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     

Dynamic viscoelasticity of low‐density polyethylene/in‐situ‐grafted carbon black composite

The study on the dynamic viscoelastic properties of grafted carbon black (g‐CB) filled low‐density polyethylene (LDPE) was carried out. Because of formation of CB networking, the characteristic modulus plateau and loss tangent arc appears. Addition of grafting monomer like butyl acrylate (BA) and acroleic acid (AA) enhances the interaction between particles and matrix due to accelerated formation of micronetworking in the composites induced by forming branch chains of AA and BA with multiunit. The decrease of the temperature corresponding to α_c mechanical relaxation together with AA (BA) addition given by the position of loss tangent (tan δ) peak for LDPE is owed to the formation of long‐chain polymer grafted between CB and the matrix, which facilitates the slip of the lamella of LDPE. The influence of maleic anhydride (MA) on enhancing interaction between LDPE and CB is not so pronounced, as compared with AA and BA because of no formation of long chain between CB particle and polymer matrix. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4127–4132, 2006     

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     

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     

Ammonia adsorption behavior of polypropylene nonwoven fabric grafted with acrylic acid

An attempt was made to synthesize an adsorbent by the photoinduced grafting of acrylic acid (AA) onto polypropylene nonwoven fabrics using benzophenone (BP) as a photosensitizer in a CH₃OH/H₂O medium. As the BP concentration was increased, the graft yield was increased up to a specific value and then decreased, and the effect of AA concentration showed the same tendency. It was also found that the graft yield increased with the reaction time and temperature. The amounts of ammonia adsorbed onto polypropylene nonwoven fabrics grafted with AA (PP‐g‐AA) were dependent on the graft yield, adsorption time, and ammonia gas pressure. The adsorption capacity of PP‐g‐AA was 5.86 mmol/g at the graft yield of 116.6%, which was much higher than that of active carbon or silica gel. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 295–301, 2002; DOI 10.1002/app.10328     

Synthesis of acrylic acid grafted silicone rubber via preirradiation graft copolymerization and its physical and dielectric properties

The hydrophilic monomer, acrylic acid (AA), has been grafted onto hydrophobic silicone rubber (SR) film via the γ-ray preirradiation graft technique. The AA percent graft in SR-g-AA film increases with increasing irradiation dose rate. The iron powder in monomer solution serves as one source of ferrous ion that is generated by the oxidation reaction with water. The swelling effect shows that the amount of chloroform taken up by an SR-g-AA membrane decreases with the increasing AA grafting, and the amount of water, alcohol, and glycerol taken up by an SR-g-AA film increases with increasing AA percent grafting. The contact angle, ultimate stress, and elongation at break of SR and SR-g-AA copolymers decrease with increasing AA percent grafting. The oxygen/nitrogen selectivity in these films can be enhanced by the graft modification. The thermal behaviors of SR-g-AA copolymers show the characteristics of SR and polyacrylic acid. Finally, the dielectric properties show that the SR-g-AA film has a superior dielectric property than the original SR and poly(AA) matrix. © 1996 John Wiley & Sons, Inc.     

Control of biodegradability of poly(3‐hydroxybutyric acid) film with grafting acrylic acid and thermal remolding

Radiation‐induced graft polymerization of acrylic acid (AAc) on poly(3‐hydroxybutyric acid) (PHB) film was carried out and the resulting film was thermally‐remolded. The PHB films grafted with AAc (PHB‐g‐AAc) having a degree of grafting higher than 5% completely lost the enzymatic degradability. The enzymatic degradability of the grafted film was recovered by thermal remolding. The highest enzymatic degradation rate was observed at degree of grafting of 10% after thermal remolding. The PHB‐g‐AAc films and thermally‐remolded PHB‐g‐AAc films were characterized by contact angle and differential scanning calorimetry. The enzymatic degradability of PHB‐g‐AAc films was lost by the grafted AAc, which covered the surface of PHB film. The acceleration of enzymatic degradation in the remolded PHB‐g‐AAc films was mainly caused by decrease of crystallinity of PHB by dispread of grafted AAc during thermal remolding. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3856–3861, 2006     

Properties of grafted polymer metal complexes as ion exchangers and its electrical conductivity

A polyelectrolyte has been prepared, as a potential proton exchange polymer, by grafting acrylic acid/acrylamide (AAc/AAm) and acrylic acid/acrylonitrile (AAc/AN) comonomers onto a low‐density polyethylene film via gamma irradiation. The developed polymers were characterized by evaluating their physico‐chemical properties such as ion exchange capacity (IEC) and electrical conductivity as functions of grafting yield. The grafted film at different compositions was characterized by Fourier transform infrared, thermogravimetric analysis, and scanning electron microscopy. IEC of the grafted film at grafting % 191 and monomer concentration ratio 50:50 for (LDPE‐g‐AAc/AAm) was found to be more than that for (LDPE‐g‐AAc/AN). The electrical conductivity was found to be greatly affected by the comonomer composition, were it increased as the degree of grafting increased for all grafted films. After alkaline treatment with 3% KOH (3% potassium hydroxide), the electrical conductivity of the grafted films found to be increased. The presence of potassium as counter ion maximized the electrical conductivity of the grafted films. The electrical conductivity of Cu‐membrane complexes was higher than that of both Co (cobalt) and Ni (Nickel) complexes. It has been indicated that, the electrical conductivity increased by increasing both Cu ion content and temperature. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers.     

Modification of low‐density polyethylene by graft copolymerization with maleic anhydride and blends with polyamide 6

Modification of low‐density polyethylene (LDPE) hyperbranched grafting with a maleic anhydride (MAH) was carried out using corotating twin screw extruder in the presence of benzoyl peroxide. The LDPE/polyamide 6 (PA6) and LDPE‐g‐MAH/PA6 blends were obtained with a corotating twin screw extruder. The melt viscosity of the grafted LDPE was measured by a capillary rheometer. The grafted copolymer was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy The effects of variations in temperature, PA6 loading, and benzoyl peroxide and MAH concentration were investigated. The results show that most MAH monomers were grafted onto the LDPE at a lower MAH concentration. With the proper selection of the reaction parameters, we obtained a grafting degree higher than 4.9%. Mechanical test results indicate that the blends had good interfacial adhesion and good stability of the phase structure during heating, which was reflected in the mechanical properties. Furthermore, the results reveal that the tensile strength of the blends increased continuously with increasing PA6 content. Moreover, the home‐synthesized maleated LDPE could be used for the compatibilization of LDPE/PA 6 blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Investigation of molecular structure of LDPE modified by itaconic acid grafting

Using thermomechanical spectroscopy, the molecular‐weight distribution and relaxation transitions have been investigated in commercial LDPE and grafted by itaconic acid (LDPE‐g‐IA). This grafting in the molten LDPE was done by reactive extrusion with varied content of reactants in the blend under alternating of a shearing rate applied onto the melt. The dependence of structural relaxation changes in LDPE is shown upon the depth of the mechanochemical transformations and the competing reactions at IA grafting, and also on the chemical crosslinking of the macromolecules. The reason for MWD bimodality for LDPE‐g‐IA obtained in dynamic mixing is the raised homogenization degree of the reactive blend and the higher grafted product yield compared with static mixers. The mixer type substantially affects the structure of the LDPE‐g‐IA amorphous phase. The data obtained reflect chemical transformations of LDPE molecules in IA's presence without an initiator of radical reactions (DCP). Most probable is the IA initiation of molecular crosslinking reactions. There could also occur IA thermodegradation and oligomerization. LDPE and IA or products of acid chemical transformations do not agree thermodynamically (the calculated solubility parameters are 16.1 (MJ/m³)^0.5 for polyethylene and 26.4 (MJ/m³)^0.5 for IA). From the above procedure it can be supposed that nongrafted IA (or its oligomers) exerts an antiplastifying effect on LDPE and LDPE‐g‐IA. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1771–1779, 1999     

Preparation of acrylic acid grafted polypropylene nonwoven fabric by photoinduced graft polymerization with preabsorption of monomer solution

We improved photoinduced graft polymerization by absorbing the monomer solution onto the substrate (Ab‐type) instead of immersing the substrate in the monomer solution (Im‐type) before photoirradiation to yield a more practical and effective grafting system. With this system, acrylic acid (AA) was effectively grafted onto polypropylene (PP) nonwoven fabric. The maximum degree of grafting obtainable was restricted by the amount of monomer preabsorbed onto the PP fabric. However, we effectively enhanced the degree of grafting by increasing the monomer concentration, adding trimethylolpropane triacrylate (TMPTA) to the monomer solution, and repeating the photoirradiation with supplementation of the monomer solution. The net availability of the monomer for graft polymerization was 50% or greater; this increased to 90% or greater with the addition of TMPTA and was much higher than for conventional Im‐type photografting (≤13%). Fourier transform infrared spectra, scanning electron microscopy morphology observations, and the adsorption–regeneration properties confirmed that the PP‐g‐AA fabric prepared by the improved Ab‐type photografting method had comparable qualities to those of fabric prepared by conventional Im‐type photografting. Thus, the improved Ab‐type photografting system provides potential for the preparation of graft adsorbents on a large scale at a competitive cost with a continuous reactor, such as a conveyer belt system, instead of a batch reactor. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Solvothermal process for grafting dibutylmaleate onto poly(ethylene‐co‐1‐octene)

Solvothermal process was successfully developed to graft dibutylmaleate (DBM) onto poly(ethylene‐co‐1‐octene) (POE) with dicumyl peroxide (DCP) as free radical‐initiator. FTIR spectra demonstrate that DBM is successfully grafted onto the backbone of POE by this novel method. The influences of DBM content, DCP concentration, POE concentration, reaction temperature and reaction time on the grafting copolymerization have been investigated in detail through grafting degree (GD). It is worthy to indicate that high grafting degree (above 15%) can be achieved through the one‐pot way when the graft reaction is carried out in 40 mL toluene at 150°C for 5 h with 1.6 g DBM, 6–8 g POE and 0.35 g DCP. This developed solvothermal process is becoming an effective way to prepare POE‐g‐DBM graft copolymers, and can be extended to other systems. In addition, TGA results show that the thermal properties of POE are enhanced after the grafting reaction. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of ion‐exchange membranes by hydrolysis of radiation‐grafted polyethylene‐g‐polyacrylamide membranes

Polyethylene‐g‐polyacrylamide membranes were prepared by graft polymerization of acrylamide onto polyethylene films using a preirradiation method. The ion‐exchange membranes were obtained by the hydrolysis of grafted films so as to transform amide groups into carboxyl groups. The fraction of amide groups transformed into carboxyl groups was limited to ～0.5. The characterization and thermal behavior of membranes with different degrees of grafting were evaluated by FTIR, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) measurements. The heat of fusion and the crystallinity of polyethylene decreased considerably in the hydrolyzed membranes depending on the degree of grafting. It was found that the grafting of acrylamide led to the reduction in crystallinity due to disruption of the crystallites (crystal defects) and dilution of the inherent crystallinity (dilution effect). The contribution of the hydrolysis step to the crystallinity decrease was negligible. The thermal stability of the membranes as obtained from TGA showed considerable enhancement after hydrolysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 149–154, 2003     

Characterization of acrylic acid grafted poly(ethylene terephthalate) fabric

The preirradiation grafting of acrylic acid (AA) onto poly(ethylene terephthalate) (PET) had been found to affect the thermal and physical characteristics of fabric. The grafted fabrics with various graft levels were characterized by thermal gravimetric analysis (TGA), ATR‐FTIR spectroscopy, contact angle, differential scanning calorimetry (DSC), X‐ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The initial decomposition temperature and T₅₀ were increased with the increase in degree of grafting. The percentage crystallinity was decreased as the degree of grafting increases. The detailed elemental analysis was done by X‐ray photoelectron spectroscopy (XPS). The atomic ratio (O_1s/C_1s) was found to increase significantly with increasing the degree of grafting and reached 0.64 at 14.5% grafting from 0.38 for virgin PET. The surface topography and morphology was strongly influenced as the degree of grafting was increased. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Studies on preparation and properties of vinyltriethoxysilane‐grafted styrene‐butadiene rubber

Graft polymerization of vinyltriethoxysilane (VTES) onto styrene‐butadiene rubber (SBR) was carried out in latex using benzoic peroxide (BPO) as an initiator. The concentration of VTES effecting on vulcanization characteristics, mechanical properties and thermal properties of VTES‐grafted SBR (SBR‐g‐VTES) were investigated. The grafting of VTES onto SBR and its pre‐crosslinking were confirmed by attenuated total teflectance‐Fourier transform infrared reflectance and proton nuclear magnetic resonance. The mechanism of graft polymerization was studied. The results revealed that the minimum torque, optimum cure time, tensile strength, thermal decomposition temperature, and glass transition temperature (T_g) all increased with the increasing concentration of VTES. But the grafting efficiency of VTES, rate of vulcanization, and elongation at break of the SBR‐g‐VTES decreased. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Structural investigations of poly(ethylene terephthalate)‐graft‐polystyrene copolymer films

Structural investigations of poly(ethylene terephthalate)‐graft‐polystyrene (PET‐g‐PS) films prepared by radiation‐induced grafting of styrene onto commercial poly(ethylene terephthalate) (PET) films were carried out by FTIR, X‐ray diffraction (XRD), and differential scanning calorimetry (DSC). The variation in the degree of crystallinity and the thermal characteristics of PET films was correlated with the amount of polystyrene grafted therein (i.e., the degree of grafting). The heat of melting was found to be a function of PET crystalline fraction in the grafted films. The grafting is found to take place by incorporation of amorphous polystyrene grafts in the entire noncrystalline (amorphous) region of the PET films and at the surface of the crystallites. This results in a decrease in the degree of crystallinity with the increase in the degree of grafting, attributed to the dilution of PET crystalline structure with the amorphous polystyrene, without almost any disruption in the inherent crystallinity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1949–1955, 2002; DOI 10.1002/app.10515     

Preparation of toughened polypropylene‐g‐poly(butyl acrylate‐co‐acrylated castor oil) by suspension grafting polymerization

Butyl acrylate (BA) with acrylated castor oil (ACO) was grafted onto porous polypropylene (PP) granules by grafting polymerization. Crosslinked copolymer microdomains which functioned as rubber phase to improve the toughness of PP were filled into the pores of PP granules. The sizes of crosslinked copolymer microdomains were controlled in the range of 0.1–1 μm in PP matrix. The results of fourier transform infrared spectroscopy and scanning electron microscope of PP‐g‐(BA‐co‐ACO) after extracted by acetone confirmed that BA and ACO were grafted onto PP successfully. The effects of comonomer ratio, initiator content and comonomer content on grafting percentage (GP) and grafting efficiency (GE) were investigated. The GP of PP‐g‐(BA‐co‐ACO) could be up to 21.3% with the comonomer content increasing to 25%. The crosslinked copolymer decreased the melting flow index and the relative crystallinity of PP. Dynamic mechanical thermal analysis showed that the glass transition temperature of PP decreased slightly from 22°C to 15°C. The addition of 5% comonomer content led to an increase of notched impact strength from 1.96 to 3.81 kJ/m² (nearly doubled) and a marginal decrease in the tensile strength of PP. Then with further addition of comonomer, the notched impact strength increased to 8.98 kJ/m² while the tensile strength was 29.37 MPa. POLYM. ENG. SCI., 58:86–93, 2018. © 2017 Society of Plastics Engineers     

Ozone‐induced grafting of a sulfoammonium zwitterionic polymer onto low‐density polyethylene film for improving hemocompatibility

Ozone‐induced grafting was developed to improve the hemocompatibility of biomaterials based on low‐density polyethylene (LDPE). An LDPE film was activated with ozone and graft‐polymerized with N,N′‐dimethyl(methacryloylethyl)ammonium propane sulfonate (DMAPS). The existence of sulfobetaine structures on the grafted film was confirmed by X‐ray photoelectron spectroscopy and attenuated total reflection/Fourier transform infrared (ATR–FTIR). More DMAPS was grafted onto the LDPE film as the DMAPS concentration increased, as determined by ATR–FTIR. Static contact‐angle measurements indicated that the DMAPS‐grafted LDPE film had a significant increase in hydrophilicity. The blood compatibility of the grafted film was preliminarily evaluated with a platelet‐rich‐plasma (PRP) adhesion study. No platelet adhesion was observed on the grafted film incubated with PRP at 37°C for 180 min. This new sulfoammonium zwitterionic‐structure‐grafted biomaterial might have potential for biomedical applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3697–3703, 2006     

Photoinduced grafting of vinyl benzyl trimethyl ammonium chloride on polyester nonwoven fabric with surfactant coating and its anion‐exchange properties

Vinyl benzyl trimethyl ammonium chloride (VBTAC) could be efficiently and stably grafted onto polyester fiber coated with a surfactant polyester (PET) by a photoirradiation‐induced graft polymerization with benzophenone as the photoinitiator without any cografting monomer required. The degree of VBTAC grafting could be controlled simply by the irradiation time and concentration of VBTAC in the monomer solution. The anion‐exchange capacity (AEC) of the PET‐g‐VBTAC fabrics increased with increasing degree of grafting up to 80 ± 5% and then leveled off. The maximum AEC of PET‐g‐VBTAC was 2.2 mequiv/g; this was similar to that of a commercial anion‐exchange resin (2.16 ± 0.04 mequiv/g) and much higher than those of nylon‐g‐VBTAC–2‐hydroxyethyl methacrylate fabrics (≤1.0 mequiv/g) prepared with a conventional cografting system. The grafted fabric was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy studies, and the sorption selectivity for anions and regeneration efficiency were estimated. The results suggest that the grafting system, in which VBTAC alone was grafted onto PET fiber coated with surfactant, was more practical and effective for the preparation of the VBTAC‐containing anion exchanger, and the resulting PET‐g‐VBTAC fabrics could be used as an effective anion exchanger. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41674.     

Grafting of hydrophilic monomers onto aminopropyl‐functionalized sodium montmorillonite via surface‐initiated redox polymerization

Hydrophilic polymer/sodium montmorillonite (Na‐MMT) hybrid nanomaterials were prepared via surface‐initiated redox polymerization of 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (PAMPS‐g‐MMT), acrylamide (PAAm‐g‐MMT) and styrenesulfonic acid sodium salt (PSSA‐g‐MMT) from surface of aminopropyl‐functionalized sodium montmorillonite (AMMT) dispersed in an aqueous medium. Cerium(IV) ammonium nitrate/nitric acid and aminopropyl groups on the surface of AMMT were used as oxidant and reducing groups, respectively. AMMT was prepared by covalently attaching 3‐aminopropyltriethoxysilane onto the surface of Na‐MMT. Hydrophilic monomers (AMPS, AAm and SSA) were then grafted onto AMMT dispersed in water via redox initiation at 40 °C. Structure, morphology and thermal properties of the AMMT, PAMPS‐g‐MMT, PAAm‐g‐MMT and PSSA‐g‐MMT hybrid materials were characterized using Fourier transform infrared (FTIR), X‐ray diffraction (XRD) and thermogravimetric (TGA) analyses, respectively. FTIR results indicated that hydrophilic monomers were successfully grafted onto the surface of MMT. Grafting amounts of the hydrophilic polymers were estimated from TGA thermograms to be 28.8, 118.8 and 14.4% for PAMPS, PAAm and PSSA, respectively. XRD patterns showed an exfoliated morphology for PAMPS‐ and PAAm‐grafted MMT hybrid nanomaterials and an intercalated/exfoliated morphology for the PSSA‐grafted MMT one. The effect of the nature of hydrophilic monomer on the grafting efficiency is discussed in detail. © 2013 Society of Chemical Industry