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Structure-Property Relationship of Polymer Materials

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A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Analysis and Characterization".

Deadline for manuscript submissions: closed (20 September 2022) | Viewed by 32916

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Prof. Dr. Byoung-Ho Choi

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Advanced Materials Characterization Laboratory, School of Mechanical Engineering, Korea University, Seoul 02841, Korea
Interests: material degradation; fracture mechanics; material durability; structure-property relationship; damage mechanics; composite materials; multiphysics and multiscale analysis
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Dear Colleagues,

Recently, various functional polymer materials have been developed, and the application fields of the developed polymer materials have been continuously expanding. It is well-known that various properties can be obtained once the structure of the polymer material is changed, so it is quite important to investigate the fundamental molecular structural and morphological features of polymer materials, which control many of their commercially interesting properties. Accordingly, when developing a polymer material, it must be able to respond to various customer needs and criteria, such as electrical, mechanical, physical, and chemical properties related to the structure of polymer materials.

The important aim of this Special Issue is to investigate the fundamentals of structure–property relationships of polymer materials for sustainable industrial applications. Therefore, this Special Issue has importance, not only for academic institutions such as universities and research institutes, but also for industries, which can provide interesting contributions. We hope that many enthusiastic and renowned researchers in related fields will have active interest and participation in this Special Issue.

Prof. Dr. Byoung-Ho Choi
Guest Editor

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Keywords

functional polymer materials
mechanical properties
electrical properties
physical properties
chemical properties
polymer chain structure
polymer crystal structure

Published Papers (12 papers)

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Research

14 pages, 24748 KiB

Open AccessArticle

The Effects of rGO Content and Drying Method on the Textural, Mechanical, and Thermal Properties of rGO/Polymer Composites

by Jelena D. Jovanovic, Stevan N. Blagojevic and Borivoj K. Adnadjevic

Polymers 2023, 15(5), 1287; https://doi.org/10.3390/polym15051287 - 03 Mar 2023

Viewed by 1096

Abstract

Composite hydrogels samples consisting of poly(methyl methacrylate/butyl acrylate/2-hydroxyethylmethacrylate) (poly-OH) and up to 60% reduced graphene oxide (rGO) containing rGO were synthesized. The method of coupled thermally induced self-assembly of graphene oxide (GO) platelets within a polymer matrix and in situ chemical reduction of GO was applied. The synthesized hydrogels were dried using the ambient pressure drying (APD) and freeze-drying (FD) methods. The effects of the weight fraction of rGO in the composites and the drying method on the textural, morphological, thermal, and rheological properties were examined for the dried samples. The obtained results indicate that APD leads to the formation of non-porous xerogels (X) of high bulk density (D), while FD results in the formation of highly porous aerogels (A) with low D. An increase in the weight fraction of rGO in the composite xerogels leads to an increase in D, specific surface area (SA), pore volume (Vp), average pore diameter (dp), and porosity (P). With an increase in the weight fraction of rGO in A-composites, the D values increase while the values of SP, Vp, dp, and P decrease. Thermo-degradation (TD) of both X and A composites takes place through three distinct steps: dehydration, decomposition of residual oxygen functional group, and polymer chain degradation. The thermal stabilities (TS) of the X-composites and X-rGO are higher than those of the A-composites and A-rGO. The values of the storage modulus (E’) and the loss modulus (E”) of the A-composites increase with the increase in their weight fraction of rGO. Full article

(This article belongs to the Special Issue Structure-Property Relationship of Polymer Materials)

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15 pages, 4195 KiB

Open AccessArticle

Microstructure and Mechanical Properties of Severely Deformed Polypropylene in ECAE (Equal Channel Angular Extrusion) via Routes A and C

by Qifeng Jiang, Ramdane Boulahia, Fahmi Zaïri, Iurii Vozniak, Zhengwei Qu, Jean-Michel Gloaguen and Xiaobing Liu

Polymers 2022, 14(23), 5287; https://doi.org/10.3390/polym14235287 - 03 Dec 2022

Cited by 1 | Viewed by 1070

Abstract

Equal channel angular extrusion (ECAE) is a solid-state extrusion process for modifying microstructures via severe plastic deformation without modifying the specimen cross section. In this study, changes in the microstructure and mechanical properties of polypropylene resulting from extrusion orientation route A (no rotation between extrusions) and extrusion orientation route C (a rotation of 180° between extrusions) are investigated using a 90° die-angle tooling outfitted with back pressure. Important differences are reported for the ECAE-induced deformation behavior between the two processing routes. A focus is made on the occurrence of heterogeneous plastic deformations (periodic shear banding and warping) for both routes and the control and inhibition of the plastic instabilities via regulated back pressure and ram velocity. Wide-angle X-ray scattering is carried out to characterize the structural evolution as a function of the processing conditions including route, extrusion velocity and BP application. The mechanical properties of the specimens machined from the ECAE pieces are examined under different loading paths including uniaxial tension/compression and simple shear. Full-field displacements converted to volumetric strains revealed the profound impacts of the processing route on the deformation mechanisms during tensile deformation. Full article

(This article belongs to the Special Issue Structure-Property Relationship of Polymer Materials)

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18 pages, 3113 KiB

Open AccessArticle

Design of Acrylate-Terminated Polyurethane for Nylon Seamless Bonding Fabric Part I: Design of the End-Capping Thermoplastic Polyurethane Adhesive with Acrylate Copolymer

by Jiong-Bo Chen, Sheng-Yu Lin, Naveed Ahmad and Chung-Feng Jeffrey Kuo

Polymers 2022, 14(19), 4079; https://doi.org/10.3390/polym14194079 - 28 Sep 2022

Cited by 1 | Viewed by 1681

Abstract

This series of studies aims to design acrylate-terminated polyurethanes for use in nylon seamless bonded fabrics. The first part used N,N-dimethylacrylamide (DMAA) and methyl methacrylate (MMA) to replace the chain extender in polyurethane synthesis as end-capping agent to synthesize thermoplastic polyurethane (TPU) adhesive. The molecular weight of the TPU is controlled to further influence the mechanical and processing properties of the polyurethane. Here, polytetramethylene ether glycol (PTMG) and 4,4-methylene diphenyl diisocyanate (MDI) were polymerized, and then a blocking agent was added thereto. The results show that the characteristic peaks of benzene ring and carbamate of TPU adhesive are at 1596 cm⁻¹ and 1413 cm⁻¹, respectively, while the characteristic peaks of DMAA are at 1644 cm⁻¹ and 1642 cm⁻¹ in the FT-IR spectrum. There is an absorption peak –N=C=O– which is not shown near 2268 cm⁻¹, which proves that the structure of TPU contains the molecular structure of capping agent, PTMG and MDI. When the DMAA concentration in the capping agent was increased from 3.0 wt% to 10 wt%, the –C=O (H-bond) area percentage of hydrogen bonds formed at 1711 cm⁻¹ increased from 41.7% to 57.6%, while the –NH (H bond) produced at 3330 cm⁻¹ increased from 70% to 81%. These phenomena suggest that increasing the concentration of DMAA capping agent can effectively promote the formation of complex supramolecular network structures by hydrogen bonding in TPU. The content and concentration of the capping agent affects the molecular weight of the TPU. Chain growth is terminated when molecular weight growth can be effectively controlled and reduced. It was observed in thermal analysis that with increasing DMAA concentration in the molecular structure, the concentration of capping agent in TPU, hydrogen bonding force between hard segments, melting point (Tmh) and melting enthalpy (ΔH) all increased the capping agent. The pyrolysis temperature of TPU is increased by 10–20 °C. Full article

(This article belongs to the Special Issue Structure-Property Relationship of Polymer Materials)

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20 pages, 6258 KiB

Open AccessEditor’s ChoiceArticle

The Effect of Physical Aging and Degradation on the Re-Use of Polyamide 12 in Powder Bed Fusion

by Benjamin Sanders, Edward Cant, Hoda Amel and Michael Jenkins

Polymers 2022, 14(13), 2682; https://doi.org/10.3390/polym14132682 - 30 Jun 2022

Cited by 11 | Viewed by 3336

Abstract

Powder bed fusion (PBF) is an additive manufacturing (AM) technique which offers efficient part-production, light-weighting, and the ability to create complex geometries. However, during a build cycle, multiple aging and degradation processes occur which may affect the reusability of the Polyamide 12 (PA-12) powder. Limited understanding of these phenomena can result in discarding re-usable powder unnecessarily, or the production of parts with insufficient properties, both of which lead to significant amounts of waste. This paper examines the thermal, chemical, and mechanical characteristics of PA-12 via an oven storage experiment that simulates multi jet fusion (MJF) conditions. Changes in the properties of PA-12 powder during oven storage showed two separate, time-dependent trends. Initially, differential scanning calorimetry showed a 4.2 °C increase in melting temperature (T_m) and a rise in crystallinity (X_c). This suggests that secondary crystallisation is occurring instead of, or in addition to, the more commonly reported further polycondensation process. However, with extended storage time, there were substantial reductions in T_m and X_c, whilst an 11.6 °C decrease in crystallisation temperature was observed. Fourier transform infrared spectroscopy, a technique rarely used in PBF literature, shows an increased presence of imide bonds—a key marker of thermo-oxidative degradation. Discolouration of samples, an 81% reduction in strength and severe material embrittlement provided further evidence that thermo-oxidative degradation becomes the dominant process following extended storage times beyond 100 h. An additional pre-drying experiment showed how moisture present within PA-12 can also accelerate degradation via hydrolysis. Full article

(This article belongs to the Special Issue Structure-Property Relationship of Polymer Materials)

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32 pages, 19146 KiB

Open AccessArticle

Cyclic Compression Testing of Three Elastomer Types—A Thermoplastic Vulcanizate Elastomer, a Liquid Silicone Rubber and Two Ethylene-Propylene-Diene Rubbers

by Anna-Maria Märta Ruth Persson and Erik Andreassen

Polymers 2022, 14(7), 1316; https://doi.org/10.3390/polym14071316 - 24 Mar 2022

Cited by 10 | Viewed by 6715

Abstract

Thermoplastic elastomer vulcanizate (TPV) and liquid silicone rubber (LSR) are replacement candidates for ethylene-propylene-diene rubbers (EPDM), as they offer the possibility for two-component injection moulding. In this study, these material types were compared side by side in cyclic compression tests. The materials were also characterized to provide details on the formulations. Compared to the rubbers, the TPV had higher compression set (after a given cycle) and hysteresis loss, and a stronger Mullins effect. This is due to the thermoplastic matrix in the TPV. The LSR had lower compression set (after a given cycle) than the EPDM, but stronger Mullins effect and higher relative hysteresis loss. These differences between the LSR and the EPDM are likely due to differences in polymer network structure and type of filler. Methods for quantifying the Mullins effect are proposed, and correlations between a Mullins index and parameters such as compression set are discussed. The EPDMs showed a distinct trend in compression set, relative hysteresis loss and relaxed stress fraction vs. strain amplitude; these entities were almost independent of strain amplitude in the range 15–35%, while they increased in this range for the TPV and the LSR. The difference between the compression set values of the LSR and the EPDM decreased with increasing strain amplitude and increasing strain recovery time. Full article

(This article belongs to the Special Issue Structure-Property Relationship of Polymer Materials)

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23 pages, 9496 KiB

Open AccessArticle

Tapered Waist Tensile Specimens for Evaluating Butt Fusion Joints of Polyethylene Pipes—Part 1: Development

by Sunwoo Kim, Taemin Eom, Wonjae Lee and Sunwoong Choi

Polymers 2022, 14(6), 1187; https://doi.org/10.3390/polym14061187 - 16 Mar 2022

Viewed by 2122

Abstract

The structural integrity of butt fusion (BF) joints in thermoplastic pressure piping systems is critical to their long-term safe use. The tapered waist tensile (TWT) specimen was developed to alleviate issues associated with ISO 13953 waisted tensile (WT) specimen for evaluating BF joints. Experimental and finite element analyses were performed to obtain optimum TWT specimen designs for the BF joint destructive test. For TWT specimens, depending on the pipe size, the displacement at onset necking was reduced by 30~100%, and the tested BF area increased by 60~80% compared to the WT specimen. In addition, the transverse specimen deflection was lower thus providing better experimental stability. Furthermore, it showed the same BF displacement at the maximum force local to the BF bead, indicating that the tapered waist geometry provides equivalent deformation constraint and BF failure mode designed for the BF joint in the WT specimens. Therefore, TWT specimens offer simplicity, adaptability, stability, and accuracy in specimen preparation, testing, and analysis compared to WT specimens. Full article

(This article belongs to the Special Issue Structure-Property Relationship of Polymer Materials)

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15 pages, 12224 KiB

Open AccessArticle

Effect of Functional Fillers on Tribological Characteristics of Acrylonitrile Butadiene Rubber after High-Pressure Hydrogen Exposures

by Byeong-Lyul Choi, Jae Kap Jung, Un Bong Baek and Byoung-Ho Choi

Polymers 2022, 14(5), 861; https://doi.org/10.3390/polym14050861 - 22 Feb 2022

Cited by 8 | Viewed by 1852

Abstract

In a high-pressure hydrogen environment, the sealing rubber material is swelled by hydrogen, and the mechanical and tribological properties are reduced, causing various problems in the sealing performance. The focus of this study was the effect of the filler type and content on the tribological characteristics of rubber after exposure to high-pressure hydrogen. Acrylonitrile butadiene rubber specimens were exposed to high-pressure hydrogen at 96.6 MPa, and the change in the amount of wear with time after exposure was observed. The wear test was performed using a pin-on-disc ball tip to measure the amount of wear before and after hydrogen exposure of the materials under fixed revolutions per minute and normal load. Scanning electron microscopy was used to observe the wear track and cross section of the specimen to examine the changes in the wear mechanism after hydrogen exposure and to analyze the wear mechanism for each filler. The results of this study are expected to contribute to the evaluation of the tribological properties of the sealing materials used in hydrogen environments. Full article

(This article belongs to the Special Issue Structure-Property Relationship of Polymer Materials)

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23 pages, 11313 KiB

Open AccessArticle

Analysis of Mechanical Property Degradation of Outdoor Weather-Exposed Polymers

by Sunwoo Kim, Youngmin Lee, Changhwan Kim and Sunwoong Choi

Polymers 2022, 14(2), 357; https://doi.org/10.3390/polym14020357 - 17 Jan 2022

Cited by 7 | Viewed by 2833

Abstract

It is well known that many polymers are prone to outdoor weathering degradation. Therefore, to ensure the safety and integrity of the structural parts and components made from polymers for outdoor use, their weather-affected mechanical behavior needs to be better understood. In this study, the critical mechanical property for degradation was identified and modeled into a usable format for use in the virtual analysis. To achieve this, an extensive 4-year outdoor weathering test was carried out on polycarbonate (PC), polypropylene (PP), polybutylene terephthalate (PBT), and high-density polyethylene (HDPE) polymers up to a total UV irradiation of 1020 MJ/m² at a 315~400 nm wavelength. In addition, tensile tests were performed by collecting five specimens for each material at every 60 MJ/m² interval. With the identification of fracture strain retention as the key performance index for mechanical property degradation, a fracture strain retention function was developed using logistic regression analysis for each polymer. In addition, a method for using fracture strain retention function to establish a mechanical property degradation dataset was proposed and successfully tested by performing weathering FE analysis on the virtual automotive collision behavior of a PC part under intermittent UV irradiation doses. This work showed the potential of using fracture strain retention function to predict the performance of polymeric components undergoing mechanical property degradation upon outdoor weathering. Full article

(This article belongs to the Special Issue Structure-Property Relationship of Polymer Materials)

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14 pages, 6714 KiB

Open AccessArticle

Scratch Properties of Clear Coat for Automotive Coating Comprising Molecular Necklace Crosslinkers with Silane Functional Groups for Various Environmental Factors

by Sung Wook Moon, Jiae Seo, Ji-Hun Seo and Byoung-Ho Choi

Polymers 2021, 13(22), 3933; https://doi.org/10.3390/polym13223933 - 14 Nov 2021

Cited by 5 | Viewed by 2713

Abstract

Automotive coatings, which comprise multiple layers, i.e., primer, base coating, and clear coat layers, are exposed to various environmental conditions that pose various types of damages to them. In particular, the outer layer of the automotive coating, i.e., the clear coat, is affected significantly by such damages. Therefore, a reliable and durable clear coat must be developed to improve the appearance of automobiles. In this study, a new clear coat based on an acrylic-based clear coat modified using polyrotaxane crosslinkers, which are necklace-shaped supramolecules composed of ring-shaped host molecules, is developed and characterized. The effects of polyrotaxane and silane on the scratch properties and mechanisms of the clear coating are analyzed. It is observed that the critical loads of the clear coat from scratch tests can be improved by adding optimal molecular necklace crosslinkers comprising silane functional groups. The improvement in the scratch properties of the modified acrylic-based clear coat may be attributed to the crosslinking characteristics and dynamic molecular movements of the polyrotaxane. In addition, the effects of environmental factors on the scratch characteristics of the modified acrylic-based clear coat are investigated by addressing the scratch durability of the clear coat. Full article

(This article belongs to the Special Issue Structure-Property Relationship of Polymer Materials)

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16 pages, 7288 KiB

Open AccessArticle

Crash Analysis of Aluminum/CFRP Hybrid Adhesive Joint Parts Using Adhesive Modeling Technique Based on the Fracture Mechanics

by Young Cheol Kim, Soon Ho Yoon, Geunsu Joo, Hong-Kyu Jang, Ji-Hoon Kim, Mungyu Jeong and Ji Hoon Kim

Polymers 2021, 13(19), 3364; https://doi.org/10.3390/polym13193364 - 30 Sep 2021

Cited by 5 | Viewed by 2086

Abstract

This study describes the numerical simulation results of aluminum/carbon-fiber-reinforced plastic (CFRP) hybrid joint parts using the explicit finite-element solver LS-DYNA, with a focus on capturing the failure behavior of composite laminates as well as the adhesive capacity of the aluminum–composite interface. In this study, two types of adhesive modeling techniques were investigated: a tiebreak contact condition and a cohesive zone model. Adhesive modeling techniques have been adopted as a widely commercialized model of structural adhesives to simulate adhesive failure based on fracture mechanics. CFRP was studied with numerical simulations utilizing LS-DYNA MAT54 to analyze the crash capability of aluminum/CFRP. To evaluate the simulation model, the results were compared with the force–displacement curve from numerical analysis and experimental results. A parametric study was conducted to evaluate the effect of different fracture toughness values used by designers to predict crash capability and adhesive failure of aluminum/CFRP parts. Full article

(This article belongs to the Special Issue Structure-Property Relationship of Polymer Materials)

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25 pages, 8183 KiB

Open AccessArticle

Structural and Viscoelastic Properties of Thermoplastic Polyurethanes Containing Mixed Soft Segments with Potential Application as Pressure Sensitive Adhesives

by Mónica Fuensanta and José Miguel Martín-Martínez

Polymers 2021, 13(18), 3097; https://doi.org/10.3390/polym13183097 - 14 Sep 2021

Cited by 9 | Viewed by 2866

Abstract

Thermoplastic polyurethanes (TPUs) were synthetized with blends of poly(propylene glycol) (PPG) and poly(1,4-butylene adipate) (PAd) polyols, diphenylmethane-4,4′-diisocyanate (MDI) and 1,4-butanediol (BD) chain extender; different NCO/OH ratios were used. The structure and viscoelastic properties of the TPUs were assessed by infrared spectroscopy, differential scanning calorimetry, X-ray diffraction, thermal gravimetric analysis and plate-plate rheology, and their pressure sensitive adhesion properties were assessed by probe tack and 180° peel tests. The incompatibility of the PPG and PAd soft segments and the segregation of the hard and soft segments determined the phase separation and the viscoelastic properties of the TPUs. On the other hand, the increase of the NCO/OH ratio improved the miscibility of the PPG and PAd soft segments and decreased the extent of phase separation. The temperatures of the cool crystallization and melting were lower and their enthalpies were higher in the TPU made with NCO/OH ratio of 1.20. The moduli of the TPUs increased by increasing the NCO/OH ratio, and the tack was higher by decreasing the NCO/OH ratio. In general, a good agreement between the predicted and experimental tack and 180° peel strength values was obtained, and the TPUs synthesized with PPG+PAd soft segments had potential application as pressure sensitive adhesives (PSAs). Full article

(This article belongs to the Special Issue Structure-Property Relationship of Polymer Materials)

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16 pages, 3507 KiB

Open AccessArticle

Composites of a Polypropylene Random Copolymer and Date Stone Flour: Crystalline Details and Mechanical Response

by Amina Benarab, Enrique Blázquez-Blázquez, Rachida Krache, Rosario Benavente, María L. Cerrada and Ernesto Pérez

Polymers 2021, 13(17), 2957; https://doi.org/10.3390/polym13172957 - 31 Aug 2021

Cited by 2 | Viewed by 2390

Abstract

Several composites were prepared based on a polypropylene random copolymer (PPR) and different amounts of date stone flour (DSF). This cellulosic fiber was silanized beforehand in order to reduce its hydrophilicity and improve the interfacial adhesion with the polymer. Other composites were also obtained, including a sorbitol derivative as an effective nucleant. Films made from these composites were prepared using two different thermal treatments, involving slow crystallization and rapid cooling from the melt. Scanning electron microscopy was used to evaluate the morphological features and the DSF particle dispersion within the PPR matrix. X-ray diffraction experiments and differential scanning calorimetry tests were employed to assess the crystalline characteristics and for the phase transitions, paying especial attention to the effects of the DSF and nucleating agent on PPR crystallization. An important nucleation ability was found for DSF, and evidently for the sorbitol derivative. The peak crystallization temperature upon cooling was considerably increased by the incorporation of either the nucleant or DSF. Additionally, a much higher proportion of orthorhombic crystals developed in relation to the monoclinic ones. Moreover, the mechanical responses were estimated from the microhardness experiments and significant improvements were found with increasing DSF contents. All of these findings indicate that the use of silanized DSF is a fairly good approach for the preparation of polymeric eco-composites, taking advantage of the widespread availability of this lignocellulosic material, which is otherwise wasted. Full article

(This article belongs to the Special Issue Structure-Property Relationship of Polymer Materials)

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