Titanium Dioxide and Calcium Sulfate Whiskers Are Used for the Preparation of High Performance Polypropylene and Reduce White Pollution.

The anti-aging agent TiO2-polyacrylonitrile (PAN) and the mechanical strengthening agent CSW-PAN were prepared by radical polymerization using rutile nano-titanium dioxide (TiO2) and anhydrous calcium sulfate whisker (CSW) as raw materials. The structures of TiO2-PAN and CSW-PAN were characterized using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Simultaneously, the mechanical properties, aging properties, and thermal stability of TiO2-PAN/CSW-PAN/polypropylene (PP) composites were studied, and the results showed that the surfaces of nano-titanium dioxide and calcium sulfate whiskers were successfully grafted with acrylonitrile. Owing to the introduction of new elements, such as acrylonitrile, nano-titanium dioxide and calcium sulfate whiskers have anti-aging properties. In comparison of the impact strength and tensile strength of TiO2-PAN/PP and TiO2-PAN/CSW-PAN/PP before aging, it can be proven that adding CSW-PAN can significantly enhance the mechanical properties of TiO2-PAN/CSW-PAN/PP. After 1000 h of aging, the tensile strength of the ternary composite TiO2-PAN/CSW-PAN/PP was 19.88 MPa when the addition amount of TiO2-PAN and CSW-PAN was 3%. Moreover, the impact strength of the ternary composite material TiO2-PAN/CSW-PAN/PP after 1000 h of aging is even better than that of non-aging pure PP materials, proving that the service life of improved PP products is extended, unnecessary waste and environmental pollution can be relieved, and the needs of specific engineering fields can be met.

Preparation of high-performance anti-aging polypropylene by modified nano-TiO2 and calcium sulfate whisker grafted acrylonitrile composite PP.

By employing the radical polymerization method, acrylonitrile (AN) was grafted on the surface of nano titanium dioxide (TiO2), and the calcium sulfate whisker (CSW) was modified using the coupling agent KH570 to provide ultraviolet (UV)-absorption capacity. The prepared TiO2-PAN and CSW-PAN materials can improve the anti-aging performance and mechanical properties of polypropylene (PP) and meet the application requirements of high-performance polypropylene. Further, the obtained PP composites show prolonged service life and application scope, which can effectively reduce white waste and avoid both resource waste and environmental pollution.

Inactivated vaccine fueled adaptive immune responses to Omicron in 2-year COVID-19 convalescents.

Over 3 years, humans have experienced multiple rounds of global transmission of SARS-CoV-2 and its variants. In addition, the widely used vaccines against SARS-CoV-2 involve multiple strategies of development and inoculation. Thus, the acquired immunity established among humans is complicated, and there is a lack of understanding within a panoramic vision. Here, we provided the special characteristics of the cellular and humoral responses in 2-year convalescents after inactivated vaccines, in parallel to vaccinated COVID-19 naïve persons and unvaccinated controls. The decreasing trends of the IgG, IgA, and NAb, but not IgM of the convalescents were reversed by the vaccination. Both cellular and humoral immunity in convalescents after vaccination were higher than the vaccinated COVID-19 naïve persons. Notably, inoculation with inactivated vaccine fueled the NAb to BA.1, BA.2, BA.4, and BA.5 in 2-year convalescents, much higher than the NAb during 6 months and 1 year after symptoms onset. And no obvious T cell escaping to the S protein was observed in 2-year convalescents after inoculation. The study provides insight into the complicated features of human acquired immunity to SARS-CoV-2 and variants in the real world, indicating that promoting vaccine inoculation is essential for achieving herd immunity against emerging variants, especially in convalescents.

Effect of ethanol osmotic dehydration on CO2 puffing and drying mechanism of potato.

In order to further improve the drying quality of potato slices, this study investigated the effects of EPD (CO2), HAD + EPD (CO2), EH + EPD (CO2), and FD on the quality and physicochemical properties of potato slices. The changes in solid loss (SL), obtained ethanol (OE), water loss (WL), and moisture content under different ethanol concentrations and soaking times were studied. The effects of WL, SL, OE, and moisture on puffing characteristics were also studied. The results show that in the EH + EPD (CO2) process, the use of ethanol and CO2 as the puffing media improves the puffing power. WL and OE have significant effects on hardness, crispness, expansion ratio, and ascorbic acid. The quality of potato slices puffed and dried by ethanol osmotic dehydration is better, which provides a new method for potato slice processing.

Synthesis and Characterization of a Novel DOPO-Based Flame Retardant Intermediate and Its Flame Retardancy as a Polystyrene Intrinsic Flame Retardant.

The research on intrinsic flame retardant has become a hot topic in the field of flame retardant. The synthesis of reactive flame-retardant monomer is one of the effective methods to obtain an intrinsic flame retardant. In addition, in view of the small molecular flame retardant easily migrates from the polymer during the use process, which leads to the gradual reduction of the flame retardant effect and even the gradual loss of flame retardant performance, and the advantages of atom transfer radical polymerization (ATRP) technology in polymer structure design and function customization, we first synthesized reactive flame retardant monomer 6-(hydroxymethyl)dibenzo[c,e][1,2]oxaphosphinine 6-oxide (FAA-DOPO), then synthesized polystyrene bromine (PS148-Br) macromolecular initiator by ATRP technology, and finally obtained block copolymer polystyrene-b-poly{6-(hydroxymethyl)dibenzo[c,e][1,2]oxaphosphinine 6-oxide} (PS-b-PFAA-DOPO) by the polymerization of FAA-DOPO initiated by macromolecular initiator PS148-Br by ATRP technology. The chemical structure of FAA-DOPO was characterized by 1D and 2D NMR (1H, 13C, DEPT 135, HSQC, COSY, NOE, and HMBC) spectra, Fourier transform infrared spectroscopy (FTIR), liquid chromatography-tandem mass spectrometry (LC-MS) and X-ray photoelectron spectroscopy (XPS). The chemical structure and molecular weight of PS-b-PFAA-DOPO were characterized by FTIR and gel permeation chromatography (GPC). The thermal and flame-retardant properties of PS-b-PFAA-DOPO were characterized by thermogravimetry analysis (TG), UL-94, limiting oxygen index (LOI), and microscale combustion calorimetry (MCC). It was found that FAA-DOPO could be used as a monomer for polymerization, although FAA-DOPO had a large steric hindrance from the chemical structure of FAA-DOPO, the UL-94 grade of PS-b-PFAA-DOPO reached the V-0 grade, and the LOI increased by 59.12% compared with PS148-Br.

Research on Microstructure and Mechanical Properties of Nylon6/Basalt Fiber/High-Density Polyethylene Composites.

As a representative polyolefin, high-density polyethylene (HDPE) has become one of the most commonly used commercial plastics with a wide range of applications in the world. However, its applications are limited due to poor mechanical properties. Hence, it is indispensable to develop composites with improved mechanical properties to overcome this disadvantage. In our work, basalt fiber (BF) and polyamide 6 (PA6)-reinforced HDPE composites were prepared. The effects of adding fiber, organic filler, and polar component maleic anhydride (MAH) on the microstructural characteristics of composites were investigated. Microstructural characterization evidenced that the binary-dispersed phase (PA6/BF) possesses a core-shell structure in which the component PA6 encapsulates the component BF, and the extent of encapsulation declines with the increase of MAH addition. It has been confirmed by scanning electron microscopy (SEM) observation that the microstructure is related to the interfacial tension of components. The effects of multicomponents on the crystallization behavior of composites were studied. The differential scanning calorimeter (DSC) analysis exhibited a significant change in the HDPE microstructure. Results showed that, as nucleating agents, PA6 and BF improve the crystallization rate in the cooling process. Furthermore, the rheological behavior of multicomponent composites was studied. With the increase of MAH, a clear improvement of complex viscosity and storage modulus was observed, of which the mechanism has been discussed in detail. The relationship between microstructure and heat resistance of composites was studied by a thermal deformation test under static fore. It is confirmed that the thermally conductive fiber BF and other components can form a thermally conductive network and channels, thus improving the heat resistance. It can become a composite material, which is suitable for special environments.

Synthesis of High-Molecular-Weight Bifunctional Additives with both Flame Retardant Properties and Antistatic Properties via ATRP.

Polystyrene (PS) is widely used in our daily life, but it is flammable and produces a large number of toxic gases and high-temperature flue gases in the combustion process, which limit its application. Improving the flame retardancy of PS has become an urgent problem to be solved. In addition, in view of the disadvantage that small-molecule flame retardants can easily migrate from polymers during use, which leads to the gradual reduction of the flame retardant effect or even loss of flame retardant performance, and the outstanding advantages of ATRP technology in polymer structure design and function customization, we used ATRP technology to synthesize the high-molecular-weight bifunctional additive PFAA-DOPO-b-PDEAEMA, which has flame retardant properties and antistatic properties. The chemical structure and molecular weight of PFAA-DOPO-b-PDEAEMA were characterized by FTIR, 1H NMR, GPC, and XPS. When the addition of PFAA-DOPO-b-PDEAEMA was 15 wt %, the limiting oxygen index (LOI) of polystyrene composites was 28.4%, which was 53.51% higher than that of pure polystyrene, the peak of the heat release rate (pHRR) was 37.61% lower than that of pure polystyrene, UL-94 reached V-0 grade, and the flame retardant index (FRI) was 2.98. In addition, when the PFAA-DOPO-b-PDEEMA content is 15 wt %, the surface resistivity and volume resistivity of polystyrene composites are 2 orders of magnitude lower than those of polystyrene. This research work provides a reference for the design of bifunctional and even multifunctional polymers.

An adjusted ELISpot-based immunoassay for evaluation of SARS-CoV-2-specific T-cell responses.

Like antibody evaluation, using an effective antigen-specific T-cell immunity assessment method in coronavirus disease 2019 (COVID-19) patients, survivors and vaccinees is crucial for understanding the immune persistence, prognosis assessment, and vaccine development for COVID-19. This study evaluated an empirically adjusted enzyme-linked immunospot assay for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T-cell immunity in 175 peripheral blood samples from COVID-19 convalescents and healthy individuals. Results of viral nucleic acid were used as the gold standard of infection confirmation. The SARS-CoV-2M peptide pool had higher sensitivity of 85% and specificity of 71% for the single peptide pool. For combined peptide pools, the parallel evaluation (at least one of the peptide pools is positive) of total peptide pools (S1&S2&M&N) had higher sensitivity (up to 93%), and the serial evaluation (all peptide pools are positive) of total peptide pools had higher specificity (up to 100%). The result of the serial evaluation was better than that of the parallel evaluation as a whole. The detection efficiency of M and N peptide pool serial evaluation appeared the highest, with a sensitivity of 80% and specificity of 93%. This T-cell immunity detection assay introduced in this report can achieve high operability and applicability. Therefore, it can be an effective SARS-CoV-2-specific cellular immune function evaluation method.

One-Year Sustained Cellular and Humoral Immunities in Coronavirus Disease 2019 (COVID-19) Convalescents.

BACKGROUND: The longitudinal antigen-specific immunity in COVID-19 convalescents is crucial for long-term protection upon individual re-exposure to SARS-CoV-2, and even more pivotal for ultimately achieving population-level immunity. We conducted this cohort study to better understand the features of immune memory in individuals with different disease severities at 1 year post-disease onset. METHODS: We conducted a systematic antigen-specific immune evaluation in 101 COVID-19 convalescents, who had asymptomatic, mild, moderate, or severe disease, through 2 visits at months 6 and 12 after disease onset. The SARS-CoV-2-specific antibodies, comprising neutralizing antibody (NAb), immunoglobulin (Ig) G, and IgM, were assessed by mutually corroborated assays (ie, neutralization, enzyme-linked immunosorbent assay [ELISA], and microparticle chemiluminescence immunoassay [MCLIA]). Meanwhile, T-cell memory against SARS-CoV-2 spike, membrane, and nucleocapsid proteins was tested through enzyme-linked immunospot assay (ELISpot), intracellular cytokine staining, and tetramer staining-based flow cytometry, respectively. RESULTS: SARS-CoV-2-specific IgG antibodies, and NAb, can persist among >95% of COVID-19 convalescents from 6 to 12 months after disease onset. At least 19/71 (26%) of COVID-19 convalescents (double positive in ELISA and MCLIA) had detectable circulating IgM antibody against SARS-CoV-2 at 12 months post-disease onset. Notably, numbers of convalescents with positive SARS-CoV-2-specific T-cell responses (≥1 of the SARS-CoV-2 antigen S1, S2, M, and N proteins) were 71/76 (93%) and 67/73 (92%) at 6 and 12 months, respectively. Furthermore, both antibody and T-cell memory levels in the convalescents were positively associated with disease severity. CONCLUSIONS: SARS-CoV-2-specific cellular and humoral immunities are durable at least until 1 year after disease onset.

Immune response pattern across the asymptomatic, symptomatic and convalescent periods of COVID-19.

We present an integrated analysis of urine and serum proteomics and clinical measurements in asymptomatic, mild/moderate, severe and convalescent cases of COVID-19. We identify the pattern of immune response during COVID-19 infection. The immune response is activated in asymptomatic infection, but is dysregulated in mild and severe COVID-19 patients. Our data suggest that the turning point depends on the function of myeloid cells and neutrophils. In addition, immune defects persist into the recovery stage, until 12 months after diagnosis. Moreover, disorders of cholesterol metabolism span the entire progression of the disease, starting from asymptomatic infection and lasting to recovery. Our data suggest that prolonged dysregulation of the immune response and cholesterol metabolism might be the pivotal causative agent of other potential sequelae. Our study provides a comprehensive understanding of COVID-19 immunopathogenesis, which is instructive for the development of early intervention strategies to ameliorate complex disease sequelae.

Environmental Resistance and Fatigue Behaviors of Epoxy/Nano-Boron Nitride Thermally Conductive Structural Film Adhesive Toughened by Polyphenoxy.

The thermally conductive structural film adhesive not only carries large loads but also exhibits excellent heat-transfer performance, which has huge application prospects. Herein, a novel epoxy (Ep) thermally conductive structural film adhesive was prepared using polyphenoxy (PHO) as the toughening agent and film former, boron nitride (BN) nanosheets as the thermally conductive filler, and polyester fabric as the carrier. When the amount of PHO in the epoxy matrix was 30 phr and the content of nano-BN was 30 wt.% (Ep/PHO30/nBN30), the adhesive resin system showed good film-forming properties, thermal stability, and thermal conductivity. The glass transition temperature of Ep/PHO30/nBN30 was 215 °C, and the thermal conductivity was 209.5% higher than that of the pure epoxy resin. The Ep/PHO30/nBN30 film adhesive possessed excellent adhesion and peeling properties, and the double-lap shear strength at room temperature reached 36.69 MPa, which was 21.3% higher than that of pure epoxy resin. The double-lap shear strength reached 15.41 MPa at 150 °C, demonstrating excellent high temperature resistance. In addition, the Ep/PHO30/nBN30 film adhesive exhibited excellent heat-aging resistance, humidity, and medium resistance, and the shear strength retention rate after exposure to the complicated environment reached more than 90%. The structural film adhesive prepared showed excellent fatigue resistance in the dynamic load fatigue test, the double-lap shear strength still reached 35.55 MPa after 1,000,000 fatigue cycles, and the strength retention rate was 96.9%, showing excellent durability and fatigue resistance.

Preparation and Thermal Decomposition Kinetics of a New Type of a Magnetic Targeting Drug Carrier.

We have designed a new magnetic targeting drug carrier Fe3O4-PVA with a core of triiron tetroxide (Fe3O4) and a shell made of polyvinyl alcohol (PVA) to improve the hydrophilicity of Fe3O4. With adriamycin hydrochloride as a model drug, this study goes on to measure the drug carrier performance of Fe3O4-PVA. In addition, the thermal stability and enthalpy of thermal decomposition of Fe3O4-PVA were measured using a differential scanning calorimeter with a non-isothermal decomposition method. The kinetics of thermal decomposition of Fe3O4-PVA were also investigated. Over the course of this study, it was determined that the resulting drug carrier Fe3O4-PVA exhibited high drug loading levels and excellent release levels.

Comparison of the performance of magnetic targeting drug carriers prepared using two synthesis methods.

In this paper, two methods were used to prepare the magnetic targeting drug carrier Fe3O4-PVA@SH, the step-by-step method and the one-pot method. The loading and release properties of the compound were measured. The results show that the Fe3O4-PVA@SH prepared using both methods exhibited excellent drug delivery properties in an environment that simulates human body fluid (pH 7.2) and a lysosomal in vitro simulation (pH 4.7). In applications such as drug delivery, magnetic targeted drug carriers prepared by both methods demonstrated superparamagnetism, high fat solubility, high hydroxyl content, and good water solubility.

Preparation of amphiphilic magnetic polyvinyl alcohol targeted drug carrier and drug delivery research.

Currently, magnetic applications have great potential for development in the field of drug carriers. In this paper, Fe3O4-PVA@SH, an amphiphilic magnetically targeting drug carrier, was prepared by using Fe3O4 and PVA with thiohydrazide-iminopropyltriethoxysilane(TIPTS). The loading capacity of Fe3O4-PVA@SH on Aspirin and the drug release kinetics of loaded drugs were studied. The obtained Fe3O4-PVA@SH exhibits excellent drug release properties in simulating the human body fluid environment (pH 7.2). Since magnetically targeting drug carriers are readily available and have excellent biocompatibility and the characteristics of drug release. This work's development, preparing amphiphilic magnetically targeting drug carriers in drug delivery and other fields, has great significance.

The study on microstructure and mechanical properties of multi-component composite based on HDPE.

The basalt fiber (BF) and polyamide 6 (PA6) reinforced HDPE composite were prepared; the effects of adding fiber, organic filler, and polar component maleic anhydride (MA) on the microstructural characteristics of composites were investigated. Microstructural characterization evidenced the binary-dispersed phase (PA6/BF) is of a core-shell structure in which the component PA6 encapsulates component BF, and the extent of encapsulates would decline with the MA adding. It is confirmed that the microstructure is related to the interfacial tension of components by the SEM observation and theoretical calculation. The effect of multi-component on the crystallization behavior of composites was investigated. Differential scanning calorimeter (DSC) analyses showed a significant change in the HDPE microstructure. It demonstrated PA6 and BF as a nucleation agent accelerated the crystallization rate under the cooling process. The corresponding crystallization kinetics and activation energy were further analyzed using the Jeziorny method, Avrami-Ozawa method, Kissinger method. The results showed MA markedly changed the crystal growth mechanism of the HDPE matrix to heterogeneous nucleation for acicular and tabular crystal growth during the annealing step. The lowest crystallinity energy and crystallinity were observed for BF/PA6/HDPE composites with 3 wt % MA. Furthermore, a clear improvement of mechanical properties (by 61%) were observed, which mechanism is discussed in detail. The mechanism of toughening is not only one, but the result of a variety of mechanisms together.

Corn stalk as starting material to prepare a novel adsorbent via SET-LRP and its adsorption performance for Pb(II) and Cu(II).

Corn stalk was used as the initial material to prepare a corn stalk matrix-g-polyacrylonitrile-based adsorbent. At first, the corn stalk was treated with potassium hydroxide and nitric acid to obtain the corn stalk-based cellulose (CS), and then the CS was modified by 2-bromoisobutyrylbromide (2-BiBBr) to prepare a macroinitiator. After that, polyacrylonitrile (PAN) was grafted onto the macroinitiator by single-electron transfer living radical polymerization (SET-LRP). A novel adsorbent AO CS-g-PAN was, therefore, obtained by introducing amidoxime groups onto the CS-g-PAN with hydroxylamine hydrochloride (NH2OH · HCl). FTIR, SEM and XPS were applied to characterize the structure of AO CS-g-PAN. The adsorbent was then employed to remove Pb(II) and Cu(II), and it exhibited a predominant adsorption performance on Pb(II) and Cu(II). The effect of parameters, such as temperature, adsorption time, pH and the initial concentration of metal ions on adsorption capacity, were examined in detail during its application. Results suggest that the maximum adsorption capacity of Pb(II) and Cu(II) was 231.84 mg g-1 and 94.72 mg g-1, and the corresponding removal efficiency was 72.03% and 63%, respectively. The pseudo-second order model was more suitable to depict the adsorption process. And the adsorption isotherm of Cu(II) accorded with the Langmuir model, while the Pb(II) conformed better to the Freundlich isotherm model.

A study on preparation of modified Graphene Oxide and flame retardancy of polystyrene composite microspheres.

In this paper, the ODOPM, a kind of 9, 10-dihydro-9-oxygen-heterooxy-10-phosphoro-10-oxygen (DOPO) derivative, was obtained by hydroxylation of DOPO. Further, a phosphorus nano-flame retardant (GO-ODOPM) was obtained by addition reaction with carboxylated Graphite Oxide (GO-COOH). And then Graphene Oxide/polystyrene (GO-ODOPM/PS) composite microspheres were obtained via suspension polymerization of styrene with GO-ODOPM. The decrease of the peak heat release rate (HRR) and total heat release rate (THR) for the GO-ODOPM/PS composite microspheres was obtained when the content of the additives was only 3.0 wt% is more than 36.2% and 33.6% compared with the pure PS microspheres, respectively. Thermogravimetric (TG), dynamic rheology and carbon residue analysis were used to study the flame-retardant mechanism of GO-ODOPM in PS microspheres. The results revealed that the addition of GO-ODOPM obviously reduced the fire hazard of polystyrene (PS) microspheres. Thus, this work provided a feasible method to design efficient flame retardants for enhancing fire safety of polymers.

Synthesis of PAN with adjustable molecular weight and low polydispersity index (PDI) value via reverse atom transfer radical polymerization.

The reverse atom transfer radical polymerization (RATRP) of acrylonitrile (AN) was carried out in N, N-dimethylformamide (DMF) with AIBN as initiator, FeCl3•6H2O/triphenylphosphine (PPh3) and FeCl3•6H2O/pentamethyldle-thylenetrlamlne (PMDETA) as catalytic systems, respectively. Effect of reaction time and initiator concentration on polymerization rate, molecular weight and molecular weight distribution were investigated in detail. The Fourier transform infrared spectrometer (FTIR) and 1H nuclear magnetic resonance spectroscopy (1HNMR) were employed to analyze the chain end of the PAN. Gel permeation chromatography (GPC) was applied to measure the molecular weight and polydispersity index (PDI) of PAN. The polymerization demonstrated a typical pseudo first-order kinetics characteristics as evidenced by the number-average molecular weights (Mn) increasing linearly with monomer conversion; the Mn decreasing with the increasing of the initiator concentration. Meanwhile, the low PDI value (<1.2) indicated the controllability of polymerization.

Study on initiating approach of (3-(tert-butylperoxy)propyl) trimethoxysilane on the polymerization of acrylonitrile as an initiator.

(3-(tert-butylperoxy)propyl) trimethoxysilane (TBPT), is a tailor-made new style silane coupling agent with peroxide group, which have ability of initiating polymerization. This study used TBPT to generate free radical, and initiated the polymerization of acrylonitrile (AN), thereby forming polyacrylonitrile (PAN) in two approaches, thermal initiation system and redox initiation system. Meanwhile this study bonded TBPT onto nano-TiO2 to get modified nano-TiO2 by means of the coupling function of TBPT, and then made the peroxide group of the modified nano-TiO2 decompose and initiate the polymerization of AN in thermal initiation system and redox initiation system respectively. The products were investigated and analyzed by FTIR, XPS and TG. The result showed that on one hand, in the products of the thermal initiation there was PAN, which both attached and unattached to the modified nano-TiO2; on the other hand, in the products of the redox initiation system the PAN unattached to the modified nano-TiO2 was produced, while the PAN attached to the modified nano-TiO2 was not.