Weight Polypropylene Research Articles

Influence of MIL-53 on the catalytic performance of metallocene in propylene polymerization

In this study, we investigate the application of metal-organic frameworks (MOFs) as a support for metallocene catalysts in the polymerization of propylene. MOFs such as MIL-53 and other conventional supports, SBA-15 and SiO2, were employed to immobilize the Me2Si(2-Me-4-PhInd)2ZrCl2 catalyst activated with methylaluminoxane (MAO). The effects of the physicochemical properties of these supports on catalytic performance and polymer properties were investigated. MIL-53, characterized by its channel structure, facilitated higher molecular weight polypropylene production and exhibited double the catalytic activity of SBA-15 and SiO2 supports. The MIL-53/MAO/Me2Si(2-Me-4-PhInd)2ZrCl2 catalyst also demonstrated higher comonomer incorporation and lower polymer melting points. The higher activity, elevated molecular weight, and increased reactivity towards 1-hexene of the MIL-53/MAO/Me2Si(2-Me-4-PhInd)2ZrCl2 catalyst are attributed to the electronic and steric effects of MIL-53. This study underscores the significant role of MOF structure in influencing polymerization behavior and highlights the potential of MOF-supported catalysts for tailored polymer properties.

Dynamic behavior of melt electrospinning of blended polypropylene

Melt electrospinning is a promising process for fiber production without the need for solvents and with potential applications in various fields. In this study, we investigated the dynamic behavior of melt electrospinning under different blending ratios and process conditions. We used high melt flow index polypropylene and low molecular weight polypropylene, which were blended to lower the melt viscosity, and fibers were successfully manufactured through the melt electrospinning process. The effects of blending ratio and applied voltage on jet and drop formation, as well as fiber morphology, were examined. The results showed that blending low-molecular-weight polypropylene significantly influenced the jet and drop areas, leading to fluctuations in jet morphology. The size of the applied high voltage also had a high effect on the fiber diameter. Additionally, the viscosity reduction achieved through blending allowed for continuous jet formation and improved fiber production. These results provide valuable insights into controlling the process parameters and blending ratios in melt electrospinning, enabling the establishment of stable electrospinning conditions and precise control of fiber diameter.

Facilely prepare ultra-high molecular weight polypropylene loose nanofiltration membrane for efficient dye/salt separation

The simple strategies and processes for preparing nanofiltration (NF) membranes with well-pore channels and high separation efficiency have received growing attention in academia. Herein, ultra-high molecular weight polypropylene (UHMWPP) has been successfully fabricated into high-performance loose NF membranes through thermally induced phase separation (TIPS). The results showed that the as-prepared UHMWPP loose NF membrane has a good water permeance (17.7 L m−2 h−1 bar−1), a high RB rejection (99 %), and a low inorganic salt retention rate (NaCl: 1.9 %), which makes the loose NF membrane a potential choice for dye/salt separation. In addition, the membrane also has good antifouling properties, acid and alkaline resistance, and long-term stability. Thus, this work offers a viable and pragmatic technical approach for addressing high-salt printing and dyeing wastewater, with broad prospects for application and practical value.

A hybrid steric ligand modification strategy promotes propylene (co)polymerization

Recently, a Hybrid Steric Ligand Modification (HSLM) strategy has been shown to significantly increase the polymerization activity and the branching degree of the resulting (co)polymers in the ethylene (co)polymerization via α-diimine catalysts. In this study, the HSLM strategy was employed for propylene (co)polymerization using a group of α-diimine Pd(II) catalysts with bulky hybrid ligands. The HSLM catalysts (Pd1-4) produced polypropylene with high molecular weights (45.4–156.9 kg/mol) and resulted in significantly high levels of activity (105 g mol−1 h−1). Additionally, nearly half of the propylene underwent chain straightening (1,3-enchainment = 43–46 %). Our findings suggest that Pd1-4 catalysts are more effective than the symmetrical catalysts Pd5-6 in producing high molecular weight polypropylene with high activity. Among all the catalysts tested, Pd4 with 4-tert-butylphenyl displayed the highest polymerization activity and molecular weight, although with lowest branching densities. It is suggested that the HSLM may provide a more open spatial configuration around the metal center, which facilitates the coordination and insertion of propylene molecules as well as chain walking. The hybrid Pd(II) catalysts showed moderate activity during the copolymerization of propylene with MA. The copolymers produced had low molecular weights (3.1–11.2 kg/mol), high branching densities (120–211/1000C), and high incorporation ratios (8.82–18.08 mol%). The copolymerization activity was highest with 4-tert-butylphenyl Pd4. The resulting P-MA copolymers had the highest molecular weight, the largest branching degree, and the lowest incorporation ratios.

On the Mechanical, Thermal, and Rheological Properties of Polyethylene/Ultra-High Molecular Weight Polypropylene Blends.

The novel ultra-high molecular weight polypropylene (UHMWPP) as a dispersed component was melt blended with conventional high-density polyethylene (PE) and maleic anhydride grafted-polyethylene (mPE) in different proportions through a kneader. Ultra-high molecular weight polypropylene is a high-performance polymer material that has excellent mechanical properties and toughness compared to other polymers. Mechanical, thermal, and rheological properties were presented for various UHMWPP loadings, and correlations between mechanical and rheological properties were examined. Optimal comprehensive mechanical properties are achieved when the UHMWPP content reaches approximately 50 wt%, although the elongation properties do not match those of pure PE or mPE. However, it is worth noting that the elongation properties of these blends did not match those of PE or mPE. Particularly, for the PE/UHMWPP blends, a significant drop in tensile strength was observed as the UHMWPP content decreased (from 30.24 MPa for P50U50 to 13.12 MPa for P90U10). In contrast, the mPE/UHMWPP blends demonstrated only minimal changes in tensile strength (ranging from 29 MPa for mP50U50 to 24.64 MPa for mP90U10) as UHMWPP content varied. The storage modulus of the PE/UHMWPP blends increased drastically with the UHMWPP content due to the UHMWPP chain entanglements and rigidity. Additionally, we noted a substantial reduction in the melt index of the blend system when the UHMWPP content exceeded 10% by weight.

Evaluating the molecular weight distribution of ultrahigh molecular weight polypropylene through rheology

This work investigates the possibility of obtaining the molecular weight distribution (MWD) of linear ultrahigh molecular weight (UHMW) polypropylene (PP) through rheology. To this end, the linear viscoelastic response of a set of UHMWPP samples is measured over the largest possible frequency range. The terminal relaxation is achieved by running creep experiments and converting the compliance in dynamic moduli. A time–temperature concentration principle, recently validated for UHMW polyethylene, is also applied to obtain the terminal relaxation of the sample with the largest molecular weight. The linear rheological response is correlated with gel permeation chromatography (GPC) results by means of the mixing rule based on the relaxation modulus. The implementation of such a rule requires the knowledge of some material parameters governing the stress relaxation of the polymer. Since they are unknown in literature for PP, they are estimated from the comparison between the viscoelastic spectra and the GPC distributions of three lab-made UHMWPPs with narrow polydispersity. Such parameters are then used as a basis to predict the MWDs of two UHMWPP samples with large polydispersity. The variability of the parameters upon molecular weight and polydispersity is assessed by applying the mixing rule to two different PP samples with lower molecular weights, one with narrow polydyspersity and another one with broad polydispersity. As the GPC curves of the samples are available, first the direct problem of estimating the rheological response from MWD and then the inverse problem of obtaining the MWD from the rheological data are solved. An overall satisfactory agreement is found between the calculated and measured MWD for the two samples, with both the direct and inverse approach.

The role of alkoxysilanes in propylene polymerization catalysis. A study of model Ti(Oi‐C3H7)4‐Al(C2H5)2Cl/Mg(C4H9)2 catalyst system

AbstractThe article describes the modifying effect of methylcyclohexyldimethoxysilane (CH3)(cyclo‐C6H11)Si(OCH3)2 in propylene polymerization reactions with a pseudo‐homogeneous catalyst system: Ti(Oi‐C3H7)4‐Al(C2H5)2Cl/Mg(C4H9)2. This catalyst system is a convenient model for the analysis of modifier effects (effects of ‘external donors’) in supported Ziegler–Natta polymerization catalysts of the fourth generation. A combination of chromatographic, spectroscopic and calorimetric data for crystalline and amorphous fractions of polypropylene prepared in the presence of the silane shows that it has a dual modification effect: (i) the silane is a potent poison of stereo‐aspecific active centers in the catalyst (the centers producing amorphous polypropylene fraction) and (ii) silane molecules coordinate at isospecific centers in the catalyst and changes their nature: the centers produce isotactic polypropylene of higher molecular weight and a higher isotacticity level. © 2023 Society of Industrial Chemistry.

Fabrication of novel biocomposite made of chemically treated sludge fibers and various molecular weight polypropylene

The effect of the chemical treatment of paper mill sludge fibers and polypropylene molecular weight were studied relative to the physical, mechanical, and morphological properties of a novel cellulosic biocomposite. Paper mill sludge fibers were treated with acetic anhydride, and succinic anhydride was mixed with maleic anhydride polypropylene (MAPP) and coupling agent (0 and 3%). The ratio of fibers and polymer materials was considered 30 to 70, which was manufactured by the hot-pressing method at 180 °C. Water absorption, volume swelling, and contact angle were examined on each specimen according to ASTM standards, while Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) explored the efficiency of chemical modification of fibers and the morphology of biocomposites, respectively. The results showed that chemical treatment of fibers reduced the water absorption and volumetric swelling. Both tensile and flexural strength were increased with chemical treatment using the coupling agent. Comparison of fibers treated with succinic acid and acetic acid showed that the succinic acid enhanced the mechanical properties better than the acetic acid treatment. Finally, FTIR analysis showed that the hydroxyl groups decreased, and SEM images indicated the interface between fibers and polypropylene improved via chemical treatment of sludge fibers.

Properties of blends of ultra-high molecular weight polypropylene with various low molecular weight polypropylenes

To enhance the ease of processability of the ultra-high molecular weight polypropylene (UHMWPP), the various low molecular weight polypropylenes (LMWPPs) blended with the UHMWPP via a facile melt blending process. The effect of the LMWPPs component on the UHMWPP component on its rheological and mechanical properties was characterized using various measurement techniques. The processability of the UHMWPP was improved drastically with the introduction of LMWPP components as the melt index of the blend increased. As the LMWPP content increases, the mechanical properties of the blends tend to increase or decrease, depending on the type of LMWPP.

Delamination behaviour and surface morphology of wholly thermoplastic composites using different ultra-high molecular weight thermoplastic fabrics with pristine and toughened Elium resin under Mode I loading

Current research investigates the manufacturing and bonding characteristics of wholly thermoplastic composites with thermoplastic fibres and acrylic Elium® resin and toughened Elium®IM with 10% weight acrylonitrile butadiene styrene (ABS) particles under Mode I loading. Ultra-high molecular weight polypropylene (UHMWPP)/Elium® IM and UHMWPP/Elium® composites have shown 43.9% and 24.5% higher critical energy release rate compared to epoxy composite systems, while a similar trend was observed in the case with composites with polyester as the reinforcement system. For ultra-high molecular weight polyethylene (UHMWPE)/Elium®, the increase was only 13.7% but with the use of toughened thermoplastic variant, the increase was found to be 36.8% higher. Detailed microscopic examination reported fibre bridging, pull-out, strong fibre–matrix adhesion, riverlines, and matrix deformation owing to the ductile characteristic of Elium® resin. ABS-modified Elium®IM composites have shown rough matrix fracture surface and there was internal cavitation of ABS particles followed by crack growth and local shear band formation.

Understanding the impact properties and damage phenomenon of ultra-lightweight all-thermoplastic composite structures

The current research presents the details of the impact properties of novel all-thermoplastic composite structures with different thermoplastic fabrics like ultra‐high molecular weight polyethylene (PE), ultra‐high molecular weight polypropylene (PP), and Polyester (PES) with room temperature curable acrylic Elium® (EL) thermoplastic resin. The low-velocity impact performance is studied at five energy levels (10J-50J), and the performance is compared to baseline epoxy (EP) composites, and their failure mechanisms are deduced through optical and SEM examination. PP/ELC, PE/ELC and PES/ELC all-thermoplastic composites have shown up to 34.68%, 24.46%, 15.35 % higher load carrying capability and 27%, 11.21%, 8.43% lower absorbed energy compared to PP/EPC, PE/EPC, and PES/EPC composites respectively due to the lesser damage and high toughness of the matrix. The major damage energy was found to be 10.55% higher due to the more elastic and plastic deformation mechanisms before the onset of the damage. PP/ELC, PE/ELC, and PES/ELC have shown 32%, 66.7% and 51% improvement in structural integrity as opposed to epoxy counterparts. ELC composites have shown matrix cracks, and strong fibre matrix adhesion with thermoplastic fibres properly embedded in the acrylic resin, while clean fibre pull-out and bare fibres were observed for EPC composites.

On the Mode I and Mode II Delamination Characteristics and Surface Morphological Aspects of Composites with Carbon-Thermoplastic Hybrid Fabrics and Innovative Liquid Thermoplastic Resin.

In the current research, the delamination behavior under Mode I and Mode II loading for the hybrid carbon-thermoplastic fabrics in conjunction with novel liquid thermoplastic acrylic Elium® resin processable at ambient conditions was studied. The experimentation by incorporating doublers methodology, studying the performance under Mode I and Mode II loading, and understanding failure mechanisms using surface morphological fractography is deliberated. Hybrid Carbon-Ultra-high molecular weight polyethylene (UHMWPP)/Elium® composite has shown a 22.81% higher GIC and a 22.2% higher GIIC than Carbon-UHMWPP/Epoxy composite. On the contrary, the Carbon_Ultra-high molecular weight polypropylene (UHMWPE)/Elium® has shown an 11.11% higher Mode I critical energy release rate (GIC) and a 7.58% higher Mode II critical energy release rate (GIIC) than Carbon_UHMWPE/Epoxy composite. Hybrid fiber reinforced thermoplastic composites have shown severe plastic deformation of the matrix, rough fracture surface, and micro-cracks on the de-bonding surface, extensive fiber bridging, and crack branching which contributed to the improvement in the delamination behavior. Hybrid fiber architecture is also found to be detrimental by inducing crack arresting mechanisms including the tortuous crack path and the resin-rich pockets path due to the mismatch of the size of the fiber yarns.

Rheological, Mechanical, and Thermal Properties of Ultrahigh Molecular Weight Polypropylene/Low Molecular Weight Polypropylene Blends

Ultra-high molecular weight polypropylene (UHMWPP), with a molecular weight of more than 106 g/mol, is expected to have superior properties, such as high mechanical strength, high thermal properties, high chemical resistance and outstanding tribological properties. However, UHMWPP has a very poor processability due to its high melt viscosity. Therefore, we aimed to improve processability of UHMWPP by blending it with a low molecular weight polypropylene (LMWPP). We attempted to improve the interfacial miscibility and intermolecular entanglement of the UHMWPP/LMWPP system by using a kneader machine. The addition of LMWPP tended to change the mechanical, thermal, and rheological properties of the blend system.

On the Mode II fracture toughness, failure, and toughening mechanisms of wholly thermoplastic composites with ultra-lightweight thermoplastic fabrics and innovative Elium® resin

Current work presents the first investigation on the Mode II fracture toughness of room temperature curable acrylic Elium® resin and toughened Elium®IM with 10% weight acrylonitrile butadiene styrene (ABS) particle with different thermoplastic fabrics like Ultra-high molecular weight polyethylene (UHMWPE), Ultra-high molecular weight polypropylene (UHMWPP), and polyester. The testing methodology using doublers, performance under Mode II loading and understanding the failure and toughening mechanisms is deliberated. GIIC of UHMWPP/Elium®IM composite was found to be 33.3% higher than that of UHMWPP/Epoxy composite. Polyester/Elium® composites have 27.02% higher GIIC than Polyester/Epoxy composites while Polyester/Elium®IM composites exhibited the highest GIIC which was 17.76% higher than Polyester/Elium® composites. Fractography of toughened Elium®IM composites displayed significant resistance to crack propagation that generated a rough and shear deformed curved layer type of de-bonding surface due to the extra toughening provided by particles which generated the crack deflection and void resulting from cavitation of ABS particles.

Investigation of Curing Mechanism and Mechanical Properties of Polypropylene/Aliphatic Epoxy Composites

Temperature-sensitive cure kinetics based on bisphenol A oligomeric diglycidyl ether and branching diphenylmethane di-isocyanate, polymer aliphatic or lower molecular weight aromatic amines, and polypropylene and epoxy composites were examined. Polypropylene networks are formed initially, followed by amine hardeners interfering with epoxy oxirane rings to frame linear oligomers. Finally, the system is formed by a reaction between amines obtained in the second phase and epoxy oxirane rings during the curing step. This three-stage treatment was illustrated. The activation energy was calculated using the Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose isoconversational approaches to cure degree. The Ea-to-αcorrelation was determined using these approaches, revealing that the research curing systems exhibited autocatalytic effects. Among the materials studied, compounds with low molecular weight aromatic amines had the strongest and longest-lasting tensile characteristics. There are numerous advantages to slow curing and discrete stages of composite creation, including better mechanical properties.

Mold temperature- and molar mass-dependent structural formation in micro-injection molding of isotactic polypropylene

The structural formation and development of isotactic polypropylene (iPP) upon the micro-injection molding process was investigated at different mold temperatures and molecular weights utilizing a real-time synchrotron radiation small angle X-ray scattering (SAXS) technique combined with a customized micro-injection molding apparatus. Shish-kebab structure and parent-daughter lamellae were found to be formed during micro-injection molding for all iPP samples. In the case of kebab lamellae, a considerable growth in the long period and in the average thickness of lamellar crystallites and amorphous domains is observed at initial stages of crystallization for samples molded at varying temperatures. This effect is caused by the successive formation of thin lamellae in the outer layer and thick lamellae in the inner layer during the manufacturing process as evidenced by the spatial distribution of the crystalline lamellae across the thickness. In addition, the length of the shish formation increases remarkably at the onset of crystallization, the extent of which is dependent on the mold temperature. Despite the large changes of the lamellar stacks and the shish misorientation, the final length of the shish remains essentially unchanged when varying mold temperature. Since there is a critical orientation molecular weight above which the chains are stretched and oriented to form stable shish, the iPP sample with a low molar mass exhibits an overall decrease in the scattering intensity of SAXS patterns compared to the high molecular weight polypropylene. • The structural formation of iPP is investigated utilizing a customized micro-injection molding device. • Shish-kebab and parent-daughter lamellae are formed during micro-injection molding. • A considerable increase in the long period is observed at initial stages of crystallization. • The length of the shish formation increases remarkably at the onset of crystallization. • The final shish length remains essentially unchanged when varying mold temperature.

Thermally and organomodified montmorillonite as effective regulators of the structure formation process in polypropylene/polystyrene blends

The influence of the concentration of thermally and organomodified montmorillonite on the processes of structure formation in a blend of polypropylene/polystyrene (PP/PS) was studied. It is established that in nanofilled compositions, as well as in the original, is formed a microfibrillar structure, the dimensional characteristics of which depend on the content of the additive and the method of its modification. The investigated clays by content (0.2–2.0) wt. % by weight of polypropylene have a compatibilizing effect in the blend of PP/PS, which reduces the average diameter of microfibers by 1.6 times and increases the homogeneity of their distribution by diameter: statistical indicators decrease (standard deviation, variance, coefficient of variation). The modifying effect of thermally modified clay is higher—the improvement of the dimensional characteristics of PP microfibers is achieved at its minimum content in the blend (0.2 wt. %). The formation of anisotropic PP structures in the PS matrix and the relaxation of the accumulated stresses at the exit of the molding hole is the main factor that causes high values of the coefficient of swelling of the extrudates (4.0–7.7). The change in the microstructure of the extrudates of nanofilled systems during spinning depends on the composition of the blend and the method of modification of montmorillonite. The average diameters of microfibers decrease from 2.2 μm (in the original blend) to (1.3–2.0) μm (in three-component) depending on the content of additives. The ability to regulate the microstructure of incompatible polymer blends by introducing additives of thermally and organomodified montmorillonite will contribute to the creation of nanocomposites with controlled morphology, as well as new fine-fiber materials with improved filtering characteristics.

VP028 TAPP REPAIR FOR INCISIONAL LUMBAR HERNIA

Abstract Aim “Incisional hernias are very common and can present even after minimally invasive surgery for other pathologies. Laparoscopic ventral hernia repair first described by LeBlanc in 1992, gained great popularity, because of its known advantages over the open techniques. In the last decade because of increasing concerns about the future risks of using an intra-peritoneal mesh, several minimally invasive techniques using a mesh outside abdominal cavity have been described. We report the use of a TAPP technique.” Material and Methods “48 yo female patient, that underwent a laparoscopic right adrenalectomy, for myelolipoma, in 2015, with subsequent incisional lumbar hernia (L4W1) in the extraction incision.” Results “The patient was submitted to a laparoscopic TAPP repair in ambulatory surgery with extended recovery. The hernia defect was closed with a barbed suture and it was used a 15x15cm medium weight polypropylene mesh without traumatic fixation. For pain control it was done a TAP block guided by laparoscopy. The duration of surgery was 90 minutes. The patient had no complications. No recurrence on follow-up (4 months).” Conclusions “New minimally invasive procedures for the repair of incisional hernias avoid the intraperitoneal mesh position and maintain all the advantages of the minimally invasive approach. Some of these techniques may be complex and have a long learning curve. TAPP seems reproducible and a good option if a good extra-peritoneal dissection is possible. Larger series are needed, to accurately compare these new techniques with IPOM, open sublay and to select the best technique for each patient.”

Experimental Investigation on concrete containing E-waste as course aggregate

Electrical and Electronic waste (e-waste) is increasing rapidly in the world, and is passing severe toxic waste issues to the human beings and the environment. About 80% to 85% of various electronic items, wastes are decomposed in landfills which might include or discharge lethal gases into air, may have an effect on human beings and environment. For solving and minimizing the discarding of huge quantity E-waste substance, recycle of E-waste materials in concrete production is well thought-out as the mainly possible purpose. It helps to eliminate the concrete materials deficiency issues that are currently going on in construction industry and it also helps to develop the strength of concrete mix and decrease the rate of concrete. In the current study, a novel attempt has been made by adding optimum weight polypropylene fiber with partial replacement of 20 mm E-waste particles as course aggregate. E-waste with pp fiber is employed in concrete in order to improve the strength of concrete mix. The work was carried out on M35 grade concrete specimen (without use of E-waste particles and pp fibers) and with a partial substitution of course aggregates with E-waste particles in range of 0%, 10%, 20% and 30% with respect to the weight of aggregate and pp fibers in the range of 0%, 0.2%, 0.4% and 0.6% with respect to the weight of cement. Comp. strength, Tensile strength and flexural strength of fibrous concrete with E-waste materials and not including e-waste materials as course aggregates was experimented which presented an excellent strength gain.

Prospective Comparative Study of Laparoscopic Totally Extra-Peritoneal Repair for Inguinal Hernia with Light Weight Polypropylene Mesh V/S 3D Anatomically Shaped Large Pore Polypropylene Mesh

Prospective Comparative Study of Laparoscopic Totally Extra-Peritoneal Repair for Inguinal Hernia with Light Weight Polypropylene Mesh V/S 3D Anatomically Shaped Large Pore Polypropylene Mesh