Structure and properties of polyurethane acrylate prepolymers based on hydroxy‐terminated polybutadiene

Precursors of polyurethane acrylate based on hydroxy‐terminated polybutadiene (HTPB) soft segments, different diisocyanate and hydroxy ethyl acrylate (HEA) as hard units, were synthesized in bulk or in solution in methyl methacrylate. During precursor synthesis (in bulk), microphase separation was observed by small‐angle X‐ray scattering (SAXS). Diffusing particles are around 50 Å in size and are assumed to be assembling of hard segments. From these morphologies, it can be deduced that some isocyanate groups were trapped/or buried in hard domains. At a larger scale, around millimeters, hard segment crystallites were observed. Properties such as molar masses, melting and glass‐transition temperatures, and viscosities were correlated with precursor structure and morphology. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 225–233, 2002     

Interconversion of light olefins—aromatics over zeolite catalysts

Improved yield in light olefins and aromatics from methanol conversion was observed on Zn and Mn loaded ZSM-5 zeolite—asbestos catalysts. The best results in terms of conversion into hydrocarbons were obtained with a Zn content not exceeding 0.6% wt/wt. The light olefins/aromatics ratio in the products varied with the Mn content in the catalyst, the cumulative light olefinic and aromatic production being kept constant at a high value.     

Unconventional Configuration Studies to Improve Mixing Times in Stirred Tanks

Dynamic perturbations and off‐centered single and dual mixing impeller configurations have been investigated to reduce mixing time with viscous fluids. Mixing times, measured with a color‐discoloration technique based on a fast acid‐base reaction, reveal the presence of both segregated and dead zones. A statistical design approach has been used to evaluate the effect of the impeller position as well as the dynamic conditions. Homogenization is significantly enhanced when a radial flow impeller is used under both off‐centered and dynamic perturbation conditions. In the case of an axial flow impeller, a combination of long clockwise times and short counter‐clockwise times give better mixing times. An enhanced homogenization is also observed when a dual impeller configuration is used.     

Use of empirical polarity parameters to describe polymer/liquid interactions: Correlation of polymer swelling with solvent polarity in binary and ternary systems

Dimroth and Reichardt polarity parameters E_T(30) have been used, in a new approach, to quantitatively describe the swelling features due to polymer liquid interactions in binary and ternary systems. With the help of a polyurethaneimide (PUI) synthesized from polytetramethyleneglycol 650, sorption of pure liquids was first examined, and it was shown that a linear relationship between the molar swelling G_m and the E_T(30) values well fits the experimental data of each of the two series studied, i. e., aliphatic alcohols and linear ethers: G_m = a+b E_T(30). The slope value b, regarded as the sensitivity of the polymer to the liquid polarity, is 3 times higher for the aprotic series. The proposed correlation was further proved valid from the study of published results concerning nine binary systems polymer–liquid, whatever the polarity of the liquids in a given family (alcohols, esters, ketones, hydrocarbons) and the nature of the polymer. Finally, that method was tested on two types of PUI-alcohol-ether ternary systems, and it was found for each case that the partial molar swelling due to an homologous set of solvents can also be described by a similar law. © 1994 John Wiley & Sons, Inc.     

Compression Test and Plastic Strain of alpha-Al2O3 Single Crystals

Compression tests of single crystals are analyzed with respect to shear due to the friction at the loaded ends. This simple approach permits an explanation of the features associated with prism plane slip in sapphire (α-Al₂O₃), i.e., the shape changes of the specimens and the curvature of the glide planes.     

Use of Hydroxyl Functionalized (Meth)acrylic Cross‐Linked Polymer Microparticles as Chain Transfer Agent in Cationic Photopolymerization of Cycloaliphatic Epoxy Monomer, 2

This study is related to the use of hydroxyl functional acrylic cross‐linked polymer microparticles (CPM, also named microgels) as a chain transfer agent in cationic photopolymerization of cycloaliphatic epoxy monomer. All CPM were based on butyl acrylate and were consequently rubbery at ambient temperature. The effect of the stabilizing acrylate monomer used during the CPM synthesis was evaluated with respect to the viscoelastic properties of the photopolymerized cationic‐type epoxy films. The viscoelastic properties were correlated to the photopolymerized film morphology observed by transmission electron microscopy. Two acrylate monomers used as stabilizing agents during CPM synthesis were compared: cardura acrylate (CA) and lauryl acrylate (LA). CA was a good stabilizer for CPM in epoxy monomer before photocure and the CPM were well dispersed into the network after reaction. In contrast, LA was a poor stabilizer resulting in large CPM aggregation. The blend of these two types of CPM led to intermediate morphology, probably because of the flocculation of the CPM stabilized with LA. Conversely, CPM synthesized with a blend of the two stabilizing acrylate monomers induced in epoxy matrix a specific bi‐continuous morphology and consequently unique viscoelastic properties.

TEM micrographs of a photopolymerized film with 15 wt.‐% CPM(BA + 20%HEA)‐20%CA + 15% CPM(BA + 18%HEA)‐27%LA used as chain transfer agents.     

Properties of mLLDPE/LDPE blends in film blowing

We evaluated the inline birefringence of two blend systems in film blowing. The first system consisted of a metallocene catalyzed linear low density polyethylene (mLLDPE‐1) and a low density polyethylene (LDPE‐1); the second one was made of a metallocene catalyzed polyethylene containing sparse long chain branches (mLLDPE‐2) and another low density polyethylene (LDPE‐2). Experimental data show that before the crystallization starts, the birefringence of the mLLDPE‐2/LDPE‐2 blends is a linear function of blend composition, suggesting miscibility of the mLLDPE‐2/LDPE‐2 blends. However, the birefringence of the mLLDPE‐1/LDPE‐1 blends shows positive deviations with respect to a linear function of blend composition. This is caused by the existence of form birefringence, suggesting immiscibility of the mLLDPE‐1/LDPE‐1 blends. The nonuniform biaxial elongational viscosity (NUBEV) at the reference temperature of 175°C for LDPE‐1 was evaluated for different operating conditions. The results show that NUBEV is approximately a unique function of the deformation rate, confirming the validity of the assumptions and technique used for the NUBEV calculation. The NUBEV and the nonuniform biaxial Trouton ratio (NUTR) of the mLLDPE‐2/LDPE‐2 blends was also evaluated using the same technique. The NUBEV of all mLLDPE‐2/LDPE‐2 blends shows a strain‐thinning behavior within the deformation rates investigated. Furthermore, the NUTR results show that LDPE‐2 deviates largely from the Newtonian fluid behavior, whereas mLLDPE‐2 is quite close to the Newtonian behavior. Nevertheless, the NUTR of the mLLDPE‐2/LDPE‐2 blends is almost a linear function of blend composition. POLYM. ENG. Sci., 45:343–353, 2005. © 2005 Society of Plastics Engineers     

Coordination and Organometallic Polymers and Oligomers of Upper-Rim Functionalized Calix[4]arenes by Transition Metals

This short review focuses on recent advances in the syntheses, characterization and structures of coordination and organometallic complexes of upper-rim functionalized calix[4]arenes that form either small oligomers or polymers. This field is very limited, presumably due to the lack of X-ray data or reliable characterization that demonstrates the presence of oligomers or polymers. Nonetheless, the few published works already clearly demonstrate the immense versatility of the calix[4]arene macrocycle as it forms polymeric materials via coordination bondings with transition metals.     

Mechanical properties of autoclaved shell-aggregate

Waste solid propylene oxide sludge (POS) and fly ash were used as main raw material to prepare propylene oxide sludge aggregate (POSA) under the condition of autoclaved (180 ℃,1.0 MPa) curing. Three different test methods namely cylinder compressive strength (CCS), individual aggregate compressive strength (IACS) and strength contribution rate (SCR) proposed were used to characterize the mechanical properties of the autoclaved POSA. POS shell-aggregate with SCR of 94% were prepared under the hydrothermal synthesis and autoclaved curing. The experimental results indicate that CCS and IACS have good consistency in characterizing mechanical properties of POSA. It is suggested that SCR not only can characterize the strength of POSA core, but also can reflect the effect of shell on the performance of POSA. By means of least square method, relationships between CCS and IACS, CCS and SCR, IACS and SCR were deduced.     

Selective oxidation of secondary amines over titanium silicalite molecular sieves,TS-1 and TS-2

Titanium silicalite molecular sieves, TS-1 and TS-2 having MFI and MEL structures, respectively, catalyze the oxidation of secondary amines to the corresponding hydroxylamines using hydrogen peroxide as the oxidant. Higher concentrations of H₂O₂ lead to further oxidation of hydroxylamine to nitrone. Diffuse reflectance spectroscopy shows the formation of a titanium peroxo complex upon addition of hydrogen peroxide to the TS-1 catalyst. The titanium peroxo complex oxidizes the substrate and reforms to a titanyl group.