃ volume fraction (V_f) increases to a critical value (Vη_f). Furthermore, a brittle-ductile transition master curve can be constructed by taking the matrix ligament thickness (L) into account as a parameter instead of V_f. The results show that the critical matrix ligament thickness (L_c) is a single parameter for the transition and L_c = 5.2μm for HDPE / CaCO₃ blends. The impact strength, however, varies considerably with CaCO₃ particle size, which shows that CaCO₃ particle size is another dominating parametor for the toughness of HDPE / CaCO₃ blends. © 1993 John Wiley & Sons, Inc.     

Compatibilization of high‐impact polystyrene/high‐density polyethylene blends by styrene/ethylene–butylene/styrene block copolymer

Compatibilization of polymer blends of high‐impact polystyrene (HIPS) and high‐density polyethylene (HDPE) blend by styrene/ethylene–butylene/styrene (SEBS) was elucidated. Polymer blends containing many ratios of HIPS and HDPE with various concentrations of SEBS were prepared. The Izod impact strength and elongation at break of the blends increased with increases in SEBS content. They increased markedly when the HDPE content was higher than 50 wt %. Tensile strength of blends increased when the SEBS concentration was not higher than 5 pphr. Whenever the SEBS loading was higher than 5 pphr, the tensile strength decreased and a greater decrease was found in blends in which the HDPE concentration was more than 50 wt %. The log additivity rule model was applied to these blends, which showed that the blends containing the HIPS‐rich phase gave higher compatibility at the higher shear rates. Surprisingly, the blends containing the HDPE‐rich phase yielded greater compatibility at the lower shear rates. Morphology observations of the blends indicated better compatibility of the blends with increasing SEBS concentration. The relaxation time (T₂) values from the pulsed NMR measurements revealed that both polymer blends became more compatible when the SEBS concentration was increased. When integrating all the investigations of compatibility compared with the mechanical properties, it is possible to conclude that SEBS promotes a certain level of compatibilization for several ratios of HIPS/HDPE blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 742–755, 2004     

Dynamic mechanical properties and morphology of high‐density polyethylene/CaCO3 blends with and without an impact modifier

Dynamic mechanical analysis and differential scanning calorimetry were used to investigate the relaxations and crystallization of high‐density polyethylene (HDPE) reinforced with calcium carbonate (CaCO₃) particles and an elastomer. Five series of blends were designed and manufactured, including one series of binary blends composed of HDPE and amino acid treated CaCO₃ and four series of ternary blends composed of HDPE, treated or untreated CaCO₃, and a polyolefin elastomer [poly(ethylene‐co‐octene) (POE)] grafted with maleic anhydride. The analysis of the tan δ diagrams indicated that the ternary blends exhibited phase separation. The modulus increased significantly with the CaCO₃ content, and the glass‐transition temperature of POE was the leading parameter that controlled the mechanical properties of the ternary blends. The dynamic mechanical properties and crystallization of the blends were controlled by the synergistic effect of CaCO₃ and maleic anhydride grafted POE, which was favored by the core–shell structure of the inclusions. The treatment of the CaCO₃ filler had little influence on the mechanical properties and morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3907–3914, 2007     

HDPE/ROSIN blends: I-Morphology, thermal and dynamic-mechanical behavior

SUMMARY Morphological and thermal studies on high density polyethylene (HDPE) / glycerol ester of partially hydrogenated rosin (ester gum) blends reveal phase separation. Both thermal and dynamic-mechanical tests showed no shift of the HDPE glass transition temperature while the HDPE α_c transition appeared. The presence of an additional transition was also noticed as the second component increased in blends; this was attributed to a rosin component. The peak ascribed to this transition became broader in blends enriched with oligomer; it moved toward lower temperatures due to the dissolution of low molecular weight HDPE. The melting temperature and crystallinity of HDPE varied slightly with the amount of amorphous oligomeric component in the blends. Received: 7 May 1997/Revised version: 20 March 1998/Accepted: 14 April 1998     

The effect of matrix toughness and dispersed elastomer phase on the brittle-ductile transition in PP/HDPE/SBS blends

In this paper the sbrittle-ductile transition of polypropylene, high density polyethylene, and a styrene-butadiene-styrene triblock copolymer (PP/HDPE/SBS) ternary blends is investigated for fixed compositions and prepared under various conditions. The morphology of the SBS dispersed phase particles and impact strength of the PP ternary blends is closely related to the processing conditions. There is a sharp Brittle-Ductile transition for the ternary blends when interparticle distance T becomes less than the critical interparticle distance T_c. Both the impact strength in general and more specifically, T_c depend upon the toughness of the PP/HDPE composite matrix.     

Study of the mechanical,thermal, and thermodegradative properties of virgin PP with recycled and non-recycled HDPE

In order to show the significance of plastic recycling, a study of the properties of blends of PP with non-recycled and recycled high density polyethylene (HDPE) is made. The results of the Young's modulus for polypropylene (PP)/non-recycled and recycled HDPE blends present a slight synergism, although no significant dependence of this property on the compound was observed. The values of elongation at break and impact strength reflect the incompatibility of the blends. In thermal studies of the blends, the values of fusion enthalpy are below the values of the components. The results of the thermodegradative studies show that activation energies (E_a) obtained are lower, in the case of the blends, than the E_a corresponding to pure polymers. In PP/recycled HDPE blends, activation energy, at 5% to 20% concentration, is maintained and falls abruptly with an increase in the concentration of the recycled material. Based upon the facts previously exposed, it is possible to recycle the recycled HDPE up to 20% concentration, in PP blends. The addition of the compatibilizer at 5% represents the optimal concentration for improving the final properties of the finished product.     

Thermal behavior and properties of polystyrene/poly(methyl methacrylate) blends

The thermal behavior and properties of immiscible blends of polystyrene (PS) and poly(methyl methacrylate) (PMMA) with and without PS‐b‐PMMA diblock copolymer at different melt blending times were investigated by use of a differential scanning calorimeter. The weight fraction of PS in the blends ranged from 0.1 to 0.9. From the measured glass transition temperature (T_g) and specific heat increment (ΔC_p) at the T_g, the PMMA appeared to dissolve more in the PS phase than did the PS in the PMMA phase. The addition of a PS‐b‐PMMA diblock copolymer in the PS/PMMA blends slightly promoted the solubility of the PMMA in the PS and increased the interfacial adhesion between PS and PMMA phases during processing. The thermogravimetric analysis (TGA) showed that the presence of the PS‐b‐PMMA diblock copolymer in the PS/PMMA blends afforded protection against thermal degradation and improved their thermal stability. Also, it was found that the PS was more stable against thermal degradation than that of the PMMA over the entire heating range. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 609–620, 2004     

Studies on binary and ternary blends of polypropylene with SEBS,PS, and HDPE. II. Tensile and impact properties

Studies are reported on tensile and impact properties of several binary and ternary blends of polypropylene (PP), styrene-b-ethylene-co-butylene-b-styrene triblock copolymer (SEBS), high-density polyethylene (HDPE), and polystyrene (PS). The blend compositions of the binary blends PP/X were 10 wt % X and 90 wt % PP, while those of the ternary blends PP/X/Y were 10 wt % of X and 90 wt % of PP/Y, or 10 wt % Y and 90 wt % PP/X (PP/Y and PP/X were of identical composition 90:10); X, Y being SEBS, HDPE, or PS. The results are interpreted for the effect of each individual component by comparing the binary blends with the reference system PP, and the ternary blends with the respective binary blends as the reference systems. The ternary blend PP/SEBS/HDPE showed properties distinctly superior to those of PP/SEBS/PS or the binary blends PP/SEBS and PP/HDPE. Differences in the tensile yield behavior of the different samples and their correlation with impact strength suggested shear yielding as the possible mechanism of enhancement of impact strength. Scanning electron microscopic study of the impact fractured surfaces also supports the shear yielding mechanism of impact toughening of these blends.