Effects of liquid‐type silane additives and organoclay on the morphology and thermal conductivity of rigid polyisocyanurate‐polyurethane foams

This article investigates the effects of liquid‐type silane additives and organoclay as a solid‐type additive on the morphological, mechanical and thermal insulating properties of polyisocyanurate‐polyurethane (PIR‐PUR) foams. The organoclay likely acted as nucleating agents during the formation of PIR‐PUR foams. When the liquid silane additives and organoclay were added, the cell size and thermal conductivity of the PIR‐PUR foams appeared to be decreased. However, organoclay did not contribute to reduce the cell size distribution of the foam. PIR‐PUR foams synthesized with tetramethylsilane as a liquid‐type additive showed a smaller average cell size and lower thermal conductivity than that of PIR‐PUR foams synthesized with the other silane additives or with organoclay as a solid‐type additive. For the PIR‐PUR foam with organoclay/TEMS (1.5/1.5 php) mixture, cell size and thermal conductivity of the foam showed similar to the foam with TEMS. These results suggest that smaller cell size appears to be one of the major factors in the improvement of thermal insulation properties of the PIR‐PUR foams. Silane additives did not seem to have a strong effect on the flammability of the PIR‐PUR foams. However, heat resistance was more dominant for the foam with the organoclay at the higher temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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     

Properties of rigid polyurethane foams prepared from recycled aircraft deicing agent with hexamethylene diisocyanate

Polyurethane (PUR) rigid foams were prepared from recycled aircraft deicing agent (aircraft deicing fluid) with reaction of hexamethylene diisocyanate at temperature of 55°C. The effect of [NCO]/[OH] ratio on properties of microscopic structure, cell size distribution, compressive strength, apparent density, as well as thermal conductivity (k) was studied. Higher [NCO]/[OH] ratio helped achieve better micromorphology, higher apparent density, and compressive strength of the PUR foams. With the [NCO]/[OH] ratio of 0.75 and 0.8, some shrinking happened during foam rising, causing a decrease in total volume of the PUR foam, and leading to higher apparent density as well as sharply increased compressive strength. All PUR foams displayed good thermal insulation properties in this study. With [NCO]/[OH] ratio increased from 0.7 to 0.8, the k value increased significantly from 34.3 to 42.2 mW m^?1 K^?1. The k value here was chiefly governed by the apparent density of the foams, which was in turn a function of the ratio of [NCO]/[OH]. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci., 2013     

New polyol for production of rigid polyurethane‐polyisocyanurate foams,Part 2: Preparation of rigid polyurethane‐polyisocyanurate foams with the new polyol

The method of preparation, determination of foaming parameters, and methods for the determination of physicochemical properties of polyurethane‐polyisocyanurate (PUR‐PIR) foams prepared with the use of N,N′‐di(methyleneoxy‐2‐hydroxyethyl)urea and boric acid derivatives are presented in this paper. It was found that application of the borate as a polyol component and simultaneously as a flame retardant in the recipe for production of PUR‐PIR foams was very favorable. The foams prepared were characterized by reduced brittleness, higher compressive strength and content of closed cells, as well as considerably lower flammability in comparison with standard foam. The results show that the new polyol prepared on the basis of N,N′‐di(methyleneoxy‐2‐hydroxyethyl)urea and boric acid can be applied for production of rigid PUR‐PIR foams, and it improves their physicochemical properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Reinforcement of soy polyol‐based rigid polyurethane foams by cellulose microfibers and nanoclays

Water‐blown rigid polyurethane foams from soy‐based polyol were prepared and their structure–property correlations investigated. Cellulose microfibers and nanoclays were added to the formulations to investigate their effect on morphology, mechanical, and thermal properties of polyurethane foams. Physical properties of foams, including density and compressive strength, were determined. The cellular morphologies of foams were analyzed by SEM and X‐ray micro‐CT and revealed that incorporation of microfibers and nanoclays into foam altered the cellular structure of the foams. Average cell size decreased, cell size distribution narrowed and number fractions of small cells increased with the incorporation of microfibers and nanoclays into the foam, thereby altering the foam mechanical properties. The morphology and properties of nanoclay reinforced polyurethane foams were also found to be dependent on the functional groups of the organic modifiers. Results showed that the compressive strengths of rigid foams were increased by addition of cellulose microfibers or nanoclays into the foams. Thermogravimetric analysis (TGA) was used to characterize the thermal decomposition properties of the foams. The thermal decomposition behavior of all soy‐based polyurethane foams was a three‐step process and while the addition of cellulose microfibers delayed the onset of degradation, incorporation of nanoclays seemed to have no significant influence on the thermal degradation properties of the foams as compared to the foams without reinforcements. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Rigid polyurethane foams made from high viscosity soy‐polyols

This study investigated the physical properties of water‐blown rigid polyurethane (PU) foams made from VORANOL®490 (petroleum‐based polyether polyol) mixed with 0–50% high viscosity (13,000–31,000 cP at 22°C) soy‐polyols. The density of these foams decreased as the soy‐polyol percentage increased. The compressive strength decreased, decreased and then increased, or remained unchanged and then increased with increasing soy‐polyol percentage depending on the viscosity of the soy‐polyol. Foams made from high viscosity (21,000–31,000 cP) soy‐polyols exhibited similar or superior density‐compressive strength properties to the control foam made from 100% VORNAOL® 490. The thermal conductivity of foams containing soy‐polyols was slightly higher than the control foam. The maximal foaming temperatures of foams slightly decreased with increasing soy‐polyol percentage. Micrographs of foams showed that they had many cells in the shape of sphere or polyhedra. With increasing soy‐polyol percentage, the cell size decreased, and the cell number increased. Based on the analysis of isocyanate content and compressive strength of foams, it was concluded that rigid PU foams could be made by replacing 50% petroleum‐based polyol with a high viscosity soy‐polyol resulting in a 30% reduction in the isocyanate content. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Insulating rigid polyurethane foams from laurel tree pruning based polyol

The present work deals with the production of a natural polyol from laurel tree pruning waste, aiming the preparation of polyurethane foams. The obtained bio-polyol was characterized and applied into foams studying the influence of the isocyanate used and the addition of the physical blowing agent. The incorporation of the polyol allowed 40% polyol substitution for those foams in which TDI was used, and up to 60% using MDI. Apparent density, cell morphology, mechanical, and thermal properties were evaluated. Mechanical and thermal properties of the foams improve to a greater amount of polyol in the matrix. Specifically, the best thermal and mechanical properties (274.99 and 7275.91 kPa for compressive strength and Young Modulus, respectively) were obtained with 50% polyol substitution (0.63 R_NCO/OH). Foams showed small, well-defined cell morphology. Laurel derived polyol can be used for the preparation of foams using MDI, since the mechanical, and thermal properties are promising for obtaining insulation materials in the construction industry.     

New compounds for production of polyurethane foams

A method of boroorganic compound preparation with boric acid, 1,3‐propanediol, 2,3‐butanediol, and 1,4‐butanediol is described in this article. The obtained compounds were characterized with respect to their usability as polyol components for the production of polyurethane (PUR) foams. New boroorganic compounds were applied as polyol components for the foaming of rigid PUR–polyisocyanurate (PIR) foams. The method of preparation, foaming parameters, and physicochemical properties of the PUR–PIR foams and their results are presented. Application of the prepared borates as polyol components in the production of foams had a favorable effect on the properties of the foams. The obtained rigid foams were characterized by lower brittleness, higher compressive strength, content of closed cells, and considerably reduced flammability in comparison with standard foams. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5918–5926, 2006     

Preparation and characterization of polyurethane/silica aerogel nanocomposite materials

In this investigation, silica aerogel (SA)/Rigid Polyurethane (PUR) foam composites and silica aerogel/Polyurethane (PU) composites were prepared by dry mixing of granular and grinded silica aerogels with polyol part. They were then combined with diisocyanate part. Three different types of PUR foams and an elastomeric coating grade of PU were studied as well. Results show that thermal conductivity of foams did not decrease by adding silica aerogel. It even increased for some grades which is assumed to be due to the change in cell configuration of these foams. It was also found that sound insulation performance of these cellular composites did not improve significantly. Unlike foam composites, addition of silica aerogel into elastomeric PU improved its thermal and acoustic insulation properties. Because of the more promising properties of elastomeric PU composites, further examinations including measurements of compression strength and water contact angle of silica aerogel/PU composites were also taken. Final results showed a significant improvement in general properties of PU coatings by adding little amounts of silica aerogel (1–4 wt %). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44521.     

Thermal‐Insulation,Electrical, and Mechanical Properties of Highly‐Expanded PMMA/MWCNT Nanocomposite Foams Fabricated by Supercritical CO2 Foaming

Foaming behavior of poly(methyl methacrylate) (PMMA)/multi‐walled carbon nanotubes (MWCNTs) nanocomposites and thermally‐insulating, electrical, and mechanical properties of the nanocomposite foams are investigated. PMMA/MWCNT nanocomposites containing various amounts of MWCNTs are first prepared by combining solution and melt blending methods, and then foamed using CO₂. The foaming temperature and MWCNT content are varied for regulating the structure of PMMA/MWCNT nanocomposite foams. The electrical conductivity measurement results show that MWCNTs have little effect on the electrical conductivity of foams with large expansion ratio. Thermal conductivities of both solid and foamed PMMA/MWCNT nanocomposites are measured to evaluate their thermally insulating properties. The gas conduction, solid conduction, and thermal radiation of the foams are calculated for clarifying the effects of cellular structure and MWCNT content on thermal insulation properties. The result demonstrates that MWCNTs endowed foams with enhanced thermal insulation performance by blocking thermal radiation. Moreover, the compressive testing shows that MWCNTs improve the compressive strength and rigidity of foams. This research is essential for optimizing environmentally friendly thermal insulation nanocomposite foams with enhanced thermal‐insulation and compressive mechanical properties.     

Production of a high‐functionality RBD palm kernel oil‐based polyester polyol

A diol‐based refined, bleached, and deodorized (RBD) palm kernel oil polyol was prepared. It was found that the polyurethane foam produced only gives a good compressive strength property at a 45 kg/m³ molded density. The combination of sorbitol into the polyol system resulted in a better dimensional stability and improved thermal conductivity as well as enhanced compressive strength. These were obtained by increasing the functionality of the polyol (functionality of 4.5) through introduction of a high molecular weight and branching polyhidric compound. Direct polycondensation and transesterification methods were used for the syntheses. The hydroxyl value, TLC, and FTIR were used to study the completion of the reaction. A comparative study of the mechanical properties and morphological behavior was carried out with a diol‐based polyol. From the water‐blown molded foam (zero ODP) with a density of about 44.2 kg/m³ and a closed‐cell content of 93%, a compressive strength of 222 kPa and a dimensional stability of 0.09, 0.10, and 0.12% at the length, width, and thickness of the foam, respectively, conditioned at ?15°C for 24 h, were obtained. The thermal conductivity improved to an initial value of 0.00198 W/mK, tested at 0°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 384–389, 2001     

Biobased Polyurethane Composite Foams Reinforced with Plum Stones and Silanized Plum Stones

In the following study, ground plum stones and silanized ground plum stones were used as natural fillers for novel polyurethane (PUR) composite foams. The impact of 1, 2, and 5 wt.% of fillers on the cellular structure, foaming parameters, and mechanical, thermomechanical, and thermal properties of produced foams were assessed. The results showed that the silanization process leads to acquiring fillers with a smoother surface compared to unmodified filler. The results also showed that the morphology of the obtained materials is affected by the type and content of filler. Moreover, the modified PUR foams showed improved properties. For example, compared with the reference foam (PUR_REF), the foam with the addition of 1 wt.% of unmodified plum filler showed better mechanical properties, such as higher compressive strength (~8% improvement) and better flexural strength (~6% improvement). The addition of silanized plum filler improved the thermal stability and hydrophobic character of PUR foams. This work shows the relationship between the mechanical, thermal, and application properties of the obtained PUR composites depending on the modification of the filler used during synthesis.     

Effects of 4,4′‐diaminodiphenyl ether on the structures and properties of isocyanate‐based polyimide foams

A series of thermal insulation, acoustic absorption isocyanate‐based lightweight polyimide (PI) foams with 4,4′‐diaminodiphenyl ether (ODA) units were prepared from polyaryl polymethylene isocyanate (PAPI) and the esterification solution derived from pyromellitic dianhydride (PMDA) and ODA. The structures and properties of the PI foams prepared with different molar ratio of ODA/PMDA were investigated in detail. The results show that the ODA units have great influence on the foam properties. With the increase of the ODA units, the density decreases firstly and then increases. When the molar ratio of ODA/PMDA is 3/10, the foam reaches the minimum density (13.7 kg/m³). Moreover, with increasing the ODA units, the acoustic absorption properties increase firstly and then decrease owing to the variation of the average cell diameter of the PI foams. All PI foams show excellent thermal stability, and the 5% and 10% weight loss temperature are in the range of 250–270 °C and 295–310 °C, respectively. In addition, the PI foams present low thermal conductivity and thermal diffusivity. Furthermore, the mechanical property was also evaluated and the compressive strength of the PI foams is in the range of 33.0–45.7 kPa. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46029.     

Rigid polyurethane foams from a soybean oil-based Polyol

Polyurethane (PU) rigid foams were synthesized by substituting a polypropylene-based polyol with soybean oil-based polyol (SBOP). All the soy-based foams maintained a regular cell structure and had even smaller average cell size than the control foams. The density of soy-based foams was within 5% of the controls, except that the density of foams from 100% SBOP was 17% higher. Soy-based foams also had comparable initial thermal conductivity (k value) and closed cell content, higher T_g and compressive strength. However, while foams from 50% SBOP showed similar increase in k value to the 0% SBOP foams, under accelerated aging conditions, the 100% SBOP foams aged faster. Gas permeation tests performed on PU thin films showed higher N₂ permeation for PU thin films made from SBOP which is believed to be the cause of accelerated thermal aging.     

制备工艺对聚氨酯酰亚胺泡沫性能的影响

以均苯四甲酸二酐(PMDA)、多苯基多亚甲基多异氰酸酯(PAPI)、聚醚多元醇为主要原料,分别采用聚酰亚胺(PI)预聚法、聚氨酯(PU)预聚法和一步法制备聚氨酯酰亚胺泡沫,从微观形貌、力学性能、热稳定性能以及阻燃性能方面对上述3种制备工艺进行对比和评估。实验结果表明,采用一步法制备PUI泡沫时,PU链段和PI链段同时增长,容易造成泡孔缺陷,导致泡沫的力学性能较差;在采用PU预聚法制备的PUI泡沫中,PU链段含量较高,因此,泡孔孔径分布较宽且平均泡孔直径较大,对应的热稳定性和阻燃性能较差;采用PI预聚法制备的PUI泡沫的泡孔孔径分布窄且平均泡孔直径较小,对应的压缩性能、热稳定性以及阻燃性能均达到最佳。     

Microstructural,mechanical, and thermal‐insulation properties of poly(methyl methacrylate)/silica aerogel bimodal cellular foams

Novel poly(methyl methacrylate) (PMMA)/silica aerogel bimodal cellular foams were prepared by melt mixing and a supercritical carbon dioxide foaming process. The effects of the silica aerogel content on the morphologies and thermal‐insulating and mechanical properties of the foams were investigated by scanning electron microscopy, mechanical tests, and heat‐transfer analysis. The experimental results show that compared to the pure PMMA foam, the PMMA/silica aerogel microcellular foams exhibited more uniform cell structures, decreased cell sizes, and increased cell densities (the densities of the foams were 0.38–0.45 g/cm³). In particular, a considerable number of original nanometric cells (ca. 50 nm) were evenly embedded in the cell walls and on the inner surfaces of the micrometric cells (<10 μm). A 62.7% decrease in the thermal conductivity (0.072 W m⁻¹ K⁻¹) in comparison to that of raw PMMA after 0.5 wt % silica aerogel was added was obtained. Mechanical analysis of the PMMA/silica aerogel foams with 5 and 2 wt % silica aerogel showed that the compressive and flexural strengths were distinctly improved by 92 and 52%, respectively, and the dynamic storage moduli increased. The enhanced performance showed that with the addition of silica aerogel into PMMA, one can obtain thermal‐insulation materials with a favorable mechanical strength. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44434.     

Effect of auxiliary blowing agents on properties of rigid polyurethane foams based on liquefied products from peanut shell

The bio‐based rigid polyurethane (PU) foams were successfully prepared based on liquefied products from peanut shell with water as the blowing agent. The influence of reaction parameters on properties of rigid PU foams was investigated. Rigid PU foams showed excellent compressive strength and low shrinkage ratio, whereas their open‐cell ratio and water absorption were higher. Therefore, rigid PU foams were synthesized with petroleum ether, diethyl ether, and acetone as auxiliary blowing agents and their inner temperature, shrinkage performance, density, compressive strength, water absorption, and open‐cell ratio were determined. The results indicated that above rigid PU foams showed lower compressive strength than the original foam but their water absorption and close‐cell ratio were improved. Compared with the original foam, the highest inner temperature of rigid PU foams with petroleum ether, diethyl ether, and acetone as auxiliary blowing agents was reduced by 11, 19, and 23 °C, respectively. Typically, foams with petroleum ether as auxiliary blowing agent displayed better water absorption and swelling ratio in water and exhibited obvious improvement in close‐cell ratio. These foams were preferable for application in thermal insulation materials because of low thermal conductivity and better corrosion resistance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45582.     

Preparation and Characterization of Sustainable Polyurethane Foams from Soybean Oils

Polyol derived from soybean oil was made from crude soybean oil by epoxidization and hydroxylation. Soy-based polyurethane (PU) foams were prepared by the in-situ reaction of methylene diphenyl diisocyanate (MDI) polyurea prepolymer and soy-based polyol. A free-rise method was developed to prepare the sustainable PU foams for use in automotive and bedding cushions. In this study, three petroleum-based PU foams were compared with two soy-based PU foams in terms of their foam characterizations and properties. Soy-based PU foams were made with soy-based polyols with different hydroxyl values. Soy-based PU foams had higher T _g (glass transition temperature) and worse cryogenic properties than petroleum-based PU foams. Bio-foams had lower thermal degradation temperatures in the urethane degradation due to natural molecular chains with lower thermal stability than petroleum skeletons. However, these foams had good thermal degradation at a high temperature stage because of MDI polyurea prepolymer, which had superior thermal stability than toluene diisocyanate adducts in petroleum-based PU foams. In addition, soy-based polyol, with high hydroxyl value, contributed PU foam with superior tensile and higher elongation, but lower compressive strength and modulus. Nonetheless, bio-foam made with high hydroxyl valued soy-based polyol had smaller and better distributed cell size than that using low hydroxyl soy-based polyol. Soy-based polyol with high hydroxyl value also contributed the bio-foam with thinner cell walls compared to that with low hydroxyl value, whereas, petroleum-based PU foams had no variations in cell thickness and cell distributions.     

Preparation and physico‐mechanical,thermal and acoustic properties of flexible polyurethane foams based on hydroxytelechelic natural rubber

Novel flexible polyurethane foams were successfully prepared from a renewable source, hydroxytelechelic natural rubber (HTNR) having different molecular weights (1000–3400 g mol^?1) and variation of epoxide contents (EHTNR, 0–35% epoxidation) by a one‐shot technique. The chemical and cell structures as well as physico‐mechanical, thermal, and acoustic properties were characterized and compared with commercial polyol analogs. The obtained HTNR based foams are open cell structures with cell dimensions between 0.38 and 0.47 mm. The HTNR1000 based foam exhibits better mechanical properties but lower elongation at break than those of commercial polyol analog. However, the HTNR3400 based foam shows the best elastic properties. In a series of EHTNR based foams, the tensile and compressive strengths show a tendency to increase with increasing epoxide content and amount of 1,4‐butanediol (BD). The HTNR based foams demonstrate better low temperature flexibility than that of the foam based on commercial polyol. Moreover, the HTNR based polyurethane foams was found to be an excellent absorber of acoustics. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Comparative study of physical properties of water‐blown rigid polyurethane foams extended with commercial soy flours

The use of renewable resources (mainly carbohydrates) in rigid polyurethane foam has been known to offer several advantages, such as increased strength, improved flame resistance, and enhanced biodegradability. Less attention has been directed to inexpensive protein‐based materials, such as defatted soy flour. The objectives of this study were to develop water‐blown rigid polyurethane foams, containing defatted soy flour, that have acceptable or improved physical properties which also lower the cost of the foam formulation and to compare the properties of developed foams extended with three kinds of commercial soy flour. Water‐blown low‐density rigid polyurethane foams were prepared with poly(ether polyol)s, polymeric isocyanates, defatted soy flour, water, a catalyst mixture, and a surfactant. Soy flour and the initial water content were varied from 0 to 40% and from 4.5 to 5.5% of the poly(ether polyol) content, respectively. A standard laboratory mixing procedure was followed for making foams using a high‐speed industrial mixer. After mixing, the mixture was poured into boxes and allowed to rise at ambient conditions. Foams were removed from boxes after 1 h and cured at room temperature for 24 h before measurement of the thermal conductivity and for 1 week before other property tests. Foam properties were determined according to ASTM procedures. Measurement of the physical properties (compressive strength, modulus, thermal conductivity, and dimensional stability under thermal and humid aging) of these foams showed that the addition of 10–20% of three kinds of soy flour imparted water‐blown rigid polyurethane foams with similar or improved strength, modulus, insulation, and dimensional stability. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 10–19, 2001