Cyclodextrins and Cyclodextrin Derivatives as Green Char Promoters in Flame Retardants Formulations for Polymeric Materials. A Review

Polymers are intrinsically flammable materials; hence, fire retardance (FR) is required in their most common applications (i.e., electronic and construction, to mention some). Recently, it has been reported that cyclodextrin (CD) and cyclodextrin derivatives are beginning to be introduced into Intumescent Fire Retardant (IFR) formulations in place of pentaerythritol, which is used in IFRs that are currently on the market. Since IFRs are of less environmental concern than their hazardous halogen containing counterparts, the use of natural origin compounds in IFRs provides a way to comply with green chemistry issues. BCD and BCD derivatives presence in IFR mixtures promotes a higher yield of blowing gases and char when polymeric materials undergo combustion. Both processes play important roles in intumescence. The key rule to obtain in insulating compact char is the good dispersion of the nanoparticles in the matrix, which can be achieved by functionalizing nanoparticles with BCD derivatives. Moreover, CD derivatives are attractive because of their nanosized structure and their ability to form inclusion complexes with many compounds used as FR components, reducing their release to the environment during their shelf life of FR items. Often, fire retardance performed by BCD and BCD derivatives accompanies other relevant properties, such as improved mechanical resistance, washability resistance, self healing ability, thermal conductivity, etc. The application of CD fire retardant additives in many polymers, such as poly(lactic acid), poly(propylene), poly(vinyl acetate), poly(methyl methacrylate), linear low density poly(ethylene), polyamides, and polyesters are comprehensively reviewed here.

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Nanocomposites Materials of PLA Reinforced with Nanoclays Using a Masterbatch Technology: A Study of the Mechanical Performance and Its Sustainability

Polymers ◽

10.3390/polym13132133 ◽

2021 ◽

Vol 13 (13) ◽

pp. 2133

Author(s):

Helena Oliver-Ortega ◽

Josep Tresserras ◽

Fernando Julian ◽

Manel Alcalà ◽

Alba Bala ◽

...

Keyword(s):

Food Packaging ◽

Mechanical Performance ◽

Polymeric Materials ◽

Barrier Properties ◽

Food Tray ◽

Environmental Concerns ◽

Poly Lactic Acid ◽

The Matrix ◽

Surface Modified ◽

Being Moved

Packaging consumes around 40% of the total plastic production. One of the most important fields with high requirements is food packaging. Food packaging products have been commonly produced with petrol polymers, but due to environmental concerns, the market is being moved to biopolymers. Poly (lactic acid) (PLA) is the most promising biopolymer, as it is bio-based and biodegradable, and it is well established in the market. Nonetheless, its barrier properties need to be enhanced to be competitive with other polymers such as polyethylene terephthalate (PET). Nanoclays improve the barrier properties of polymeric materials if correct dispersion and exfoliation are obtained. Thus, it marks a milestone to obtain an appropriate dispersion. A predispersed methodology is proposed as a compounding process to improve the dispersion of these composites instead of common melt procedures. Afterwards, the effect of the polarity of the matrix was analyzing using polar and surface modified nanoclays with contents ranging from 2 to 8% w/w. The results showed the suitability of the predispersed and concentrated compound, technically named masterbatch, to obtain intercalated structures and the higher dispersion of polar nanoclays. Finally, the mechanical performance and sustainability of the prepared materials were simulated in a food tray, showing the best assessment of these materials and their lower fingerprint.

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STUDYING THE INTERNAL STRESS HETEROGENEITY OF THE GROWING BIOFILM BY THE MICROPILLAR DEFORMATION OF THE GROWING SUBSTRATE

Journal of Mechanics in Medicine and Biology ◽

10.1142/s0219519419500702 ◽

2019 ◽

Vol 19 (06) ◽

pp. 1950070

Author(s):

XIAOLING WANG ◽

ZHAOCAN WANG ◽

XING SHEN ◽

YUHAO KONG ◽

HUI ZHAO ◽

...

Keyword(s):

Extracellular Matrix ◽

Internal Stress ◽

Early Time ◽

Bacterial Biofilm ◽

Internal Stresses ◽

Mechanical Resistance ◽

Self Healing ◽

Biofilm Thickness ◽

The Matrix ◽

Stress Heterogeneity

The bacterial biofilm is a microbial community in which bacteria are embedded in the extracellular matrix and can also be used as a solid composite. It was found that internal stresses are generated during pellicle growth, which exists between the air and the liquid. But we do not know if there is the internal stress in the biofilm, which exists between the air and the solid, and how does the internal stress evolve and distribute in the growing biofilm. So, in this paper, we make the growing substrate into the micropillar array to grow biofilms, each micropillar has the deformation due to the growing heterogeneity of the biofilm around the micropillar, and we can get the internal stress by measuring each micropillar’s deformation. First, we find that the direction of the internal stress is approximately along the biofilm expansion at the early time, colonies are formed in the biofilm at the later time, which cause the internal stress locally along the expansion of the colony. Second, the internal stress is proportional to the biofilm thickness. Finally, we find that the matrix producing cells contribute more the internal stress, and the internal stress evolving is closely related to the secretion of the extracellular matrix. Form our work, we obtain the distribution of the internal stress direction, we also can use the biofilm thickness, which is easy to measure, express the internal stress approximately, by doing so, we can further study other phenomena of biofilms, such as self-healing and mechanical resistance.

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Recent developments in fire-retardant thermoset resins using inorganic-organic hybrid flame retardants

Journal of Polymer Engineering ◽

10.1515/polyeng-2017-0224 ◽

2018 ◽

Vol 38 (6) ◽

pp. 563-571 ◽

Cited By ~ 1

Author(s):

Ewa Kicko-Walczak ◽

Grażyna Rymarz

Keyword(s):

Flame Retardants ◽

Fire Retardant ◽

Polymeric Materials ◽

Expandable Graphite ◽

Limiting Oxygen Index ◽

Thermoset Resins ◽

Organic Hybrid ◽

Thermoset Resin ◽

Recent Developments ◽

The Impact

Abstract Inorganic-organic hybrid modifiers have attracted attention of scholars worldwide because they combine the advantages of both different components and provide a way for modifying the structure and properties of polymeric materials. The article describes and investigates a positive effect of reduced flammability of thermoset resins resulting from the use of nanocomposites containing new inorganic-organic hybrid flame retardants (FRs) that combine conventional phosphorous/nitrogen modifiers interacting with nanofillers. The impact of these inhibitors on the level of flammability of thermoset resin compositions was defined by determining the value of limiting oxygen index, thermogravimetric and cone calorimeter analysis of thermal destruction processes. Morphology of composites was assessed using a scanning microscope and an analysis of actual scanning electron micrographic images. The analysis of thermal decomposition of the materials under examination confirmed flammability reducing properties of the inorganic-organic hybrid FR used, and a synergist to generate integrated flame retarding effect was observed between conventional modifiers and nanofillers, in particular carbon nanofillers: expandable graphite, graphene and graphene oxide. The inorganic-organic hybrid FR will provide a new solution to efficient FR polymeric materials.

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Aromatic vs. Aliphatic Hyperbranched Polyphosphoesters as Flame Retardants in Epoxy Resins

Molecules ◽

10.3390/molecules24213901 ◽

2019 ◽

Vol 24 (21) ◽

pp. 3901 ◽

Cited By ~ 6

Author(s):

Markwart ◽

Battig ◽

Velencoso ◽

Pollok ◽

Schartel ◽

...

Keyword(s):

Epoxy Resins ◽

Chemical Structure ◽

Flame Retardants ◽

Complex Shape ◽

Current Trend ◽

Polymeric Materials ◽

The Matrix ◽

Decomposition Pathway ◽

Halogen Free ◽

Phase Activity

The current trend for future flame retardants (FRs) goes to novel efficient halogen-free materials, due to the ban of several halogenated FRs. Among the most promising alternatives are phosphorus-based FRs, and of those, polymeric materials with complex shape have been recently reported. Herein, we present novel halogen-free aromatic and aliphatic hyperbranched polyphosphoesters (hbPPEs), which were synthesized by olefin metathesis polymerization and investigated them as a FR in epoxy resins. We compare their efficiency (aliphatic vs. aromatic) and further assess the differences between the monomeric compounds and the hbPPEs. The decomposition and vaporizing behavior of a compound is an important factor in its flame-retardant behavior, but also the interaction with the pyrolyzing matrix has a significant influence on the performance. Therefore, the challenge in designing a FR is to optimize the chemical structure and its decomposition pathway to the matrix, with regards to time and temperature. This behavior becomes obvious in this study, and explains the superior gas phase activity of the aliphatic FRs.

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In Vitro and In Vivo Biosafety Analysis of Resorbable Polyglycolic Acid-Polylactic Acid Block Copolymer Composites for Spinal Fixation

Polymers ◽

10.3390/polym13010029 ◽

2020 ◽

Vol 13 (1) ◽

pp. 29

Author(s):

Seung Kyun Yoon ◽

Jin Ho Yang ◽

Hyun Tae Lim ◽

Young-Wook Chang ◽

Muhammad Ayyoob ◽

...

Keyword(s):

Lactic Acid ◽

Animal Experiments ◽

Polymeric Materials ◽

Polyglycolic Acid ◽

Poly Lactic Acid ◽

Skin Sensitization ◽

Spinal Fixation ◽

In Vivo Degradation

Herein, spinal fixation implants were constructed using degradable polymeric materials such as PGA–PLA block copolymers (poly(glycolic acid-b-lactic acid)). These materials were reinforced by blending with HA-g-PLA (hydroxyapatite-graft-poly lactic acid) and PGA fiber before being tested to confirm its biocompatibility via in vitro (MTT assay) and in vivo animal experiments (i.e., skin sensitization, intradermal intracutaneous reaction, and in vivo degradation tests). Every specimen exhibited suitable biocompatibility and biodegradability for use as resorbable spinal fixation materials.

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Fire-Safe Polymer Composites: Flame-Retardant Effect of Nanofillers

Polymers ◽

10.3390/polym13040540 ◽

2021 ◽

Vol 13 (4) ◽

pp. 540

Author(s):

Yukyung Kim ◽

Sanghyuck Lee ◽

Hyeonseok Yoon

Keyword(s):

Organic Matter ◽

High Temperature ◽

Flame Retardant ◽

Flame Retardants ◽

Combustion Process ◽

Polymeric Materials ◽

Fire Performance ◽

Gaseous Species ◽

Advantages And Disadvantages ◽

Temperature Conditions

Currently, polymers are competing with metals and ceramics to realize various material characteristics, including mechanical and electrical properties. However, most polymers consist of organic matter, making them vulnerable to flames and high-temperature conditions. In addition, the combustion of polymers consisting of different types of organic matter results in various gaseous hazards. Therefore, to minimize the fire damage, there has been a significant demand for developing polymers that are fire resistant or flame retardant. From this viewpoint, it is crucial to design and synthesize thermally stable polymers that are less likely to decompose into combustible gaseous species under high-temperature conditions. Flame retardants can also be introduced to further reinforce the fire performance of polymers. In this review, the combustion process of organic matter, types of flame retardants, and common flammability testing methods are reviewed. Furthermore, the latest research trends in the use of versatile nanofillers to enhance the fire performance of polymeric materials are discussed with an emphasis on their underlying action, advantages, and disadvantages.

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Chlorine-Functional Silsesquioxanes (POSS-Cl) as Effective Flame Retardants and Reinforcing Additives for Rigid Polyurethane Foams

Molecules ◽

10.3390/molecules26133979 ◽

2021 ◽

Vol 26 (13) ◽

pp. 3979

Author(s):

Anna Strąkowska ◽

Sylwia Członka ◽

Karolina Miedzińska ◽

Krzysztof Strzelec

Keyword(s):

Flame Retardants ◽

Elevated Temperatures ◽

Bending Strength ◽

Reaction System ◽

Fire Retardant ◽

Polyurethane Foams ◽

Polymerization Reaction ◽

Three Point Bending ◽

One Step

The subject of the research was the production of silsesquioxane modified rigid polyurethane (PUR) foams (POSS-Cl) with chlorine functional groups (chlorobenzyl, chloropropyl, chlorobenzylethyl) characterized by reduced flammability. The foams were prepared in a one-step additive polymerization reaction of isocyanates with polyols, and the POSS modifier was added to the reaction system in an amount of 2 wt.% polyol. The influence of POSS was analyzed by performing a series of tests, such as determination of the kinetics of foam growth, determination of apparent density, and structure analysis. Compressive strength, three-point bending strength, hardness, and shape stability at reduced and elevated temperatures were tested, and the hydrophobicity of the surface was determined. The most important measurement was the determination of the thermal stability (TGA) and the flammability of the modified systems using a cone calorimeter. The obtained results, after comparing with the results for unmodified foam, showed a large influence of POSS modifiers on the functional properties, especially thermal and fire-retardant, of the obtained PUR-POSS-Cl systems.

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Comparison of the Dielectric Properties of Ecoflex® with L,D-Poly(Lactic Acid) or Polycaprolactone in the Presence of SWCN or 5CB

Materials ◽

10.3390/ma14071719 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1719

Author(s):

Patryk Fryń ◽

Sebastian Lalik ◽

Natalia Górska ◽

Agnieszka Iwan ◽

Monika Marzec

Keyword(s):

Oleic Acid ◽

Dielectric Properties ◽

Polymer Matrix ◽

Liquid Crystalline ◽

Weight Ratio ◽

Poly Lactic Acid ◽

Relaxation Processes ◽

The Matrix ◽

Walled Carbon Nanotubes ◽

Hybrid Layers

The main goal of this paper was to study the dielectric properties of hybrid binary and ternary composites based on biodegradable polymer Ecoflex®, single walled carbon nanotubes (SWCN), and liquid crystalline 4′-pentyl-4-biphenylcarbonitrile (5CB) compound. The obtained results were compared with other created analogically to Ecoflex®, hybrid layers based on biodegradable polymers such as L,D-polylactide (L,D-PLA) and polycaprolactone (PCL). Frequency domain dielectric spectroscopy (FDDS) results were analyzed taking into consideration the amount of SWCN, frequency, and temperature. For pure Ecoflex®, two relaxation processes (α and β) were identified. It was shown that the SWCN admixture (in the weight ratio 10:0.01) did not change the properties of the Ecoflex® layer, while in the case of PCL and L,D-PLA, the layers became conductive. The dielectric constant increased with an increase in the content of SWCN in the Ecoflex® matrix and the conductive behavior was not visible, even for the greatest concentration (10:0.06 weight ratio). In the case of the Ecoflex® polymer matrix, the conduction relaxation process at a frequency ca. several kilohertz appeared and became stronger with an increase in the SWCN admixture in the matrix. Addition of oleic acid to the polymer matrix had a smaller effect on the increase in the dielectric response than the addition of liquid crystal 5CB. Fourier transform infrared (FTIR) results revealed that the molecular structure and chemical character of the Ecoflex® and PCL matrixes remained unchanged upon the addition of SWCN or 5CB in a weight ratio of 10:0.01 and 10:1, respectively, while molecular interactions appeared between L,D-PLA and 5CB. Moreover, adding oleic acid to pure Ecoflex® as well as the binary and ternary hybrid layers with SWCN and/or 5CB in a weight ratio of Ecoflex®:oleic acid equal to 10:0.3 did not have an influence on the chemical bonding of these materials.

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Self Healing of Epoxy Composite for Aircraft's Structural Applications

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.136.39 ◽

2008 ◽

Vol 136 ◽

pp. 39-44 ◽

Cited By ~ 2

Author(s):

Willy C.K. Tan ◽

J.C. Kiew ◽

K.Y. Siow ◽

Z.R. Sim ◽

H.S. Poh ◽

...

Keyword(s):

Composite Structures ◽

Polymeric Materials ◽

Hollow Fibre ◽

The Body ◽

Strength Increase ◽

Self Healing ◽

Structural Applications ◽

Self Repair ◽

Repair Systems ◽

Point Bend

When one cut himself, it's amazing to watch how quickly the body acts to mend the wound. Immediately, the body works to pull the skin around the cut back together. The concept of repair by bleeding of enclosed functional agents serves as the biomimetric inspiration of synthetic self repair systems. Such synthetic self repair systems are based on advancement in polymeric materials; the process of human thrombosis is the inspiration for the application of self healing fibres within the composite materials. Preliminary results based on flexural 3 point bend test on prepared samples have shown the healed hollow fibre laminate has a healed strength increase of 47.6% compared to the damaged baseline laminate. These results gave us confidence that there is a great potential to adopt such self healing mechanism on actual composite parts like in aircraft’s composite structures.

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Mechanical responses of microencapsulated self-healing cementitious composites under compressive loading based on a micromechanical damage-healing model

International Journal of Damage Mechanics ◽

10.1177/10567895211011239 ◽

2021 ◽

pp. 105678952110112

Author(s):

Kaihang Han ◽

Jiann-Wen Woody Ju ◽

Yinghui Zhu ◽

Hao Zhang ◽

Tien-Shu Chang ◽

...

Keyword(s):

Fracture Toughness ◽

Compressive Strength ◽

Micromechanical Model ◽

Cementitious Composites ◽

Self Healing ◽

Damage Degree ◽

Healing Efficiency ◽

The Matrix ◽

Healing Agent ◽

Damage Healing

The cementitious composites with microencapsulated healing agents have become a class of hotspots in the field of construction materials, and they have very broad application prospects and research values. The in-depth study on multi-scale mechanical behaviors of microencapsulated self-healing cementitious composites is critical to quantitatively account for the mechanical response during the damage-healing process. This paper proposes a three-dimensional evolutionary micromechanical model to quantitatively explain the self-healing effects of microencapsulated healing agents on the damage induced by microcracks. By virtue of the proposed 3 D micromechanical model, the evolutionary domains of microcrack growth (DMG) and corresponding compliances of the initial, extended and repaired phases are obtained. Moreover, the elaborate studies are conducted to inspect the effects of various system parameters involving the healing efficiency, fracture toughness and preloading-induced damage degrees on the compliances and stress-strain relations. The results indicate that relatively significant healing efficiency, preloading-induced damage degree and the fracture toughness of polymerized healing agent with the matrix will lead to a higher compressive strength and stiffness. However, the specimen will break owing to the nucleated microcracks rather than the repaired kinked microcracks. Further, excessive higher values of healing efficiency, preloading-induced damage degree and the fracture toughness of polymerized healing agent with the matrix will not affect the compressive strength of the cementitious composites. Therefore, a stronger matrix is required. To achieve the desired healing effects, the specific parameters of both the matrix and microcapsules should be selected prudently.

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