The influence of variant PE‐b‐PEO segments on physical properties of LLDPE graft copolymers

A method was adopted to fix a series of polymers of PE‐b‐PEO with different PEO/PE segments on the chains of LLDPE. Maleic anhydride (MA) reacting with hydroxyl group of PE‐b‐PEO (mPE‐b‐PEO) was used as the intermediate. The structures of intermediates and graft copolymers were approved by ¹H NMR and FTIR. XPS analysis revealed a great amount of oxygen on the surface of grafted copolymers although the end group of PEO was fixed on the LLDPE chains through MA. Thermal properties of the graft copolymers as determined by differential scanning calorimetry (DSC) showed that PE segments in the grafted monomers could promote the heterogeneous nucleation of the polymer, increase T_c, and crystal growth rate. While the amorphous PEO segments which attached to the crystalline PE segments in LLDPE, impaired their ability to fit the crystal lattice, and depressed the crystallization of LLDPE backbones. In this study, it was also verified through the dynamic rheological data that increasing M_n of grafted monomers significantly increased the complex viscosity and enhanced the shear‐thinning behavior. Long‐branched chains formed by grafted monomers enhanced the complex moduli (G′ and G″) value and retarded relaxation rate. However, there were little influence on the rheological properties when increasing the amounts of PEO segments (or decreasing PE segments) of grafted monomers with similar molecular weight. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 506–515, 2008     

马来酸酐-苯乙烯熔融接枝聚丙烯的影响因素及其性能研究

用单螺杆挤出机制备了马来酸酐 (MAH) 苯乙烯 (St)对聚丙烯 (PP)的多组分单体自由基熔融接枝体系 .研究证实了当两种单体物质的量比约为 1∶1时 ,接枝物的接枝率最高 ,而熔体流动速率 (MFR)最大 .对反应体系影响因素的研究表明单体用量和引发剂用量对不同单体用量比的系列接枝物的接枝率会产生不同的影响 ;另外 ,单体用量增加 ,接枝物的MFR减小 ,过氧化二异丙苯 (DCP)用量增加 ,接枝物的MFR增加 .对多单体熔融接枝聚丙烯PP g (MAH co St)的力学性能研究发现 ,选用合适的单体用量比、单体用量和DCP用量时 ,所制备的接枝物可具有与纯PP相当或更佳的力学性能     

马来酸酐-苯乙烯多组分单体熔融接枝高密度聚乙烯机理及性能研究

用单螺杆挤出机制备了马来酸酐-苯乙烯(MAH-St)多单体熔融接枝高密度聚乙烯(HDPE)体系,研究发现添加St共同接枝,可以显著提高接枝物的接枝率.随着St的增加,接枝率先增大后有所降低.当两种单体物质的量比约为1:1时,接枝物的接枝率最高,此时接枝物的熔体流动速率(MFR)最小.即MAH接枝率越高,接枝物的MFR越...     

GRAFTING OF PEROXIDE-INITIATED MALEIC ANHYDRIDE ON SPHERICAL PE／PP IN-REACTOR BLEND GRANULES

Spherical polyethylene/polypropylene (PE/PP) in-reactor blend granules with various ethylene/propylene molar ratios and high porosity were synthesized using a high yield TiCl4/MgCl2 supported catalyst. A solution of benzoyl peroxide (BPO)/maleic anhydride (MAH)/xylene (interfacial reagent) or BPO/MAH/St (comonomer) was absorbed onto the PE/PP inreactor blend granules, and solid phase gratt polymerization of MAH on PE/PP was conducted. The amount of grafted MAH on PE/PP was measured through chemical titration. The results showed that solid phase graft polymerization of MAH in PE/PP in-reactor blend granules produced graft copolymer with high amount of grafted MAH, and the amount of grafted MAH was raised slightly when St was introduced as comonomer. The graft in-reactor blend was fractionated into five fractions through temperature-gradient extraction fractionation (TGEF), and the fractions were analyzed by FTIR. The results revealed that MAH is mainly grafted on the PE segments, whereas MAH was predominantly grafted on the PP segments when St was present in the graft polymerization system. In addition, the final product is still in the form of regular spherical granules, which is beneficial for industrial processing.     

A study on melt grafting of maleic anhydride onto low‐density polyethylene and its blend with polyamide 6

Graft copolymerization of low‐density polyethylene (LDPE) with a maleic anhydride (MAH) was performed using intermeshing corotating twin‐screw extruder in the presence of benzoyl peroxide (BPO). The LDPE/polyamide 6 (PA6) and LDPE‐g‐MAH/PA6 blends were prepared in 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 (FTIR) and scanning electron microcopy (SEM). The influence of the variation in temperature, BPO and MAH concentration, and temperature on the grafting degree and on the melt viscosity was studied. The grafting degree increased appreciably up to about 0.45 phr and then decreased continuously with an increasing BPO concentration. According to the FTIR analysis, it was found that the amount of grafted MAH on the LDPE chains was ～5.1%. Thermal analysis showed that melting temperature of the graft copolymers decreases with increasing grafting degree. In addition to this, loss modulus (E″) of the copolymers first increased little with increasing grafting and then obviously decreased with increasing grafting degree. Furthermore, the results revealed that the tensile strength of the blends increased linearly with increasing PA6 content. The results of SEM and mechanical test showed that the blends have good interfacial adhesion and good stability of the phase structure, which is reflected in the mechanical properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 267–275, 2010     

Radiation-induced graft polymerization of maleic acid and maleic anhydride onto ultra-fine powdered styrene–butadiene rubber (UFSBR)

The functionalization of ultra-fine powdered styrene–butadiene rubber (UFSBR) was carried out using gamma radiation-induced graft polymerization of maleic acid (MA) and maleic anhydride (MAH), respectively. It was found that the graft yield of MA onto UFSBR increased rapidly up to the peak and then decreased with increasing MA content. Moreover, the peak shifted to the direction of lower MA content with increasing absorbed dose. Similarly, there was the peak of graft yield with increasing MAH content for grafting of MAH onto UFSBR, whereas the peak of graft yield was achieved at 10 wt% MAH content at different absorbed doses. On the other hand, increasing absorbed dose and decreasing monomer contents are useful to improve the graft efficiency of MA and MAH. At high dose and low monomer content, the graft yield of MAH onto UFSBR is higher than that of MA. FTIR spectra confirmed that both MA and MAH can be grafted successfully onto the UFSBR under gamma irradiation, respectively. Comparing with maleation of rubber by melt grafting, the graft yield of MAH on UFSBR is higher, which can be attributed to the network structure and nanometer size of UFSBR as well as high energy provided by radiation.     

Graft copolymerization of maleic anhydride/styrene onto isotactic polypropylene using supercritical CO2

The free‐radical grafting of maleic anhydride (MAH) and styrene (St) onto isotactic polypropylene (iPP) was studied by thermal decomposition of dicumyl peroxide (DCP) using supercritical CO₂ as a solvent and swelling agent. Several effects of molar ratio of monomer, soaking temperature and time, reaction time, and reaction pressure on the graft degree were discussed. It was found that the addition of St to the grafting system as a comonomer could significantly enhance the graft degree of the grafted PP. Under the optimal reaction condition, the maximum of iPP grafting MAH and St in supercritical CO₂ medium was 10.58%. The chemical structures and properties of grafting copolymers were characterized by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The results showed that the supercritical CO₂ method had noticeable advantages over the existed method when compared, such as a lower temperature, a higher graft degree, easy separation, and environmentally benign. Copyright © 2007 John Wiley & Sons, Ltd.     

Ultrahigh‐molecular‐weight‐polyethylene‐fiber surface treatment by electron‐beam‐irradiation‐induced graft polymerization and its effect on adhesion in a styrene–butadiene rubber matrix

Aiming to develop a high‐performance fiber‐reinforced rubber from styrene–butadiene rubber (SBR), we applied a special technique using electron‐beam (EB)‐irradiation‐induced graft polymerization to ultrahigh‐molecular‐weight‐polyethylene (UHMWPE) fibers. The molecular interaction between the grafted UHMWPE fibers and an SBR matrix was studied through the evaluation of the adhesive behavior of the fibers in the SBR matrix. Although UHMWPE was chemically inert, two monomers, styrene and N‐vinyl formamide (NVF), were examined for graft polymerization onto the UHMWPE fiber surface. Styrene was not effective, but NVF was graft‐polymerized onto the UHMWPE fibers with this special method. A methanol/water mixture and dioxane were used as solvents for NVF, and the effects of the solvents on the grafting percentage of NVF were also examined. The methanol/water mixture was more effective. A grafting percentage of 16.4% was the highest obtained. This improved the adhesive force threefold with respect to that of untreated UHMWPE fibers. These results demonstrated that EB irradiation enabled graft polymerization to occur even on the inert surface of UHMWPE fibers. However, the mechanical properties of the fibers could be compromised according to the dose of EB irradiation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2595–2603, 2004     

Ultraviolet grafting of methacrylic acid and acrylic acid on high‐density polyethylene in different solvents and the wettability of grafted high‐density polyethylene. I. Grafting

Methacrylic acid (MAA) and acrylic acid (AA) were grafted onto high‐density polyethylene (PE) with UV initiation and a range of solvents. With acetone as the solvent, MAA was more easily grafted onto PE when the photoinitiator benzophenone was precoated on PE than when it was dissolved in the monomer solution. The grafting was faster in aliphatic solvents than in polar solvents or a UV‐adsorbing aromatic solvent (toluene). Acetone itself could initiate the photografting of both MAA and AA onto PE when it was mixed with water. The extent of grafting of MAA onto PE showed a maximum when there was about 40% acetone in the mixture. For AA, when the acetone/water concentration was 10%, the extent of grafting increased rapidly with the irradiation time. At higher acetone concentrations, the extent of grafting was low. Atomic force microscopy images showed that the surface topography of PE grafted with MAA in acetone/water was quite different from that obtained when the grafting was performed in other organic solvents. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 253–262, 2004     

Grafting of maleic anhydride on poly(L-lactic acid). Effects on physical and mechanical properties

Maleic Anhydride (MAH) was grafted onto poly(L-lactic acid) (PLLA) in the presence of dicumyl peroxide (DCP) as a radical initiator. The effect of the MAH and DCP concentrations on the grafting and the physical and mechanical properties of PLLA films were investigated. The glass transition temperature and crystallinity significantly decreased with addition of MAH. The thermal decomposition of the PLLA films was affected by the MAH content while the mechanical properties were almost unchanged. A slight increase in molecular weight was found, which could be attributed to either the MAH branching reaction or a possible crosslinking reaction between the PLLA chains increasing the chain entanglements.     

Radical grafting from glass fiber surface: Graft polymerization of vinyl monomers initiated by azo groups introduced onto the surface

This paper describes the radical graft polymerization of vinyl monomers from glass fiber surface initiated by alkylazo groups introduced onto the fiber surface. The introduction of azo groups onto the glass fiber surface was achieved by reaction of isocyanate groups which were previously attached onto the surface with two kinds of azo initiators, 4,4′-azobis(4-cyanopentanoic acid) (ACPA) and 2,2′-azobis(2-cyanopropanol) (ACP). The amounts of surface azo groups introduced by ACPA and ACP were both determined to be 1.3 × 10⁻⁵ mol g⁻¹ by nitrogen analysis. The radical graft polymerization of methyl methacrylate (MMA) was found to be initiated in the presence of the glass fiber having surface azo groups. During the polymerization, part of resultant poly(MMA) grafted onto the fiber surface through propagation of the polymer from the surface radicals produced by the decomposition of the azo groups. The percentage of grafting of poly(MMA) reached 48.1% after 24 h. The graft polymerizations of other monomers, such as styrene, N-vinylcarbazole, and acrylic acid, were also initiated by the surface azo groups, and the corresponding polymer effectively grafted onto the surface. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2121–2128, 1999     

Radical graft polymerization of vinyl monomers onto nanoparticles in ionic liquid initiated by azo groups introduced onto the surface

The radical graft polymerization of vinyl monomers, such as styrene and methyl methacrylate, initiated by azo groups introduced onto silica nanoparticle and carbon black surfaces in room temperature ionic liquid (IL) were investigated. In this work, 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([C₄mim][PF₆]) was used as IL. The percentage of polystyrene and poly(methyl methacrylate) grafting onto silica nanoparticle and carbon black increased with increasing reaction time. The percentage of grafting in IL was much larger than that in 1,4‐dioxane. The molecular weight of polystyrene grafted onto the silica surface in IL was almost equal to that in 1,4‐dioxane. The result indicates that the amount of grafted polystyrene in IL is five times that in 1,4‐dioxane. This may be due to the fact that lifetime of the surface radical formed by the group of azo is prolonged because of high viscosity of IL. Therefore, the surface azo groups were effectively used as initiating sites for the graft polymerization. In addition, the reduction of waste solvent was achieved by use of IL as reaction solvent, because unreacted monomer could be removed under vacuum after the reaction and the reuse of IL was easily achieved. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1143–1149, 2007     

聚β-羟基丁酸酯辐照接枝顺丁烯二酸酐及产物表征

探索了一种提高聚β羟基丁酸酯(PHB)热稳定性的方法,即用60Coγ射线辐照对PHB进行顺丁烯二酸酐(MAH)的接枝,采用1HNMR、13CNMR、TGA、DSC、XRD等方法对辐照接枝产物进行了表征.1HNMR、13CNMR谱图结果表明MAH单体接枝到了PHB上.TGA测试表明,辐照接枝产物的热稳定性显著提高,如接枝率为0.52%的样品热分解温度提高了36K.DSC研究表明辐照接枝产物的熔融温度和结晶温度均降低.此外,由于引入极性单体顺丁烯二酸酐,接枝产物的结晶度降低,同时亲水性提高.     

Dual monomer grafting of styrene and maleic anhydride onto model hydrocarbon substrates

Styrene and maleic anhydride (MAn) were successfully grafted, alone and simultaneously, onto various model hydrocarbon substrates at 180 °C with 2,5‐dimethyl‐2,5‐di‐(t‐butyl peroxy)hexane (L101) as a free‐radical initiator. Dodecane, 1‐dodecene, and 2,6,10,14‐tetramethylpentadecane were selected as model compounds to investigate the effects of terminal unsaturation and branching on grafting and crosslinking. These compounds were chosen to mimic the aforementioned microstructural characteristics that are commonly observed in polyethylene. The results demonstrate that terminal unsaturation increases the amount of crosslinked material in the presence of L101. With respect to grafting, for the single monomer systems, MAn prefers to graft as single saturated units, whereas styrene prefers to graft as long chains of polystyrene oligomers. However, when both monomers are grafted simultaneously, graft yields are drastically reduced because of a propensity for the two monomers to form a styrene–maleic anhydride copolymer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2456–2468, 2000     

In-situ monitoring by fibre-optic NIR spectroscopy and rheometry of maleic anhydride grafting to polypropylene in a laboratory scale reactive extruder

The graft copolymerisation of maleic anhydride (MAH) onto polypropylene (PP) has been studied in situ by interfacing a laboratory scale mini-extruder/processor with a near-infrared (NIR) spectrometer via a fibre optic link. Apparent viscosity was measured simultaneously with the NIR spectra. The graft reaction was carried out at several temperatures with and without the initiator, dicumyl peroxide (DCP). Analysis of the NIR spectra showed the reaction to be first order with respect to MAH, and that the graft reaction rate was not affected by the presence of DCP. However, DCP caused a large increase in chain scission reactions leading to a dramatic drop in apparent viscosity. In the absence of DCP, scission reactions occurred at a slower rate and the apparent viscosity remained steady, after an initial drop, for about 15 min during the early part of the reaction. We suggest that a possible explanation for this might be a “repair mechanism” involving the reaction of two PP macro-radicals with a single MAH moiety, thus maintaining the molecular weight. Once the concentration of MAH drops, this reaction becomes less significant and scission reactions dominate.     

Photografting of polymers onto nanosized silica surface initiated by eosin moieties immobilized onto the surface

The photograft polymerization of various vinyl monomers onto nanosized silica surfaces was investigated. It was initiated by eosin moieties introduced onto the silica surface. The preparation of the silica with eosin moieties was achieved by the reaction of eosin with benzyl chloride groups on the silica surface.These were introduced by the reaction of surface silanol groups with 4‐(chloromethyl)phenyltrimethoxysilane in the presence of t‐butyl ammonium bromide as a phase‐transfer catalyst. The photopolymerization of various vinyl monomers, such as styrene, acrylamide, acrylic acid, and acrylonitrile was successfully initiated by eosin moieties on the silica surface in the presence of ascorbic acid as a reducing agent and by oxygen. The corresponding polymers were grafted from the silica surface. The grafting efficiency (percentage of grafted polymer to total polymer formed) in the photoinitiation system was much larger than that in the radical polymerization initiated by surface radicals; these radicals were formed by the thermal decomposition of azo groups introduced onto the silica surface. It was found that the polymer‐grafted silica gave stable dispersions in good solvents of grafted polymer and the wettability of the surfaces can be easily controlled by grafting of polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 600–606, 2005     

A novel approach to synthesis of functional CPVC and CPE or graft copolymers—in situ chlorinating graft

A new process of graft copolymerization of poly(vinyl chloride) (PVC) and polyethylene (PE) with other monomers was developed. The grafted chlorinated poly(vinyl chloride) (CPVC) and chlorinated polyethylene (CPE) were synthesized by in situ chlorinating graft copolymerization (ISCGC) and were characterized. Convincing evidence for grafting and the structure of graft copolymers was obtained using FT‐IR, ¹H‐NMR, gel permeation chromatography (GPC), and the vulcanized curves. Their mechanical properties were also measured. The results show that the products have different molecular structure from those prepared by other conventional graft processes. Their graft chains are short, being highly branched and chlorinated. The graft copolymers have no crosslinking structure. The unique molecular structure will make the materials equipped with special properties. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis and morphology of polyethylene chains grafted onto the surface of crosslinked polystyrene microspheres

The bifunctional comonomer 4‐(3‐butenyl) styrene was used to synthesize crosslinked polystyrene microspheres (c‐PS) with pendant butenyl groups on their surface via suspension copolymerization. Polyethylene chains were grafted onto the surface of c‐PS microspheres (PS‐g‐PE) via ethylene copolymerizing with the pendant butenyl group on the surface of the c‐PS microspheres under the catalysis of metallocene catalyst. The composition and morphology of the PS‐g‐PE microspheres were characterized by means of Fourier transform infrared spectroscopy, Fourier transform Raman spectroscopy, X‐ray photoelectron spectroscopy, and field‐emission scanning electron microscopy. It is possible to control the content of PE grafted onto the surface of c‐PS microspheres by varying the polymerization time or the initial quantity of pendant butenyl group on the surface of c‐PS microspheres. Investigation on the morphology and crystallization behavior of grafted PE chains showed that different surface patterns could be formed under various crystallization conditions. Moreover, the crystallization temperature of PE chains grafted on the surface of c‐PS microspheres was 6 °C higher than that of pure PE. The c‐PS microspheres decorated by PE chains had a better compatibility with PE matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4477–4486, 2007     

Grafting of polymers onto a carbon‐fiber surface by ligand‐exchange reaction of poly(vinyl ferrocene‐co‐vinyl monomer) with polycondensed aromatic rings of the surface

To improve the surface of carbon fiber, the grafting reaction of copolymer containing vinyl ferrocene (VFE) onto a carbon‐fiber surface by a ligand‐exchange reaction between ferrocene moieties of the copolymer and polycondensed aromatic rings of carbon fiber was investigated. The copolymer containing VFE was prepared by the radical copolymerization of VFE with vinyl monomers, such as methyl methacrylate (MMA) and styrene, using 2,2′‐azobisisobutyronitrile as an initiator. By heating the carbon fiber with poly(VFE‐co‐MMA) (number‐average molecular weight: 2.1 × 10⁴) in the presence of aluminum chloride and aluminum powder, the copolymer was grafted onto the surface. The percentage of grafting reached 46.1%. On the contrary, in the absence of aluminum chloride, no grafting of the copolymer was observed. Therefore, it is considered that the copolymer was grafted onto the carbon‐fiber surface by a ligand‐exchange reaction between ferrocene moieties of the copolymer and polycondensed aromatic rings of carbon fiber. The molar number of grafted polymer chain on the carbon‐fiber surface decreased with increasing molecular weight of poly(VFE‐co‐MMA) because the steric hindrance of grafted copolymer on the carbon‐fiber surface increases with increasing molecular weight of poly(VFE‐co‐MMA). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1868–1875, 2002     

Graft copolymerization kinetics of acrylic acid onto the poly(ethylene terephthalate) surface by atmospheric pressure plasma inducement

After one atmospheric pressure plasma treatment of poly(ethylene terephthalate) (PET) film, acrylic acid (AAc) in aqueous solution was successfully graft‐copolymerized onto PET films. The effects of reaction time, AAc monomer concentration and reaction temperature on grafting behavior of AAc were systematically studied. Possible reaction kinetics of plasma‐induced graft copolymerization, starting from initial hydroperoxide decomposition, were proposed. Through the Arrhenius analysis about graft copolymerization kinetics of AAc monomers on PET surface, it was revealed that the activation energies of decomposition, propagation and termination were 98.4, 63.5, and 17.5 kJ/mol, respectively. The temperature around 80 °C was favorable not only for the formation of oxide radicals through the thermal decomposition of hydroperoxide on PET surface but also for the extension of graft copolymer chain through direct polymer grafting. Poly(acrylic acid) (PAAc) grains grafted onto PET surfaces possessed relatively uniform size and both PAAc grain size and surface roughness increased with increasing the grafting degree of AAc. The increase of grain size with increasing grafting degree results from the possibility of forming long chain graft copolymers and their shielding of reactive sites. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1594–1601, 2008