Polyaryl Polymethylene Isocyanate Research Articles

A facile synthesis of solid-solid phase change material for thermal energy storage

Abstract Thermosetting polyurethane based on Polyethylene glyol and Polyaryl polymethylene isocyanate was prepared through solvent-free bulk polymerization for solid-solid phase change materials. Chemical structure, crystallization behavior, phase change behavior, thermal reliability and thermal stability of Polyethylene glyol based phase change materials were extensively studied by fourier transform infrared spectroscopy, X-ray diffraction, polarizing optical microscopy, differential scanning calorimetry, thermal cycling testing and thermogravimetric analysis, respectively. The polarizing optical microscopy and X-ray diffraction results indicated that the crystal structure of prepared phase change materials was not affected by the crosslink structure. Differential scanning calorimetry measurements showed that prepared phase change materials possess high latent heat and appropriate phase change temperature for the application of thermal energy storage. The maximum latent heat of phase change materials in melting and freezing process reached 111.7 J/g and 110.4 J/g, respectively. Thermal cycling test and thermogravimetric analysis results demonstrated the good thermal reliability and stability of prepared phase change materials. The prepared phase change materials showed the potential for thermal energy storage application and will make an effective utilization of waste energy.

Interfacial Adhesion and Damping Characteristics of Laminated Veneer Lumber Intercalated with Rubber Sheets

Laminated wood veneer lumber intercalated with rubber sheets (LLVR) was fabricated using a layered adhesive system composed of polyaryl polymethylene isocyanate (PAPI) for wood-rubber inter-bonding and phenol formaldehyde (PF) resin to glue the wood veneers. The optimized manufacturing process (chloroprene rubber: CR; PAPI: 80 g/m2; PF: 200 g/m2; and silane: 9.0 wt.%) was determined. The process as developed was then utilized to fabricate nine-ply LLVRs of five balanced constructions with two or three CR laminates used as various layers. The physico-mechanical properties of the LLVRs were evaluated, and the results showed that LLVRs had strong shear strength, sound dimensional stability, decent bending strength, and favorable toughening and buffering performances. The newly developed product is an interesting potential alternative to traditional laminated veneer lumber or plywood.

Fertilization impacts on green leafy vegetables supplied with slow release nitrogen fertilizers

ABSTRACTConventional over-fertilization in green leafy vegetables has promoted the need for alternative nitrogen management practices. A novel slow-release fertilizer, coated with inorganic minerals, was developed in our lab. The membrane structural characteristics and nitrogen release profile of the product were systematically studied. Furthermore, different fertilization treatments were prepared to study the potential nitrogen use efficiency in Brassica chinensis L., cultivated under open field and greenhouse cultivation patterns. With a relatively smooth surface, coating layer of the newly developed fertilizer stacked by bonded multi-layer of polyaryl polymethylene isocyanate was formed by tightly arraying solid phosphate rock powder granules. After immersing the fertilizer in water, there was about 13% nitrogen released after 24 h and 30% of nitrogen released in 7 days. Moreover, the fertilizer significantly enhanced the yield of Brassica chinensis L. by 28.2%. Nitrogen use efficiency of vegetables treated with the fertilizer was much higher than that of conventional fertilization.

Facile fabrication of polyimide foam sheets with millimeter thickness: Processing, morphology, and properties

ABSTRACTA series of polyimide foam sheets (PIFSs) with thickness of 0.5 mm using 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA), 3,4′‐oxydianiline (3,4′‐ODA), and polyaryl polymethylene isocyanate (PAPI) as main materials were first fabricated by liquid foaming and compression molding technology. The effects of different PAPI contents and 3,4′‐ODA contents on the structures and properties of PIFSs were investigated. The results indicated that PIFSs exhibited a structure that front surface displayed closed cells made of damaged cell walls and membranes, while internal cells were open, and elliptic vacancies were flatted in the thickness direction from the cross section. The average cellular diameter increased with increasing PAPI loading. In addition, the introduction of 3,4′‐ODA increased the average cell size of PIFSs. Further, PIFSs had density of 0.087–0.239 g/cm3, elongation at break of 3.75–8.01% and tensile toughness of 3.46 × 10−2−13.87 × 10−2 J/cm3. Notably, they exhibited higher tensile strength of 1.89–5.42 MPa and lower thermal conductivity of 14.727–19.25 mW/m •K at 24°C, compared to the polyimide foams reported earlier. The sound absorption coefficients (α) of samples with different PAPI contents increased and then decreased with increasing PAPI content. At low frequencies, a certain content of 3,4′‐ ODA allowed an improvement of the acoustical behavior of PIFSs, and the α increased and then decreased with increasing density. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39881.

Thermal, mechanical, and rheological properties of poly(propylene carbonate) cross-linked with polyaryl polymethylene isocyanate

In this study, cross-linked poly(propylene carbonate) (PPC) was prepared using polyaryl polymethylene isocyanate (PAPI) as a cross-linking agent. The gel content, thermal behaviors, mechanical and rheological properties of the cross-linked PPC were investigated. FTIR results showed that the chemical reactions took place between PPC and PAPI and the interactions demonstrated that PPC may be cross-linked with the PAPI. The results of gel content revealed that PPC was partially cross-linked with the PAPI. The cross-linked PPC showed higher glass transition temperature and decomposition temperature compared with pure PPC. Accordingly, the melt flow index gradually decreased and complex viscosity increased with increasing PAPI content. Moreover, the mechanical properties proved also to be enhanced as evidenced by tensile tests. The introduction of small amount of cross-linkable moiety provides an efficient and convenient method to improve the properties of PPC and extend its application area.

Preparation and characterization of electromagnetic interference shielding polyimide foam

AbstractThis article focused on the preparation and characterization of ultralight and high‐temperature resistant polyimide foam (PIF) for electromagnetic interference shielding. PIF was first prepared based on a one‐pot process by the primary reactions of derivatives of pyromellitic dianhydride and polyaryl polymethylene isocyanate. Then, PIFs with silver (0) coating were then prepared by spraying silver (0) on the surfaces of PIF through physical spraying method. The surface density of silver coating was 0.18 kg/m2, and the densities of silver‐coated PIFs were less than 23 kg/m3. The scanning electron microscopy coupled with an energy‐dispersive X‐ray spectrometer (EDX) measurement were carried out to investigate the morphological and chemical properties of uncoated and coated PIFs. For coated PIFs, the EDX spectrums indicated increasing higher silver proportions from interior to exterior surface, together with increasing higher carbon proportions from exterior surface to interior. Thermogravimetry/Fourier transform infrared instrument that combined thermogravimetric analysis with pyrolysis product analysis by Fourier transform infrared spectroscopy were applied to investigate the thermal stability and pyrolysis products of uncoated and coated PIFs. The results indicated that the thermal properties of silver‐coated PIFs were improved obviously with the 5% weight loss temperature higher than 400°C and the residual weight retentions at 800°C ∼ 80%. In the frequency range 200–7000 MHz, the EMI shielding efficiency with one surface and two surfaces coated with silver were in the range of 36.4–60.7 dB and 61.6–95.6 dB, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Thermal properties of the polyimide foam prepared from aromatic dianhydride and isocyanate

A new type of polyimide foam (PIF) was prepared successfully based on a one-pot process by the reaction of a first solution and a second solution. The first solution comprised pyromellitic dianhydride (PMDA), N, N-dimethyl formamide (DMF), methanol, polyethylene glycol and water. The second solution contained polyaryl polymethylene isocyanate (PAPI). The thermal properties of the polyimide foam were thoroughly investigated by thermogravimetry–Fourier transform infrared spectroscopy (TG–FTIR) and high-resolution pyrolysis gas chromatography–mass spectroscopy (PyGC–MS) at various temperatures. The results of TG–FTIR indicated that polyimide foam was thermally stable and experienced a weight loss of less than 2% before the scanning temperature reached 280.7 °C. It showed a two-stage degradation process during the whole decomposition. The major decomposition products were carbon dioxide (CO2), carbonic oxide (CO) and methyl formate. The results of PyGC–MS indicated that no pyrolysis products were indentified when the test temperature was 250 °C. Certain pyrolyzates such as oxygen, carbon dioxide and methyl formate was identified as the pyrolysis temperature increased. According to the degradation behaviors and the structure and relative content of pyrolysis products, a proposed pyrolysis mechanism of polyimide is presented in this article.

Preparation and performance of a novel polyimide foam

AbstractA new type of polyimide foam (PIF) was prepared and characterized based on a one‐pot process by the reaction of a first solution with different ratios of a second solution. The first solution was comprised of pyromellitic dianhydride (PMDA), N, N‐dimethyl formamide (DMF), methanol, water, surfactant, and catalysts, while the second solution contained polyaryl polymethylene isocyanate (PAPI). In the present study, the relationships among compositions, structures, and properties of PIFs were investigated. The results indicated that with the increase in the weight ratio of PAPI/(first solution), the foaming degrees of PIFs increased from 10.14 to 10.52 times and the apparent densities before postcure decreased from 15.96 to 14.51 kg/m3. The open cell contents, average sound absorption coefficients, and average cellular diameters of PIFs after postcure increased with increase in the weight ratio of PAPI/(first solution). The glass transition temperatures (Tg) of PIFs after postcure first increased from 287 to 299°C, then decreased to 292°C, and the 5% weight loss temperatures and 10% weight loss temperatures presented the same trend as well. The compressive and flatwise tensile properties scaled very well with the relative densities of the foams after postcure, with the highest compressive strength of 0.03 MPa and the highest flatwise tensile strength of 0.15 MPa. Copyright © 2011 John Wiley & Sons, Ltd.

Preparation of semirigid polyurethane foam with liquefied bamboo residues

AbstractBamboo residues were liquefied by using a solvent mixture consisting of polyethylene glycol 400 and crude glycerol (4/1, w/w) with 98% sulfuric acid as catalyst at 160°C for 120 min. The liquefied bamboo had hydroxyl values from 178 to 200 mg KOH/g and viscosities from 507 to 2201 mPa S. The obtained bamboo‐based polyols were reacted with various amounts of polyaryl polymethylene isocyanate (PAPI), using distilled water as blowing agent, silicone as surfactant, and triethylenediamine and dibutyltine dilaurate as cocatalyst to produce semirigid polyurethane (PU) foams. The [NCO]/[OH] ratio was found to be an important factor to control the mechanical properties of PU foams. At a fixed [NCO]/[OH] ratio, both density and compressive strength of PU foams decreased with the increase of bamboo content. The microstructure of PU foams indicates that [NCO]/[OH] ratios are important for cell formation and chemical reactions. The uniformity and cell structure of the foams are comparable to their corresponding compressive strengths. Moreover, the thermogravimetry analysis showed that all the semirigid PU foams had approximately the same degradation temperature of about 250 to 440°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Effect of glycols on the properties of polyester polyols and of room‐temperature‐curable casting polyurethanes

AbstractA series of liquid polyester polyols (PEs) from adipic acid (AA), phthalic anhydride (PA) and trihydroxymethylpropane (TMP), and such glycols as ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), butanediol (BD) and hexanediol (HD), were prepared. Polyurethanes (PUs) were obtained from the PEs and polyaryl polymethylene isocyanate (PAPI) at room temperature. The effects of the structures of the glycols on viscosity, glass transition temperature and crystallinity of the PEs, and the mechanical, thermal and boiling‐water‐resistant properties of PUs were studied. The experiments showed that the viscosities and glass transition temperatures of the PEs decreased as the length of the glycol chains increased. The polyester based on HD lost flowability because of crystallization. The tensile strength and hardness of the PUs obtained decreased with increasing the length of the glycol chains, while the resistance to thermal deformation and boiling water increased. Thermogravimetric analysis demonstrated that thermal degradation of the polyurethane based on DEG proceeded in one step and for the others in two steps. The initial degradation temperature of the polyurethane based on EG was the lowest and that of the polyurethane based on BD was the highest. The residue of the former at 450 °C was the greatest, while that of the latter was the lowest. Copyright © 2004 Society of Chemical Industry