Structure–property relationship of HTPB-based propellants. III. Optimization trials with varying levels of diol–triol contents

A systematic study has been conducted on a composite solid propellant formulation using hydroxyl-terminated polybutadiene (HTPB) prepolymer with varying molecular weights and hydroxyl values. Fairly extensive regions of resin parameters have been studied. Contours of important propellant properties have been laid down. In this set of experiments, varying levels of diol and triol contents were used at two different NCO/OH ratios to arrive at the optimum level needed for different grades of HTPB resin. It is seen that different grades of HTPB resin require varying levels of diol–triol contents to give similar properties for the end product. Also, for the best performance, varying the diol–triol ratio at the optimum level of the diol–triol content is necessary. © 1994 John Wiley & Sons, Inc.     

Surfactants, polymers and their nanoparticles for personal care applications

A 'touch me not' plant folding up rapidly upon being attacked or microbes depositing on teeth or ocean vessels even under hostile conditions are examples in nature that provide inspiration for developing new classes of personal care release or deposition systems. In this paper, development of such systems based on polymer/surfactant colloid chemistry is explored for achieving transport and release of cosmetic and pharmaceutical molecules at desired rates at desired sites. The successful development of products depends upon understanding and utilizing key interactions among surfactants, polymers and hybrid polymers that are relevant to personal care products. Thus, the absorbed layers or tethers on the particulates can be manipulated for desired dispersion of actives or depositions on substrate under any and all conditions. New hybrid polymers and nanogels have been synthesized for tuning up nanodomains that can extract and deliver at will cosmetics/drugs/toxins by perturbing pH, temperature or ionic strength of the system. Particularly, hydrophobically modified polymers have features of both polymers and surfactants and due to the associative nature of the hydrophobic groups, such polymers can form intramolecular nanodomains for performing carrier functions. Nanogels developed recently include that of polyacrylamide, poly(acrylic acid) and starch nanogels modified for extraction and subsequent slow release of fragrances and overdosed toxic drugs. Binding and release processes were investigated using surface plasmon resonance and fluorescence spectroscopies, powerful techniques for monitoring short term and long term changes.     

A novel processing scheme for core – shell nano composites using controlled polymer adsorption

 A new processing scheme has been developed for the preparation of core-shell structured composite particles that can be used as building blocks for the fabrication of nanocomposites [1]. The scheme is a two stage coating process utilizing controlled polymer adsorption and bridging in which a layer of nano sized particles is bridged onto submicron sized core particles. The coating process is monitored using electrokinetic techniques as well as SEM. The controlled coating process was used also to prepare multilayer nanocomposites. The application of the coating process to concentrated suspensions (15 volume percent) required in ceramic processing was shown to be feasible. Ceramic compacts were successfully prepared using pressure filtration methods and tested for their green density and flexibility. Received: 18 October 1998/Revised and accepted: 1 December 1998     

不同成因磷灰石可浮性的研究

对五种不同成因磷灰石的浮选行为与表面,溶解速度,油酸钙沉淀和油酸盐吸附量等之间的关系作了系统研究。实验表明,磷灰石的溶解速度,油酸钙沉淀量及充分浮选所需油酸钾浓度都与磷灰石的比表面积有关。 沉积型磷灰石有较大比表面积,在水溶液中溶下较多量ca~(2+)离子,生成较多油酸钙沉淀,充分浮选时需较高油酸钾浓度。 充分浮选时,捕收剂在五种不同磷灰石表面的复盖率看来是相近的,都有油酸钙沉淀生成,这与ca~(2+)离子从磷灰石表面溶下速度及达到一定复盖率时所需的捕收剂浓度有关。     

A population balance model for flocculation of colloidal suspensions by polymer bridging

A detailed population balance model for flocculation of colloidal suspensions by polymer bridging under quiescent flow conditions is presented. The collision efficiency factor is estimated as a function of interaction forces between polymer coated particles. The total interaction energy is computed as a sum of van der Waals attraction, electrical double layer repulsion and bridging attraction or steric repulsion due to adsorbed polymer. The scaling theory is used to compute the forces due to adsorbed polymer and the van der Waals attraction is modified to account for presence of polymer layer around a particle. The irregular structure of flocs is taken into account by incorporating the mass fractal dimension of flocs. When tested with experimental floc size distribution data published in the literature, the model predicts the experimental behavior adequately. This is the first attempt towards incorporating theories of polymer-induced surface forces into a flocculation model, and as such the model presented here is more general than those proposed previously.     

Mechanisms of grinding modification by chemical additives: organic reagents

The effects of dodecylammonium chloride on properties of quartz slurries that are relevant to grinding, such as pulp fluidity, flocculation and dispersion, and primary breakage, have been investigated in this study. These tests were conducted under chemical conditions (pH, ionic strength, additive concentration, etc.) similar to those used in wet ball milling tests. The data obtained were correlated with the grinding results. Amine was found to improve grinding, pulp fluidity, and primary breakage of quartz suspensions, especially in the alkaline pH range. These beneficial effects are attributed to the formation of highly surface-active amineaminium complexes in this pH range. In contrast to the above, amine decreased the grinding rate in the acidic pH range owing to increased flocculation of quartz fines in the presence of amine in this pH range. These results show that grinding of quartz can be improved by amine if other conditions such as pH are controlled. Also, the results indicate that the effect of chemical additives on grinding cannot be attributed to a single mechanism, but that the cumulative effect on different pulp properties has to be taken into consideration. Examination of the effect of all properties has led to a better understanding of the mechanisms responsible for the observed grinding aid effects in the present study.     

Selective flocculation of fines

1　ＩＮＴＲＯＤＵＣＴＩＯＮＡｓｔｈｅｅａｒｔｈ’ｓｒｅｓｏｕｒｃｅｓａｒｅｂｅｉｎｇｃｏｎｓｕｍｅｄｓｔｅａｄｉｌｙａｎｄａｓｄｅｍａｎｄｆｏｒｍｉｎｅｒａｌｐｒｏｄｕｃｔｓｃｏｎｔｉｎｕｅｓｔｏｉｎｃｒｅａｓｅ ,ｔｈｅｎｅｅｄｔｏｕｔｉｌｉｚｅｌｏｗ ｇｒａｄｅｏｒｅｓｍｏｒｅｅｆｆｉｃｉｅｎｔｌｙｈａｓｂｅｃｏｍｅｍｏｒｅｓｅｖｅｒｅ .Ｔｈｉｓｉｎｄｅｅｄｒｅ ｓｕｌｔｓｉｎｔｈｅｇｅｎｅｒａｔｉｏｎｏｆａｌａｒｇｅｑｕａｎｔｉｔｙｏｆｆｉｎｅｐａｒｔｉ ｃｌｅｓｄｕｒｉｎｇｍｉｎｉｎｇａｎｄ…     

Adsorption characteristics of polyacrylamide and sulfonate-containing polyacrylamide copolymers on sodium kaolinite

Polyacrylamide and its copolymer containing 6.8 mole % 2-acrylamido-2-methylpropane sulfonic acid were prepared by an irradiation-initiated precipitation polymerization technique. The polymer was characterized by intrinsic viscosity under conditions similar to those used during adsorption measurements. Hydrolytic degradation of the polyacrylamide was found to be negligible under conditions used. The adsorption substrate, sodium kaolinite, was prepared by extensive ion exchange treatment. Equilibrium adsorption of the polymers on the sodium kaolinite was made as a function of polymer concentration, solution pH, ionic strength, and temperature.     

Physico-chemical aspects of grinding: a review of use of additives

The efficiency of energy utilization in tumbling mills is discussed in terms of component processes taking place inside the mill. The past reports on the effect of physicochemical parameters of the environment on mechanical properties and grindability of materials are reviewed. Reported mechanisms explaining such effects are analyzed and possible ways to improve the grinding efficiency, through the use of chemical additives, are also discussed.