Research

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12 pages, 2706 KiB

Open AccessArticle

Detailed Study of the Correlation between Cross-Linking of Thick SU-8 and UV–NIR Optical Transmission/Photoluminescence Spectroscopy

by Abdullah Alharbi, Dhaifallah Almutairi, Hadba Hussain and Salman Alfihed

Polymers 2023, 15(19), 3866; https://doi.org/10.3390/polym15193866 - 23 Sep 2023

Viewed by 1124

Abstract

SU-8 polymers are promising materials for various applications due to their low cost, excellent thermal stability, and outstanding mechanical properties. Cross-linking of SU-8 is a crucial process that determines the properties of the materials. This study investigates the effect of cross-linking of free-standing [...] Read more.

SU-8 polymers are promising materials for various applications due to their low cost, excellent thermal stability, and outstanding mechanical properties. Cross-linking of SU-8 is a crucial process that determines the properties of the materials. This study investigates the effect of cross-linking of free-standing SU-8 films on optical transmission and PL emission under various curing conditions. Our findings show that an increase in the cross-linking density reduces optical transmission and causes a red shift of the PL emission band peaks. By directly measuring the optical response of the isolated SU-8, we remove any uncertainty due to the substrate’s presence. Moreover, we show that optical transmission and PL spectroscopy are two non-distractive techniques that can be employed to monitor the curing of the SU-8. This finding enhances our understanding of the cross-linking process in SU-8 and paves the way to further enhance the properties of the SU-8 polymer for various electronics and optoelectronics applications. Full article

(This article belongs to the Special Issue Synthesis, Processing, Structure and Properties of Polymer Materials II)

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13 pages, 4719 KiB

Open AccessArticle

Investigation on Nanocomposites of Polysulfone and Different Ratios of Graphene Oxide with Structural Defects Repaired by Cellulose Nanocrystals

by Yansong Yu, Yiwen Hu, Xiuduo Song, Jinyao Chen, Jian Kang, Ya Cao and Ming Xiang

Polymers 2023, 15(18), 3821; https://doi.org/10.3390/polym15183821 - 19 Sep 2023

Viewed by 732

Abstract

In this manuscript, nanofillers of graphene oxide (GO) and cellulose nanocrystal (CNC) with different weight ratios (G/C ratios), named GC 2:1, GC 4:1, GC 8:1, GC 16:1, and GC 32:1, were successfully prepared. Characterization methods such as Raman spectroscopy, X-ray photoelectron spectrometry (XPS), [...] Read more.

In this manuscript, nanofillers of graphene oxide (GO) and cellulose nanocrystal (CNC) with different weight ratios (G/C ratios), named GC 2:1, GC 4:1, GC 8:1, GC 16:1, and GC 32:1, were successfully prepared. Characterization methods such as Raman spectroscopy, X-ray photoelectron spectrometry (XPS), and thermogravimetric analysis (TGA) were performed. Additionally, the effects of these samples on the thermal stability, mechanical properties, and gas barrier properties of polysulfone (PSF) nanocomposites were investigated. A hydrophilic interaction took place between CNC and GO; as a consequence, CNCs were modified on the surface of GO, thus repairing the structural defects of GO. With the increase in G/C ratios, the repair effect of insufficient CNCs on the defects of GO decreased. The G/C ratio had a great influence on the improvement of mechanical properties, thermal stability, and gas barrier properties of nanocomposites. Compared with PSF/GC 2:1 and PSF/GC 32:1, the differences in the growth rates of tensile strength, elongation at break, and Young’s modulus were 30.0%, 39.4%, and 15.9%, respectively; the difference in T_d 3% was 7 °C; the difference in decline rate of O₂ permeability was 40.0%. Full article

(This article belongs to the Special Issue Synthesis, Processing, Structure and Properties of Polymer Materials II)

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27 pages, 4511 KiB

Open AccessArticle

A Visco-Hyperelastic Constitutive Model to Characterize the Stress-Softening Behavior of Ethylene Propylene Diene Monomer Rubber

by Xiu Liu, Chen Liu, Dingxiang Zhu and Jianguo Lin

Polymers 2023, 15(16), 3388; https://doi.org/10.3390/polym15163388 - 12 Aug 2023

Viewed by 1155

Abstract

Uniaxial and biaxial cyclic tensile tests and stress relaxation tests were performed on the ethylene propylene diene monomer (EPDM) material to investigate its stress-softening effect. The experimental results reveal that the EPDM material presents a significant Mullins effect during the cyclic stretching processes. [...] Read more.

Uniaxial and biaxial cyclic tensile tests and stress relaxation tests were performed on the ethylene propylene diene monomer (EPDM) material to investigate its stress-softening effect. The experimental results reveal that the EPDM material presents a significant Mullins effect during the cyclic stretching processes. Furthermore, it is found that the deformation of the EPDM material does not return to zero simultaneously with the stress, due to the viscoelasticity of the EPDM material. Therefore, this study combines pseudo-elasticity theory and viscoelastic theory to propose a visco-hyperelastic constitutive model. The proposed model is used to fit and analyze the uniaxial and biaxial cyclic test results of EPDM and a comparison is conducted with the corresponding hyper-elastic constitutive model. The results show that the proposed model is in good agreement with the experimental data and superior to the hyper-elastic constitutive model, especially when it comes to the stress-softening unloading process. This work is conducive to accurately characterizing the stress-softening behavior of rubber-like materials at large deformation and can provide some theoretical guidance for their widespread application in industry. Full article

(This article belongs to the Special Issue Synthesis, Processing, Structure and Properties of Polymer Materials II)

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15 pages, 3742 KiB

Open AccessArticle

Temperature and Frequency Dependence of the Dynamic Viscoelastic Properties of Silicone Rubber

by Xiu Liu, Dingxiang Zhu, Jianguo Lin and Yongjun Zhang

Polymers 2023, 15(14), 3005; https://doi.org/10.3390/polym15143005 - 10 Jul 2023

Cited by 1 | Viewed by 1881

Abstract

Temperature–frequency sweep tests were performed on silicone rubber to investigate the dynamic viscoelastic properties. The test results show that the viscoelasticity of silicone rubber presents significant temperature dependence and frequency dependence. The dynamic viscoelastic test curves at different temperatures can be shifted along [...] Read more.

Temperature–frequency sweep tests were performed on silicone rubber to investigate the dynamic viscoelastic properties. The test results show that the viscoelasticity of silicone rubber presents significant temperature dependence and frequency dependence. The dynamic viscoelastic test curves at different temperatures can be shifted along the logarithmic frequency coordinate axis to construct smooth master curves at the reference temperature of 20 °C, covering a frequency range of 10 decades, which indicates thermorheological simplicity on a macro level and frequency temperature equivalence of the silicone rubber material in the experimental temperature range. The van Gurp–Palmen plot and Cole–Cole plot for the test data at various temperatures merge into a common curve, which further validates thermorheological simplicity. The temperature dependent shift factors of silicone rubber material were well characterized by the Williams–Landel–Ferry equation. Moreover, the fractional-order differential Kelvin (FDK) model, the fractional-order differential Zener (FDZ) model, and the improved fractional-order differential Zener (iFDZ) model were used to model the asymmetric loss factor master curve. The result shows that the iFDZ model is in good agreement with the test results, indicating that this model is suitable for describing the asymmetry of dynamic viscoelastic properties of silicone rubber. Full article

(This article belongs to the Special Issue Synthesis, Processing, Structure and Properties of Polymer Materials II)

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23 pages, 5151 KiB

Open AccessArticle

One-Step Multifunctionalization of Flax Fabrics for Simultaneous Flame-Retardant and Hydro-Oleophobic Properties Using Radiation-Induced Graft Polymerization

by Jamila Taibi, Sophie Rouif, Bruno Améduri, Rodolphe Sonnier and Belkacem Otazaghine

Polymers 2023, 15(9), 2169; https://doi.org/10.3390/polym15092169 - 02 May 2023

Cited by 1 | Viewed by 1713

Abstract

This study concerns the one-step radiografting of flax fabrics with phosphonated and fluorinated polymer chains using (meth)acrylic monomers: dimethyl(methacryloxy)methyl phosphonate (MAPC1), 2-(perfluorobutyl)ethyl methacrylate (M4), 1H,1H,2H,2H-perfluorooctyl acrylate (AC6) and 1H,1H,2H,2H-perfluorodecyl methacrylate (M8). The multifunctionalization of flax fabrics using a pre-irradiation procedure at 20 and [...] Read more.

This study concerns the one-step radiografting of flax fabrics with phosphonated and fluorinated polymer chains using (meth)acrylic monomers: dimethyl(methacryloxy)methyl phosphonate (MAPC1), 2-(perfluorobutyl)ethyl methacrylate (M4), 1H,1H,2H,2H-perfluorooctyl acrylate (AC6) and 1H,1H,2H,2H-perfluorodecyl methacrylate (M8). The multifunctionalization of flax fabrics using a pre-irradiation procedure at 20 and 100 kGy allows simultaneously providing them with flame retardancy and hydro- and oleophobicity properties. The successful grafting of flax fibers is first confirmed by FTIR spectroscopy. The morphology of the treated fabrics, the regioselectivity of grafting and the distribution of the fluorine and phosphorus elements are assessed by scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (SEM-EDX). The flame retardancy is evaluated using pyrolysis combustion flow calorimetry (PCFC) and cone calorimetry. The hydro- and oleophobicity and water repellency of the treated fabrics is established by contact angle and sliding angle measurements, respectively. The grafting treatment of flax irradiated at 100 KGy, using M8 and MAPC1 monomers (50:50) for 24 h, allows achieving fluorine and phosphorus contents of 8.04 wt% and 0.77 wt%, respectively. The modified fabrics display excellent hydro-oleophobic and flame-retardant properties with water and diiodomethane contact angles of 151° and 131°, respectively, and a large decrease in peak of heat release rate (pHRR) compared to pristine flax (from 230 W/g to 53 W/g). Relevant results are also obtained for M4 and AC6 monomers in combination with MAPC1. For the flame retardancy feature, the presence of fluorinated groups does not disturb the effect of phosphorus. Full article

(This article belongs to the Special Issue Synthesis, Processing, Structure and Properties of Polymer Materials II)

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22 pages, 2820 KiB

Open AccessArticle

Effect of Hybrid Filler, Carbon Black–Lignocellulose, on Fire Hazard Reduction, including PAHs and PCDDs/Fs of Natural Rubber Composites

by Przemysław Rybiński, Ulugbek Zakirovich Mirkhodjaev, Witold Żukowski, Dariusz Bradło, Adam Gawlik, Jakub Zamachowski, Monika Żelezik, Marcin Masłowski and Justyna Miedzianowska

Polymers 2023, 15(8), 1975; https://doi.org/10.3390/polym15081975 - 21 Apr 2023

Cited by 1 | Viewed by 1075

Abstract

The smoke emitted during thermal decomposition of elastomeric composites contains a significant number of carcinogenic and mutagenic compounds from the group of polycyclic aromatic hydrocarbons, PAHs, as well as polychlorinated dibenzo-p-dioxins and furans, PCDDs/Fs. By replacing carbon black with a specific amount of [...] Read more.

The smoke emitted during thermal decomposition of elastomeric composites contains a significant number of carcinogenic and mutagenic compounds from the group of polycyclic aromatic hydrocarbons, PAHs, as well as polychlorinated dibenzo-p-dioxins and furans, PCDDs/Fs. By replacing carbon black with a specific amount of lignocellulose filler, we noticeably reduced the fire hazard caused by elastomeric composites. The lignocellulose filler reduced the parameters associated with the flammability of the tested composites, decreased the smoke emission, and limited the toxicity of gaseous decomposition products expressed as a toximetric indicator and the sum of PAHs and PCDDs/Fs. The natural filler also reduced emission of gases that constitute the basis for determination of the value of the toximetric indicator W_LC50SM. The flammability and optical density of the smoke were determined in accordance with the applicable European standards, with the use of a cone calorimeter and a chamber for smoke optical density tests. PCDD/F and PAH were determined using the GCMS-MS technique. The toximetric indicator was determined using the FB-FTIR method (fluidised bed reactor and the infrared spectrum analysis). Full article

(This article belongs to the Special Issue Synthesis, Processing, Structure and Properties of Polymer Materials II)

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16 pages, 4781 KiB

Open AccessArticle

Synthesis, Characterization and Application of a New Functionalized Polymeric Sorbent Based on Alkenylphoshine Oxide

by Sławomir Frynas and Monika Wawrzkiewicz

Polymers 2023, 15(6), 1591; https://doi.org/10.3390/polym15061591 - 22 Mar 2023

Cited by 1 | Viewed by 1398

Abstract

A novel phosphorus-containing sorbent (CyP(Ph)4–DVB) was prepared by copolymerizing divinylbenzene (DVB) with bis α,β-unsaturated phosphorylated cyclohexene (CyP(Ph)4). ATR-FT-IR indicated that the phosphinoyl group was introduced into the sorbent structure. The thermal properties of the sorbent were investigated using a differential scanning calorimeter (DSC), [...] Read more.

A novel phosphorus-containing sorbent (CyP(Ph)4–DVB) was prepared by copolymerizing divinylbenzene (DVB) with bis α,β-unsaturated phosphorylated cyclohexene (CyP(Ph)4). ATR-FT-IR indicated that the phosphinoyl group was introduced into the sorbent structure. The thermal properties of the sorbent were investigated using a differential scanning calorimeter (DSC), which revealed that (CyP(Ph)4–DVB) is more stable than poly(DVB). The CyP(Ph)4–DVB was applied for cationic dye removal, such as C.I. Basic Yellow 2 (BY2) and C.I. Basic Blue 3 (BB3). Batch adsorption tests suggested that the Freundlich isotherm model seemed to be the better one for the description of equilibrium sorption data at equilibrium, rather than the Langmuir or Temkin models. The Freundlich constants concerning the adsorption capacity of CyP(Ph)4–DVB, k_F, were calculated as 14.2 mg^1−1/nL^1/n/g for BY2 and 53.7 mg^1−1/nL^1/n/g for BB3. Full article

(This article belongs to the Special Issue Synthesis, Processing, Structure and Properties of Polymer Materials II)

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16 pages, 6897 KiB

Open AccessArticle

Study on Press Formability and Properties of UV-Curable Polyurethane Acrylate Coatings with Different Reactive Diluents

by Woo-Chan Choi, Vishal Gavande, Dong-Yun Kim and Won-Ki Lee

Polymers 2023, 15(4), 880; https://doi.org/10.3390/polym15040880 - 10 Feb 2023

Cited by 3 | Viewed by 2004

Abstract

UV-curable coatings have numerous advantages, including environmental sustainability due to 100% solid content, economic feasibility attributable to relatively fast curing time, decent appearance, mechanical properties, chemical resistance, and abrasion resistance. However, UV-curable polyurethane acrylate coatings on metals apparently restrict their engineering applications owing [...] Read more.

UV-curable coatings have numerous advantages, including environmental sustainability due to 100% solid content, economic feasibility attributable to relatively fast curing time, decent appearance, mechanical properties, chemical resistance, and abrasion resistance. However, UV-curable polyurethane acrylate coatings on metals apparently restrict their engineering applications owing to low mechanical properties and poor thermal stability, giving UV-curable coatings less flexibility and formability. In this study, we evaluated the property change of films according to the type of reactive diluents that lowers the viscosity of UV-curing coatings for pre-coated metal and has a substantial effect on the curing rate, viscoelastic properties, adhesive properties, and flexibility of the film. Moreover, there are many changes in the properties of coatings according to varied curing conditions in order to evaluate the oxygen inhibition phenomenon during the curing process in the atmosphere. In particular, to evaluate the effect of reactive diluents on forming formability, which is the most crucial property for the pre-coated metal, this study used conventional formability tests, such as t-bending or the Erichsen test. Moreover, a cross-die cup drawing mold with a similar form as failure and Safety Zone was utilized in order to obtain clearer information on its actual formability. The analysis on the effect of failure and safety zone on the material used in press forming was conducted by assessing limit punch height and forming a limit diagram of the manufactured film according to varied reactive diluents. Full article

(This article belongs to the Special Issue Synthesis, Processing, Structure and Properties of Polymer Materials II)

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17 pages, 7674 KiB

Open AccessArticle

Kinetic Study of the Effective Thermal Polymerization of a Prebiotic Monomer: Aminomalononitrile

by Carlos Hortelano, Marta Ruiz-Bermejo and José L. de la Fuente

Polymers 2023, 15(3), 486; https://doi.org/10.3390/polym15030486 - 17 Jan 2023

Cited by 1 | Viewed by 1116

Abstract

Aminomalononitrile (AMN), the HCN formal trimer, is a molecule of interest in prebiotic chemistry, in fine organic synthesis, and, currently, in materials science, mainly for bio-applications. Herein, differential scanning calorimetry (DSC) measurements by means of non-isothermal experiments of the stable AMN p-toluenesulfonate [...] Read more.

Aminomalononitrile (AMN), the HCN formal trimer, is a molecule of interest in prebiotic chemistry, in fine organic synthesis, and, currently, in materials science, mainly for bio-applications. Herein, differential scanning calorimetry (DSC) measurements by means of non-isothermal experiments of the stable AMN p-toluenesulfonate salt (AMNS) showed successful bulk AMN polymerization. The results indicated that this thermally stimulated polymerization is initiated at relatively low temperatures, and an autocatalytic kinetic model can be used to appropriately describe, determining the kinetic triplet, including the activation energy, the pre-exponential factor, and the mechanism function (E_α, A and f(α)). A preliminary structural characterization, by means of Fourier transform infrared (FTIR) spectroscopy, supported the effective generation of HCN-derived polymers prepared from AMNS. This study demonstrated the autocatalytic, highly efficient, and straightforward character of AMN polymerization, and to the best of our knowledge, it describes, for the first time, a systematic and extended kinetic analysis for gaining mechanistic insights into this process. The latter was accomplished through the help of simultaneous thermogravimetry (TG)-DSC and the in situ mass spectrometry (MS) technique for investigating the gas products generated during these polymerizations. These analyses revealed that dehydrocyanation and deamination processes must be important elimination reactions involved in the complex AMN polymerization mechanism. Full article

(This article belongs to the Special Issue Synthesis, Processing, Structure and Properties of Polymer Materials II)

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15 pages, 5826 KiB

Open AccessArticle

Anti-Fouling and Anti-Biofilm Performance of Self-Polishing Waterborne Polyurethane with Gemini Quaternary Ammonium Salts

by Yi Zhang, Tao Ge, Yifan Li, Jinlin Lu, Hao Du, Ling Yan, Hong Tan, Jiehua Li and Yansheng Yin

Polymers 2023, 15(2), 317; https://doi.org/10.3390/polym15020317 - 07 Jan 2023

Viewed by 2299

Abstract

Biofilms are known to be difficult to eradicate and control, complicating human infections and marine biofouling. In this study, self-polishing and anti-fouling waterborne polyurethane coatings synthesized from gemini quaternary ammonium salts (GQAS), polyethylene glycol (PEG), and polycaprolactone diol (PCL) demonstrate excellent antibiofilm efficacy. [...] Read more.

Biofilms are known to be difficult to eradicate and control, complicating human infections and marine biofouling. In this study, self-polishing and anti-fouling waterborne polyurethane coatings synthesized from gemini quaternary ammonium salts (GQAS), polyethylene glycol (PEG), and polycaprolactone diol (PCL) demonstrate excellent antibiofilm efficacy. Their anti-fouling and anti-biofilm performance was confirmed by a culture-based method in broth media, with the biofilm formation factor against Gram-positive (S. aureus) and Gram-negative bacterial strains (E. coli) for 2 days. The results indicate that polyurethane coatings have excellent anti-biofilm activity when the content of GQAS reached 8.5 wt% against S. aureus, and 15.8 wt% against E. coli. The resulting waterborne polyurethane coatings demonstrate both hydrolytic and enzymatic degradation, and the surface erosion enzymatic degradation mechanism enables them with good self-polishing capability. The extracts cyto-toxicity of these polyurethane coatings and degradation liquids was also systematically studied; they could be degraded to non-toxic or low toxic compositions. This study shows the possibility to achieve potent self-polishing and anti-biofilm efficacy by integrating antibacterial GQAS, PEG, and PCL into waterborne polyurethane coatings. Full article

(This article belongs to the Special Issue Synthesis, Processing, Structure and Properties of Polymer Materials II)

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13 pages, 2577 KiB

Open AccessArticle

Mechanical and Thermal Properties of Functionally Graded Polyolefin Elastomer Foams

by Ehsan Rostami-Tapeh-Esmaeil, Sahar Shojaei and Denis Rodrigue

Polymers 2022, 14(19), 4124; https://doi.org/10.3390/polym14194124 - 01 Oct 2022

Cited by 9 | Viewed by 2422

Abstract

In this work, uniform and graded polyolefin elastomer (POE) foams were prepared using a single-step technology based on a fixed chemical blowing agent (azodicarbonamide) concentration of 4 phr (parts per hundred rubber). The effect of molding temperature, including the average temperature (T [...] Read more.

In this work, uniform and graded polyolefin elastomer (POE) foams were prepared using a single-step technology based on a fixed chemical blowing agent (azodicarbonamide) concentration of 4 phr (parts per hundred rubber). The effect of molding temperature, including the average temperature (T_avg) and temperature difference (ΔT), on the foams’ morphology, mechanical properties (tension, compression and hardness) and thermal conductivity was investigated. Two series of samples were produced by fixing T_avg with different ΔT or setting different ΔT, leading to different T_avg. The morphological analyses showed that two or three regions inside the foams were produced depending on the molding conditions, each region having different cellular structure in terms of cell size, cell density and cell geometry. The results obtained for the conditions tested showed a range of density (0.55–0.72 g/cm³), tensile modulus (0.44–0.70 MPa) and compression elastic modulus (0.35–0.71 MPa), with a thermal conductivity between 0.125 and 0.180 W/m.K. Based on the information provided, it can be concluded that the foam’s properties can be easily controlled by the cellular structure and that graded samples are more interesting than uniform ones, especially for thermal insulation applications, such as packaging, construction, transportation, automotive and aerospace industries. Full article

(This article belongs to the Special Issue Synthesis, Processing, Structure and Properties of Polymer Materials II)

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17 pages, 6551 KiB

Open AccessArticle

Synthesis of Iron(II) Clathrochelate-Based Poly(vinylene sulfide) with Tetraphenylbenzene Bridging Units and Their Selective Oxidation into Their Corresponding Poly(vinylene sulfone) Copolymers: Promising Materials for Iodine Capture

by Noorullah Baig, Suchetha Shetty, Sameh S. Habib, Ali A. Husain, Saleh Al-Mousawi and Bassam Alameddine

Polymers 2022, 14(18), 3727; https://doi.org/10.3390/polym14183727 - 07 Sep 2022

Cited by 12 | Viewed by 1895

Abstract

The development of a simple and efficient synthetic methodology to engineer functional polymer materials for gas adsorption is necessary due to its relevance for various applications. Herein, we report the synthesis of metalorganic poly(vinylene sulfide) copolymers CTP1-3 with iron(II) clathrochelate of various side [...] Read more.

The development of a simple and efficient synthetic methodology to engineer functional polymer materials for gas adsorption is necessary due to its relevance for various applications. Herein, we report the synthesis of metalorganic poly(vinylene sulfide) copolymers CTP1-3 with iron(II) clathrochelate of various side groups connected by tetraphenylbenzene units. CTP1-3 were subsequently oxidized into their respective poly(vinylene sulfone) copolymers CTP4-6 under green reaction conditions. The target copolymers CTP1-6 were characterized using various instrumental analysis techniques. Examination of the iodine adsorption properties of the copolymers revealed high iodine uptake properties, reaching 2360 mg g⁻¹ for CTP2, and whose reusability tests proved its efficient regeneration, thus proving the importance of iron(II) clathrochelate polymers in iodine capture. Full article

(This article belongs to the Special Issue Synthesis, Processing, Structure and Properties of Polymer Materials II)

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Review

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35 pages, 9944 KiB

Open AccessReview

Process Design and Parameters Interaction in Material Extrusion 3D Printing: A Review

by Ouri Bouzaglou, Ofek Golan and Noa Lachman

Polymers 2023, 15(10), 2280; https://doi.org/10.3390/polym15102280 - 12 May 2023

Cited by 9 | Viewed by 2265

Abstract

Additive Manufacturing (AM), commonly known as “3D printing”, is rapidly integrated into many various fields, from everyday commercial to high-end medical and aerospace. Its production flexibility in small-scale and complex shapes is a significant advantage over conventional methods. However, inferior physical properties of [...] Read more.

Additive Manufacturing (AM), commonly known as “3D printing”, is rapidly integrated into many various fields, from everyday commercial to high-end medical and aerospace. Its production flexibility in small-scale and complex shapes is a significant advantage over conventional methods. However, inferior physical properties of parts manufactured by AM in general, and by material extrusion in particular, compared to traditional fabrication methods, inhibit its full assimilation. Specifically, the mechanical properties of printed parts are not high enough and, more importantly, not consistent enough. Optimization of the many various printing parameters is therefore required. This work reviews the influence of material selection, printing parameters such as path (e.g., layer thickness and raster angle), build (e.g., infill and building orientation) and temperature parameters (e.g., nozzle or platform temperature) on mechanical properties. Moreover, this work focuses on the interactions between the printing parameters, their mechanisms, and the statistical methods required to identify such interactions. Choosing the right parameters can increase mechanical properties by up to 60% (raster angle and orientation build), or render other parameters insignificant (material selection), while specific settings of certain parameters can completely inverse the influence trend of other parameters. Finally, trends for future research are suggested. Full article

(This article belongs to the Special Issue Synthesis, Processing, Structure and Properties of Polymer Materials II)

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29 pages, 5760 KiB

Open AccessReview

Polymerization within Nanoporous Anodized Alumina Oxide Templates (AAO): A Critical Survey

by Carmen Mijangos and Jaime Martin

Polymers 2023, 15(3), 525; https://doi.org/10.3390/polym15030525 - 19 Jan 2023

Cited by 3 | Viewed by 2212

Abstract

In the last few years, the polymerization of monomers within the nanocavities of porous materials has been thoroughly studied and developed, allowing for the synthesis of polymers with tailored morphologies, chemical architectures and functionalities. This is thus a subject of paramount scientific and [...] Read more.

In the last few years, the polymerization of monomers within the nanocavities of porous materials has been thoroughly studied and developed, allowing for the synthesis of polymers with tailored morphologies, chemical architectures and functionalities. This is thus a subject of paramount scientific and technological relevance, which, however, has not previously been analyzed from a general perspective. The present overview reports the state of the art on polymerization reactions in spatial confinement within porous materials, focusing on the use of anodized aluminum oxide (AAO) templates. It includes the description of the AAO templates used as nanoreactors. The polymerization reactions are categorized based on the polymerization mechanism. Amongst others, this includes electrochemical polymerization, free radical polymerization, step polymerization and atom transfer radical polymerization (ATRP). For each polymerization mechanism, a further subdivision is made based on the nature of the monomer used. Other aspects of “in situ” polymerization reactions in restricted AAO geometries include: conversion monitoring, kinetic studies, modeling and polymer characterization. In addition to the description of the polymerization process itself, the use of polymer materials derived from polymerization in AAO templates in nanotechnology applications, is also highlighted. Finally, the review is concluded with a general discussion outlining the challenges that remain in the field. Full article

(This article belongs to the Special Issue Synthesis, Processing, Structure and Properties of Polymer Materials II)

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23 pages, 4204 KiB

Open AccessReview

Recent Advances in the Enzymatic Synthesis of Polyester

by Hong Wang, Hongpeng Li, Chee Keong Lee, Noreen Suliani Mat Nanyan and Guan Seng Tay

Polymers 2022, 14(23), 5059; https://doi.org/10.3390/polym14235059 - 22 Nov 2022

Cited by 6 | Viewed by 2268

Abstract

Polyester is a kind of polymer composed of ester bond-linked polybasic acids and polyol. This type of polymer has a wide range of applications in various industries, such as automotive, furniture, coatings, packaging, and biomedical. The traditional process of synthesizing polyester mainly uses [...] Read more.

Polyester is a kind of polymer composed of ester bond-linked polybasic acids and polyol. This type of polymer has a wide range of applications in various industries, such as automotive, furniture, coatings, packaging, and biomedical. The traditional process of synthesizing polyester mainly uses metal catalyst polymerization under high-temperature. This condition may have problems with metal residue and undesired side reactions. As an alternative, enzyme-catalyzed polymerization is evolving rapidly due to the metal-free residue, satisfactory biocompatibility, and mild reaction conditions. This article presented the reaction modes of enzyme-catalyzed ring-opening polymerization and enzyme-catalyzed polycondensation and their combinations, respectively. In addition, the article also summarized how lipase-catalyzed the polymerization of polyester, which includes (i) the distinctive features of lipase, (ii) the lipase-catalyzed polymerization and its mechanism, and (iii) the lipase stability under organic solvent and high-temperature conditions. In addition, this article also focused on the advantages and disadvantages of enzyme-catalyzed polyester synthesis under different solvent systems, including organic solvent systems, solvent-free systems, and green solvent systems. The challenges of enzyme optimization and process equipment innovation for further industrialization of enzyme-catalyzed polyester synthesis were also discussed in this article. Full article

(This article belongs to the Special Issue Synthesis, Processing, Structure and Properties of Polymer Materials II)

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