Effect of the chemical structure of introduced polymers on the properties of poly-p-phenyleneterephthalamide solutions

Conclusions The effect of the chemical structure of a polymer introduced into a liquid crystal solution of PPTA on some properties of the solutions has been found.Aliphatic and aromatic polyamides exert the least action on these properties as compared with polymers of other classes.Translated from Khimicheskie Volokna, No. 4, pp. 39–40, July–August, 1984.     

Unsteady-state combustion of a granulated solid propellant in a cylindrical channel

The unsteady-state combustion of a granulated solid propellant (GSP) in a cylindrical confined vessel with a uniformly perforated lateral surface is considered. The vessel is placed in a simulation chamber. The GSP specimens are heated by incandescent particles supplied by a hot gas flow through the left perforated face of the vessel. The right face of the vessel is either blank or perforated. The one-dimensional gasdynamic problem is solved by the method of large particles, with the solution of the Euler problem being modified. The one-dimensional thermal problem is solved for individual granules of the propellant in each gasdynamic unit. The behavior of the unsteady-state combustion of the GST affected by variations in the initial temperature and initial burning web of propellant granules as well as the mass and the number of granules in the tested volume has been analyzed numerically. The results of the analysis are reported.Institute of Applied Mathematics, Ural Branch, Russian Academy of Sciences, Izhevsk 426001. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 6, pp. 43–51, November–December, 1994.     

Physical agglomeration behavior in preparation of cellulose‐N‐methyl morpholine N‐oxide hydrate solutions by simple mixing

The different melting temperatures of N‐methyl morpholine N‐oxide (NMMO) hydrates in the cellulose–NMMO hydrate solution may be explained by the rather different crystal structures of NMMO hydrates, which are determined by the amount of the hydrates. The preparative process of cellulose–NMMO hydrate solution may result in cellulose structural change from cellulose I to cellulose II, depending on the amount of the hydrate. Mixtures of cellulose and NMMO hydrate in a blender was changed from the granules to slurry with increasing mixing time at 60–70°C, which is below the melting point of the NMMO hydrate. In the case of 15 wt % cellulose–NMMO hydrate granules, which were made by mixing for 20 min, the melting points of various NMMO hydrates were obtained as 77.8°C (n = 0.83), 70.2°C (n = 0.97), and 69.7°C (n = 1.23), respectively, depending on the hydrate number. However, the melting points of cellulose–NMMO hydrate slurry and solution were shifted lower than those of cellulose granules, while the mixing time of slurry and solution are 25 and 35 min, respectively. These melting behaviors indicate instantaneous liquefaction of the NMMO hydrate and the diffusion of the NMMO hydrate into cellulose during mixing in a blender. When cellulose was completely dissolved in NMMO hydrate, the crystal structure of cellulose showed only cellulose II structure. In the cellulose–NMMO products of granules or slurry obtained by high‐speed mixing, which is a new preparation method, they still retained the original cellulose I structure. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1687–1697, 2004     

Improved properties of molecular composite of nitrile rubber and poly (p-phenylene terephthalamide) by blending with poly (vinyl chloride)

Summary Nitrile rubber (NBR) was reinforced by poly(p-phenylene terephthalamide) (PPTA) with a coprecipitation method from a common solvent of them. PPTA was converted to N-sodium PPTA with sodium hydride in DMSO, forming homogeneous solution. DMF dissolves NBR. Both solutions were blended to form an isotropic solution. The precipitant was NBR reinforced by PPTA which was regenerated from N-sodium PPTA at coagulation as reported previously. The molecular composite thus obtained was mill-blended with poly(vinyl chloride) (PVC) in order to enhance solvent resistant property. The vulcanized composite of NBR/PVC reinforced by PPTA showed higher modulus, higher strength and more improved solvent resistance than the gum stock and the black stock of NBR/PVC. The properties of the molecular composite containing 5phr PPTA found approximately comparable to those of the black stock of NBR/PVC with 30–40phr ISAF carbon black.On Leave from Japan synthetic Rubber Co., Ltd., Higashi-yurigaoka, Assao-ku, Kawasaki 215, Japan     

Properties of spinels formed in highly fired periclase — Spinel refractories

Conclusions In high-temperature firing of periclase-spinel refractories one of the principal aims of a rational technology is achieved: the formation of spinels of magnochromite composition, with the crystal structure of a normal spinel and a high melting point.In such products the modified chrome spinel relates to magnochromite in composition whilst having the structure of normal spinel. The melting point of the modified chrome spinel exceeds 2100°C. The secondary spinels correspond in composition, or are close to, magnochromite. They have the structure of the mixed spinel with a very low degree of rotation, and a melting point of 2050–2070°C.Translated from Ogneupory, No. 8, pp. 41–44, August, 1972.     

Obtaining NPK fertilizers using decomposition of phosphate rock by sulphuric acid

In this study a method for obtaining granular NPK fertilizers of various grades has been established. Kola apatite or Baltic phosphorites were dissolved in 57% H₂SO₄; the resulting slurries were then ammoniated, evaporated and mixed with urea or ammonium nitrate and potassium salts. In some experiments micronutrients (B, Cu, Mo, Co or Mn) were added. The mixtures were dried and granulated. When using urea, granulation was carried out by heating the mixture until partial melting occurred, but the mixtures with ammonium nitrate had to be granulated with the addition of water. The products contained 29–38% fertilizer nutrients (N soluble in water, P₂O₅ soluble in citric acid and K₂O soluble in water) and had a ratio of over 90% of P₂O₅ soluble in citric acid to the P₂O₅ total. The granules were hygroscopic, but little caking occurred. The urea-containing materials produced better granules. Adding micronutrients usually resulted in an improvement in the product quality (an increase in the granule hardness and phosphorus solubility).     

Granulation of finely crystalline ammonium sulphate using calcium oxide and sulphuric acid

Two types of finely crystalline ammonium sulphate (particle size distributions: white type 7% 2–3 mm, 45% 1–2 mm, 48% <1 mm; blue type 1% 2–3 mm, 8% 1–2 mm, 91% <1 mm) were granulated by adding calcium oxide and concentrated sulphuric acid using a rotating drum in the laboratory and pilot plant. The granules had satisfactory physical and chemical properties.The granules made in the pilot plant with 25 kg ammonium sulphate, 0.5 kg CaO, 1.26 litres of water and 0.9 to 1.125 litres of 98.5% H₂SO₄ had 80 to 97% of the granules within the size range of 1–3 mm, abrasion resistance of 0.4 to 0.8% <1 mm, crushing strength of 1.4 to 2.3 kg, critical relative humidity of 65–70%, pH 1.8 to 1.9 and N, S and Ca contents of 19, 24 and 1%. The quality of the granules when stored for 6 months alone or blended together with common fertilizers did not change.A glass house trial using barley demonstrated that the agronomic values of 4 prototype ammonium sulphate granules produced in the laboratory were similar to 3 standard granular ammonium sulphate fertilizers.The process of granulation which could easily be adopted in superphosphate manufacturing plants is recommended for plant scale testing.Provisional New Zealand Patent (No 236,025) applied for.     

Specifics of the thermal oxidative decomposition and burning of fabrics from fibre mixtures

Conclusions It has been shown that on introducing up to 12% by wt. PCA into a fibre from a mixture of two polymers (PPTA and PCA), a marked increase in the fire-protective characteristics of the fibre is observed.Differences have been established in the mechanism of fire-protective action of the phosphorus-containing combustion retarder for materials from a mixture of cellulosic fibre and PPTA and fabrics from a mixture of cellulosic fibre and a fibre from a mixture of PPTA and PCA.Translated from Khimicheskie Volokna, No. 2, pp. 40–42, March–April, 1990.     

ON THE FORMATION OF POLY (P-PHENYLENE TEREPHTHALAMIDE) PULPS FROM STIRRED SOLUTIONS

PPTA (poly (p-phenylene terephthalamide)) may precipitate directly from stirred solution by the use of glycerol or glycerol/water coagulant in fibrous pulp form—short fibers with attached fine fibrils that are called PPTA pulp. Scanning electron micrographs show that the precipitated PPTA pulps have a ribbon-like structure similar to Twaron pulps. The wide-angle X-ray diffraction patters of the resultant pulps exhibit three diffraction peaks at 2θ–20.5, 23.5, and 28.5 corresponding to the {110}, {200}, and {004} crystal faces of PPTA fibers, and the peaks are not as sharp as those of fibers. The process yields PPTA pulps with properties such as specific surface areas and mean length depending on the stirring speed, and the ratio of the viscosity of the PPTA/H₂SO₄ solution to that of the coagulant. The inherent viscosity of the pulps determined by that of the PPTA bulk, which can be easily polycondensated to the desired specification.     

Process for production of calcined phosphate in a grate furnace

Experimental results on bench scale production of calcined phosphate in a grate furnace are presented. Phosphate concentrates were mixed with silica, sodium carbonate and charcoal in varying amounts and granulated (4–6 mm), in some cases with the aid of phosphoric acid. The granules were dried and calcined at 1140–1300°C in a grate furnace. Products with 24.4 to 30.7% total P₂O₅ were obtained with solubility higher than 70% in 2% citric acid.Other experiments were done employing pelletized (4–6 mm) sugar cane bagasse as fuel instead of coal. In these cases, the raw materials silica, sodium carbonate and phosphate concentrates were granulated and then mixed with the pelletized sugar cane bagasse. Two products with 26.1 and 29.4% total P₂O₅ containing respectively 18.8 and 24.0% soluble P₂O₅ (in 2% citric acid solution) were obtained by calcination at temperatures of 930 and 1300°C respectively.The products of both experiments were mainly citric acid-soluble phosphates (rhenanite and andoite) with small amounts of non-reacted apatite.     

The manufacture and evaluation of granular potassium chloride fertilizers

A finely divided red potassium chloride (KCl) (particle size distribution: 79% <0.5 mm, 20% 1-0.5 mm and 1% 1–2 mm) was granulated by adding eight readily available and relatively inexpensive binders using a rotating drum in the laboratory. The binders used were: urea, pulp and paper waste liquor containing lignosulphonate, urea + pulp and paper waste liquor, Borrebond powder (a commercial product containing lignosulphonate), urea + formaldehyde, ammonium sulphate, ammonium sulphate + pulp and paper waste liquor and a waste liquor containing ammonium sulphate from a Ferritin production plant. Of these, except for urea and urea + pulp and paper waste liquor which produced KCl granules having low critical relative humidity at 30°C (CRH) (<55%) and Borrebond which produced KCl granules of low crushing strength (1.1 kg for 2–3 mm granules) the other five binders produced granules with good size distributions, high crushing strengths (2.0–2.5 kg for 2–3 mm granules), CRH (65–70%) and suitable nutrient contents (K, 46–50%, Cl, 42–47%). These values are very close to those of the standard chipped KCl (crushing strength, 2.5 kg; CRH, 65–70%; K, 50%; Cl, 47%).Crushed chipped KCl (74% <1 mm, 25% 1–2 mm, 1% 2–3 mm) when cogranulated in the pilot plant with the 5 binders found successful in the laboratory, produced granules having similar characteristics as the corresponding ones produced in the laboratory. Granules produced both in the laboratory and the pilot plant had lower abrasion resistance (higher % degradation) than chipped KCl. The abrasion resistance however markedly increased when the fines (<1.4 mm) in the granules were removed.Glasshouse trials using barley as test crop demonstrated that the agronomic values of the KCl prototype granules produced with the 5 binders were similar to chipped KCl and granules produced from the feedstock KCl and water.     

Heterogeneity of poly-p-phenylene-1,3,4-oxadiazole solutions

Conclusions The heterogeneity of spinning dopes is mainly caused by impurities contained in the starting raw materials.Heterogeneity of concentrated POD solutions (above 13%) is connected with the formation of crystal solvates.The melting points of the crystal solvates in POD solutions dependls on the polymer content of the solution, the molecular weight of the POD, the sulfuric acid concentration, and the nature of the modifying components.Translated from Khimicheskie Volokna, No. 3, pp. 26–28, May–June, 1986.     

Accelerated determination of the viscosity of poly-p-phenylene terephthalamide

Conclusions A procedure has been proposed for determining the viscosity of dilute PPTA solutions which is based on dissolving the reaction mixture formed in the polymer synthesis process in sulfuric acid.The procedure makes it possible to considerably shorten (by a factor of 10) the time for determining the viscosity of PPTA solutions.Translated from Khimicheskie Volokna, No. 3, pp. 31–32, May–June, 1985.     

New polymer syntheses: 59. Homo-and copolyesters of 4-(4′-hydrophenoxy)benzoic acid

The homopolyester of 4-(4′-hydroxyphenoxy)benzoic acid (poly(4-HPBA)), was prepared under two different reaction conditions and compared with a sample provided by another research group. Depending on the synthetic route, different melting points, d.s.c. traces and crystal lattices were found. However, after repeated heating and cooling, one thermodynamically stable modification with a melting point of 370–375°C can be obtained. Copolyesters of 4-hydroxybenzoic acid and 4-(4′-hydroxyphenoxy)benzoic acid were prepared with various molar ratios either in the melt (condensation in bulk) or in solution. These copolyesters were characterized by elemental analyses, ¹H n.m.r. spectroscopy, d.s.c. measurements, wide-angle X-ray scattering measurements at various temperatures, and optical microscopy. Whereas copolyesters prepared in solution do not melt below 500°C, those prepared by polycondensation in bulk show melting points down to approximately 260°C and form a nematic melt.     

Partially acidulated phosphate rocks: Phosphorus release characteristics

Five phosphate rocks varying in formic acid P solubility from 18.9 to 52.7%, expressed as percentage of total P, were acidulated with phosphoric or sulphuric acids to 0, 20%, 33% and 50% of full acidulation and granulated. In an incubation experiment fertilizer granules of diameter 1–2 mm were mixed with two acid soils and after 1 week incubation soil samples were extracted with a 0.5 M NaOH solution. In a dissipation experiment single fertilizer granules of 4 mm diameter were implanted into soil, incubated for 1 and 4 weeks and inorganic P fractionation in the residual granules and the surrounding soil was performed. Dissipated P was greater than the water soluble P content of the partly acidulated phosphate rock fertilizers indicating the dissolution of the non-acidulated phosphate rocks. The amount of P dissipated was related to the initial water soluble P content and to the formic acid solubility of phosphate rocks used for manufacturing the fertilizers. The P dissipated increased with an increase in soil acidity.     

Heterogeneity in the system cellulose-N-methylmorpholine-N-oxide

Conclusions Data obtained by the turbidity spectrum method indicate a comparatively high heterogeneity of cellulose solutions in N-methylmorpholine-N-oxide monohydrate. The particle size of the disperse phase depends on the temperature-time regime of solution preparation.The concentration of the solution and the degree of polymerization of the cellulose exert an effect on the melting point of the cellulose-MMOMH system.Translated from Khimicheskie Volokna, No. 1, pp. 38–40, January–February, 1987.     

Effect of spinning conditions on the stationary regime region in stretching a jet of a solution of poly-p-phenyleneterephthalamide in an air gap

Conclusions -- The spinning of a yarn from sulfuric acid solutions of poly-p-phenyleneterephthalamide through an air gap in the region of high stretch ratios is unstable because of the onset of pulsations in jet diameter, which is known for polymer melts as stretching resonance.-- The onset of resonance depends on the diameter of the holes in standard cup-shaped spinnerets in the range 0.06–0.1 mm.-- The region of stationary jet-stretching regimes without resonance is considerably expanded in the case of forced cooling of the jet of PPTA solution in the air gap.Deceased.Translated from Khimicheskie Volokna, No. 2, pp. 17–19, March–April, 1993.     

TPC溶液加料低温溶液缩聚合成PPTA的研究

本文详细研究了采用对苯二甲酰氯(TPC)溶液加料(双溶液法)低温溶液缩聚合成聚对苯二甲酰对苯二胺(PPTA)的各种工艺条件对产物对数比浓粘度的影响。结果表明,盐的用量、吡啶的用量和单体浓度与TPC粉末加料具有相同的规律性。由于TPC溶液加料工艺的影响,单体摩尔比、TPC分步加料的使用、溶液放置时间及溶剂在TPC和对苯二胺(PPD)溶液配制时的分配比例等具有其特殊的规律性。在优选的条件下,TPC溶液加料工艺和固体粉末加料工艺一样,可以获得较高对数比浓粘度的PPTA。     

Phase behavior and mechanical properties of poly-p-phenylene terephthalamide/amorphous nylon molecular composites

Poly(p-phenylene terephthalamide) (PPTA)/amorphous nylon (AN) molecular composites were prepared from sulfuric acid solution by rapidly coagulating in distilled water. The regenerated films appear homogeneous and transparent. However, the rod-like and flexible macromolecules are probably entrapped in a single phase during rapid coagulation, thus thermodynamically unstable and undergoing phase segregation upon thermal treatment. The miscibility between PPTA/AN was identified by a dielectric relaxation method. Phase behavior and kinetics of phase separation in PPTA/AN mixtures were thoroughly investigated by time-resolved light scattering as well as optical microscope. A pseudo phase diagram reminiscent of a lower critical solution temperature (LCST) was established by a cloud point measurement. Several temperature-jump experiments were undertaken from ambient to a two-phase temperature region. The low PPTA content molecular composites were prepared by coagulating in a non-solvent, then by compression molding below the phase separation temperatures. The 30 wt% PPTA molecular composite exhibits over three-fold increase in tensile modulus relative to that of the neat AN, however, there is little or no improvement in the tensile strength. On the other hand, by a slight addition of AN into PPTA, the tensile and compressive failures of spun fibers may be improved.     

Shear-induced crystallization of poly(phenylene sulfide)

The crystalline morphology of poly(phenylene sulfide) (PPS) isothermally crystallized from the melt under shear has been observed by polarized optical microscope (POM) equipped with a CSS450 hot-stage. The shish–kebab-like fibrillar crystal structure is formed at a higher shear rate or for a longer shear time, which is ascribed to the tight aggregation of numerous oriented nuclei in the direction of shear. The crystallization induction time of PPS decreases with the shear time, indicating that the shear accelerates the formation of stable crystal nuclei. Under shear, the increase of spherulite growth rate results from highly oriented chains. The melting behavior of shear-induced crystallized PPS performed by differential scanning calorimetry (DSC) shows multiple melting peaks. The lower melting peak corresponds to melting of imperfect crystal, and the degree of crystal perfection decreases as the shear rate increases. The higher melting peak is related to the orientation of molecular chains. These oriented molecular chains form the orientation nuclei which have higher thermal stability than the kebab-like lamellae that are developed later. A new model based on the above observation has been proposed to explain the mechanism of shish–kebab-like fibrillar crystal formation under shear flow.