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Polymers (Basel) ; 16(11)2024 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-38891536

RESUMO

Organic solar cells (OSCs) are one of the most promising photovoltaic technologies due to their affordability and adaptability. However, upscaling is a critical issue that hinders the commercialization of OSCs. A significant challenge is the lack of cost-effective and facile techniques to modulate the morphology of the active layers. The slow solvent evaporation leads to an unfavorable phase separation, thus resulting in a low power conversion efficiency (PCE) of organic solar modules. Here, a nitrogen-blowing assisted method is developed to fabricate a large-area organic solar module (active area = 12 cm2) utilizing high-boiling-point solvents, achieving a PCE of 15.6%. The device fabricated with a high-boiling-point solvent produces a more uniform and smoother large-area film, and the assistance of nitrogen-blowing accelerates solvent evaporation, resulting in an optimized morphology with proper phase separation and finer aggregates. Moreover, the device fabricated by the nitrogen-blowing assisted method exhibits improved exciton dissociation, balanced carrier mobility, and reduced charge recombination. This work proposes a universal and cost-effective technique for the fabrication of high-efficiency organic solar modules.

3.
ISA Trans ; 151: 221-231, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-38839548

RESUMO

Top-blowing furnace systems, characterized by a large number of sensors and harsh working environments, are prone to sensor failures due to factors like component aging and external interference. These failures can significantly impact the system's safe and reliable operation. However, traditional sensor fault diagnosis methods often neglect the exploration of spatial-temporal characteristics and focus solely on learning temporal relationships between sensors, failing to effectively consider their spatial relationships. In this study, we propose a spatial correlation model based on the maximal information-based graph convolutional network (MI-GCN) by constructing a sensor network knowledge graph using maximal mutual information. The MI-GCN leverages the graph convolution mechanism to extract multi-scale spatial features and capture the spatial relationships between sensors. Additionally, we develop a spatial-temporal graph-level prediction model, known as the spatial-temporal graph transformer (STGT), to extract temporal features. By combining the spatial features extracted by the MI-GCN with the temporal features captured by the STGT, accurate predictions can be achieved. Sensor fault diagnosis is conducted by analysing the normalized residuals between the predicted values and the ground truth. Finally, the feasibility and effectiveness of the proposed method are validated using test data from a top-blowing furnace system in the nickel smelting process.

4.
Polymers (Basel) ; 16(9)2024 Apr 23.
Artigo em Inglês | MEDLINE | ID: mdl-38732650

RESUMO

Silicone elastomers are high-performance plastics. In the extrusion process, only high-consistency silicone rubbers were used. In order to reduce the cost and weight, silicone rubbers can be foamed during processing. In this study, high-consistency silicone rubber is processed with different physical and chemical blowing agents. The resulting reaction kinetics, as well as the mechanical and morphological properties, had been investigated and compared with each other. This showed that the chemical blowing agent significantly influenced the crosslinking reaction compared to the microspheres and the water/silica mixture tested, but it also achieved the lowest density compared to the physical blowing agents. When evaluating the foam morphology, it became clear that the largest number of pores was achieved with the microspheres and the largest pores when using the water/silica mixture. Furthermore, it has been shown that the different mechanisms of action of the blowing agents have a major influence on the mechanical properties, such as the micro shore hardness and the foam morphology.

5.
Polymers (Basel) ; 16(9)2024 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-38732755

RESUMO

The last few decades have witnessed significant advances in the development of polymeric-based foam materials. These materials find several practical applications in our daily lives due to their characteristic properties such as low density, thermal insulation, and porosity, which are important in packaging, in building construction, and in biomedical applications, respectively. The first foams with practical applications used polymeric materials of petrochemical origin. However, due to growing environmental concerns, considerable efforts have been made to replace some of these materials with biodegradable polymers. Foam processing has evolved greatly in recent years due to improvements in existing techniques, such as the use of supercritical fluids in extrusion foaming and foam injection moulding, as well as the advent or adaptation of existing techniques to produce foams, as in the case of the combination between additive manufacturing and foam technology. The use of supercritical CO2 is especially advantageous in the production of porous structures for biomedical applications, as CO2 is chemically inert and non-toxic; in addition, it allows for an easy tailoring of the pore structure through processing conditions. Biodegradable polymeric materials, despite their enormous advantages over petroleum-based materials, present some difficulties regarding their potential use in foaming, such as poor melt strength, slow crystallization rate, poor processability, low service temperature, low toughness, and high brittleness, which limits their field of application. Several strategies were developed to improve the melt strength, including the change in monomer composition and the use of chemical modifiers and chain extenders to extend the chain length or create a branched molecular structure, to increase the molecular weight and the viscosity of the polymer. The use of additives or fillers is also commonly used, as fillers can improve crystallization kinetics by acting as crystal-nucleating agents. Alternatively, biodegradable polymers can be blended with other biodegradable polymers to combine certain properties and to counteract certain limitations. This work therefore aims to provide the latest advances regarding the foaming of biodegradable polymers. It covers the main foaming techniques and their advances and reviews the uses of biodegradable polymers in foaming, focusing on the chemical changes of polymers that improve their foaming ability. Finally, the challenges as well as the main opportunities presented reinforce the market potential of the biodegradable polymer foam materials.

6.
Materials (Basel) ; 17(9)2024 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-38730829

RESUMO

This article presents the results of an investigation of the proposed method and the influence of a modified additive on foam concrete properties. X-ray diffraction analysis showed that the modified additive has a variable mineralogical composition, and the joint use of the components contributes to the synergistic effect, improving the processes of cement hydration. Microscopy of the foam concrete samples showed the presence of microcracks and micropores in samples both with and without the additive. However, the use of the additive significantly reduced their number and size, which indicates an improvement in the structure of the material. The strength values showed that the samples with the additive have high strength. In particular, the strength values of samples of type 3 at different stages of curing exceed those of samples of type 1 by 1.32-1.51 times and samples of type 2 by 1.07-1.10 times. The obtained strength values are 2.82-3.21 MPa for type 1, 3.64-4.04 MPa for type 2, and 4.39-4.84 MPa for type 3, which corresponds to grade D600. The evaluation of water absorption also confirmed the advantages of the proposed method and the additive, significantly reducing the water absorption of the samples and increasing their hydrophobicity. The obtained values of water absorption are 13.8-16.6% for type 1, 13.7-16.1% for type 2, and 9.5-11.2% for type 3.

7.
Micromachines (Basel) ; 15(4)2024 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-38675326

RESUMO

The use of static solution-assisted laser drilling can effectively improve hole roundness, decrease taper angle, and reduce recast layer thickness and hole wall slag adhesion. However, the enormous energy of the laser will evaporate the solution to form a suspension droplet and reduce the quality and efficiency of laser drilling. To deal with this defect, the mist-blowing method was used to reduce the influence of droplets on the taper angle and recast layer. In this work, the effect of wind speed on drilling quality was examined, and laser drilling in air, water, and NaCl solution was carried out to analyse the effect of solution composition on hole wall morphology. The results showed that a speed fan with a proper wind speed that disperses the droplets formed in the processing area can significantly reduce the refraction and scattering of the laser, and the taper angle and roundness of the drilling hole were also reduced by 15.6% and improved by 2.4%, respectively, under the wind speed of 2 m/s. The hole wall morphology showed a thicker recast layer and cracking in air, while it was thinner in water and there was little or no layer in the NaCl solution in the same current. When drilling in NaCl, the taper angle and roundness of the drilling hole were reduced by 4.13% and improved by 2.11%, respectively, compared to water. Due to the mechanical effect of the laser in the NaCl solution, the impact force on the material was much greater than that in water. The solution cavitation effect, generated by the absorption of laser energy, caused an explosive impact on the molten material adhered to the surface of the hole wall. Above all, drilling in the NaCl solution with a current of 200 A and a wind speed of 2 m/s was the optimal condition for obtaining the best processing quality.

8.
Carbohydr Polym ; 336: 122119, 2024 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-38670751

RESUMO

This study aimed to investigate the effects of polydimethylsiloxane (PDMS) with a low surface energy on the structure and physicochemical properties of starch/poly (butylene adipate-co-terephthalate) (PBAT) blown films. The film's appearance was not significantly changed after the addition of PDMS. Compared with the films without PDMS, the films with PDMS displayed a smoother surface. A 2% w/w PDMS addition resulted in the maximum mechanical properties (8.10 MPa of strength, 211.00% of modulus) and surface hydrophobicity (87°) of the films. By contrast, the film with 3% w/w PDMS showed the lowest light transmittance, water vapor (2.73 × 10-11 g·cm·cm2·s-1·Pa-1) and oxygen permeability (9.73 × 10-13·cm3·cm·cm-2·s-1·Pa-1), owing to the improved tightness of the matrix, which increased the zigzag path for molecules to pass through. Films with higher PDMS contents effectively extended the shelf life of packaged bananas and shiitake mushrooms, benefiting from the outstanding and appropriate barrier properties, according to principal component analysis results. Findings supported that high-content starch/PBAT films containing PDMS had potential in the preservation of fresh agricultural products.

9.
Dysphagia ; 2024 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-38492048

RESUMO

Patients with pseudobulbar palsy often present with velopharyngeal incompetence. Velopharyngeal incompetence is usually observed during expiratory activities such as speech and/or blowing during laryngoscopy. These patients typically exhibit good velopharyngeal closure during swallowing, which is dissociated from expiratory activities. We named this phenomenon "speech-swallow dissociation" (SSD). SSD on endoscopic findings can help in diagnosing the underlying disease causing dysphagia. This endoscopic finding is qualitative, and the quantitative characteristics of SSD are still unclear. Accordingly, the current study aimed to quantitatively evaluate SSD in patients with pseudobulbar palsy. We evaluated velopharyngeal pressure during swallowing and expiratory activity in 10 healthy subjects and 10 patients with pseudobulbar palsy using high-resolution manometry, and compared the results between the two groups. No significant differences in maximal velopharyngeal contraction pressure (V-Pmax) were observed during dry swallowing between the pseudobulbar palsy group and healthy subjects (190.5 mmHg vs. 173.6 mmHg; P = 0.583). V-Pmax during speech was significantly decreased in the pseudobulbar palsy group (85.4 mmHg vs. 34.5 mmHg; P < 0.001). The degree of dissociation of speech to swallowing in V-Pmax, when compared across groups, exhibited a larger difference in the pseudobulbar palsy group, at 52% versus 80% (P = 0.001). Velopharyngeal pressure during blowing was similar to that during speech. Velopharyngeal closure in patients with pseudobulbar palsy exhibited weaker pressure during speech and blowing compared with swallowing, quantitatively confirming the presence of SSD. Pseudobulbar palsy often presents with SSD, and this finding may be helpful in differentiating the etiology of dysphagia.

10.
Biosens Bioelectron ; 255: 116198, 2024 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-38555771

RESUMO

Accurate oxygen sensing and cost-effective fabrication are crucial for the adoption of wearable devices inside and outside the clinical setting. Here we introduce a simple strategy to create nonwoven polymeric fibrous mats for a notable contribution towards addressing this need. Although morphological manipulation of polymers for cell culture proliferation is commonplace, especially in the field of regenerative medicine, non-woven structures have not been used for oxygen sensing. We used an airbrush spraying, i.e. solution blowing, to obtain nonwoven fiber meshes embedded with a phosphorescent dye. The fibers serve as a polymer host for the phosphorescent dye and are shown to be non-cytotoxic. Different composite fibrous meshes were prepared and favorable mechanical and oxygen-sensing properties were demonstrated. A Young's modulus of 9.8 MPa was achieved and the maximum oxygen sensitivity improved by a factor of ∼2.9 compared to simple drop cast film. The fibers were also coated with silicone rubbers to produce mechanically robust sensing films. This reduced the sensing performance but improved flexibility and mechanical properties. Lastly, we are able to capture oxygen concentration maps via colorimetry using a smartphone camera, which should offer unique advantages in wider usage. Overall, the introduced composite fiber meshes show a potential to significantly improve cell cultures and healthcare monitoring via absolute oxygen sensing.


Assuntos
Técnicas Biossensoriais , Dispositivos Eletrônicos Vestíveis , Oxigênio , Polímeros/química , Próteses e Implantes
11.
Carbohydr Polym ; 333: 121982, 2024 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-38494234

RESUMO

The production of high-performance starch-based packaging films by extrusion blowing is challenging, ascribed to poor processability of the blend precursors. In this study, a new strategy of mechanical activation (MA)-enhanced metal-organic coordination was proposed to improve the processability of starch (St)/polyvinyl alcohol (PVA) blend precursor, with calcium acetate (CA) as a chelating agent and glycerol as a plasticizer. MA pretreatment activated the hydroxyl groups of starch and PVA for constructing strong metal-organic coordination between CA and St/PVA during reactive extrusion, which effectively enhanced the melt processing properties of the blend precursor, contributing to the fabrication of high-performance St/PVA films by the extrusion-blowing method. The as-prepared St/PVA films exhibited excellent mechanical properties (tensile strength of 34.5 MPa; elongation at break of 271.8 %), water vapor barrier performance (water vapor permeability of 0.704 × 10-12 g·cm-1·s-1·Pa-1), and oxygen barrier performance (oxygen transmission rate of 0.7 cm3/(m2·day·bar)), along with high transmittance and good uniformity. These outstanding characteristics and performances can be attributed to the improved interfacial interaction and compatibility between the two matrix phases. This study uncovers the mechanism of MA-enhanced metal-organic coordination for improving the properties of starch-based films, which provides a convenient and eco-friendly technology for the preparation of high-performance biodegradable films.

12.
Heliyon ; 10(3): e25259, 2024 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-38352739

RESUMO

This study aimed to investigate the modeling of antimicrobial activity (AA) of nisin and sorbate on Clostridium sporogenes in jar cream cheese (JCC) using the linear regression (LR), multilayer perceptron (MLP) neural network, and reduced error pruning tree (REPTree) methods, in order to prevent the late blowing defect (LBD) in the cheese. Both preservatives used in JCC samples showed AA against C. sporogenes; so that sorbate at all the concentrations used in JCC samples inhibited cracking spoilage during storage period at 35 °C. However, nisin could not inhibit cracking spoilage at concentration of 30 ppm in the samples, and a higher concentration of it was needed. The three models used in this study, followed the similar pattern in both training and validation datasets for nisin and sorbat in JCC. The R2 and root mean square error (RMSE) values of training and validation datasets showed the superiority of the REPTree model compared to the MLP and LR models (conventional methods) in the modeling of AA of nisin and sorbate against C. sporogenes in JCC.

13.
Polymers (Basel) ; 16(4)2024 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-38399847

RESUMO

The melt-blowing process involves high velocity airflow and fiber motion, which have a significant effect on fiber attenuation. In this paper, the three-dimensional airflow field for a melt-blowing slot die was measured using the hot-wire anemometry in an experiment. The fiber motion was captured online using a high-speed camera. The characteristics of the airflow distribution and fiber motion were analyzed. The results show that the melt-blowing airflow field is asymmetrically distributed. The centerline air velocity is higher than that around it and decays quickly. The maximum airflow velocity exists near the die face, in the range of 130-160 m/s. In the region of -0.3 cm < y < 0.3 cm and 0 < z < 2 cm, the airflow has a high velocity (>100 m/s). As the distance of z reaches 5 cm and 7 cm, the maximum airflow velocity reduces to 70 m/s. The amplitude of fibers is calculated, and it increases with the increase in air dispersion area which has a significant influence on fiber attenuation. At z = 1.5 cm, 2.5 cm, 4 cm, and 5.5 cm, the average fiber amplitudes are 1.05 mm, 1.71 mm, 2.83 mm, and 3.97 mm, respectively. In the vicinity of the die, the fibers move vertically downward as straight segments. With the increase in distance from the spinneret, the fiber appears to bend significantly and forms a fiber loop. The fiber loop morphology affects the velocity of the fiber movement, causing crossover, folding, and bonding of the moving fiber. The study investigated the interaction between the fiber and airflow fields. It indicates that the airflow velocity, velocity difference, and dispersion area can affect the motion of fiber which plays an important role in fiber attenuation during the melt-blowing process.

14.
Front Microbiol ; 15: 1353321, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38414773

RESUMO

The genus Clostridium is a large and diverse group of species that can cause food spoilage, including late blowing defect (LBD) in cheese. In this study, we investigated the taxonomic status of strain FAM25158 isolated from Emmental cheese with LBD using a polyphasic taxonomic and comparative genomic approach. A 16S rRNA gene sequence phylogeny suggested affiliation to the Clostridium sensu stricto cluster, with Clostridium tyrobutyricum DSM 2637T being the closest related type strain (99.16% sequence similarity). Average Nucleotide Identity (ANI) analysis revealed that strain FAM25158 is at the species threshold with C. tyrobutyricum, with ANI values ranging from 94.70 to 95.26%, while the digital DNA-DNA hybridization values were below the recommended threshold, suggesting that FAM25158 is significantly different from C. tyrobutyricum at the genomic level. Moreover, comparative genomic analysis between FAM25158 and its four closest C. tyrobutyricum relatives revealed a diversity of metabolic pathways, with FAM25158 differing from other C. tyrobutyricum strains by the presence of genes such as scrA, srcB, and scrK, responsible for sucrose utilization, and the absence of many important functional genes associated with cold and osmolality adaptation, which was further supported by phenotypic analyses. Surprisingly, strain FAM25158 exhibited unique physiologic traits, such as an optimal growth temperature of 30°C, in contrast to its closest relatives, C. tyrobutyricum species with an optimal growth temperature of 37°C. Additionally, the growth of FAM25158 was inhibited at NaCl concentrations higher than 0.5%, a remarkable observation considering its origin from cheese. While the results of this study provide novel information on the genetic content of strain FAM25158, the relationship between its genetic content and the observed phenotype remains a topic requiring further investigation.

15.
Int J Biol Macromol ; 263(Pt 2): 130437, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38412935

RESUMO

In this work, pullulan (PUL) nanofibrous films incorporated with water-in-oil emulsions (PE) were prepared by microfluidic blowing spinning (MBS). The microstructures of nanofibers were characterized by scanning electron microscopy (SEM), fourier transform infrared (FT-IR), and X-ray diffraction (XRD). With the addition of W/O emulsions, the thermal stability, mechanical, and water barrier properties of PUL nanofibers were improved. Increases in emulsion content significantly affected the antioxidant and antimicrobial properties of nanofibrous films. ABTS and DPPH free radical scavenging rates increased from 10.26 % and 8.57 % to 60.66 % and 57.54 %, respectively. The inhibition zone of PE nanofibers against E. coli and S. aureus increased from 11.00 to 20.00 and from 15.67 to 21.17 mm, respectively. In addition, we investigated the freshness effectiveness of PE nanofibrous films on fresh-cut apples. PE nanofibrous films significantly maintained the firmness, and reduced the weight loss and browning index of the fresh-cut apple, throughout the 4 days of storage. Thus, the PE nanofibrous films exhibited good potential to prolong the shelf life of fresh-cut fruit and promote the development of active food packaging.


Assuntos
Glucanos , Malus , Nanofibras , Nanofibras/química , Espectroscopia de Infravermelho com Transformada de Fourier , Emulsões , Escherichia coli , Staphylococcus aureus , Microfluídica , Embalagem de Alimentos , Tecnologia , Água
16.
Heliyon ; 10(2): e24150, 2024 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-38293368

RESUMO

The finite element simulations of the Soret-Dufour and angled magnetic field effects on conjugate heat and mass transportation of unsteady heat absorbing hydromagnetic Casson flow across a semi-infinite flat oscillatory plate engrafted in a porous medium with suction/blowing, radiation and chemical reaction is performed. The dimensionless coupled flow guiding nonlinear PDEs of the physical structure is handled numerically by the dynamic Galerkin finite element scheme. The demeanor of the velocity, concentration and the temperature profiles due to the alterations in the regulating flow parameters are examined graphically whereas the wall-friction, mass and heat transfer rates explicated by utilizing the tabular data. The research discovered that radiation; conjugate heat transfer and diffusion thermo effects heighten the temperature and velocity distributions whereas heat absorption has a reverse effect. Likewise, conjugate mass transfer and thermo-diffusion effects intensify the concentration and velocity distributions whereas the chemical reaction display overturns aspect. Increased radiation absorption, inclined magnetic field and porosity parameter stimulate fluid velocity whereas the Casson and magnetic parameters exhibit the converse impact. In the instance of suction, the profiles of concentration, velocity and temperature displayed a downturn nature but for the case of blowing, it was noticed a reversal trend. Further, a comparative analysis between the current findings and existing research works in the literature demonstrates our results are exact and accurate.

17.
Int J Biol Macromol ; 258(Pt 2): 128994, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38157632

RESUMO

Non-isocyanate polyurethane (NIPU) as a new type of polyurethane material has become a hot research topic in the polyurethane industry due to its no utilization of toxic isocyanates during the synthesis process. And the developing on recyclable biomass materials has also much attention in the industrial sector, hence the preparation and application of bio-based NIPU has also become a very meaningful study work. So, in this paper, tannin as a biomass material was used to synthesize tannin based non-isocyanate polyurethanes (TNIPU) resin, and then successfully prepared a self-blowing TNIPU foam at room temperature by using formic acid as initiator and glutaraldehyde as cross-linking agent. The compressive strength of this foam as high as 0.8 MPa, which is an excellent compressive performance. Meanwhile it will return to the state before compression when removing the pressure. This indicating that the foam has good toughness. In addition, formic acid can react with the amino groups in TNIPU to form amide substances, and generated enough heat to initiate the foaming process. Glutaraldehyde, as a crosslinking agent, reacts with the amino group in TNIPU to form a network structure system. By scanning electron microscope (SEM) observation of the cell shapes, it can be seen that the foam cells were uniform in size and shape, and the cell pores showed open and closed cells. The limiting oxygen index (LOI) tested value of this TNIPU foam is 24.45 % without any flame retardant added, but compared to the LOI value of polyurethane foam (17 %-19 %), TNIPU foam reveal a better fire resistance. It has a wider application prospect.


Assuntos
Formiatos , Isocianatos , Poliuretanos , Taninos , Glutaral
18.
Cureus ; 15(11): e48584, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-38084184

RESUMO

Orbital emphysema commonly resolves with no morbidity. However, sight-threatening complications, such as central retinal artery occlusion and ischemic optic neuropathy, may occur, which can result in poor visual outcomes. Plain skull X-ray, which is widely available, is a useful tool in identifying orbital emphysema. We report a case of a 29-year-old gentleman with underlying allergic rhinitis who presented with a painless, progressively increasing periorbital swelling of the right eye, which was aggravated by nose blowing. He had a history of blunt trauma one day prior to the presentation. Visual acuity was unaffected and optic nerve function tests were unremarkable. There was right upper lid swelling with crepitations, right hypoglobus with restricted upward gaze movement, and right conjunctival injection. Intraocular pressure was within normal limits. The posterior segment examination was unremarkable. A plain skull radiograph revealed a "black eyebrow sign" over the right orbit with no obvious orbital wall fracture. Computed tomography of the orbit showed focal indentation over the right lamina papyracea with superior orbito-palpebral emphysema. Systemic antibiotics, steroid nasal spray, and oral antihistamines were initiated with the prohibition of nose blowing. On post-trauma day five, he made an uneventful recovery. High clinical suspicion and thorough clinical examination with the aid of a plain skull radiograph can diagnose orbital emphysema in order for prompt referral to be undertaken to prevent morbidity. Clinicians should consider orbital emphysema as a differential diagnosis for periorbital swelling, especially if there was a preceding trauma.

19.
Polymers (Basel) ; 15(22)2023 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-38006148

RESUMO

Water, alcohols, diols, and glycerol are low-cost blowing agents that can be used to create the desired silicone foam structures. Although their combined use can be beneficial, it remains unclear how it affects the physical properties of the resulting materials. We conducted a comparative study of these hydroxyl-bearing blowing agents in fumed silica- and mica-filled polymer composite systems for simultaneous blowing and crosslinking to obtain a low-density, uniform porosity and superior mechanical properties. The foams were optimized for a uniform open-pore structure with densities ranging from 75 to 150 kg‧m-3. Varying the diol chain length (Cn) from one to seven carbons can alter the foam density and structure, thereby enhancing the foam tensile strength while maintaining a low density. Replacing 10 mol% of water with 1,4-butanediol decreased the density by 26%, while increasing the specific strength by 5%. By combining glycerol and water blowing, the resulting foams exhibited a 30% lower apparent density than their water-blown analogs. The results further showed that Cn > 4 alkane chain diols had an odd-even effect on the apparent density and cell wall thickness. All foamable compositions had viscosities of approximately 7000 cSt and curing times below 2 min, allowing for quick dispensing and sufficient time for the foam to cure in semi-industrial volumes.

20.
Polymers (Basel) ; 15(17)2023 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-37688170

RESUMO

Plastic-based additive manufacturing processes are becoming increasingly popular in the production of structural parts. Based on the idea of lightweight design and the aim of extending the functionality of additive structures, the production of additively manufactured foam structures has emerged as a new field of application. The optical characterisation of these structures is of particular importance for process adjustments and the identification of (unwanted) changes in the foam structure. The degree of foaming and the fineness of a foam structure are of interest at this point. In this context, only the part of a structure dominated by foam pores is considered a foam structure. So far, there are no sophisticated methods for such an optical characterisation. Therefore, in this work, microscope images of manufactured as well as artificially created additively manufactured foam structures were evaluated. On these images, the features porosity, pore size, pore amount and a measure for the textural change were determined in order to obtain information about changes within an additively manufactured foam structure. It is shown that additive structures show changing pore shapes depending on the orientation of the cutting plane, although there are no changes in the foaming behaviour. Therefore, caution is required when identifying changes within the foam structure. It was also found that, owing to the additive process, the total porosity is already set in the slicing process and remains constant even if the degree of foaming of individual tracks is changed. Therefore, the degree of foaming cannot be determined on the basis of the total porosity, but it can be assessed on the basis of the formation of large networks of process-related pores.

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