Polymer Testing最新文献

Injection molding is widely used in the plastics manufacturing industry. However, there is a need to better understand and calculate the bonding strength between the injection-molded part and the insert, especially for semi-crystalline polymers. The weldability of semi-crystalline polymers differs from that of amorphous polymers. Semi-crystalline polymers cannot heal until they reach their glass transition temperature, unlike amorphous polymers, as the crystalline particles prevent molecule motion below this temperature. To account for this difference, we have developed a method that takes into effect the crystalline parts of semi-crystalline polymers in the calculation of healing. We used polypropylene (PP) in our experiments, and calculated healing with a new method based on the method we previously described for the healing of amorphous polymers.

To enhance the effectiveness of mechanical plastic recycling, it is best to separate different types of plastic during collection and recycling. This ensures the integrity and quality of recycled materials. For instance, the presence of polypropylene (PP) in recycled polyethylene (PE) can result in inconsistent and undesirable material, impacting the quality and performance of the recycled PE. This underscores the need for an analytical technique to accurately detect the presence of PP in recycled PE materials. In this study, we propose a quantitative analysis using a solution-based crystallization elution fractionation (CEF) technique to assess the polypropylene (PP) content in high-density polyethylene (HDPE) blends. The proposed methodology inherently distinguishes between the semi-crystalline PP matrix, including Homo-PP and Random copolymer PP, as well as the non-crystalline copolymer PP, and then quantifies each segment. A series of commercially available Ziegler–Natta catalyzed polymers were used to obtain the calibration curves per different type of PP materials, i.e., Homo-PP and Random copolymer PP. These calibration curves were then utilized to quantify Homo PP and copolymer PP (either semi-crystalline ethylene-propylene or amorphous ethylene-propylene) in different virgin polymer blends. The proposed methodology provides a comprehensive approach to characterizing the polypropylene content within polyethylene systems, especially in the context of qualifying polyolefin recyclate or polymer blends.

In the field of tissue engineering, synthetic and degradable polyesters like poly(ε-caprolactone) (PCL) and poly(ε-caprolactone-co-p-dioxanone) (PCLDX) are widely used as scaffolds. Our previous research revealed that thermal storage conditions could alter the surface texture of PCL and PCLDX scaffolds, which might influence cell-scaffold interactions in tissue engineering applications. These findings highlighted the importance of multi-scale characterization techniques to identify the scales most sensitive to external changes and the need for personalized surface texture analysis. Sterilization techniques, such as ethylene oxide and gamma radiation, are essential for ensuring the sterility of polymeric medical devices. However, these processes can significantly impact the bulk polymer properties and/or surface texture of the scaffolds, potentially affecting their biocompatibility, safety, and overall performance. Therefore, the influence of sterilization processes on the surface texture of PCLDX films and electrospun nanofibers and to correlate these findings with the thermal and physical properties of the polymer are essential and have been assessed. Our results demonstrated that ethylene oxide maintained the structural integrity and surface texture of PCLDX scaffolds, while gamma irradiation caused a significant reduction in molar mass and increased the number of hills (Shn) and dales (Sdn) on PCLDX samples. Despite these changes, both sterilization methods showed minimal effects on the thermal properties, such as melting temperature and degree of crystallinity, and surface wettability of the scaffolds. This comprehensive surface texture analysis highlights the importance of evaluating feature parameters such as Shn and Sdn for optimizing the performance and biocompatibility of polymeric scaffolds in tissue engineering.

This research developed a bio-based polymer composite using polylactic acid (PLA) and agro-industrial residues from coffee by-products (without chemical modification and the use of coupling agents or stabilizers). Agro-industrial residues, such as spent coffee ground (SCG) and coffee silver skin (CSS) as filler, were added into the PLA matrix in different percentages by weight, from 0.5 to 10 wt%. The bio-composites were prepared using solvent-cast films and were characterized by various techniques, including FT-IR, TGA, DSC, XRD, SEM and mechanical tests. Bio-composites' formation was verified using FT-IR and SEM; the material showed good interfacial interaction, with percentages between 3 and 5 wt%. XRD and DSC determined the percentage crystallinity in the bio-composites. SEM found that the bio-composites form crystals, showing their limits after mechanical testing. The bio-composites exhibited enhanced thermal and mechanical properties compared to neat PLA.

These bio-based composites show great potential for a wide range of applications in the food industry, including disposable and single-use materials, as well as food packaging. Moreover, their use can significantly contribute to the global demand for eco-friendly materials.

To enhance the phosphoric acid (PA) retention as well as maintain high proton conductivity of phosphoric acid doped proton exchange membranes at high temperature, we successfully design a series of phosphoric acid doped biobased composite membranes by incorporation of starch and graphene oxide (GO) into poly arylene ether ketones (PAEK). Proton transfer channels should be mainly built through dense hydrogen bonds formed from massive oxygen-containing groups of starch mainchain, which is confirmed by Molecular dynamics (MD) simulation, FT-IR and XRD analysis. The dense hydrogen-bond structure could construct fast proton transfer channels with extreme low doping level (0.00484 molH₃PO₄). The excellent PA retention properties with almost unchanged proton conductivity at high temperature (200 °C) for 600 min indicates that PA molecules are firmly fixed into membranes. Thus, in this study, we suggest a novel strategy for stablizing proton conductivity at high temperature and improving PA retention properties of PA doped membranes, which is building dense hydrogen-bond structure with low PA doping level.

Based on the results in this study and the Grotthuss proton transfer mechanism, dense hydrogen-bonds from oxygen-containing groups in polymer backbones should be more stable than hydrogen-bonds from massive H₃PO₄ molecules with high acid doping levels to promote proton conduction.

To recycle waste carbon fibers (CFs) and utilize them as a composite material with polyamide–6 (PA–6), the oxidation of the carbon surface is crucial for enhancing its bonding with PA–6 without damaging the waste CFs. However, the most effective oxygen-containing functional group (O–group) was hitherto unknown. In this study, computational simulations demonstrated that incorporating O–groups enhanced the interfacial bonding force via hydrogen bonding between the oxygen of the O–groups and hydrogen (N–H) of PA–6. Among various O–groups, the bonding of lactone groups to PA–6 was energetically most favorable, corroborated by different oxidation treatments such as acid, heat, and plasma. As the reaction time or temperature increased, the amount of O–groups, such as lactones, increased. Regardless of the oxidation treatment type, an increase in the amount of O–groups increased the interfacial force, and this tendency was predominantly observed in lactone groups. However, excessive surface oxidation introduced defects on the surface of CFs, which reduced the interfacial force. The modification of waste CFs by identifying the proposed mechanisms lays the groundwork for synthesizing high-quality waste CF composites.

In the transition from the laboratory to the clinic, the sterilization of medical devices becomes a fundamental and mandatory step to ensure patient safety. This work evaluates the impact of three different sterilization methods - autoclave, ethylene oxide and gamma irradiation - on the physicochemical properties and degradation kinetics of 3D-printed polycaprolactonecalcium deficient hydroxyapatite (PCLCDHA) scaffolds for bone regeneration. The in vitro degradation test was performed in phosphate buffer saline solution at 47 °C for 18 weeks by recording the evolution of pH, scaffold morphology, swelling degree, mass loss as well as polymer content, molecular weight and crystallinity. The results showed that under thermally accelerated degradation, the scaffolds underwent hydrolytic bulk degradation without altering the pH of the soaking medium nor compromising the morphology and integrity of the constructs. Although the structural integrity of the scaffolds was maintained, autoclaving severely deteriorated the properties of the polymer, resulting in a faster degradation pattern, confirming that it is not an appropriate sterilization method for PCLCDHA scaffolds. While ethylene oxide had no significant effect on degradation, gamma irradiation slightly accelerated hydrolysis by chain scission. However, due to the porous nature of the scaffolds, the use of ethylene oxide is inadvisable due to the risk of gas trapping in the pores. Therefore, gamma irradiation, a non-toxic, effective, predictable and reproducible sterilization method, is considered the most appropriate.

Aramid fabrics are widely used in bulletproof armor because of their excellent mechanical properties. Previous studies have shown that ultraviolet radiation has a negative effect on the mechanical properties of aramid yarn, so improving the mechanical properties and impact resistance of aramid fabrics under ultraviolet radiation has become a research focus. In this work, aramid fabric was modified with CuO and ZnO particles to improve its ballistic performance under ultraviolet radiation. The ballistic impact resistance response and microscopic failure mechanisms of aramid fabrics under ultraviolet radiation were analyzed in detail. Under ultraviolet radiation, the ballistic limit velocity (v_bl) of the CuO/ZnO-modified aramid fabric was 185.1 % greater than that of a neat fabric with a similar areal density. The v_bl of the single-layer modified fabric was 45.6 % greater than that of the two-layer neat fabrics. The decrease in the ballistic performance of the aramid fabric under ultraviolet radiation was attributed to surface damage caused by the fracture of the chemical structure of the fibers, which weakened the mechanical properties of the fabric. The numerical simulation results were highly consistent with the ballistic impact test results, and the error between the numerical simulation and experimental results was within 10 %. The effects of changes in the mechanical parameters of the fabrics on the protection mechanism and energy absorption structure during ballistic impact were investigated. The energy dissipation of the modified fabric was at least 147.7 % greater than that of the neat fabric, further explaining the significant improvement in the ballistic performance of CuO/ZnO-modified fabrics under ultraviolet radiation.

We have shown that the Irgacure 784 titanocene photoinitiator can be advantageously used to improve the light absorption, mechanical and nanosecond-regime laser ablation properties of urethane dimethacrylate (UDMA)-methyl methacrylate (MMA) polymer blends with photopolymerization using curing with green (520–525 nm) light. The hardness was found to be significantly higher (0.25–0.29 GPa) than that of other UDMA polymer blends photopolymerized using other initiator systems. The established 48–63 % degree of conversion is also comparable to that of similar other blends and is useful in many applications. The laser ablation and laser-induced breakdown spectroscopy (LIBS) properties of these polymers were studied at 266 and 532 nm laser wavelengths. The polymers showed consistently good laser ablation characteristics (reproducible, well-defined, shallow craters) at 266 nm wavelength, whereas at 532 nm, extensive carbonization and strong photothermal effects were observed. LIBS spectra of the blend shows lines of C, H, O, N and Ti as well as C₂ and CN bands, but provide many spectral windows for interference-free analytical measurements. Our findings indicate that UDMA-MMA polymer blends can be good candidates as target matrices for laser ablation-based measurements in the UV or Vis range, in applications like analytical spectroscopy or laser-initiated fusion research.