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Thermal Insulating and Fire-Resistant Polymer Composites

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

Deadline for manuscript submissions: closed (18 February 2020) | Viewed by 44577

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Prof. Dr. Jingliang Li

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Institute for Frontier Materials, Deakin University, Waurn Ponds, VIC 3216, Australia
Interests: supramolecular assembly/materials; 3D printing; carbon materials
Special Issues, Collections and Topics in MDPI journals

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Dear Colleagues,

Polymeric materials have the advantages of being lightweight and have low thermal conductivity; hence, they are good for thermal insulation applications. However, their mechanical strength and fire-resistance are inferior to those of inorganic materials. Enforcing polymeric materials (e.g., foams) with fillers, such as particles, is a convenient approach to produce composite materials with improved mechanical properties. The fillers could also improve the thermal insulating and fire-resistance properties of the materials, which promotes the applications of polymeric materials many sectors such as buildings and aerospace. This Special Issue aims to gather the recent advances in this field. Both review and research articles are welcome. While synthetic polymers are suitable, special interest will be on natural polymers. In general, the processes for producing polymers from natural resources are greener than those for the synthetic ones. In addition, the use of natural polymer composites in various application does not impose significant hazards to human beings and the environment. Hence, they are more environmentally friendly and sustainable.

Associate Prof. Jingliang Li
Guest Editor

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Keywords

Polymer
Composite
Nanocomposite
Thermal insulation
Fire resistance

Published Papers (11 papers)

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Research

19 pages, 6178 KiB

Open AccessArticle

Base Promoted Intumescence of Phenols

by Yu Ji, Qiang Yao, Weihong Cao and Yueying Zhao

Polymers 2020, 12(2), 261; https://doi.org/10.3390/polym12020261 - 23 Jan 2020

Cited by 4 | Viewed by 2295

Abstract

The intumescent process of sodium (substituted) phenolates has been studied. The generation of hydrogen radical via a homolytic cleavage of the Ar–H bond and the subsequent hydroarylation of phenolates to cyclohexadienes along with cyclization and elimination reactions of cyclohexadienes are critical steps in the base promoted intumescence of phenols. The substituents show great influence on the intumescence of phenolates. Phenolates substituted with a weak electron donating group enable intumescence while those with an electron withdrawing group or strong electron donating group suppresses intumescence. This distinction can be justified by both electronic and steric effects of substituents on the generation of hydrogen radical and the degree of hydroarylation. Full article

(This article belongs to the Special Issue Thermal Insulating and Fire-Resistant Polymer Composites)

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14 pages, 4241 KiB

Open AccessArticle

Effect of Magnesium Hydroxide and Aluminum Hydroxide on the Thermal Stability, Latent Heat and Flammability Properties of Paraffin/HDPE Phase Change Blends

by Ru Zhou, Zhuang Ming, Jiapeng He, Yanming Ding and Juncheng Jiang

Polymers 2020, 12(1), 180; https://doi.org/10.3390/polym12010180 - 09 Jan 2020

Cited by 35 | Viewed by 5258

Abstract

In this study, paraffin was selected as the phase change material (PCM) and high-density polyethylene (HDPE) as the supporting material to prepare a flame-retardant PCM system. The system consisted of paraffin, HDPE, expanded graphite (EG), magnesium hydroxide (MH) and aluminum hydroxide (ATH). The thermal stability and flame retardancy were studied by thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM) and cone calorimeter test (CONE). The SEM proved that the addition of MH and ATH can produce an oxide film on the surface of the composite material and form a “physical barrier” with the char layer, generated by the expansion of EG, preventing the transfer of heat and oxygen. The TGA test showed that, compared with other flame-retardant systems, the materials with added MH and ATH have a higher thermal stability and carbonization ability, and the amount of char residue has increased from 17.6% to 32.9%, which reduces the fire risk of the material. The flame retardant effect is obvious. In addition, the addition of MH and ATH has no significant effect on the phase transition temperature and latent heat value of PCMs. The CONE data further confirmed that MH and ATH can work with EG to prevent heat release, reduce the total heat release rate (THR) value and effectively suppress the generation of smoke, CO and CO₂. The peak heat release rate (PHRR) value also decreased, from 1570.2 kW/m² to 655.9 kW/m². Full article

(This article belongs to the Special Issue Thermal Insulating and Fire-Resistant Polymer Composites)

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15 pages, 4316 KiB

Open AccessArticle

Study on Some Thermal and Electrical Properties of Basalt Fabric Modified with Metal and Ceramics as a Result of Magnetron Sputtering

by Pamela Miśkiewicz, Iwona Frydrych, Magdalena Tokarska and Wojciech Pawlak

Polymers 2019, 11(12), 2087; https://doi.org/10.3390/polym11122087 - 13 Dec 2019

Cited by 11 | Viewed by 2677

Abstract

The main aim of the research was to compare the values of some thermal and electrical parameters obtained for a basalt fabric modified with the metal and ceramics coatings. The surface modification of basalt fabric was made by using a magnetron sputtering technique. Chrome and zirconium(IV) oxide coatings were deposited on the fabric surface. The thermal and electrical properties of selected fabrics were determined. In order to assess the comfort properties of fabrics, the thermal resistance of materials was analyzed. Instrumental color measurement was used for an assessment of the surface of modified and unmodified basalt fabric. Using a non-contact digital color imaging system, DigiEye, an original method of samples surface analysis was presented. As a result of research, the modification of basalt fabric surface for applications in a hot work environment enabled the improvement of thermal properties in relation to the references samples. The first level of protection against contact heat for a contact temperature of 100 °C was obtained for the zirconium(IV) oxide-modified basalt fabric. The first level of protection against radiant heat was obtained for all samples. The highest value for the heat radiant resistance was obtained for the chrome-modified basalt fabric. Full article

(This article belongs to the Special Issue Thermal Insulating and Fire-Resistant Polymer Composites)

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14 pages, 2877 KiB

Open AccessArticle

Comparative Study on the Flame-Retardant Properties and Mechanical Properties of PA66 with Different Dicyclohexyl Hypophosphite Acid Metal Salts

by Heng Zhang, Junliang Lu, Hongyan Yang, Jinyan Lang and Heng Yang

Polymers 2019, 11(12), 1956; https://doi.org/10.3390/polym11121956 - 28 Nov 2019

Cited by 13 | Viewed by 3334

Abstract

Three metal salts of dicyclohexyl hypophosphite, namely dicyclohexyl aluminum hypophosphite (ADCP), dicyclohexyl magnesium hypophosphite (MDCP), and dicyclohexyl zinc hypophosphite (ZDCP), were synthesized. These flame retardants were subjected to thermogravimetric analysis, and the results showed that ADCP and ZDCP had higher thermal stabilities than MDCP. They were then separately mixed with polyamide 66 (PA66)to prepare composite materials, of which the combustion properties were determined by the limiting oxygen index method and horizontal/vertical burning experiments. The mechanical properties of the materials were further evaluated using an electronic universal testing machine. The results showed that all the three flame retardants exerted a flame-retardant effect on PA66, but the flame-retardant effect of MDCP was inferior to those of ADCP and ZDCP. All the composites also showed similar mechanical properties. Among the three flame retardants, ADCP had the best overall performance for raw materials, showing good flame-retardant properties while maintaining the mechanical properties of the raw materials. The optimal dosage of ADCP was 15 wt %, at which a V-0 rating in the vertical burning test (UL 94 test) can be obtained. Full article

(This article belongs to the Special Issue Thermal Insulating and Fire-Resistant Polymer Composites)

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18 pages, 6733 KiB

Open AccessArticle

Highly Effective Flame-Retardant Rigid Polyurethane Foams: Fabrication and Applications in Inhibition of Coal Combustion

by Liancong Wang, Benjamin Tawiah, Yongqian Shi, Suncheng Cai, Xiaohui Rao, Chuan Liu, Ye Yang, Fuqiang Yang, Bin Yu, Yuntao Liang and Libi Fu

Polymers 2019, 11(11), 1776; https://doi.org/10.3390/polym11111776 - 29 Oct 2019

Cited by 40 | Viewed by 4511

Abstract

The extemporaneous combustion of coal remains a major threat to safety in coal mines because such fire accidents result in casualties and significant property loss, as well as serious environmental pollution. This work proposed the fabrication of flame-retardant rigid polyurethane foam (RPUF) containing expandable graphite as char expander/sealant with melamine phosphosphate and 2-carboxyethyl (phenyl)phosphinic acid as char inducer and radical trapping agents. The as-prepared RPUF successfully inhibited coal combustion by forming thermally stable high graphitic content expandable intumescent char sealing over the coal. The RPUF achieved UL-94 V-0 rating in addition to significant reductions in peak heat release, total heat release, and CO and CO₂ yields. The external and the internal residual char structure was studied by X-ray photoelectron spectra, Raman spectroscopy, and real-time Fourier transform infrared spectra techniques, and a flame-retardant mode of action has been proposed. This work provides important insight into a facile fabrication of highly efficient and economical flame-retardant RPUF to inhibit the spontaneous combustion of coal. Full article

(This article belongs to the Special Issue Thermal Insulating and Fire-Resistant Polymer Composites)

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11 pages, 2464 KiB

Open AccessArticle

Synergistic Flame-Retardant Mechanism of Dicyclohexenyl Aluminum Hypophosphite and Nano-Silica

by Heng Zhang, Junliang Lu, Hongyan Yang, Heng Yang, Jinyan Lang and Qinqin Zhang

Polymers 2019, 11(7), 1211; https://doi.org/10.3390/polym11071211 - 19 Jul 2019

Cited by 14 | Viewed by 4543

Abstract

The flame retardant dicyclohexenyl aluminum hypophosphite (ADCP) and nano-silica are added to PA66 to improve flame retardant property of the composite. The flame-retardant property of the composite is tested via oxygen index test, vertical burning test, and cone calorimetry test. Combustion residues are tested using scanning electron microscopy, EDS spectroscopy, and Fourier infrared analysis. Results show that flame-retardant ADCP can effectively promote the formation of a porous carbon layer on the combustion surface of PA66. Nano-silica easily migrates to the material surface to improve the oxidation resistance of the carbon layer and the density of the carbon layer’s structure. It can also effectively prevent heat, flammable gases, and oxygen from entering the flame zone and enhance the flame retardant properties of ADCP. Full article

(This article belongs to the Special Issue Thermal Insulating and Fire-Resistant Polymer Composites)

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14 pages, 4340 KiB

Open AccessArticle

On the Origin of Alkali-Catalyzed Aromatization of Phenols

by Yu Ji, Qiang Yao, Yueying Zhao and Weihong Cao

Polymers 2019, 11(7), 1119; https://doi.org/10.3390/polym11071119 - 02 Jul 2019

Cited by 9 | Viewed by 3648

Abstract

To gain an insight of the chemistry in the alkali-promoted aromatization of oxygen-containing heavily aromatic polymers or biomass; thermal degradations of sodium phenolates with different substituents have been investigated. The -ONa group strongly destabilizes the phenolates. The thermal stability of phenolates is largely in parallel with bond strengths of Ar substituents. De-substituents and the removal of aromatic hydrogens are dominant reactions in the main degradation step. CO is formed only at a very late stage. This degradation pattern is completely different from that of phenol. To account for this distinctive decomposition; a mechanism involving an unprecedented formation of an aromatic carbon radical anion generated from the homolytic cleavage of Ar substituent (or Ar–H) in keto forms has been proposed. The homolytic cleavage of Ar substituent (or Ar–H) is facilitated by the strong electron-donating ability of the oxygen anion. A set of free-radical reactions involved in the alkali-catalyzed aromatization have been established. Full article

(This article belongs to the Special Issue Thermal Insulating and Fire-Resistant Polymer Composites)

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17 pages, 7395 KiB

Open AccessEditor’s ChoiceArticle

Synthesis of a Novel Phosphorous-Nitrogen Based Charring Agent and Its Application in Flame-retardant HDPE/IFR Composites

by Junlei Chen, Jihui Wang, Aiqing Ni, Hongda Chen and Penglong Shen

Polymers 2019, 11(6), 1062; https://doi.org/10.3390/polym11061062 - 19 Jun 2019

Cited by 28 | Viewed by 4461

Abstract

In this work, a novel phosphorous–nitrogen based charring agent named poly(1,3-diaminopropane-1,3,5-triazine-o-bicyclic pentaerythritol phosphate) (PDTBP) was synthesized and used to improve the flame retardancy of high-density polyethylene (HDPE) together with ammonium polyphosphate (APP). The results of Fourier transform infrared spectroscopy (FTIR) and ¹³C solid-state nuclear magnetic resonance (NMR) showed that PDTBP was successfully synthesized. Compared with the traditional intumescent flame retardant (IFR) system contained APP and pentaerythritol (PER), the novel IFR system (APP/PDTBP, weight ratio of 2:1) could significantly promote the flame retardancy, water resistance, and thermal stability of HDPE. The HDPE/APP/PDTBP composites (PE3) could achieve a UL-94 V-0 rating with LOI value of 30.8%, and had a lower migration percentage (2.2%). However, the HDPE/APP/PER composites (PE5) had the highest migration percentage (4.7%), lower LOI value of 23.9%, and could only achieve a UL-94 V-1 rating. Besides, the peak of heat release rate (PHRR), total heat release (THR), and fire hazard value of PE3 were markedly decreased compared to PE5. PE3 had higher tensile strength and flexural strength of 16.27 ± 0.42 MPa and 32.03 ± 0.59 MPa, respectively. Furthermore, the possible flame-retardant mechanism of the APP/PDTBP IFR system indicated that compact and continuous intumescent char layer would be formed during burning, thus inhibiting the degradation of substrate material and improving the thermal stability of HDPE. Full article

(This article belongs to the Special Issue Thermal Insulating and Fire-Resistant Polymer Composites)

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15 pages, 5080 KiB

Open AccessArticle

Preparation and Characteristics of an Environmentally Friendly Hyperbranched Flame-Retardant Polyurethane Hybrid Containing Nitrogen, Phosphorus, and Silicon

by Chin-Hsing Chen and Chin-Lung Chiang

Polymers 2019, 11(4), 720; https://doi.org/10.3390/polym11040720 - 19 Apr 2019

Cited by 20 | Viewed by 4283

Abstract

The NCO functional group of 3-isocyanatoproplytriethoxysilane (IPTS) and the OH functional group of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phospha-phenantbrene-10-oxide (DOPO-BQ) were used to conduct an addition reaction. Following completion of the reaction, triglycidyl isocyanurate (TGIC) was introduced to conduct a ring-opening reaction. Subsequently, a sol–gel method was used to initiate a hydrolysis–condensation reaction on TGIC–IPTS–DOPO-BQ to form a hyperbranched nitrogen–phosphorous–silicon (HBNPSi) flame retardant. This flame retardant was incorporated into a polyurethane (PU) matrix to prepare a hybrid material. Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), limiting oxygen index (LOI), UV-VIS spectrophotometry, and Raman analysis were conducted to characterize the structure and analyze the transparency, thermal stability, flame retardancy, and residual char to understand the flame retardant mechanism of the prepared hybrid material. After the flame retardant was added, the maximum degradation rate decreased from −36 to −17 wt.%/min, the integral procedural decomposition temperature (IPDT) increased from 348 to 488 °C, and the char yield increased from 0.7 to 8.1 wt.%. The aforementioned results verified that the thermal stability of PU can be improved after adding HBNPSi. The LOI analysis indicated that the pristine PU was flammable because the LOI of pristine PU was only 19. When the content of added HBNPSi was 40%, the LOI value was 26; thus the PU hybrid became nonflammable. Full article

(This article belongs to the Special Issue Thermal Insulating and Fire-Resistant Polymer Composites)

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15 pages, 4625 KiB

Open AccessArticle

Density Effect on Flame Retardancy, Thermal Degradation, and Combustibility of Rigid Polyurethane Foam Modified by Expandable Graphite or Ammonium Polyphosphate

by Hongyu Yang, Hongyin Liu, Yuping Jiang, Mingfeng Chen and Chaojun Wan

Polymers 2019, 11(4), 668; https://doi.org/10.3390/polym11040668 - 11 Apr 2019

Cited by 24 | Viewed by 4505

Abstract

The current study aims at comparatively investigating the effect of apparent density on flame retardancy, thermal degradation and combustion behaviors of rigid polyurethane foam (RPUF), RPUF/ expandable graphite (EG) and RPUF/ ammonium polyphosphate (APP). A series of RPUF, RPUF/EG and RPUF/APP samples with different apparent densities (30, 60 and 90 kg/m³) were prepared. The flame retardancy, thermal degradation, and combustion behaviors of each sample were investigated. Limiting oxygen index (LOI) results indicated that increasing apparent density was beneficial to the flame retardancy of all foam systems. The effect of apparent density on the enhancement of flame retardancy followed the sequence of RPUF < RPUF/APP < RPUF/EG. Thermogravimetric analysis (TGA) results showed that an increase in the apparent density can cause more weight loss in the first degradation stage and less weight loss in the second degradation stage for all foam systems. The combustion behaviors also showed significant differences. The samples with a higher apparent density showed a longer duration of heat release and higher total heat release (THR). The findings in this study demonstrated that apparent density played an important role in flame retardancy, thermal degradation, and combustion behaviors of RPUF, which must be paid more attention in the studies of flame-retardant RPUF. Full article

(This article belongs to the Special Issue Thermal Insulating and Fire-Resistant Polymer Composites)

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17 pages, 3979 KiB

Open AccessArticle

Construction of Carbon Microspheres-Based Silane Melamine Phosphate Hybrids for Flame Retardant Poly(ethylene Terephthalate)

by Baoxia Xue, Ruihong Qin, Jie Wang, Mei Niu, Yongzhen Yang and Xuguang Liu

Polymers 2019, 11(3), 545; https://doi.org/10.3390/polym11030545 - 22 Mar 2019

Cited by 12 | Viewed by 3818

Abstract

To improve the flame retardancy and inhibit the smoke of poly(ethylene terephthalate) (PET), carbon microspheres (CMSs)-based melamine phosphate (MP) hybrids (MP-CMSs) were constructed in situ with the introduction of CMSs into the hydrothermal reaction system of MP. The integrated MP-CMSs were modified by 3-Aminopropyltriethoxysilane (APTS) to obtain the silane MP-CMSs (SiMP-CMSs) to strengthen the interface binding between the MP-CMSs and PET matrix. The results showed that the SiMP layer was loaded on the CMSs surface. The addition of only 3% SiMP-CMSs increased the limiting oxygen index (LOI) value of the PET from 21% ± 0.1% to 27.7% ± 0.3%, reaching a V-0 burning rate. The SiMP-CMSs not only reduced heat damage, but also inhibited the smoke release during PET combustion, whereupon the peak heat release rate (pk-HRR) reduced from 513.2 to 221.7 kW/m², and the smoke parameters (SP) decreased from 229830.2 to 81892.3 kW/kg. The fire performance index (FPI) rose from 0.07 m²s/kW to 0.17 m²s/kW, demonstrating the lower fire risk. The proportion of the flame-retardant mode in the physical barrier, flame inhibition, and char effects were recorded as 44.53%, 19.04%, and 9.04%, respectively. Full article

(This article belongs to the Special Issue Thermal Insulating and Fire-Resistant Polymer Composites)

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