Graft copolymers of microcrystalline cellulose as reinforcing agent for elastomers based on natural rubber

In the present study, free radical graft copolymerization of acrylic monomers and microcrystalline cellulose (MCC) was applied to develop a biopolymer for natural rubber reinforcements. The copolymerization was carried out in aqueous media. Cerium ammonium nitrate was employed as the initiator in the presence of nitric acid. Acrylic monomers used in the copolymer synthesis were ethyl acrylate (EA) and butyl acrylate (BA). Effects of monomer concentration, initiator concentration, polymerization time, and polymerization temperature on the obtained graft copolymers were investigated. The graft parameters were obtained by thermal gravimetric analysis method. The obtained copolymers (MCC‐g‐PEA, MCC‐g‐PBA) were characterized by attenuated total reflection, wide‐angle X‐ray diffraction, field‐emission electron microscopy, and thermal gravimetric analysis. In comparison to native MCC, better thermal stability of graft copolymers were observed. In addition, the graft copolymers reinforced natural rubber composites were produced, and sulfur was used as the vulcanizing agent. Their vulcanization and mechanical properties were characterized. Comparing to the native MCC reinforced natural rubber composites, the copolymers reinforced natural rubber composites shows improved mechanical properties, indicating the copolymer's potential application as rubber reinforcements. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43087.     

Natural rubber‐g‐methyl methacrylate/poly(methyl methacrylate) blends

The grafting of the methyl methacrylate (MMA) monomer onto natural rubber using potassium persulfate as an initiator was carried out by emulsion polymerization. The rubber macroradicals reacted with MMA to form graft copolymers. The morphology of grafted natural rubber (GNR) was determined by transmission electron microscopy and it was confirmed that the graft copolymerization was a surface‐controlled process. The effects of the initiator concentration, reaction temperature, monomer concentration, and reaction time on the monomer conversion and grafting efficiency were investigated. The grafting efficiency of the GNR was determined by a solvent‐extraction technique. The natural rubber‐g‐methyl methacrylate/poly(methyl methacrylate) (NR‐g‐MMA/PMMA) blends were prepared by a melt‐mixing system. The mechanical properties and the fracture behavior of GNR/PMMA blends were evaluated as a function of the graft copolymer composition and the blend ratio. The tensile strength, tear strength, and hardness increased with an increase in PMMA content. The tensile fracture surface examined by scanning electron microscopy disclosed that the graft copolymer acted as an interfacial agent and gave a good adhesion between the two phases of the compatibilized blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 428–439, 2001     

超声-微波共辐射法合成纤维素-MMA接枝共聚物

引言纤维素作为一种天然的可再生高分子材料,存在于丰富的绿色植物中,是自然界取之不尽用之不竭的清洁资源。因此,在煤、石油、天然气的储量日益减少的今天,纤维素可作为一种可持续发展的绿色资源来研究和开发。而且天然植物纤维资源丰富、价格低廉,并且具有较好的生物可降解性,在     

Graft copolymerization of methyl methacrylate from brominated poly(isobutylene‐co‐isoprene) via atom transfer radical polymerization

Commercial brominated poly(isobutylene‐co‐isoprene) (BIIR) rubber has been directly used for the initiation of atom transfer radical polymerization (ATRP) by utilizing the allylic bromine atoms on the macromolecular chains of BIIR. The graft copolymerization of methyl methacrylate (MMA) from the backbone of BIIR which was used as a macroinitiator was carried out in xylene at 85 °C with CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as a catalytic complex. The polymerization conditions were optimized by adjusting the catalyst and monomer concentration to reach a higher monomer conversion and meanwhile suppress macroscopic gelation during the polymerization process. This copolymerization followed a first‐order kinetic behavior with respect to the monomer concentration, and the number‐average molecular weight of the grafted poly(methyl methacrylate) (PMMA) increased with reaction time. The resultant BIIR‐graft‐PMMA copolymers showed phase separation morphology as characterized by atomic force microscopy, and the presence of PMMA phase increased the polarity of the BIIR copolymers. This study demonstrated the feasibility of using commercial BIIR polymer directly as a macromolecular initiator for ATRP reactions, which opens more possibilities for BIIR modifications for wider applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43408.     

Preparation,characterization, and properties of cellulose–polyacrylamide graft copolymers

Graft copolymers of acrylamide on cellulose materials (α‐cellulose 55.8%, DP 287.3) obtained from Terminalia superba wood meal and its carboxymethylated derivative (DS 0.438) were prepared using a ceric ion initiator and batch polymerization and modified batch polymerization processes. The extent of graft polymer formation was measured in graft level, grafting efficiency, molecular weight of grafted polymer chains, frequency of grafting as a function of the polymerization medium, and initiator and monomer concentrations. It was found that the modified batch polymerization process yielded greater graft polymer formation and that graft copolymerization in aqueous alcohol medium resulted in enhanced levels of grafting and formation of many short grafted polymer chains. Viscosity measurements in aqueous solutions of carboxymethyl cellulose‐g‐polyacrylamide copolymer samples showed that interpositioning of polyacrylamide chains markedly increased the specific viscosity and resistance to biodegradation of the graft copolymers. The flocculation characteristics of the graft copolymers were determined with kaolin suspension. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 913–923, 2003     

Graft copolymerization of methylmethacrylate with N‐substituted maleimide‐styrene copolymer by ATRP

Atom transfer radical polymerization (ATRP) was employed to prepare graft copolymers having poly(MBr)‐alt‐poly(St) copolymer as backbone and poly(methyl methacrylate) (PMMA) as branches to obtain heat resistant graft copolymers. The macroinitiator was prepared by copolymerization of bromine functionalized maleimide (MBr) with styrene (St). The polymerization of MMA was initiated by poly(MBr)‐alt‐poly(St) carrying bromine groups as macroinitiator in the presence of copper bromide (CuBr) and bipyridine (bpy) at 110°C. Both macroinitiator and graft copolymers were characterized by ¹H NMR, GPC, DSC, and TGA. The ATRP graft copolymerization was supported by an increase in the molecular weight (MW) of the graft copolymers as compared to that of the macroinitiator and also by their monomodal MW distribution. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Blends of poly(vinyl chloride) (PVC)/natural rubber‐g‐(styrene‐co‐methyl methacrylate) for improved impact resistance of PVC

To improve the mechanical properties of poly(vinyl chloride) (PVC), the possibility of combining PVC with elastomers was considered. Modification of natural rubber (NR) by graft copolymerization with methyl methacrylate (MMA) and styrene (St) was carried out by emulsion polymerization by using redox initiator to provide an impact modifier for PVC. The impact resistance, dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM) of St and MMA grafted NR [NR‐g‐(St‐co‐MMA)]/PVC (graft copolymer product contents of 5, 10, and 15%) blends were investigated as a function of the amount of graft copolymer product. It was found that the impact strength of blends was increased with an increase of the graft copolymer product content. DMA studies showed that NR‐g‐(St‐co‐MMA) has partial compatibility with PVC. SEM confirmed a shift from brittle failure to ductility with an increase graft copolymer content in the blends. The mechanical properties showed that NR‐g‐(St‐co‐MMA) interacts well with PVC and can also be used as an impact modifier for PVC. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1666–1672, 2004     

Factorial experimental design for graft copolymerization of styrene and methyl methacrylate onto styrene–butadiene rubber

The graft copolymerization of styrene (ST) and methyl methacrylate (MMA) onto styrene–butadiene rubber (SBR) latex prepared by seeded emulsion polymerization has been studied under various reaction conditions using cumene hydroperoxide redox initiator. The mechanism of graft copolymerization has been investigated. The synthesized graft copolymers were purified and then characterized by proton nuclear magnetic resonance (¹H NMR) analysis. A 2 2 fractional factorial experimental design was applied to study the effects of the process variables such as the amount of initiator and emulsifier, the presence or absence of chain‐transfer agent, ST to MMA ratio, monomer to rubber ratio, and reaction temperature on the grafting efficiency. The analysis of the results from the design showed the sequence of the main effect on the observed response of the grafting of ST and MMA onto SBR and that the amount of chain‐transfer agent had a significant effect. Transmission electron microscopy was used to study the morphology of the graft copolymers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2867–2874, 2006     

Synthesis of well‐defined comb‐like amphiphilic copolymers with protonizable units in the pendent chains: 1. Preparation of narrow polydispersity copolymers of methyl methacrylate and 2‐hydroxyethyl methacrylate by atom‐transfer radical polymerization

Well‐defined methyl methacrylate (MMA) and 2‐(trimethylsiloxy)ethyl methacrylate (Pro‐HEMA) copolymers were prepared by atom‐transfer radical polymerization(ATRP), using CuCl/2,2′‐bipyridine as catalytic system and p‐toluenesulfonyl chloride as initiator. ATRP process of MMA and Pro‐HEMA was monitored by ¹H NMR, and the kinetic curves of the MMA/Pro‐HEMA copolymerization were plotted in terms of the ¹H NMR data. At low content of Pro‐HEMA in the feed composition, the copolymerization can be well controlled with the molecular weight, polydispersity and the monomer distribution in the copolymer chain. With the increase of Pro‐HEMA content in the feed mixture, the composition of the final copolymer deviates from the composition of the feed mixture gradually, and gradient copolymers of MMA/Pro‐HEMA can be obtained. Through the hydrolysis process, well‐defined copolymers of MMA/HEMA were obtained from poly(MMA/Pro‐HEMA). Copyright © 2003 Society of Chemical Industry     

Factorial experimental design for grafting of vinyl monomers onto natural rubber latex

Graft copolymerization of styrene (St) and methyl methacrylate (MMA) in the presence of natural rubber latex using cumene hydroperoxide/tetraethylenepentamine redox initiator system was prepared at various process variables. The synthesized graft copolymers were purified and then characterized by Fourier transformed infrared spectroscopy analysis. A full 2⁴ factorial experimental design was applied to study the effect of various process variables on grafting efficiency. The following four independent variables considered to be mainly affecting the grafting efficiency were reaction temperature, rubber‐to‐monomer ratio, St‐to‐MMA ratio, and initiator amount used in the secondary polymerization. It was shown in this study that the reaction temperature significantly influenced the grafting efficiency, increasing as the temperature was increased. The amount of grafting increased with increasing rubber‐to‐monomer ratio and St‐to‐MMA ratio, whereas the amount of grafting decreased with increasing amount of initiator. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 455–463, 2004     

Synthesis and characterization of N‐vinyl pyrrolidone and cellulosics based functional graft copolymers for use as metal ions and iodine sorbents

To develop cost effective and eco friendly polymeric materials for enrichment and separation technologies, 1‐vinyl‐2‐pyrrolidone (N‐VP) was graft copolymerized onto cellulose, extracted from pine needles. Optimum conditions have been evaluated for the grafting of N‐VP onto cellulose and at these conditions it was also grafted onto cellulose phosphate, hydroxypropyl cellulose, cyanoethyl cellulose, and deoxyhydrazino cellulose. At the optimum grafting conditions for N‐VP, it was also cografted with maleic anhydride. Kinetics of radiochemical graft copolymerization has been studied and evaluation of the polymerization and grafting parameters as percent grafting, percent grafting efficiency, rate of polymerization, homopolymerization, and graft copolymerization have been evaluated. Graft copolymers have been characterized by elemental analysis, FTIR, and swelling studies. An attempt has been made to study sorption of some metal ions such as Fe²⁺ and Cu²⁺ and iodine on select graft copolymers to investigate selectivity in metal ion sorption and iodine sorption as a function of structural aspects of the functionalized graft copolymers to find their end uses in separation and enrichment technologies. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 373–382, 2005     

Ultrasound‐assisted emulsion polymerization of poly(methyl methacrylate‐co‐butyl acrylate): Effect of initiator content and temperature

In this study, we propose an efficient method for preparation of large scale, monodisperse poly(methyl methacrylate‐co‐butyl acrylate) latexes by application of the low power ultrasound irradiation. The effect of polymerization temperature and initiator concentration on the polymerization nature, particle size, and particle size distribution were investigated. Results indicated that the ultrasound pulses in the first minutes of polymerization increase instant free radical to monomer ratio as well mixing efficiency which led to higher monomer conversion, improved polymerization rate (especially at first 15 min of the reaction), and remarkable decrease in molecular weight distribution. Transmittance electron microscopy (TEM) and dynamic light scattering (DLS) revealed that the particle size and particle size distribution were significantly affected, particle size decreased, and more uniform particles were obtained. Dynamic mechanical thermal analysis also showed that the initiator concentration affected glass transition temperature (T_g) of the final copolymers and in the case of ultrasound‐assisted emulsion polymerization T_g was in a very good agreement with theoretical predictions for copolymerization. POLYM. ENG. SCI., 56:214–221, 2016. © 2015 Society of Plastics Engineers     

Thermal behavior of some homogeneously polymethyl methacrylate (PMMA)‐grafted high α‐cellulose products

The graft copolymerization of methyl methacrylate (MMA) onto high α‐cellulose was carried out homogeneously in an N,N‐dimethyl acetamide/lithium chloride solvent system by using benzoyl peroxide as radical initiator. The rate of grafting was evaluated as a function of concentrations of initiator and monomer, reaction time, and temperature. The grafted products were characterized with the help of infrared spectroscopy, whereas the thermal decomposition of optimum PMMA‐grafted high α‐cellulose was studied using TGA, DTG, and DTA techniques at two heating rates, 10 and 20°C/min, in nitrogen atmosphere in the range of room temperature to 650°C. Three major decomposition steps were identified and the relative thermal stabilities of the PMMA‐grafted high α‐cellulose products were assessed. The kinetic parameters for the three decomposition steps were estimated with the help of two well‐known methods. The thermal stability of the grafted products decreased with the increase of graft yield (GY). Crystallinity or peak intensity of wide‐angle X‐ray diffraction patterns decreased with the increase of GY. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3471–3478, 2004     

Effect of dimethyl sulfoxide on synthesis of thermoplastic cellulose‐Graft‐poly(l‐lactide) copolymer using ionic liquid as reaction media

In this study, ring‐opening graft polymerization of l ‐lactide onto cellulose was carried out homogeneously in ionic liquid (IL)/dimethyl sulfoxide (DMSO) co‐solvent as a reaction media. Through the effective control of high viscosity and steric hindrance caused by the interaction between the IL and the hydroxyl group of cellulose by adding DMSO as a co‐solvent, cellulose‐graft‐poly(l ‐lactide) (Cell‐g‐PLLA) copolymer with higher substitution efficiency was successfully prepared, at relatively low concentration of l ‐lactide. The maximum values of molar substitution, degree of lactyl substitution, and degree of polymerization of poly(l ‐lactide) in the copolymer were 3.76, 1.74, and 2.16, respectively, determined by ¹H‐NMR. The prepared cell‐g‐PLLA copolymers showed thermal plasticization with a glass transition temperature of 155°C. In addition, the thermal processibility could be improved as the amount of grafted PLLA in the copolymer increased. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41331.     

RAFT synthesis of cellulose‐g‐polymethylmethacrylate copolymer in an ionic liquid

We demonstrate for the first time the feasibility in conducting the graft copolymerization of methylmethacrylate (MMA) with cellulose by the means of the reversible addition‐fragmentation chain transfer (RAFT) polymerization in an ionic liquid [1‐N‐butyl‐3‐methylimidazolium chloride] (BMIMCl). Cellulose was first converted to a macromolecular chain transfer agent to which MMA was grafted by RAFT in BMIMCl. The success of the occurrence of different reactions was validated by elemental analyses, Fourier transform infrared and nuclear magnetic resonance spectroscopies. The results demonstrate that the MMA polymer chains were grafted onto the cellulose while the use of the ionic liquid as a reaction medium enhanced the polymerization rate to a moderate extent. Gel permeation chromatography analysis of poly(MMA) chains cleaved from the cellulose by acidic hydrolysis indicated low polydispersity indices (ca. 1.3) that were consistent with the “living” nature of the RAFT. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Graft copolymerization of p‐acryloyloxybenzoic acid and p‐methacryloyloxybenzoic acid onto isotactic polypropylene and their thermal properties: Part I

The polymerization and grafting of the monomers p‐acryloyloxybenzoic acid and p‐methacryloyloxybenzoic acid were studied. Poly(acryloyloxybenzoic acid) was obtained by γ‐radiation‐induced solution polymerization and bulk melt polymerization initiated by dicumyl peroxide. Poly(methacryloyloxybenzoic acid) could be obtained only by bulk melt polymerization. The graft copolymerization of the monomers onto isotactic polypropylene was carried out in bulk. The maximum grafting was reached in shorter times at higher temperatures, and it also increased with the concentration of the monomers in the reaction medium. The thermal and crystallization behavior of the graft copolymers was studied with differential scanning calorimetry and wide‐angle X‐ray diffraction. The graft copolymerization of p‐acryloyloxybenzoic acid did not have any influence on the formation of both α forms (monoclinic) of polypropylene, whereas p‐methacryloyloxybenzoic acid led to the α₂ form. The β‐crystalline modification (hexagonal) formed in poly(acryloyloxybenzoic acid)‐g‐polypropylene products at 185°C and at higher grafting temperatures and also in the second run of differential scanning calorimetry studies after fast cooling. The β form was not observed in graft copolymers of poly(methacryloyloxybenzoic acid). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Homogeneous graft copolymerization of chitosan with methyl methacrylate by γ‐irradiation via a phthaloylchitosan intermediate

The graft copolymerization of methyl methacrylate (MMA) onto chitosan was tried via a new protection‐graft‐deprotection procedure. Because the intermediate phthaloylchitosan was soluble in organic solvents, the graft copolymerization was carried out in a homogeneous system. Grafting was initiated by γ‐irradiation. The graft percentage extent was dependent on the irradiation dose and the concentration of MMA monomer, and copolymers with grafting above 100 % were readily prepared. The graft copolymers exhibited a high affinity not only for aqueous acid but also for some organic solvents. Differential scanning calorimetry measurements revealed the presence of a glass transition phenomenon, which could be ascribed to the poly(methyl methacrylate) side‐chains. Copyright © 2004 Society of Chemical Industry     

Ceric‐initiated free radical graft copolymerization of acrylonitrile onto kappa carrageenan

The polysaccharide, kappa carrageenan (kC), was modified using ceric‐initiated graft copolymerization of acrylonitrile (AN) under inert atmosphere in a homogeneous aqueous medium. Grafting was confirmed using FTIR spectroscopy, solubility test, elemental analysis, acid hydrolysis, and thermogravimetric analysis (TGA). kC‐graft‐poly(AN) products had a higher thermal stability than kC as revealed by TGA analysis. The polyacrylonitrile branches were isolated by acidic degradation of the carrageenan main chains and characterized by size exclusion chromatography (SEC). Residual monomers were not found by HPLC in graft copolymers stored even for longer periods. The effect of various factors affecting on grafting, i.e., concentration of the initiator, monomer, and polysaccharide as well as the reaction time and temperature were studied by conventional methods to achieve the optimum grafting parameters. The graft copolymerization reactions were kinetically investigated using semi‐empirical expressions and a suitable rate expression has been derived. According to the empirical rates of the polymerization and the graft copolymerization of AN onto kC backbone, the overall activation energy of the graft copolymerization reaction was estimated to be 20.96 kJ/mol. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and applicability of functionalized polyethylene with an ethylene/1,7‐octadiene copolymer

The copolymerization of ethylene and 1,7‐octadiene was carried out to synthesize polyethylene with unreacted vinyl groups. The prepared copolymer [poly (ethylene‐co‐1,7‐octadiene) (PEOD)] was epoxidized with peracetic acid, m‐chloroperbenzoic acid, or formic acid/H₂O₂. Of these, peracetic acid gave the best results. Epoxidized PEOD was subjected to a reaction with 2‐mercaptobenzimidazole and poly(L ‐lactic acid). The bromination of PEOD was also performed in the presence of a Br₂/HBr solution at room temperature. The brominated poly(ethylene‐co‐1,7‐octadiene) (PEOD‐Br) was used as a macroinitiator for atom transfer radical polymerization. The polymerization of styrene, butyl methacrylate, and glycidyl methacrylate was performed in bulk or solution at 120°C with a PEOD‐Br/CuBr/2,2′‐dipyridyl initiator system. The thermal properties of the graft copolymers and the efficiency of the graft polymerization were investigated. These graft copolymers have potential applications as interfacial modifiers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of sub‐micrometer core–shell rubber particles with 1,2‐azobisisobutyronitrile as initiator and deformation mechanisms of modified polystyrene under various conditions

BACKGROUND: Sub‐micrometer core‐shell polybutadiene‐graft‐polystyrene (PB‐g‐PS) copolymers with various ratios of polybutadiene (PB) core to polystyrene (PS) shell were synthesized by emulsion grafting polymerization with 1,2‐azobisisobutyronitrile (AIBN) as initiator. These graft copolymers were blended with PS to prepare PS/PB‐g‐PS with a rubber content of 20 wt%. The mechanical properties, morphologies of the core‐shell rubber particles and deformation mechanisms under various conditions were investigated. RESULTS: Infrared spectroscopic analysis confirmed that PS could be grafted onto the PB rubber particles. The experimental results showed that a specimen with a ‘cluster’ dispersion state of rubber particles in the PS matrix displayed better mechanical properties. Transmission electron micrographs suggested that crazing only occurred from rubber particles and extended in a bridge‐like manner to neighboring rubber particles parallel to the equatorial plane at a high speed for failure specimens, while the interaction between crazing and shear yielding stabilized the growing crazes at a low speed in tensile tests. CONCLUSION: AIBN can be used as an initiator in the graft polymerization of styrene onto PB. The dispersion of rubber particles in a ‘cluster’ state leads to better impact resistance. The deformation mechanism in impact tests was multi‐crazing, and crazing and shear yielding absorbed the energy in tensile experiments. Copyright © 2009 Society of Chemical Industry