Polyolefin blends
Somayeh Rafiei; Davood Soudbar; Minoo Sadri; Fatemeh Shafiei
Abstract
Thermoplastic vulcanizates (TPVs) were prepared based on polypropylene (PP) and polybutadiene rubber (PBR) at different PP/PBR compositions (70/30 and 60/40). PP-grafted-maleic anhydride (PP-g-MA) was introduced into the TPVs at different concentrations (10 and 20%). The compatibilizing effect of PP-g-MA ...
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Thermoplastic vulcanizates (TPVs) were prepared based on polypropylene (PP) and polybutadiene rubber (PBR) at different PP/PBR compositions (70/30 and 60/40). PP-grafted-maleic anhydride (PP-g-MA) was introduced into the TPVs at different concentrations (10 and 20%). The compatibilizing effect of PP-g-MA was demonstrated through cross-sectional morphology. PP-g-MA exhibited a suppressing impact on the coalescence of the rubber domains, leading to a finer and more uniform distribution of the PBR phase. Due to the higher rubber content, the compatibilizing effect was more pronounced for the 60/40 composition, which was on the averge of forming a co-continuous morphology. However, it was found that a higher PP-g-MA content is needed to effectively compatibilize the TPVs. Rheological results revealed opposing effects on the viscoelastic response of the system. However, the elastic response was intensified once higher content of PP-g-MA was used, suggesting its compatibilizing role. Dynamic mechanical analysis results proved the existence of opposing effects and revealed the profound compatibilizing effects of PP-g-MA, especially at higher content (20%). Izod impact strength exhibited moderate and notable enhancements in both TPV compositions by adding 10% and 20% of PP-g-MA, respectively, attributed to the highly increased compatibility of the PP/PBR TPVs, especially at higher levels of PP-g-MA content.
Characterization
Ahmed Hamdi
Abstract
Describing the solidification process is very important in polymer processing. In polypropylene (PP), the increase of viscosity, named stiffening or hardening, is determined by a rise in crystallinity. When PP flows in a channel or is stretched on a chill roll, the stress induces an anticipated crystallization ...
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Describing the solidification process is very important in polymer processing. In polypropylene (PP), the increase of viscosity, named stiffening or hardening, is determined by a rise in crystallinity. When PP flows in a channel or is stretched on a chill roll, the stress induces an anticipated crystallization and thus can lead to an unexpected solidification. This study explores how flow fields influence the crystallization behavior of PP. A controlled-stress rheometer was used to investigate the effect of short shear stress steps on crystallization kinetics. The results revealed that applying a stress step significantly increased the rate of crystallization compared to a non-stressed sample. This acceleration is attributed to the stress-induced orientation of macromolecules, which promotes nucleation. Furthermore, longer durations of applied stress led to a faster increase in viscosity, indicating a higher nucleation density with increasing stress exposure. A mastercurve approach validated the consistency of the model describing the stress-crystallization relationship. The calculated parameter relating to nucleation density confirmed a linear increase with stress duration, allowing estimation of the nucleation rate during shear.
Simulation & Modeling
Aamir Mustafa Shaikh; Pravin R. Kubade
Abstract
Polymers can be natural or synthetic and are largely used in several applications due to their versatile properties. Polymers can vary widely in their properties and applications, and they are a fundamental part of our everyday life. Polypropylene (PP) is a thermoplastic polymer from the polyolefin family. ...
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Polymers can be natural or synthetic and are largely used in several applications due to their versatile properties. Polymers can vary widely in their properties and applications, and they are a fundamental part of our everyday life. Polypropylene (PP) is a thermoplastic polymer from the polyolefin family. It is among the most widely used plastics in various automotive and packaging industries. Although PP is widely used in commodity range, still its applications are restricted in niche areas due to lack of toughness which can be improved by incorporation of rubbery materials or fillers. Graphene (G) is one of the nanomaterials used to strengthen polypropylene. Graphene is recognized for its outstanding thermo-mechanical properties, making it a highly desirable material in various fields of science and technology. Benefits gained by incorporation of graphene nanoparticles into polypropylene are studied by researchers. In this study, a finite element analysis is performed which shows the mechanical behaviour of PP and G using ANSYS, which is one of the most powerful finite element analysis (FEA) softwares that can help to perform such simulations to understand stress, strain, deformation of components before actual experimentation. The bending load of 100 N and 1400 N in vertical z-direction are applied for 100% PP model, 100% G model and 50% PP+50% G model and the linear part of stress-strain curve is captured in this analysis.
Olefin polymerization and copolymerization
Tingting Yang; Ao Li; Yawei Qin; Jin-Yong Dong
Abstract
Polypropylene is one of the most widely used synthetic resins, which is mainly synthesized with Ziegler-Natta catalysts. In this paper, the functionalized Ziegler-Natta catalyst is applied to prepare high-performance polypropylene. A new way to synthesize functionalized Ziegler-Natta catalysts is to ...
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Polypropylene is one of the most widely used synthetic resins, which is mainly synthesized with Ziegler-Natta catalysts. In this paper, the functionalized Ziegler-Natta catalyst is applied to prepare high-performance polypropylene. A new way to synthesize functionalized Ziegler-Natta catalysts is to dope with inorganic nanoparticles. The MgCl2/TiCl4/BMMF catalysts doped with halloysite nanotubes were prepared and applied to synthesize polypropylene containing less than 200ppm halloysite nanotubes. It is found that doping nanotubes in Ziegler-Natta catalyst has little impact on the structure, composition and activity of the catalyst, and polypropylene with high isotactic degree and molecular weight was synthesized with the functionalized Ziegler-Natta catalyst. Halloysite nanotubes are found to be dispersed in polypropylene in the form of individual nanotube, forming percolated network in the polymer melt effectively. Moreover, the polypropylene containing halloysite nanotubes exhibited better mechanical and thermal resistance properties as compared with conventional polypropylene, and the thermo-oxidative properties of which do not deteriorate as the introduction of nanotubes. This research provides a facile way to relieve the contradiction between the high activity of catalyst and high content of nanoparticles during the preparation of polyolefin nanocomposites by in-situ polymerization, and a new idea to prepare polyolefin nanocomposites by in-situ polymerization.
Structure and property relationship
Leila Latreche; Samira Maou; Lokmane-Taha Abdi; Tahir Habila; Yazid Meftah
Abstract
Polypropylene (PP) is a strong, tough, crystalline thermoplastic material with high performance. Because of its diverse thermo-physical and mechanical properties, it is utilized in a wide variety of disciplines. In this study, the impact of free quenching on the thermo-physical characteristics of PP/calcium ...
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Polypropylene (PP) is a strong, tough, crystalline thermoplastic material with high performance. Because of its diverse thermo-physical and mechanical properties, it is utilized in a wide variety of disciplines. In this study, the impact of free quenching on the thermo-physical characteristics of PP/calcium carbonate (CaCO3) composites was examined. Three distinct heating procedures were used. First, composites were cooled from their melting phase temperature to ambient temperature. Second, composites were cooled from 130°C to a pre-determined and controlled temperature (T: 0°, 20°, 30°, 40°, 50°, 60°, 70°, 80°C). Third, composites were temperature-tested using annealing. The findings suggest that the elongation-at-break and impact strength may be improved following an initial quenching process from the melting phase to ambient temperature. On the other hand, a second quenching process at 0°C produces superior results, and a correlation between mechanical and thermal characteristics is noted; however, while these qualities are increased, others, such as flexibility, density, Vicat softening temperature (VST), and heat distortion temperature (HDT) are negatively impacted.
Polymer physics
Buncha Suksut; Chonticha Seesong; Nutchalida Phueaksri; Chantarawan Chuephlob
Abstract
The effect of calcium lactate (CL) and epoxidized soil bean (ESO) on the crystallization kinetics of polypropylene (PP) was investigated by using polarized optical microscope (POM) and differential scanning calorimetry (DSC). The experiments were performed under both non-isothermal and isothermal conditions. ...
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The effect of calcium lactate (CL) and epoxidized soil bean (ESO) on the crystallization kinetics of polypropylene (PP) was investigated by using polarized optical microscope (POM) and differential scanning calorimetry (DSC). The experiments were performed under both non-isothermal and isothermal conditions. The development of spherulitic microstructure and crystallization kinetics were influenced by both CL and ESO. CL was an efficient nucleating agent for the crystallization of PP. The addition of CL facilitated faster spherulite growth and crystallization rate, while reduced the spherulite size. An opposite performance was discovered with the incorporation of ESO. Nucleation effect of CL on the PP crystallization was less effective with the presence of ESO. Compared with PP/CL, PP/CL/ESO provided a large spherulite size, slow spherulite growth, and a low crystallization rate. This is attributed to the ESO inhibited the nucleation site of CL. However, the degree of crystallinity and the Avrami exponents remained unchanged with the inclusion of both CL and ESO.
Ahmed Hamdi
Abstract
The suitability of a polymer to be processed by injection molding is called moldability. The technicians in injection molding companies tend to estimate moldability by using a parameter named Melt Flow Index (MFI), which however can be often misleading since it represents the ability of a melt to flow ...
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The suitability of a polymer to be processed by injection molding is called moldability. The technicians in injection molding companies tend to estimate moldability by using a parameter named Melt Flow Index (MFI), which however can be often misleading since it represents the ability of a melt to flow in specific conditions, very different from the ones that the polymer encounters during injection molding. A much significant parameter is the so-called flow-length, which is the length reached by a polymer during injection molding in a thin cold cavity. In this work, three commercial grades of polypropylene were injection molded in a cold thin cavity and the flowlengths were measured in function of injection pressure and temperature. The results obtained were correlated with the rheological parameters. The results demonstrate that the MFI is misleading as a technical parameter for the moldability of polypropylene. An empirical equation is proposed to describe the flow-length of polypropylene in function of injection pressure.
Rheology
Maryam Shokrollahi; Bahereh T. Marouf; Reza Bagheri
Abstract
Dimethylbenzylidene sorbitol (DMDBS) is a common nucleating/clarifier agent used in polypropylene (PP). So many researchers have looked at different aspects of incorporating this additive on crystallization behavior of PP. The current study has focused on a rather new subject and that is the role of ...
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Dimethylbenzylidene sorbitol (DMDBS) is a common nucleating/clarifier agent used in polypropylene (PP). So many researchers have looked at different aspects of incorporating this additive on crystallization behavior of PP. The current study has focused on a rather new subject and that is the role of carrier resin of DMDBS masterbatch on the rheological behaviour of polypropylene. This goal has been achieved through studying the role of carrier resin on phase separation behavior of DMDBS upon cooling. It has been shown that a permanent bonding forms between the molecules of carrier resin and DMDBS in the masterbatch and this bonding slows down the crystallization kinetics of DMDBS in the final blend which in turn, influences its rheological behavior. Frequency sweep experiments conducted on a block co-polypropylene showed that lower values of storage shear modulus (G’), loss shear modulus (G’’), and complex shear viscosity (ɳ*) are observed if DMDBS is incorporated in the form of masterbatch. Interestingly, a different effect was observed when the masterbatch constituents were employed directly into the polypropylene, illustrating the importance of the mentioned bonding between DMDBS and the carrier resin in the masterbatch.
Structure and property relationship
Shokoufeh Hakim; Mehdi Nekoomanesh; Ali Shahrokhinia
Abstract
Three polypropylene samples (1-3) were synthesized with a 4th generation Ziegler-Natta catalyst in the presence of cyclohexyldimethoxymethylsilane (donor c), dicyclopenthyldimethoxysilane (donor d) and diisopropyldimethoxysilane (donor p), respectively, as external electron donors. The physical properties ...
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Three polypropylene samples (1-3) were synthesized with a 4th generation Ziegler-Natta catalyst in the presence of cyclohexyldimethoxymethylsilane (donor c), dicyclopenthyldimethoxysilane (donor d) and diisopropyldimethoxysilane (donor p), respectively, as external electron donors. The physical properties of the synthesized polypropylenes were determined. For samples 1 to 3, Successive self-nucleation and annealing (SSA) and Fourier transform infrared spectroscopy (FT-IR) analyses indicated that the relative content of the fraction with high isotacticity and regularity in conformational structure decreased in contrast with the fraction of low isotacticity and low uniformity in stereo-defect distribution from sample 1 to 3. The results demonstrated that the longer the isotactic sequence length and the less uniform the stereo-defect distribution, the greater the conformational order. Deconvolution of the molecular weight distribution curves indicated that the stability of the active centers increased from samples 1 to 3, but the participation of stereo-specefic active centers in the polymerization decreased. DMA tests showed that samples 3 and 1 had the highest damping ability and storage modulus, respectively.
Polymer processing
Fatemeh Hassan; Mehdi Entezam
Abstract
Irradiation of polymers is one of the most effective and economical methods for modifying their properties and for changing their applications. In this study, an extrusion grade polypropylene (PP) was treated by electron beam irradiation to produce a PP suitable for injection molding. Irradiation was ...
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Irradiation of polymers is one of the most effective and economical methods for modifying their properties and for changing their applications. In this study, an extrusion grade polypropylene (PP) was treated by electron beam irradiation to produce a PP suitable for injection molding. Irradiation was carried out at different doses (0-80 kGy) under atmosphere air and at ambient temperature. Melt flow index (MFI) measurements showed PP samples irradiated in the range of 10 to 40 kGy are suitable to use in injection molding. Electron beam irradiation decreased the viscosity and the shear thinning rheological behavior of PP. The differential scanning calorimetry (DSC) analysis revealed that electron beam irradiation increased the crystallinity percentage and temperature of PP, but decreased the melting temperature. Among all treated samples, the PP20, irradiated at the dose of 20 kGy, showed the highest impact resistance. It had higher Young’s modulus and tensile strength, but lower elongation-at-break in comparison with untreated PP.
Polymer processing
Shahab Hoseinpour; Yoones Jafarzadeh; Reza Yegani; Sepideh Masoumi
Abstract
The aim of the present work is to enhance the antifouling properties of polypropylene (PP) membrane based on hydrophilicity improvement. Different contents of neat and modified nanodiamond (0.25, 0.50, 0.75 and 1.00 wt.%) were embedded into PP membranes. Nanodiamond nanoparticles were carboxylated by ...
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The aim of the present work is to enhance the antifouling properties of polypropylene (PP) membrane based on hydrophilicity improvement. Different contents of neat and modified nanodiamond (0.25, 0.50, 0.75 and 1.00 wt.%) were embedded into PP membranes. Nanodiamond nanoparticles were carboxylated by heat treatment method and the presence of carboxyl functional groups on the surface of nanoparticles was confirmed by FTIR analysis. Membranes were then characterized by FESEM, contact angle and tensile strength tests. At the same content of nanoparticles, hydrophilicity, pure water flux and tensile strength of PP/ND-COOH membranes were more than those of PP/ND membranes. Membranes embedded with 0.75 wt. % of neat and modified nanoparticles were used in a submerged membrane bioreactor (SMBR) system along with neat PP membrane. The results showed that critical flux values for neat PP, PP/ND and PP/ND-COOH membranes were 7, 18 and 22 L/(m2.h), respectively. Analysis of fouling mechanisms revealed that antifouling properties of 0.75 wt. % PP/ND-COOH membrane were higher than those of other two ones so that irreversible fouling ratio decreased from 88.9% for neat PP to 47.8% for PP/ND-COOH membrane.
Structure and property relationship
Qian Li; Yongjie Zhang; Huayi Li; Zhongchuan Peng; Yu Zhang; Youliang Hu
Abstract
PP-g-PS copolymer is a typical compatilizer used in polypropylene and polystyrene immiscible blends. PP-g-PS copolymers with different side chain lengths were synthesized, and their thermal and mechanical properties were characterized by differential scanning calorimetry (DSC), polarizing optical microscopy ...
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PP-g-PS copolymer is a typical compatilizer used in polypropylene and polystyrene immiscible blends. PP-g-PS copolymers with different side chain lengths were synthesized, and their thermal and mechanical properties were characterized by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and dynamic mechanical analysis (DMA), respectively. The DSC and POM results show that the introduction of PS side chain dramatically accelerates the crystallization rate of the PP main chain due to the covalent bond in the PP and PS copolymer. Furthermore, the copolymers become more rigid as the PS component content increases. Blend of PP with PP-g-PS copolymer was prepared to investigate the compatibility between PP and PS. The properties of five PP/PP-g-PS binary blends were characterized by DSC, DMA, scanning electron microscopy (SEM) and mechanical testing. Well dispersion of PS and small PS particle size are detected in the binary blends. The formation of covalent bond between PP and PS also increases the compatibility and interfacial adhesion between these two phases.
Catalysis
He-Xin Zhang; Seung-Ri Lee; Dong-Ho Lee; Xue-Quan Zhang; Keun-Byoung Yoon
Abstract
Despite the great potential of graphene as a nanofiller, achieving homogeneous dispersion remains the key challenge for effectively reinforcing polyolefin (such as polyethylene (PE) and polypropylene (PP)) nanocomposites. Therefore, in this research, we report a facile combined in situ polymerization ...
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Despite the great potential of graphene as a nanofiller, achieving homogeneous dispersion remains the key challenge for effectively reinforcing polyolefin (such as polyethylene (PE) and polypropylene (PP)) nanocomposites. Therefore, in this research, we report a facile combined in situ polymerization and masterbatch method for fabricating PP/reduced graphene oxide (rGO) nanocomposites. In the polymerization stage, the synthesized catalyst exhibited a very high activity toward propylene polymerization, while the resultant PP/rGO with a very high isotactic index (I.I. = 99.3), broad molecular weight distribution (Mw/Mn = 14.9), and thermal stability was produced. After meltblending with commercial PP, a significantly increased modulus along with no observable change in tensile strength and elongation-at-break were achieved via the addition of a very small amount of rGO; these properties resulted from the suitable dispersion and good interface adhesion of the graphene sheet and PP matrix. Thus, this work provides a method for production of high performance PP.
Polyolefin degradation
Nikoo Karami; Reza Jahanmardi
Abstract
The present work is aimed to find a new and efficient type of antioxidants for polypropylene. Hence, effects of 3,3-bis(4-hydroxy-2-methyl-5-propan-2-ylphenyl)-2-benzofuran-1-one, generally known as thymolphthalein, on thermo-oxidative stability of polypropylene in solid and melt states were evaluated ...
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The present work is aimed to find a new and efficient type of antioxidants for polypropylene. Hence, effects of 3,3-bis(4-hydroxy-2-methyl-5-propan-2-ylphenyl)-2-benzofuran-1-one, generally known as thymolphthalein, on thermo-oxidative stability of polypropylene in solid and melt states were evaluated and compared with those of SONGNOX 1010, an efficient commercially used antioxidant for the polymer. Oven ageing experiments followed by Fourier transform infrared (FTIR) spectroscopy showed that thymolphthalein increased thermo-oxidative stability of the polymer outstandingly in the solid state and its stabilization efficiency was comparable to that of SONGNOX 1010. In addition, measurements of oxidative induction time (OIT) and oxidation onset temperature (OOT) revealed that thymolphthalein improved thermo-oxidative stability of the polymer in the melt state significantly. It was also observed that thymolphthalein did not interfere with the stabilization action of SONGNOX 1010 in the polymer neither in melt nor in solid state. On the basis of the obtained results, a probable mechanism for the stabilization action of thymolphthalein in the polymer is proposed.
Polyolefin degradation
Larissa Stieven Montagna; Ana Paula Testa Pezzin; Maria Madalena Forte; Ruth Marlene Santana
Abstract
In abiotic degradation the action of light radiation is one of the most important parameters, because polymers undergo degradation due to the action of light (natural or artificial). The aim of this study was to investigate the degradation rate for samples of polypropylene (PP) modified with an organic ...
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In abiotic degradation the action of light radiation is one of the most important parameters, because polymers undergo degradation due to the action of light (natural or artificial). The aim of this study was to investigate the degradation rate for samples of polypropylene (PP) modified with an organic pro-degradant submitted to ageing in a natural environment and to accelerated ageing test. The degradation behavior of the samples exposed to the ageing processes was evaluated through changes in the degree of crystallinity (Xc ), surface morphology (Scanning Electron Microscopy) and molecular weight. The results indicated that for the modified polypropylene samples natural ageing led to a 42.3% reduction in the molecular weight and the surface morphology showed evidence of erosion. In the accelerated ageing process the UV radiation was stronger, which led to a 94.3% increase in the degree of crystallinity and micro-voids were present on the surface of the modified polypropylene.
Polyolefin degradation
Larissa Montagna; Andre Luis Catto; Maria Madalena Forte; Ruth Marlene Santana
Abstract
In this study, PP films were modified with an organic pro-degradant in different concentrations (1, 2 and 3 wt.%), exposed in the first step of degradation to natural ageing for 100 days followed by biodegradation in simulated soil in the respirometric test for 100 days. At the end of the combined degradation ...
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In this study, PP films were modified with an organic pro-degradant in different concentrations (1, 2 and 3 wt.%), exposed in the first step of degradation to natural ageing for 100 days followed by biodegradation in simulated soil in the respirometric test for 100 days. At the end of the combined degradation process the PP samples were characterized according to their morphological and physical properties and the CO2 generated during the biodegradation in soil was monitored. The CO2 production by the PP films modified with the organic pro-degradant was proportional to the oxidation rate and weight loss of the samples. The reduction in the average viscosimetric molecular weight could be attributed to chain scission due to the weathering conditions to which the samples were exposed (natural ageing followed by biodegradation in soil). Scanning electron microscopy (SEM) of the PP films revealed surface deterioration of the films with the organic pro-degradant after the combined degradation process.
Catalysis
Gholam-Reza Nejabat; Mehdi Nekoomanesh; Hassan Arabi; Hamid Salehi-Mobarakeh; Gholam-Hossein Zohuri; Mohammad-Mahdi Mortazavi; Saeid Ahmadjo; Stephen A. Miller
Abstract
Several types of hybrid catalysts are made through mixing of 4th generation Ziegler-Natta (ZN) and (2-PhInd)2ZrCl2 metallocene catalysts using triethylaluminum (TEA) as coupling agent. Response surface methodology (RSM) is used to evaluate the interactive effects of different parameters including ...
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Several types of hybrid catalysts are made through mixing of 4th generation Ziegler-Natta (ZN) and (2-PhInd)2ZrCl2 metallocene catalysts using triethylaluminum (TEA) as coupling agent. Response surface methodology (RSM) is used to evaluate the interactive effects of different parameters including amounts of metallocene and TEA and temperature on metallocene loading. Analyzing the amounts of Al and Zr elements in the hybrid catalysts through ICP-OES and EDXA reveals that temperature plays a crucial role on anchoring of the metallocene catalyst on ZN while TEA has the least determining effect. The ICP analysis shows that as the concentration of Al goes up in the hybrid catalyst the concentration of Zr passes a maximum, while EDXA shows a direct relationship between the Al and Zr contents. Using triisobutylaluminum (TIBA) and methylaluminoxane (MAO) as the coupling agents, almost similar metallocene loadings are observed. Finally, the performance of hybrid catalysts is investigated in propylene polymerization and the obtained polymers are characterized using DSC and DMTA through which the presence of two types of polymers in the final product are confirmed.
Catalysis
Maria Marques; Renato Oliveira; Rafael Araujo; Bruno Amantes
Abstract
A fourth-generation Ziegler-Natta catalyst was prepared to synthesize polypropylene (PP), which was stabilized by in situpolymerization employing lignin as antioxidant. The antioxidant properties of lignin were compared with those of the commercial antioxidant Irganox 1010. The presence of lignin in ...
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A fourth-generation Ziegler-Natta catalyst was prepared to synthesize polypropylene (PP), which was stabilized by in situpolymerization employing lignin as antioxidant. The antioxidant properties of lignin were compared with those of the commercial antioxidant Irganox 1010. The presence of lignin in the reaction medium slightly decreased the catalytic activity of the reaction. The isotacticity index (I.I.) of PP synthesized with lignin (PP-lig) was not affected by the presence of the additive in the reaction medium. The thermal properties, characterized by differential scanning calorimetry, showed slightly decreased degree of crystallinity (Xc), but the melting temperature (Tm) and crystallization temperature (Tc) were not affected when compared with the neat polymer. Lignin showed good activity as a stabilizer by thermogravimetry. The initial temperature of degradation (Tonset) increased when compared to the pure PP and PP stabilized with the commercial antioxidant. The lower carbonyl index of the PP, evaluated by infrared spectroscopy (FTIR) after thermo-oxidative treatment, also revealed the stabilizing action of lignin.
