Water Resistance of Poly(imide-siloxane) Adhesives: An IGC Surface Energetics Study

Inverse Gas Chromatography was utilized to examine the interaction of water vapor with the surfaces of a polyimide homopolymer and poly(imide-siloxane) random-block copolymers of increasing siloxane content. The studies employed 45-60 meter, thin-polymer-film mega-bore capillary columns to maximize surface area. The free energies of specific surface interaction with water and the dispersive components of the solid surface free energies were determined. An increase in the polymer siloxane content from 0-wt% to 10-wt% resulted in a decrease of approximately 4 kJ/mol in the free energy of water-specific surface interaction. A further increase in siloxane content to 30-wt% was not found to increase surface water resistance significantly. Dispersive components of the solid surface free energies of the copolymers were comparable to values reported for poly(dimethylsiloxane) homopolymer.     

Water Resistance of Poly(Imide-Siloxane) Adhesives: Diffusion Coefficients by Gravimetric Sorption

Diffusion coefficients of water vapor in a polyimide homopolymer and poly(imide-siloxane) multi-block copolymers of different siloxane concentration were determined from gravimetric sorption experiments. Diffusion coefficients were of the order of magnitude of 10^-8 cm²/sec. Higher levels of siloxane incorporation caused a definite increase in the diffusion coefficient, indicating a decreased resistance to water ingression. The increase in diffusion was found to be influenced by siloxane block length and was interpreted in terms of free volume and morphology. The diffusion coefficient of the 10-weight-percent PDMS copolymer, however, was found to be the same within error as that of the polyimide. This and a previous surface study suggested that an increased surface water resistance may be achieved at low siloxane concentrations without greatly increasing the bulk diffusive properties to undesirable levels.     

反气相色谱法研究结晶聚合物的表面性质

采用反相气相色谱法测定了聚乙二醇 (PEG)不同相态结构组成下的色散成分的表面能 Yds,并探讨了 γds 与温度的关系。研究结果表明 :PEG的表面能较低 (32 .39m J- 2 40℃ ) ,在结晶态和熔融非晶态形式下 ,γds 随温度的升高而降低 ;而在 6 7～ 90℃的结晶熔融温度范围内 ,PEG的γds,随温度的升高呈现先降→后升→再下降的趋势 ,特别是当结晶熔融温度达到 6 3℃时 ,PEG的表面能发生明显的转折。     

Measurement of the Surface Free Energy of Amorphous Cellulose by Alkane Adsorption: A Critical Evaluation of Inverse Gas Chromatography (IGC)

Surface energies of amorphous cellulose “beads” were measured by IGC at different temperatures (50 to 100°C) using n-alkane probes (pentane to undecane). The equation of Schultz and Lavielle was applied which relates the specific retention volume of the gas probe to the dispersive component of the surface energy of the solid and liquid, γ^d_s and γ^d_l, respectively, and a parameter (“a”) which represents the surface area of the gas probe in contact with the solids. At 50°C, γ^d_s was determined to be 71.5 mJ/m², and its temperature dependence was 0.36 mJ m^-2 K^-1. Compared with measurements obtained by contact angle, IGC results were found to yield higher values, and especially a higher temperature dependence, d(γ^d_s)/dT. Various potential explanations for these elevated values were examined. The surface energy, as determined by the Schultz and Lavielle equation, was found to depend mostly on the parameter “a”. Two experimental conditions are known to affect the values of “a”: the solid surface and the temperature. While the surface effect of the parameter “a” was ignored in this study, the dependence of the surface energy upon temperature and probe phase was demonstrated to be significant. Several optional treatments of the parameter “a” were modeled. It was observed that both experimental imprecision, but mostly the fundamental difference between the liquid-solid vs the gas-solid system (and the associated theoretical weakness of the model used), could explain the differences between γ^d_s and d(γ^d_s)/dT measured by contact angle and IGC. It was concluded that the exaggerated temperature dependence of the IGC results is a consequence of limitations inherent in the definition of parameter “a”.     

Measurement of the Surface Free Energy of Amorphous Cellulose by Alkane Adsorption: A Critical Evaluation of Inverse Gas Chromatography (IGC)

Surface energies of amorphous cellulose “beads” were measured by IGC at different temperatures (50 to 100°C) using n-alkane probes (pentane to undecane). The equation of Schultz and Lavielle was applied which relates the specific retention volume of the gas probe to the dispersive component of the surface energy of the solid and liquid, γ^d _s and γ^d _l, respectively, and a parameter (“a”) which represents the surface area of the gas probe in contact with the solids. At 50°C, γ^d _s was determined to be 71.5 mJ/m², and its temperature dependence was 0.36 mJ m^?2 K^?1. Compared with measurements obtained by contact angle, IGC results were found to yield higher values, and especially a higher temperature dependence, d(γ^d _s)/dT. Various potential explanations for these elevated values were examined. The surface energy, as determined by the Schultz and Lavielle equation, was found to depend mostly on the parameter “a”. Two experimental conditions are known to affect the values of “a”: the solid surface and the temperature. While the surface effect of the parameter “a” was ignored in this study, the dependence of the surface energy upon temperature and probe phase was demonstrated to be significant. Several optional treatments of the parameter “a” were modeled. It was observed that both experimental imprecision, but mostly the fundamental difference between the liquid-solid vs the gas-solid system (and the associated theoretical weakness of the model used), could explain the differences between γ^d _s and d(γ^d _s)/dT measured by contact angle and IGC. It was concluded that the exaggerated temperature dependence of the IGC results is a consequence of limitations inherent in the definition of parameter “a”.     

IGC study of filler–filler and filler–rubber interactions in silica‐filled compounds

A modification of the existing methods for evaluating the dispersive and specific components of surface free energy (γ_d and γ_s, respectively) was made to investigate filler–rubber and filler–filler interactions by inverse gas chromatography. Four silicas as fillers and various probes that mimic elastomers were employed in this study. It was shown that the pretreatment of silicas with helium could increase γ_d and decrease γ_s. Modification of the silica surface with silane could enhance the dispersive interaction and weaken the specific interaction. The temperature dependence of the interfacial interaction was also investigated, and it was found that lower temperatures favored filler–rubber interactions and mixing efficiency. Tests on different sizes of agglomerates demonstrated the existence of a filler–rubber and filler–filler network. It was also found that γ_d played a role in agglomeration or filler–filler interaction. Our study showed that the larger the specific surface area was, the stronger the dispersive and specific interactions were. The effectiveness of various fillers and elastomer probes was also compared. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2517–2530, 2001     

Water Vapor Permeability of Poly(L‐lactide)/Poly(D‐lactide) Stereocomplexes

PLLA/PDLA blend films with only stereocomplex crystallites as a crystalline species together with pure PLLA and PDLA films with only homo‐crystallites as a crystalline species were prepared, and the effects of enantiomeric polymer blending, crystalline species, and crystallinity on the water vapor permeability were investigated. The WVT coefficient P of PLLA/PDLA blend films was 14–23% lower than that of pure PLLA and PDLA films in the crystallinity X_c range of 0–30%. Amorphous PLLA/PDLA blend films have a much lower P than pure PLLA and PDLA films. The dependence of P on X_c for blend films was stronger for X_c = 0–30% than for X_c = 30–100%. This dependence is discussed using the Nielsen model and the concept of “restricted” (or “restrained”) and “free” amorphous regions.

     

Surface Energy and Lewis Acid-base Characteristics of Lignocellulosic Fibers upon Modification by Chemical Vapor Deposition of Trichloromethylsilane: An Inverse Gas Chromatography Study

The surface of a thermomechanical pulp (TMP), containing 26 wt% of lignin, was modified by silanization with trichloromethylsilane (TCMS) via chemical vapor deposition, and thoroughly analyzed for its physicochemical properties by inverse gas chromatography (attenuated total reflection-Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy being used as complementary tools). For a 2-min TCMS-treated TMP, a decrease of the dispersive component of the surface energy from 38 to 14 mJ m^?2 (at 40°C), and, at the same time, an increase of the Lewis acidic and Lewis basic characters were found. The surface of this sample, modified in a high extent, was similar to that of a bleached kraft pulp (<0.1 wt% of lignin) subjected to the same silanization process, which is suggested as being due, in both cases, to the formation of a methyl-silica coating on the fiber's surface. The new silanized fibers obtained from cheap TMP can be used for the production of a new generation of biocomposites with a variety of matrices.     

聚氯代对二甲苯表面原位引发接枝聚合提升膜表面能的研究

通过钠-萘络合物的处理,在聚氯代对二甲苯膜表面形成自由基,通过表面自由基原位引发甲基丙烯酸甲酯聚合,在薄膜表面引入极性基团以提高膜表面黏结性能。利用红外光谱、X射线衍射和显微镜对接枝改性后薄膜的化学组成和表面形貌进行了表征,运用聚合物膜表面接触角的变化表征了其改性效果。结果表明,甲基丙烯酸甲酯单体由聚氯代对二甲苯膜表面自由基引发,从Cl位置接入,接枝链以共价键的形式与聚氯代对二甲苯膜连接;接枝改性后聚氯代对二甲苯膜表面出现-C=O的特征吸收峰,-CH2的吸收峰随接枝时间的延长而逐渐增大;接枝后薄膜的表面能由28.6 mJ/m2提高到54.1 mJ/m2,拉伸强度由150.5 kPa提高到222.5 kPa。     

Characterization of poly(vinyl methyl ketone) using the inverse gas chromatography method

The inverse gas chromatography method was applied to the semicrystalline polymer poly(vinyl methyl ketone) (PVMK). The method was able to provide valuable information on the thermodynamic and surface properties of PVMK. Thirteen solutes with different chemical properties were used. They provided information on the type and strength of the polymer–solute interactions which were attributed to the melting behavior of PVMK. The melting temperature of PVMK was detected with precision using solutes that interacted strongly with PVMK. The interaction parameters χ₁₂ of PVMK–alkanes over the temperature range 70–180°C were obtained and were shown to be independent of temperature and number of carbons in the alkane series. The dispersive contribution of the surface energy of PVMK was measured as a function of temperature. The values ranged between 29·00 and 18·00 mJ/m². The molar heat of sorption and the molar free energy of adsorption were calculated.     

Solid‐State Polymerization of Poly(ethylene terephthalate): The Effect of Water Vapor in the Carrier Gas

SSP of PET has been thoroughly investigated under the regimes of chemical reaction and particle diffusion control. However, the majority of industrial PET plants operate under conditions of surface by‐product diffusion control, mainly due to recycling cycles of the carrier gas. The presence of residual volatile by‐products in the carrier gas (especially water) may affect adversely the polymerization reaction and the resulting polymer quality. For this reason, the effects caused by varying water vapor content of the carrier gas on the course of the PET SSP are analyzed, with emphasis on the intrinsic viscosity. The presence of small amounts of water in the carrier gas is found to exert a pronounced effect on the course of polymerization, leading to significant reduction of the molar masses of the final product.

     

Rayleigh散射研究部分相容聚苯乙烯／顺丁橡胶合金相结构

用光散射在线采集与分析方法完成了熔融混炼过程中非相容高分子共混物的形态结构分析。选择了聚苯乙烯／顺丁橡胶合金体系；使用了小角前向光散射和小角背散射(在线)技术，用Debye-Bueche光散射理论的结构参数如相关距离ac、平均弦长l、旋转半径Rg和积分不变量Q表征了共混物中分散相尺度和均匀性，讨论了合金体系的相容性。用扫描电子显微镜测定了共混物中分散相尺寸，并与光散射的结果进行了比较。ac、l和Rg的变化规律与显微镜的结果是一致的。用积分不变量Q研究了共混物的均匀性。     

Determination of the interaction parameter χ of poly(ethylene oxide) by gas-liquid chromatography below the melting temperature

The interaction parameter χ of poly(ethylene oxide) in different solvents at temperatures below the melting point (T_m) of the polymer has been determined by means of the solubility parameters of the polymer and solvents at this temperature, chromatographically obtained from their values at higher temperatures (70°–140°C). The value of the interaction parameter so obtained is not only in good agreement with those calculated by other techniques but also independent of the temperature range employed in the chromatographic measurements. Moreover, using the equation-of-state theory formulation, we have determined values of the interaction parameter χ1 for different poly(ethylene oxide)/probe systems and from it the contact interaction energy X₁₂, in the temperature range between 70° and 140°C.     

Water vapor permeability of poly(lactide)s: Effects of molecular characteristics and crystallinity

Amorphous‐made poly(L ‐lactide) [i.e., poly(L ‐lactic acid) (PLLA)], poly(L ‐lactide‐co‐D ‐lactide)[P(LLA‐DLA)](77/23), and P(LLA‐DLA)(50/50) films and PLLA films with different crystallinity (X_c) values were prepared, and the effects of molecular weight, D ‐lactide unit content (tacticity and optical purity), and crystallinity of poly(lactide) [i.e., poly(lactic acid) (PLA)] on the water vapor permeability was investigated. The changes in number‐average molecular weight (M_n) of PLLA films in the range of 9 × 10⁴–5 × 10⁵ g mol^?1 and D ‐lactide unit content of PLA films in the range of 0–50% have insignificant effects on their water vapor transmission rate (WVTR). In contrast, the WVTR of PLLA films decreased monotonically with increasing X_c from 0 to 20%, while leveled off for X_c exceeding 30%. This is probably due to the higher resistance of “restricted” amorphous regions to water vapor permeation compared with that of the “free” amorphous regions. The free and restricted amorphous regions are major amorphous components of PLLA films for X_c ranges of 0–20% and exceeding 30%, respectively, resulting in the aforementioned dependence of WVTR on X_c. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Characterization of biodegradable polymers by inverse gas chromatography. III. Blends of amylopectin and poly(L‐lactide)

The morphology changes and surface thermodynamics of blends of amylopectin (AP)–poly(L ‐lactide) (PLA) were investigated over a wide range of temperatures and compositions using the inverse gas chromatography method. Twenty‐five solutes were selected such as alkanes, acetates, oxy, halogenated, and six‐member ring families. They provided a variety of specific interactions with the blends' surface. The morphology showed two regions, some others showed a de‐polymerization above 130°C. These zones enabled the estimation of T_g and T_m of AP, PLA, and the blends. Blending AP with PLA caused a decrease in AP's T_g value due to the reduction of the degree of crystallinity of the blend. Exothermic values of χ₂₃ were obtained indicating the compatibility of AP and PLA at all temperatures and weight fractions of AP–PLA. The miscibility was favored at 75%AP, only 25%AP–75%PLA composition influenced the degree of crystallinity. The dispersive component of the surface energy of the blends ranged from 16.09 mJ/m² for the pure AP as high as 58.36 mJ/m² at 110°C when AP was mixed with PLA in a 50–50% ratio. The surface energy was at its highest value when the composition was 75% of AP, in good agreement with χ₂₃ values. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation of microporous chlorinated poly(vinyl chloride) membrane in fabric and the characterization of their pore sizes and pore‐size distributions

Chlorinated poly(vinyl chloride) (CPVC)/poly(vinyl pyrrolidone) (PVP) membranes were prepared by using the solvent system tetrahydrofuran (THF)/n‐butyl alcohol (n‐BA) to investigate the possibility of pore size and pore‐size distribution control. The coagulation of CPVC/PVP solution was induced by the exposure to water vapor at 25 (±0.5)°C. The average pore diameter, d_p, and the size distribution of pores on the surface of the membrane were quantified through the image analyzer from the images visualized by field emission scanning electron microscope (FE‐SEM). Surface pore size and distribution of the prepared CPVC/PVP membrane were strongly affected by the relative humidity (RH) in the environment and the content of PVP used as an additive. Particularly, in the case of CPVC membrane without PVP, the mean pore size was 0.15–0.2 μm, depending on the RH. The pore distribution became broad with the increase of the RH. The membranes had open pores as confirmed by the hydraulic permeation experiment. In addition, the water flux and membrane resistance (R_m) were greatly affected by the composition of polymer solution and the RH. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1195–1202, 2002     

The Effect of Nanosized Layered Materials on the Structure-Property Relationship of Poly(aniline)s: An FTIR Kinetic Study

Aniline (ANI) was chemically polymerized in the presence of two different nanosized layered materials, zirconylphosphate (ZP) and molyptic acid (MA) under different experimental conditions with nitrogen purging at 45°C. The effect of nanosized layered materials on the rate of polymerization (R_p) and Fourier transform infra red-relative intensities (FTIR-RI) of benzenoid and quinonoid forms of poly(aniline) (PANI) were tested. The thermal stability and electrical conductivity values were boosted with the help of nanosized materials. High resolution transmission electron microscope (HRTEM) determined the size of nano material and its uniform distribution on the PANI matrix. For the sake of comparison, o-toluidine (OT) was polymerized under the same experimental conditions and its structure-property relationship in the presence of nano materials were also tested and critically compared with PANI systems.     

Chemical Functionalization of Graphene Oxide by Poly(styrene sulfonate) Using Atom Transfer Radical and Free Radical Polymerization: A Comparative Study

Poly(sodium styrenesulfonate)-functionalized graphene was prepared from graphene oxide, using atom transfer radical polymerization and free radical polymerization. In atom transfer radical polymerization route, the amine-functionalized GO was synthesized through hydroxyl group reaction of GO with 3-amino propyltriethoxysilane. Atom transfer radical polymerization initiator was grafted onto modified GO (GO-NH₂) by reaction of 2-bromo-2-methylpropionyl bromide with amine groups, then styrene sulfonate monomers were polymerized on the surface of GO sheets by in situ atom transfer radical polymerization. In free radical polymerization route, the poly(sodium 4-styrenesulfonate) chains were grafted on GO sheets in presence of Azobis-Isobutyronitrile as an initiator and styrene sulfonate monomer in water medium. The resulting modified GO was characterized using range of techniques. Thermal gravimetric analysis, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy results indicated the successful graft of polymer chains on GO sheets. Thermogravimetric analysis showed that the amount of grafted polymer was 22.5 and 31?wt% in the free radical polymerization and atom transfer radical polymerization methods, respectively. The thickness of polymer grafted on GO sheets was 2.1?nm (free radical polymerization method) and 6?nm (atom transfer radical polymerization method) that was measured by atomic force microscopy analysis. X-ray diffractometer and transmission electron microscopy indicated that after grafting of poly(sodium 4-styrenesulfonate), the modified GO sheets still retained isolated and exfoliated, and also the dispersibility was enhanced.