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polymers

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Nguyễn Gia Hào

Academic year: 2023

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The chemical composition of the different materials was analyzed by attenuated total reflection Fourier transform infrared (ATR/FTIR) spectroscopy (Shimazu, Tokyo, Japan). This is because the filler distribution changes with the different loads; at a low amount, such as 0.1 or 0.5 wt%, the dispersion is poor, while at higher amounts, such as 1.5 or 2.0 wt%, the large amount of filler is left to a filler agglomeration, forming weak points that act as localized stress concentration points with an increase of wear rate for a specialist improvement of wear. statistically significant differences in the effect of the media (air, distilled water, and artificial and natural lubricant) on the nanocomposites (p<0.0001). This may be due to the ability of carbon nanofiller (CNF) to improve resistance to oxidative degradation.

Comparing all materials in the spectra of UHMWPE with paraffine oil and with 1.0 wt% carbon nano-filler (curve d), the typical bands of the hydroxyapatite layer are clearly visible.

Table 1. Values of reference UP and of the nanocomposites at different immersion times
Table 1. Values of reference UP and of the nanocomposites at different immersion times

History of Cyclodextrin Nanosponges

Introduction

A comprehensive overview of the current state of these NS drug delivery systems is provided in the review by Caldera et al. NSs have proven to be able to keep up with the advances in nanomedicine, responding positively to the need for targeted treatments, which aim to improve the efficacy and reduce the adverse effects of the drugs. They have progressed from the relatively simple cross-linked networks of the 1960s to today's multifunctional polymers.

As Winston Churchill said: "The further back you can look, the further forward you are likely to look".

Origin and Historical Development of Nanosponges Over the Last 50 Years

At the end of the decade, NSs also found use as a substrate for enzyme immobilization. The role of NS in solubilization and stabilization of benzoporphyrin derivative monoacid ring A (BPDMA), all-trans retinoic acid (atRA) and on skin permeation of diclofenac (DIC) was tested. Physical mixing, kneading and sonication were used to prolong the duration of drug release [55].

In the last few years, all four CD-based nanosponge generations have been investigated in the pharmaceutical field [11]. β-CD cross-linked with DMC, CDI, DPC, PMDA and CA (citric acid), which belong to the first generation, have been used in pharmaceutical research (Table 1).

Figure 1. Number of papers on cyclodextrin-based nanosponges (CD NSs) published over the years from 1999 until 2019.
Figure 1. Number of papers on cyclodextrin-based nanosponges (CD NSs) published over the years from 1999 until 2019.

Conclusions and Future Perspectives

Fabrication and characterization of nifedipine loaded β-cyclodextrin nanosponges: An in vitro and in vivo evaluation. In vitro and in vivo therapeutic evaluation of camptothecin-encapsulated β-cyclodextrin nanosponges in prostate cancer.J. In vitro and in vivo evaluation of cyclodextrin-based nanosponges for improving oral bioavailability of atorvastatin calcium.Drug Dev.

Improving the solubility and in vitro cytotoxicity (anticancer activity) of ferulic acid by loading it into cyclodextrin nanosponges.Int.

Figure 4. Timeline of the historical development of cyclodextrin-based nanosponges.
Figure 4. Timeline of the historical development of cyclodextrin-based nanosponges.

Delayed Addition of Template Molecules Enhances the Binding Properties of

Diclofenac-Imprinted Polymers

  • Materials and Methods
  • Results and Discussion
  • Discussion
  • Conclusions

A preliminary study on the gelation time of the prepolymerization mixtures was performed in the same experimental conditions used to prepare diclofenac-imprinted polymers. These experiments show that turbidity was clearly noticeable with the naked eye after about 40 min from the start of the thermal polymerization process. Early formation of nanogel particles in the pre-polymerization mixture was confirmed by dynamic light scattering measurements performed and 20 minutes from the start of the polymerization (Figure S1).

Immediately after the addition of the template, a clear change in the color of the solution from yellow to dark orange was observed for all the mixtures considered. MIP-10: molecularly imprinted polymers (MIPs) prepared by template addition 10 min from the start of polymerization. The effect of the delayed template addition can be further highlighted by considering the imprinting factors, as reported in Figure 3.

When the template was present in the polymerization mixture from the beginning of the process, the resulting polymer (MIP-0) showed a relatively small but statistically significant imprinting effect for both diclofenac (α=0.05,n=11,t=3.509) and mefenamic acid (α=0.05,n=1.05,n=1.05,n=1). Due to the changing binding properties of the MIP, the binding selectivity was also clearly affected by the delayed template addition in the polymerization mixture. From the experimental data obtained, it is worth emphasizing that the addition of template molecules shortly after the start of the polymerization process (5-10 min) improved the imprinting effect and binding selectivity, mainly by increasing the binding affinity constant of the resulting polymer.

It is well known that monomers rapidly form oligomeric chains at the beginning of the polymerization process. We speculate that this effect may be controlled by the nature of the polymerization process.

Figure 1. (A) The MIP-10 polymerization mixture immediately before the addition of diclofenac;
Figure 1. (A) The MIP-10 polymerization mixture immediately before the addition of diclofenac;

Life-Cycle Assessment in the Polymeric Sector: A Comprehensive Review of Application Experiences

Applications

The LCA results showed that the environmental impact associated with the disposable network is mainly due to the production phase, due to the large volume of packages required throughout the year. It was found that the transport phase and different disposal scenarios had a significant impact on the sustainability and environmental impacts of the RPC system. The authors pointed out that there is no room for improvement in the production of PS granules, in the transport of materials and in trays.

The LCA analysis was performed according to an attribution approach and a consequential approach, in order to quantify the impact of the different technological approaches. Specifically, the comparison was performed using an endpoint approach level and the results were found to be related to the life cycle of the trays (Figure 6) and the DCs and ICs (Figure 7). The production of light and high-performance components for the automotive industry was also the subject of study by Vita and his colleagues [70].

However, due to the large contribution in terms of global warming of SS reinforced concrete (plus 35,508 kg CO2 eq.) the former formulation remained the largely preferred choice. Some of the observed reductions (material depletion and energy consumption) were attributed to the different level of maintenance required. The results obtained showed different environmental impacts of the three different vehicles in function of the considered phases.

The main goals that the authors addressed in the last section were the reduction of environmental impacts, proposing a different strategy, using LCA, compared to the default strategy. After the fabrication and chemical characterization of this CF/epoxy composite, they evaluated the environmental impact of the recyclability of the thermoset composite [104]. The reduction of environmental impacts and human health toxicity in the design and production of materials for X-ray shielding applications was investigated by Milanesio et al.

Data were normalized to the maximum value for a quick evaluation of the advantages and disadvantages of each material.

Figure 4. Municipal solid-waste life cycle. Reprinted from [36], © 2020 with permission from Wiley.
Figure 4. Municipal solid-waste life cycle. Reprinted from [36], © 2020 with permission from Wiley.

Future Outlooks

Green lines refer to impacts calculated for lead, red lines for composite samples and blue lines refer to steel impacts. Last but not least, the automotive sector is historically a very important sector of the Italian economy. Here, LCA practitioners can be spoiled both with the myriad of polymer components to examine and the ability to expand or constrain the boundaries, focusing on one impact category rather than another.

In this regard, it is worth considering to be aware of comparing scenarios that are likely to be similar, but which instead may show large differences simply by expanding the field under study.

Conclusions

Foamed polystyrene trays for fresh meat packaging: Life cycle inventory data collection and environmental impact assessment. Food Res. Attribution experience of a life cycle assessment application to highlight environmental hot spots in the production of polylactic acid foam trays for use in fresh food packaging. Plastics: A Life Cycle Assessment of Extra Virgin Olive Oil Bottles in Global Supply Chains. Durability.

Food losses, shelf life extension and environmental impact of a packaged cheesecake: A life cycle assessment. Food Res. Environmental and economic life cycle assessment of a lightweight solution for an automotive component: A comparison between polymer composites reinforced with talc-filled and hollow glass microspheres. J. Take-Home Messages from Life Cycle Assessment Applications in Lightweight Automotive Components.SAE Tech.

Comparative life cycle analysis of low pressure RTM, compression RTM and high pressure RTM manufacturing processes to produce CFRP car hoods. Optimal design of flax fiber reinforced polymer composite as a lightweight automotive component from a life cycle assessment point of view. Improving the Environmental Sustainability of Low Noise Pavements: Comparative Life Cycle Analysis of Reclaimed Asphalt and Crumb Rubber Based Hot Mix Technologies.Coatings2019,9, 343.

Optimization of a micro-CHP system based on polymer electrolyte membrane fuel cell and membrane reactor from economic and life cycle assessment point of view.Chem. Recycling treatment of carbon fiber/epoxy composites: Recycling and characterization of material and environmental impacts through life cycle assessment.

Epoxy Based Blends for Additive Manufacturing by Liquid Crystal Display (LCD) Printing

The Effect of Blending and Dual Curing on Daylight Curable Resins

Experimental 1. Materials and Method

A rate of rise test was used to characterize the viscoelastic properties of the samples after the thermal curing cycle was completed. The latter test was used to measure the glass transition temperature (Tg) of the resin, which was determined as Tanδpeak. The glass transition temperature (Tg) was measured as the midpoint of the heat capacity increment Δcp associated with the glass-to-rubber transition.

The total exothermic heat released was calculated from the area of ​​the DSC exothermic peak. Such an improvement can be explained as a result of the increased crosslinking density caused by the thermal curing that occurs in the first scan. Therefore, to account for such an effect, exposure times were increased from 25 s for cream resin to 30 s for CE7030 and CE5050 (Table 2).

However, the printing results are also affected by the flow of resin during the up and down movement of the platform. To account for the increased viscosity of the mixtures (Figure 3), the controlled motion of the platform was modified as indicated in Table 2 for the mixtures. The results of the DSC tests showed the presence of an exothermic peak for the uncured cream resin, which describes the presence of reactive moieties leading to the thermal curing of this system (see Figure 1).

DMA is a suitable technique for studying the thermal hardening of solid systems after vitrification [22]. The shift of the Tg peaks corresponding to the glass transition temperature (Tg) is due to the increased crosslinking density due to the crosslinking reactions that occur due to the thermal curing of the cream resin.

Table 1. Resin formulations studied.
Table 1. Resin formulations studied.

Hình ảnh

Figure 5. (A) Data from MTT assay expressed as NIH-3T3 cells viability (%) vs. untreated cells.
Table 1. Historical excursus of publications on CD-based NSs employed in pharmaceutical research.
Table 2. Historical excursus of publications on CD-based NSs employed in food, textile, environmental fields, etc.
Figure 3. Hierarchy analysis approach to choose the best cross-linker.
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