Graft copolymerisation of N‐vinyl pyrrolidone onto polypropylene copolymer in melt: Effect of grafting on thermomechanical properties and paint adhesion

N‐vinyl pyrrolidone (NVP) was grafted onto a polypropylene copolymer (PP) in melt in a Brabender Plasticorder and single screw extruder. The effect of variation of dicumyl peroxide (DCP) and lupersol (LUP) concentrations alone and with 20 wt % NVP concentration in the Brabender Plasticorder on Melt Flow Index (MFI) and final torque values was studied. Variation of NVP concentration (1–10 wt %) at a fixed DCP concentration on percent grafting (G) and MFI was also studied in the single screw extruder. The graft copolymers (PP‐g‐NVP) obtained by reaction of PP with NVP were soxhlet extracted with isopropanol to remove homopolymer, dried, and finally characterized by Fourier transform infrared (FTIR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The PP‐g‐NVP (0–30 wt %) was used as an additive with PP, extruded in the single screw extruder, molded, and the mechanical properties and paint adhesion was measured. MFI values increased and torque values decreased with an increase in initiator concentration, indicating the dominance of the peroxide‐initiated scission reaction over grafting. DCP gave higher grafting compared to LUP. When NVP concentration was increased, MFI values increased initially due to more scission, and then decreased, indicating more graft copolymer formation. Mechanical properties increased by incorporation of PP‐g‐NVP as an additive than PP‐g‐NVP alone. Paint adhesion increased by the presence of PP‐g‐NVP as additive especially with polyurethane primer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2173–2180, 2003     

Preparations and properties of thermosensitive terpolymers of N‐isopropylacrylamide,sodium 2‐acrylamido‐2‐methyl‐propanesuphonate,and N‐tert‐butylacrylamide

Terpolymers based on N‐isopropylacrylamide, sodium 2‐acrylamido‐2‐methyl‐propanesulfonate, and N‐tert‐butylacrylamide were synthesized by free‐radical copolymerization with 2,2′‐azobisisobutyronitrile as an initiator. The lower critical solution temperatures (LCSTs) of the linear polymer aqueous solutions were determined by the measurement of the transmittance on UV at different temperatures. The influence of the polymer concentration, polymer composition, and ionic strength on the LCSTs of the linear polymers was investigated. The LCST decreased with increases in the hydrophobic monomer N‐tert‐butylacrylamide, polymer concentration, and ionic strength. The phase transition became sharp when the polymer concentration and ionic strength increased. Meanwhile, the crosslinked hydrogels were prepared with the same recipe used for the linear terpolymers, but a crosslinker was added to the reaction system. The swelling ratios of the hydrogels at various temperatures and salt solutions were determined. The hydrogels possessed both high swelling ratios and thermosensitivity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Graft polymerization of acrylic acid onto polypropylene monofilament by RF plasma

Plasma‐induced graft polymerization of acrylic acid onto polypropylene monofilament was carried out to introduce carboxyl groups on its surface. The monofilament was treated with oxygen plasma to create hydroperoxide groups and subsequent graft polymerization of acrylic acid on exposed filament was carried out. An increase in the plasma power led to higher graft levels. It was observed that the hydroperoxide build up on PP surface follows linear increase with the increase in the plasma treatment time only up to 180 s beyond which it slowed down significantly. The formation of oxygenated species was ascertained by X‐ray photoelectron spectroscopy, and the peroxide content was measured by the 2′‐diphenylpicrylhydrazyl (DPPH) estimation. The grafting was observed to be considerably influenced by the plasma exposure time, plasma power, reaction temperature, monomer concentration and the storage temperature. A maximum in the degree of grafting was observed at 40% monomer concentration beyond which grafting tended to decrease very fast. The grafting was also found to be maximum at 50°C followed by a sharp decrease, subsequently. The storage of the exposed filament at ?80°C led to the identical grafting all along the 16 days. However, the storage at 25°C showed significant reduction in the degree of grafting. The atomic force microscopy showed that surface morphology is transformed into a nonhomogeneous one after the plasma exposure, but tends to flatten out after the grafting process in the form of globular structures. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Velocity measurements on a polypropylene melt during extrusion through a flat coat‐hanger die

An experimental investigation of various flow regimes observed during the extrusion of a polypropylene melt through a flat coat‐hanger die by laser‐Doppler velocimetry (LDV) is presented. LDV measurements of the velocity profiles across the gap of the die at various locations along the die reveal three different extrusion regimes. At small wall shear stresses, the velocity profiles can be fitted by symmetrical curves with the velocities becoming zero at the die walls. These profiles are not uniformly distributed along the die. An increase of the wall shear stress reveals a second flow regime characterized by a uniform distribution of the velocity profiles along the die. As the wall shear stress is increased even further, a third flow regime characterized by wall slip on the glass windows is observed. This flow regime is systematically characterized by measurements of the slip velocities at various temperatures and throughputs. The maximum velocities along the die are taken to assess the uniformity of flow which decisively influences the thickness of the extruded film. By measuring velocity profiles, at different throughput, and temperatures, the conditions for constant velocities along the die were determined. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Graft copolymerization of methyl acrylate onto silk sericin initiated by tert‐butyl hydroperoxide

A novel redox system, tert‐butyl hydroperoxide (TBHP)–silk sericin (SS), was used to initiate the graft copolymerization of methyl acrylate (MA) onto silk sericin in an aqueous medium. The graft copolymer, consisting of nanoparticles with a fine core–shell structure, was characterized using Fourier transfer infrared spectroscopy. The effects of the concentrations of MA and TBHP, reaction temperature and time on the grafting parameters of the copolymerization were studied in detail. In terms of grafting percentage and grafting efficiency, the optimum reaction conditions were obtained as follows: [MA] = 0.465 mol L^?1, [TBHP] = 3.884 × 10^?4 mol L^?1, T = 80 °C, t = 150 min. Transmission electron microscopy images of the particles showed a core–shell morphology, where poly(methyl acrylate) cores were covered with SS shells. A possible initiation mechanism is proposed. Copyright © 2006 Society of Chemical Industry     

Graft polymerization of acrylonitrile onto starch‐coated polyethylene film surfaces

Starch‐coated polyethylene (PE) films were prepared by immersing PE in a hot, jet cooked solution of starch. They were allowed to react with acrylonitrile (AN) in the presence of ceric ammonium nitrate initiator, and the graft polymerization that occurred produced starch‐g‐polyacrylonitrile (PAN) coatings that contained about 25 wt % grafted PAN. The starch‐g‐PAN coatings tightly adhered to the PE film surfaces. When grafted starch coatings were wetted with water and the surfaces vigorously rubbed, less than 20% of the coating was removed. The fact that PAN‐grafted coatings were not removed with boiling water provided further evidence for their strong adherence. When starch was removed from the coating by acid hydrolysis, the residual grafted PAN still remained adsorbed on the PE surface. Because the grafted coating was completely removed by treatment with refluxing 0.7N sodium hydroxide, there is apparently no chemical bonding between starch‐g‐PAN and PE. The dimensional changes associated with the evaporation of water from these PAN‐grafted coatings caused the films to curl during drying. Because the final shape of these coated films depends upon the presence or absence of water in the surrounding environment, these films may be considered to be a type of stimulus‐responsive polymer. Attempts to graft polymerize methyl methacrylate and methyl acrylate onto starch‐coated PE surfaces, under conditions similar to those used with AN, were unsuccessful. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3323–3328, 2003     

Graft copolymerization of N‐isopropylacrylamide onto poly(vinyl chloride)

Poly(vinyl chloride) (PVC) was dehydrochlorinated in alkali solution and then grafted with N‐isopropylacrylamide (NIPAM) using benzoyl peroxide as an initiator under a nitrogen atmosphere. The results show that grafting of NIPAM onto dehydrochlorinated PVC (DHPVC) by means of chemical initiation is easily performed. The influence of various reaction conditions such as NIPAM concentration, reaction time, initiator concentration, and PVC content on the grafting copolymerization was investigated. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1234–1241, 1999     

Physical gels of [BMIM][BF4] by N‐ tert‐butylacrylamide/ethylene oxide based triblock copolymer self‐assembly: Synthesis,thermomechanical, and conducting properties

We report a strategy to prepare and characterize mechanically robust, transparent, thermoreversible physical gels of an ionic liquid 1‐butyl‐3‐methylimidazolium tetrafluoroborate, [BMIM][BF₄], to harness its good ionic conductivity and electrolytic properties for solid‐state electrolyte and lithium ion battery applications. Physical gels are prepared using a triblock copolymer comprising central polyethylene oxide block that is soluble in [BMIM][BF₄] and the end blocks, poly(N‐tert‐butylacrylamide), that are insoluble in [BMIM][BF₄]. Transparent, strong, physical ion‐gels with significant mechanical strength can be formed at low concentration of the triblock copolymer (～5 wt %), unlike previous reports in which chemical gels of [BMIM][BF₄] are obtained at very high polymer concentration. Our gels are thermoreversible and thermally stable, showing 1–4% weight loss up to 200°C in air. Gelation behavior, mechanical properties, and ionic conductivity of these ion‐gels can be easily tuned by varying the concentration or N‐tert‐butylacrylamide block length in the triblock copolymer. These new non‐volatile, reprocessable, mechanically robust, [BMIM][BF₄]‐based physical ion‐gels obtained from a simple and convenient preparation method are promising materials for solid‐state electrolyte applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Comparison of maleic anhydride grafting onto powder and granular polypropylene in the melt by reactive extrusion

The grafting of powder and granular polypropylene (PP) with maleic anhydride (MA) was investigated in a reactive extrusion process with dicumyl peroxide (DCP) as an initiator. The effects of the MA and DCP contents in the feed on grafting were investigated. Under the experimental conditions applied in this study, the grafted monomer unit content was varied from 0.023 to 0.5%. The MA grafting efficiency of powder PP was higher than that obtained for the granular form of PP. In general, the grafting degree first increased with the MA or DCP content in the feed, then reached a maximum value, and finally decreased because of several possible alternative reactions during the grafting. The grafting of powder PP was more successful because of better initial mixing and less diffusional resistance during the grafting. An increase in the MA content in the feed caused significant reductions in the melt‐flow index of the graft copolymers. The results obtained with Fourier transform infrared, differential scanning calorimetry, and X‐ray powder diffraction analyses indicated that the structure, macrotacticity, crystallinity, crystallization, and thermal behavior of PP changed with grafting and depended on the grafting degree. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3675–3684, 2004     

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     

Preparation and Swelling Properties of Temperature‐Sensitive Semi‐Interpenetrating Polymer Networks Composed of Poly[(N‐tert‐butylacrylamide)‐co‐acrylamide] and Hydroxypropyl Cellulose

Summary: Temperature‐responsive hydrogels based on linear HPC and crosslinked P(NTBA‐co‐AAm) were prepared by the semi‐IPN technique. The structure of these semi‐IPN hydrogels was investigated by FT‐IR spectroscopy. An increase in normalized band ratios (A₂₉₈₀/A₁₆₆₅) was observed with increasing HPC content in the initial mixture. The swelling kinetics and water transport mechanism of these semi‐IPN hydrogels were examined and their temperature responsive behaviors were also investigated by measuring equilibrium swelling ratios and pulsatile swelling experiments. The results showed that these semi‐IPN hydrogels underwent a volume phase transition between 18 and 22 °C irrespective of the amounts of MBAAm and HPC. However, below the volume phase transition temperature, their equilibrium swelling ratios were affected by the amount of MBAAm and HPC. The pulsatile swelling experiments indicated that the lower the MBAAm and the higher HPC contents in semi‐IPN hydrogels the faster the response rate temperature change.

Equilibrium swelling ratios of the semi‐IPN P(NTBA‐co‐AAm)/HPC hydrogels in water shown as a function of temperature.     

Irradiation‐induced surface graft polymerization onto calcium carbonate nanoparticles and its toughening effects on polypropylene composites

Nano‐sized calcium carbonate was pretreated with silane coupling agent and then mixed with butyl acrylate that is of larger amount than the nanoparticles. Under γ‐irradiation, graft polymerization occurred on the nanoparticle surface, forming a nanocomposite structure consisting of grafted poly(butyl acrylate) (PBA), homopolymerized PBA, and the segregated nanoparticles. It was found that the silane pretreatment significantly promoted the graft reaction. When the grafted nano‐CaCO₃ particles were melt compounded with polypropylene (PP), an obvious synergistic effect, offered by (i) the chemical bonding between the elastomer type grafted PBA and nano‐CaCO₃ and (ii) the deliberately introduced thick interlayer mainly constructed by the homopolymerized PBA, led to a significant increase in notch impact strengths and elongation to break of PP at a rather low content of nano‐CaCO₃. Meanwhile, the tensile stiffness of the composites was also slightly increased and the yielding strength of the composites was almost unchanged. The results are different from those with conventional rubber‐toughened plastics, in which the improvement of ductility is acquired at high additive fraction and a great expense of strength performance. POLYM. ENG. SCI., 45:529–538, 2005. © 2005 Society of Plastics Engineers     

聚己内酯的熔体流动性能和挤出胀大

应用熔体流动速率仪,在温度为90～140℃和载荷为2.16～12.50 kg的条件下,考察了温度、表观剪切速率(γα)及管壁剪切应力((Τ)R)对聚己内酯(PCL)熔体流动性能和挤出胀大比(B)的影响.结果表明:在实验条件下,PCL熔体的剪切流动基本服从幂律定律.表观剪切黏度ηa与绝对温度的关系符合Arrhenius方程,ηa随着γa或ΤR的增加而非线性减小.B随着温度的升高而非线性降低,随着γa或(Τ)R的增加而非线性增大,达到最大值后B则下降.     

Investigation of radiation‐grafted and radiation‐modified N‐vinyl‐2‐pyrrolidone onto polypropylene film

The radiation‐induced graft copolymerization of N‐vinyl‐2‐pyrrolidone (NVP) onto polypropylene films was investigated using the mutual method. The grafted polymer was modified with prepared α,β‐unsaturated nitrile (Scheme 1 ). The water uptake of the grafted and modified grafted films was found to increase with the degree of grafting. It was observed that the swelling behavior of the modified grafted films with α‐cyano‐β‐phenyl crotononitrile improved more than that of the film grafted and modified grafted with α‐cyano‐β‐(2‐thienyl)crotononitrile or α‐cyano‐β‐(2‐pyridyl)crotononitrile. The modification process for the grafted substrate was confirmed by IR spectroscopy. No significant improvement was observed in thermal stability for the modified grafted films compared to the grafted films. Scanning electron microscopy (SEM) of the grafted and modified grafted membranes heated to 150°C showed change in the structure and morphology. Improvement in the hydrophilicity and morphology of these membranes with carbonitriles may increase the permeability of those membranes for some practical applications.     

A reactive extrusion process for the free radical grafting of silanes onto polypropylene: Effects of processing conditions and properties of water cross‐linked silane‐grafted polypropylene

Silane grafting and water cross‐linking of polypropylene (PP) are a recent method to modify its properties, such as melt strength, heat, and chemical resistance. This work aims at grafting silanes onto PP by reactive extrusion. The occurrence of the grafting of silane onto PP was confirmed by Fourier transform infrared (FTIR) and a method based on FTIR was developed to quantify the amount of polymerized silane and that of silane grafted onto PP. The molar mass of the silane‐grafted PP and its melt viscosity were also measured. A multiobjective optimization strategy was used to study the effects of processing conditions on the quality of the silane‐modified PP. It was concluded that to maximize the amount of silane grafted on PP and minimize the amount of polymerized silane and the decrease in PP chain scission, screw speed and barrel temperature should be low and feed rate high. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

Graft copolymerization of itaconic acid onto chitin and its properties

Modification of chitin by grafting with itaconic acid (IA) was carried out using potassium persulfate as redox initiator. In complimentary experiments, grafting was performed using γ‐radiation. Grafting was confirmed by FTIR spectroscopy. The effect of monomer concentration, initiator concentration and copolymerization temperature on the percentage of grafting were studied. The effect of radiation dose was also investigated. Values for percentages of grafting of up to 300 % were reached. It was observed that the percentage of grafting increased with increasing monomer concentration and showed a tendency to level off at IA concentration of 0.1 mol l^?1. The percentage of grafting increased with temperature up to 60 °C and then decreased. The solubility of the grafted chitin was studied in organic and inorganic solvents. The complexation of the grafted chitin with some cations, namely copper, nickel, cobalt, zinc and lead, was also investigated. The metal uptake was measured by UV spectroscopy. Thermogravimetric analysis of the grafted chitin was also studied. Copyright © 2004 Society of Chemical Industry     

Graft copolymerization of N‐vinyl‐2‐pyrrolidone onto sodium carboxymethylcellulose with azobisisobutyronitrile as the initiator

Graft copolymers of sodium carboxymethylcellulose with N‐vinyl‐2‐pyrrolidone were prepared in aqueous solutions with azobisisobutyronitrile as the initiator. The graft copolymers [sodium carboxymethylcellulose‐g‐poly(N‐vinyl‐2‐pyrrolidone)] were characterized with Fourier transform infrared spectroscopy, elemental analysis, nuclear magnetic resonance spectroscopy, differential scanning calorimetry, and scanning electron microscopy. The grafting parameters, including the graft yield of the graft copolymer and the grafting efficiency of the reaction, were evaluated comparatively. The effects of reaction variables such as the time, temperature, and monomer and initiator concentrations on these parameters were studied. The graft yield and grafting efficiency increased and then decreased with increasing concentrations of N‐vinyl‐2‐pyrrolidone and azobisisobutyronitrile and increasing polymerization temperatures. The optimum temperature and polymerization time were 70°C and 4.30 h, respectively. Further changes in the properties of grafted sodium carboxymethylcellulose, such as the intrinsic viscosity, were determined. The overall activation energy for the grafting was also calculated to be 10.5 kcal/mol. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 936–943, 2007     

Effect of long‐chain branches of polypropylene on rheological properties and foam‐extrusion performances

The effect of modifying polypropylene by the addition of long‐chain branches on the rheological properties and performance of foam extrusion was studied. Three polypropylenes, two long‐chain‐branched polypropylenes and a linear polypropylene, were compared in this study. The modification was performed with a reactive‐extrusion process with the addition of a multifunctional monomer and peroxide. The rheological properties were measured with a parallel‐plate and elongational rheometer to characterize the branching degree. The change from a linear structure to a long‐chain‐branched nonlinear structure increased the melt strength and elasticity of polypropylene. Also, there was a significant improvement in the melt tension and sag resistance for branched polypropylenes. Foaming extrusion was performed, and the effect of the process variables on the foam density was analyzed with Taguchi's experimental design method. For this study, an L₁₈(2¹3⁵) orthogonal array was used on six parameters at two or three levels of variation. The considered parameters were the polypropylene type, the blowing agent type, the blowing agent content, the die temperature, the screw speed (rpm), and the capillary die length/diameter ratio. As a result, the most significant factor that influenced the foam density was the degree of long‐chain branching of polypropylene. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1793–1800, 2005     

Syntheses and properties of graft polymers of N‐substituted acrylamides onto EPDM

The graft polymerizations of N‐isopropylacrylamide (NIPAM) or N‐phenylacrylamide (NPAM) onto ethylene‐propylene‐diene terpolymer (EPDM) were carried out with benzoyl peroxide (BPO) as an initiator in toluene or THF. The structures of synthesized graft polymers, EPDM‐g‐N‐isopropylacrylamide (ENIPAM) and EPDM‐g‐N‐phenylacrylamide (ENPAM), were identified by infrared (IR) spectroscopy. The effects of monomer concentration, reaction time, and initiator concentration were investigated on the graft polymerization. The highest graft efficiency of NIPAM was obtained at 0.75 mol/L of NIPAM, 4 g of EPDM, 3 wt % of BPO, and 70°C for 48 h and that of NPAM did not much change up to 0.75 mol/L of NPAM, 4 g of EPDM, 3 wt % of BPO, and 70°C for 72 h. The thermal decomposition temperatures, wettabilities, and tensile strengths of ENIPAM and ENPAM all decreased with an increasing concentration of NIPAM and NPAM moiety in the corresponding polymers, respectively. The morphologies of ENIPAM and ENPAM after irradiation showed many gel particles as compared with those of ENIPAM and ENPAM before irradiation. The UV light and ⁶⁰Co γ‐ray resistances of ENIPAM and ENPAM were worse than those of EPDM due to carbonyl group in NIPAM and NPAM. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3259–3267, 1999     

Cellulose nanofibril‐reinforced polypropylene composites for material extrusion: Rheological properties

Polypropylene (PP) is not typically utilized in 3D printing material extrusion because PP shrinks and warps during the printing process. Cellulose nanofibrils (CNF) have the potential to make PP 3D printer processable and also enhance mechanical properties of PP printed parts. The rheological behavior of CNF‐PP composites during material extrusion requires study because it is different from injection molding and compression molding processes. This study revealed the effects of CNF contents (3 and 10 wt%) and maleic anhydride polypropylene (MAPP) coupling agent on the rheological properties of CNF–PP composites. Morphological analysis showed that CNF agglomerated during spray drying and a spherical structure was formed. Rheological tests showed that the elastic modulus, complex viscosity, viscosity, and transient flow shear stress of PP were increased by the addition of 10 wt% CNF, while the creep strain of PP was reduced. The damping factor and stress relaxation time remained the same when 10 wt% CNF was added to the PP. Incorporation of MAPP into the CNF–PP composites impacted the rheological properties of the CNF–PP composites. Flexural strength and modulus of PP were improved by 5.9% and 26.8% by adding 10 wt% CNF compared to the control. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers