Polypropylene Copolymer Research Articles

Unveiling the Multiplicity of Silica Nanoparticles in Improving the Laser Powder Bed Fusion Processability of Polypropylene Copolymer

Unveiling the Multiplicity of Silica Nanoparticles in Improving the Laser Powder Bed Fusion Processability of Polypropylene Copolymer

SEGREGATED ELECTRICALLY CONDUCTIVE NANOCOMPOSITES BASED ON THERMOPLASTIC ELASTOMERS AND GRAPHITE

The paper presents the results of a study of the electrical conductive characteristics and a complex of physical-mechanical properties of graphite-based nanocomposites, a wide range of polyolefins - low-density polyethylene, high-density polyethylene, isotactic polypropylene, random copolymer of polypropylene, block copolymer of propylene with ethylene, ethylene/hexene copolymer and ethylene/butene-1 copolymer. For the considered nanocomposites based on polyolefins, the optimal concentrations of graphite were determined, at which the maximum values of electrical conductivity are achieved, within the range of 10–2–10–3 (Ωm)–1. A detailed description of the mechanism of tunneling and electronic electrical conductivity in the nanocomposites under consideration is given. Thermoplastic elastomers (TPE) based on polyolefins and ethylene-propylene-diene rubber have been developed. In a wide concentration range, the regularities of changes in the electrical conductivity of nanocomposites based on thermoplastic elastomers and nanodispersed graphite have been determined. When studying the physical-mechanical properties of TPE nanocomposites, the tensile strength, yield strength, elongation at break, bending strength, Vicat softening temperature, melt flow rate, and Young's modulus were determined. The regularity of the change in the dependence "stress-strain" for TPE depending on the content of ethylene-propylene-diene rubber has been established. Using the methods of derivatography, X-ray phase and SEM analyses, and electron microscopy, studies were carried out to assess the structural features of nanocomposites of thermoplastic elastomers depending on the ratio of the mixture components used. For visual interpretation, a schematic representation of the processes occurring in the interfacial region of thermoplastic elastomers is given. The method of X-ray phase analysis shows the regularity of the change in the degree of crystallinity of thermoplastic elastomers depending on the content of rubber and graphite. The principal possibility of obtaining flexible electrically conductive materials with predetermined properties by controlling the ratio of components in the composition of thermoplastic elastomers is shown. For citation: Kakhramanov N.T., Allahverdiyeva Kh.V., Gahramanli Yu.N., Mustafayeva F.A., Sadikhov N.M., Martynova G.S., Valimatova N.I., Gurbanova R.V. Segregated electrically conductive nanocomposites based on thermoplastic elastomers and graphite. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 11. P. 122-137. DOI: 10.6060/ivkkt.20246711.7045.

Impacts of Photooxidation on Commercially Available Homo and Copolymers of Polypropylene on Their Microstructure and Mechanics: A Cross‐Sectional Analysis

ABSTRACTPolyolefin degradation is widely studied to assess the lifetime of packaging materials. In this work, a combination of bulk (DSC, GPC, 13C‐NMR, XRD), surface (FTIR) and cross‐sectional characterization (Raman spectroscopy and nanoindentation) was used to examine changes in the mechanical properties and microstructure of two different commercially‐available polyolefins, with similar crystallinities, produced by injection molding—a polypropylene homopolymer (PPH) and a polypropylene random copolymer (PPRC)—aged under accelerated UV‐A conditions. The aim was to characterize the variations in the crystallinity and microstructure across the cross‐section of these materials. Our results suggest that the presence of ethylene comonomer units in PPRC results, on average, in smaller crystal dimensions, leads to improved packing, and a more homogeneous microstructure and hardness across the cross‐section of the sample. The ethylene monomers stabilize PPRC from oxidation during the first 14 days of accelerated aging, but eventually the rate of degradation matches the PPH at 28 days of aging, probably because of the higher surface area to volume ratio of the smaller crystals. The work emphasizes the importance of incorporating ethylene comonomers into polyolefins to limit variation of the microstructure across the core to the skin layer, for improved future design of packaging that degrades fully.

Random and Block Copolymers of Isotactic Polypropylene with Higher α-Olefins: The Role of the Chain Topology on the Side-Chains Confined Crystallization

Random and Block Copolymers of Isotactic Polypropylene with Higher α-Olefins: The Role of the Chain Topology on the Side-Chains Confined Crystallization

Crystallization Behavior of Block Copolymers of Isotactic Polypropylene and Linear Low-Density Polyethylene

Crystallization Behavior of Block Copolymers of Isotactic Polypropylene and Linear Low-Density Polyethylene

Crystallization Kinetics of Crystalline–Crystalline and Crystalline–Amorphous Block Copolymers of Linear Polyethylene and Isotactic Polypropylene

Crystallization Kinetics of Crystalline–Crystalline and Crystalline–Amorphous Block Copolymers of Linear Polyethylene and Isotactic Polypropylene

Crystallization, mechanical, and heat resistance performances of copolymer polypropylene modified by α nucleating agent

AbstractPolypropylene (PP) was a very practical and important thermoplastic, which was widely used in various fields due to its low cost, universal, and corrosion resistance. However, the moderate mechanical and heat resistance properties of PP limited its application in some special fields. In this paper, nucleating agents NP‐657 were added to further improve its mechanical and heat resistance performances of PP (300H). Furthermore, the heterogeneous nucleation of NP‐657 reduced the crystal size and increased the crystal density of 300H. With the rise of NP‐657 content, the crystallization rate of different PP systems increased significantly, such as the t1/2 of 300H‐0.2 reduced by 31.9 min in comparison with that of 300H at 140°C. At the same time, the crystallinity of 300H‐0.05 with 0.05 wt.% NP‐657 increased by about 5.96% compared with 300H. In addition, 300H‐0.05 has the highest tensile strength (23.9 ± 0.6 MPa), flexural modulus (1273.3 ± 67.3 MPa), and the highest thermal deformation temperature (88.5 ± 7.7°C) in different PP systems. In general, this paper provided a reference for the fabrication of PP with satisfactory mechanical and heat resistance performances.Highlights 300H‐0.05 had a maximum crystallinity of 40.8 ± 0.2% in different PP systems. The flexural modulus of 300H‐0.05 was 434 MPa higher than that of 300H. The tensile strength of 300H‐0.05 increased to 23.9 ± 0.6 MPa. 300H had the highest thermal deformation temperature of 88.5 ± 7.7°C.

Modeling and analysis of polypropylene copolymer properties and pressure stability for integrated tubular loop reactor and MZCR

In the context of the emerging multizone circulating reactor (MZCR) operating with gas–solid phases, maintaining pressure balance is crucial for both reactor stability and achieving intended product quality. In this study, the method of moments, reactor model and pressure balance model are coupled to model and analyze an entire process flow for propylene (co)polymerization, which integrates a pre-polymerization tubular loop reactor (TLR) with a main polymerization MZCR. The modeling results unveil the relevance of pre-polymerization in the entire MZC process flow. Additionally, the influence of typical operating parameters on both the pressure stability and copolymer properties is investigated. To further visually identify the pressure-stable boundary of the MZCR, a method based on analyzing the pressure balance loop is proposed. The current study has illustrated the variation trends of pressure drops and product properties under typical operating conditions, identifying an operational range essential for reactor safety.

Upgrading properties and circularity of the recycled flexible polypropylene by developing composites with an optimal combination of a fumed silica and maleated polypropylene copolymer: Influence of the addition of copolymer, type of fumed silica and the silica/copolymer ratio on packaging properties

Rigid polypropylene is mechanically recycled but flexible polypropylene is mostly used in energetic valorization because of the poor properties of the recycled polymer. A recycled polypropylene-based composite with outstanding properties for flexible food packaging was developed. For the first time, the influence of maleated polypropylene copolymer addition and the fumed silica/copolymer ratio on the packaging properties of recycled flexible polypropylene under the effects of silica hydrophilicity was investigated. The structural, morphological, thermal, mechanical, melt flow, overall migration, water vapor barrier and sealing properties of the developed nanocomposites were analyzed. Prominently, the addition of 1:1 maleated polypropylene and hydrophobic nanosilica improved the global performance of all tested methods. The recycled polypropylene had an overall migration to olive oil of 17 mg dm−2, exceeding the limit allowed for food packaging, but the developed added-value composite reduced it to the tolerance limit according EU legislation. The seal strength was drastically increased by 50 % with adhesive peeling, high thermal stability, and well-dispersed particles without affecting the ductility.

Ternary Blends of Polypropylene Copolymer, Polyethylene and Thermoplastic Polyurethane for Fused Deposition Modeling Three-Dimensional Printing Technology: Preparation, Printing and Properties.

A set of filaments for fused deposition modeling (FDM) three-dimensional (3D) printing was developed from the ternary blends of polypropylene random copolymer (PPR or P), high density polyethylene (HDPE or E), and thermoplastic polyurethane (TPU or T), formulated with different weight ratios of polymers, i.e., 80:20:0, 70:20:10, 60:20:20, and 50:20:30, respectively, and coded as P80E20T0, P70E20T10, P60E20T20, and P50E20T30, respectively. The blend composition was optimized to obtain both high-quality filaments with low ovality and FDM-fabricated objects with minimized warpage and good interlayer bonding. The crystallization and crystalline morphologies of individual polymers in the blend filaments were comprehensively analyzed by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and polarized light optical microscopy (PLOM). It was found that HDPE acted as crystalline nuclei for PPR crystallization; PPR appeared to crystallize more readily at a slightly higher T c with somewhat greater crystallinity. Meanwhile, TPU explicitly restricted the crystallization of both polyolefins; decreases in both the size and growth rate of their spherulites were observed. The PLOM and SEM results indicated that the surface morphology of the ternary blends was not absolutely phase-separated; an increasing number of TPU droplets inherently imbedded at the boundary of the polyolefin aggregate phase when a higher TPU quantity was integrated. Consequently, the warpage deformation and layer interfusion of the as-printed articles were most remarkably improved when P50E20T30 was used. Nonetheless, the incorporation of relatively flexible TPU material into the PPR-based filaments inevitably reduced their mechanical performance; the flexural strength and modulus of the highest-quality 3D-printed P50E20T30 object were fairly decreased by approximately 25% and 12%, respectively.

Effect of short-term sample storage and preparatory conditions on losses of 18 per- and polyfluoroalkyl substances (PFAS) to container materials

There is a lack of agreement on a suitable container material for per- and polyfluoroalkyl substances (PFAS) analysis, particularly at trace levels. In this study, the losses of 18 short- and long-chain (C4–C10) PFAS to commonly used labware materials (high-density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), polypropylene co-polymer (PPCO), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), and glass were investigated. The influence of sample storage and preparation conditions, i.e., storage time, solvent composition, storage temperatures (4 °C and 20 °C), and sample agitation techniques (shaking and centrifugation) on PFAS losses to the container materials were investigated. The results showed higher losses for most of the considered PFAS (up to 50.9%) in 100% aqueous solutions after storage for 7 days regardless of the storage temperature compared to those after 3 days. Overall, the order of losses to different materials varied for individual PFAS, with the highest losses of long-chain PFAS observed to PP and HDPE after 7-day storage at room temperature. The addition of methanol to aqueous PFAS solutions reduced the losses of long-chain PFAS to all tested materials. The use of sample centrifugation and shaking did not influence the extent of losses for most of the PFAS in 80:20 water:methanol (%, v/v) to container materials except for 8:2 fluorotelomer sulfonic acid (8:2 FTS), 9-chlorohexadecafluoro-3-oxanone-1-sulfonic acid (9Cl-PF3ONS), perfluorodecanoic acid (PFDA) and 4:2 fluorotelomer sulfonic acid (4:2 FTS). This study demonstrates lower losses of both long- and short-chain PFAS to glass and PET. It also highlights the need for caution when deciding on sample preparatory steps and storage during the analysis of PFAS.

Impact of graphene concentration on crystallinity, rheological, and mechanical characteristics of a polypropylene copolymer

This study examines the impact of graphene nanoplatelets (GNP) on the properties of a CP442XP polypropylene (PP) copolymer. GNP was added in concentrations of 0.5%, 1%, and 2% by mass, alongside a 2% flake graphite blend. An objective of this work is to prepare the material using industrial equipment. Therefore, PP/GNP composite production involved twin-screw extrusion for mixing and injection molding to produce samples. Characterization as crystallinity by Differential Scanning Calorimetry (DSC), mechanical and thermal properties, morphology and rheological properties are investigated. Results indicate that 0.5% and 1% GNP enhance PP crystallinity, due to GNP particles acting as nucleation sites. However, 2% GNP reduced crystallinity, possibly due to poor dispersion. Besides that, the PP copolymer usually starts with a better impact strength, compared to a PP homopolymer. Mechanical analysis showed that 1% GNP in PP improves elasticity but reduces impact strength at higher concentrations, indicating a stiffer polymer matrix. Rheological analysis revealed that 1% GNP in PP lowers viscosity at shear rates of 10 to 100 1/s, suggesting less energy required for polymer processing. In summary, low GNP concentrations beneficially modify the mechanical properties and rheology of PP copolymers. Some properties are possible to achieve even using standard industrial equipment.

Rheological insights into the degradation behavior of PP/HDPE blends

The (re-)processing and degradation behavior of polypropylene (PP) blends with high-density polyethylene (HDPE) is a crucial topic in mechanical recycling due to the prevalence of PP/HDPE mixtures. In particular, small amounts of cross-contamination (below 10.0 wt.%) between these polyolefins are quite common. While much empirical data is available, systematic studies on such blends are scarce and rarely account for the polymers’ chain structure. This study employs time-resolved rheology, atomic force microscopy (AFM), differential scanning calorimetry (DSC) and chemiluminescence techniques to study the degradation of different PP types containing 0.5 to 10.0 wt.% of HDPE. It is observed that the addition of small amounts of HDPE can result in a prominent change in the viscoelastic properties of PP during the thermo-oxidative degradation. The substantial evolution of elasticity in the blends is mainly related to the gelation of fine PE particles dispersed within the PP matrix. It is also shown that a smaller viscosity ratio between the blend components can lead to a more significant degradation through morphology alterations. Remarkably, time-resolved rheology studies revealed that even a small amount of HDPE (2.5 wt.%) can lead to a reduction in the thermo-oxidative stability of the PP/HDPE blend through excessive branching/crosslinking of the HDPE phase. This effect was particularly more pronounced when the PP contained an ethylene comonomer in its backbone. The finer morphology of PE particles in PP copolymer can exacerbate the thermo-oxidative stability of the blend. These insights are essential in designing new life cycles for recycled PP cross-contaminated with HDPE, typically found in the light fraction of municipal solid plastic waste.

Largely Improved Creep Resistance and Thermal-Aging Stability of Eco-Friendly Polypropylene High-Voltage Insulation by Long-Chain Branch-Induced Interfacial Constraints.

Polypropylene (PP)-based composites have attracted numerous attention as a replacement of prevailing cross-linked polyethylene (XLPE) for high-voltage insulation due to their ease of processing, recyclability, and excellent electrical performance. However, the poor resistances against high-temperature creep and thermal aging are obstacles to practical applications of PP-based thermoplastic high-voltage insulation. To address these problems, in this Letter, we synthesized an impact polypropylene copolymer (IPC) containing multifold long-chain branched (LCB) structures in phases, especially the interfaces between the PP matrix and the rubber phase. The results indicated that the structural stability of LCBIPC was significantly enhanced under extreme conditions. In comparison to IPC (without LCB structures), 24.1% less creep strain and 75.2% less unrecoverable deformation are achieved in LCBIPC at 90 °C. In addition, the thermal aging experiments were performed at 135 °C for 48 and 88 days for IPC and LCBIPC, respectively. The results show that the resistance against thermal aging was also enhanced in LCBIPC, which showed a 133% longer thermal aging life compared to IPC. Further results revealed that the interfacial layer between the PP matrix and the rubber phase was constructed in LCBIPC. The two phases are tightly linked by chemical bonds in LCB structures, leading to enforced constraints of the rubber phase at the micro level and better resistance performance against creep and thermal aging at the macro level. Evidently, the reported eco-friendly LCBIPC thermoplastic insulation shows great potential for applications in high-voltage cable insulation.

Industrially relevant injection moulding apparatus for in situ time-resolving small-angle X-ray scattering measurements

This work presents the design and construction of an automated industrial injection moulding apparatus that can be used with a typical multi-user beamline such as the NCD-SWEET small-angle X-ray scattering at the ALBA Synchrotron Light Source. This apparatus is focused on developing an understanding of how the mould temperature and the injection temperature and pressure affect both the orientation and morphology of the semi-crystalline polymer used to fabricate the injected parts. The system design follows current industrial practice and enables the collection of time-resolved X-ray scattering data at several points within the mould cavity, so we can understand the 4D morphology. In this work we show the effectiveness of the equipment using some results from the injection moulding of a random copolymer of polypropylene and that it can be used with a more demanding material such as polyhydroxybutyrate. This can be seen as the first step toward a multiscale digital twin for injection moulding.

Exploring the effect of cooling rate on non-isothermal crystallization of copolymer polypropylene by fast scanning calorimetry

Exploring the effect of cooling rate on non-isothermal crystallization of copolymer polypropylene by fast scanning calorimetry

Characterizing Microplastic Pollution and Microbial Community Status in Rice Paddy Soils Across Varied Environmental Settings in Songjiang, Shanghai: An Analysis of Morpho-Chemical Characteristics

Microplastic (MP) pollution poses a huge threat to rice fields, but the distribution characteristics of MPs in farmlands of different types of areas are still uncertain. In this work, 24 samples from 12 rice fields of four different land-use types (Factory, highway, greenhouse/mulching and normal fields) were collected from Songjiang, Shanghai. From our selected sites, it was found that MP abundances were in the range of 233.33- 173.33 particles/kg in rhizosphere and bulk soil. MP distribution results showed that over 40% of particles were less than 1 mm and MP sizes ranging between 1 and 5 mm represented the greatest proportion. According to our study, MP in rhizosphere soil has the highest abundance (233.33 ± 57.73 particles/kg) than bulk soil. The particle shape classified as fragment (with edges and angular) was the most frequent shape found near factory areas, with an abundance of approximately 37.10%. Copolymers of polypropylene- polyethylene (PP/PE) at 24.30% were the most abundant polymers in rice lands in both bulk and rhizosphere soils; following is polystyrene (PS) at 21.40%, respectively. Most of the particles found in soils were white. Statistical analyses showed that fields near factories and fields where plastic mulching (mulch film and greenhouse crops) was used had a significantly higher particle abundance for bulk and rhizosphere soils, hence identifying plastic mulching as a major contributor to MP pollution in paddy soils. In industrial areas, MP can also be generated by released waste or by air. Microbial studies in rice roots, rhizosphere soil, and bulk soil show variation in the abundance of different species and genera. The dominant bacterial phyla in rice roots are Proteobacteria, Actinobacteriota, Firmicutes, and Bacteroidota. These microbes have been observed and can be impacted by the presence of MPs. Rhizosphere soil and bulk soil have an abundance of Chloroflexi, Actinobacteriota, Proteobacteria, Firmicutes, and Acidobacteriota. The specific effects on the microbial community structure depend on factors like MP type, concentration, and exposure duration. As our study was field-based, the significant effect of a specific type or concentration of MP was difficult to identify. Variation analyses of MP characteristics revealed that paddy lands were more likely to contain fragment shapes and large MP particles (1-5 mm). Also, rhizosphere soils were likely to contain fragment shapes and pony-size MPs (0.02-0.2 mm). Differences among rice fields may depend on various reasons, such as using slow- release fertilizers, mulching plastic application, irrigation, atmospheric fallout, etc. This study provides some proper evidence about the characteristics of MP pollution in rice fields of Songjiang and explores some probable conditions and predominant MP sources in rice fields.

Development of a Measurement System Using Infrared Spectroscopy-Attenuated Total Reflectance, Principal Component Analysis and Artificial Intelligence for the Safe Quantification of the Nucleating Agent Sorbitol in Food Packaging.

Sorbitol derivatives and other additives are commonly used in various products, such as packaging or food packaging, to improve their mechanical, physical, and optical properties. To accurately and precisely evaluate the efficacy of adding sorbitol-type nucleating agents to these articles, their quantitative determination is essential. This study systematically investigated the quantification of sorbitol-type nucleating agents in food packaging made from impact copolymers of polypropylene (PP) and polyethylene (PE) using attenuated total reflectance infrared spectroscopy (ATR-FTIR) together with analysis of principal components (PCA) and machine learning algorithms. The absorption spectra revealed characteristic bands corresponding to the C-O-C bond and hydroxyl groups attached to the cyclohexane ring of the molecular structure of sorbitol, providing crucial information for identifying and quantifying sorbitol derivatives. PCA analysis showed that with the selected FTIR spectrum range and only the first two components, 99.5% of the variance could be explained. The resulting score plot showed a clear pattern distinguishing different concentrations of the nucleating agent, affirming the predictability of concentrations based on an impact copolymer. The study then employed machine learning algorithms (NN, SVR) to establish prediction models, evaluating their quality using metrics such as RMSE, R2, and RMSECV. Hyperparameter optimization was performed, and SVR showed superior performance, achieving near-perfect predictions (R2 = 0.9999) with an RMSE of 0.100 for both calibration and prediction. The chosen SVR model features two hidden layers with 15 neurons each and uses the Adam algorithm, balanced precision, and computational efficiency. The innovative ATR-FTIR coupled SVR model presented a novel and rapid approach to accurately quantify sorbitol-type nucleating agents in polymer production processes for polymer research and in the analysis of nucleating agent derivatives. The analytical performance of this method surpassed traditional methods (PCR, NN).

Developing polypropylene copolymer powder with a wide sintering window for laser powder bed fusion via extrusion and in-blend annealing

Converting cheap resins like polypropylene (PP) copolymer into near-spherical powder materials with a wide sintering window (SW) is highly desired for broadening the feedstock palette for laser powder bed fusion (PBF-LB/P). Herein, a novel “melt extrusion-in blend annealing” strategy was proposed to achieve this aim, which involved dispersing the copolymer into a water-soluble matrix and then annealing the blend at temperatures near the melting point of the copolymer for a certain time. Spherical PP copolymer powders with largely widened SW (>30ºC) were obtained after removing the matrix. Two advantageous effects of in-blend annealing were identified. The first one was the elevation in the onset melting temperature due to crystal perfection. Another one was the decline in the onset crystallization temperature, which was suggested to relate to the migration of heterogeneous nuclei out of copolymer particles but required further verification. The obtained powder with optimized SW was fabricated into parts with low warpage at the cost of a slightly inferior mechanical performance possibly related to material degradation and changes in the crystal structure. The strategy proposed offers a promising prospect for developing new powders with optimized processing features for PBF-LB/P from commercially available resins.

Combining Cyclic Units and Unsaturated Pendant Groups by Propene/1,5-Hexadiene Copolymerization Toward Functional Isotactic Polypropylene.

The precise use of a widely available and inexpensive metallocene catalyst enabled the synthesis of isotactic polypropylene copolymers characterized by the copresence of randomly distributed cyclic units in the backbone and unsaturated pendant units employing 1,5-hexadiene as comonomer. Optimization of the polymerization conditions avoided the cross-linking phenomena that negatively affects the material processing and final properties, resulting in good yields of samples featuring high molecular masses and a precisely controlled microstructure. Such polypropylene-based copolymers exhibit a broad spectrum of properties ranging from thermoplastic to surprising elastomeric behavior, with the additional value of being functionalizable by post-polymerization reactions.