Viscosity correlation for aqueous polyvinylpyrrolidone (PVP) solutions

Polyvinylpyrrolidone (PVP) is characterized by its K‐value, which is a function of the average molecular weight, the degree of polymerization, and the intrinsic viscosity. The viscosity was measured for aqueous PVP solutions with K‐values ranging from 92.1 to 95.4 and with concentrations from 2 to 3 weight percent. A correlation was determined that relates solution viscosity to the K value and weight percent PVP, which is particularly useful in its use as a photoresist in the manufacture of high resolution display screens. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1153–1155, 2003     

聚乙烯吡咯烷酮的合成及其在定型剂啫喱中的应用

N-乙烯基吡咯烷酮(NVP)通过自由基溶液聚合方法合成聚乙烯基吡咯烷酮(PVP),通过调节引发剂偶氮二异丁腈(AIBN)的用量和催化剂NaHCO3溶液浓度调控PVP的质均分子量,制备出适用于定型剂啫喱所需的PVP。结果表明,当m(AIBN)∶m(NVP)为0.4%、NaHCO3溶液浓度为0.4 mol/L、聚合温度70℃、聚合时间2 h条件下,合成的PVP质均分子量为66 829;其所配制的定型剂啫喱对头发卷曲保持率为86.9%,且具有光泽度好、易清洗、不易发粘、梳理性好等性能。     

Foam glass obtained through high‐pressure sintering

Foam glasses are usually prepared through a chemical approach, that is, by mixing glass powder with foaming agents, and heating the mixture to a temperature above the softening point (10^6.6 Pa s) of the glass. The foaming agents release gas, enabling expansion of the sintered glass. Here, we use a physical foaming approach to prepare foam glass. First, closed pores filled with inert gases (He, Ar, or N₂) are physically introduced into a glass body by sintering cathode ray tube (CRT) panel glass powder at high gas pressure (5‐25 MPa) at 640°C and, then cooled to room temperature. The sintered bodies are subjected to a second heat treatment above the glass transition temperature at atmospheric pressure. This heat treatment causes expansion of the pores due to high internal gas pressure. We found that the foaming ability strongly depends on the gas pressure applied during sintering, and on the kinetic diameters of the gases. The pressure for attaining maximum expansion, that is, lowest density and highest porosity, is found to be around 20 MPa.     

Preparation and characterization of low molecular weight silk fibroin by high‐temperature and high‐pressure method

A low molecular weight silk fibroin powder (LMSF) was prepared through high temperature (200°C) and high pressure (20 kgf/cm²), without any addition of chemicals. The carbonized adducts produced during this process were then removed by treatment with activated charcoal. The yield of LMSF by this preparation method was over 60% after the removal of carbonized adducts by using activated charcoal. Amino acid analysis showed an observable decrease in contents of serine and tyrosine in LMSF prepared by this method, as compared to those prepared by neutral salt. The molecular weight of this LMSF was also observably decreased with an increase in the reaction time. From the measurements of differential scanning calorimeter (DSC) and thermal gravimetric analyzer (TGA), thermal properties of LMSF through high temperature and high pressure were also decreased as compared to those produced by neutral salts. In addition, wide‐angle X‐ray diffraction (WAXD) patterns showed that the crystallinity of LMSF differed from that of the original silk fibroin. It can be said that the preparation method of LMSF in this study is a simple, economical, and environmentally compatible process with many advantages. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2890–2895, 2002     

Microstructural investigation of butt‐fusion joint in high‐density polyethylene pipes using wide‐ and small‐angle X‐ray scattering

The melt fusion zone (MFZ) of polyethylene pipe was investigated employing synchrotron wide‐ and small‐angle X‐ray scattering at various locations in MFZ by changing X‐ray incidence angles to probe three‐dimensional structural features. It was determined that the crystals were oriented in two different modes. One is that the polymer chains are oriented parallel to the joint interface line consistently throughout the MFZ. The other is that the crystals are oriented in particular directions depending on the positions in MFZ. The combination of pressure and melt flow during joining process resulted in such a complex structure. It was notable that the boundary of MFZ against the base material was found to be very different depending on the structures involved such as crystallographic unit orientation, lamellae orientation, crystallinity, and spherulitic morphology. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45668.     

Synthesis and characterization of novel copolymers with the trimethylsilyl group for deep‐UV photoresists

N‐(4‐Acetoxyphenyl) maleimide (APMI) and three kinds of comonomers bearing a trimethylsilyl group were copolymerized at 60°C in the presence of azobisisobutyronitrile (AIBN) as an initiator in 1,4‐dioxane to obtain the three IP, IIP, and IIIP copolymers. These copolymers were removed from the acetoxy group in a transesterification process into new IVP, VP, and VIP copolymers with a pendant hydroxyl group. Two modified processes were adopted to prepare photoresists using these copolymers. The first process involved mixing the dissolution inhibitor, o‐nitrobenzyl cholate, with the new copolymers. Second, o‐nitrobenzyl cholate was introduced into the copolymers using 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) in dimethylformamide (DMF). The cyclic maleimide structure is responsible for the high thermal stability of these copolymers. After irradiation using deep–UV light and development with aqueous Na₂CO₃ (0.01 wt %), the developed patterns showed positive images and exhibited good adhesion to the silicon wafer without using any adhesion promoter. The resolution of these resists was at least 0.8 μm and an oxygen‐plasma etching rate was 1/5.3 to that of hard‐baked HPR‐204. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2791–2798, 2002; DOI 10.1002/app.10255     

水系锌离子电池二氧化锰正极的储能特性及机理研究进展

水系锌离子电池在大型储能等领域具有很高的应用价值和发展前景.目前,水系锌离子电池的正极材料研究主要集中在锰基化合物(如二氧化锰、三氧化二锰、三氧化三锰等)、钒基氧化物以及普鲁士蓝类似物等材料.其中,二氧化锰具有电化学性能优良、储量丰富、价格低廉及安全环保等优势,成为当前最受关注的一类正极材料,近年来得到快速发展.但是,在充放电过程中,二氧化锰晶型多变且伴随其他表面反应,其反应机理复杂且存在一定争议.近两年来,随着研究的不断深入,其电化学反应机理逐渐明晰.围绕二氧化锰的晶体结构特点及其作为水系锌离子电池正极的性能,结合最新研究进展重点讨论了不同晶型二氧化锰的储能机理,并对其未来发展趋势进行了展望.     

Influence of polyvinylpyrrolidone on the hydrophobic properties of partially porous poly(styrene–divinylbenzene) particles for biological applications

For the preparation of polymer particles by free radical, stabilizers are usually present in the reaction mixture to maintain the separation of particles from each other. Polyvinylpyrrolidone (PVP) is one the hydrophilic polymers that has been extensively used as the stabilizer in the polymerization system employing a polar solvent or solvent mixture as the continuous phase. As shown in the present study, the presence of PVP in the later steps could significantly influence the hydrophobic property of partially porous poly(styrene–divinylbenzene) (PS–DVB) particles, prepared by the method of multistep swelling and polymerization involving the use of polymeric porogens. The association of PVP molecules on the particle surface reduced the hydrophobicity and consequently the capability of particles for biological applications. For the reversed‐phase liquid chromatography of penicillin G and its enzymatic hydrolysis product, particles prepared without PVP led to an enhancement in both retention and resolution, compared with particles resulting from the use of PVP. Results from lipase immobilization on these particles also showed that the presence of PVP could shield the hydrophobic groups on the particle surface and then reduce the efficiency of enzyme immobilization. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1818–1824, 2003     

Characterization of the free volume in high‐impact polystyrene/polypropylene and high‐impact polystyrene/high‐density polyethylene blends probed by positron annihilation spectroscopy

The free‐volume properties of high‐impact polystyrene (HIPS)/polypropylene (PP) and HIPS/high‐density polyethylene (HDPE) blends were investigated by means of positron annihilation lifetime spectroscopy (PALS). The measured results show that the free‐volume holes in the semicrystalline polymers, such as PP and HDPE, were not large enough to accommodate the branched chains and the end groups of the macromolecular chains in HIPS to produce favorable interactions between the semicrystalline polymers and the HIPS polymer in these blends; thus immiscible blends were formed. The weak interaction between two dissimilar polymer molecules only took place in the regions between two amorphous phases. In addition, the observed negative deviations of the longest lifetime intensity and the free‐volume fraction were attributed to the influence of the interfacial polarization during PALS measurement. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1507–1514, 2003     

Effect of phenol derivatives on molecular dimensions of poly(N‐vinyl‐2‐pyrrolidone) in aqueous solution

The unperturbed dimensions and thermodynamic parameters of poly(N‐vinyl‐2‐pyrrolidone) (PVP) were studied in aqueous solutions in the presence of certain phenolic cosolutes (phenol, catechol, hydroquinone, resorcinol, and phloroglucinol). The intrinsic viscosities at 25°C and the θ temperature, linear and thermodynamic expansions, and root mean square end to end distances were evaluated for the system that was employed. The sequence was obtained due to the effectiveness of the cosolutes in the order of phloroglucinol > resorcinol > hydroquinone > catechol > phenol. The effects of these cosolutes on the main thermodynamic parameters were reported to be due to the number and position of hydroxyl groups present. The thermodynamic interaction parameter was also evaluated and the enthalpic and entropic contributions were verified. The condition required for the θ temperature to correspond to a Flory interaction parameter of 0.5 was well provided, yielding a θ temperature of almost 0.5 for the system under study. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 473–477, 2002; DOI 10.1002/app.10047     

Effect of the high‐density polyethylene melt index on the microcellular foaming of high‐density polyethylene/polypropylene blends

The effect of high‐density polyethylene (HDPE)/polypropylene (PP) blending on the crystallinity as a function of the HDPE melt index was studied. The melting temperature and total amount of crystallinity in the HDPE/PP blends were lower than those of the pure polymers, regardless of the blend composition and melt index. The effects of the melt index, blending, and foaming conditions (foaming temperature and foaming time) on the void fractions of HDPEs of various melt indices and HDPE/PP blends were also investigated. The void fraction was strongly dependent on the foaming time, foaming temperature, and blend composition as well as the melt index of HDPE. The void fraction of the foamed 30:70 HDPE/PP blend was always higher than that of the foamed 50:50 HDPE/PP blend, regardless of the melt index. The microcellular structure could be greatly improved with a suitable ratio of HDPE to PP and with foaming above the melting temperature for long enough; however, using high‐melt‐index HDPE in the HDPE/PP blends had a deleterious effect on both the void fraction and cell morphology of the blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 364–371, 2004     

X‐ray diffraction studies and phase volume determinations in poly(ethylene glycol)–montmorillonite nanocomposites

Poly(ethylene glycol)–montmorillonite nanocomposites were prepared by both solution and melt intercalation methods with a range of polymer molecular weights and at a range of polymer loadings. Particular attention was given to the reliability of low‐angle X‐ray diffraction results for basal plane spacing and a sound correlation between three diffractometers was obtained (±0.005 nm). Expansion of the basal plane spacing from 1.23 nm to 1.82 nm by solution intercalation was independent of polymer molecular weight in the range 300–20 000. Furthermore, the clay expansion was independent of the method of intercalation; melt intercalation also gave d₀₀₁ = 1.82 nm irrespective of polymer molecular weight. The maximum amount of polymer intercalated by clay and the maximum loading of clay that polymer can sustain were also studied for the determination of nanocomposite formulations. The confined polymer exerts a reduced effective density (670 kg m^?3) in the galleries. Copyright © 2005 Society of Chemical Industry     

Modeling the oxidative degradation of ultra‐high‐molecular‐weight polyethylene

Understanding the sequence of reactions that occur in ultra‐high‐molecular‐weight polyethylene (UHMWPE) following ⁶⁰Co γ irradiation has been the focus of numerous experimental studies. In the study reported here, we have incorporated recent experimental findings into a mathematical model for UHMWPE oxidation. Simulation results for shelf aging and accelerated aging are presented. It is shown that very reasonable simulations of shelf‐aging and accelerated‐aging data can be obtained. It is also shown that simulations of shelf aging in reduced oxygen environments predict that the subsurface peaks of ketones will be shifted to the exterior surface. In vivo aging can be simulated if we assume that the oxygen level in the synovial fluid is about one‐eighth that of atmospheric levels. Some reduced irradiation doses are predicted to significantly reduce the ketone formation for shelf‐aging periods of up to 10 years. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 814–826, 2003     

Cocrystallization behavior of poly(n‐docosyl acrylate) with n‐docosanoic acid by X‐ray and differential scanning calorimetry studies

Cocrystallization behavior of comb‐like poly(n‐docosyl acrylate) (PDA) with n‐docosanoic acid (C₂₂) has been studied by means of differential scanning calorimetry (DSC) and X‐ray diffraction (XRD) methods. The DSC curves of blended samples of neat PDA with C₂₂ show the characteristic melting endotherms that correspond to the melting of the crystallites. DSC measurements of PDA/C₂₂ blends also suggest the existence of another crystalline form induced by the addition of the C₂₂. From the XRD measurements, the existence of hexagonally‐packed crystalline lattice and the phase behavior of PDA/C₂₂ blends at different mole percent are confirmed. Thermal degradation behavior of PDA and its corresponding blends with C₂₂ is studied by thermogravimetric analysis. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2140–2146, 2005     

Successive solution fractionation mechanisms for high‐density polyethylene

BACKGROUND: Preparative fractionation techniques are currently used in order to obtain large amounts of polyethylene fractions. Preparative successive solution fractionation (SSF) and temperature rising elution fractionation (TREF) are compared as regards obtaining, at a multi‐gram scale, low‐dispersity fractions of high‐density polyethylene (HDPE). The operative separation mechanisms during a SSF of a broad HDPE, which are not yet totally elucidated, are also studied in this work. RESULTS: SSF and TREF approaches lead to the separation of HDPE macromolecules according to their molar masses. If very homogeneous fractions (dispersities from 1.1 to 1.3) are isolated in TREF at the lowest elution temperature, the collected mass is too low. At higher elution temperatures, the fractions have too broad a molar mass distribution (dispersities from 2.7 to 3.7). With the SSF procedure, dispersities are not as low as for the first TREF fractions. But, the relative weight fraction is better distributed between the different extraction temperatures. The molar mass distribution exhibits a dispersity of around 1.9. CONCLUSION: The SSF method is the most suitable way to obtain large gram amounts of low‐dispersity (ca 2) HDPE fractions over a wide molar mass range. Complementary gram‐scale rheological characterization is thus possible enabling a better comprehension of the SSF mechanism. Liquid–liquid demixing is the main mechanism in SSF, but its relative importance depends on polymer characteristics and solvent quality. Copyright © 2008 Society of Chemical Industry     

Synthesis of succinylated poly(4‐hydroxystyrene) and its application for negative‐tone photoresist

Atom transfer radical polymerization (ATRP) was used to prepare poly(acetoxystyrene) (PAS) with a controlled molecular weight and narrow polydispersity. Using 1‐phenylethylbromide (PEBr)/CuBr/Cu(0)/2,2′‐bipyridine as an initiating system, the heterogeneous ATRP of 4‐acetoxystyrene was carried out to form PAS as a precursor polymer. The reaction follows the first‐order kinetics with respect to the conversion of monomer. A linear molecular weight (polydispersities Mw/Mn = 1.07–1.27) indicates the “living”/controlled nature of polymerization. The obtained PAS was chemically modified to obtain succinylated poly(hydroxystyrene) (Succ‐PHS). The formulation of Succ‐PHS, crosslinker (benzoguanamine‐formaldehyde), and triphenylsulfonium triflate (TPST) as a photo acid generator (PAG) was carried out by UV irradiation using an i‐line tool. The performance of the resultant polymer as the negative resist pattern photoresist for photolithography was studied with instrumental techniques. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3560–3566, 2007     

Rheology of poly(vinyl chloride) plastisol for super‐high‐shear‐rate processing. II

Capillary flow of poly(vinyl chloride) plastisol was examined at low, high, and superhigh shear rates. At the low to intermediate shear rates, the flow was pseudo‐plastic, but the measured viscosity was not reproducible and widely scattered. The flow behavior was explained as the breakup of the particle network into network‐fragments of varying size. At high shear rates, the measured viscosity was reproducible and increased with shear rate, indicating that the particles were, by and large, separated from each other. At superhigh shear rates, the viscosity decreased with the increase of shear rate. The particles cease to participate in flow because rotation becomes more difficult. A plug‐flow ensues with a thin layer of lubricating plasticizer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012