Graft copolymerization of oleic acid onto low‐density polyethylene in the molten state

A graft copolymer of oleic acid (OA) onto low‐density polyethylene (LDPE) was prepared using dicumyl peroxide (DCP) as an initiator in the molten state. The grafting was carried out in a Haake rheometer. The effects of the reaction time and the amount of DCP and the monomer on the percentage of grafting were studied. The rheological behavior and the melt‐flow rate of the graft copolymer (LDPE‐g‐OA) were also investigated. FTIR spectroscopy and a mass spectrum were used to characterize the structure of LDPE‐g‐OA. The experimental results showed that when the OA amount was 10 wt % and the DCP amount was 0.4 wt % based on the LDPE the percentage of grafting of LDPE‐g‐OA, prepared by maintaining the temperature at 170°C and the roller speed at 80 rpm, was about 6 wt %. It was found that both LDPE and LDPE‐g‐OA were pseudoplastic fluids. OA was grafted onto LDPE in the form of a monomer and a dimer. The grafted LDPE is expected to act as a compatibilizer between starch and polyethylene. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3299–3304, 2003     

Surface modification of low‐density polyethylene films by UV‐induced graft copolymerization with a fluorescent monomer

Surface modification of argon plasma–pretreated low‐density polyethylene (LDPE) film via UV‐induced graft copolymerization with a fluorescent monomer, (pyrenyl)methyl methacrylate (Py)MMA, was carried out. The chemical composition and morphology of the (Py)MMA‐graft‐copolymerized LDPE [(Py)MMA‐g‐LDPE] surfaces were characterized, respectively, by X‐ray photoelectron spectroscopy (XPS) and by atomic force microscopy (AFM). The concentration of the surface‐grafted (Py)MMA polymer increased with Ar plasma pretreatment time and UV graft copolymerization time. The photophysical properties of the (Py)MMA‐g‐LDPE surfaces were measured by fluorescence spectroscopy. After graft copolymerization with the fluorescent monomer, the surface of the LDPE film was found to have incorporated new and unique functionalities. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1526–1534, 2001     

Effects of glycerol and PE‐g‐MA on morphology,thermal and tensile properties of LDPE and rice starch blends

The effects of glycerol and polyethylene‐grafted maleic anhydride (PE‐g‐MA) on the morphology, thermal properties, and tensile properties of low‐density polyethylene (LDPE) and rice starch blends were studied by scanning electron microscopy (SEM), differential scanning calorimetry, and the Instron Universal Testing Machine, respectively. Blends of LDPE/rice starch, LDPE/rice starch/glycerol, and LDPE/rice starch/glycerol/PE‐g‐MA with different starch contents were prepared by using a laboratory scale twin‐screw extruder. The distribution of rice starch in LDPE matrix became homogenous after the addition of glycerol. The interfacial adhesion between rice starch and LDPE was improved by the addition of PE‐g‐MA as demonstrated by SEM. The crystallization temperatures of LDPE/rice starch/glycerol blends and LDPE/rice starch/glycerol/PE‐g‐MA blends were similar to that of pure LDPE but higher than that of LDPE/rice starch blends. Both the tensile strength and the elongation at break followed the order of rice starch/LDPE/glycerol/PE‐g‐MA blends > rice starch/LDPE/glycerol > LDPE/rice starch blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 344–350, 2004     

Reactive extrusion for the synthesis of nylon 12 and maleated low‐density polyethylene blends via the anionic ring‐opening polymerization of lauryllactam

Nylon 12 was successfully synthesized in a twin‐screw extruder via the anionic ring‐opening polymerization of lauryllactam (LL). Maleated low‐density polyethylene (LDPE–MAH) was added to improve the mechanical properties of nylon 12. The in situ blends of nylon 12 and LDPE–MAH were characterized by mechanical testing and scanning electron microscopy. With increasing LDPE–MAH content, the tensile strength and flexural strength decreased, whereas the blend had improved impact strength and achieved supertoughness when the content of LDPE–MAH was 30 wt %. In the in situ formed low‐density polyethylene‐g‐PA12 copolymer, the domain of the LDPE–MAH phase was finely dispersed in the nylon 12 matrix. The good interface between the two phases demonstrated that LDPE–MAH could be used as a macromolecular activator to induce the polymerization of LL. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Novel heterocyclic synthesis and investigation on radiation‐grafted low‐density polyethylene with 2‐N‐vinylpyrrolidone

Radiation‐induced graft polymerization of low‐density polyethylene with N‐vinylpyrrolidone, LDPE‐g‐PNVP, was used as a starting material for the synthesis of polyfunctionally substituted heterocyclic products. Thus, LDPE‐g‐PNVP reacts with ylidenemalononitrile derivatives to give the Michael addition products. In multistep reaction, LDPE‐g‐PNVP reacts with N,N‐dimethylformamide dimethyl acetal (DMFDMA), hydrazine hydrate and malononitrile, respectively, to give a hydropyrrolopyridazine derivative. The latter could also be prepared via the reaction of LDPE‐g‐PNVP with DMFDMA, followed by treating with cyanoacetohydrazide. Also, LDPE‐g‐PNVP reacts with malononitrile to give an adduct product, dimer malononitrile derivative 13. The latter reacts with sulfur element to afford the thiophene derivative. Furthermore, this adduct reacts with hydrazine hydrate to isolate the original starting material, LDPE‐g‐PNVP, and aminopyridine derivative. The resulted films were characterized by infrared (IR) spectroscopy, ¹H nuclear magnetic resonance (¹H‐NMR) mass spectroscopy, elemental analysis, swelling behavior, and electron scanning microscope. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2963–2970, 1999     

Grafting of itaconic acid onto LDPE by the reactive extrusion: Effect of neutralizing agents

Grafting of itaconic acid (IA) onto low‐density polyethylene (LDPE) was performed by reactive extrusion where the initiator was dicumyl peroxide, and the neutralizing agents (NAs) were zinc oxides and hydroxides as well as magnesium oxides and hydroxides. The carboxyl groups were neutralized in molten LDPE directly in the course of acid grafting, and in prefabricated functionalized polyethylene (LDPE‐g‐IA). It was found that neutralizing agents introduced into the initial reaction mixture increase the yield of LDPE‐g‐IA while the carboxyl groups were neutralized partially or totally through chemical reactions. The physical structure of LDPE‐g‐IA did not in fact suffer any substantial changes. From the standpoint of neutralization activity, the NAs studied could be arranged as follows: Zn(OH)₂ > ZnO > Mg(OH)₂ > MgO. NA, added into the initial reaction mixture improved the grafting efficiency of IA onto LDPE. In case of the one‐step process (neutralization simultaneously with grafting), the neutralizing effect appears stronger than that in the two‐step process (neutralization of prepared LDPE‐g‐IA). This means that neutralization of carboxyl groups in IA was less effective when NA was introduced into LDPE‐g‐IA than for the case of the initial reactive mixture. Chemical neutralization of grafted IA results in products of improved resistance to thermal oxidation and thermal stability of melt. This result is of practical importance to the opportunities for widening the application range for PE modified by grafting IA, while preparing polymer blends to be compounded, processed, and used at elevated temperatures. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 828–836, 2003     

The study of melt grafting mechanism of acrylic acid and butyl acrylate onto low density polyethylene and its application as internal plasticizer

Melt grafting of acrylic acid (AA) and butyl acrylate (BA) (equal molar ratios) onto low‐density polyethylene (LDPE) was carried out in Haake internal mixter by free radical grafting copolymerization. The graft degree of AA and BA in the grafted LDPE (LDPE‐g‐(AA+BA)) was determined by FTIR. The influences of initiator on the graft degree of AA and BA, melt flow rate (MFR), and gel content were investigated, and the optimum conditions were obtained. The successive self‐nucleation/annealing (SSA) thermal fraction method was used to characterize the molecular structure and polydispersity of LDPE‐g‐(AA+BA) with various graft degrees. The effects of thermal fraction parameters on fraction of LDPE‐g‐(AA+BA) were investigated. On the basis of the results of SSA, the grafting reaction mechanism of AA and BA onto LDPE was proposed, i.e., grafting reaction preferentially occurred on the tertiary carbons of LDPE. The grafted LDPE possessed suitable reactivity and rheological property. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The effect of matrix composition on the properties of cellulosic fibers–polyethylene composites

The solution/precipitation method was used for the preparation of polyethylene (PE)/cellulosic fibers composites. Blends of modified linear low density PE [linear low density PE‐grafted maleic anhydride (LLDPE‐g‐MAH)] with low density PE (LDPE) were used as matrices for the aforementioned composites. Blends of LDPE with a copolymer of LDPE and acrylic acid (AA)/n‐butyl acrylate (n‐BA) [(AA/n‐BA)–LDPE] were also studied for the same purpose. The reinforcing effect of cellulosic fibers in terms of tensile strength is more enhanced when mixtures of the modified polar polymer with pure PE were used as matrices, as compared with that corresponding to matrices consisting of modified PE alone. Regarding the Izod impact strength, composites of LLDPE‐g‐MAH presented the best performance with an improvement of 135% in comparison with specimens consisting of LDPE matrix, whereas composites of (AA/n‐BA)‐LDPE matrix showed a modest improvement of their impact resistance. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Low‐density polyethylene/plasticized tapioca starch blends with the low‐density polyethylene functionalized with maleate ester: Mechanical and thermal properties

In this study, the mechanical and thermal properties of low‐density polyethylene (LDPE)/thermoplastic tapioca starch blends were determined with LDPE‐g‐dibutyl maleate as the compatibilizer. Mechanical testing for the evaluation of the impact strength and tensile properties was carried our as per standard ASTM methods. Thermogravimetric analysis and differential scanning calorimetry were also used to assess the thermal degradation of the blends. Scanning electron micrographs were used to analyze fracture and blend morphologies. The results show significant improvement in the mechanical properties due to the addition of the compatibilizer, which effectively linked the two immiscible blend components. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1109–1120, 2006     

Efforts to decrease crosslinking extent of polyethylene in a reactive extrusion grafting process

Grafting of acrylic acid and glycidyl methacrylate onto low density polyethylene (LDPE) was performed by using a corotating twin‐screw extruder. The effects of residence time and concentration of initiator and monomers on degree of grafting and gel content of grafting LDPE were studied systematically. Paraffin, styrene, p‐benzoquinone, triphenyl phosphite, tetrachloromethane, and oleic acid were added to try to decrease the extent of crosslinking of LDPE. 4‐hydroxyl‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy (4‐hydroxyl‐TEMPO) and dipentamethylenethiuram tetrasulfide were also tried to inhibit crosslinking reaction of LDPE during its extruding grafting process. It was found that p‐benzoquinone, triphenyl phosphite and tetrachloromethane were good inhibitors for crosslinking of LDPE. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 535–543, 2001     

Soil burial test for poly(ethylene‐co‐vinyl alcohol)‐graft‐polycaprolactone

The ring‐opening polymerization of ε‐caprolactone was carried out with poly(ethylene‐co‐vinyl alcohol) as a macroinitiator to synthesize poly(ethylene‐co‐vinyl alcohol)‐graft‐polycaprolactone (EVOH‐g‐PCL). A simple low‐density polyethylene (LDPE)/polycaprolactone (PCL) (64/36) blend lost 5.3 wt % of its original weight after 90 days of a soil burial test. However, the elongation at break of the LDPE/PCL blend remained almost invariable even after the solid burial test because the tensile properties depended mostly on the LDPE phase on account of the poor interaction between the continuous LDPE matrix and the dispersed PCL phase. For EVOH‐g‐PCL, the elongation at break decreased drastically as a result of the soil burial test, and the reduction of the elongation at break was more pronounced for EVOH‐g‐PCL with a higher PCL concentration, even though the weight loss of EVOH‐g‐PCL after the soil burial test was as low as 1.2–1.3% and was nearly independent of the PCL concentration. Few holes were observed in EVOH‐g‐PCL when the PCL concentration was less than 26 wt % after an accelerated hydrolysis experiment at 60°C for 7 days in a 0.1M KOH solution. In contrast, the hydrolysis formed small holes in EVOH‐g‐PCL with a PCL concentration of 36 wt %. The LDPE/PCL blend was much better percolated, as a result of the hydrolysis, than EVOH‐g‐PCL with the same PCL concentration; the soil burial test showed the same results. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1064–1071, 2005     

Analysis of low‐density polyethylene‐g‐poly(vinyl chloride) copolymers formed in poly(vinyl chloride)/low‐density polyethylene melt blends with gel permeation chromatography and solid‐state 13C‐NMR

Gel permeation chromatography (GPC) and solid‐state ¹³C‐NMR techniques were used to analyze the structural changes of poly(vinyl chloride) (PVC) in blends of a low‐density polyethylene (LDPE) and PVC during melt blending. The GPC results showed that the weight‐average molecular weight (M_w) of PVC increased with LDPE content up to 13.0 wt % and then decreased at a LDPE content of 16.7 wt %, whereas the number‐average molecular weight remained unchanged for all of LDPE contents used. The ¹³C‐NMR results suggest that the increase in M_w was associated with the formation of a LDPE‐g‐PVC structure, resulting from a PVC and LDPE macroradical cross‐recombination reaction during melt blending. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3167–3172, 2004     

Time‐dependent rheological behavior of low‐density polyethylene white color masterbatches under dynamic stress field

The time‐dependent behavior of low‐density polyethylene (LDPE) white color masterbatches (WCMBs), which were concentrated suspensions filled with titanium dioxide (TiO₂), was found using dynamic stress rheometer. The viscosity first decreased slightly with time then continuously increased with time, and T_g(δ) (δ was the angle of loss) decreased with time, which meant the time‐dependent behavior of the elastic contribution was more pronounced than that of the viscous contribution. The higher the experimental frequency and temperature, the more pronounced the viscosity increase. However, the higher experimental stress did not lead to pronounced viscosity increase, which was attributed to the existence of small defects at higher stress. The 30 wt % of TiO₂ content was critical to obvious time‐dependent behavior. The viscosity increase with time was related to the formation of a hard shell around the melt sample during the test. It was verified by thermogravimetric analysis that the TiO₂ concentration at the outer surface was higher than that at the core of the sample and, because the outer surface contained more TiO₂, a hard shell was formed, which impeded further deformation of the sample. This was completely different from the other reported systems with time‐dependent behavior. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2793–2799, 2002     

Effect of the compatibility on dielectric performance and breakdown strength of poly(vinylidene fluoride)/low‐density polyethylene blends

Immiscible polymer blends with high dielectric constant (ε) and improved breakdown strength (E_b) performance were obtained by composing poly(vinylidene fluoride) (PVDF) with low‐density polyethylene (LDPE) or the LDPE grafted with maleic anhydride (LDPE‐g‐MAH) through melt‐blending way. The dielectric properties of these blends were emphasized for considering the compatibility effect on the energy storage application. Interface morphology, co‐continuity behavior, and grafted ratio were simultaneously investigated to detect the compatibility enhancement after introducing MAH. Results showed that the MAH positively improved the dielectric properties. Both the measured E_b of PVDF/LDPE and PVDF/LDPE‐g‐MAH blends showed a minimum value at v^PVDF = 50 vol % because of the worst compatibility; meanwhile, higher E_b of PVDF/LDPE‐g‐MAH than that of PVDF/LDPE blend was observed owing to the better compatibility. For considering the effect interface morphology on the dielectric performance, layer‐structure films composing with pure PVDF and LDPE layers were further constructed and studied. It was revealed that the layered structure could be treated as a helpful way to improve ε and E_b for immiscible polymer blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42507.     

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     

Dyeability and swelling properties of graft copolymers of LDPE with 2‐hydroxypropyl methacrylate monomer prepared by gamma radiation

Low density polyethylene (LDPE) films were grafted with 2‐hydroxypropyl methacrylate (HPMA) monomer by gamma radiation. The LDPE graft copolymer was characterized by FTIR spectroscopy, tensile mechanical testing, and thermogravimetric analysis (TGA). The dye affinity of LDPE graft copolymers for different dyestuffs was studied. Also, the effect of temperature on the swelling characters of LDPE‐g‐HPMA was investigated. The TGA study showed that the LDPE graft copolymers, over the studied graft yields, possessed higher thermal stability than pure LDPE polymer. While, LDPE has no dye affinity for any of the known dyestuffs, LDPE graft copolymers displayed a unique dye affinity for a wide range of dyestuffs belonging to different classes. The results showed that the equilibrium swelling of LDPE graft copolymers in water reached after 7 h. In addition, the results showed that the swelling of LDPE graft copolymers was influenced by temperature within the temperature range 10–40°C. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Effects of chemical modification of epoxy‐(ethylene diamine) on water hyacinth fibers (Eichhornia crassiper)‐filled (low‐density polyethylene)/(natural rubber) blends

The effects of modification by epoxy‐(ethylene diamine) (EED) on (water hyacinth fiber)‐filled (low‐density polyethylene)/(natural rubber) (LDPE/NR/WHF_‐EED) composites were studied. The LDPE/NR/WHF and LDPE/NR/WHF_‐EED composites were prepared by using a Brabender Plasticorder. LDPE/NR/WHF_‐EED showed higher tensile strength, Young's modulus, and elongation at break but lower molar sorption of toluene compared with LDPE/NR/WHF composites. The Fourier‐transform infrared radiation analysis indicated that the absorption peak at 1,648 cm^?1 exhibited the C? N band. This C? N band was formed from the bond of the epoxy group and the amine group in the WHF‐g‐epoxy‐(ethylene diamine) (WHF_‐EED). The scanning electron microscopic morphology of LDPE/NR/WHF_‐EED composites displayed rougher surfaces and less fiber pull, which improved the interfacial adhesion among the fiber/matrix. J. VINYL ADDIT. TECHNOL., 20:201–209, 2014. © 2014 Society of Plastics Engineers     

Dynamic study of free volume properties in polyethylene/styrene butadiene rubber blends by positron annihilation lifetime method

Positronium (Ps) formation in low and high‐density polyethylene (LDPE and HDPE) and styrene butadiene rubber (SBR), as well as in their blends (LDPE/SBR: 50/50 and HDPE/SBR: 50/50) has been investigated by positron annihilation lifetime (PAL) measurements as a function of low temperature (100–300 K). The glass transition temperature (T_g) for the initial polymers and their blends are determined by ortho‐positronium (o‐Ps) lifetime, τ₃ versus temperature as well as by differential scanning calorimetry (DSC) measurements. The temperature dependence of nanoscale free volume size shows similar trend for all the investigated samples indicating an abrupt change at T_g, which is found to be higher for SBR sample characterized by its high chain mobility. In addition, The T_g values deduced from PAL measurements are compared with the corresponding data deduced from DSC. The variation of o‐Ps formation probability I₃ versus temperature for polyethylene and their blends were interpreted in the frame work of spur reaction model of Ps formation. On the other hand, the lifetime coefficient below and above T_g is found to be one order of magnitude larger than the linear expansion coefficient. This constitutes evidence that Ps is only probing free volumes. The results obtained from change in free volume–hole distribution with temperature reflect both thermal expansion and increase in free volume–hole size with the rise in temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermally stable low‐density polyethylene/polyhydroxybutyrate pairs: Synergy between organomodified nanoclay and LDPE‐g‐MAH

Nanocomposites of low‐density polyethylene/polyhydroxybutyrate (LDPE/PHB) containing organomodified montmorillonite (OMMT) and/or LDPE grafted maleic anhydride (LDPE‐g‐MAH) were prepared with a wide range of composition ratios using a vertical co‐rotating twin‐screw microCompounder. To infer the effect of OMMT and LDPE‐g‐MAH on the thermal stability of prepared nanocomposites, all samples were characterized by thermogravimetric analysis while changing clay and compatibilizer contents. Accordingly, two commonly used kinetic models (Coats–Redfern and Horowitz–Metzger) were employed to correlate the thermal stability of the samples with kinetic parameters, including activation energy and pre‐exponential factor. Furthermore, morphological features of LDPE/PHB in the presence or absence of OMMT and LDPE‐g‐MAH were studied using scanning electron microscopy, transmission electron microscopy, and wide‐angle X‐ray diffraction analysis. It was found that for a specific OMMT composition ratio (1 wt %), the thermal stability is enhanced due to an exfoliated structure. However, for samples containing more organoclay (>=3 wt %), the thermal stability was reduced showing the competition between the barrier effect of organoclay platelets and the catalyzing effect of ammonium salts. Moreover, when using LDPE‐g‐MAH as compatibilizer, it acted as a good coupling agent in all compositions in LDPE major phase systems in contrast to PHB major phase samples. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45922.     

Effect of the parent solution concentration on the flocculation performance of PAAm flocculants and the relation between the optimal parent solution concentration and critical concentrations

Flocculation performance of three kinds of polyacrylamide (PAAm), linear‐PAAm, Al(OH)₃–PAAm hybrid, and star–PAAm, in kaolin suspensions have been investigated by Spectrophotometer. It was found that the flocculation performance of the polymer flocculant is enhanced at the beginning and then impaired with increasing parent solution concentration (C_p) and an optimal parent solution concentration (C_op) exists, which is directly proportional to both critical concentrations of C* and C_s of the polymer in the dilute aqueous solution, and can be roughly expressed by an empirical formula, C_op = 3.1 × 10^?3 + 643.1C_s. The findings suggests that flocculation performance of a given polymer is dependent on both of the interchain association and the chain contact of the polymer chains in the parent solution and in the kaolin suspension, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1585–1592, 2007