Flame retardation of dibromoneopentyl glycol on intumescent flame‐retardant/low‐density polyethylene composites

On the basis of ammonium polyphosphate (APP) microencapsulated with pentaerythritol/dibromoneopentyl glycol (DBNPG) mixed phosphate melamine salt as an intumescent flame retardant (IFR), the influence of DBNPG on the flame retardancy of IFR/low‐density polyethylene was investigated. The results prove that DBNPG could influence the combustion heat and the thermal barrier properties of the char layer in combustion. The intumescent degree (ID), compactness, and closure were the determinants of the thermal barrier properties of the char layer. A greater ID below 500°C and then a more compact and closed char layer above 500°C contributed to the better thermal barrier properties. An appropriate DBNPG reduced the combustion heat and promoted the formation of a compact and closed char layer by increasing of the melting viscosity of the composites. However, excessive DBNPG destroyed the closure of the char layer and increased the combustion heat because of a decrease in the melting viscosity of the composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41244.     

A novel intumescent flame‐retardant system for flame‐retarded LLDPE/EVA composites

A new intumescent flame retardant (IFR) system consisting of ammonium polyphosphate (APP) and charing‐foaming agent (CFA) and a little organic montmorillonite (OMMT) was used in low‐density polyethylene (LLDPE)/ethylene‐vinyl acetate (EVA) composite. According to limiting oxygen index (LOI) value and UL‐94 rating obtained from this work, the reasonable mass ratio of APP to CFA was 3 : 1, and OMMT could obviously enhance the flame retardancy of the composites. Cone calorimeter (CONE) and thermogravimetric analysis (TGA) were applied to evaluate the burning behavior and thermal stability of IFR‐LLDPE/EVA (LLDPE/EVA) composites. The results of cone calorimeter showed that heat release rate peak (HRR‐peak) and smoke production rate peak (SPR‐peak) and time to ignition (TTI) of IFR‐LLDPE/EVA composites decreased clearly compared with the pure blend. TGA data showed that IFR could enhance the thermal stability of the composites at high temperature and effectively increase the char residue. The morphological structures of the composites observed by scanning electron microscopy (SEM) and X‐ray diffraction (XRD) demonstrated that OMMT could well disperse in the composites without exfoliation, and obviously improve the compatibility of components of IFR in LLDPE/EVA blend. The morphological structures of char layer obtained from Cone indicated that OMMT make the char layer structure be more homogenous and more stable. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polyphosphazene/low‐density polyethylene blends: Miscibility and flame‐retardance studies

The effect of poly(dianilinephosphazene) (PDAP) on the processability, thermal behavior, crystallinity, morphology, mechanical properties, and flammability behavior of low‐density polyethylene (LDPE) was studied. Plasticorder traces of PDAP/LDPE blends implied good processability and miscibility. Thermogravimetric analysis showed that PDAP improved the thermal stability of LDPE. X‐ray diffraction results indicated that PDAP was a semicrystalline polymer, and the crystallinity of the blends decreased with increasing PDAP content. A new reflection at 2θ = 23.15° was found in wide‐angle X‐ray diffraction spectra of the blends, indicating that these two components interacted with one another. The scanning electron microscopy microstructures of the blends also supported these findings. Moreover, PDAP substantially enhanced the limited oxygen index and elongation at break of LDPE. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 709–714, 2002     

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     

Influence of ultrafine zinc borate on the thermal degradation behavior of a(low‐density polyethylene)/(intumescent flame retardant) system

The thermal degradation behavior of low‐density polyethylene (LDPE), LDPE treated with an intumescent flame retardant (LDPE/IFR), and LDPE treated with an intumescent flame retardant and ultrafine zinc borate (LDPE/IFR/UZB) was studied by (thermal gravimetric)‐(differential thermal) analysis (TG‐DTA) and cone calorimetry. The results of TG‐DTA showed that the initial degradation temperature increased, thermal degradation rate decreased, and the residual char amount increased substantially during the Pyrolysis process when ultrafine zinc borate was introduced into the LDPE/IFR system. The mass‐loss rate (MLR) curves and mass curves obtained by cone calorimetry showed that UZB could decrease the MLR and significantly enhance the residual char amount of LDPE/IFR during the combustion process. The results of Fourier transform infrared spectroscopy implied that a graphite‐like char and aromatic structures containing P‐O‐P, P‐O‐C, and B‐O‐B bonds were formed when LDPE/IFR/UZB was heated at high temperature. Scanning electronic micrographs of residual chars showed that ultrafine zinc borate improved char quality. X‐ray diffraction Studies implied that boron orthophosphate (BPO₄) formed in the residual char may play an important role in improving the structural properties of the char and is responsible for its good quality. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

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     

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     

Synergistic effect of intumescent flame retardant and zinc borate on linear low-density polyethylene

A series of novel intumescent flame retardant (IFR) based on melamine, neopentyl glycol, and aluminum diethylphosphinate were prepared and tested. In addition, the synergistic effect of the novel IFR and zinc borate (ZB) on the flame retardancy of LLDPE composites was investigated. The structures of novel IFR and ZB were characterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The limiting oxygen index (LOI) increased from 19.3% for the pure LLDPE to 27% for the 25 wt% IFR/5 wt% ZB composites and the composites achieved the desired V-0 rating in the UL-94 test. Thermogravimetric analysis showed that the addition of IFR/ZB reduced the pyrolysis rate of the LLDPE composites at high temperatures and increased the amount of the char residues, and the char residue of LLDPE-5 reached 12.1 wt% at 700°C. Cone calorimetry (CCT) data showed that the peak of total heat release, heat release rate, and fire growth index were comparatively reduced, indicating that the addition of IFR/ZB decreased the fire hazard of LLDPE composites. The formation of a compact and thermally stable char layer on the surfaces of LLDPE composites was revealed from the scanning electrone microscopy images and digital photographs of the char residue after the CCT tests.     

Properties of high‐density polyethylene filled with waste crosslinked foam

Crosslinked polyethylene foam is widely used in packaging and as an insulation material. Finely ground waste of such crosslinked foam mesh size 7 or particle size less than 2815 μm is used as a filler in high‐density polyethylene (HDPE) of two different grades (7.5 and 21 MFI). Mechanical, thermal, and morphological properties of filled composites is studied experimentally. Waste foam powder concentration was varied up to 40% by weight basis. Impact strength of base HDPE increased by a factor of six. The overall changes in mechanical properties are similar to the crosslinking effect. It is believed that waste foam particles act as a point of entanglement with different chains of polyethylene. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 110–114, 2004     

Ultraviolet weathering of photostabilized wood‐flour‐filled high‐density polyethylene composites

Wood‐plastic composites are being increasingly examined for nonstructural or semistructural building applications. As outdoor applications become more widespread, durability becomes an issue. Ultraviolet exposure can lead to photodegradation, which results in a change in appearance and/or mechanical properties. Photodegradation can be slowed through the addition of photostabilizers. In this study, we examined the performance of wood flour/high‐density polyethylene composites after accelerated weathering. Two 2⁴ factorial experimental designs were used to determine the effects of two hindered amine light stabilizers, an ultraviolet absorber, a colorant, and their interactions on the photostabilization of high‐density polyethyl‐ ene blends and wood flour/high‐density polyethylene composites. Color change and flexural properties were determined after 250, 500, 1000, and 2000 h of accelerated weathering. The results indicate that both the colorant and ultraviolet absorber were more effective photostabilizers for wood flour/high‐density polyethylene composites than the hindered amine light stabilizers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2609–2617, 2003     

Mechanical properties and water absorption of low‐density polyethylene/sawdust composites

The mechanical properties and water absorption of low‐density polyethylene/sawdust composites were investigated. The relationship between the filler content and the composite properties was also studied. Different degrees of esterification of the sawdust with maleic anhydride were obtained with different reaction times. The experimental results demonstrated that the treatment of sawdust by maleic anhydride enhanced the tensile and flexural strengths. The water absorption for maleic anhydride treated sawdust indicated that it was more hydrophobic than untreated sawdust. The effects of the addition of benzoyl peroxide during the preparation of composite samples on the water absorption and mechanical properties were also evaluated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

Influence of irradiation crosslinking on the self‐heating and conduction of an acetylene carbon black filled high‐density polyethylene composite in the electric–thermal equilibrium state

The electric self‐heating and conduction behaviors of a high‐density polyethylene/acetylene carbon black composite crosslinked with electron‐beam irradiation are studied with respect to the electric field and ambient temperature. On the basis of scaling arguments, the critical fields and current densities for the onsets of self‐heating and global electrical breakdown are discussed with respect to the intrinsic resistivity at a given ambient temperature as well as the irradiation dosage. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Positive temperature coefficient effect and interaction based on low‐density polyethylene/graphite powder composites

In this article, the positive temperature coefficient (PTC) and interaction based on low‐density polyethylene (LDPE) filled with the loading of graphite (G) powder have been investigated. The dependence of the room temperature resistivity on filler content showed the significant decrease. The PTC behavior enhanced with increasing graphite content but this was not always the case. The maximum PTC effect was observed in LDPE/G composites (G, 45 wt %) with the relatively low room temperature resistivity. The thermal behavior was measured by differential scanning calorimetry (DSC). The structure characteristic for LDPE/G composites was examined by X‐ray diffraction (XRD), field‐emission scanning electron microscopy (SEM), and stress–strain test. The fact was revealed that the slight interaction between LDPE matrix and graphite may lead to change the thermal‐electric properties of the PTC materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effects of ultraviolet absorbers on the ultraviolet degradation of rice‐hull/high‐density polyethylene composites

In China, rice‐hull powder is widely used as a fiber component to reinforce polymers because of its ready availability and lower cost compared to wood fibers. However, an issue concerning these composites is their weathering durability. In this study, the effects of two ultraviolet absorbers (UVAs), UV‐326 and UV‐531, on the durability of rice‐hull/high‐density polyethylene (HDPE) composites were evaluated after the samples were exposed to UV‐accelerated weathering tests for up to 2000 h. All of the samples showed significant fading and color changes in exposed areas. X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were used to detect surface chemical changes. The results indicate that surface oxidation commenced immediately within the first 500 h of exposure for all of the samples. However, the control rice‐hull/HDPE composites underwent a greater degree of oxidation than those with the UVAs. Scanning electron microscopy revealed that the rice‐hull/HDPE composites degraded significantly upon accelerated UV aging, with dense cracking on the exposed surface. The UVAs provided effective protection for the rice‐hull/HDPE composites, and UV‐326 had a more positive effect on the color stability than UV‐531. The results reported herein serve to enhance our understanding of the efficiency of UV stabilizers in the protection of rice‐hull/HDPE composites against UV radiation, with a view toward improving their formulation. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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     

Influence of radiation structures on positive‐temperature‐coefficient and negative‐temperature‐coefficient effects of irradiated low‐density polyethylene/carbon black composites

The electrical‐resistivity/temperature behaviors of low‐density polyethylene (LDPE)/carbon black (CB) composites irradiated with ⁶⁰Co γ rays were studied. The experimental results showed that the irradiated composites could be separated into insoluble crosslinking networks with CB (gel) and soluble components (sol) by solvent‐extraction techniques. When the sol of an irradiated LDPE/CB composite was extracted, the electrical conductivity of the system increased. The positive‐temperature‐coefficient (PTC) and negative‐temperature‐coefficient (NTC) intensities of the gels of the irradiated composites became extremely small and independent of the radiation dose. The sols and gels of the irradiated LDPE/CB composites, which had different thermal behaviors, played important roles in the appearances of the PTC and NTC effects. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 700–704, 2005     

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     

Effects of coupling agents on the natural aging behavior and oxidation profile of high‐density polyethylene/sericite composites

The natural photooxidation of high‐density polyethylene (HDPE)/sericite composites was carried out outdoors for 180 days. The oxidative products, oxidation profile, and section morphology were characterized with Fourier transform infrared spectroscopy, infrared microscopy, and scanning electron microscopy, respectively. The results showed that HDPE/sericite had a higher oxidation degree than HDPE. All the coupling agents (CAs) accelerated the oxidation reaction of HDPE and made the final carbonyl index higher than that of an untreated one. The effect of sericite might have been due to the increased ultraviolet absorbance, whereas the effects of CAs might have been due to the active functional groups. Furthermore, cracks in the sections of test bars of HDPE/sericite composites after natural exposure were also observed. Their average lengths and densities were different for various CA treatments. This difference had a direct correspondence with the oxidation profile along the depth. This demonstrated that significant oxidation and consequently chain scission in the surface layer were responsible for the formation of cracks. Comparing the natural aging behavior of the films with test bars, we obtained more information about the propagation of the photooxidation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Time–temperature superposition principle applied to a kenaf‐fiber/high‐density polyethylene composite

The time–temperature superposition principle was applied to the viscoelastic properties of a kenaf‐fiber/high‐density polyethylene (HDPE) composite, and its validity was tested. With a composite of 50% kenaf fibers, 48% HDPE, and 2% compatibilizer, frequency scans from a dynamic mechanical analyzer were performed in the range of 0.1–10 Hz at five different temperatures. Twelve‐minute creep tests were also performed at the same temperatures. Creep data were modeled with a simple two‐parameter power‐law model. Frequency isotherms were shifted horizontally and vertically along the frequency axis, and master curves were constructed. The resulting master curves were compared with an extrapolated creep model and a 24‐h creep test. The results indicated that the composite material was thermorheologically complex, and a single horizontal shift was not adequate to predict the long‐term performance of the material. This information will be useful for the eventual development of an engineering methodology for creep necessary for the design of structural building products from these composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1995–2004, 2005