Reactive flame retardant with core‐shell structure and its flame retardancy in rigid polyurethane foam

With a shell of poly (methyl methacrylate‐co‐hydroxyl ethyl acrylate) (PMMA‐HA), microencapsulated ammonium polyphosphate (MHAPP) is prepared by in situ polymerization. The core‐shell structure of the reactive flame retardant (FR) is characterized by Fourier transform infrared (FTIR) and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). The results of water leaching rate and water contact angle measurements show that ammonium polyphosphate (APP) is well coated by a hydrophobic shell. Due to the presence of active groups (–OH) and hydrophobic groups (–CH₃) in shell, MHAPP exhibits better compatibility, flame retardancy, and water resistance compared with neat ammonium polyphosphate (APP) in rigid polyurethane foam (PU). Compression strength of PU/MHAPP with suitable loading is higher than that of PU/APP and PU, the reason is that the active groups in shell can improve the compatibility of MHAPP in PU composite. From thermal stability and residue analysis, it can be seen that the presence of reactive flame retardant shows positive effect on thermal stability of PU composite at high temperature, results also indicate that MHAPP can promote the carbonization formation efficiency of PU composite during combustion process compared with APP. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42800.     

Effect of glass transition temperature and saturation temperature on the solid‐state microcellular foaming of cyclic olefin copolymer

Effect of glass transition temperature and saturation temperature on the solid‐state microcellular foaming of cyclic olefin copolymer (COC)—including CO₂ solubility, diffusivity, cell nucleation, and foam morphology—were investigated in this article. COCs of low T_g (78°C) and high T_g (158°C) were studied. Solubilities are 20–50% higher in high T_g COC than in the low T_g COC across the saturation temperature range. Diffusivities are about 15% higher on average in high T_g COC for temperatures up to 50°C. A much faster increase of diffusivity beyond 50°C is observed in low T_g COC due to it being in the rubbery state. Under similar gas concentration, high T_g COC starts foaming at a higher temperature. And the foam density decreases faster in low T_g COC with foaming temperature. Also, high T_g COC foams show about two orders of magnitude higher cell nucleation density than the low T_g COC foams. The effect of saturation temperature on microcellular foaming can be viewed as the effect of CO₂ concentration. Nucleation density increases and cell size decreases exponentially with increasing CO₂ concentration. Uniform ultramicrocellular structure with an average cell size of 380 nm was created in high‐T_g COC. A novel hierarchical structure composed of microcells (2.5 μm) and nanocells (cell size 80 nm) on the cell wall was discovered in the very low‐density high‐T_g COC foams. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42226.     

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.     

Synthesis of macroporous polymer foams via pickering high internal phase emulsions for highly efficient 2,4,5‐trichlorophenol removal

Macroporous polymers foams (MPFs) were prepared by W/O Pickering high internal phase emulsions (HIPEs) stabilized by oleic acid (OA) modified silica nanoparticles (SPs), and then as‐prepared MPFs were applied to highly efficient adsorption of 2,4,5‐trichlorophenol (TCP). The characterization demonstrated that MPFs possessed macropore (50–150 μm) and interconnected pores (0.5–2 μm), and also had slightly hydrophobic nature (contact angle was 116°) and excellent thermal stability especially bellow 200°C. The influence of pH value, temperature, initial concentration, and contact time for the batch mode adsorption process was investigated, and the results showed that the maximum adsorption capacity and equilibrium time at 25°C were 167.7 mg g^?1 and 30 min, respectively. Moreover, the experimental data indicate that equilibrium isotherms for TCP fitted to the non‐linear Langmuir model, and both the adsorption and desorption kinetics can be represented by the pseudo‐second‐order model. The possible adsorption mechanism was considered to be the dispersion and hydrophobic interaction, simultaneously. The regeneration of the MPFs for one cycle was 94%. The results above strongly proved that this method reached the effect of highly efficient TCP removal. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41430.     

Nano‐crystalline cellulose,chemical blowing agent,and mold temperature effect on morphological,physical/mechanical properties of polypropylene

Polypropylene (PP)/nano‐crystalline cellulose (NCC) composites and foams were produced through extrusion compounding combined with injection molding. From the samples produced, a complete morphological, physical, and mechanical analysis was performed to study the effect of NCC concentration (0–5wt %), foaming agent content (0 to 2wt %) and mold temperature (30°C and 80°C). NCC was very effective to reduce cell size (42–71%) and increase cell density (5–37 times) of the foams, while slightly increasing the overall density (2–7%). The results showed that NCC addition increased the specific tensile modulus (15–22%), specific tensile strength (1–14%) and specific flexural modulus (13–26%) of PP, but decreased specific impact strength (10–20%) and specific elongation at break (50–96%). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42845.     

Effects of processing parameters and thermal history on microcellular foaming behaviors of PEEK using supercritical CO2

In this study, we mainly investigate the solid‐state foaming of polyether ether ketone (PEEK) with different crystallinities using supercritical CO₂ as a physical blowing agent. The gaseous mass‐transfer and thermophysical behaviors were studied. By altering the parameters of the foaming process, microcellular foams with different cell morphologies were prepared. The effect of crystallization on the cell morphology was also investigated in detail. The results indicate that the crystallization restricts gas diffusion in the material, and the thermophysical behaviors of the saturated PEEK sample with low crystallinity presents two cold crystallization peaks. The cell density decreases and the cell size increases as the saturation pressure increases. The cell density of the microcellular foams prepared under 20 MPa is 1.23 × 10¹⁰ cells/cm³, which is almost 10 times compares to that under 8 MPa. The cell size increases as the foaming time extends or the foaming temperature increases. It is interesting that the cell morphology with a bimodal cell‐size distribution is generated when the samples are foamed at temperatures higher than 320°C for a sufficient time. Additionally, nanocellular foams can be obtained from a highly crystallized PEEK after the decrystallization process. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42576.     

Rigid polyurethane foams modified with selected layered silicate nanofillers

The aim of this study was to investigate the effect of three different nanofillers on the properties of rigid polyurethane foams, which were prepared by a one‐step, laboratory‐scale method from a two‐component system at the ratio of NCO groups to OH groups equaled to 2. The reaction mixture consisted of the proper amounts of the commercial oligoether polyol, catalysts, water, nanoclays, and polymeric diphenylmethane diisocyanate. Three types of montmorillonite were used as clay component, i.e., montmorillonite modified by methyl tallow bis‐2‐hydroxyethyl ammonium (Cloisite^®30B), a synthetic layered silicate (Laponite^®RD), and an aluminium phyllosilicate absorbent, essentially impure clay consisting mostly of montmorillonite (Bentonite). Thermal properties of rigid polyurethane foams and nanocomposite foams were investigated by dynamical thermal analysis, thermogravimetry, oxygen index, and thermal conductivity measurements. It has been shown that the foams modified by selected nanofillers are characterized by high mechanical strength, as well as improved fire barrier properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2272–2281, 2013     

Synthesis and applications of oligoetherols with perhydro‐1,3,5‐triazine ring and boron

A new method of preparation of oligoetherols containing perhydro‐1,3,5‐triazine rings and boron atoms is presented. The oligoetherols were obtained in the reaction of 1,3,5‐tris(2‐hydroxyethyl) isocyanurate with boric acid followed by reaction with alkylene carbonates. The structure and physical properties of the products render them good candidate for preparing the polyurethane foams. The foams were obtained and their properties were compared with those synthesized from isocyanuric acid and alkylene carbonates. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Improved specific thermomechanical properties of polyurethane nanocomposite foams based on castor oil and bacterial nanocellulose

Bacterial nanocellulose (BNC) was used to synthesize polyurethane foams (PUFs) prepared from castor oil polyol and MDI diisocyanate using water as the blowing agent. The BNC reacted with the isocyanate, increasing the weight content of urethane hard segments (HS). It did not behave as a nucleation agent, forming a nanometric distribution of cells within the struts followed by a reduction of the apparent density (?7.6%) and a relevant increase of cell size in the growth direction (+37.9%). An alignment of the BNC parallel to the cell walls was observed, producing a nanocomposite with a higher reinforcement weight fraction in that area. At only 0.2 wt %, the BNC behaved as a nanostructured reinforcement, improving the specific compression modulus and strength by +4.67% and +23.6%, respectively, as well as the thermomechanical properties, with an improvement of the specific E ′ at 30 °C of +52.4%. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44982.     

浅谈水稳(底)基层配合比设计

文章以安徽省亳州段105国道和305省道水稳(底)基层的质量控制为例,从原材料、配合比设计等几个方面的控制入手,对如何清除或减少水稳(底)基层的裂缝提出一些预控措施。