Polymers

Research

13 pages, 5053 KiB

Open AccessArticle

Experimental Research of Abnormal Wear for Water-Lubricated Polymer Bearings under Low Speed, Heavy Pressure, and High Water Temperature

by Ying Liu, Gengyuan Gao and Dan Jiang

Polymers 2023, 15(5), 1227; https://doi.org/10.3390/polym15051227 - 28 Feb 2023

Cited by 1 | Viewed by 1054

Abstract

Polymer bearings used in a real ship had a hydrolysis failure under 50 rpm at 0.5 MPa with 40 °C water temperature. The test conditions were determined based on the operating conditions of the real ship. The test equipment was rebuilt to accommodate [...] Read more.

Polymer bearings used in a real ship had a hydrolysis failure under 50 rpm at 0.5 MPa with 40 °C water temperature. The test conditions were determined based on the operating conditions of the real ship. The test equipment was rebuilt to accommodate bearing sizes in a real ship. Water swelling was eliminated after 6 months’ soaking. The results showed that the polymer bearing was subjected to hydrolysis because of the increased heat generation and heat dissipation deterioration under low speed, heavy pressure, and high water temperature. The wear depth in the hydrolysis area is 10 times larger than that in normal wear area, and the melting, stripping, transferring, adhering, and accumulation of hydrolyzed polymers caused abnormal wear. Additionally, extensive cracking was observed in the hydrolysis area of the polymer bearing. Full article

(This article belongs to the Special Issue Thermal Behavior of Polymer Materials)

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18 pages, 4889 KiB

Open AccessArticle

Improvement of the Thermal Stability of Polymer Bioblends by Means of Reactive Extrusion

by Félix Carrasco, Orlando Santana Pérez, Noel León Albiter and Maria Lluïsa Maspoch

Polymers 2023, 15(1), 105; https://doi.org/10.3390/polym15010105 - 27 Dec 2022

Cited by 4 | Viewed by 1703

Abstract

Poly(lactic acid) (PLA) and biosourced polyamide (PA) bioblends, with a variable PA weight content of 10–50%, were manufactured by melt blending in order to improve the behavior of PLA against thermal degradation. The effect of reactive extrusion on the thermal performance of PLA [...] Read more.

Poly(lactic acid) (PLA) and biosourced polyamide (PA) bioblends, with a variable PA weight content of 10–50%, were manufactured by melt blending in order to improve the behavior of PLA against thermal degradation. The effect of reactive extrusion on the thermal performance of PLA within bioblends was analyzed. The reactive extrusion was made by means of the addition of a styrene-acrylic multi-functional-epoxide oligomeric reactive agent (SAmfE), with the commercial name of Joncryl. Four parameters were considered in order to study the thermal behavior of bioblends against thermal decomposition: the onset decomposition temperature, the shape and temperature interval of the thermal decomposition patterns, the activation energy of the thermal decomposition, and the evidence leading to the most probable mechanism. The latter was determined by means of three evidence: standardized conversion functions, y(α) master plots, and integral mean error. It was shown that reactive extrusion of PLA as well as PA incorporation to the polymer matrix of PLA were responsible for an increase in the onset decomposition temperature of 10.4 °C. The general analytical equation (GAE) was used to evaluate the kinetic parameters of the thermal degradation of PLA within bioblends for various reaction mechanisms. It was shown that the random scission of macromolecular chains is the best mechanism for both untreated and treated PLA by means of reactive extrusion. It was shown that reactive extrusion together with higher content of PA resulted in an increased protective effect against the thermal degradation of PLA as demonstrated by an increase in activation energy of 60 kJ/mol. It was found that there is a relationship between the increase in activation energy and the increase in the onset decomposition temperature when using reactive extrusion. The improvement of the thermal stability of bioblends by means of reactive extrusion was explained by an increase in the complex viscosity from 980 to 2000 Pa·s at 0.06 rad/s and from 250 to 300 Pa·s at 630 rad/s for bioblend containing 30% of PLA_REX and by a finer dispersion of PA within the PLA_REX matrix. Results from DSC were not conclusive regarding the compatibility between both phases. Full article

(This article belongs to the Special Issue Thermal Behavior of Polymer Materials)

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18 pages, 7005 KiB

Open AccessArticle

Facile Fabrication of Superhydrophobic and Flame-Retardant Coatings on Cotton Fabrics

by Shiwei Li, Luyan Yu, Jianhua Xiong, Ying Xiong, Shuguang Bi and Heng Quan

Polymers 2022, 14(23), 5314; https://doi.org/10.3390/polym14235314 - 05 Dec 2022

Cited by 7 | Viewed by 1801

Abstract

The hydrophilicity and inherent flammability of cotton textiles severely limit their usage. To solve these drawbacks, a superhydrophobic and flame-retardant (SFR) coating made of chitosan (CH), ammonium polyphosphate (APP), and TiO₂-SiO₂-HMDS composite was applied to cotton fabric using simple [...] Read more.

The hydrophilicity and inherent flammability of cotton textiles severely limit their usage. To solve these drawbacks, a superhydrophobic and flame-retardant (SFR) coating made of chitosan (CH), ammonium polyphosphate (APP), and TiO₂-SiO₂-HMDS composite was applied to cotton fabric using simple layer-by-layer assembly and dip-coating procedures. First, the fabric was alternately immersed in CH and APP water dispersions, and then immersed in TiO₂-SiO₂-HMDS composite to form a CH/APP@TiO₂-SiO₂-HMDS coating on the cotton fabric surface. SEM, EDS, and FTIR were used to analyze the surface morphology, element composition, and functional groups of the cotton fabric, respectively. Vertical burning tests, microscale combustion calorimeter tests, and thermogravimetric analyses were used to evaluate the flammability, combustion behavior, thermal degradation characteristics, and flame-retardant mechanism of this system. When compared to the pristine cotton sample, the deposition of CH and APP enhanced the flame retardancy, residual char, heat release rate, and total heat release of the cotton textiles. The superhydrophobic test results showed that the maximal contact angle of SFR cotton fabric was 153.7°, and possessed excellent superhydrophobicity. Meanwhile, the superhydrophobicity is not lost after 10 laundering cycles or 50 friction cycles. In addition, the UPF value of CH/APP@TiO₂-SiO₂-HMDS cotton was 825.81, demonstrating excellent UV-shielding properties. Such a durable SFR fabric with a facile fabrication process exhibits potential applications for both oil/water separation and flame retardancy. Full article

(This article belongs to the Special Issue Thermal Behavior of Polymer Materials)

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23 pages, 9500 KiB

Open AccessArticle

Non-Linearity of Thermosetting Polymers’ and GRPs’ Thermal Expanding: Experimental Study and Modeling

by Alexander Korolev, Maxim Mishnev and Dmitrii Vladimirovich Ulrikh

Polymers 2022, 14(20), 4281; https://doi.org/10.3390/polym14204281 - 12 Oct 2022

Cited by 3 | Viewed by 1305

Abstract

Thermal expanding is the important property that defines the stress–strain condition of GRP structures exploited under heating and having limited thermal resistance. So, the GRPs’ thermal expanding prediction is the actual requirement of such structures design. The experimental accurate dilatometric study resulted in [...] Read more.

Thermal expanding is the important property that defines the stress–strain condition of GRP structures exploited under heating and having limited thermal resistance. So, the GRPs’ thermal expanding prediction is the actual requirement of such structures design. The experimental accurate dilatometric study resulted in the non-linearity of thermosetting polymers and plastics thermal expanding under heating. The polymers and plastics thermal expanding coefficient (CTE) is non-linearly increasing under heating before glassing temperature (Tg). Using the previous polymers and GRPs modelling experience and experimental dilatometric results, the non-linear adequate prediction models of their CTE were proposed and proved. The new compensative wave model of polymers’ CTE and multi-layer model of GRPs’ CTE were proposed and successfully tested. A prediction of the temperature dependences of the thermal expansion coefficients of various thermoset polymer binders and data on the reinforcement structure was performed based on the experimentally obtained temperature dependences of the CTEs of GRPs. The prediction was performed using the finite-element homogenization method in the Material Designer module of the academic version of the Ansys package. A satisfactory concurrence of the numerical results of the prognosis and the experiment for all considered cases is observed in the temperature range from 50 to 100 °C, after glass transition temperature best coincidence of numerical values of CTE is obtained for glass-reinforced plastics on epoxy resin, which were not subjected to thermal aging. Full article

(This article belongs to the Special Issue Thermal Behavior of Polymer Materials)

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12 pages, 3479 KiB

Open AccessArticle

Curing Kinetics of Methylene Diphenyl Diisocyanate—Based Polyurethane Elastomers

by Shuang Liu, Xiaodong Li, Mengchen Ge, Xujie Du and Meishuai Zou

Polymers 2022, 14(17), 3525; https://doi.org/10.3390/polym14173525 - 27 Aug 2022

Cited by 1 | Viewed by 1798

Abstract

The curing kinetics of MDI-based polyurethane elastomers were studied by non-isothermal differential scanning calorimetry (DSC). The kinetic parameters of the reaction system were calculated by the Kissinger method. The changing activation energy was observed by the Flynn–Wall–Ozawa method and the Friedman method. The [...] Read more.

The curing kinetics of MDI-based polyurethane elastomers were studied by non-isothermal differential scanning calorimetry (DSC). The kinetic parameters of the reaction system were calculated by the Kissinger method. The changing activation energy was observed by the Flynn–Wall–Ozawa method and the Friedman method. The results of model free fitting showed that the curing reaction could be divided into two stages, showing a change in reaction order when α > 0.45 and a piecewise curing mechanism function of the MDI-based polyurethane elastomers reaction system was deduced by autocatalytic model. The extrapolation method was used to determine the optimum curing conditions for the system, which can accurately describe the curing process. In addition, the optimal curing conditions are when: the constant temperature curing temperature of the system is 81 °C, the curing time is 29 min, and the post-curing temperature is 203 °C. Full article

(This article belongs to the Special Issue Thermal Behavior of Polymer Materials)

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19 pages, 4985 KiB

Open AccessArticle

High-Performance Optical PET Analysis via Non-Isothermal Crystallization Kinetics

by Dezhi Qu, Jiayang Cai, Fei Huang, Jinyu Zhang, Huajiang Zuo, Shuai Sun, Jinghua Liu and Yongping Bai

Polymers 2022, 14(15), 3044; https://doi.org/10.3390/polym14153044 - 27 Jul 2022

Cited by 4 | Viewed by 1594

Abstract

The optical properties of PET have always been a problem that related research has been trying to break through. In the previous work, we modified PET by adding PSLDH (phosphate antioxidant) to obtain a PET film with excellent optical properties. Through non-isothermal crystallization [...] Read more.

The optical properties of PET have always been a problem that related research has been trying to break through. In the previous work, we modified PET by adding PSLDH (phosphate antioxidant) to obtain a PET film with excellent optical properties. Through non-isothermal crystallization kinetic analysis of modified PET, we hope to verify the conclusion of optical properties by the effect of PSLDH addition on the crystallization properties of PET. PET and PSLDH modified PET were tested by DSC at different cooling rates. The non-isothermal crystallization kinetic process was calculated and analyzed by Jeziorny and Mo methods and the non-isothermal crystallization activation energy was analyzed by Kissinger and Friedman methods by analyzing the DSC curves. The results show that the addition of PSLDH at 0.05 wt% can make the crystallization of PET smaller and slower, which is the same as the case required for excellent optical properties. At the same time, the results can also guide the processing of the optical PET film. Full article

(This article belongs to the Special Issue Thermal Behavior of Polymer Materials)

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13 pages, 3388 KiB

Open AccessArticle

Thermal Diffusivity and Conductivity of Polyolefins by Thermal Lens Technique

by Behnaz Abbasgholi-NA, Seyed Reza Nokhbeh, Osamah A. Aldaghri, Khalid Hassan Ibnaouf, Nawal Madkhali and Humberto Cabrera

Polymers 2022, 14(13), 2707; https://doi.org/10.3390/polym14132707 - 01 Jul 2022

Cited by 5 | Viewed by 2142

Abstract

A mode-mismatched thermal lens spectrometry (TLS) technique, in a pump–probe two-laser-beam configuration, was employed for the experimental determination of the thermal properties of four selected well-characterized polyolefin homopolymer films. We investigated the thermal diffusivity (D) and thermal conductivity (κ) of high-density polyethylene, low-density [...] Read more.

A mode-mismatched thermal lens spectrometry (TLS) technique, in a pump–probe two-laser-beam configuration, was employed for the experimental determination of the thermal properties of four selected well-characterized polyolefin homopolymer films. We investigated the thermal diffusivity (D) and thermal conductivity (κ) of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and polypropylene. We also measured the structural properties (i.e., average molecular weight, polydispersity index, branching number), along with the rheological and thermal properties (i.e., melting point, specific heat capacity Cp, degree of crystallinity) of samples by high-temperature gel permeation chromatography (HT-GPC), rheometric mechanical spectrometry (RMS), differential scanning calorimetry (DSC), and densitometry. The relationship between microstructural properties such as degree of crystallinity, D, and κ was investigated. The results show that there is good correlation between the degree of crystallinity and D. The TL technique enables measurement of D in semitransparent thin films within an uncertainty of 4%. Full article

(This article belongs to the Special Issue Thermal Behavior of Polymer Materials)

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13 pages, 4210 KiB

Open AccessArticle

Laser Ablation Mechanism and Performance of Carbon Fiber-Reinforced Poly Aryl Ether Ketone (PAEK) Composites

by Jindong Zhang, Ran Bi, Shengda Jiang, Zihao Wen, Chuyang Luo, Jianan Yao, Gang Liu, Chunhai Chen and Ming Wang

Polymers 2022, 14(13), 2676; https://doi.org/10.3390/polym14132676 - 30 Jun 2022

Cited by 3 | Viewed by 4819

Abstract

The ablation mechanism and performance of carbon fiber (CF)-reinforced poly aryl ether ketone (PAEK) thermoplastic composites were studied in this paper. The results show that the ablation damaged area is controlled by the irradiation energy, while the mass loss rate is controlled by [...] Read more.

The ablation mechanism and performance of carbon fiber (CF)-reinforced poly aryl ether ketone (PAEK) thermoplastic composites were studied in this paper. The results show that the ablation damaged area is controlled by the irradiation energy, while the mass loss rate is controlled by the irradiation power density. In the ablation center, the PAEK resin and CFs underwent decomposition and sublimation in an anaerobic environment. In the transition zone, the resin experienced decomposition and remelting in an aerobic environment, and massive char leaves were present in the cross section. In the heat-affected zone, only remelting of the resin was observed. The fusion and decomposition of the resin caused delamination and pores in the composites. Moreover, oxygen appeared crucial to the ablation morphology of CFs. In an aerobic environment, a regular cross section formed, while in an anaerobic environment, a cortex–core structure formed. The cortex–core structure of CF inside the ablation pit was caused by the inhomogeneity of fibers along the radial direction and the residual carbon layer generated by resin decomposition in an anoxic environment. The description of the ablation mechanism presented in this study broadens our understanding of damage evolution in thermoplastic composites subjected to high-energy CW laser irradiation. Full article

(This article belongs to the Special Issue Thermal Behavior of Polymer Materials)

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13 pages, 6759 KiB

Open AccessArticle

Interlaminar Mechanical Properties and Toughening Mechanism of Highly Thermally Stable Composite Modified by Polyacrylonitrile Nanofiber Films

by Yingjian Ma, Yangpeng Zhuang, Chunwei Li, Chuyang Luo and Xing Shen

Polymers 2022, 14(7), 1348; https://doi.org/10.3390/polym14071348 - 26 Mar 2022

Cited by 3 | Viewed by 4779

Abstract

This work concentrated on the interlaminar mechanical properties and toughening mechanism of carbon fiber-reinforced bismaleimide resin (CF/BMI) composites modified by polyacrylonitrile (PAN) nanofiber films. The PAN nanofiber films were prepared by electrospinning. End-notched flexure (ENF) and short-beam strength tests were conducted to assess [...] Read more.

This work concentrated on the interlaminar mechanical properties and toughening mechanism of carbon fiber-reinforced bismaleimide resin (CF/BMI) composites modified by polyacrylonitrile (PAN) nanofiber films. The PAN nanofiber films were prepared by electrospinning. End-notched flexure (ENF) and short-beam strength tests were conducted to assess the mode II fracture toughness (G_IIc) and interlaminar shear strength (ILSS). The results showed that the G_IIc and ILSS of PAN-modified specimens are 1900.4 J/m² and 93.1 MPa, which was 21.4% and 5.4% higher than that of the virgin specimens (1565.5 J/m² and 88.3 MPa), respectively. The scanning electron microscopy (SEM) images of the fracture surface revealed that the PAN nanofiber films toughen the composite on two scales. On the mesoscopic scale, the composite laminates modified by PAN formed a resin-rich layer with high strength and toughness, which made the crack propagate across the layers. At the microscopic scale, the crack propagation between two-dimensional nanofiber films led to constant pull-out and breakage of the nanofibers. As a result, the interlaminar fracture toughness of the composite laminates improved. Full article

(This article belongs to the Special Issue Thermal Behavior of Polymer Materials)

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