Reinforcement of agricultural wastes liquefied polyols based polyurethane foams by agricultural wastes particles

Four kinds of agricultural wastes particles (XS: oilseed rape straw [OS], rice straw [RS], wheat straw [WS], and corn stover [CS]) were used to reinforce agricultural wastes liquefied polyol (P-XS) based polyurethane (PU) foam. Different XS loading dosages (0% ~ 15%) are investigated to confirm suitable filler concentrations for modifying foams. RS particles show great promoting ability, OS particles reveal complex influence, while WS and CS particles display mild effect on foaming process. With 1% of OS, 6% of RS, 3% of WS, or 1% of CS incorporating in matrix materials, the reinforced foam could keep applicable density, reach better physical and mechanical property, display more uniform cellular structure, and show higher thermal stability with more excellent water absorption ability. Using of agricultural wastes as polymer filler is economical, simple, environmental, and wide applicable for biomass utilization and biopolymer preparation.     

Sustainable rigid polyurethane foams based on recycled polyols from chemical recycling of waste polyurethane foams

The preparation and characteristics of rigid polyurethane foams (RPUFs) based on recycled polyol obtained by glycolysis of waste RPUF scraps from end-of-life refrigerators were investigated. To deactivate the amine adducts derived from isocyanates, the recycled product obtained after depolymerization was chemically modified via addition polymerization of propylene oxide. Two kinds of recycled polyols with different hydroxyl values and viscosity were blended with conventional virgin polyether polyol to prepare the RPUFs. The effects of the recycled polyols on the physical properties of RPUFs such as cell structures, compressive strength, thermal conductivity, and limiting oxygen index were discussed. It was found that the RPUFs from recycled polyols showed superior compressive strength, thermal insulation property, and self-extinguishing property compared with conventional control foam. The results of this study reveal that the recycled polyols could be used as feedstock for RPUFs with superior performance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47916.     

Effect of storage time on the characteristics of a waterborne polyurethane/tetraethoxysilane mixture and the properties of prepared films

Waterborne polyurethane (WPU) is one of the most important resins. The properties of WPU can be modified by introducing inorganic components. Tetraethoxysilane (TEOS) is a precursor for preparing inorganic polymers and can be used to prepare WPU/silica hybrids. In this study, WPU dispersion was synthesized by reacting polytetramethylene ether glycol and dimethylolpropionic acid with isophorone diisocyanate, followed by chain extension with ethylenediamine. After mixing WPU with TEOS, the mixture was sealed and stored at room temperature for different lengths of times. The influence of time on the characteristics of the WPU/TEOS mixture and the properties of films were investigated. The results showed that the viscosity, surface tension and average particle size of the mixture increased with prolonged storage time. ²⁹Si-NMR analysis indicated that the structure of silica exists in the WPU film. DSC, DMA and TGA results showed that WPU/silica films made from the mixture have less thermal activity, higher storage modulus, lower damping peak heights and better heat resistance after relatively long storage times.     

Thermal degradation kinetics of rigid polyurethane foams blown with water

The thermal decomposition behavior of rigid polyurethane foams blown with water was studied by dynamic thermogravimetric analysis (TGA) in both nitrogen and air atmosphere at several heating rates ranging from room temperature to 800°C. The kinetic parameters, such as activation energy (E), degradation order (n), and pre‐exponential factor (A) were calculated by three single heating rate techniques of Friedman, Chang, and Coats–Redfern, respectively. Compared with the decomposition process in nitrogen, the decomposition of foams in air exhibits two distinct weight loss stages. The decomposition in nitrogen has the same mechanism as the first stage weight loss in air, but the second decomposition stage in air appears to be dominated by the thermo‐oxidative degradation. The heating rates have insignificant effect on the kinetic parameters except that the kinetic parameters at 5°C/min have higher values in nitrogen and lower values in air, indicating different degradation kinetics in nitrogen and air. The kinetic parameters of foam samples blown with different water level in formulation decline firstly and then increase when water level increases from 3.0 to 7.0 pph. According to the prediction for lifetime and half‐life time of foams, water‐blown rigid foams have excellent thermostability, when used as insulation materials below 100°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:4149–4156, 2006     

Renewable chemical feedstocks from peanut shell liquefaction: Preparation and characterization of liquefied products and residue

The objective of this investigation is to liquefy peanut shell for the preparation of aromatic polyol‐rich products. The influences of reaction parameters are discussed. It is found that, compared to single‐solvent, the mixture of polyethylene glycol and glycerol as solvents shows higher liquefaction efficiency. And the maximum liquefaction yield of 98.7 wt % can be achieved when the sulfuric acid content, mass ratio between polyethylene glycerol, glycerol, and peanut shell powder, liquefaction temperature, and time are 17 wt % (relative to peanut shell), 8/2/1, 150 °C, and 2 h, respectively. Furthermore, the solubility test result indicates that the liquefied products are fully soluble in the water and polyol. Meanwhile, the properties of the peanut shell and liquefaction residue were analyzed by means of attenuated total reflectance‐Fourier transform infrared spectroscope, thermal gravity analysis, and scanning electron microscope. The polysaccharide is degraded by the cleaving of C–O bond, and the lignin is decomposed by leaving the dominant linkages including β‐O‐4, 4‐O‐5, and dibenzodioxocin units. The fibers in the peanut shell are broken, and the nondegraded components in the residue lost their network structure. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44162.     

Synthesis and characterization of eugenol-based silicone modified waterborne polyurethane with excellent properties

A eugenol-based silicone-containing monomer 4,4′-(1,1,3,3-tetramethyldisiloxane-1,3-dipropyl)bis-2-methoxyphenol(EUSi) was synthesized from eugenol and 1,1,3,3-tetramethyldisiloxane via the hydrosilylation reaction. And waterborne polyurethane (WPU) with excellent properties was obtained by using EUSi as a type of diol chain extender. The unique combination of rigidity and flexibility in the chemical structure of EUSi greatly facilitated the mechanical properties, thermal properties, and water resistance of WPU. With only a 3% dosage of EUSi, the maximum tensile strength was increased from 6.2 to 22.4 MPa, while the water absorption was decreased from 31.3% to a surprisingly 7.6%. Our work provides a new convenient strategy for the preparation of organosilicon-modified WPU with improved performance.     

Physical properties of water‐blown rigid polyurethane foams from vegetable oil‐based polyols

Fifty vegetable oil‐based polyols were characterized in terms of their hydroxyl number and their potential of replacing up to 50% of the petroleum‐based polyol in waterborne rigid polyurethane foam applications was evaluated. Polyurethane foams were prepared by reacting isocyanates with polyols containing 50% of vegetable oil‐based polyols and 50% of petroleum‐based polyol and their thermal conductivity, density, and compressive strength were determined. The vegetable oil‐based polyols included epoxidized soybean oil reacted with acetol, commercial soybean oil polyols (soyoils), polyols derived from epoxidized soybean oil and diglycerides, etc. Most of the foams made with polyols containing 50% of vegetable oil‐based polyols were inferior to foams made from 100% petroleum‐based polyol. However, foams made with polyols containing 50% hydroxy soybean oil, epoxidized soybean oil reacted with acetol, and oxidized epoxidized diglyceride of soybean oil not only had superior thermal conductivity, but also better density and compressive strength properties than had foams made from 100% petroleum polyol. Although the epoxidized soybean oil did not have any hydroxyl functional group to react with isocyanate, when used in 50 : 50 blend with the petroleum‐based polyol the resulting polyurethane foams had density versus compressive properties similar to polyurethane foams made from 100% petroleum‐based polyol. The density and compressive strength of foams were affected by the hydroxyl number of polyols, but the thermal conductivity of foams was not. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Rigid polyurethane foams derived from cork liquefied at atmospheric pressure

The aim of this study was to evaluate the possibility of using polyols derived from liquefied cork in the production of novel bio‐based polyurethane foams (PUFs). For that purpose, different liquefaction conditions were used at atmospheric pressure and moderate temperature where poly(ethylene glycol) and glycerol were used as solvents and sulfuric acid as catalyst. The ensuing polyols were used to produce foams which were characterized using structural, morphological, thermal and mechanical analyses to demonstrate that liquefaction conditions play a crucial role in the properties of the foams. The resulting foams exhibited the typical cellular structure of PUFs with low densities (57.4–70.7 kg m^?3) and low thermal conductivities (0.038–0.040 W m^?1 K^?1). However, the mechanical properties differed significantly depending on the liquefaction conditions. The best stress–strain results were obtained for PUFs prepared using the polyol with lowest I_OH and water content (Young's modulus of 475.0 kPa, compressive stress (σ_10%) of 34.6 kPa and toughness of 7397.1 J m^?3). This PUF was thermally stable up to 200 °C and presented a glass transition temperature of around 27 °C. The results obtained demonstrate that these polyols from liquefied cork yield PUFs that are adequate materials for insulation applications. © 2014 Society of Chemical Industry     

Preparation of polyurethane foams using fractionated products in liquefied wood

Liquefaction of sawdust was studied using glycerol and methanol as mix solvents. A new bio‐polyol product consisting of high purity multi‐hydroxy compounds was obtained by precipitation of the hydrophobic organics from the liquefied product in an aqueous solution. As identified by GC‐MS, the dominate components in bio‐polyol were glycerol, glycerol derivatives, and multiple types of sugar derivatives. By using the mass ratio of m (sawdust) : m (glycerol) = 1 : 1, the total content of multi‐hydroxy compounds reached 90.84%. The hydroxyl number of the bio‐polyol was 1287 mgKOH/g with a rotational viscosity of 1270 cP. Preparation of polyurethane foams using bio‐polyol and isocyanate was also studied. Water was used as an environmental friendly blowing agent. The factors that influence the cell structure of foams (i.e., catalyst, dosage of blowing agent, and mass ratio of bio‐polyol to PEG‐400 were studied. The compressive strength of the synthesized foam was 150 Kpa, which met the requirement of Chinese specification for rigid foams. The synthesized foams were characterized by FTIR, SEM, and TG. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40096.     

The effect of component addition order on the properties of epoxy resin/polyurethane resin interpenetrating polymer network structure

Epoxy resin (ER) is one of the most important synthetic resins, but it has the disadvantage of lacking impact resistance. However, it can be improved by mixing with polyurethane resin (PU). In this study, Epon 828, triethylenetetramine (TETA), polytetramethylene ether glycol (PTMG), isophorone diisocyanate (IPDI), and dibutyltin dilaurate (DBTDL) were used as raw materials to prepare ER/PU interpenetrating polymer network structures (IPNs) by three different blending processes. The results showed the reactivity between TETA and IPDI were greater than that between TETA and ER. When ER/TETA/PTMG/IPDI/DBTDL were mixed at the same time, or ER and PU resins were prepared separately and then mixed, the ER/PU composites produced had a phase separation inside the structure. The most appropriate blending method was to mix ER with PTMG, IPDI, DBTDL first, and then add TETA after 10 min. The composite formed had a uniform appearance, and had better physical, mechanical, and thermal properties than the others did.     

Degradable polyurethane foams based on disaccharides

New functional elastic polyurethane foams (PUF) degradable under environmental abiotic and biotic factors, retaining all the inherent properties of the conventional foams were synthesized using isocyanate precursors based on disaccharides (DS): lactose, maltose and saccharose. It was shown by the model reactions of monosaccharide glucose, and DS lactose and saccharose, with phenylisocyanate that both the primary and secondary hydroxyls of the carbohydrates reacted to form urethanes. The main properties of DS‐based foams (PUF/DS) were found to be similar to PUF foam (matrix) prepared with conventional polyols. However, the new PUF/DS were found to undergo enhanced acid/alkaline hydrolysis and degradation compared with PUF matrix when incubated in soil. Mass losses of incubated PUF/DSs significantly exceeded the actual carbohydrate content 28.6%, and in 12 months reached 39.58 (PUF‐4), 53.31(PUF‐8), and 47.25 (PUF‐12). In contrast, under the same conditions PUF matrix lost only 2–2.5%, confirming that incorporation of natural compounds into the polymer chain impacted the degradation processes. PUF/DS were characterized by FTIR, ¹H NMR, ebullioscopy, and exclusion chromatography (molecular masses and molecular mass distribution of the oligomeric model), physical and mechanical tests (density, tensile strength, relative elongation, moisture absorption, vapor permeability), morphology, and degradation in the soil. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42131.     

Climate‐friendly polyurethane blowing agent based on a carbon dioxide adduct from palmitic acid grafted polyethyleneimine

To explore a new blowing agent for polyurethanes (PUs), palmitic acid was grafted onto a branched polyethyleneimine (bPEI; weight‐average molecular weight = 25,000 Da) via N,N′‐carbonyldiimidazole condensation to form a hydrophobically modified bPEI [palmitic acid grafted branched polyethyleneimine (C₁₆–bPEI)] with a grafting rate of 12%. A CO₂ adduct of C₁₆–bPEI, which trapped 16.8% CO₂ in it, was synthesized from C₁₆–bPEI. The long alkyl chain grafting improved the dispersibility of the CO₂ adduct in the PU raw materials and favored a homogeneous release of CO₂ to blow PUs during the exothermic foaming process. The preliminary results show that the foams possessed a density of 72.0 kg/m³ and a compressive strength of 246 kPa; this matched the required values of foams for the thermal insulation of underground steel pipes. This new blowing agent emitted nothing but CO₂ to the atmosphere, so it will not promote ozone depletion and will avoid global warming problems that are associated with traditional blowing agents such as chlorofluorocarbons and hydrochloroflourocarbons. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43874.     

Thermal degradation studies on rigid polyurethane foams blown with pentane

The effect of sodium dihydrogenphosphate, trisodium pyrophosphate, and sodium aluminocarbonate on the thermal decomposition of rigid polyurethane (PUR) foams, based on diphenylmethane‐4,4‐diisocyanate, diphenyl‐2,2‐propane‐4,4‐dioxyoligo(ethylene oxide), and oxyalkylenated toluene‐2,6‐diamine, blown with pentane, was studied. Thermogravimetric (TG) data have shown that there is a stabilization effect of additives in the initial stage of degradation, both in nitrogen and air atmosphere, and the decomposition proceeded in two steps up to 600°C. Results of the kinetic analysis by the isoconversional methods of Ozawa–Flynn–Wall and Friedman yielded values of (apparent) activation energy (E_a) and preexponential factor (A). For phosphate‐stabilized PUR samples, E_a remained stable over a broad area of the degree of conversion, while for carbonate‐containing sample two regions of E_a were observed. Further advanced kinetic analysis by a nonlinear regression method revealed the form of kinetic function that was the best approximation for experimental data—for a two‐stage consecutive reaction the first step was the Avrami–Erofeev nucleation‐dependent model, and the second step was a chemical reaction (1st or nth order) model. The integrated thermogravimetric (TG)/Fourier transform infrared (FTIR) technique probed the thermal degradation of modified PURs by analyzing the evolved gases. The solid residue remaining at different temperatures was identified by diffuse reflection FTIR (Kubelka–Munk format). The complex thermal behavior was discussed on the basis of the obtained results—it can be shown that the global stabilization effect is a multistage process whose initial conditions are of critical importance in governing the nature of the entire process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2319–2330, 2003     

Synthesis and properties of magnetite nanoparticles with peroxide-containing polymer shell and nanocomposites based on them

Magnetite nanoparticles (Fe₃O₄ NPs) with peroxide-containing polymer shell have been synthesized using the method of coprecipitation from the mixture solutions of Fe (II) and Fe (III) salts in the presence of peroxide-containing copolymer (PCC). Polymer shell presence has been proved by elemental and complex thermal analysis. Synthesized Fe₃O₄ NPs possess superparamagnetic properties. Their specific saturation magnetization decreases gradually from 65 to 54 A·m²·kg⁻¹ with increasing PCC concentration owing to the surface spin pinning effect caused by a polymer shell. The average sizes of Fe₃O₄ NPs estimated from the data of XRD analysis and magnetic measurements are in the range of 9–12 nm. The NP sizes determined by the DLS method lie in the range of 150–270 nm; this result is significantly larger than the sizes estimated by the two aforementioned methods evidencing a tendency for Fe₃O₄ NPs toward self-association. Cross-linked composite films based on polyvinyl alcohol have been obtained via radical curing initiated by the PCC shell of nanoparticles. The resulting composite films are magnetically sensitive films with rather high physico-mechanical properties (tensile strength reaches 48–67 MPa and relative elongation – 4%–21% depending on cross-linking degree), a priori non-toxic and biocompatible, which makes them promising materials for various applications.     

Effect of monomer temperature on foaming and properties of flexible polyurethane foams

Polyurethane foam formation involves simultaneous polymerization and expansion. In an open cell foam, foam lamellae rupture at some stage of foam formation, resulting in a foam with continuous air channels. Experiments are carried out to study the effect of initial temperature of monomers on the open cell content of water‐blown flexible polyurethane foams. The change in kinetics of the polymerization and blowing with initial monomer temperature is noted by measuring the gel and rise times during foaming. Both polymerization and blowing reactions are found to be faster with increasing monomer temperature. The cell size is found to increase with initial monomer temperature, and the height of the cured free rise foam is found to decrease. The open cell content of the foam increased considerably with initial monomer temperature, leading finally to the collapse of the foam at the highest temperatures studied. The mechanical properties of the foam at different monomer temperatures are determined by making molded foams. The indentation load deflection decreased with increasing monomer temperature indicating the formation of softer foams, but showed a slight increase near the temperature of collapse. Other mechanical properties showed a small degradation with increase in initial monomer temperatures. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation and characterization of water‐blown polyurethane foams from liquefied cornstalk polyol

Polyurethane foams were prepared from the liquefied cornstalk polyol, which was obtained by the liquefaction of cornstalk in the presence of polyhydric alcohols using sulfuric acid as catalyst. The advisable liquefaction reaction conditions were selected by investigating their influences on the properties of liquefied cornstalk polyol, taking account of the requirement for the preparation of appropriate polyurethane foams. The influences of the contents of catalysts, water, surfactant, and isocyanate on the properties of polyurethane foams were also discussed, and feasible formulations for preparing cornstalk‐based polyurethane foams were proposed. The results indicated that the foams prepared from such liquefied cornstalk polyol exhibited excellent mechanical properties and thermal properties, and could be used as heat‐insulating materials. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Surface‐modifiers of clay on mechanical properties of rigid polyurethane foams/organoclay nanocomposites

Three different surface modifiers, octadecyl trimethyl ammonium (ODTMA), octadecyl primary ammonium (ODPA), and decanediamine (DDA) were used to modify Na⁺? montmorillonite (MMT), and the resultant organoclays were coded as ODTMA‐MMT, ODPA‐MMT, DDA‐MMT, respectively. Rigid PU foams/organoclay composites were prepared by directly using organoclay as the blowing agent without the addition of water. Investigation shows that the morphology of the nanocomposites is greatly dependent on the surface modifiers of clay used in the composites. In detail, DDA‐MMT is partially exfoliated in the PU matrix with the smallest cell size, while two others are intercalated in the PU matrices with smaller cell sizes. The sequence of their cell sizes is pristine PU foams > rigid PU foams/ODTMA‐MMT > rigid PU foams/ODPA‐MMT > rigid PU foams/DDA‐MMT, and the average cell size of rigid PU foams/DDA‐MMT composites decreases evidently from 0.30 to 0.07 mm. Moreover, all rigid PU foams/organoclay composites show remarkable enhanced compressive and tensile strengths as well as dynamic properties than those of PU foams, and the enhancement degree coincides well with the relative extent of internal hydrogen bonding of materials and gallery spacing of organoclay. For example, in the case of rigid PU foams/DDA‐MMT composite, 214% increase in compressive strength and 148% increase in tensile strength compared with those of pure PU foams were observed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Desaminated glycolysis of water‐blown rigid polyurethane foams

Glycolysis reaction kinetics of methylene diphenyl diisocyanate‐based water‐blown polyurethane foams was examined by gel permeation chromatography. Glycolysates were reacted with butyl glycidyl ether to convert toxic aromatic amines to polyols, and their products were identified by ¹H‐NMR spectroscopy. To examine the quality of recycled polyol, polyurethane foams were reprepared using the virgin and recycled polyol mixtures with varying compositions. Cell structures and sizes of reprepared foams were similar to those of original ones when the recycled polyols were mixed up to 30 wt %. Density, thermal conductivity, and flexural strength of the reprepared foams were compared with those of the original ones, and no difference was observed below the recycled polyol concentration of 30 wt %. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2646–2656, 2000     

疏水花生壳/聚氨酯复合泡沫的制备与油水分离性能

为提高聚氨酯泡沫（PUF）的疏水性能,首先采用十六烷基三甲氧基硅烷（HDTMS）对花生壳粉末（PSP）进行改性,得到疏水改性花生壳粉末（H-PSP）。水接触角测试结果表明,改性后H-PSP的水接触角由PSP的0°提高至145.2°。然后采用预聚体法制备了PUF负载H-PSP复合材料（H-PSP-PUF-n,n为H-PSP占聚氨酯预聚体PPU的质量分数）。对H-PSP-PUF-n的结构和性能进行了表征与测试。结果表明,H-PSP的负载提高了泡沫材料的表面粗糙度和力学性能,H-PSP的最佳负载量为PPU质量的10%（H-PSP-PUF-10）。与PUF相比,H-PSP-PUF-10的静态水接触角达到142.4°,较PUF提高了50.4°。对二氯甲烷、石油醚、煤油、二甲苯、环己烷五种油品进行油水分离实验,结果表明,H-PSP-PUF-10对不同油品的吸油倍率在7~9 g/g,而且具有良好的油水选择性。经15次吸附-脱附循环后,H-PSP-PUF-10对各油品的吸油倍率在6.5~8.0 g/g,具有良好的循环利用性。     

疏水花生壳/聚氨酯复合泡沫的制备与油水分离性能

为提高聚氨酯泡沫（PUF）的疏水性能，首先，采用十六烷基三甲氧基硅烷（HDTMS）对花生壳粉末（PSP）进行改性，得到疏水改性花生壳粉末（H-PSP）。水接触角测试结果表明，改性后H-PSP的水接触角由PSP的0°提高至145.2°。然后，采用预聚体法制备了PUF负载H-PSP复合材料[H-PSP-PUF-n,n为H-PSP占聚氨酯预聚体（PPU）质量的百分数]。对H-PSP-PUF-n的结构和性能进行了表征与测试。结果表明，H-PSP的负载提高了泡沫材料的表面粗糙度和力学性能，H-PSP的最佳负载量为PPU质量的10%（标记为H-PSP-PUF-10）。与PUF相比，H-PSP-PUF-10的静态水接触角达到142.4°，较PUF提高了50.4°。对二氯甲烷、石油醚、煤油、二甲苯、环己烷进行油水分离实验，结果表明，H-PSP-PUF-10对石油醚、煤油、二甲苯、环己烷的吸油倍率在7～9 g/g，而且具有良好的油水选择性。经15次吸附-脱附循环后，H-PSP-PUF-10对各油品的吸油倍率在6.5～8.0 g/g，具有良好的循环利用性。