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14 pages, 14719 KiB

Open AccessArticle

Application and Properties of Polyglycolic Acid as a Degradation Agent in MPU/HNBR Degradable Elastomer Composites for Dissolvable Frac Plugs

by Kai Cheng, Mingyang Yuan, Yupeng Zhang, Ningjing Sun and Bo Peng

Polymers 2024, 16(2), 181; https://doi.org/10.3390/polym16020181 - 08 Jan 2024

Cited by 1 | Viewed by 719

Abstract

In this research, fully degradable elastomeric sealing materials were developed to enhance the environmental sustainability of oil and gas extraction. The modification of millable polyurethane rubber (MPU) with polyglycolic acid/hydrogenated nitrile butadiene rubber (PGA/HNBR) led to the synthesis of PGA@MPU/HNBR composite materials. The [...] Read more.

In this research, fully degradable elastomeric sealing materials were developed to enhance the environmental sustainability of oil and gas extraction. The modification of millable polyurethane rubber (MPU) with polyglycolic acid/hydrogenated nitrile butadiene rubber (PGA/HNBR) led to the synthesis of PGA@MPU/HNBR composite materials. The impact of varying monomer quantities on the mechanical properties, degradation behavior, degradation mechanisms, and thermal stability of these materials was investigated. Our findings illustrate that an increasing proportion of HNBR in the PGA@MPU/HNBR composite materials resulted in a decreased degradation rate. Simultaneously, higher HNBR content improved the thermal stability of the materials, while the inclusion of PGA reduced material hardness, rendering the composites more susceptible to swelling. At an HNBR content of 40 phr, MPU at 60 phr, and PGA at 6 phr, the composite material demonstrated the highest retention of mechanical properties at 31.3% following 168 h of hydrolysis at 100 °C. The degradation of the composite materials in 100 °C water primarily resulted from the hydrolysis of MPU’s ester groups, with HNBR remaining unaffected. Full article

(This article belongs to the Special Issue Degradation and Stability of Polymer Based Systems)

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15 pages, 5616 KiB

Open AccessArticle

The Interplay of Protein Hydrolysis and Ammonia in the Stability of Hevea Rubber Latex during Storage

by Narueporn Payungwong, Jitladda Sakdapipanich, Jinrong Wu and Chee-Cheong Ho

Polymers 2023, 15(24), 4636; https://doi.org/10.3390/polym15244636 - 07 Dec 2023

Viewed by 1020

Abstract

Natural rubber (NR) latex derived from Hevea brasiliensis is a complex colloid comprising mainly rubber hydrocarbons (latex particles) and a multitude of minor non-rubber constituents such as non-rubber particles, proteins, lipids, carbohydrates, and soluble organic and inorganic substances. NR latex is susceptible to [...] Read more.

Natural rubber (NR) latex derived from Hevea brasiliensis is a complex colloid comprising mainly rubber hydrocarbons (latex particles) and a multitude of minor non-rubber constituents such as non-rubber particles, proteins, lipids, carbohydrates, and soluble organic and inorganic substances. NR latex is susceptible to enzymatic attack after it leaves the trees. It is usually preserved with ammonia and, to a lesser extent, with other preservatives to enhance its colloidal stability during storage. Despite numerous studies in the literature on the influence of rubber proteins on NR latex stability, issues regarding the effect of protein hydrolysis in the presence of ammonia on latex stability during storage are still far from resolved. The present work aims to elucidate the interplay between protein hydrolysis and ammoniation in NR latex stability. Both high- and low-ammonia (with a secondary preservative) NR latexes were used to monitor the changes in their protein compositions during storage. High-ammonia (FNR-A) latex preserved with 0.6% (v/v) ammonia, a low 0.1% ammonia/TMTD/ZnO (FNR-TZ) latex, and a deproteinized NR (PDNR) latex were labeled with fluorescence agents and observed using confocal laser scanning microscopy to determine their protein composition. Protein hydrolysis was confirmed via sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE). The results revealed that protein hydrolysis increased with the storage duration. The change in protein composition accompanying hydrolysis also allows the spatial distribution of allergenic proteins to be estimated in the latex. Concurrently, the latex stability increased with the storage duration, as measured by the latex’s mechanical stability time (MST) and the zeta potential of the latex particles. As monitored by AFM, the surface roughness of the NR latex film increased markedly during extended storage compared with that of the DPNR latex, which remained smooth. These results underscore the pivotal role of ammonia in bolstering NR latex stability brought on by protein hydrolysis, which greatly impacts latex film’s formation behavior. NR latex stability underpins the quality of latex-dipped goods during manufacturing, particularly those for medical gloves. Full article

(This article belongs to the Special Issue Degradation and Stability of Polymer Based Systems)

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16 pages, 2319 KiB

Open AccessArticle

UV Light Causes Structural Changes in Microplastics Exposed in Bio-Solids

by Somayye Sadat Alavian Petroody, Seyed Hossein Hashemi, Luka Škrlep, Branka Mušič, Cornelis A. M. van Gestel and Andrijana Sever Škapin

Polymers 2023, 15(21), 4322; https://doi.org/10.3390/polym15214322 - 04 Nov 2023

Cited by 2 | Viewed by 1830

Abstract

Bio-solids (biological sludge) from wastewater treatment plants are a significant source of the emission of microplastics (MPs) into the environment. Weakening the structure of MPs before they enter the environment may accelerate their degradation and reduce the environmental exposure time. Therefore, we studied [...] Read more.

Bio-solids (biological sludge) from wastewater treatment plants are a significant source of the emission of microplastics (MPs) into the environment. Weakening the structure of MPs before they enter the environment may accelerate their degradation and reduce the environmental exposure time. Therefore, we studied the effect of UV-A and UV-C, applied at 70 °C, on three types of MPs, polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET), that are commonly found in sewage sludge, using three shapes (fibers, lines, granules). The MPs were exposed to UV radiation in bio-solid suspensions, and to air and water as control. The structural changes in and degradation of the MPs were investigated using Attenuated Total Reflectance–Fourier Transform Infrared Spectrometry (ATR-FTIR) and surface morphology was performed with SEM analysis. UV exposure led to the emergence of carbonyl and hydroxyl groups in all of the PP samples. In PE and PET, these groups were formed only in the bio-solid suspensions. The presence of carbonyl and hydroxyl groups increased with an increasing exposure time. Overall, UV radiation had the greatest impact on the MPs in the bio-solids suspension. Due to the surface-to-volume ratio of the tested samples, which influences the degradation rate, the fibers were more degraded than the other two plastic shapes. UV-A was slightly more effective at degrading the MPs than UV-C. These findings show that ultraviolet radiation in combination with an elevated temperature affects the structure of polymers in wastewater bio-solids, which can accelerate their degradation. Full article

(This article belongs to the Special Issue Degradation and Stability of Polymer Based Systems)

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16 pages, 5279 KiB

Open AccessArticle

Preparation and Characterization of TiO₂-Coated Hollow Glass Beads for Functionalization of Deproteinized Natural Rubber Latex via UVA-Activated Photocatalytic Degradation

by Supinya Nijpanich, Adun Nimpaiboon, Porntip Rojruthai, Jae-Hyeok Park, Takeshi Hagio, Ryoichi Ichino and Jitladda Sakdapipanich

Polymers 2023, 15(19), 3885; https://doi.org/10.3390/polym15193885 - 26 Sep 2023

Viewed by 908

Abstract

The photochemical degradation of natural rubber (NR) is a prevalent method used to modify its inherent properties. Natural rubber, predominantly derived from the Hevea Brasiliensis tree, exhibits an exceptionally high molecular weight (MW), often reaching a million daltons (Da). This high MW restricts [...] Read more.

The photochemical degradation of natural rubber (NR) is a prevalent method used to modify its inherent properties. Natural rubber, predominantly derived from the Hevea Brasiliensis tree, exhibits an exceptionally high molecular weight (MW), often reaching a million daltons (Da). This high MW restricts its solubility in various solvents and its reactivity with polar compounds, thereby constraining its versatile applications. In our previous work, we employed TiO₂ in its powdered form as a photocatalyst for the functionalization of NR latex. However, the post-process separation and reuse of this powder present substantial challenges. In this present study, we aimed to functionalize deproteinized NR (DPNR) latex. We systematically reduced its MW via photochemical degradation under UVA irradiation facilitated by H₂O₂. To enhance the efficiency of the degradation process, we introduced TiO₂-coated hollow glass beads (TiO₂-HGBs) as photocatalysts. This approach offers the advantage of easy collection and repeated reuse. The modified DPNR showed a reduction in its number-average MW from 9.48 × 10⁵ to 0.28 × 10⁵ Da and incorporated functional groups, including hydroxyl, carbonyl, and epoxide. Remarkably, the TiO₂-HGBs maintained their performance over seven cycles of reuse. Due to their superior efficacy, TiO₂-HGBs stand out as promising photocatalysts for the advanced functionalization of NR across various practical applications. Full article

(This article belongs to the Special Issue Degradation and Stability of Polymer Based Systems)

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10 pages, 5511 KiB

Open AccessArticle

Natural Rigid and Hard Plastic Fabricated from Elastomeric Degradation of Natural Rubber Composite with Ultra-High Magnesium Carbonate Content

by Abedeen Dasaesamoh, Kittikhun Khotmungkhun and Kittitat Subannajui

Polymers 2023, 15(14), 3078; https://doi.org/10.3390/polym15143078 - 18 Jul 2023

Viewed by 919

Abstract

It is known that natural rubber is an elastomeric polymer; hence, the main uses are usually limited to soft applications. For the process to reverse the elastomeric effect of natural rubber to obtain rigid plastic from a natural material, an ultra-high amount of [...] Read more.

It is known that natural rubber is an elastomeric polymer; hence, the main uses are usually limited to soft applications. For the process to reverse the elastomeric effect of natural rubber to obtain rigid plastic from a natural material, an ultra-high amount of magnesium carbonate particles was added to the natural rubber to study the effect of magnesium carbonate in the reduction of elastomeric properties. High magnesium carbonate ratios of 80–180 phr were mixed in the natural rubber in the latex form to maximize the mixing capability since it was more difficult to achieve these mixture ratios with only two roll mill or extruder processes. The more magnesium carbonate powders in the composite, the higher torques were measured from the moving die rheometer (MDR) test. The powder was thoroughly mixed inside the composite, which was observed from energy-dispersive X-ray spectrometer (EDX) mapping; however, the matrix of composites was filled with porosity due to the CO₂ formation when latex with magnesium carbonate was assimilated with acid during the vulcanization process. The strength of the composite dropped, and the elongations were shortened. On the other hand, the hardness of composites was drastically increased. The composite lost the elastomeric property, and the hard natural rubber composites were obtained. Full article

(This article belongs to the Special Issue Degradation and Stability of Polymer Based Systems)

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14 pages, 6976 KiB

Open AccessArticle

Investigation on the Photodegradation Stability of Acrylic Acid-Grafted Poly(butylene carbonate-co-terephthalate)/Organically Modified Layered Zinc Phenylphosphonate Composites

by Yi-Fang Lee and Tzong-Ming Wu

Polymers 2023, 15(5), 1276; https://doi.org/10.3390/polym15051276 - 02 Mar 2023

Viewed by 1326

Abstract

The application efficiency of biodegradable polymers used in a natural environment requires improved resistance to ultraviolet (UV) photodegradation. In this report, 1,6-hexanediamine modified layered zinc phenylphosphonate (m-PPZn), utilized as a UV protection additive for acrylic acid-grafted poly(butylene carbonate-co-terephthalate) (g-PBCT), was successfully fabricated and [...] Read more.

The application efficiency of biodegradable polymers used in a natural environment requires improved resistance to ultraviolet (UV) photodegradation. In this report, 1,6-hexanediamine modified layered zinc phenylphosphonate (m-PPZn), utilized as a UV protection additive for acrylic acid-grafted poly(butylene carbonate-co-terephthalate) (g-PBCT), was successfully fabricated and compared to the solution mixing process. Experimental data of both wide-angle X-ray diffraction and transmission electron microscopy reveal that the g-PBCT polymer matrix was intercalated into the interlayer spacing of m-PPZn, which was approximately delaminated in the composite materials. The evolution of photodegradation behavior for g-PBCT/m-PPZn composites was identified using Fourier transform infrared spectroscopy and gel permeation chromatography after being artificially irradiated by a light source. The change of carboxyl group produced via photodegradation was used to show the enhanced UV protection ability of m-PPZn in the composite materials. All results indicate that the carbonyl index of the g-PBCT/m-PPZn composite materials after photodegradation for 4 weeks was extensively lower than that of the pure g-PBCT polymer matrix. These findings were also supported by the decrease in the molecular weight of g-PBCT after photodegradation for 4 weeks, from 20.76% to 8.21%, with the loading of 5 wt% m-PPZn content. Both observations were probably owing to the better UV reflection ability of m-PPZn. This investigation shows, through typical methodology, a significant advantage of fabricating the photodegradation stabilizer to enhance the UV photodegradation behavior of the biodegradable polymer using an m-PPZn compared to other UV stabilizer particles or additives. Full article

(This article belongs to the Special Issue Degradation and Stability of Polymer Based Systems)

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14 pages, 5748 KiB

Open AccessArticle

Enhancing the Initial Whiteness and Long-Term Thermal Stability of Polyvinyl Chloride by Utilizing Layered Double Hydroxides with Low Surface Basicity

by Guanhua Shen, Yanhua Zhao, Mingxin Ma, Yongli Wang, Xiangying Hao and Guodong Yuan

Polymers 2023, 15(4), 1043; https://doi.org/10.3390/polym15041043 - 19 Feb 2023

Viewed by 1546

Abstract

This study investigated the impact of surface basicity on the performance of layered double hydroxides (LDHs) as heat stabilizers for polyvinyl chloride (PVC). LDHs with varying surface basicity were synthesized and characterized using XRD, SEM, BET, and CO₂-TPD. The LDHs were [...] Read more.

This study investigated the impact of surface basicity on the performance of layered double hydroxides (LDHs) as heat stabilizers for polyvinyl chloride (PVC). LDHs with varying surface basicity were synthesized and characterized using XRD, SEM, BET, and CO₂-TPD. The LDHs were then combined with zinc stearate and dibenzoylmethane to create an environmentally friendly heat stabilizer and added to PVC. The resulting PVC composites were evaluated for thermal stability using the oven-aging method. The results showed that a lower Mg/Al molar ratio (2.0) improved the initial whiteness and long-term thermal stability of PVC composites compared to higher ratios (2.5, 3.0, and 3.5). Replacing Mg with Zn in the LDHs had a similar effect to that of reducing the Mg/Al ratio. Crosslinking the laminae of LDHs with 5% silane coupling agent KH-560 reduced the surface basicity of LDHs by 79%, increasing the chromaticity index, b*, and thermal stability time of PVC composites by 48% and 14%, respectively. A descriptive relationship was established between the structure and surface basicity of LDHs and the initial whiteness and long-term thermal stability of PVC composites. Full article

(This article belongs to the Special Issue Degradation and Stability of Polymer Based Systems)

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20 pages, 7686 KiB

Open AccessArticle

Spin Trapping Analysis of Radical Intermediates on the Thermo-Oxidative Degradation of Polypropylene

by Thu Anh Nguyen, Hui Ming Lim, Kenji Kinashi, Wataru Sakai, Naoto Tsutsumi, Satoko Okubayashi, Satoru Hosoda and Tetsu Sato

Polymers 2023, 15(1), 200; https://doi.org/10.3390/polym15010200 - 30 Dec 2022

Cited by 3 | Viewed by 2076

Abstract

The purpose of this study is to investigate the thermo-oxidative degradation behavior of polypropylene (PP) by comparing three types of pristine PP granules (consisting of homopolymer, random copolymer, and block copolymer) with their corresponding oxidized analogues. These analogues were intensely oxidized under oxygen [...] Read more.

The purpose of this study is to investigate the thermo-oxidative degradation behavior of polypropylene (PP) by comparing three types of pristine PP granules (consisting of homopolymer, random copolymer, and block copolymer) with their corresponding oxidized analogues. These analogues were intensely oxidized under oxygen at 90 °C for 1000 h by using the electron spin resonance (ESR) spin trapping method that can detect short-lived radical intermediates during the degradation. The degrees of oxidation could be evaluated by chemiluminescence (CL) intensity, which was related to the concentration of hydroperoxide groups generated in the PP chain. In the pristine PP samples, a small amount of hydroperoxides were found to be formed unintentionally, and their homolysis produces alkoxy radicals, RO•, which then undergo β-scission to yield chain-end aldehydes or chain-end ketones. These oxidation products continue to take part in homolysis to produce their respective carbonyl and carbon radicals. On the other hand, in the oxidized PP granules, because of their much higher hydroperoxide concentration, the two-stage cage reaction and the bimolecular decomposition of hydroperoxides are energetically favorable. Carbonyl compounds are formed in both reactions, which are then homolyzed to form the carbonyl radical species, •C(O)–. PP homopolymer produced the largest amount of carbonyl radical spin adduct; thus, it was found that the homopolymer is most sensitive to oxygen attack, and the presence of ethylene units in copolymers enhances the oxidation resistance of PP copolymers. Full article

(This article belongs to the Special Issue Degradation and Stability of Polymer Based Systems)

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12 pages, 2783 KiB

Open AccessArticle

Spin-Trapping Analysis of the Thermal Degradation Reaction of Polyamide 66

by Akihiro Kurima, Kenji Kinashi, Wataru Sakai and Naoto Tsutsumi

Polymers 2022, 14(21), 4748; https://doi.org/10.3390/polym14214748 - 05 Nov 2022

Cited by 3 | Viewed by 2144

Abstract

The radical mechanisms of the thermal degradation of polyamide 66 (PA66) occurring under a vacuum at a temperature range between 80 °C and 240 °C (which includes the temperature of practical applications) were investigated using a spin-trapping electron spin resonance (ST-ESR) technique, as [...] Read more.

The radical mechanisms of the thermal degradation of polyamide 66 (PA66) occurring under a vacuum at a temperature range between 80 °C and 240 °C (which includes the temperature of practical applications) were investigated using a spin-trapping electron spin resonance (ST-ESR) technique, as well as FTIR, TG-DTA, and GPC methods. No significant weight loss and no sign of thermal degradation are observed at this temperature range under oxygen-free conditions, but a slight production of secondary amine groups is confirmed by FTIR. GPC analysis shows a small degradation by the main chain scission. ST-ESR analysis reveals two intermediate radicals which are produced in the thermal degradation of PA66: (a) a ^●CH₂− radical generated by main chain scission and (b) a −^●CH− radical generated by hydrogen abstraction from the methylene group of the main chain. The ST-ESR result does not directly confirm that a −NH−^●CH− radical is produced, although this reaction has been previously inferred as the initiation reaction of the thermal degradation of PA; however, the presence of −^●CH− radicals strongly suggests the occurrence of this initiation reaction, which takes place on the α-carbon next to the NH group. The ST-ESR analysis reveals very small levels of reaction, which cannot be observed by common analytical methods such as FTIR and NMR. Full article

(This article belongs to the Special Issue Degradation and Stability of Polymer Based Systems)

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13 pages, 3072 KiB

Open AccessArticle

The Preparation of Hydroxyl-Terminated Deproteinized Natural Rubber Latex by Photochemical Reaction Utilizing Nanometric TiO₂ Depositing on Quartz Substrate as a Photocatalyst

by Apisara Sillapasuwan, Phattharawadi Saekhow, Porntip Rojruthai and Jitladda Sakdapipanich

Polymers 2022, 14(14), 2877; https://doi.org/10.3390/polym14142877 - 15 Jul 2022

Cited by 3 | Viewed by 1433

Abstract

Hydroxyl-terminated natural rubber (HTNR) is a product of interest for making natural rubber (NR) easy and versatile for use in a wide range of applications. Photochemical degradation using a TiO₂ film that has been deposited on a glass substrate is one of [...] Read more.

Hydroxyl-terminated natural rubber (HTNR) is a product of interest for making natural rubber (NR) easy and versatile for use in a wide range of applications. Photochemical degradation using a TiO₂ film that has been deposited on a glass substrate is one of the fascinating methods of producing HTNR. Nevertheless, light energy is wasted during the photodegradation process because a glass substrate has a cutoff for ultraviolet light. To enhance the effectiveness of the process, a quartz substrate was coated with the TiO₂ film for photochemical breakdown. X-ray diffraction (XRD) spectroscopy and atomic force microscopy (AFM) were applied to investigate the TiO₂ deposited on glass and quartz substrates. In addition, the influence of several factors, such as rubber and surfactant concentrations, on the reaction was investigated. After the reaction, the properties of the rubber products, including intrinsic viscosity, molecular weight, and microstructure, were determined. A unique diffraction peak for the anatase (101) phase could be observed in the TiO₂ film deposited on the quartz substrate, resulting in photochemical activity and photocatalytic efficiency significantly higher than those of the substrate made of glass. In the scenario of deproteinized NR (DPNR) latex containing 10% DRC, 20% w/w H₂O₂, and TiO₂ film coated on a quartz substrate, the HTNR could be manufactured effectively. Full article

(This article belongs to the Special Issue Degradation and Stability of Polymer Based Systems)

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Review

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23 pages, 5498 KiB

Open AccessReview

On Hair Care Physicochemistry: From Structure and Degradation to Novel Biobased Conditioning Agents

by Catarina Fernandes, Bruno Medronho, Luís Alves and Maria Graça Rasteiro

Polymers 2023, 15(3), 608; https://doi.org/10.3390/polym15030608 - 24 Jan 2023

Cited by 6 | Viewed by 7636

Abstract

Hair is constantly exposed to various adverse external stimuli, such as mechanical or thermal factors, that may cause damage or cause it to lose its shine and smooth appearance. These undesirable effects can be minimized by using hair conditioners, which repair the hair [...] Read more.

Hair is constantly exposed to various adverse external stimuli, such as mechanical or thermal factors, that may cause damage or cause it to lose its shine and smooth appearance. These undesirable effects can be minimized by using hair conditioners, which repair the hair and restore the smooth effect desired by the consumer. Some of the currently used conditioning agents present low biodegradability and high toxicity to aquatic organisms. Consumers are also becoming more aware of environmental issues and shifting their preferences toward natural-based products. Therefore, developing novel, sustainable, natural-based derivatives that can act as conditioning agents in hair care products and thus compete with the traditional systems obtained from non-renewable sources is highly appealing. This paper presents the key physicochemical aspects of the hair conditioning process, including hair structure and degradation, and reviews some of the new alternative conditioning agents obtained from natural resources. Full article

(This article belongs to the Special Issue Degradation and Stability of Polymer Based Systems)

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