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In the present paper, a dynamic optimization problem regarding grade transitions in bulk poly(propylene) polymerization processes is formulated and solved for the first time. Initially, a detailed dynamic process model is presented and implemented, comprising mass and energy balances, some of the polymer properties (such as the melting flow index and the xylene solubles) and regulatory control loops. Additionally, the effects of cocatalyst and electron donor on the propagation rate constant are taken into account. Then, the dynamic optimization problem is formulated and an evolutionary algorithm is used to solve the resulting nonlinear programming problem. It is shown that there is significant coupling among the manipulated variables and the controlled performance and polymer property variables, which adds complexity to the grade transition problem and demands the simultaneous manipulation of multiple variables during transitions. Despite the inherent open‐loop unstable nature of the analyzed process, it is shown that smooth grade transition trajectories can be accomplished through proper adjustment of the objective function weights. Finally, it is shown that the obtained optimum trajectories can significantly diminish the transition time, which can be of paramount importance for the plant economics. [ABSTRACT FROM AUTHOR]

The aim of the paper was to determine the mechanical, thermal, and morphological properties of heat-treated wood-polypropylene polymer composites (WPCs) and to select the composites having the optimum properties with the PROMETHEE method. In this study, polypropylene (PP) as a matrix, wood thermally treated at 180°C and 220°C as reinforcement filler were examined for preparing composites. The PP composites were compounded using a twin-screw extruder and test specimens were prepared by compression moulding. According to the test results, the thermal and mechanical properties of the WPCs generally increased with the addition of heat-treated wood fillers. The SEM images showed that the wood fillers dispersed better in the PP matrix as the particle size decreased from 40 mesh to 100 mesh. The WPCs having the optimum mechanical and thermal properties were determined for 40 mesh heat-treated wood at 220°C and 20 wt-% loadings with PROMETHEE method. [ABSTRACT FROM AUTHOR]

Melt mixed polypropylene/polyamide 6 (PA6) and multiwalled carbon nanotubes (CNTs) were molded by compression, injection, and interval injection molding. PA phase exists as an isolated dispersed phase in the sea–island system with different phase orientations and dispersion degrees. CNTs prefer to be located in the minor PA phase because of their remarkable compatibility. However, when the content of CNTs is high enough, a conductive path can be formed regardless of the phase morphology. Moreover, when the CNT content is low, the dispersed PA forms an unelongated structure, which is beneficial to electrical conductivity. Although the elongated PA phase holds advantages in terms of its tensile properties, its conductivity network is defective. These results were proposed to uncover the influence of dispersed phase morphology on mechanical and electrical conductivity. [ABSTRACT FROM AUTHOR]

Summary: This paper shows the characterization carried out in polypropylene nanocomposites made up with different proportions of modified nanoclays (1% 2.5% and 5%). Modified nanoclay (montmorillonite) has been added to improve the mechanical properties of the original matrix and increase its heat resistance. The objective of this work is to characterize multiscale nanocomposites, from nano-scale to macroestrucutural scale using thermography, nanoindentaton and mechanical testing. [ABSTRACT FROM AUTHOR]

Diffuse small-angle X-ray scattering is caused by inhomogeneity in the electron density distribution of a material and is often attributed to the existence of microvoids in polymers. The content, dimensions and relative surfaces of the microvoid system can be determined thereby. The dimensions of the coherently scattering domains and the sizes of the inhomogeneities are related by the form, or shape factor (f). Changes in this factor highlight structural changes in polymer fibers caused by different treatments. In the present paper the microvoid system of differently treated poly(ethylene terephthalate) (PET) and poly(propylene) (PP) fibers were studied after subjugation to different treatments. PP fibers were spun from two different polymers and drawn at different temperatures, whereas PET fibers were treated in different media. The form factors found for PET and PP fibers were rather high. For PP fibers, drawn at different temperatures and draw ratios, the form factors were between 2 and 5. Untreated PET samples had form factors of about 6. A supercritical fluid treatment could increase the form factor up to 8. Conventional water dyeing and hot air treatments caused considerable changes in the microvoid system and increased the form factor to values even larger than 8. [ABSTRACT FROM PUBLISHER]

This paper presents the method of obtaining poly(propylene) (PP) nonwoven fabrics with antimicrobial properties, using Alafosfalin as the nonwoven modifying agent. Alafosfalin, namely L-alanyl-L-1-aminoethylphosphonic acid, presents representative P-terminal phosphonodipeptide, which possesses a strong, broad spectrum of antimicrobial properties. The analysis of these biofunctionalized nonwoven fabrics processed by the melt-blown technique, included: scanning electron microscopy (SEM), UV/Vis transmittance, FTIR spectrometry, and air permeability. The nonwovens were subjected to microbial activity tests against colonies of Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. Results indicate that the described nonwovens can be successfully used as an antibacterial material. [ABSTRACT FROM AUTHOR]

Melt crystallization of isotactic polypropylene (iPP), containing crystallites of N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide (DCNDCA) as a nucleating agent of the the β-phase iPP crystal, is carried out under a magnetic field (6 T) to obtain the alignment of the iPP crystal induced by magnetic alignment of DCNDCA. In a previous paper, DCNDCA was reported to undergo magnetic alignment in a liquid suspension. The obtained iPP sample exhibits alignment of the β-phase crystal with the c-axis aligned perpendicular to the magnetic field. The comparison of this alignment of iPP with the reported magnetic alignment of DCNDCA indicates that the β-phase crystal grows epitaxially on the DCNDCA crystal. The (330)β plane of the iPP crystal lies on the bc-plane of the DCNDCA crystal in which the direction of the c-axis of the iPP coincides with the direction of the b-axis of the DCNDCA crystal. [Copyright &y& Elsevier]

Long chain branched polypropylene/clay‐supported calcium pimelate (LCBPP/CaHA‐OMMT) composites and their foams were prepared using self‐made CaHA‐OMMTs. The CaHA‐OMMT showed high β‐nucleation efficiency, especially that with larger initial interlayer distance could induce 89% of β crystal in LCBPP with a dosage of 0.5%. Clay layers were mostly exfoliated in the composites with low CaHA‐OMMT content, while intercalated structure was dominant and agglomeration occurred when the content of CaHA‐OMMT was higher than 2%. The composite foams were prepared with improved compression molding. The cell structure of the composite foams is improved, that is, the density, cell size, and cell size distribution decreased, and the cell density increased compared with that of LCBPP foam. The minimum average cell size of LCBPP/CaHA‐OMMT foams was 77 μm and the maximum cell density was 2.8 × 106 cells/cm3 with the CaHA‐OMMT content of 2%. It is concluded that there are two requirements for high nucleation efficiency: the CaHA was supported on OMMT layers, and the OMMT platelets were dispersed well and exfoliated. The compression properties of the composite foams, including compression modulus, energy absorption density and failure strength increased first and then decreased with the increase of CaHA‐OMMT content. [ABSTRACT FROM AUTHOR]

Agro‐industrial residue from sugarcane cultivation in Brazil generates more than 200 million tons of bagasse per year, which is rich in plant fibers that can be potentially applied in polymer composites. New processing routes are required to process composites with fiber contents above 50% wt. The objective of this work was to incorporate sugarcane bagasse fibers to polypropylene at high contents (50%–80% wt) in the development of composites via thermokinetic mixture. Composites with 50% and 60% fibers showed a traditional composite morphology, while those with 70% and 80% resembled agglomerated composites. The water absorption varied between 5% and 34%, increasing with fiber content, while the bulk density remained relatively constant, close to 1 g/cm3. The flexural strength and the flexural modulus reached 31 MPa and 2.4 GPa, respectively, tending to decrease with fiber content. In summary, the present work showed the viability of the proposed processing route, with only two starting materials, to produce cheap, relatively lightweight composites with mechanical properties close to and water absorption much lower than wood composites (medium‐density fiberboard and medium‐density particleboard) used in similar applications, such as furniture, construction, and automobile industry. [ABSTRACT FROM AUTHOR]

The glass syntactic polypropylene composite highlights as the most used wet thermal insulation solution for subsea pipelines. The continuous and disperse phases of the material, however, show low interaction levels due to poor chemical compatibility between the polypropylene matrix and the hollow glass microspheres, ultimately leading to a premature failure when subjected to mechanical loads. This article assesses the use of poly(propylene‐g‐maleic anhydride) and ethylene‐acrylic ester‐glycidyl methacrylate terpolymer as compatibilizing agents to enhance the matrix–filler interaction. The effectiveness of the selected strategy is analyzed through mechanical stress–strain tests, evaluation of absorbed water during hot water immersion, and evaluation of thermal properties. The composites with polypropylene and heterophasic polypropylene matrices, 25% by the weight of hollow glass microspheres, and contents of compatibilizing agents spanning from 1% to 5% by weight were prepared and tested. The addition of compatibilizers increased the tensile strength by 9%–30% and reduced the elongation at break by 13% to 45%. Thermal analyses indicated no significant influence of compatibilizers on melting points and crystallization temperatures; meanwhile, water absorption studies indicated opposite effects of each compatibilizer on the absorbed water content. Finally, the main results observed were ratified through scanning electron microscopy. [ABSTRACT FROM AUTHOR]

The paper reports the experimental results of a study investigating the effect of different contents of a mineral filler on the rheological properties, p-v-T, of polypropylene. Using the pvT100 apparatus, we measured specific volume under isobaric cooling at different pressures for pure polypropylene and chalk-filled polypropylene (10 wt%, 20 wt% and 30 wt%). Next, we employed computer methods to determine the coefficients of a mathematical model describing the variations in specific volume in a function of temperature and pressure. The model was used in the numerical simulations of injection molding and shrinkage processes.

ABSTRACT The crystallization of polypropylene with different density of macromolecular entanglements was studied in isothermal and non-isothermal conditions. The growth rate of spherulites increased with reduced concentration of entanglements. Reduction of entanglements shifted the temperature of transition between Regimes II and III, which means that more regular growth of crystals was possible at lower temperature. The range of temperatures at which polypropylene cavitated in regions of melt occluded by spherulites was limited to 137-139°C, with weak dependence on entanglements density. DSC studies showed that isothermal crystallization is faster in less entangled polymers, however the crystallinity degree and long period of structure (by SAXS) were similar for studied materials. When the crystallization was completed during fast cooling, the differences between individual samples were more significant. The partial disentangling, overcoming some limitation for movements of macromolecules, made possible easier crystallization, even at low temperature of Regime III. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 748-756 [ABSTRACT FROM AUTHOR]

The influence of polymerization temperature ( Tp) on the isoselectivity of the C2-symmetric zirconocene catalysts rac-Me2Si(2-Me-4-PhInd)2ZrCl2/MAO ( 1/MAO), rac-Me(CyHex)Si[2-Me-4-(4′- tBuPh)Ind]2ZrCl2/MAO ( 2/MAO), and rac-Me2Si(2-Me-4-Ph-5-OMe-6- tBuInd)2ZrCl2/MAO ( 3/MAO) in propene polymerization, has been studied in the range 30-85 °C in liquid propene. All three catalysts show similar polymerization activity versus Tp profiles, with a maximum at about 60 °C ( 1/MAO), 80−85 °C ( 2/MAO), and 70−80 °C ( 3/MAO). 3/MAO shows the highest activity at any Tp. The isoselectivity of the three catalysts remains high and approximately constant in the whole Tp range investigated, as indicated by the roughly constant isotactic triad content ( mm > 99%) of the produced isotactic poly(propylene)s (iPP). Surprisingly, the melting and crystallization temperatures of iPP increase by increasing TP. This behavior is due to an unexpected increase in catalyst regioselectivity with Tp, as indicated by the decrease in the content of 2,1-erythro regiodefects (2,1e) at increasing Tp. A mechanism involving a metal cation-2,1-coordinated propene slow state is proposed to account for this so far unnoticed behavior. The correlations between Tp, Tm, and [2,1e] are defined for these three catalysts. [ABSTRACT FROM AUTHOR]

Liquid chromatography at critical conditions (LCCC) of poly(propylene) (PP) holds unique potential to further augment the understanding of molecular heterogeneities present in PP. The critical conditions for isotactic poly(propylene) (iPP) and syndiotactic poly(propylene) (sPP) have been identifi ed using porous graphitic carbon as stationary phase and combinations of adsorption and desorption promoting solvents. It is found that 1,2,4-trichlorobenzene is a stronger desorption promoting eluent compared to 1,2-dichlorobenzene, while 2-octanol shows a weaker adsorption promoting effect compared to 2-ethyl-1-hexanol for all stereo-isomeric forms of PP. The fraction of desorption promoting solvent needs to reach critical conditions decreased in a linear manner with the temperature. High temperature 2D liquid chromatography with infrared detection provides quantitative information about the fractions of the constituents (iPP and ethylene-propylene copolymer) of a model high impact PP sample at LCCC of iPP. [ABSTRACT FROM AUTHOR]

We present a simple strategy for the fabrication of poly(propylene) (PP) superhydrophobic surfaces, i.e., surfaces that show water contact angle (WCA) ≥ 150° after a simple dipping process. Injection-moulded PP samples were coated with titanium dioxide nanoparticles previously functionalised with trimethoxy propyl silane. Water, ethanol or xylene were used as solvents in the nanoparticles' suspensions. The prepared superhydrophobic surfaces were characterised by WCA, FTIR-ATR, SEM and profilometry measurements. PP coated samples showed very low wettability, with WCAs higher than 150° when xylene was used as a solvent. The combination of increasing the surface roughness via dipping coating process plus the low surface tension of the coating produced the final superhydrophobic PP substrates. [ABSTRACT FROM AUTHOR]

Electrically conductive polypropylene nanocomposites containing multi-walled carbon nanotubes were produced by melt blending by dilution of a concentrate masterbatch containing 10 wt.% of filler. In order to promote polymer infiltration within primary agglomerates a ultra-low melt viscosity polypropylene grade has been used for masterbatch production. Moreover, three polypropylenes with different melt viscosities have been used for successive dilutions. Filler dispersion has been assessed by both indirect macroscale analyses and direct morphological investigations. Characterization showed percolation thresholds occurring for very low filler contents. During dilution, lower polymer viscosities lead to more effective residue agglomerates dispersion, hence better electrical properties. [ABSTRACT FROM AUTHOR]

The relationship between varying processing variables, rotor speed (50 to 200 rpm) and mixing time (10 to 30 min), and MWCNT loading (0.5 to 2.0 wt%), on MWCNT dispersion in a poly(propylene) during batch melt mixing was investigated. MWCNT dispersion was improved by increasing rotor speed and/or mixing time, 200 rpm and 30 min being optimum, although composites prepared employing 100 rpm and 20 min were the most electrically conducting, (<100 S cm−1). PP shear viscosity increased with increasing MWCNT loading yielding a rheological percolation of ∼0.5 wt% MWCNTs. Volume resistivity of the composites decreased with increasing rotor speed and for mixing times up to 20 min only, the former yielding an electrical percolation of ∼0.65 wt% MWCNTs at 200 rpm. [ABSTRACT FROM AUTHOR]

Poly(propylene) homopolymer/fly ash (50% wt) composites have been prepared from two samples of fly ash that differ in terms of the geographic source of coal feedstock, which left one of the samples with a higher group I and II metal content. A screening study indicated that Lubrizol Solplus® C800 (an unsaturated carboxylic acid dimer coupling agent), initiated with dicumyl peroxide, conferred the best strength-toughness balance to the composites. In some cases, however this was related to detachment of the interfacial region due to possible extraction of PP-C800 adduct-group I and II ion reaction products. Interfacial adhesion was arguably too high in the case of the fly ash sample bearing a lower level of group I and II ions. These deductions were also supported by DSC data. [ABSTRACT FROM AUTHOR]

ABSTRACT Coefficients of linear thermal expansion (CTE) for poly(propylene)/ poly(propylene)-grafted-maleic anhydride/montmorillonite ethylene-co-octene elastomer (PP/PP-g-MA/MMT/EOR) blend nanocomposites were determined as a function of MMT content and various PP-g-MA/organoclay masterbatch ratios. The nanocomposites were prepared in a twin-screw extruder at a fixed 30 wt % elastomer, 0-7 wt % MMT content, and various PP-g-MA/organoclay ratio of 0, 0.5, 1.0, and 1.5. The organoclay dispersion facilitated by the maleated PP helps to reduce the size of the dispersed phase elastomer particles in the PP matrix. The elastomer particle size decreased significantly as the PP-g-MA/organoclay ratio and MMT content increased; the elastomer particles viewed // to flow direction (FD) are smaller and less deformed compared to those viewed // to transverse direction (TD). The elastomer particle shape based on the view along the three orthogonal directions of the injection molded sample is similar to a prolate ellipsoid. The CTE decreased significantly in the FD and TD, whereas a slight increase is observed in the normal direction in the presence of MMT and PP-g-MA. The Chow model based on a two population approach showed better fit to experimental CTE when the effect of MMT and elastomer are considered individually. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B Polym. Phys. 2013, 51, 952-965 [ABSTRACT FROM AUTHOR]

ABSTRACT The deformation behavior of a polypropylene (PP) sheet, in which c-axis of β-form PP orients perpendicular to the flow direction in the sheet [transverse direction (TD)], is studied focusing on the mechanical anisotropy. The deformation mechanism of this sample is found to be strongly dependent on the stretching direction. Shear yielding is dominant in TD stretching, indicating that reorganization and phase transformation of crystalline form occur easily with low yield stress. On the contrary, in machine direction (MD) stretching, numerous microvoids appear with the transformation of crystalline form as well as the rotation of c-axis. Moreover, the crazing process, initiated at the orientation defects, occurs locally with remaining undeformed region in which β-form PP orients to TD. The deformation behavior is applicable to a microporous film. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 897-906 [ABSTRACT FROM AUTHOR]

The effect of adding hydrogen and/or electron donor on the microstructure of polypropylene polymerized with a 4th generation Ziegler-Natta catalysts at two temperatures on the molecular weight distribution, tacticity, and crystallinity of polypropylene is thoroughly investigated in this article. Polypropylene tacticity and crystallinity increases not only when external donors are added, but also when hydrogen is used as a chain transfer agent. The molecular weight distribution of the resins is deconvoluted into several Flory's most probable distributions to show how different active site types respond to the presence of electron donor and hydrogen. [ABSTRACT FROM AUTHOR]

The superfine down powder (SDP) was chemically modified using phenyl isocyanate (PI) and octadecyl isocyanate(ODI), respectively. The wetting behavior of water on the SDP surface was observed by the contact angle. The modified and unmodified SDP-filled polypropylene (PP/SDP) fibers were prepared and characterized by the moisture absorption experiments and thermal and mechanical analysis. The PI- and ODI-modification improved the hydrophobic property of SDP, and the excellent moisture absorption of SDP remained as such. The addition of SDP improved the moisture absorption and thermal stability of the PP fiber. The modification of PI and ODI strengthened the mechanical property of the blend fiber. © 2012 Wiley Periodicals, Inc. Adv Polym Techn 32: E514-E519, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21297 [ABSTRACT FROM AUTHOR]

Nanocomposites of polypropylene and graphene nanoplatelets were synthesized by in situ polymerization in liquid monomer in the presence of highly effective isospecific homogeneous metallocene catalyst. Microstructure, mechanical, dielectric, and thermal properties of composites are presented. X-ray phase analysis data indicate that graphene nanoplatelets are present in composites as thin flaky particles aggregates, with aspect ratio affected by sonication of reaction mixture. Crystallization temperature of polypropylene increases in composites. Nanocomposites are characterized by high rigidity, thermal stability, and crystallization temperature, low conductivity, and high dielectric losses in the microwave range. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

In this work, a novel isotactic polypropylene (PP)/fibrous cellulose (FC) composite containing a poly(ethylene oxide) (PEO)/TiO2 was prepared, and its oxo-biodegradation behavior was studied. FC loading of 5 and 1% resulted in an opaque film and relatively good transparence, respectively. Fourier transform infrared (FTIR) spectra of the nonphotodegraded composite samples revealed little PP auto-oxidation under the melt-mixing condition. Ultraviolet irradiation enhanced the auto-oxidation of the composite. FTIR analyses of the composite indicated that TiO2 and PEO functioned as the initiator and accelerator of PP auto-oxidation, respectively. In addition, even with 1% PEO, the accelerator effect was enhanced by the spreading of the degraded PEO component from other areas when the film thickness was increased. All PP/PEO/TiO2/FC composites with a PEO content varying from 0.3 to 5% showed a Young's modulus value of ∼ 180% higher than that of pristine PP. Biodegradability of the photodegraded composite was confirmed by a soil burial test. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Summary: Dynamic and steady shear rheological properties of dynamically vulcanized iPP/EPDM blends were investigated. Two different curing systems based on sulfur or phenolic resin were applied on iPP/EPDM blends. The use of phenolic resin system allows producing materials with lower viscosity at higher rubber content in comparison with sulfur-cured compositions. Melt rheological properties of iPP/EPDM blends with different loading levels of paraffinic oil were studied. Significant improvement in the flowability is observed for TPVs extended with 50 wt% oil. A partial replacement of EPDM on rubber powder decreases the viscosity of materials. [ABSTRACT FROM AUTHOR]

Biaxially oriented polypropylene (BOPP) films are used in a variety of areas around the world. They are especially well suited for food packaging and industrial usages because of their high productivity. Many studies on the stretchability with regard to crystal structure changes have been reported by various researchers because the machine speed has been increasing and the demand to produce thinner films has been becoming more important. Furthermore, a number of studies on the surface structure of BOPP films with craterlike roughnesses have been reported since the 1980s. Although a craterlike surface roughness was formed under specific film process conditions, the formation mechanism and the controlling method of the craterlike film surface are yet to be clarified. In this report, we demonstrated a new hypothesis for the craterlike film surface roughness formation mechanism by analyzing the morphology of the surface layer of polypropylene (PP) sheets and by investigating the relationship between the surface structural changes and the changes in the entire structure. As a result, we found that an overcritical crystallization time was needed to form the crater on the surface of the BOPP film, and the crater formation mechanism was closely related not only to the surface structure changes but also to the deformation phenomenon of the spherulite in the PP sheet during stretching. Furthermore, this report shows the controlling factors in the formation of the crater structure from the viewpoint of the production conditions. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012 [ABSTRACT FROM AUTHOR]

Surface defects associated with manufacturing processes can severely impair the appearance of polymeric products. These defects can be enhanced with ageing (time, UV-light, heat and weather conditions). In the present contribution, the interest is focused on the defects generated during injection molding of elastomer-modified polymers that are often used in the automotive sector to produce interior and exterior components. In particular, defects denoted as 'flow marks' or 'tiger stripes' were investigated. Two different grades of elastomer-modified polypropylene (PP)-containing mineral fillers were studied here before and after heat ageing for 9 weeks at a constant temperature of 95°C. Although injection moldings are one of the grades that did not exhibit any flow marks, moldings of other PP-grade showed such defects and they were enhanced after the ageing process. The properties and structure of the glossy and the dull bands (as well as the effect of the thermal ageing) have been assessed by several characteristics such as microhardness, nanohardness, crystallinity, and surface composition. An increase in surface hardness was noted after the ageing treatment as a consequence of increased crystallinity. Dull and glossy bands also exhibited different values of the nanohardness, glossy bands were harder, and the dull bands appeared to be less crystalline. The surface composition of glossy and dull regions was slightly different; the surface regions of the glossy areas contained higher amounts of filler particles. The effect of the ageing on the striped appearance is furthermore discussed in relation to possible depletion of the stabilizer system. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

A new technique to provide melt elasticity using flexible fine fibers prepared from a polymer with high melting point is demonstrated. A polymer composite of poly(propylene) with a small amount of fine fibers of poly(butylene terephthalate) shows marked strain-hardening behavior in elongational viscosity, i.e., a rapid increase in the transient elongational viscosity with time or strain. The blend also shows prominent normal stress difference at steady shear. These elastic properties have not been observed for polymer composites with rigid fibers and can be applicable to the modification of rheological properties and thus the improvement of processability. [ABSTRACT FROM AUTHOR]

TPVs are prepared by dynamic vulcanization in which crosslinking of an elastomeric polymer takes place during its melt mixing with a thermoplastic polymer under high-shear conditions. 30:70 wt% blends of PP and ethylene-octene copolymer are vulcanized using electron-induced reactive processing (EIReP) employing a range of absorbed doses (25, 50, and 100 kGy) while keeping the electron energy and treatment time fixed. The structure/property relationships of the prepared samples are studied using various characterization techniques such as DMA, DSC, SEM, and melt rheology. The results suggest that EIReP offers a novel route to prepare TPVs without any chemical crosslinking and coupling agents. [ABSTRACT FROM AUTHOR]

Boehmite alumina nanoparticles are added to PP -g-MAH-compatibilized blends of PA 12 and PP to study the effects of nanoparticle loading in the resulting composites. WAXD and SEM data suggest that the nanoparticles enhanced the coalescence of PP. DSC, DMA, and TGA reveal that the final properties such as crystallization temperature, flexural storage modulus, thermal degradation temperature, etc., improve with increasing nanoparticle loading for blend/based composites. FTIR results show that the nanoparticles interfere with the interfacial activity at 5 wt% nanoparticle loading. All results are compared between the neat polymers and the compatibilized blend and show that despite a slight increase in dispersed-phase domain size, all other properties improve with the addition of AlO(OH). [ABSTRACT FROM AUTHOR]

Apparent kinetic rate constants and activation energies for catalyst activation, deactivation, and propylene propagation with a 4th-generation Ziegler-Natta catalyst are estimated. The rate of polymerization in the presence of donor and hydrogen is higher than in their absence. Catalyst activation and propagation rate constants increase with the addition of hydrogen, likely because hydrogen frees 2-1-terminated dormant sites. The deactivation term was the highest without electron donor, presumably because the nonspecific sites deactivate faster than the specific sites. Apparent activation energies for catalyst activation, deactivation, and propagation are not significantly influenced by the presence of hydrogen or external donor, indicating that they do not affect these mechanisms substantially. [ABSTRACT FROM AUTHOR]

The comparative studies on the thermal, mechanical and morphological behavior of compression molded poly(propylene) (PP)/wood flour (WF) composites were performed using wood flours (WFs) of different origins. The comparison has been made on the basis of results obtained from thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and tensile testing. It has been demonstrated that an addition of 5 wt.-% of maleic anhydride grafted polypropylene (PP-g-MA) has a significant effect on the morphological and thermomechanical behavior of the composites. Although, microscopic examinations revealed no significant differences in the morphology of the compatibilized composites, a remarkable improvement of thermal degradation behavior was observed. From the view point of mechanical properties, the composites with high amount of filler (60 wt.-%) showed similar behavior irrespective of the origin of wood flour. [ABSTRACT FROM AUTHOR]

The semi-batch slurry polymerization of propylene using a heterogeneous multi-site type Ziegler-Natta catalytic system was studied. A simple kinetic model including initiation, propagation, spontaneous chain transfer, chain transfer to hydrogen, chain transfer to monomer and chain transfer to cocatalyst, and spontaneous deactivation was developed to predict instantaneous rates of polymerization and average molecular weights of final products. Estimation of kinetic parameters was performed using online measurements of polymerization rate and end of batch measurements of average molecular weights. The multivariable nonlinear optimization problem was solved using the Nelder-Mead simplex method for three different site types at three levels of temperatures. The model predicts that the propagation reaction has a lower activation energy than chain transfer reactions which leads to a decrease of molecular weight at elevated temperatures. The deactivation reaction has a higher activation energy than the propagation reaction, which results in decreasing the final rate of polymerization at higher temperatures. [ABSTRACT FROM AUTHOR]

A number of symmetrical and unsymmetrical azoalkanes of the general formula R′−N = N−R and related azoxy, hydrazone as well as azine derivatives have been synthesized in order to assess their potential as novel flame retardants for polypropylene alone or in combination with commercially available flame retardants such as alumina trihydrate (ATH), decabromodiphenyl ether (DecaBDE) and tris(3-bromo-2,2-bis(bromomethyl)-propyl)phosphate (TBBPP). The experimental results show that in the series of different sized azocycloalkanes the flame retardant efficacy decreased in the following order: R = cyclohexyl > cyclopentyl > cyclobutyl > cyclooctanyl >> cyclododecanyl. Whereas in the series of aliphatic azoalkanes compounds the efficacy decreased in the following order: R = n-alkyl > tert-butyl > tert-octyl. In addition, also some of the prepared azoxy, azine, and hydrazone derivatives provide flame retardancy to polypropylene films at already very low concentrations (0.25-1 wt%). Noteworthy is that in contrast to other halogen-free radical generators, the azoalkanes are also very effective as flame retardants in polypropylene thick moldings. Interestingly, it was found that 4,4′-bis(cyclohexylazocyclohexyl)-methane) shows a strong synergistic effect with ATH. Thus, in the presence of 0.5 wt% of azoalkane the ATH loading could be reduced from 60 to 25 wt% and still UL94 V-2 rating could be reached. Furthermore, the fire testing data reveal that azoalkanes show a synergistic effect with DecaBDE and when used in conjunction with very low loadings of TBBPP. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The combined effects of organo-modified montmorillonite (O-MMT) gallery polarity, surface modification of magnesium hydroxide (MDH), maleic anhydride grafted polypropylene (MA-g-PP) and antioxidant (Irganox 1010) addition, together with mixing time and rotor speed of the mixer on the measured flexural modulus, maximum (max) flexural (flex) strength and impact strength of the composites were studied. A two-level factorial experimental design of these variables was used to examine their simultaneous effects. The 16 composite samples were prepared by melt mixing in an internal mixer at 200 °C and their properties were measured. The flexural modulus and max flex strength of the samples containing high level of both MDH and O-MMT reached the highest and lowest amount respectively. Effect of the factors and their interactions on impact strength and max flex strength was almost in the same order and by decreasing the amount of O-MMT/or MDH, these properties were increased. The regression equations showed the most effective factors and their interactions which were in good agreement with the obtained results. Addition of 1% w/ w O-MMT to 50% w/ w MDH/PP composites led to the best mechanical properties. [ABSTRACT FROM AUTHOR]

The effect of calcium glutarate (Cagt) and calcium pimelate (Capt) on the formation of β crystalline form in isotactic poly(propylene) in the crystallization temperature range of 110-130°C has been investigated. The content of β phase crystals increase with the addition of calcium glutarate. K (relative content of β crystalline form in the iPP sample) attains its maximum value for iPP doped with 0.3 wt.% Cagt isothermally crystallized at 110°C (26.71%) or 120°C (30.27%), and for iPP doped with 0.2 wt.% Cagt isothermally crystallized at 130°C (31.97%), respectively. Compared with the K values of iPP doped with 0.1 wt.% Capt (78.33-94.76%), the β nucleation ability of Cagt is inferior to that of Capt. The spherulite size of iPP doped with Capt is smaller than that of iPP doped with Cagt. The difference in the β nucleation ability between Cagt and Capt is explained by the difference between their crystal structure parameters and those of β-iPP. [ABSTRACT FROM AUTHOR]

The effect of crystallization temperatures (100-140°C) on the formation of β crystalline form in isotactic polypropylene nucleated by pimelic acid and sodium, magnesium, zinc, calcium, barium and aluminium salts of pimelic acid has been investigated. It is found that β crystalline form can be produced from polypropylene melt, isothermally crystallized at 120 or 130°C. Aluminium pimelate is a α nucleator which suppresses the production of β crystalline form in polypropylene. Pimelic acid and magnesium pimelate are weak β nucleators. Sodium pimelate is a moderate β nucleator. Zinc pimelate, calcium pimelate and barium pimelate are good β nucleators for polypropylene with calcium pimelate being the best. [ABSTRACT FROM AUTHOR]

The thermal endurance of nanocomposites based on isotactic poly(propylene) filled with nanosilicates, is evaluated by a short-term analytical procedure. The procedure is based on oxidative stability measurements by isothermal thermogravimetric analysis in a pure oxygen flow, over the temperature range form 120 to 150 °C, and provides the activation energy of the thermo-oxidative degradation process. The activation energy values thus obtained were compared with those derived by scanning thermogravimetric analysis at different heating rates. The thermal endurance lines for the investigated materials can be drawn with the aid of a conventional life test, based on weight loss measurement as a function of aging time, according to the IEC 60216 procedure. A noticeable increase of the thermal endurance of the isotactic poly(propylene) based nanocomposite with respect to the unmodified polymer is found out. [ABSTRACT FROM AUTHOR]

In fibre production, draw induced crystallisation and orientation are the dominant factors that influence the properties of the final end use article. These properties depend on processing conditions; in particular, the rate of temperature change, which affects crystallinity, and the stress applied during the drawing process, which affects orientation and may also facilitate crystallisation. Polymer crystalline regions can be characterised by wide angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS). An X-ray system capable of in situ determination of fibre structure as it develops during processing has been designed and installed at Clemson University, allowing simultaneous measurement in the WAXS and SAXS regions from the extruder exit and down the spinline. Results from the in situ study of isotactic poly(propylene) with determinations of crystallinity and crystalline orientation from WAXS patterns, and lamellar long period from SAXS patterns, diameter, temperature and velocity, at varying distances from the exit of the extruder are presented. [ABSTRACT FROM AUTHOR]

The influence of molecular weight on the mechanical properties of isotactic poly(propylene) (iPP) and iPP blended with ethylene-propylene copolymers has been investigated by means of the microhardness technique. The hardness ( H) of iPP is shown to slightly decrease with increasing molecular mass, within the range of molecular weights investigated. The H-decrease is correlated to a loss of crystallinity as the average molecular weight increases. On annealing, the mechanical properties are enhanced as a consequence of an increase in both, the degree of crystallinity and the crystalline lamellar thickness. A value of H∞ c for iPP crystals of infinite thickness in the α-form is proposed for the first time. The inclusion of EPR particles in the iPP matrix softens the material. This result could be explained in terms of an increase in the basal surface free energy of the iPP crystals with increasing amount of rubber content. [ABSTRACT FROM AUTHOR]

Polypropylene/organically modified montmorillonite (OMMT) nanocomposites are prepared with different levels of compatibilizer (maleic anhydride functionalized polypropylene) and OMMT. A specially designed polymer nanocomposite injection molding compounder with a hyperbolic nozzle is used to prepare the nanocomposites. The thermal kinetic parameters, the activation energy, pre‐exponential factor, and the reaction model are estimated using isoconversional methods. The activation energy of virgin polypropylene is slightly higher than the polypropylene/OMMT nanocomposites. However, the presence of the compatibilizer is the vital reason for the lower activation energy in the polypropylene/OMMT nanocomposites. The reaction model explains the complexity of the reaction in the presence of OMMT and its influence on the accelerated charring in the later stages of degradation. The optimum working temperature of the prepared polypropylene/clay nanocomposites is significantly higher thus proving that OMMT improves the thermal stability of the nanocomposites. The polypropylene with 5% OMMT and 10% compatibilizer in its weight proportion has the optimum working temperature of 198 °C for 20 000 h before losing its integrity. Thermal Lifetime and Reaction Model: The thermal lifetime and reaction model for polypropylene/organically modified montmorillonite (OMMT) nanocomposites are estimated. The optimum level of compatibilizer and OMMT to improve the thermal stability of the nanocomposite has been characterized. [ABSTRACT FROM AUTHOR]