Cost-effectiveness of low-astigmatism correction with toric or spherical intraocular lenses combined with corneal incisions: an economic evaluation.

PURPOSE: To assess the cost-effectiveness of the treatment of low corneal astigmatism (≤1.5 D) at the moment of the cataract surgery. SETTING: ("Masked by journal requirement"). DESIGN: Economic Evaluation. METHODS: A decision tree was used to assess the cost-effectiveness of implanting spherical versus toric intraocular lenses (IOLs) or the spherical lens combined with the following corneal incisions: limbal relaxing incisions conducted manually (M-LRI) or assisted by femtosecond laser (F-LRI), arcuate keratotomies conducted manually (M-AK) or assisted by femtosecond (F-AK), and intrastromal arcuate keratotomies (F-iAK). Outcomes of cost were selected from a patient's perspective considering the gross cost of each one of the surgeries at European centers, and the effectiveness variable was the probability of achieving a visual acuity of 20/20 after surgery. A sensitivity analysis was conducted to assess the uncertainty considering the evidence retrieved from the transition probabilities of the model, the effectiveness, and the cost. RESULTS: F-AK or Toric IOLs were the most effective treatments, increasing an 16% or 9%, respectively, in the percentage of eyes attaining 20/20 vision. The M-LRI, F-iAK, and F-LRI procedures were strongly dominated, while the M-AK and toric IOL were weakly dominated by the F-AK. A patient with low corneal astigmatism would need to be willing to pay 360€ [CI 95%: 231-1224] with F-AK and 472€ [CI 95%: 149-4490] with toric IOLs for a 10% increase in the probability of achieving 20/20 vision. CONCLUSIONS: From the patient's perspective, F-AK was generally the most cost-effective treatment, even though toric IOLs can dominate in some countries.

Sex-specific impact of inflammation on traditional cardiovascular risk factors and atherosclerosis in axial spondyloarthritis. A multicentre study of 913 patients.

INTRODUCTION: The nature of the relationship between inflammation, cardiovascular (CV) risk factors and atherosclerosis in axial spondyloarthritis (axSpA) remains largely unknown and sex differences in this regard are yet to be assessed. METHODS: Study including 611 men and 302 women from the Spanish multicentre AtheSpAin cohort to assess CV disease in axSpA. Data on CV disease risk factors were collected both at disease diagnosis and at enrolment, and data on disease activity, functional indices and carotid ultrasonography only at enrolment. RESULTS: After a median disease duration of 9 years, patients of both sexes who at disease diagnosis had elevated acute phase reactants (APRs), more frequently had hypertension and obesity. The same occurred with dyslipidaemia in men and with diabetes mellitus in women. At enrolment, CV risk factors were independently associated with APR and with activity and functional indices, with various sex differences. C reactive protein (CRP) values were inversely associated with HDL-cholesterol in men (ß coefficient: -1.2 (95% CI: -0.3 to -0.07) mg/dL, p=0.001), while erythrocyte sedimentation rate values were positively associated with triglycerides in women (ß coefficient: 0.6 (95% CI: 0.04 to 1) mg/dL, p=0.035). Furthermore, only women showed an independent relationship between insulin resistance parameters and APR or disease activity. Both men and women with high-very high CV risk according to the Systematic Assessment of Coronary Risk Evaluation 2 and CRP levels higher than 3 mg/L at diagnosis of the disease presented carotid plaques significantly more frequently than those with normal CRP levels at disease diagnosis. CONCLUSION: Inflammation is associated with atherosclerosis and CV disease in axSpA. A gender-driven effect is observed in this relationship.

Recovery of an Antioxidant Derived from a Phenolic Diphosphite from Wastewater during the Production of a Polypropylene Compound: A Step towards Sustainable Management.

Organic phosphoester (OPE) antioxidants are currently required due to their contribution to enhancing the quality of polymers, including polypropylene (PP). In this research, an integral methodology is presented for the efficient extraction of bis(2,4-dicumylphenyl) pentaerythritol diphosphite from industrial wastewater. Upon employing the solid-phase extraction (SPE) technique, the recovered compound is subjected to a comprehensive analysis of the recovered compound using high-performance liquid chromatography (HPLC), mass spectrometry (MS), thermal analysis (TGA), Fourier transforms infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Subsequently, purified Bis(2,4-dicumylphenyl) pentaerythritol diphosphite was evaluated as a thermo-oxidative stabilizer after incorporation into PP resins. The relative standard deviation (RSD), Error (Er), linearity (R2), and percentage (%) recovery were less than 2.6, 2.5, more significant than 0.9995, and greater than 96%, respectively, for the inter-day and intra-day tests of the chromatographic method and the SPE. Except for chloroform, which was necessary due to the solubility properties of the investigated analyte, the use of environmentally friendly solvents, such as methanol and acetonitrile, was considered during the development of this research. The OPE extracted from industrial wastewater was characterized by FTIR, UV-Vis, DSC, TGA, and MS, allowing the elucidation of the structure of Bis(2,4-dicumylphenyl) pentaerythritol diphosphite (BDPD). The recovered OPE was mixed with PP resins, allowing it to improve its thermal properties and minimize its thermo-oxidative degradation. Organophosphorus flame retardant (OPE)' concentration in wastewater is alarming, ranging from 1179.0 to 4709.6 mg L-1. These exceed toxicity thresholds for aquatic organisms, emphasizing global environmental risks. Using a validated solid-phase extraction (SPE) technique with over 94% recovery, the study addresses concerns by removing organic contaminants and supporting circular economy principles. The high economic and environmental significance of recovering BDPD underscores the need for urgent global attention and intervention.

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).

Cardiovascular event in a cohort of rheumatoid arthritis patients in Castilla-La Mancha: Utility of carotid ultrasound.

Rheumatoid Arthritis (RA) has a mortality rate 1,3 to 3 times higher than the general population, with cardiovascular mortality accounting for 40-50% of cases. Currently, cardiovascular disease is considered an extraarticular manifestation of RA (OR: 1,5-4,0). Ultrasound measurement of the intima-media thickness (IMT) of the common carotid artery and the presence of atherosclerotic plaques (AP) is a non-invasive method and a surrogate marker of subclinical arteriosclerosis. OBJECTIVE: To determine if subclinical arteriosclerosis findings through carotid ultrasound can serve as a good predictor of cardiovascular events (CVE) development in a cohort of RA patients over a 10-year period. METHODOLOGY: A cohort of RA patients seen in the Rheumatology outpatient clinic of a hospital in Castilla La Mancha in 2013 was evaluated. A prospective evaluation for the development of CVE over the following 10 years was conducted, and its correlation with previous ultrasound findings of IMT and AP was analyzed. RESULTS: Eight (24%) patients experienced a CVE. Three (9%) had heart failure, three (9%) had a stroke, and two (6%) experienced acute myocardial infarction. RA patients who developed a CVE had a higher IMT (0,97 +/- 0.08 mm) compared to the RA patients without CV complications (0,74 +/- 0.15 mm) (p = 0,003). The presence of IMT ≥ 0.9 mm and AP had a relative risk of 12,25 (p = 0,012) and 18,66 (p = 0,003), respectively, for the development of a CVE. CONCLUSIONS: Carotid ultrasound in RA patients may allow for early detection of subclinical atherosclerosis before the development of CVE, with IMT ≥ 0.9 mm being the most closely associated finding with CVE, unaffected by age.

Study of the Chemical Activities of Carbon Monoxide, Carbon Dioxide, and Oxygen Traces as Critical Inhibitors of Polypropylene Synthesis.

This study outlines the investigation into how the compounds CO2, CO, and O2 interact with the active center of titanium (Ti) on the surface of MgCl2 and how these interactions impact the productivity of the Ziegler-Natta catalyst, ultimately influencing the thermal stability of the produced polypropylene. The calculations revealed that the adsorption energies of Ti-CO2-CO and O2 were -9.6, -12.5, and -2.32 Kcal/mol, respectively. Using the density functional theory in quantum calculations, the impacts of electronic properties and molecular structure on the adsorption of CO, O2, and CO2 on the Ziegler-Natta catalyst were thoroughly explored. Additionally, the Gibbs free energy and enthalpy of adsorption were examined. It was discovered that strong adsorption and a significant energy release (-16.2 kcal/mol) during CO adsorption could explain why this gas caused the most substantial reductions in the ZN catalyst productivity. These findings are supported by experimental tests showing that carbon monoxide has the most significant impact on the ZN catalyst productivity, followed by carbon dioxide, while oxygen exerts a less pronounced inhibitory effect.

Evento cardiovascular en una cohorte de pacientes con artritis reumatoide en Castilla-La Mancha, utilidad de la ecografía carotídea / Cardiovascular event in a cohort of rheumatoid arthritis patients in Castilla-La Mancha: Utility of carotid ultrasound

La artritis reumatoide (AR) presenta una mortalidad de 1,3-3 veces superior a la población general donde destaca la mortalidad de origen cardiovascular con un 40-50%. Actualmente se considera la enfermedad cardiovascular como una manifestación extraarticular de la AR, siendo un factor de riesgo independiente de los tradicionales, con un riesgo elevado de enfermedad cardiovascular (OR: 1,5-4,0). La medición ecográfica del grosor íntimo medial (GIM) de la arteria carótida común y la presencia de placas ateromatosas es un método no invasivo y marcador subrogado de arterioesclerosis subclínica. Objetivo: Establecer si los hallazgos de arterioesclerosis subclínica por ecografía carotídea pueden ser un buen predictor del desarrollo de eventos cardiovasculares (ECV) en una cohorte de pacientes con AR a 10 años. Metodología: Se evaluó una cohorte de pacientes con AR atendidos en consulta externa de Reumatología de una hospital de Castilla-La Mancha durante el año 2013. Se realizó una evaluación para el desarrollo de ECV a los 10 años siguientes de comenzado el estudio y se analizó su correlación con los hallazgos ecográficos previos de GIM y placas ateromatosas. Resultados: Ocho (24%) pacientes presentaron un ECV. Tres (9%), episodio de fallo cardiaco; 3 (9%) accidente cerebrovascular y 2 (6%) episodio de infarto agudo al miocardio. Los pacientes con AR que desarrollaron un ECV habían presentado un GIM mayor (0,97±0,08mm) en comparación con los pacientes con AR que no tuvieron complicaciones cardiovasculares (0,74±0,15mm) (p=0,003). La presencia de un GIM≥0,9mm y placas ateromatosas representó un riesgo relativo de 12,25 (p=0,012) y 18,66 (p=0,003), respectivamente, para el desarrollo de un ECV. Conclusiones: La ecografía carotídea en pacientes con AR nos podría permitir la detección precoz de aterosclerosis subclínica antes del desarrollo de ECV, siendo fundamentalmente el GIM≥0,9mm el hallazgo más asociado a ECV y no influenciado por la edad.(AU)

Rheumatoid arthritis (RA) has a mortality rate 1.3–3 times higher than the general population, with cardiovascular mortality accounting for 40%–50% of cases. Currently, cardiovascular disease is considered an extra-articular manifestation of RA (OR: 1.5–4.0). Ultrasound measurement of the intima-media thickness (IMT) of the common carotid artery and the presence of atherosclerotic plaques is a non-invasive method and a surrogate marker of subclinical arteriosclerosis. Objective: To determine if subclinical arteriosclerosis findings through carotid ultrasound can serve as a good predictor of cardiovascular events (CVE) development in a cohort of RA patients over a 10-year period. Methodology: A cohort of RA patients seen in the rheumatology outpatient clinic of a hospital in Castilla-La Mancha in 2013 was evaluated. A prospective evaluation for the development of CVE over the following 10 years was conducted, and its correlation with previous ultrasound findings of IMT and atherosclerotic plaques was analyzed. Results: Eight (24%) patients experienced a CVE. Three (9%) had heart failure, three (9%) had a stroke, and two (6%) experienced acute myocardial infarction. RA patients who developed a CVE had a higher IMT (0.97±0.08mm) compared to the RA patients without cardiovascular complications (0.74±0.15mm) (P=.003). The presence of IMT≥0.9mm and atherosclerotic plaques had a relative risk of 12.25 (P=.012) and 18.66 (P=.003), respectively, for the development of a CVE. Conclusions: Carotid ultrasound in RA patients may allow for early detection of subclinical atherosclerosis before the development of CVE, with IMT≥0.9mm being the most closely associated finding with CVE, unaffected by age.(AU)

Functional Classification of Intraocular Lenses Based on Defocus Curves: A Scoping Review and Cluster Analysis.

PURPOSE: To explore a potential functional classification of intraocular lenses (IOLs) based on monocular visual acuity defocus curves (VADCs) as a primary end-point. METHODS: A systematic literature search was conducted using PubMed. Two independent reviewers screened the literature for inclusion and data extraction. Inclusion criteria were full-text primary clinical studies of IOLs, published in English from 2010 onward, involving patients undergoing cataract or refractive lens exchange. A cluster analysis was conducted to explore similarities in the range of field (RoF) and increase of visual acuity from intermediate to near (ΔVA). RESULTS: A total of 107 studies were ultimately included from the 436 identified in the systematic search, with an additional 5 studies added through the snowballing technique search. The cluster analysis was conducted using 69 reports that included monocular VADCs. Two main categories were identified based on the achieved RoF for 0.2 and 0.3 logMAR: full (FRoF) and partial (PRoF) RoF IOLs. Three subcategories were identified for FRoF depending on ΔVA: continuous (FRoF-C), smooth (FRoF-Sm), and steep (FRoF-St). On the other hand, PRoF IOLs shared the characteristic of monotonous decrease in visual acuity and were subclassified into two subcategories depending on the achieved RoF: narrowed (PRoF-N) and extended (PRoF-Ex). An additional subcategory was added to PRoF, enhanced (PRoF-En), for 7 reports alternating between PRoF-N and PRoF-Ex depending on the use of 0.2 or 0.3 logMAR as a cut-off for calculating the RoF. CONCLUSIONS: IOLs can be functionally classified into six types depending on the RoF and shape of the monocular VADC. [J Refract Surg. 2024;40(2):e108-e116.].

Development of films based on chitosan, gelatin and collagen extracted from bocachico scales (Prochilodus magdalenae).

Biodegradable biopolymers from species of the animal kingdom or their byproducts are sustainable as ecological materials due to their abundant supply and compatibility with the environment. The research aims to obtain a biodegradable active material from chitosan, gelatin, and collagen from bocachico scales (Prochilodus magdalenae). Regarding the methodology, films were developed from gelatin, chitosan, and collagen from bocachico scales (Prochilodus magdalenae) at different concentrations using glycerol as a plasticizer and citric acid as a cross-linker. The films were obtained with the hydrated mass processed by compression molding and characterized according to humidity, water solubility, contact angle, mechanical properties, and structural properties. The results of the films showed a hydrophobic characteristic. First, the chitosan-collagen (CS/CO) films showed a yellowish color, while the gelatin-collagen (Gel/CO) films were transparent and less soluble than the gelatin-collagen (Gel/CO) films. Concerning mechanical properties, gelatin films showed higher stiffness and tensile strength than chitosan films. Furthermore, in the morphological analysis, more homogeneous chitosan films were obtained by increasing the concentration of citric acid. In general, chitosan, gelatin, and collagen extracted from the scales of the bocachico (Prochilodus magdalenae) are an alternative in the application of films in the food industry.

Analysis of substrate specificity of cytochrome P450 monooxygenases involved in trichothecene toxin biosynthesis.

Trichothecenes are a structurally diverse family of toxic secondary metabolites produced by certain species of multiple fungal genera. All trichothecene analogs share a core 12,13-epoxytrichothec-9-ene (EPT) structure but differ in presence, absence and types of substituents attached to various positions of EPT. Formation of some of the structural diversity begins early in the biosynthetic pathway such that some producing species have few trichothecene biosynthetic intermediates in common. Cytochrome P450 monooxygenases (P450s) play critical roles in formation of trichothecene structural diversity. Within some species, relaxed substrate specificities of P450s allow individual orthologs of the enzymes to modify multiple trichothecene biosynthetic intermediates. It is not clear, however, whether the relaxed specificity extends to biosynthetic intermediates that are not produced by the species in which the orthologs originate. To address this knowledge gap, we used a mutant complementation-heterologous expression analysis to assess whether orthologs of three trichothecene biosynthetic P450s (TRI11, TRI13 and TRI22) from Fusarium sporotrichioides, Trichoderma arundinaceum, and Paramyrothecium roridum can modify trichothecene biosynthetic intermediates that they do not encounter in the organism in which they originated. The results indicate that TRI13 and TRI22 could not modify the intermediates that they do not normally encounter, whereas TRI11 could modify an intermediate that it does not normally encounter. These findings indicate that substrate promiscuity varies among trichothecene biosynthetic P450s. One structural feature that likely impacts the ability of the P450s to use biosynthetic intermediates as substrates is the presence and absence of an oxygen atom attached to carbon atom 3 of EPT.

Screening of positive dysphotopsia before multifocal intraocular lens implantation.

PURPOSE: To assess the photic phenomena (PP) and positive dysphotopsia in candidates for presbyopia or cataract surgery and to evaluate their relationship with cataract grading systems. DESIGN: Retrospective observational. METHODS: Monocular data for 82 subjects measured during the preoperative screening were retrospectively retrieved from our database. The evaluated variables consisted of two methods for PP measurement: light distortion index (LDI) and parameters obtained from a simulator, both of which were combined with subjective bother related to PP. The cutoff for LDI that better predicted patients passing from slightly to moderately bothersome was estimated. The relationships between LDI and the following objective cataract grading methods were also assessed: objective scatter index (OSI), dysfunctional lens index (DLI), and Pentacam Nucleus Staging (PNS). RESULTS: LDI was the best method for measuring PP, which showed a significant correlation with the bothersome question (rho = 0.34, P = 0.002) and also with OSI (rho = 0.67, P < 0.0005), DLI (rho = -0.29, P = 0.007), and PNS (rho = 0.48, P < 0.0005). The number/percentage of patients who found it bothersome was as follows: "Not at all" (18/22%), "Slightly" (41/50%), "Moderately" (15/18.3%), and "Very" (8/9.7%). The cutoff value that predicted the transition from slightly to moderately bothersome was ≥15.20% according to LDI, which could be estimated with the following values for grading: ≥2.8 for OSI, ≤7.6 for DLI, and ≥2 for PNS. CONCLUSIONS: Patients reporting moderately or higher bothersome levels in the preoperative period and with LDI <15.20%, <2.8 for OSI, >7.6 for DLI, and <2 for PNS might deserve special attention in the multifocal intraocular lens selection.

Simulations of Multifocal Vision in Patients With Previous Monofocal Intraocular Lens Implantation.

PURPOSE: To evaluate the effectiveness and patient acceptance of multifocal vision simulation in patients with previous monofocal intraocular lens (IOL) implantation, and to explore their willingness-to-pay (WTP) and willingness-to-accept (WTA) based on the perceived advantages and disadvantages of multifocal vision. METHODS: Seventeen patients with previous monofocal IOL implantation participated in this cross-sectional study. The SimVis Gekko device (2EyesVision SL) was used to simulate monofocal (Evaluation B) and multifocal (Evaluation C) visual experiences, compared to their existing vision (Evaluation A). Visual acuity at three distances and defocus curves were measured. Patients responded to inquiries about visual quality in each evaluation, bothersomeness of photic phenomena, probability to select the visual experience, and the monetary value they associated with enhanced WTP or diminished WTA visual quality. RESULTS: The simulations underestimated the visual acuity reported for the IOL in existing literature by one or two lines, depending on the testing distance. This underestimation was more pronounced in defocus curves. However, 70.6% of patients were likely or very likely to opt for multifocal vision, indicating they perceived the benefits of multifocality. The WTP for multifocal vision was twice that of monofocal vision, and the WTP/WTA ratio exceeded 1, suggesting the perceived vision benefits outweighed potential drawbacks. CONCLUSIONS: Despite underestimating the expected postoperative visual performance, the multifocal simulation enabled patients to perceive the benefits of multifocal vision to some extent. This system could be beneficial in avoiding potential postoperative complaints, but the possible rise in false-positive results should be considered and evaluated in future research. [J Refract Surg. 2023;39(12):831-839.].

Descemet membrane endothelial keratoplasty combined with presbyopia-correcting and toric intraocular lenses - a narrative review.

Fuchs endothelial corneal dystrophy (FECD) is the leading indication for EK and may coexist with cataract and presbyopia. Notably, the outcomes of phacoemulsification in FECD patients are not as favorable as those in eyes without this condition. Historically, only monofocal intraocular lenses (IOLs) were recommended for these patients. However, recent reports have described the implantation of Premium-IOLs (such as Multifocal IOLs, Enhanced Depth of Focus IOLs, and Toric IOLs) in FECD eyes undergoing cataract surgery and Descemet membrane endothelial keratoplasty (DMEK). While the results are encouraging, they are not as optimal as those from unoperated eyes, especially when comparing simultaneous procedures to sequential ones. It's advised to perform the DMEK first to improve the accuracy of IOL calculations. Still, even successfully operated eyes may experience secondary graft failure or graft rejection after DMEK. The success rate of a secondary DMEK is typically lower than that of the initial procedure. Furthermore, if the postoperative thickness after DMEK is less than anticipated, laser enhancements might not be an option. There's a pressing need for more controlled and randomized clinical trials to ascertain the safety and effectiveness of Premium-IOLs for FECD eyes. This narrative review aims to collate evidence on the use of Premium IOL technologies in eyes receiving EK and to underscore key points for surgeons performing EK combined with cataract surgery.

Evaluation of the Reactivity of Methanol and Hydrogen Sulfide Residues with the Ziegler-Natta Catalyst during Polypropylene Synthesis and Its Effects on Polymer Properties.

The study focused on the evaluation of the influence of inhibitory compounds such as hydrogen sulfide (H2S) and methanol (CH3OH) on the catalytic productivity and properties of the polymers in the polymerization process with the Ziegler-Natta catalyst. The investigation involved experimental measurements, computational calculations using DFT, and analysis of various parameters, such as molecular weight, melt flow index, xylene solubility, and reactivity descriptors. The results revealed a clear correlation between the concentration of H2S and methanol and the parameters evaluated. Increasing the H2S concentrations, on average by 0.5 and 1.0 ppm, resulted in a drastic decrease in the polymer's molecular weight. A directly proportional relationship was observed between the flow rate and the H2S concentration. In the case of methanol, the change occurred from 60 ppm, causing a sharp decrease in the molecular weight of the polymer, which translates into an increase in the fluidity index and a decrease in solubility in xylene. The presence of these inhibitors also affected the catalytic activity, causing a reduction in the productivity of the Ziegler-Natta catalyst. Computational calculations provided a deeper understanding of the molecular behavior and reactivity of the studied compounds. The computational calculations yielded significantly lower results compared to other studies, with values of -69.0 and -43.9 kcal/mol for the Ti-CH3OH and H2S interactions, respectively. These results indicate remarkable stability in the studied interactions and suggest that both adsorptions are highly favorable.

Parts per Million of Propanol and Arsine as Responsible for the Poisoning of the Propylene Polymerization Reaction.

Polypropylene synthesis is a critical process in the plastics industry, where control of catalytic activity is essential to ensure the quality and performance of the final product. In this study, the effect of two inhibitors, propanol and arsine, on the properties of synthesized polypropylene was investigated. Experiments were conducted using a conventional catalyst to polymerize propylene, and different concentrations of propanol and arsine were incorporated into the process. The results revealed that the addition of propanol led to a significant decrease in the Melt Flow Index (MFI) of the resulting polypropylene. The reduction in the MFI was most notable at a concentration of 62.33 ppm propanol, suggesting that propanol acts as an effective inhibitor by slowing down the polymerization rate and thus reducing the fluidity of the molten polypropylene. On the other hand, introducing arsine as an inhibitor increased the MFI of polypropylene. The maximum increase in the MFI was observed at a concentration of 0.035 ppm arsine. This suggests that small amounts of arsine affect the MFI and Mw of the produced PP. Regarding the catalyst productivity, it was found that as the concentration of propanol in the sample increased (approximately seven ppm), there was a decrease in productivity from 45 TM/kg to 44 TM/kg. Starting from 10 ppm, productivity continued to decline, reaching its lowest point at 52 ppm, with only 35 MT/kg. In the case of arsine, changes in catalyst productivity were observed at lower concentrations than with propanol. Starting from about 0.006 ppm, productivity decreased, reaching 39 MT/kg at a concentration of 0.024 ppm and further decreasing to 36 TM/kg with 0.0036 ppm. Computational analysis supported the experimental findings, indicating that arsine adsorbs more stably to the catalyst with an energy of -60.8 Kcal/mol, compared to propanol (-46.17 Kcal/mol) and isobutyl (-33.13 Kcal/mol). Analyses of HOMO and LUMO orbitals, as well as reactivity descriptors, such as electronegativity, chemical potential, and nucleophilicity, shed light on the potential interactions and chemical reactions involving inhibitors. Generated maps of molecular electrostatic potential (MEP) illustrated the charge distribution within the studied molecules, further contributing to the understanding of their reactivity. The computational results supported the experimental findings and provided additional information on the molecular interactions between the inhibitors and the catalyst, shedding light on the possible modes of inhibition. Solubles in xylene values indicate that both propanol and arsine affect the polymer's morphology, which may have significant implications for its properties and final applications.

Experimental-Density Functional Theory (DFT) Study of the Inhibitory Effect of Furan Residues in the Ziegler-Natta Catalyst during Polypropylene Synthesis.

In this experimental-theoretical study, the effect of furan on Ziegler-Natta catalyst productivity, melt flow index (MFI), and mechanical properties of polypropylene were investigated. Through the analysis of the global and local reactivity of the reagents, it was determined that the furan acts as an electron donor. In contrast, the titanium of the ZN catalyst acts as an electron acceptor. It is postulated that this difference in reactivity could lead to forming a furan-titanium complex, which blocks the catalyst's active sites and reduces its efficiency for propylene polymerization. Theoretical results showed a high adsorption affinity of furan to the active site of the Ti catalyst, indicating that furan tends to bind strongly to the catalyst, thus blocking the active sites and decreasing the availability for propylene polymerization. The experimental data revealed that the presence of furan significantly reduced the productivity of the ZN catalyst by 10, 20, and 41% for concentrations of 6, 12.23, and 25.03 ppm furan, respectively. In addition, a proportional relationship was observed between the furan concentration and the MFI melt index of the polymer, where the higher the furan concentration, the higher the MFI. Likewise, the presence of furan negatively affected the mechanical properties of polypropylene, especially the impact Izod value, with percentage decreases of 9, 18, and 22% for concentrations of 6, 12.23, and 25.03 ppm furan, respectively.

Dimethylformamide Impurities as Propylene Polymerization Inhibitor.

This research study examined how the use of dimethylformamide (DMF) as an inhibitor affects the propylene polymerization process when using a Ziegler-Natta catalyst. Several experiments were carried out using TiCl4/MgCl2 as a catalyst, aluminum trialkyl as a cocatalyst, and different amounts of DMF. Then, we analyzed how DMF influences other aspects of the process, such as catalyst activity, molecular weight, and the number of branches in the polymer chains obtained, using experimental and computational methods. The results revealed that as the DMF/Ti ratio increases, the catalyst activity decreases. From a concentration of 5.11 ppm of DMF, a decrease in catalyst activity was observed, ranging from 45 TM/Kg to 44 TM/Kg. When the DMF concentration was increased to 40.23 ppm, the catalyst activity decreased to 43 TM/Kg, and with 75.32 ppm, it dropped even further to 39 TM/Kg. The highest concentration of DMF evaluated, 89.92 ppm, resulted in a catalyst productivity of 36.5 TM/Kg and lost productivity of 22%. In addition, significant changes in the polymer's melt flow index (MFI) were noted as the DMF concentration increased. When 89.92 ppm of DMF was added, the MFI loss was 75%, indicating a higher flowability of the polymer. In this study, it was found that dimethylformamide (DMF) exhibits a strong affinity for the titanium center of a Ziegler-Natta (ZN) catalyst, with an adsorption energy (Ead) of approximately -46.157 kcal/mol, indicating a robust interaction. This affinity is significantly higher compared to propylene, which has an Ead of approximately -5.2 kcal/mol. The study also revealed that the energy gap between the highest occupied molecular orbital (HOMO) of DMF and the lowest unoccupied molecular orbital (SOMO) of the Ziegler-Natta (ZN) catalyst is energetically favorable, with a value of approximately 0.311 eV.