Enhancement of PUR/PIR foam thermal stability after addition of Zostera marina biomass component investigated via thermal analysis and isoconversional kinetics

In the present work, a thorough thermogravimetric (TG) analysis of bio-based polyurethane–polyisocyanurate (PUR–PIR) foams in both nitrogen and oxygen atmosphere is performed. A sustainable element of the foam is a biopolyol obtained via acid-catalyzed liquefaction of Zostera marina and Enteromorpha Algae biomass. Based on isoconversional analysis and apparent activation energies, several conclusions are obtained. In contradiction to the common understanding, biopolyol based foams exhibit enhanced stability in both oxidative atmosphere and in nitrogen compared to purely petrochemical foams. Relationships between thermal stability and structure of the foams are established. Enhanced stability of bio-based foams in oxygen is attributed to two factors. First is an increased cross-linking density due to higher hydroxyl number of biopolyol compared to petrochemical one. Possibly the presence of more amount of aromatic compounds in the structure of polyols that come from lignin or aromatic ketones contribute to further enhancement of thermal stability. Those results suggest that the studied biobased foams are prospective alternatives to standard petrochemical PUR foams.     

毛竹屑与玉米淀粉共液化产物制备聚氨酯泡沫研究

采用单因素试验设计,研究了液化剂组成、液比以及毛竹屑与淀粉的比例对液化产物理化性质、及所制备的聚氨酯泡沫材料的物理力学指标影响.结果显示当以50%乙二醇+50%碳酸亚乙酯混合物作为液化剂、添加相当于液化剂质量3%的浓硫酸为催化剂、在(150±5)℃(油浴)和常压条件下,液化150min,搅拌速度30r/min,取得本试验条件下最好的竹屑液化效果,液化产物中竹屑含量25%,残渣率3.96%,但该液化产物中天然聚合物碎片含量少,所制备的聚氨酯泡沫材料塌陷;竹屑与玉米淀粉共液化有效提高了液化产物中生物质的含量,但占液化剂质量25%竹屑+占液化剂质量125%玉米淀粉共液化产物粘度太高(8.85Pa.s);而20%竹屑+130%玉米淀粉的共液化产物与4,4′-二苯基甲烷二异氰酸酯以及各种助剂按异氰酸酯基/羟基摩尔比为1.1配合时,所制备的聚氨酯泡沫材料表观密度为33.6kg/m3、压缩强度118kPa、弹性模量6.91MPa,在周年生物降解试验中,该生物质基聚氨酯硬质泡沫失重率为12.63%.     

Preparation and characterization of biopolyol via liquefaction of rice straw

Biopolyols were prepared by the liquefaction of rice straw under the mild condition. The optimum liquefaction effect was obtained at 5 : 1 volume ratio of PEG400 to DEG, 4 : 1 liquid–solid ratio, H₂SO₄ 3%, time 2.5 h, and reaction temperature120°C. Products were characterized by FTIR and gel permeation chromatograms (GPC) measurements. The hydroxyl value and weight-average molecular weight of the biopolyol produced based on the above optimal conditions were 260 mg KOH/g polyol and 420 g mol^–1, respectively. Biopolyol obtained is suitable for the preparation of rigid polyurethane foam. This study has certain significance for the high added value use of rice straw and reducing the production cost and improvement biodegradability of polyurethane foams.     

基于天然聚多糖的环境友好材料（II）-麻纤维和芦苇纤维多元醇的生物降解聚氨酯

以麻纤维和芦苇纤维制备的植物多元醇为原料,合成具有良好性能的生物降解 性硬质聚氨酯泡沫体,其密度40 kg/m~3左右,压缩强度150 kPa,弹性模量4 MPa 。而且多元醇中植物原料含量越大,其性能越好,这使植物原料的充分利用和材料 生产成本的降低成为可能。土壤掩埋实验表明,泡沫体有很好的土壤微生物降解性 。     

Carbon nanofibers reinforced soy polyol-based polyurethane nanocomposites

Vapor-grown carbon nanofiber (CNF)-modified soy polyol-based polyurethane (PU) nanocomposites with different hydroxyl value of polyols (OH) were synthesized. The glass transition, thermal stability, mechanical properties, and morphology of the PU nanocomposites were characterized through differential scanning calorimetry, thermogravimetry, universal test machine, and scanning electron microscopy. The addition of CNFs increased the glass transition temperature as well as significantly improved tensile strength and Young’s modulus of PU nanocomposites. Meanwhile, thermal and mechanical properties of PU composites were influenced by the different hydroxyl value of polyols due to those different structures. In particular, in the case of 2 mass% CNF addition in PU derived from soy polyol with the OH number of 164 mg KOH g^?1, 20.8 °C improvement in the glass transition temperature, 115 % increment in tensile strength, and nearly eightfold increase in Young’s modulus were obtained.     

Glass transition and thermal degradation of rigid polyurethane foams derived from castor oil–molasses polyols

Rigid polyurethane (PU) foams having saccharide and castor oil structures in the molecular chain were prepared by reaction between reactive alcoholic hydroxyl group and isocyanate. The apparent density of PU foams was in a range from 0.05 to 0.15 g cm^?3. Thermal properties of the above polyurethane foams were studied by differential scanning calorimetry, thermogravimetry and thermal conductivity measurement. Glass transitions were observed in two steps. The low-temperature side glass transition was observed at around 220 K, regardless of castor oil content. This transition is attributed to the molecular motion of alkyl chain groups of castor oil. The high-temperature side glass transition observed in the temperature range from 350 to 390 K depends on the amount of molasses polyol content. The high-temperature side glass transition is attributed to the molecular motion of saccharides, such as sucrose, glucose, fructose as well as isocyanate phenyl rings, which act as rigid components. Thermal decomposition was observed in two steps at 570 and 620–670 K. Thermal conductivity was observed at around 0.032 J sec^?1 m^?1 K^?1. Compression strength and modulus of PU foams were obtained by mechanical test. It was confirmed that the thermal and mechanical properties of PU foams could be controlled by changing the mixing ratio of castor oil and molasses for suitable practical applications.     

Scalable single-step synthesis of lignin-based liquid polyols with ethylene carbonate for polyurethane foams

A new method for the synthesis of lignin-based liquid polyols was developed. Organosolv lignin was reacted with ethylene carbonate in polyethylene glycol as solvent, leading to a full conversion of the phenolic OH into primary aliphatic OH groups. These aromatic polyols are obtained in a single step, without any purification. Upon modification of the polyethylene glycol molar mass, a wide range of hydroxyl values (I_OH) can be covered. The polyols with up to 30%wt lignin have a viscosity suitable for the direct elaboration of polyurethane (PUR) foams. The method presents significant advantages over oxypropylation, the most common method for producing lignin-based polyols since it is performed at ambient pressure, without any toxic chemicals, does not require purification or post treatment, and allows to produce polyols with tunable properties. Four different aromatic polyols were then synthesized to produce rigid PUR foams, with substitution of up to 100% of a standard polyether polyol. The developed polyols showed very high reactivity, allowing to reduce the catalyst content in the PUR formulation by 75%. Rigid PUR foams prepared with 25% substitution of the standard polyol showed properties in the range of commercial PUR foams, with more than 90% closed cells and thermal conductivity of about 25 mW m^?1/K, perfectly adequate for thermal insulation applications.     

Structure and properties of polyurethanes based on halogenated and nonhalogenated soy–polyols

Four polyols were prepared by a ring opening of epoxidized soybean oil with HCl, HBr, methanol, and by hydrogenation. Two series of polyurethanes were prepared by reacting the polyols with two commercial isocyanates: PAPI and Isonate 2143L. Generally, the properties of the two series were similar. The crosslinking density of the polyurethane networks was analyzed by swelling in toluene. Brominated polyols and their corresponding polyurethanes had the highest densities, followed by the chlorinated, methoxylated, and hydrogenated samples. The polyurethanes with brominated and chlorinated polyols had comparable glass transition and strength, somewhat higher than the polyurethane from methoxy containing polyol, while the polyurethane from the hydrogenated polyol had lower glass‐transition and mechanical properties. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4062–4069, 2000     

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

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.     

Synthesis and thermal studies of flexible polyurethane nanocomposite foams obtained using nanoclay modified with flame retardant compound

This work presents thermal studies of nanocomposites based on the flexible polyurethane (PU) matrix and filled using montmorillonite organically modified with organophosphorus flame retardant compound. Flexible PU nanocomposite foams were prepared in the reaction carried out between reactive alcoholic hydroxyl and isocyanate groups with the ratio of NCO to OH groups equal to 1.05. The amount of an organoclay ranging from 3 to 9 vol% was added to the polyol component of the resin before mixing with isocyanate. The apparent density of PU foams was ranging from 0.066 to 0.077 g cm^?1. Thermal properties of the flexible PU nanocomposite foams were investigated by thermogravimetry and dynamical mechanical analysis. Glass transition temperatures (T _g) were defined as maximum peak on tanδ curve. Thermal decomposition was observed at 310–320 °C (calculated from the onset of TG curve). Tensile strength of the PU foams was determined using mechanical test. The microstructure of the nanoparticles and the composites was investigated by X-ray diffraction. Finally, it was confirmed that the thermal and mechanical properties of flexible PU nanocomposite depend on the amount of nanoclay.     

One-pot synthesis of biofoams from castor oil and cellulose microfibers for energy absorption impact materials

The use of renewable feedstocks in foam technology has created a worldwide demand for more sustainable materials. Castor oil is a vegetable oil, composed mainly of triricinoglycerol, a natural polyol, suitable for polyurethane foam production. In this study, castor oil and variable amounts of microcrystalline cellulose (MCC) fibers were used in a straightforward one-pot synthesis approach for the preparation of novel biofoams. The ensuing biofoams were characterized by several techniques, including attenuated total reflectance Fourier transform infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis, and their mechanical performance was evaluated by compression mechanical testing and by dynamic mechanical thermal analysis. They were (semi-) flexible, with a cell-like morphology and reinforced toughness due to the use of MCC. They had a Young’s modulus varying between 0.188 and 1.06 MPa depending on the amount of MCC used and were thermally stable up to 267 °C. The properties of these novel biofoams enable them to be strong candidates for use as tough, energy-absorbing foams, advantageously prepared using renewable-based resources.     

Design,polymerization, and properties of polyurethane elastomers from miscible,immiscible, and hybridized seed‐oil derived soft segment blends

Polyester seed‐oil derived polyols have been prepared and blended with conventional polyols for making polyurethane elastomers. Miscibility was complete for polypropylene oxide/polyethylene oxide and polytetramethylene oxide (PTMEG). Blends of polyester seed‐oil derived polyols with conventional polyester polyols (polybutylene adipate and ?‐polycaprolactone) were immiscible or nearly so. Furthermore, the phase behavior (miscible vs. immiscible) did not change appreciably for each blend composition explored as a function of temperature at relevant ranges (up to the polyether ceiling temperature). This counter‐intuitive result is found to be actually consistent with calculated solubility parameters for each polyol type and the phase diagrams computed on their basis. The phase behavior of the polyols is shown to have significant effects on the properties of polyurethane elastomers where immiscible polyols cause broadening of the glass transition distribution and significant reduction of ultimate tensile properties. However, here it is shown that immiscible systems containing polyester seed‐oil derived polyols can be transesterified with the appropriate polyol partner of interest to create a new single phase polyol or that the polyester polyol monomers can also be copolymerized to make new single phase polyols, both of which result in improved polyurethane elastomer properties. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 93–102     

Effect of glycols used as glycolysis agents on chemical structure and thermal stability of the produced glycolysates

In this study, the influence of glycols on chemical structure and thermal stability of glycolysates as polyurethane intermediates were investigated. The intermediates were obtained by the glycolysis process of waste polyurethane foams in the reaction with different glycols ranging from ethylene glycol to hexane-1,6-diol. The used glycols were not separated from the product after the glycolysis process has been terminated. The effects of different weight ratio of glycols to polyurethane (PU) foam on chemical structure and thermal stability were investigated by FTIR, GPC, and TG/DTG. FTIR analysis of the glycolysates revealed their similar chemical architecture as manifested by the similarity of absorption peaks within the entire wavenumber range of spectra. This may indicate that the glycol has no influence on the chemical composition of glycolysates. GPC analysis showed that the glycolysates were characterized by polydispersity smaller than 2 which is lower as compared to some commercial polyols used for PU synthesis. GPC chromatograms showed that the applied glycols and the conditions of PU glycolysis allowed recreation of the original polyol as documented on the chromatograms by a single, well-formed peak at the beginning of retention time. Based on TG thermograms, it was established that glycol used in transesterification of PUs affected the temperature at which the loss of glycolysate mass by 5 and 10?% occurs. It was also observed that glycol affected the temperature at which the decomposition rate of glycolysates was the highest.     

Activities of octoate salts as novel catalysts for the transesterification of flexible polyurethane foams with diethylene glycol

Polyurethane foams are disposed of not only at the end of their use but also as scrap during slabstock manufacturing, leading to an environmental and economic problem. Flexible polyurethane foams can be advantageously treated by two-phase glycolysis in order to recover their constituent polyols with an improved quality compared to the single phase processes. The glycolysis comprises a transesterification, which has been traditionally catalyzed by alkanolamines, titanium compounds and acetates. In this work, the performance evaluation of new catalysts based on alkaline, alkaline-earth and transition metal octoate salts has been carried out. The carboxylates have showed different catalytic activities according to their basicity and coordination ability. A reaction mechanism for the polyurethane glycolysis in the presence of the carboxylate catalysts studied has also been proposed. The mechanism involves several steps, including the formation of a metal alkoxylate, coordination-insertion of the alkoxide into the urethane group and transfer from recovered polyol to glycol. Among the octoates studied, lithium and stannous octoates showed a remarkable catalytic activity. They yielded the greatest quality for the recovered polyol as well as the highest decomposition rates.     

Synthesis and thermal properties of soybean oil-based waterborne polyurethane coatings

Waterborne polyurethane coatings were prepared by a polyaddition reaction using toluene diisocyanate (TDI), 2,2-di(hydroxy-methyl) propionic acid, soy-based polyols with different hydroxyl values, plus 2-hydroxyethyl methacrylate (HEMA) as chain termination agent, triethylamine as neutralization agent, and DBTDL as catalyst. Six soybean oil-based polyols were used in this study with hydroxyl values of 100, 115, 128, 140, 155, and 164 mg KOH g⁻¹, respectively. The molar ratio of polyol hydroxyl to DMPA was varied from 1.6 to 2.6. The storage stability of the waterborne polyurethane coatings was greater than 6 months. The thermal properties of the coating films were investigated by TG and DCS. The results show that the soy-based polyurethane films decomposed in three stages. The glass transition temperatures, T _g, of the soy-based polyurethane films increased with the hydroxyl number of the soy-based polyol.     

Recovery of polyols from flexible polyurethane foam by “split-phase” glycolysis: Glycol influence

Scrap of flexible polyurethane foams from slabstock manufacturing comprises about 10% of the total production, leading to not only an environmental problem but also an economic one. The general purpose of polyurethane chemical recycling is to recover a valuable constituent, the polyol. Among the processes suitable, glycolysis, and specially glycolysis in two phases seems to be the method that allows better quality products. In this study glycolysis of flexible polyurethane foams in “split phase” was conducted with different glycols, in order to study their activity and select a system to obtain the highest quality recovered polyol. Reaction kinetics and the products obtained were investigated. Times required to reach complete conversion, chemical properties of the polyol phase and its purity depended on the glycol employed. Diethylene glycol proved to be the most suitable glycol to obtain a high purity in the polyol phase.     

Atmospheric Pressure Liquefaction of Dried Distillers Grains (DDG) and Making Polyurethane Foams from Liquefied DDG

In this study, dried distillers grains (DDG) was liquefied in acidic conditions at atmospheric pressure, and polyurethane foams were subsequently prepared from the liquefied DDG. Liquefaction was examined over a range of conditions including liquefaction time of 1–3 h, temperature of 150–170 °C, sulfuric acid (as catalyst) concentration of 1.0–3.0 wt%, and liquefaction solvent (ethylene carbonate) to DDG ratio of 3:1–5:1. The bio-polyols in the liquefied DDG were rich in hydroxyl groups, which can react with methylene diphenyl diisocyanate (MDI) to form cross-linked polyurethane networks. The biodegradability of the prepared polyurethane foams was also evaluated. This study strives to broaden the application of DDG as a feedstock for bio-polyurethane preparation.     

Effects of biopitch on the properties of flexible polyurethane foams

Biopitches are industrial residues obtained by the distillation of the tar recovered during Eucalyptus charcoal production and can be used as a renewable polyol source. Flexible polyurethane foams were prepared with different proportions of biopitch and HTPB (hydroxyl-terminated polybutadiene) and using polymeric MDI (4,4′ diphenyl methane diisocyanate), N,N dimethylcyclohexylamine as a catalyst and water as a blowing agent. Elemental analysis, thermal analysis (TG/DSC), Fourier Transform Infrared Spectroscopy (FTIR), scanning electronic microscopy (SEM), and density results were used aiming to discuss the contribution of biopitch to foams properties. The higher the biopitch content, the higher the thermal stability and the lower the density of the flexible foams (air atmosphere), behaviors similar to those of lignin-based polyurethanes. Biopitch enhanced the oxygen content of the polyurethane foams synthesized, and their reaction with HTPB resulted in stable foams.     

Biobased porous acoustical absorbers made from polyurethane and waste tire particles

The production of flexible polyurethane foams (FPF) with good acoustical performance to control sound and noise and incorporating bio/recycled raw materials is an interesting alternative to conventional acoustic absorbent materials. In this sense, biobased polyols like glycerol (GLY) or hydroxylated methyl esters derived from tung oil (HMETO) as multifunctional polyols, and waste tire particles (WTP) as fillers of low thermal conductivity and good capability for acoustical absorption, are prospective feedstocks for FPF preparation. In this work, FPF were prepared by adding different amounts of these components to a formulation based on a commercial polyether polyol. Results of scanning electron microscopy (SEM) analysis, compression tests and normal-incidence sound absorption coefficient (α_N) measurements are presented and discussed. The addition of WTP or GLY to the commercial formulation enhanced both the modulus and yield stress of the obtained FPF in all cases. Moreover, a high recovery of the applied strain (>90%) was attained 24 h after the compression tests. On the other hand, the normal-incidence sound absorption coefficient, α_N, reached high values mostly at the highest evaluated frequencies (α_N ∼0.62–0.89 at 2000 Hz and α_N ∼0.70–0.91 at 5000 Hz). SEM micrographs revealed that the foams obtained present a combination of open and closed cell structure and both the modifiers and particles tend to decrease the cell size.     

Sound absorption properties of polyurethane foams derived from crude glycerol and liquefied coffee grounds polyol

The main objective of this study was to evaluate the sound absorption properties of rigid polyurethane foams (PUFs) produced from crude glycerol (CG) and/or liquefied coffee grounds derived polyol (POL). The lignin content of POL proved to have a major influence on the structure and mechanical properties of the foams. Indeed, the POL content increased the cell size of the foams and their stiffness, which subsequently influenced the sound absorption coefficients. The POL derived foam has slightly higher sound absorption coefficient values at lower frequencies, while the CG foam has higher sound absorption coefficient values at higher frequencies. In turn, the foam prepared using a 50/50 mixture of polyols presents slightly higher sound absorption coefficient values in the medium frequencies range due to a balance between the cell structure and the mechanical properties. The results obtained seem to suggest that the mechanisms involved in sound wave absorption depend on the formulation used to prepare the foams. Additionally higher POL contents improved the thermal stability of PUFs as well as their mechanical properties. From this work the suitability of CG and/or POL derived PUFs as sound absorbing materials has been proven.