Polyurethane Microparticles Research Articles

Matrix Matters: novel insights for the extraction, preparation, and quantitation of microplastics in a freshwater mesocosm study

The extraction and characterization of secondary microplastics, those formed through subjection to the environment, must continuously improve in accuracy and applicability in order to generate robust microplastics exposure and risk assessments. Currently, there is a dearth of reliable extraction and quantitation methods for solid microplastic particles in sediment with chemical specificity. Herein we present advances in methodologies to extract and quantify microplastic particles from sediment, utilizing an outdoor mesocosm to model a freshwater coastal environment. Model secondary microplastics of crosslinked polyurethane (PU) were studied in comparison to model secondary polypropylene (PP) microplastics. Techniques to characterize particles in sediment included pyrolysis gas chromatography mass spectrometry (py GC/MS), stereoscope microscopy, and scanning electron microscopy. To complement particle analysis, plastic-associated leachable molecules were extracted from sediment and analyzed semi-quantitatively by high performance liquid chromatography with high-resolution mass spectrometry (HPLC/HR-MS). After developing and optimizing extraction and analytical methods we quantitated PU microparticles by count and weight and discovered that model PU particles fell from the water column into the sediment over the course of a year, while no PP particles were located in sediment samples. In addition, target small molecules associated with the crosslinked PU were identified in sediment by HPLC/HR-MS but leachable molecules associated with polypropylene could not be identified in sediment samples. We share the new py GC/MS method to quantify highly crosslinked PUs in complex environmental matrices containing both inorganic and organic components. In the process of generating robust extraction methods for microplastics in sediment, we discovered important considerations for the quantitation of microplastics by py GC/MS and the impacts of sample matrix on the quantitation of PU and PP specifically. We provide guidance for the preparation of microplastics from complex environmental matrices (e.g., sediment and soil) for analysis by py GC/MS.Graphical

Development and Preliminary Characterization of Polyester-Urethane Microparticles Used in Curcumin Drug Delivery System for Oropharyngeal Cancer.

Background and Objectives: Curcumin (Cc) as an active substance is known for its anti-inflammatory, anticoagulant, antioxidant, and anti-carcinogenic effects, together with its role in cholesterol regulation, and its use in different gastrointestinal derangements. On the other hand, curcumin can be used for its properties as an inactive substance, with Cc particles being more often tested in pharmaceutical formulations for drug delivery, with promising safety records and kinetics. The aim of this research was to obtain and characterize polyurethane microparticles that can be used as a carrier with a controlled Cc release. Materials and Methods: The in vitro samples were characterized by the Zetasizer procedure, and UV-Vis spectroscopy, while the in-vivo measurements on human subjects were performed by non-invasive skin assays (trans-epidermal water loss, erythema, and skin hydration). A total of 16 patients with oropharyngeal cancer stages II and III in equal proportions were recruited for participation. Results: The experimental values of sample characteristics using the Zetasizer identified a mean structural size of 215 nm in the polyester-urethane preparate (PU), compared to 271 nm in the curcumin-based PU. Although the size was statistically significantly different, the IPDI and Zeta potential did not differ significantly (22.91 mV vs. 23.74 mV). The average age during the study period was 57.6 years for patients in the PU group, respectively, and 55.1 years in those who received the curcumin preparations. The majority of oropharyngeal cancers were of HPV-related etiology. There were no significant side effects; 75.0% of patients in the PU group reporting no side effects, compared to 87.5% in the Cc group. The 48 h TEWL measurement at the end of the experiment found a statistically significant difference between the PU and the Cc group (2.2 g/h/m2 vs. 2.6 g/h/m2). The erythema assessment showed a starting measurement point for both research groups with a 5.1-unit difference. After 48 h, the difference between PU and PU_Cc was just 1.7 units (p-value = 0.576). The overall difference compared to the reference group with sodium lauryl sulfate (SLS) was statistically significant at a 95% significance level. Conclusions: Our findings indicate the obtaining of almost homogeneous particles with a medium tendency to form agglomerations, with a good capacity of encapsulation (around 60%), a medium release rate, and a non-irritative potential. Therefore, this polyester-urethane with Cc microparticles can be tested in other clinical evaluations.

Synthesis, Characterization and Antibacterial Activity of Novel β-cyclodextrin Polyurethane Materials

The advanced water treatment taken by organic micro-pollution or microbiological pollution water resource has been a hot issue of public concern. In this article, novel quaternary ammonium salt functionalized β-cyclodextrin polyurethane (QAS-β-CDPU) microparticles were successfully constructed for above-mentioned pollutants removal. By adjusting the proportion of the chlorine-containing monomers, we studied the effect of different quaternization degree (0%, 20%, 40%, 60%) on solvent resistance and thermal stability. Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) are recognized as significant human bacterial pathogens, which were used as model bacteria to investigate the antibacterial activity by contact-killing tests. Methylene blue (MB) served as a toxic organic model to quantify the dye wastewater remediation efficiency. Research shows that the reaction of β-cyclodextrin and diisocyanate can form a cyclodextrin-based carbamate network structure. Since both the cyclodextrin cavity and the carbamate network may remove the dye, the obtained polymer has a double advantage. Besides, the presence of quaternary ammonium groups enables QAS-β-CDPU microparticles to possess good bactericidal properties. When the quaternization degree is 60%, sterilization rates of QAS-β-CDPU microparticles are over 96% for S. aureus and E. coli. On basis of this simple, green and economical synthetic route, QAS-β-CDPU microparticles have the potential to become an ideal multifunctional material in water purification. Novel quaternary ammonium salt functionalized β-cyclodextrin polyurethane (QAS-β-CDPU) microparticles were successfully constructed for removing bacteria and dyes from wastewater.

Synthesis and Comparative Characterization of Different Microparticles used as Biomaterials in Dentistry

A biomaterial must be biologically compatible, mechanical, functional, corrosion resistant and easily adapt to clinical and laboratory technologies. Dental biomaterials are materials used to replace a part of a living system or to work closely with living tissue. Many scientific articles present different polymeric biocomposites with possible application in dentistry and this is a proof of the opportunity of a research in a field in full ascent and with great availability in the promotion of materials destined to �work under biological constraint� and which must also meet the functional requirements of a dental implant. The objectives of this research were to obtain and to comparatively evaluate different polymeric microparticles that can be used in dentistry. The samples based on poly(lactic-co-glycolic acid) and respectively polyurethane microparticles were characterized by pH and Zetasizer measurements, and in vitro cytotoxicity assays. The results indicate the obtaining of particles with a neutral pH, medium homogeneity, and with different tendencies to form agglomerations. Their low cytotoxicity, tested on the primary human gingival fibroblasts by MTT and LDH techniques, indicates that these microparticles are safe to be tested in further clinical evaluations.

Structure and properties of tough starch modified with rubber-based polyurethane microparticles

We prepared a novel covalent rubber-based polyurethane/starch composites material via a simple and effective method. Infrared, scanning electron microscopic, and mechanical tests demonstrated that polyurethane microparticles showed good compatibility with starch as the polyurethane content increases. This is mainly because of the urethane bond newly formed by –OH in starch and –NCO in rubber-based polyurethane. And when the rubber-based polyurethane content increased from 20% to 30%, its elongation at break improved by 116.9%. CPB30 showed excellent hydrophobicity and toughness, which showed potential application.

Synthesis and characterization of a polyurethane carrier used for a prolonged transmembrane transfer of a chili pepper extract.

PurposeRed chili peppers have been highly valued in gastronomy and traditional medicine since ancient times; it seems that it is not just an ingredient for food but also a good remedy for various medical conditions such as increased blood pressure and high levels of serum triglycerides and cholesterol, myocardial infarction, arthritis, and migraines. The objective of this study is the characterization of a new carrier used for encapsulated extract.MethodsChili pepper extract was obtained and was physically entrapped inside polyurethane microparticles in order to diminish the irritative potential of this extract. The particles were evaluated by Zetasizer measurements, small-angle neutron scattering and thermal analysis, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy; the encapsulation efficacy and the drug release profile were assessed by UV-Vis spectroscopy. Bioevaluations on mice skin were performed to predict the irritative potential of the samples.ResultsTwo different types of samples were compared: hollow polyurethane microparticles vs polyurethane particles containing the natural extract. The sizes of the particles were very similar, but the sample containing the extract presents three particle populations (the polydispersity index increases from 0.3 to 0.6 from one sample to another). The zeta-potential measurements and SEM images indicate a medium tendency to form clusters, while the UV-Vis study revealed an almost 70% encapsulation efficacy.ConclusionThe results suggest that encapsulation of a chili pepper extract inside polyurethane microparticles leads to a non-irritative product with a prolonged release: ~30% of encapsulated extract is released within the first 8 days and a maximum 45% is reached in 2 weeks.

Polyurethane Microparticles for Stimuli Response and Reduced Oxidative Degradation in Highly Porous Shape Memory Polymers.

Shape memory polymers (SMPs) have been found to be promising biomaterials for a variety of medical applications; however, the clinical translation of such technology is dependent on tailorable properties such as gravimetric changes in degradation environments. For SMPs synthesized from amino-alcohols, oxidation resulting in rapid mass loss may be problematic in terms of loss of material functionality as well as toxicity and cytocompatibility concerns. Control of gravimetric changes was achieved through the incorporation of small molecule antioxidants, either directly into the polymer matrix or included in microparticles to form a SMP composite material. With direct incorporation of small molecule phenolic antioxidant 2,2'-methylenebis(6- tert-butyl)-methylphenol (Methyl), SMPs displayed reduce strain recovery by more than 50% (Methyl) and increase elastic modulus from approximately 1.4 to 2.3 MPa, at the expense of the strain to failure being reduced from 45% to 32%. Importantly, such changes could not ensure retention of the antioxidants and therefore did not increase oxidative stability beyond 15 days in accelerated oxidative conditions (equivalent to approximately 800 days in porcine aneurysms) in all cases except for the inclusion of a hindered amine that capped network growth, which also resulted in shape memory reduction (only 80% recoverable strain achieved). However, the inclusion of antioxidants in microparticles was found to produce materials with similar thermomechanical ( Tg migration below 1.0 °C) and shape recovery of 100%, while increasing oxidative resistance compared to controls (oxidation onset was delayed by 3 days and material lifespan increased to approximately 20-22 days in accelerated oxidative solution or beyond 1000 days in the porcine aneurysm). The microparticle composite SMPs also act as a platform for environmental sensing, such as pH-dependent fluorescence shifts and payload release, as demonstrated by fluorescent dye studies using phloxine B and nile blue chloride and the release of antioxidants over a 3 week period. The use of polyurethane-urea microparticles in porous SMPs is demonstrated to increase biostability of the materials, by approximately 25%, and ultimately extend their lifespan for use in aneurysm occlusion as determined through calculated in vivo degradation rates corresponding to a porcine aneurysm environment.

Polyurethane-gold and polyurethane-silver nanoparticles conjugates for efficient immobilization of maltogenase

Preparation of polyurethane microparticles (PU) modified with gold (Au-NPs) or silver nanoparticles (Ag-NPs) for maltogenase immobilization was presented. The PU/Au-NPs and PU/Ag-NPs conjugates were prepared via adsorption of already synthesized nanoparticles on PU or via synthesis of nanoparticles within bulk of PU. Au-NPs of different size and Ag-NPs, synthesized by reduction of tetrachloroauric acid and silver nitrate with sodium citrate, were characterized by UV–vis and Dynamic Light Scattering technique. The best results (immobilization yield 90.0% and efficiency 83.5%) were achieved, when maltogenase was immobilized onto PU modified with Au-NPs(13nm) by adsorption method. Immobilized maltogenase was stable in time, after 25days of storage 95.2-98.6% of initial enzyme activity was remained. Moreover, the results revealed that stability of enzyme was improved upon immobilization on PU/Au-NPs(13nm) in comparison to PU without Au-NPs. Enhancement of photoluminescence after enzyme immobilization confirmed the successful attachment of maltogenase to PU/Au-NPs or PU/Ag-NPs via metal nanoparticles.

UV Curable Self-Healing Structural Epoxy Composite Materials Interfacial Polycondensation Microencapsulation of Healing Agent and Photo-Initiator

<div>The ability of polymeric coatings to self-heal itself from mechanical damage is explored in this paper. Polymeric coatings with self-healing property is one of the important aspects in modern science. It can be used in industries such as oil industry (protection against corrosion), mechanical engineering, aircraft, etc. The polyurethane (PU) microparticles were synthesized on the basis of polypropyleneglycol (PPG) and toluene diisocyanate (TDI) with a method of interfacial polycondensation at the interface water-benzene. Further to study the surface morphology of the microcapsules with healing agent (trimethylolpropanetriacrylate–TMPTA) obtained PU was applied the method of scanning electron and atomic force microscopy. The PU microparticles hollow inside have regular spherical shape with a diameter of 5-10 µm with a dense and smooth polymerics shell. The resulting polyimide–olyurethane (PI–PU) composites have high potential to regenerate damaged surfaces not only on the surface and also in the volume of composite within several minutes.</div><div> </div>

Development and in vitro evaluation of polyurethane microparticles as carrier for bevacizumab: an alternative treatment for retinopathy of prematurity

Retinopathy of prematurity (ROP) is known as an abnormal development of the blood capillaries from the eyes’ retina, and it is met to those infants that were born too early (premature) as its name suggests. Bevacizumab or Avastin belongs to the class of monoclonal antibodies and it is a possible treatment for those patients who have been diagnosed with a recurrent malignant glioma or other cancers due to its behavior to bind selectively to vascular endothelial growth factor (VEGF). In this study, eye drops based on a polyurethane carrier used for bevacizumab were obtained and the degradation of this carrier was studied for three weeks in two different media: simulated body fluid (SBF) and phosphate buffered saline (PBS); the influence of ultrasounds on the degradation of polyurethane carrier was also evaluated. The obtained results suggest that the polyurethane carrier presents a very slow degradation which is beneficial for drugs which require low release rates and on the other hand, the concentrations of the degradation products remain at a low level.DOI: http://dx.doi.org/10.3329/icpj.v3i6.18759 International Current Pharmaceutical Journal, May 2014, 3(6): 275-279

Preparation and Characterization of Various Starches Modified with Polyurethane Micro-Particles

Preparation and Characterization of Various Starches Modified with Polyurethane Micro-Particles

A one-pot preparation of silk fibroin modified with polyurethane micro-particles

In this study, polycaprolactone (PCL) tetrol and 4,4′-methylenedi-p-phenyl diisocyanate (MDI) were initially mixed for 10 min at 40 °C, then immediately added to a silk fibroin (SF)–water mixture. The obtained mixture was then added into a mixer to prepare the modified SF. The effects of the polyurethane prepolymer (PUP) content in the modified SF on the structure and properties of the modified SF were investigated. Fourier transform infrared spectroscopy (FTIR) revealed that urethane linkages formed between the SF and the PUP, and that the grafting ratio of the PUP used for preparing the modified SF was 99.1%. Polyurethane micro-particles were dispersed throughout the SF matrix of the modified SF and interacted with the SF matrix through urethane linkages, which strengthened the interface between the two phases. This special structure led to improved strength and elongation of the modified SF at break. The urethane-linked SF and PUP improved the mechanical properties and gave a higher thermal stability than other materials prepared by physical mixing. In addition, compared with the pure silk fibroin, the modified SF demonstrated a higher strength and elongation at break, along with better flexibility and hydrophobicity. These properties were also improved as the PU content was increased. Therefore, a simple and effective method to prepare high performance modified SF was successfully developed.

Tough thermoplastic starch modified with polyurethane microparticles by reactive extrusion

AbstractIn this work, a starch–water mixture was blended with polyurethane prepolymer (PUP) at 0, 5, 10, 15, and 20 wt% and extruded in a twin screw extruder. The ensuing results showed that the reaction ratio of PUP used for modified starch was 98.6 ± 0.3%. This was attributed to the polyurethane particles being formed under shear stress during extrusion processing. Each polyurethane particle contained many NCO groups with high reaction activity, which therefore increased the reaction probability of PUP micro‐particles with starch. The elastic and hydrophobic PUP played an important role in improving the properties of modified starch. SEM showed that the starch and polyurethane had good compatibility; the toughness, hydrophobicity, and thermal stability of modified starch thus sharply improved. This work provided a method for the preparation of high reaction efficiency modified starch.

Starches modified with polyurethane microparticles: Effects of hydroxyl numbers of polyols in polyurethane

In this work, three different types of polycaprolactone (PCL) polyols-PCL diol, PCL triol and PCL tertol were used to synthesize polyurethane prepolymers (PUPs) with 4, 4′-methylenedi-p-phenyl diisocyanate (MDI). The obtained PUPs then were used to modify thermoplastic starch (TPS) in an intensive mixer. Results showed that the grafting ratio of PUP used for modified starch was 99.6±0.2%, and the hydrophobicity of the modified starches improved compared to that of pure starch. With the increasing OH numbers of polyols in PUP, the compatibility between polyurethane and starch was improved. The toughness and thermal stability of modified starches were thus increased while the crystallinity of starch decreased. In addition, due to the existence of dense cross-linking, there was strong interaction between starch and PCL tertol based PUP, and the modified starch showed excellent toughness compared to pure starch. The superiorly formed, modified starch could have great potential applications.

Thermoplastic starch modified with polyurethane microparticles: Effects of hydrophilicity of polyurethane prepolymer

AbstractIt is important to chemically modify starch in an effective way. In this study, a series of polyurethane prepolymers (PUP) using 2,2‐dimethylol propionic acid (DMPA) as hydrophilic chain extender was synthesized and then used to modify starch by intensive mixing to obtain modified thermoplastic starch (TPS). The structure and properties of the modified TPS were investigated. The results showed that the elongation at break of the modified TPS increased from 5.4 to 9.8% with the content of PUP in modified TPS increasing from 10 to 20%, suggesting the PUP played an important role in the enhancement of the flexibility of the modified TPS sheet. The reaction ratio of PUP used for preparing the modified TPS was 98.5 ± 0.03%, indicating the modification was conducted efficiently because the multifunctional groups of polyurethane microparticles dramatically improved the reaction probability of the PUP modifier. The modified TPS prepared with PUP by adding DMPA showed increasing viscosity and decreasing contact angle due to the hydrophilicity of DMPA.

Tough Thermoplastic Starch Modified with Polyurethane Microparticles: The Effects of NCO Content in Prepolymers

In this work, polyurethane prepolymers (PUPs) with various NCO content proportions were synthesized and mixed reactively with a starch–water mixture to prepare modified thermoplastic starch (TPS) in an environmentally friendly way. The effects of polyurethane NCO content on the structure and/or properties of the modified TPS sheets were investigated. Results revealed that the reaction ratio of PUPs used for preparing the modified TPS was 99.8%, indicating that the PUPs were almost cross-linked to the starch matrix. With an increase of NCO content in PUP, the tensile strength of the modified TPS increased from 19.3 to 37.4 MPa, and the elongation from 1.7% to 17.2%. As the PUP’s NCO content increased, the amount of urethane linkage between PU microparticles and the starch matrix would increase. In addition, the compatibility of the two polymers was also improved resulting in the improvement of tensile properties. The urethane linkage between PU and starch therefore played an important role in improving the toughness of the modified TPS.

Assembly and Characterization of Polyurethane–Gold Nanoparticle Conjugates

AbstractThe PU/Au‐NPs conjugates based on poly(vinyl alcohol)‐containing polyurethane microparticles coated with Au‐NPs are prepared by a heat‐treated method. The PU/Au‐NPs conjugates are characterized by FT‐IR, SEM, TEM analysis. The appearance of characteristic peaks in the FT‐IR spectra at 1574 and 1624 cm−1, which are attributed to urethane groups, are presented for both PU and PU/Au‐NPs conjugate. The absorption band at 1716–1718 cm−1, attributed to the hydrogen‐bonded urethane carbonyl groups of PU/Au‐NPs(13nm)‐A is higher than that obtained for unmodified PU. The Au‐NPs(13nm) are found to be well dispersed in the PU. The Au‐NPs(3.5nm) tend toward agglomeration when they are entrapped within PU. It is determined, that Au‐NPs present in PU‐Au conjugates quench the luminescence of PU.

Hydrophobic Thermoplastic Starches Modified with Polyester-Based Polyurethane Microparticles: Effects of Various Diisocyanates

It is critical to prepare ductile and hydrophobic modified starch material in an effective and environmentally friendly way. In this work, polyurethane prepolymers (PUPs) with various isocyanates were synthesized and mixed reactively with thermoplastic starches (TPS) in an intensive mixer to prepare modified TPS. The effects of the isocyanates on the structure and properties of the modified TPS were then investigated by using scanning electron microscope (ESEM), tensile tester, and contact angle meter. Results showed that mechanical properties of the modified TPS were improved with the increase in hydrophobicity of the isocyanate. 4,4′-Methylenedi-p-phenyl diisocyanate (MDI) was hydrophobic, the NCO groups in PUPs were not easily consumed by water when modified starch was prepared, leading to a significantly increased reaction of the NCO groups with starch. As the amount of urethane bonds between starch and PUP increased, the compatibility between the two polymers was also improved, resulting in the impro...

Thermoplastic starches modified with polyurethane microparticles: The effects of isocyanate types in polyurethane

AbstractIn this work, polyurethane prepolymers (PUPs) with different isocyanate types were synthesized and mixed reactively with a starch–water mixture to prepare modified thermoplastic starch (TPS). The effects of the polyurethane isocyanate on the structure and properties of the modified TPS sheets were then investigated. Results from the scanning electron microscope (SEM), FTIR, mechanical tests, and contact angle (CA) confirmed that the modified TPS possessed a homogenous structure, good compatibility between starch and polyurethane (PU), excellent toughness, and hydrophobicity. The degradation experiment also revealed that the PU could be completely separated from the modified TPS. Additionally, almost 100% of the PU particles were cross‐linked to starch matrix, indicating the high efficiency of the modification. The NCO groups with higher reaction activity exhibited a higher number of urethane linkages between the starch matrix and the PU microparticle, resulting in improved compatibility of the two phases of the modified TPS and an increase in toughness.

Design and characterization of bi-soft segmented polyurethane microparticles for biomedical application

Bi-soft segmented poly(ester urethane urea) microparticles were prepared and characterized aiming a biomedical application. Two different formulations were developed, using poly(propylene glycol), tolylene 2,4-diisocyanate terminated pre-polymer (TDI) and poly(propylene oxide)-based tri-isocyanated terminated pre-polymer (TI). A second soft segment was included due to poly(ɛ-caprolactone) diol (PCL). Infrared spectroscopy, used to study the polymeric structure, namely its H-bonding properties, revealed a slightly higher degree of phase separation in TDI-microparticles. TI-microparticles presented slower rate of hydrolytic degradation, and, accordingly, fairly low toxic effect against macrophages. These new formulations are good candidates as non-biodegradable biomedical systems.