Biodegradability and degrading microbes of low‐density polyethylene

This article is intended to establish a comprehensive interpretation of the noticeable differences in the dynamic mechanical behaviors of polypropylene/talc composites with and without modified interphases. The latter are discussed on the basis of different surface treatments applied to the reinforcement particles. To this end, a series of 75/25 (w/w) polypropylene/talc composites with and without interfacial modifications from the reinforcement side were evaluated by dynamic mechanical analysis. The proven capability of this technique analysis to follow the transitions and structural and morphological changes in organic polymers, which are largely influenced by the degree of compatibility between the components of heterogeneous materials based on polymers, was used in this study to check and discuss the kinds and efficiencies of different physisorption‐ and chemisorption‐based processes carried out on the surface of talc particles. We tackled this study by embracing the different relaxation phenomena taking place in the polymer matrix. To this end, five different temperature intervals were distinguished according to the relaxation phenomena taking place. Finally, a correlation between the parameters on the microscopic scale and others on the macroscopic scale appeared to emerge. Thus, the interfacial effects caused by the modified reinforcements could be determined by observations on either scale. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of ultrasonic oscillations on processing behavior and mechanical properties of metallocene‐catalyzed linear low‐density polyethylene/low‐density polyethylene blends

The influences of ultrasonic oscillations on rheological behavior and mechanical properties of metallocene‐catalyzed linear low‐density polyethylene (mLLDPE)/low‐density polyethylene (LDPE) blends were investigated. The experimental results showed that the presence of ultrasonic oscillations can increase the extrusion productivity of mLLDPE/LDPE blends and decrease their die pressure and melt viscosity during extrusion. Incorporation of LDPE increases the critical shear rate for sharkskin formation of extrudate, crystallinity, and mechanical properties of mLLDPE. The processing behavior and mechanical properties of mLLDPE/LDPE blends were further improved in the presence of ultrasonic oscillations during extrusion. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2522–2527, 2004     

Melt strength of linear low‐density polyethylene/low‐density polyethylene blends

Linear low‐density polyethylenes and low‐density polyethylenes of various compositions were melt‐blended with a batch mixer. The blends were characterized by their melt strengths and other rheological properties. A simple method for measuring melt strength is presented. The melt strength of a blend may vary according to the additive rule or deviate from the additive rule by showing a synergistic or antagonistic effect. This article reports our investigation of the parameters controlling variations of the melt strength of a blend. The reciprocal of the melt strength of a blend correlates well with the reciprocal of the zero‐shear viscosity and the reciprocal of the relaxation time of the melt. An empirical equation relating the maximum increment (or decrement) of the melt strength to the melt indices of the blend components is proposed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1408–1418, 2002     

Moisture‐sorption characteristics of starch/low‐density polyethylene films

Moisture‐sorption characteristics of starch/low‐density polyethylene (LDPE) blends were carried out at 27°C for water activity (a_w) from 0.1 to 0.9. The sorption data were used to fit six different sorption isotherm models proposed in the literature. The model constants were determined by linear fitting of the sorption equations. The ranges of applicability of water activity for the isotherm models reported in the article lies between 0.1 and 0.4 (monomolecular layer) for the BET model and between 0.3 and 0.9 (multimolecular and capillary condensation layers) for other models. The value of the coefficient of determination (R² = 0.97 ± 0.02) confirms the linear fitting of the equations studied. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1193–1202, 2002; DOI 10.1002/app.10417     

Thermal fractionation and crystallization enhancement of silane‐grafted water‐crosslinked low‐density polyethylene

Thermal fractionations performed using differential scanning calorimetry (DSC) to characterize the heterogeneities in molecular structures of low‐density polyethylene (LDPE), silane‐grafted LDPE (G‐LDPE), and silane‐grafted water‐crosslinked LDPE with gel fractions of 30 and 70 wt % are reported. In regular DSC analyses, LDPE, G‐LDPE, and the low gel fraction of crosslinked samples (30 wt %) give one broad endothermic peak at ～110 °C, whereas the high gel fraction of crosslinked samples (70 wt %) give overlapped multiple endothermic peaks in a much broader temperature range. After thermally fractionated in the range 60–145 °C, LDPE, G‐LDPE, and the low gel fraction samples give five to six endothermic peaks in the low‐temperature range, whereas the high gel fraction samples give nine peaks, with three additional peaks appearing in the high‐temperature range. These multiple peaks correspond to fractions of different molecular structures, with the additional peaks for the high gel fraction samples corresponding to the fraction of molecular segments with low or no branching. This fraction of molecular segments is increasingly extruded out of the gel region with increasing gel fraction by crosslinking and leads to an enhancement of crystallization of the sample. This crystallization enhancement behavior is also demonstrated by the X‐ray diffraction data and polarized optical micrographs. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 591–599, 2001     

Thermal analysis of high‐density polyethylene and low‐density polyethylene with enhanced biodegradability

The thermal properties of high‐density polyethylene (HDPE) and low‐density polyethylene (LDPE) filled with different biodegradable additives (Mater‐Bi AF05H, Cornplast, and Bioefect 72000) were investigated with thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The DSC traces of the additives indicated that they did not undergo any significant phase change or transition in the temperature region typically encountered by a commercial composting system. The TGA results showed that the presence of the additive led to a thermally less stable matrix and higher residue percentages. The products obtained during the thermodegradation of these degradable polyolefins were similar to those from pure polyethylenes. The LDPE blends were thermally less stable than the HDPE blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 764–772, 2002     

Thermal and mechanical properties of linear low‐density polyethylene/low‐density polyethylene/wax ternary blends

The thermal and mechanical properties of uncrosslinked three‐component blends of linear low‐density polyethylene (LLDPE), low‐density polyethylene (LDPE), and a hard, paraffinic Fischer–Tropsch wax were investigated. A decrease in the total crystallinity with an increase in both LDPE and wax contents was observed. It was also observed that experimental enthalpy values of LLDPE in the blends were generally higher than the theoretically expected values, whereas in the case of LDPE the theoretically expected values were higher than the experimental values. In the presence of higher wax content there was a good correlation between experimental and theoretically expected enthalpy values. The DSC results showed changes in peak temperature of melting, as well as peak width, with changing blend composition. Most of these changes are explained in terms of the preferred cocrystallization of wax with LLDPE. Young's modulus, yield stress, and stress at break decreased with increasing LDPE content, whereas elongation at yield increased. This is in line with the decreasing crystallinity and increasing amorphous content expected with increasing LDPE content. Deviations from this behavior for samples containing 10% wax and relatively low LDPE contents are explained in terms of lower tie chain fractions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1748–1755, 2005     

Structure and properties of polyamide 6 blends with low‐density polyethylene grafted by itaconic acid and with neutralized carboxyl groups

A comparative study of the structure and properties of two‐phase blends of polyamide 6 (PA6) and low‐density polyethylene (LDPE) modified in the course of reactive extrusion, by grafting of itaconic acid (IA) without neutralization of carboxyl groups (LDPE‐g‐IA) and with neutralized carboxyl groups (LDPE‐g‐IA^?M⁺) was carried out. It was shown that 30 wt % of LDPE‐g‐IA^?M⁺ introduced to PA6 resulted in blends of higher Charpy impact strength compared with that of PA6/LDPE‐g‐IA blends. The maximum increase was achieved when Mg(OH)₂ was used as a neutralizing agent. The blend morphology has a two‐phase structure with blurred interphases because of increased adhesion between the phases. The neutralization of carboxyl groups in grafted IA did not lead to two‐phase morphology of blends, which had a negative influence on the mechanical properties. It is believed that the differences in the impact strength were caused by the influence of the added neutralizing agents on the structure of interphases, which depends on both the interfaces adhesion and structural effects resulting from the nucleating behavior of the neutralizing agent. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1702–1708, 2004     

Evaluation of the thermal and mechanical properties of poly(ε‐caprolactone), low‐density polyethylene,and their blends

The thermal and mechanical properties of low‐density polyethylene (LDPE), poly(ε‐caprolactone) (PCL), and their blends were evaluated. Differential scanning calorimetry showed that increasing the PCL content of the blend did not change the LDPE melting temperature, but reduced the crystallinity by up to 16.8%. This behavior was related to interactions between the PCL chains and the crystalline phase of LDPE. Tensile strength and elongation at break values for the blends were lower than those for the pure polymers, which suggested an incompatibility between the polymers. The values for Young's modulus under tensile increased when PCL was added to LDPE. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91:3909–3914, 2004     

Preparation and characterization of linear low‐density polyethylene/low‐density polyethylene/TiO2 membranes

Because of their special functions, the application of nanoscale powders has recently attracted both industrial and theoretical interest. In this study, nanoscale TiO₂, which exhibited a special UV absorption and consequent antibacterial function, was added to a low‐density polyethylene/linear low‐density polyethylene hybrid by melt compounding to yield functional composite membranes. TiO₂ exhibited an apparent induced nucleation effect on the crystallization of polyethylene, and the size of the crystallites decreased while the number increaed with the introduction of TiO₂; however, the crystallinity of polyethylene changed little. Also, TiO₂ exhibited an ideal dispersion in the membrane with an average size less than 100 nm, and this excellent dispersion provided the membranes extra UV absorption; moreover, the transparency of the membranes was maintained to satisfy common requirements. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 216–221, 2005     

Effect of diatomite/polyethylene glycol binary processing aids on the rheology of a metallocene linear low‐density polyethylene

Flow performance of metallocene linear low‐density polyethylene (mLLDPE) containing small amounts of polyethylene glycol (PEG) diatomite and diatomite/PEG binary processing aids respectively was investigated. The mLLDPE melt viscosity is increased by the addition of diatomite, but is decreased by addition of PEG or the diatomite/PEG binary processing aids. It was also found that the viscosity reduction of mLLDPE with the addition of diatomite/PEG binary processing aid was significantly greater than that obtained with the addition of only PEG. The flow curves of mLLDPE containing diatomite/PEG binary processing aid show extremely lower value and stronger dependence on shear rate than the others. It is suggested that the rheological improvement of mLLDPE with diatomite/PEG binary processing aids resulted not entirely from the wall slip promoted by PEG; the intrinsic structure may have changed under the application of shear flow. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1546–1552, 2004     

Recycled milk pouch and virgin low‐density polyethylene/linear low‐density polyethylene based coir fiber composites

The viability of the thermomechanical recycling of postconsumer milk pouches [a 50 : 50 low‐density polyethylene/linear low‐density polyethylene (LDPE–LLDPE) blend] and their use as polymeric matrices for coir‐fiber‐reinforced composites were investigated. The mechanical, thermal, morphological, and water absorption properties of recycled milk pouch polymer/coir fiber composites with different treated and untreated fiber contents were evaluated and compared with those of virgin LDPE–LLDPE/coir fiber composites. The water absorption of the composites measured at three different temperatures (25, 45, and 75°C) was found to follow Fickian diffusion. The mechanical properties of the composites significantly deteriorated after water absorption. The recycled polymer/coir fiber composites showed inferior mechanical performances and thermooxidative stability (oxidation induction time and oxidation temperature) in comparison with those observed for virgin polymer/fiber composites. However, a small quantity of a coupling agent (2 wt %) significantly improved all the mechanical, thermal, and moisture‐resistance properties of both types of composites. The overall mechanical performances of the composites containing recycled and virgin polymer matrices were correlated by the phase morphology, as observed with scanning electron microscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Surface characterization of low‐temperature cascade arc plasma–treated low‐density polyethylene using contact angle measurements

Low‐density polyethylene (LDPE) was treated with a low‐temperature cascade arc plasma torch (LTCAT) of argon with or without adding a reactive gas of oxygen or water vapor. The static sessile droplet method and the dynamic Wilhelmy balance method were employed to perform surface contact angle measurement in order to investigate and characterize the effects of LTCAT treatment on LDPE surfaces. These treatment effects included changes in surface wettability and surface stability and possible surface damage that would create low‐molecular‐weight oligomers on the treated surface. Experimental results indicated that the combination of static and dynamic surface contact angle measurements enabled a comprehensive investigation of these effects of plasma treatment on a polymer surface. Without the addition of a reactive gas, a 2‐s argon LTCAT treatment of LDPE resulted in a stable hydrophilic surface (with a water contact angle of 40°) and little surface damage. The addition of oxygen into argon LTCAT produced a less stable LDPE surface and showed more surface damage. Adding H₂O vapor into argon LTCAT produced an extremely hydrophilic surface (with a water contact angle < 20°) of LDPE but with pronounced surface damage. When compared with conventional radio frequency (13.56 MHz) plasmas, LTCAT treatment provides a much more rapid, effective, and efficient method of surface modification of LDPE. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2528–2541, 2006     

Compatibility of low‐density polyethylene/poly(ethylene‐co‐vinyl acetate) binary blends prepared by melt mixing

The compatibility of low‐density polyethylene and poly(ethylene‐co‐vinyl acetate) containing 18 wt % vinyl acetate units (EVA‐18) was studied. For this purpose, a series of different blends containing 25, 50, or 75 wt % EVA‐18 were prepared by melt mixing with a single‐screw extruder. For each composition, three different sets of blends were prepared, which corresponded to the three different temperatures used in the metering section and the die of the extruder (140, 160, and 180°C), at a screw rotation speed of 42 rpm. Blends that contained 25 wt % EVA‐18 were also prepared through mixing at 140, 160, or 180°C but at a screw speed of 69 rpm. A study of the blends by differential scanning calorimetry showed that all the prepared blends were heterogeneous, except that containing 75 wt % EVA‐18 and prepared at 180°C. However, because of the high interfacial adhesion, a fine dispersion of the minor component in the polymer matrix was observed for all the studied blends with scanning electron microscopy. The tensile strengths and elongations at break of the blends lay between the corresponding values of the two polymers. The absence of any minimum in the mechanical properties was strong evidence that the two polymers were compatible over the whole range of composition. The thermal shrinkage of the blends at various temperatures depended mainly on the temperature and EVA‐18 content. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 841–852, 2003     

Crosslinking of low‐density polyethylene by diisocyanates for superior barrier properties

The chemical modification of low‐density polyethylene (LDPE) resins with hexamethylene diisocyanate and toluene diisocyanate was achieved. The reaction of LDPE with diisocyanate was monitored by Fourier transform infrared spectroscopy, wherein the appearance of new peaks at 3326, 1620, and 1572 cm^?1 corresponding to ? N? H stretching, ? (C?O)? NH₂ stretching, and ? N? H bending in an amide moiety, respectively, was observed. Modified films of excellent clarity and uniform thickness were obtained by the solution casting of crosslinked polyethylene. The oxygen transmission rate (OTR), water vapor transmission rate (WVTR), grease resistance, and thermal properties of the modified films were studied. The results clearly indicate that the OTR was improved by 35% and that grease resistance was improved by 90–125% in the crosslinked LDPE films with little change in their strengths. The heat seal characteristics, however, showed that relatively higher temperatures were needed to achieve efficient sealing in these films. Differential scanning calorimetry showed a decrease in the melting temperature from 104°C for LDPE to 101°C for both of the crosslinked LDPE films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1193–1199, 2005     

Statistical and kinetic approaches for linear low‐density polyethylene melting modeling

The aim of this study was to compare different models, either originating from literature or originally proposed in this study, for the interpretation of the melting behavior of polymers. In particular, these models, tested with a linear low‐density polyethylene widely used in rotational molding, are suitable for coupling with energy balances in the study of polymer processing. We obtained the experimental data from differential scanning calorimetry (DSC) dynamic scans, assuming that the endothermic flux was related to the rate of melting of the polymer. The studied models were able to predict the broad melting temperature range typically observed during polymer melting with either a statistical or a kinetic approach. The two different approaches were compared with experimental DSC data. The analysis of model performances with complex thermal programs showed that the statistical approach could provide a more realistic representation of polymer melting. These models were particularly suitable in rotational molding, where the lack of any flow and, hence, of any crystalline orientation leads to a degree of melting determined by the actual temperature of the polymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 289–295, 2003     

Investigation of charge transport properties in conducting copolymers of aniline with 3‐aminobenzenesulfonic acid for their applications as antistatic encapsulation materials blended with low‐density polyethylene

The electrostatic charge dissipative (ESD) properties of conducting self‐doped and PTSA-doped copolymers of aniline (AA), o‐methoxyaniline (methoxy AA) and o‐ethoxyaniline (ethoxy AA) with 3‐aminobenzenesulfonic acid (3‐ABSA) blended with low‐density polyethylene (LDPE) were investigated in the presence of external dopant p‐toluenesulfonic acid (PTSA). Blending of copolymers with LDPE was carried out in a twin‐screw extruder by melt blending by loading 1.0 and 2.0 wt% of conducting copolymer in the LDPE matrix. The conductivity of the blown polymers blended with LDPE was in the range 10^?12–10^?6 S cm^?1, showing their potential use as antistatic materials for the encapsulation of electronic equipment. The DC conductivity of all self‐doped homopolymers and PTSA‐doped copolymers was measured in the range 100–373 K. The room temperature conductivity (S cm^?1) of self‐doped copolymers was: poly(3‐ABSA‐co‐AA), 7.73 × 10^?4; poly(3‐ABSA‐co‐methoxy AA), 3.06 × 10^?6; poly(3‐ABSA‐co‐ethoxy AA), 2.99 × 10^?7; and of PTSA‐doped copolymers was: poly(3‐ABSA‐co‐AA), 4.34 × 10^?2; poly(3‐ABSA‐co‐methoxy AA), 9.90 × 10^?5; poly(3‐ABSA‐co‐ethoxy AA), 1.10 × 10^?5. The observed conduction mechanism for all the samples could be explained in terms of Mott's variable range hopping model; however, ESD properties are dependent upon the electrical conductivity. The antistatic decay time is least for the PTSA‐doped poly(3‐ABSA‐co‐AA), which has maximum conductivity among all the samples. © 2013 Society of Chemical Industry     

Process efficiency and long‐term performance of α‐tocopherol in film‐blown linear low‐density polyethylene

α‐Tocopherol was compared with a commercial phenolic antioxidant (Irganox 1076) as a long‐term and process antioxidant in film‐blown and compression‐molded linear low‐density polyethylene. The antioxidant function of α‐tocopherol was high in the film‐blown material, especially in the processing, according to oxygen induction time measurements with differential scanning calorimetry. The residual content of α‐tocopherol after processing, determined with chromatographic techniques, was less than that of the commercial phenolic antioxidant in both the film‐blown and compression‐molded materials. The process stabilizing efficiency was nevertheless higher for the material containing α‐tocopherol. During the long‐term stabilization, the efficiency of α‐tocopherol was less than that of the commercial phenolic stabilizer Irganox 1076 in the thin films, according to chemiluminescence and infrared measurements. The long‐term efficiency in the compression‐molded samples stabilized with α‐tocopherol or Irganox 1076 was equally good because of the low loss of both α‐tocopherol and Irganox 1076 from the thicker films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2427–2439, 2005     

Phase dispersion–crosslinking synergism in binary blends of poly(vinyl chloride) with low‐density polyethylene: Entrapping phenomenon in PVC/LDPE/DCP blend

The co‐crosslinked products and the entrapping phenomenon that may exist in a poly(vinyl chloride)/low density polyethylene/dicumyl peroxide (PVC/LDPE/DCP) blend were investigated. The results of selective extraction show that unextracted PVC was due to not being co‐crosslinked with LDPE but being entrapped by the networks formed by the LDPE phase. SBR, as a solid‐phase dispersant, can promote the perfection of networks of the LDPE phase when it is added to the PVC/LDPE blends together with DCP, which leads to more PVC unextracted and improvement of the mechanical properties of PVC/LDPE blends. Meanwhile, the improvement of the tensile properties is dependent mainly on the properties of the LDPE networks. Finally, the mechanism of phase dispersion–crosslinking synergism is presented. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1296–1303, 2003     

Recent developments in the radiation grafting of N‐vinyl‐2‐pyrrolidone onto low‐density polyethylene with cinnamonitrile derivatives

The radiation‐induced graft polymerization of N‐vinyl‐2‐pyrrolidone onto low‐density polyethylene films was conducted with γ radiation by a simultaneous technique. The grafted copolymer was modified with cinnamonitrile or benzylidene malononitrile. The modified and grafted films were amidoximated with hydroxylamine hydrochloride in a basic medium. However, during amidoximation, the benzylidene malononitrile was cyclized to yield isoxazole ring through an addition to the nitrile group in its structure, whereas the nitrile groups of cinnamonitrile were converted into amidoxime groups. The swelling behavior of the grafted copolymers and copolymers grafted and modified either with cinnamonitrile or benzylidene malononitrile was studied. Amidoximated and grafted films and copolymer–metal complexes of Cu(II) were prepared and characterized. The effect of the isoxazole ring on polymeric materials was also investigated. These films were characterized with different analysis techniques, such as infrared, ultraviolet (UV), elemental analysis, energy‐dispersive spectroscopy, and electron spin resonance (ESR). The UV and ESR analyses revealed that the geometric structure of Cu(II) was square‐planar. Scanning electron microscopy was used to examine the grafted and modified films to determine the changes in the surface morphology. Morphological changes clearly appeared for both complexed and isoxazole films because of the increase in their crystallinity. The thermal stability of different films was investigated with thermogravimetric analysis. The improvement of the copolymer by modification with cinnamonitrile derivatives showed great promise for some practical applications, such as metal recovery by complexation or the use of isoxazole in medicine. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1189–1197, 2005