Structure and adhesion properties of acrylic acid grafted high‐density polyethylene powders synthesized by a novel photografting method

A novel photografting, nonvapor, and nonliquid phase living graft polymerization was developed to functionalize high‐density polyethylene (HDPE) powder. The structure and adhesion properties of HDPE powder grafted with acrylic acid (AA) were studied by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), water contact angle, peel strength, and graft degree measurements. The result shows that HDPE powder can be grafted with AA via the method with a short reaction time and a high monomer conversion. The graft degree increases with the reaction time. Then, the hydrophilicity of the grafted HDPE powder increases also. The peel strength of HPDE/steel joint improved significantly when acrylic acid grafted HPDE powder was used as hot melt adhesive in place of ungrafted HDPE powder. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mechanical properties of uncrosslinked and crosslinked linear low‐density polyethylene/wax blends

The mechanical properties of uncrosslinked and crosslinked linear low‐density polyethylene (LLDPE)/wax blends were investigated, using differential scanning calorimetry (DSC), tensile testing, and melt flow indexing. A decrease in the degree of crystallinity, as determined from the DSC melting enthalpies, was observed with an increase in the dicumyl peroxide (DCP) concentration. The Young's modulus increased with increased wax portions, and there was a higher increase for crosslinked blends. The yield stress generally decreased with increased peroxide content. Crosslinking caused an increase in elongation at yield, but increased wax content caused a decrease in elongation at yield. The stress at break generally increased with increasing peroxide content, but it decreased with increased wax content. The elongation at break decreased with an increase in the DCP concentration. Melt flow rate measurements indicated a mutual miscibility in LLDPE/wax blends. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 973–980, 2001     

Influence of branching characteristics on thermal and mechanical properties of Ziegler–Natta and metallocene hexene linear low‐density polyethylene blends with low‐density polyethylene

The effect of the branch content (BC) and composition distribution (CD) of linear low‐density polyethylene (LLDPE) on the thermal and mechanical properties of its blends with LDPE were studied. All blends and pure resins were conditioned in a Haake PolyDrive blender at 190°C and in the presence of adequate amounts of antioxidant. Two metallocene LLDPEs (m‐LLDPE) and one Ziegler–Natta (ZN) hexene LLDPE were melt blended with the same LDPE. The effect of the BC was investigated by blending two hexene m‐LLDPEs of similar weight‐average molecular weights and molecular weight distributions but different BCs with the same LDPE. The effect of the CD was studied by using a ZN and an m‐LLDPE with similar weight‐average molecular weights, BCs, and comonomer type. Low‐BC m‐LLDPE blends showed separate crystallization whereas cocrystallization was observed in the high‐BC m‐LLDPE‐rich blends. However, ZN‐LLDPE/LDPE blends showed separate crystallization together with a third population of cocrystals. The influence of the crystallization behavior was reflected in the mechanical properties. The BC influenced the modulus, ultimate tensile strength, and toughness. The addition of a small amount of LDPE to a low‐BC m‐LLDPE resulted in a major improvement in the toughness, whereas the results for the high‐BC pair followed the additivity rule. ZN‐LLDPE blends with LDPE blends were found to be more compatible and exhibited superior mechanical properties compared to m‐LLDPE counterparts with the same weight‐average molecular weight and BC. All mechanical properties of ZN‐LLDPE blends follow the linear rule of mixtures. However, the CD had a stronger influence on the mechanical properties in comparison to the BC. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2488–2498, 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     

LLDPE与甲基丙烯酸接枝共聚

采用溶液聚合和悬浮聚合法研究了线型低密度聚乙烯对甲基丙烯酸的接枝行为，发现溶液接枝法的产物有较高的接枝率，对铝箔的粘合力很强。     

Effect of the compatibilization of linear low‐density polyethylene‐g‐acrylic acid on the morphology and mechanical properties of poly(butylene terephthalate)/linear low‐density polyethylene blends

A poly(butylene terephthalate) (PBT)/linear low‐density polyethylene (LLDPE) alloy was prepared with a reactive extrusion method. For improved compatibility of the blending system, LLDPE grafted with acrylic acid (LLDPE‐g‐AA) by radiation was adopted in place of plain LLDPE. The toughness and extensibility of the PBT/LLDPE‐g‐AA blends, as characterized by the impact strengths and elongations at break, were much improved in comparison with the toughness and extensibility of the PBT/LLDPE blends at the same compositions. However, there was not much difference in their tensile (or flexural) strengths and moduli. Scanning electron microscopy photographs showed that the domains of PBT/LLDPE‐g‐AA were much smaller and their dispersions were more homogeneous than the domains and dispersions of the PBT/LLDPE blends. Compared with the related values of the PBT/LLDPE blends, the contents and melting temperatures of the usual spherulites of PBT in PBT/LLDPE‐g‐AA decreased. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1059–1066, 2002; DOI 10.1002/app.10399     

Thermal properties and morphology of recycled poly(ethylene terephthalate)/maleic anhydride grafted linear low‐density polyethylene blends

Properties of recycled Poly(ethylene terephthalate) were greatly improved. Recycled PET was blended with LLDPE‐g‐MA by low‐temperature solid‐state extrusion. Mechanical properties of the blends were affected obviously by the added LLDPE‐g‐MA. Elongation at break reaches 352.8% when the blend contains 10 wt % LLDPE‐g‐MA. Crystallization behavior of PET phase was affected by LLDPE‐g‐MA content. Crystallinity of PET decreased with the increase of LLDPE‐g‐MA content. FTIR testified that maleic anhydride group in LLDPE‐g‐MA reacted with the end hydroxyl groups of PET and PET‐co‐LLDPE‐g‐MA copolymers were in situ synthesized. SEM micrographs display that LLDPE‐g‐MA phase and PET phase are incompatible and the compatibility of the blends can be improved by the forming of PET‐co‐LLDPE‐g‐MA copolymer. LLDPE‐g‐MA content was less, the LLDPE‐g‐MA phase dispersed in PET matrix fine. With the increase of LLDPE‐g‐MA content, the morphology of dispersed LLDPE‐g‐MA phase changed from spherule to cigar bar, then to irregular spherule. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Blend of high‐density polyethylene and a linear low‐density polyethylene with compositional‐invariant mechanical properties

This article presents the tensile properties and morphological characteristics of binary blends of the high‐density polyethylene (HDPE) and a linear low‐density polyethylene (LLDPE). Two constituents were melt blended in a single‐screw extruder. Injection‐molded specimens were evaluated for their mechanical properties by employing a Universal tensile tester and the morphological characteristics evaluated by using a differential scanning calorimeter and X‐ray diffractometer. It is interesting to observe that the mechanical properties remained invariant in the 10–90% LLDPE content. More specifically, the yield and breaking stresses of these blends are around 80% of the corresponding values of HDPE. The yield elongation and elongation‐at‐break are around 65% to corresponding values of HDPE and the modulus is 50% away. Furthermore, the melting endotherms and the crystallization exotherms of these blends are singlet in nature. They cluster around the corresponding thermal traces of HDPE. This singlet characteristic in thermal traces entails cocrystallization between these two constituting components. The clustering of thermal traces of blends near HDPE meant HDPE‐type of crystallites were formed. Being nearly similar crystallites of blends to that of HDPE indicates nearness in mechanical properties are observed. The X‐ray diffraction data also corroborate these observations. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2604–2608, 2002     

Platelet adhesion on laser‐induced acrylic acid–grafted polyethylene terephthalate

To improve blood compatibility, acrylic acid (AAc) was grafted onto a polyethylene terephtalate (PET) film surface using lasers. The PET surface was irradiated with a CO₂ pulsed laser, and then graft copolymerization was carried out in an aqueous solution of AAc in the presence of Mohr's salt. Different techniques such as attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR), scanning electron microscopy (SEM), and contact angle measurements were used to characterize the modified PET surface. The ATR‐FTIR spectra confirmed the creation of new functional groups on the PET surface, and contact angle measurements revealed that the hydrophilicity of the PET surface increased as a result of the AAc graft polymerization. The electron micrographs showed that the grafting changed the surface morphology of the PET film. To evaluate the blood compatibility in vitro, the number of platelets adhering to the modified PET surface was determined using lactate dehydrogenase (LDH) activity measurement. The data from LDH method indicated that the extent of platelet adherence on the unmodified PET was much higher than that on the AAc grafted PET. The morphology of adhered platelets on the PET surface was investigated by SEM. The results showed that platelet adhesion and activation onto the PET surface was reduced because of AAc graft polymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3191–3196, 2002     

Characteristics of acrylic acid and N-isopropylacrylamide binary monomers–grafted polyethylene film synthesized by photografting

Method for introducing grafted chains consisting of two types of monomer components, acrylic acid (AA) and N-isopropylacrylamide (NIPAAm), into low-density polyethylene (PE) film (thickness = 25 μm) was investigated by two photografting technique using xanthone photoinitiator at 60°C. In the first method (one-step method), AA and NIPAAm binary monomers were graftcopolymerized onto PE film. In the second method (two-step method), AA was first photografted onto PE film and then NIPAAm was further introduced into the AA-grafted PE film by a second-step photografting. Water absorbencies of the grafted films (one- and two-step samples) prepared by the one- and two-step methods, respectively, decreased in the order of AA-grafted film > one-step sample > two-step sample > NIPAAm-grafted film. The water absorbency steeply decreased at 20 to 40°C with increasing temperature when immersed in water at the temperatures (5–60°C) for 24 h. Thermosensitivity, which was defined as the ratio of water absorbencies of the grafted samples at 5 and 60°C, was higher for the one-step sample than the two-step one. The different extent of the water absorbency and the thermosensitivity between both samples is discussed in terms of location of grafted chains in the film substrate, which was determined by electron probe microanalysis and attenuated total reflection–infrared measurements, and monomer sequence distribution of the grafted chains. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2057–2064, 1998     

Assessment and characterization of antifungal and antialgal performances for biocide‐enhanced linear low‐density polyethylene

In this work, four biocides were used for the purpose of growth inhibition of fungi and algae in linear low‐density polyethylene (LLDPE) specimens. Benzimidazol‐2‐yl‐carbamicacid methyl ester [carbendazim (CB)], 5‐chloro‐2‐(2,4‐dichlorophenoxy)phenol [triclosan (TS)], and 3‐iodo‐2‐propynyl N‐butylcarbamate [iodopropynyl butylcarbamate (IPBC)] were used as antifungal agents, and 2‐methylthio‐4‐ethylamino‐6‐tert‐butylamino‐triazin‐1,3,5 [terbutryn (TT)] was used as an antialgal agent. Antifungal performance was evaluated by disk diffusion and dry weight techniques, and antialgal activities were carried out by disk diffusion and chlorophyll A methods. Aspergillus niger TISTR 3245 and Chlorella vulgaris TISTR 8580 were used as the testing fungus and alga, respectively. The experimental results suggested that the wettabilities of LLDPE specimens changed with the incorporation of CB, TS, IPBC, and TT biocides without significant changes in chemical structures and mechanical properties of the LLDPE. IPBC with the recommended content of 10,000 ppm was found to give the most satisfactory growth inhibition of A. niger. Antifungal performance evaluations were dependent on the testing methods used, whereas those for antialgal activity were not. The optimum concentration of TT agent for effective killing of C. vulgaris was 750 ppm; this loading could be reduced from 750 to 250 ppm by the addition of either TS or IPBC agent. TS and IPBC could be used as antialgal promoters in the LLDPE specimens. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013     

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     

Photografting of acrylic acid on high density polyethylene powder in vapour phase

A photografting technique was explored as a means of functionalizing high density polyethylene (HDPE) powder. The graft copolymerization reaction of acrylic acid on HDPE powder and the surface structure of grafted HDPE powder were studied in terms of grafting degree and grafting efficiency, and by FTIR and ESCA. The results show that the surface of chemically inert HDPE powder pretreated by an acetone solution of benzophenone (BP) can be graft‐copolymerized with acrylic acid by photografting in the vapour phase. Thereby, the grafting degree is increased but the grafting efficiency is decreased with increasing reaction time. When the BP concentration in pretreatment solution is increased, the grafting degree is increased to a maximum, and is then reduced. The most suitable reaction temperature is 90 °C. Grafting degree can reach the quite high value of 10.6 wt% under the conditions of BP concentration 1.0 wt%, reaction time 1 h and temperature 90 °C. © 2000 Society of Chemical Industry     

Sago starch‐filled linear low‐density polyethylene (LLDPE) films: Their mechanical properties and water absorption

Composites containing various percentages of sago starch and linear low‐density polyethylene (LLDPE) have been prepared. The mechanical properties and water uptake of the composites have been determined. The tensile strength and elongation at break decreased with increase in starch content. However, the modulus of the composites increased with increase in starch content. The yield strength was not significantly affected. Moisture uptake in humid air and in water increased with increase in starch content. At higher relative humidity the composites absorbed more moisture, thus indicating that the moisture barrier properties decreased with increase in relative humidity. Moisture uptake was highest when the composites were completely immersed in water. Scanning electron microscopy (SEM) shows agglomeration of the starch granules and hence, poor wetting between the starch granules and LLDPE matrix. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 29–37, 2001     

Preparation of linear low‐density polyethylene by in situ copolymerization of ethylene with Zr supported on montmorillonite/Fe/methylaluminoxane catalyst system

Linear low‐density polyethylene (LLDPE) was prepared by in situ copolymerization of ethylene with dual‐functional catalysts that were composed of rac‐Et(Ind)₂ZrCl₂ supported on montmorillonite (MMT) and {[(2‐ArN?C(Me))₂C₅H₃N]FeCl₂} [Ar = 2,4‐C₆H₄(Me)₂] oligomerization catalyst. A series of polyethylenes with different degrees of branching were obtained by adjusting the ratio of Fe and Zr (Fe/Zr). DSC, NMR, GPC, SEM, and density‐gradient method were used to characterize the polymers. With increasing Fe/Zr ratio, the densities and melting points of polymers decreased, whereas the branching degrees and molecular weights increased. When the Fe/Zr ratio was increased, the activities of the catalysts decreased at atmospheric pressure and increased at 0.7 MPa ethylene pressure. SEM micrographs revealed that the morphology of branched polyethylene, produced with the catalyst supported on MMT, is better than that produced by the catalyst in a homogeneous system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1690–1696, 2004     

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     

On promoting intercalation and exfoliation of bentonite in high‐density polyethylene by grafting acrylic acid

Acrylic acid (AA) grafted high‐density polyethylene (HDPE)/bentonite (BT) composites and HDPE/BT composites were prepared via melt compounding. XRD and TEM results indicated that the modification of AA grafting promoted the dispersion and intercalation of BT in HDPE matrix; IR proved that there were interactions between AA and BT sheets. Consequently, with increasing BT content, the tensile strength and Young's modulus of HDPE‐g‐AA/BT nanocomposites increased, while that of HDPE/BT composites decreased. Moreover, the addition of BT to HDPE‐g‐AA decreased the ability of crystallization of the matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2429–2434, 2005     

Dielectric relaxation of polar aromatics in unoriented and oriented linear low‐density polyethylene

The dielectric behavior of some polar aromatics dissolved in nonpolar unoriented and stretched linear low‐density polyethylene was investigated within the temperature region between 150 and 350 K. The measurements were carried out in the frequency range 1 kHz to 10 MHz. The maximum temperatures and the half widths of the loss tangent peaks depend upon the shape and the polar structure of guest molecules. Stretching the samples induced a shift of the loss tangent to higher temperatures, decreased the height, and increased the width of tan δ peak. The activation energy is also influenced by the type of guest molecules and orientation of polymer matrix. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1278–1282, 2001     

Adhesion of surface‐grafted low‐density polyethylene plates with enzymatically modified chitosan solutions

An investigation was undertaken on application of dilute chitosan solutions modified by tyrosinase‐catalyzed reaction with 3,4‐dihydroxyphenetylamine (dopamine) to adhesion of the low‐density polyethylene (LDPE) plates surface‐grafted with hydrophilic monomers. Tensile shear adhesive strength effectively increased with an increase in the grafted amount for methacrylic acid‐grafted and acrylic acid‐grafted LDPE (LDPE‐g‐PMAA and LDPE‐g‐PAA) plates. In particular, substrate breaking was observed at higher grafted amounts for LDPE‐g‐PAA plates. The increase in the amino group concentration of the chitosan solutions and molecular mass of the chitosan samples led to the increase in adhesive strength. Adhesive strength of the PE‐g‐PMAA plates prepared at lower monomer concentrations sharply increased at lower grafted amounts, which indicates that the formation of shorter grafted PMAA chains is an effective procedure to increase adhesive strength at lower grafted amounts. Infrared measurements showed that the reaction of quinone derivatives enzymatically generated from dopamine with carboxyl groups was an important factor to increase adhesive strength in addition to the formation of the grafted layers with a high water absorptivity. The above‐mentioned results suggested that enzymatically modified dilute chitosan solutions can be applied to an adhesive to bond polymer substrates. The emphasis is on the fact that water is used as a solvent for preparation of chitosan solutions and photografting without any organic solvents. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Experimental estimation of gas‐transport properties of linear low‐density polyethylene membranes by an integral permeation method

In recent years, we have investigated gas‐transport phenomena in coextruded linear low‐density polyethylene (LLDPE) membranes. For the most part, coextruded LLDPE membranes were investigated because of their excellent mechanical properties, which explain their extensive use in the packaging industry. Because of the small thickness of coextruded LLDPE membranes, significant errors can be involved in the determination of the diffusion coefficient of gases in the membranes by the time‐lag method. To obtain more precise transport parameters for LLDPE membranes, we determined the permeability and diffusion coefficients for O₂, CO₂, He, and N₂ from 298 to 348 K by employing an alternative method recently developed. The results indicate that the procedure used in this study for determining the diffusivity of gases in membranes was precise and more efficient than a method based on the evaluation of the time‐lag parameter. With respect to permeability, the coefficients obtained in this work agree satisfactorily with those obtained by the time‐lag method. In general, the permeability and diffusivity results are in satisfactory agreement with the literature values reported for semicrystalline polyethylene membranes. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3013–3021, 2001