Commercial Polyol Research Articles

Design of polyurethane composite foam obtained from industrial PET wastes and MXenes for EMI shielding applications.

The primary aim of this study was to synthesize and characterize polyurethane (PUR) foams derived from the depolymerization products of poly(ethylene terephthalate) (PET) and MXenes (Nb2AlC). The depolymerized PET products were produced through a zinc acetate-catalyzed glycolysis process using diethylene glycol (DEG) as solvent. These glycolysis products were then reacted with 4,4'-diphenylmethane diisocyanate (MDI), commercial polyols, and MXenes to produce the PUR foams. The resulting materials were characterized using FT-IR, SEM, EDX mapping, mechanical testing, thermal analysis, and electromagnetic interference (EMI) shielding assessments. The analysis revealed that specimens with a higher concentration of the filler (3.55%) exhibited superior mechanical properties, while the thermal behavior remained relatively unchanged. The sample containing 2.56% of MXenes showed significant potential as an effective EMI shielding material in the 8-9 GHz frequency range, while the blank sample provided the best performance between 9-13 GHz, mostly due to a bigger high-frequency absorption in the upper part of the X band. Regarding mechanical performance, the compression force increased slightly from 1013.31 N to 1013.71 N as the Mxenes concentration increased from 2.56% to 3.55%.

Liquefaction optimization of grape pulp using response surface methodology for biopolyol production and bio-based polyurethane foam synthesis.

Both environmental and economic disadvantages of using petroleum-based products have been forcing researchers to work on environmentally friendly, sustainable, and economical alternatives. The purpose of this study is to optimize the solvothermal liquefaction process of grape pomace using response surface methodology coupled with a central composite design. After investigating the physicochemical properties of the liquified products (biopolyol) in detail, a bio-based rigid polyurethane foam (RPUF) was synthesized and characterized. The hydroxyl and acid numbers and viscosity values of all the biopolyols were analyzed. According to variance analysis results (%95 confidence range), both the reaction temperature and catalyst loading were determined as significant parameters on the liquefaction yield (LY). The model was validated experimentally in the following reaction conditions: 4.25% catalyst loading, 50 min reaction time, and 165 °C reaction temperature, which yields an LY of 81.3%. The biopolyols produced by the validation experiment display similar characteristics (hydroxyl number: 470.5 mg KOH/g; acid number: 2.31 mg KOH/g; viscosity: 1785 cP at 25 °C) to those of commercial polyols widely preferred in the production of polyurethane foam. The physicochemical properties of bio-based foam obtained from the biopolyol were determined and the thermal conductivity, closed-cell content, apparent density, and compressive strength values of bio-based RPUF were 31.3 mW/m·K, 71.1%, 33.4 kg/m3, and 105.3 kPa, respectively.

Harnessing Enhanced Flame Retardancy in Rigid Polyurethane Composite Foams through Hemp Seed Oil-Derived Natural Fillers.

Over the past few decades, polymer composites have received significant interest and become protagonists due to their enhanced properties and wide range of applications. Herein, we examined the impact of filler and flame retardants in hemp seed oil-based rigid polyurethane foam (RPUF) composites' performance. Firstly, the hemp seed oil (HSO) was converted to a corresponding epoxy analog, followed by a ring-opening reaction to synthesize hemp bio-polyols. The hemp polyol was then reacted with diisocyanate in the presence of commercial polyols and other foaming components to produce RPUF in a single step. In addition, different fillers like microcrystalline cellulose, alkaline lignin, titanium dioxide, and melamine (as a flame retardant) were used in different wt.% ratios to fabricate composite foam. The mechanical characteristics, thermal degradation behavior, cellular morphology, apparent density, flammability, and closed-cell contents of the generated composite foams were examined. An initial screening of different fillers revealed that microcrystalline cellulose significantly improves the mechanical strength up to 318 kPa. The effect of melamine as a flame retardant in composite foam was also examined, which shows the highest compression strength of 447 kPa. Significantly better anti-flaming qualities than those of neat foam based on HSO have been reflected using 22.15 wt.% of melamine, with the lowest burning time of 4.1 s and weight loss of 1.88 wt.%. All the composite foams showed about 90% closed-cell content. The present work illustrates the assembly of a filler-based polyurethane foam composite with anti-flaming properties from bio-based feedstocks with high-performance applications.

Sustainable production and evaluation of bio-based flame-retardant PU foam via liquefaction of industrial biomass residues

The utilization of low-cost renewable feedstock, such as furfural residue and crude glycerol, presents great potential for advancing the bio-based polymer industry. Firstly, this study explored the feasibility of using furfural residue liquefaction in the presence of crude glycerol to synthesize biopolyols. The optimal conditions for liquefaction were determined to be 220 ℃, 3 h, with a 7% sodium hydroxide loading and 9% biomass loading. The hydroxyl and acid numbers of prepared biopolyols were found to be comparable to those of commercial polyols, which were 460 mg KOH/g and 2.25 mg KOH/g, respectively. Subsequently, newly bio-based flame-retardant polyurethane (PU) foam was produced using obtained biopolyols, isocyanate, and flame retardants. The foam demonstrated a compressive strength of 286 kPa and a density of 0.050 g·cm−3, with its thermal conductivity measured at 0.032 W·m−1·K−1. To enhance the flame retardant and insulation properties of the PU foam, 2% of modified hollow silica (Kh-SiO2) was incorporated. PU foams produced under optimal conditions exhibited a limiting oxygen index of 27.25%, demonstrating exceptional fire-retardant characteristics. Cone calorimetry tests revealed that the PU composites had a 45.7% lower peak heat release rate and a 35.7% lower smoke release rate than neat PU foam. Additionally, the synchronous thermal analyzer (STA) revealed that the PU foam exhibited potential thermal insulation performance. This study provides a technically feasible and sustainable approach to valorize furfural residue and crude glycerol for producing biopolyols and flame-retardant insulation PU foam.

Production of Bio-Based Polyol from Coconut Fatty Acid Distillate (CFAD) and Crude Glycerol for Rigid Polyurethane Foam Applications.

This study propounds a sustainable alternative to petroleum-based polyurethane (PU) foams, aiming to curtail this nonrenewable resource's continued and uncontrolled use. Coconut fatty acid distillate (CFAD) and crude glycerol (CG), both wastes generated from vegetable oil processes, were utilized for bio-based polyol production for rigid PU foam application. The raw materials were subjected to catalyzed glycerolysis with alkaline-alcohol neutralization and bleaching. The resulting polyol possessed properties suitable for rigid foam application, with an average OH number of 215 mg KOH/g, an acid number of 7.2983 mg KOH/g, and a Gardner color value of 18. The polyol was used to prepare rigid PU foam, and its properties were determined using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis/derivative thermogravimetric (TGA/DTA), and universal testing machine (UTM). Additionally, the cell foam morphology was investigated by scanning electron microscope (SEM), in which most of its structure revealed an open-celled network and quantified at 92.71% open-cell content using pycnometric testing. The PU foam thermal and mechanical analyses results showed an average compressive strength of 210.43 kPa, a thermal conductivity of 32.10 mW·m-1K-1, and a density of 44.65 kg·m-3. These properties showed its applicability as a type I structural sandwich panel core material, thus demonstrating the potential use of CFAD and CG in commercial polyol and PU foam production.

Preparation and Effect of Methyl-Oleate-Based Polyol on the Properties of Rigid Polyurethane Foams as Potential Thermal Insulation Material.

Recently, most of the commercial polyols used in the production of rigid polyurethane foams (RPUFs) have been derived from petrochemicals. Therefore, the introduction of modified palm oil derivatives-based polyol as a renewable material into the formulation of RPUFs is the focus of this study. A palm oil derivative-namely, methyl oleate (MO)-was successfully modified through three steps of reactions: epoxidation reaction, ring-opened with glycerol, followed by amidation reaction to produce a bio-based polyol named alkanolamide polyol. Physicochemical properties of the alkanolamide polyol were analyzed. The hydroxyl value of alkanolamide polyol was 313 mg KOH/g, which is suitable for producing RPUFs. Therefore, RPUFs were produced by replacing petrochemical polyol with alkanolamide polyol. The effects of alkanolamide polyol on the physical, mechanical and thermal properties were evaluated. The results showed that the apparent density and compressive strength increased, and cell size decreased, upon introducing alkanolamide polyol. All the RPUFs exhibited low water absorption and excellent dimensional stability. The RPUFs made with increased amounts of alkanolamide polyol showed higher thermal conductivity. Nevertheless, the thermal conductivities of RPUFs made with alkanolamide polyol are still within the range for thermal insulating materials (<0.1 W/m.K). The thermal stability of RPUFs was improved with the addition of alkanolamide polyol into the system. Thus, the RPUFs made from alkanolamide polyol are potential candidates to be used as insulation for refrigerators or freezers.

Research on modifying of recycling polyol from waste polyurethane foam by vegetable oil for producing insulation materials

Polyurethane (PU) foam is formed by the condensation of 2 components Polyol and Isocyanate. PU foam waste can be recycled by glycolysis which decomposes the polymer chains into polyol. The recycled polyol can then be used as the material to make new PU foam. However, the recycled Polyol is mixed with unprofitable primary and secondary amines, and it is not suitable for use as a raw material for the production of insulating foam because of its small average molecular weight, high hydroxyl index, etc. In this study, recycled Polyol will be modified with vegetable oil for the purpose of removing the amines mentioned above, creating the product with basic properties like commercial Polyol. Research results show that the regenerated Polyol after modification has the low hydroxyl index of 423.5 mg KOH/g and the viscosity of 4400 mPa.s, which are quite similar to that of commercial Polyol and the mass average molecular weight (2440.6) much higher than regenerated polyol.

Influence of Reactive Amine-Based Catalysts on Cryogenic Properties of Rigid Polyurethane Foams for Space and On-Ground Applications.

Rigid polyurethane (PUR) foams have outstanding properties, and some of them are successfully used even today as cryogenic insulation. The fourth-generation blowing agent Solstice® LBA and commercial polyols were used for the production of a low-density cryogenic PUR foam composition. A lab-scale pouring method for PUR foam preparation and up-scaling of the processes using an industrial spraying machine are described in this article. For the determination of the foam properties at cryogenic temperature, original methods, devices, and appliances were used. The properties at room and cryogenic temperatures of the developed PUR foams using a low-toxicity, bismuth-based, and low-emission amine catalyst were compared with a reference foam with a conventional tin-based additive amine catalyst. It was found that the values of important cryogenic characteristics such as adhesion strength after cryoshock and the safety coefficient of the PUR foams formed with new reactive-type amine-based catalysts and with the blowing agent Solstice® LBA were higher than those of the foam with conventional catalysts.

Synthesis and characterization of polyurethane rigid foam by using feedstocks received from renewable and recyclable resources

The mimicry reactions used in the industrial field based on pure materials to obtain products is very important in order to achieve a circular economy and a green environment. This time around, the idea is that all raw materials are wastes. In addition to synthesizing biodiesel, this study aims to synthesize polyurethane rigid foams from recyclable materials such as liquid wastes and solid plastic wastes. The study follows preparation of a new class of biopolyols by reacting a mixture of crude glycerin-based polyol and epoxidized used cooking oil with polyethylene terephthalate, polyurethane, and bisphenol-polycarbonate wastes. Then, fabrication of polyurethane rigid foams by blending synthesized biopolyols with commercial polyol at ratios 20%, 40%, and 60% occurs. The properties of biopolyols and fabricated rigid foams was investigated by nuclear magnetic resonance, infrared spectrometer, thermal gravimetric analyzer, scanning electron microscope, and dynamic mechanical thermal analyzer. The results show that the biopolyols are valuable products for polyurethane manufactures. Moreover, the fabricated rigid foams show nonsignificant changes at the commercial and industrial level.

Hydroxypropylation of Polyphenol-Rich Alkaline Extracts from Pinus radiata Bark and Their Physicochemical Properties.

Pinus radiata bark is a rich source of polyphenols, which are mainly composed of proanthocyanidins. This study aimed to utilize P. radiata bark as a polyol source for bio-foam production in the future. Polyphenol-rich alkaline extracts (AEs) from P. radiata bark were prepared by mild alkaline treatment and then derivatized with propylene oxide (PO). Hydroxypropylated alkaline extracts (HAEs) with varying molar substitutions (MS 0.4-8.0) were characterized by FT-IR, NMR, GPC, TGA, and DSC. The hydroxyl value and solubility in commercial polyols were also determined. The molecular weights of the acetylated HAEs (Ac-HAEs) were found to be 4000 to 4900 Da. Analyses of FT-IR of HAEs and 1H NMR of Ac-HAEs indicated that the aromatic hydroxyl groups were hydroxypropylated and showed an increase in aliphatic hydroxyl group content. The glass transition temperature (Tg) of AE and HAEs were 58 to 60 °C, showing little difference. The hydroxyl value increased as the hydroxypropylation proceeded. Although salts were produced upon neutralization after hydroxypropylation, HAEs still showed suitable solubility in polyether and polyester polyols; HAEs dissolved well in polyether polyol, PEG#400, and solubility reached about 50% (w/w). This indicated that neutralized HAEs could be directly applied to bio-foam production even without removing salts.

Bio-Based Polymer Developments from Tall Oil Fatty Acids by Exploiting Michael Addition.

In this study, previously developed acetoacetates of two tall-oil-based and two commercial polyols were used to obtain polymers by the Michael reaction. The development of polymer formulations with varying cross-link density was enabled by different bio-based monomers in combination with different acrylates—bisphenol A ethoxylate diacrylate, trimethylolpropane triacrylate, and pentaerythritol tetraacrylate. New polymer materials are based on the same polyols that are suitable for polyurethanes. The new polymers have qualities comparable to polyurethanes and are obtained without the drawbacks that come with polyurethane extractions, such as the use of hazardous isocyanates or reactions under harsh conditions in the case of non-isocyanate polyurethanes. Dynamic mechanical analysis, differential scanning calorimetry, thermal gravimetric analysis, and universal strength testing equipment were used to investigate the physical and thermal characteristics of the created polymers. Polymers with a wide range of thermal and mechanical properties were obtained (glass transition temperature from 21 to 63 °C; tensile modulus (Young’s) from 8 MPa to 2710 MPa and tensile strength from 4 to 52 MPa). The synthesized polymers are thermally stable up to 300 °C. The suggested method may be used to make two-component polymer foams, coatings, resins, and composite matrices.

A Fully Biobased Aromatic Polyester Polyol for Polyisocyanurate Rigid Foams: Poly(diethylene furanoate)

Aromatic polyester polyols are often used in polyurethane rigid foam (PUR) and polyisocyanurate (PIR) synthesis, since they offer higher rigidity than polyether polyols. Herein, a route toward fully biobased aromatic polyester polyols was investigated using sugar-based 2,5-furandicarboxylic acid (FDCA) and diethylene glycol (DEG), enabling a direct one-step synthesis of a fully biobased aromatic polyester polyol, poly(diethylene furanoate) (PDEF), for applications in PIR rigid foam. Therefore, reaction conditions were optimized to obtain PDEF as a processable polyol with OH values and remaining unreacted DEG similar to a commercial, petroleum-based polyol. The processability was improved by either copolymerizing 10–20 mol % of a biobased aliphatic dicarboxylic acid, like succinic acid (SA) or adipic acid (AA), maintaining the fully biobased character of the polyol, or copolymerization with phthalic acid. The fully biobased polyester polyols were successfully prepared on a 100 g scale of dicarboxylic acids. Subsequent application in PIR rigid foam showed similar density, thermal conductivity, flame behavior, and compressive strength if compared to the rigid foam obtained from a commercial polyol. Thus, fully biobased PDEF can substitute petroleum-based aromatic polyester polyols in PIR applications.

A Comparative Study on Bio-Based PU Foam Reinforced with Nanoparticles for EMI-Shielding Applications.

Today, most commercial polyols used to make polyurethane (PU) foam are produced from petrochemicals. A renewable resource, castor oil (CO), was employed in this study to alleviate concerns about environmental contamination. This study intends to fabricate a bio-based and low-density EMI-defending material for communication, aerospace, electronics, and military appliances. The mechanical stirrer produces the flexible bio-based polyurethane foam and combines it with nanoparticles using absorption and hydrothermal reduction processes. The nanoparticles used in this research are graphite nanoplates (GNP), zirconium oxide (ZrO2), and bamboo charcoal (BC). Following fabrication, the samples underwent EMI testing using an EMI test setup with model number N5230A PNA-L. The EMI experimental results were compared with computational simulation using COMSOL Multiphysics 5.4 and an optimization tool using response surface methodology. A statistical design of the experimental approach is used to design and evaluate the experiments systematically. An experimental study reveals that a 0.3 weight percentage of GNP, a 0.3 weight percentage of ZrO2, and a 2.5 weight percentage of BC depict a maximum EMI SE of 28.03 dB in the 8–12 GHz frequency band.

Recovery of Green Polyols from Rigid Polyurethane Waste by Catalytic Depolymerization.

Polyurethane (PU) is one of the most versatile polymers available and can be found in an infinite number of formats ranging from rigid or flexible foams to elastomers. Currently, most Rigid PU Foam (RPUF) waste is landfilled, even though a small amount is mechanically recycled, in which the material is conditioned in size to a very fine powder, which is introduced as a filler. In this work, chemical recycling of two types of rigid PU foams is studied, the major difference being the aliphatic or aromatic nature of the isocyanate used in the synthesis. A solvolysis process is developed, a chemical depolymerization that breaks the chains by means of a chemical agent, a solvent, in the presence of a catalyst and under controlled process conditions. The glycolysis products are purified by vacuum distillation, centrifugation, and acid water treatment, depending on the most suitable process for each waste type. Optimal process conditions are established to obtain high-purity green polyols by performing a set of catalytic glycolysis reactions at laboratory scale with the previously conditioned RPUF waste samples. The physicochemical properties of the polyols, such as hydroxyl value, acid value, average molecular weight (Mn), and viscosity, are analyzed. The chemical structure and thermal stability of the polyols are studied by means of FTIR and TGA, respectively. Partial substitution of the commercial polyol (up to 15 wt.%) by the recycled polyols for RPUF synthesis is studied and characterized.

Synthesis and Characterization of Wood Rigid Polyurethane Composites.

Incorporating biodegradable reinforcement, such as wood particles, into rigid polyurethane foams (RPUFs) is among the alternatives to reduce their environmental impact. This study aims to assess the effect of different wood particles as reinforcement in RPUFs. Reinforced rigid polyurethane foams are synthesized with milled wood particles of various forms and sizes and commercial polyol and isocyanate. The effect of fiber treatments and mechanical stirring on foams’ properties is also studied. Additional tests on polyisocyanurate foams (PIR) were undertaken to assess the effect of reinforcement on their properties. Mechanical properties are measured to investigate the impact of wood particle reinforcement on the foam. Confocal microscopy and Fourier-transform infrared spectroscopy (FTIR) showed the interaction between the wood fibers and the matrix. Despite the adhesion observed for some fibers, most of the cell walls of RPUFs were punctured by the rigid wood fibers, which explained the decrease in the compressive strength of the composites for manually mixed foams. Mechanical stirring proved to be an efficient method to enhance the reinforcement power of untreated fibers. RPUF foams’ properties showed similar changes when untreated wood flour was introduced to the formula, increasing compressive strength significantly.

Rational analysis of dispersion and solubility of Kraft lignin in polyols for polyurethanes

The incorporation of Kraft lignin (KL) in polyurethanes has received much academic and industrial attention due to its potential for sustainably improving broader property profiles. However, the consistency in physical properties improvement is still challenging. The missing link in this field is the compatibility of KL with polyols and the major unanswered question is ‘how does lignin choose to disperse in polyols?’. This study reports the solubility of KL dispersed in ethylene oxide (EO) diols, propylene oxide (PO) diols, commercial polyols containing EO or PO and a standard crosslinker (glycerol) at room temperature, and rationally evaluates compatible polyol/lignin systems based on microscopic, gravimetric, and rheological analyses for potential application in polyurethanes. The degree of dispersion of KL in polyols was observed to vary from low to high with polydispersity in particle size depending on the chemical structure (functionality, solubility parameter, polarity) and molecular weight of polyols. While low molecular weight diols have shown high solubility of KL, the EO-based polyols have shown relatively better compatibility with KL than the PO-based polyols and glycerol. By exploring the various degrees of dispersion of KL in polyols, this study suggests that the polyurethane materials could be engineered with KL through judicious selection of compatible polyol based on structure, solubility parameter, and molecular weight.

Synthesis of Rigid Polyurethane Foams Incorporating Polyols from Chemical Recycling of Post-Industrial Waste Polyurethane Foams.

The preparation and characteristics of rigid polyurethane foams (RPUFs) synthesized from polyols obtained by glycolysis of post-industrial waste RPUFs have been studied. More precisely, waste rigid foams that have been chemically recycled by glycolysis in this work are industrially produced pieces for housing and bracket applications. The glycolysis products have been purified by vacuum distillation. The physicochemical properties of the polyols, such as hydroxyl value, acid value, average molecular weight (Mn) and viscosity have been analyzed. The chemical structure and thermal stability of the polyols have been studied by means of FTIR and TGA, respectively. Partial substitution of the commercial polyol (up to 15 wt.%) by the recycled polyols increases the reactivity of the RPUFs synthesis, according to short characteristic times during the foaming process along with more exothermic temperature profiles. Foams formulated with recycled polyols have a lower bulk density (88.3–96.9 kg m−3) and smaller cell sizes compared to a conventional reference RPUF. The addition of recycled polyols (up to 10 wt.%) into the formulation causes a slight decrease in compressive properties, whereas tensile strength and modulus values increase remarkably.

Green rigid polyurethane foam from hydroxyl liquid natural rubbers as macro-hydroxyl polyols

The novel renewable source precursors from hydroxyl liquid natural rubbers (HLNRs) with various secondary hydroxyl content of 22% (HLNR22), 35% (HLNR35), and 50% (HLNR50) (or naming macro-hydroxyl polyols) were used to prepare rigid polyurethane foam. The aim of this study was to investigate the effect of hydroxyl content of HLNR precursors and the ratio of HLNRs and commercial polyols on physico-mechanical properties of rigid polyurethane foams in comparison to foams made from commercial polyols. The increase in hydroxyl content of HLNRs resulted in the foams with larger cell size while the increase in the HLNR portion caused a small and more uniform cell size, which is related to their density and compressive strength. Thermal stability of polyurethane foams was analyzed by thermogravimetric analysis and the results have demonstrated that the use of HLNR polyols improved thermal stability of polyurethane foams in comparison to commercial foam.

Pre-Treatment of Used Cooking Oil Followed by Transesterification Reaction in the Production of Used Cooking Oil-Based Polyol

Used cooking oil has been considered as an economical and sustainable material that can be used widely as a starting material in the production of polymer precursors such as polyol for polyurethane. Since the composition of fatty acids and glyceride in the structure of used cooking oil remain the same as virgin vegetable oil, used cooking oil can be synthesized using the same method. However, there are certain physicochemical modifications to the oil properties that arise during the process of oil fryings such as increases in viscosity, acid value, and color changes that will affect the conversion of used cooking oil into bio-based polyol. Thus, various pretreatment methods that can be applied to used cooking oil such as adsorption, chemical bleaching, and treatment with solvents will be reviewed in this paper. Transesterification of used cooking oil with alcohol in the presence of catalyst will produce used cooking oil-based polyol which will have two or more hydroxyl groups per molecule. The formation of polyol can be confirmed with the formation of O-H peak in the FTIR spectrum during the FTIR spectroscopy analysis. This paper will also discuss the type of alcohol and catalyst used in the transesterification reaction. Used cooking oil-based polyol obtained from transesterification reaction has been reported to be comparable to the commercial polyol.

Effects of high functionality polyol on the structure and properties of rigid polyurethane foam

ABSTRACT High performance rigid polyurethane foam (RPUF) has been designed by using hyperbranched polyurethane (HBPU) polyol with high functionality to replace traditional polyol. The influences of different types of polyol on the apparent density and heat deformation temperature of RPUF were studied. The microstructures, including cell structure, cell diameter and distribution, were characterised by SEM. Effects of polyol types on the cell structure of RPUF were discussed. Thermal resistance and thermal stability were measured by the thermal deformation vicat temperature meter and TGA. Thermal conductivity of RPUF was characterised by Hot Disk, and the mechanical properties were also measured. Compared with the RPUFs obtained from commercial polyether polyols, RPUF-HBPU exhibited enhanced thermal resistance. Besides, the compressive strength, flexural strength and tensile strength were up to 4.5, 4 and 3.5 times, respectively, than that of traditional RPUF as well. The as-prepared RPUF-HBPU displayed low thermal conductivity/thermal diffusion and good thermal stability.