Propylene Random Copolymer Research Articles

Choosing an Effective Compatibilizer for a Virgin HDPE Rich-HDPE/PP Model Blend.

The most widely used commodity polymers in the rigid packaging industry are polypropylene (PP) and high-density polyethylene (HDPE). For example, blow molding grade of HDPE as a bottle and injection molding grade of PP as a cap are often used to produce detergent bottles. Therefore, the recycled HDPE bottles from post-consumer waste include PP as a contaminant originated from PP bottle caps. To simulate mechanical recycling of bottle waste, the mechanical properties of HDPE-rich-HDPE/PP virgin model blend were studied. For compatibilization, ethylene-based olefin block copolymer, propylene-based olefin block copolymer, ethylene propylene random copolymer, and styrene-butadiene-styrene triblock copolymer were chosen as potential compatibilizer candidates. Contact angle measurements, morphological analysis, adhesion tests of compatibilizer candidates to polymer blend components and the tensile as well as tensile impact properties of the ternary blends were studied. It was found that the ethylene-based olefin block copolymer was the most effective compatibilizer resulting in a return of mechanical properties to those of neat vHDPE due to its ability to encapsulate dispersed vPP particles in a vHDPE matrix (core-shell morphology) and the best adhesion to polymer blend components.

Revisiting the Mechanism of the Meso-to-α Transition of Isotactic Polypropylene and Ethylene–Propylene Random Copolymers

In this work, we have conducted in situ simultaneous small- and wide-angle X-ray scattering and Raman spectroscopy experiments to investigate the fundamental differences in the mechanism of the mesomorphic to α phase transition of the isotactic polypropylene homopolymer and the random ethylene–propylene copolymer. Via quantitative analysis of the results coming from the three techniques, we found that in the homopolymer, chain interlock and chain extension occur during the transition. However, these processes are not necessary for the transition to occur. Indeed, the presence of randomly distributed ethylene co-units hinders the chain interlock process in the early stages of the phase transition (T > 60 °C) and suppresses the chain elongation process at the later stages (T > 90 °C). Consequently, the mesomorphic to α-phase transition in the random copolymer occurs with inclusion of the ethylene co-units inside the crystal lattice, causing increased lateral interchain distance and larger crystalline sizes. Our results show how differences exist in the way solid phase transitions occur at the molecular scale when co-monomers are included into the macromolecular chains, leading to a better understanding of the thermal behavior of semi-crystalline polymers.

Design of Polypropylene Random Co-Polymer Pipe Cutter

The purpose of this research is to design disc cutter for cutting poly propylene random co-polymer (PPR) and high density polypropylene (HDP) extrudates. Analytical methods and software including like Catia and ANSYS are used to design the tool and analyze the effect of load on the cutter. In designing the disc Cutter, using the digital logic method of material selection, the optimum material, carbon steel 19573 with the least cost, locally obtainable, manufacturable and with hardness 63.42HRC is selected. The desired optimum combination of hardness and toughness of the cutter is obtained using hardening temperature 10200C, tempering temperature 2000C, and tempering time 120min which finally gives a hardness value of 63.42HRC. The strength and quality of cut edge are tested by cutting hard plastic PPR pipe with maximum thickness of 12.9mm. By the same setup of the cutter used in the factory the prototype disc cutter serves and its failure rate improves from cutting 150 to 250 PPR pipe pieces which was recognized by the industry. The research results can be used to design the cutter disk and fabricate a cutter with enough strength to cut different thickness of PPR pipes without breakage, reducing unwanted additional cost.

Development of elastic recovering 4-methyl-1-pentene/propylene copolymer

We investigated the solid structures and mechanism of the rubber elastic behavior of 4-methyl-1-pentene/propylene random copolymers (PMPCs), which were prepared using metallocene catalyst, by time-resolved wide-angle X-ray diffraction and small-angle X-ray scattering measurements. PMPC becomes an amorphous polymer and exhibits rubber elasticity in the propylene content (PC) ranging from 28 mol% to 75 mol%. However, the amorphous structure and the elastic recovery largely differ depending on PC. PMPC with PC = 75 mol% had an amorphous structure similar to that of polypropylene and developed rubber elasticity. This was because of the entropic elastic behavior caused by entanglements of polymer chains in a manner that was same as that in amorphous polymers. On the other hand, PMPCs with PC = 28 and 40 mol% had unique amorphous structures. The structures had the interactions between molecular chains and the inhomogeneous structure. These phenomena are presumed to exhibit excellent rubber elasticity, because the two structures change reversibly by deformation.

Chain microstructure of two highly impact polypropylene resins with good balance between stiffness and toughness

For highly impact polypropylene (HIPP), a good balance between stiffness and toughness has attracted much attention from both industrial and academic research. Herein, two HIPP resins (A and B) with different ethylene contents and impact resistances especially at low temperatures are investigated. Their chain microstructure is studied by combining preparative temperature rising elution fractionation (P-TREF) with multiple characterization techniques such as high-temperature gel permeation chromatography (HT-GPC), Fourier transform infrared (FTIR) spectroscopy, 13C nuclear magnetic resonance (13C NMR), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), rheometer, and thermal fractionation. Both samples are mainly composed of four portions: amorphous ethylene−propylene random copolymer (EPR), ethylene−propylene (EP) segmented and blocky copolymer, and isotactic polypropylene homopolymer. Sample A contains ~30 wt% EPR fractions eluted at 35 °C, ~9 wt% EP segmented and blocky copolymers eluted at 80–100 °C, and ~19 wt% highly isotactic polypropylene fractions eluted at 125–140 °C, which are higher than the contents of corresponding fractions in sample B. Moreover, most fractions of sample A have higher molecular weights than the corresponding fractions of sample B. The contribution of different components to stiffness and toughness is also discussed. The excellent impact resistance of sample A is demonstrated from the perspective of chain microstructure.

Facile synthesis of ethylene–propylene fully alternating copolymer and comparison with random copolymer of similar composition

ABSTRACTA precisely sequenced ethylene–propylene (EP) fully alternating copolymer was synthesized via trans‐1,4‐polymerization of isoprene catalyzed by Ziegler–Natta catalyst followed by hydrogenation. This EP copolymer was used as model polymer for studying structure–property relationship. An ethylene–propylene random copolymer (ethylene–propylene rubber [EPR]) with similar ethylene content was also prepared for comparison, and the effect of comonomer sequence distribution on properties was investigated. The copolymer chain structures were monitored by 1H and 13C NMR and Fourier translation infrared. Differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, and tensile tests were employed to determine the thermal and mechanical properties. The fully alternating copolymer EP gives a more precise glass transition comparing than EPR. Further understanding on thermal properties and aggregation behavior of ethylene–propylene copolymers is made possible by this comparative study. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45816.

Novel Supramolecular Block Copolymer of Isotactic Polypropylene and Ethylene-co-propylene Connected by Complementary Quadruple Hydrogen Bonding System

Supramolecular block copolymers comprising isotactic polypropylene (iPP) and ethylene–propylene random copolymers (EP) with complementary quadruple hydrogen bonding junctions have been prepared by melt-mixing of iPP having a 2-ureido-4[1H]-pyrimidinone (UPy) group (iPP-UPy) and elastic EP bearing a 2,7-diamido-1,8-naphthyridine (Napy) group (EP-Napy). Transmission electron microscope (TEM) analysis of the iPP-UPy/EP-Napy composite showed that the elastic EP domains were well dispersed in the iPP matrix compared with the traditional iPP/EP impact polypropylene copolymer (IPC). The iPP-UPy/EP-Napy hydrogen-bonded pseudo block copolymer effectively acts as a compatibilizer in the IPC and contributes to improved mechanical properties of the resulting iPP/EP composite. There is good correlation between impact strength of the IPC and EP domain size observed by the TEM analysis. The use of the complementary quadruple hydrogen bonding system for blending two immiscible polymers has been shown to result in smaller...

Phase‐separation of heterophasic polymer in solution: A model case of impact‐resistant polypropylene copolymer

ABSTRACTImpact‐resistance polypropylene copolymer (IPC) has been well known as commercial heterophasic polymer in which ethylene–propylene random copolymer (EPR) domain is dispersed in the homo‐polypropylene matrix. The phase‐separation of those phases is one of the keys to control the polymer properties. However, especially in the solution, there is rarely report that addresses to the phase‐separation of the IPC due to the difficulties in the investigation; i.e., (i) the proximity of the refractive indices of those phases and (ii) the small size of the EPR droplet. Here, the phase‐separation of the commercial IPC in xylene is traced by the in situ small angle X‐ray scattering which the phase‐separation temperature is clearly revealed. The results also show that the evolution of the EPR domain is strongly depended on the polymer composition. Moreover, the migrations of the copolymers are evidenced, and this could be a model for other heterophasic systems. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45069.

Toughness Reinforcement in Carbon Nanotube-Filled High Impact Polypropylene Copolymer with β-Nucleating Agent

In this work, carbon nanotubes (CNTs) were introduced into an impact polypropylene copolymer (IPC) with β-nucleating agent to prepare IPC composites just by means of a simple mechanical blending method without any special treatment of the CNTs. The resultant IPC composites demonstrated an impressively improved impact property (97.78% increment of toughness compared to pure IPC). It was found that CNT aggregates were dispersed in the polypropylene homopolymer (hPP) matrix rather than the interface between the dispersed phase and hPP host. At the presence of CNTs, the size of the ethylene–propylene random copolymer elastomer particles in the IPC nanocomposites was decreased as evidenced by scanning electronic microscopy, and moreover, the mobility of molecular chains in the amorphous phase of the hPP matrix and crystalline lamellae was enhanced as confirmed by dynamic mechanical analysis and small-angle X-ray scattering measurement. The selective distribution of CNTs, the decreased size of elastomer particl...

Molecular structure and local dynamic in impact polypropylene copolymers studied by preparative TREF, solid state NMR spectroscopy, and SFM microscopy

The phase morphology in impact polypropylene was studied by size exclusion chromatography (SEC), differential scanning calorimetry (DSC), and solid-state nuclear magnetic resonance (NMR). The characterizations of the raw copolymer materials indicate the presence of amorphous and crystalline phases. In order to gain more comprehensive insight in the microstructure of these materials, four different subsamples were prepared by Temperature Rising Elution Fractionation (TREF) and subsequently analyzed by DSC, SEC, analytical TREF and solid state NMR measurements. Fraction 1 consisted of non-crystalline ethylene–propylene random copolymer (EPR). Fraction 2 was composed of intermediate ethylene and propylene segments with different length and capabilities to crystallize. In fraction 3, long propylene segments were the dominating contribution, although some amorphous and crystalline ethylene sequences were detected, which are probably incorporated into the polypropylene main chains, since no soluble component was detected by analytical TREF. Finally, isotactic polypropylene (iPP) was determined to be the unique component of fraction 4. The local molecular mobility in the different phases was analyzed using 2D Wide Line Separation (WISE) NMR, while 13C detected spin diffusion experiments helped to elucidate local morphologies. Scanning Force Microscopy (SFM) studies of the impact polypropylene revealed a semicrystalline iPP matrix with dispersed softer regions, which involve not only soft amorphous elastomeric EPR components, but additional nano-domains with semi-crystalline properties different from the iPP matrix. Combining the SFM and solid state NMR results, a phase model for the EPR regions dispersed in the iPP matrix is proposed.

Electrophysical Properties of Thermally Conductive Polymer Materials

Results of studies on basic electrophysical properties of new thermally conductive polymer materials based on low-density polyethylene and the random copolymer of propylene and ethylene are presented. It has been shown that modifying the polymer matrix with carbon-containing fillers allows thermally conductive polymer materials with both low and high electrical conductivity to be developed.

Comparison Study on CO2-Promoted Crystallization and Melting Behavior of Polypropylene: Homopolymer and Copolymers

Three types of polypropylene, namely propylene homopolymer (HPP), block copolymer of propylene with ethylene (CPP-B) and random copolymer of propylene with ethylene (CPP-R), were melted and isothermally crystallized in a self-designed vessel under supercritical carbon dioxide (Sc-CO2) atmosphere. The melting behavior and crystalline forms of crystallized samples were investigated using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The results showed that the presence of Sc-CO2 could improve the crystallinity for all three polypropylenes, and the promoting effect was more obivious with increasing CO2 pressure. In addition, it was observed that γ-crystals could be obtained in the CPP-B and CPP-R samples crystallized under Sc-CO2, while no γ-crystals were formed in HPP under the given conditions. The relative content of γ-crystals obtained in CPP-R samples was much higher than that of CPP-B, and 100% γ-phase could be formed in the CPP-R sample when subjected to 14 MPa Sc-CO2.

Ethylene–Propylene Segmented Copolymer as an in Situ Compatibilizer for Impact Polypropylene Copolymer: An Assessment of Rheology and Morphology

This work aims to probe the roles of ethylene–propylene segmented copolymer (EPS) in impact polypropylene copolymers (IPCs) by rheological and morphological investigations. A series of IPCs with different EPS contents and molecular structures are prepared by an atmosphere-switching polymerization process (ASPP). The Palierne emulsion model is used to describe the relationship between the rheological response to small amplitude oscillatory deformation and the morphology of IPC. It is found that this model describes well the linear viscoelastic responses of IPC, if the role of EPS is taken into account. An increase in the content of EPS and the length of its PP segments leads to a decrease in the size of the ethylene–propylene random copolymer (EPR) phase domains and the interfacial tension. These results strongly confirm the role of the EPS as a compatibilizer in the IPC system. The adhesion between the PP matrix and the EPR phase domains is enhanced by the presence of the EPS that is produced in situ duri...

Toughening effects of nucleating agent on impact polypropylene copolymer

ABSTRACTIn this study, the impact polypropylene copolymer (IPC) blended with the sorbitol‐based nucleating agent (NA) NX8000 was prepared and then characterized using a wide range of instrumentations. The results showed that the NA formed a fibril network which resulted in the increased viscosity of system and the decreased size of ethylene–propylene random copolymer (EPR) phase. The results of mechanical tests revealed “the brittle–ductile transition (BDT)” occurred while the ethylene content was between 3.5 wt % and 6 wt % and indicated that the impact strength of IPC was greatly improved by the addition of NX8000 when the EPR content was right over the critical value of BDT. The investigations provided valuable information for the further development of IPC materials and boarded its potential industrial applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40705.

On row-structures in sheared polypropylene and a propylene–ethylene copolymer

The crystallisation of polymers such as polyethylene or polypropylene from the melt is greatly influenced by the flow-thermal history prior to the crystallisation. We explore the influence of the chemical configuration of polypropylene based chains on the formation of row structures on crystallisation. We use a combination of in situ time resolved small-angle X-ray scattering, ex situ wide angle X-ray scattering with optical and scanning electron microscopy to show that row nuclei are formed in random copolymers of propylene with a limited amount of ethylene subjected to modest shear flow fields. We contrast observations performed using two homopolymers of isotactic polypropylene and one random copolymer of propylene and ethylene. We propose that it is not strictly necessary to argue that the row nuclei are already crystalline nor to invoke epitaxial crystallisation as the mechanism for the nucleation of lamellae, as similar structures can be formed on carbon nanotubes and fibrils of dibenzylidene sorbitol. The combination of microscopy and scattering provides a powerful approach to investigating these phenomena, especially as compared to either technique used in isolation.

Regulation of Phase Separation in PP/EPR In-Reactor Alloy and Its Effect on Crystallization Kinetics

The low molecular weight ethylene–propylene random copolymer (LEPR) in a polypropylene (PP)/EPR in-reactor alloy is replaced by high molecular weight EPR (HEPR). It is found that the phase separation rate of PP/HEPR alloy is much slower than that of PP/LEPR alloy. The effect of phase separation on the crystallization kinetics of PP/HEPR alloy is studied and compared with that of PP/LEPR alloy. The pre-phase-separated PP/HEPR alloy exhibits a faster spherulitic growth rate and overall crystallization rate, as compared with the directly quenched one. This is contrary to the PP/LEPR alloy and is interpreted in terms of the relative rate of crystallization and phase separation based on phase diagram. It is also observed that directly quenched PP/HEPR alloy has a larger long period after crystallization. This can be attributed to more inclusion of EPR-rich phase into inter-lamellae, which is advantageous to the mechanical properties.

Mechanical and dynamic mechanical properties of polyolefin blends: effect of blend ratio and copolymer monomer fraction on the compatibilisation efficiency of random copolymers

The mechanical and dynamic mechanical properties of isotactic polypropylene/high density polyethylene (PP/HDPE) blends, as a function of blend ratio and compatibiliser concentration were analysed. Ethylene propylene random copolymers (EPDM) with three different monomer fractions were used as compatibilisers. Compatibilisation improved the mechanical properties (except Young’s modulus) of the blends, considerably. The compatibiliser with 1:1 monomer fraction was found to be most efficient. A detailed discussion on the fundamental reasons responsible for the deterioration of properties in the absence of compatibilisers and the improvement of properties in the presence of compatibilisers was presented. The tensile strength of the uncompatibilised blends was theoretically modelled using Nielsen’s and Nicolais-Narkis models. The Young’s and storage moduli of uncompatibilised blends were compared with those predicted by various theoretical models. Attention was paid to correlate the mechanical properties of both compatibilised and uncompatibilised blends with their phase morphology.

Improved chemical composition separation of ethylene–propylene random copolymers by high-temperature solvent gradient interaction chromatography

High-temperature solvent gradient interaction chromatography (HT-SGIC) is a fast and efficient fractionation technique for the chemical composition analysis of olefin copolymers. The separation of ethylene-propylene random copolymers (EPRs) was achieved on a graphitic stationary phase, Hypercarb, at 160 °C by using linear solvent gradient elution from 1-decanol to 1,2,4-trichlorobenzene (TCB). In the present work, the solvent gradient profile was modified to improve the chromatographic separation of EPRs. With the aim to obtain a better resolution in separation, a slow increase in the volume fraction of TCB was applied. This allowed for a relatively large retention region for linear polyethylene (PE) chains on the column; thereby, a broader elution volume zone between the start of the gradient and the PE elution was achieved. The efficiency of this new gradient profile was demonstrated by analysing two fully amorphous EPR samples. Clear differences in the chemical composition of these EPR samples with similar ethylene contents have been proven by using this modified solvent gradient. The comprehensive chemical composition and microstructure analysis of the SGIC-separated fractions by FTIR revealed that ethylene/propylene (EP) copolymer chains were eluted according to their ethylene/propylene contents and E or P sequence lengths, even though they are distributed in a random manner. These results showed that the solvent composition is an important factor to affect the interactive adsorption or desorption behaviour of EP chains on Hypercarb. In this way, for the first time, the determination of the complex composition and chain structure of EPR samples was achieved within short analysis time, which is not possible till now using other fractionation techniques reported.

A model for the structures of impact polypropylene copolymers produced by an atmosphere-switching polymerization process

This work reports on the development of a model to establish the relationship between the structures of impact polypropylene copolymer (IPC), a high performance polymer material, and the characteristics of an atmosphere-switching polymerization process (ASPP), a new polymerization route. To calculate the complex structures of IPC, a detailed kinetic mechanism was proposed to describe the kinetic behavior of the active centers of Ziegler–Natta catalyst during ASPP. The semibatch ASPP for synthesizing IPC was carried out for the model validation. The model is capable of predicting the evolution of the compositional distributions of IPC as a function of switching frequency (SF), which is the main characteristic parameter of ASPP. ASPP not only allows controlling the contents of ethylene–propylene random copolymers (EPR) and ethylene–propylene segmented copolymers (EPS,) but also tuning the composition of EPS. Other applications of the model are discussed.

The trigonal form of i-PP in random C3/C5/C6 terpolymers

The formation of the trigonal structure of isotactic polypropylene (i-PP) in a series of random terpolymers of propylene (C3) with n-pentene-1 (C5) and n-hexene-1 (C6) by cooling from the molten state was investigated with the aim of assessing to what extent the intrinsic molecular disorder and the length of the side branch of the comonomers reflect on structuring kinetics and features of the crystal lattice. Experiments were performed on samples with an overall content of comonomers of ca. 25 mol% and show that, alike in the random copolymers of propylene with 1-pentene (C3/C5) or with 1-hexene (C3/C6), the trigonal modification of i-PP, δ form, develops upon cooling from the molten state also in the case of random terpolymers. At a constant molar fraction of propylene, the values of a and b axes of the unit cell linearly depend on the relative proportion of the two comonomers. Crystallinity and cell constant values as a function of terpolymer composition were provided by evaluation of data obtained from deconvoluted WAXD patterns. The development of crystallinity in isothermal conditions was followed at 0 and 20 °C, both by WAXD and DSC. Results were compared with those of the correspondent C3/C5 and C3/C6 copolymers and used to confirm the kinetic model proposed in a previous paper.