Effects of platinum compounds/superfine aluminum hydroxide/ultrafine calcium carbonate on the flame retardation and smoke suppression of silicone foams

Environmentally friendly, flame-retardant, and relatively low-density (0.25–0.31 g cm⁻³) silicone foams (SiFs) were successfully obtained through dehydrogenation at room temperature (RT = 25.0 °C). Moreover, a flame-retardant system for SiFs was obtained through a synergistic combination of platinum (Pt) compounds, superfine aluminum hydroxide (ATH), and ultrafine calcium carbonate (CC). The smoke suppression, flame retardance, mechanical properties, and thermal stability of SiFs with Pt compounds, ATH, and CC were tested using the limited oxygen index (LOI), UL-94 test, smoke density test, cone calorimeter, and thermogravimetry–Fourier transform infrared spectroscopy. With only 0.6 wt % Pt compounds, the pure SiF achieved the UL-94-V1 rating (3 mm thick), had an LOI value of 29.6%, and the maximum smoke density (MSD) was 6.5%. After adding ATH and CC, SiF composites could achieve the UL-94-V0 rating (3 mm thick), the LOI increase to 35.2%, and MSD decrease by 45%. Furthermore, the SiF with 0.6 wt % Pt compounds, 15.0 wt % ATH, and 15.0 wt % CC exhibited the optimal comprehensive properties for smoke suppression, flame retardance, mechanical performance, and thermal stability. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47679.     

Synergistic flame retardant interplay of phosphorus containing flame retardants with aluminum trihydrate depending on the specific surface area in unsaturated polyester resin

The influence of the specific surface area of aluminum trihydrate (ATH) on the synergism to different phosphorus-based flame retardants (FRs) in unsaturated polyester (UP) resin was investigated. Flammability and thermal stability of UP composites were evaluated with UL-94 vertical burning, thermogravimetric analysis, and cone calorimetry. The morphology of char residues was examined via scanning electron microscopy (SEM). An interaction between crystalline ATH (4.5 m² g⁻¹) and aluminum hypophosphite (AHP) or zinc diethylphosphinate (DEPZn) was observed. When 37 wt % ATH and 8 wt % AHP or DEPZn were incorporated, samples passed V-0 in UL-94 tests. Furthermore, peak of heat release rate (PHRR) and total heat release (THR) were reduced by introduction of phosphorus containing FRs compared to a formulation containing solely crystalline ATH. The incorporation of amorphous ATH (300 m² g⁻¹) leaded to lower UL-94 ratings, using the same amount of AHP or DEPZn. In comparison to crystalline ATH, an addition of phosphorus containing FRs did not lead to a decrease of PHRR and THR for amorphous ATH. SEM of the residues showed that the combination of crystalline ATH with phosphorus species having hydrogen/carbon rich environment formed a dense and tough layer. The combination of crystalline ATH with phosphorus species providing oxygen rich environment gives fragile residues. An incorporation of amorphous ATH leaded to a fragile residue as well. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47270.     

Rigid polyurethane foams with halogen-free flame retardants: Thermal insulation,mechanical, and flame retardant properties

Rigid polyurethane foam (RPUF) composites with triphenyl phosphate (TPhP), aluminum trihydrate (ATH), and zinc borate (ZnB) alone, as well as their binary blends, were prepared via a one-shot process. The amount of flame retardant (FR) or FR blend was varied from 10 to 50% by polyol weight percentage, and the weight fraction of the blends was also fixed at 40%. The effects of additives on thermal insulation, mechanical, and flame retardancy properties of the composites were investigated. Thermal conductivity of the neat foam (RPUF) decreased from 22.53 to 21.04–21.58 mW m⁻¹ K⁻¹. The compressive strength of foams displayed an increase with increasing the amount of TPhP, ATH, and ZnB till 40% by weight. The limited oxygen index values of all foams increased and the flame spread rates of all foams significantly decreased. It was also observed that the flame was self-extinguished in some cases. The cone calorimeter test results indicated that the FR additives improved the flame retardancy of the RPUF. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47611.     

Rheological behavior of collagen/chitosan blended solutions

Understanding the rheological behavior of collagen/chitosan blends is fundamental to design the optimized collagen/chitosan composite materials. Steady shear, dynamic frequency sweep, thixotropy and creep-recovery tests were investigated to characterize the rheological behavior of collagen/chitosan blends as a function of chitosan content (0%–90% [wt/wt]). All the samples showed pseudoplasticity with shear-thinning behavior. With the increase of chitosan, the viscosity significantly decreased from 862.54 to 0.60 Pa s at 0.05 s⁻¹. The storage modulus and loss modulus also decreased while the dynamic denaturation temperature increased from 39.79 to 45.18°C. Besides, the thixotropy weakened and when the chitosan content reached 70%, the final recovery percentage was only 4.6%. The entanglements between collagen fibers observed by atomic force microscopy became weaker. Finally, the corresponding mathematical models were used to simulate the experimental data, and the obtained parameters might provide some useful theoretical guidance for the processing of the collagen/chitosan blended solutions.     

Degradation of flame retardance: A comparison of ethylene-vinyl acetate and low-density polyethylene cables with two different metal hydroxides

The durability of flame retardancy is a challenge for cables over long lifetimes. The degradation of flame retardance is investigated in two kinds of exposures, artificial weathering and humidity. In this basic study, typical mineral flame retardants in two polymers frequently used in cable jackets are investigated to get the fundamental picture. Aluminum hydroxide (ATH) and magnesium hydroxide (MDH) are compared in ethylene-vinyl acetate (EVA), and further in EVA and linear low-density polyethylene (LLDPE) cables containing the same ATH. The changes in chemical structure at the surface are studied through attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), the formation of cracks, and changes in color are investigated. The cone calorimeter and a bench scale fire testing cable module are utilized to evaluate the fire behavior of the cables. Although the flame retardancy deteriorated slightly, it survived harsh exposure conditions for 2000 h. Compared to EVA/MDH and LLDPE/ATH, the fire behavior of EVA/ATH is the least sensitive. Taken together, all of the results converge to estimate that there will be no problem with flame retardancy performance, for materials subjected to natural exposure for several years; the durability of fire retardancy is questionable for longer periods, and thus requires further investigation.     

Preparation of a chitosan‐based flame‐retardant synergist and its application in flame‐retardant polypropylene

A novel flame‐retardant synergist, chitosan/urea compound based phosphonic acid melamine salt (HUMCS), was synthesized and characterized by Fourier transform infrared spectroscopy and ³¹P‐NMR. Subsequently, HUMCS was added to a fire‐retardant polypropylene (PP) compound containing an intumescent flame‐retardant (IFR) system to improve its flame‐retardant properties. The PP/IFR/HUMCS composites were characterized by limiting oxygen index (LOI) tests, vertical burning tests (UL‐94 tests), microscale combustion calorimetry tests, and thermogravimetric analysis to study the combustion behavior and thermal stability. The addition of 3 wt % HUMCS increased the LOI from 31.4 to 33.0. The addition of HUMCS at a low additive amount reduced the peak heat‐release rate, total heat release, and heat‐release capacity obviously. Furthermore, scanning electron micrographs of char residues revealed that HUMCS could prevent the IFR–PP composites from forming a dense and compact multicell char, which could effectively protect the substrate material from combusting. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40845.     

Biodegradable biocomposites from poly(butylene adipate‐co‐terephthalate) and miscanthus: Preparation,compatibilization, and performance evaluation

Miscanthus fibers reinforced biodegradable poly(butylene adipate‐co‐terephthalate) (PBAT) matrix‐based biocomposites were produced by melt processing. The performances of the produced PBAT/miscanthus composites were evaluated by means of mechanical, thermal, and morphological analysis. Compared to neat PBAT, the flexural strength, flexural modulus, storage modulus, and tensile modulus were increased after the addition of miscanthus fibers into the PBAT matrix. These improvements were attributed to the strong reinforcing effect of miscanthus fibers. The polarity difference between the PBAT matrix and the miscanthus fibers leads to weak interaction between the phases in the resulting composites. This weak interaction was evidenced in the impact strength and tensile strength of the uncompatibilized PBAT composites. Therefore, maleic anhydride (MAH)‐grafted PBAT was prepared as compatibilizer by melt free radical grafting reaction. The MAH grafting on the PBAT was confirmed by Fourier transform infrared spectroscopy. The interfacial bonding between the miscanthus fibers and PBAT was improved with the addition of 5 wt % of MAH‐grafted PBAT (MAH‐g‐PBAT) compatibilizer. The improved interaction between the PBAT and the miscanthus fiber was corroborated with mechanical and morphological properties. The compatibilized PBAT composite with 40 wt % miscanthus fibers exhibited an average heat deflection temperature of 81 °C, notched Izod impact strength of 184 J/m, tensile strength of 19.4 MPa, and flexural strength of 22 MPa. From the scanning electron microscopy analysis, better interaction between the components can be observed in the compatibilized composites, which contribute to enhanced mechanical properties. Overall, the addition of miscanthus fibers into a PBAT matrix showed a significant benefit in terms of economic competitiveness and functional performances. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45448.     

Microstructural,mechanical, and thermal‐insulation properties of poly(methyl methacrylate)/silica aerogel bimodal cellular foams

Novel poly(methyl methacrylate) (PMMA)/silica aerogel bimodal cellular foams were prepared by melt mixing and a supercritical carbon dioxide foaming process. The effects of the silica aerogel content on the morphologies and thermal‐insulating and mechanical properties of the foams were investigated by scanning electron microscopy, mechanical tests, and heat‐transfer analysis. The experimental results show that compared to the pure PMMA foam, the PMMA/silica aerogel microcellular foams exhibited more uniform cell structures, decreased cell sizes, and increased cell densities (the densities of the foams were 0.38–0.45 g/cm³). In particular, a considerable number of original nanometric cells (ca. 50 nm) were evenly embedded in the cell walls and on the inner surfaces of the micrometric cells (<10 μm). A 62.7% decrease in the thermal conductivity (0.072 W m⁻¹ K⁻¹) in comparison to that of raw PMMA after 0.5 wt % silica aerogel was added was obtained. Mechanical analysis of the PMMA/silica aerogel foams with 5 and 2 wt % silica aerogel showed that the compressive and flexural strengths were distinctly improved by 92 and 52%, respectively, and the dynamic storage moduli increased. The enhanced performance showed that with the addition of silica aerogel into PMMA, one can obtain thermal‐insulation materials with a favorable mechanical strength. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44434.     

Production and thermomechanical characterization of wool–geopolymer composites

Load‐bearing and thermal insulating wool waste/geopolymer composites with fire‐resistant properties were produced and characterized. Two formulations, with different amounts of wool fibers, corresponding in the final composites to about 23 vol% and 31 vol%, were tested. The composites exhibited an average density of 1.0 g/cm³, with a thermal conductivity of 0.2 W/mK, and compressive and flexural strength around 9 and 5 MPa, respectively. The flexural strength and fracture behavior were improved by the presence of the fibers, which promoted the onset of a toughening mechanism in the material. Results showed that a geopolymer matrix loaded with 23 vol% of wool fibers is suitable as flame‐resistant barrier, as reaction to fire is in class A2 (UNI‐EN 13501‐1), and as insulating structural partition in buildings because it ensures a consistent load‐bearing ability coupled with thermal insulating properties, similarly to other man‐made fiber products, with a considerable gain in terms of cost and environmental impact.     

High interfacial thermal resistance induced low thermal conductivity in porous SiC-SiO2 composites with hierarchical porosity

The incorporation of a thermally insulating secondary phase can significantly increase the interfacial thermal resistance attributed to its low intrinsic thermal conductivity and the creation of multiple phonon scattering interfaces between adjacent SiC particles. The newly developed porous SiC-33 wt% SiO₂ composites with SiO₂ as a thermally insulating secondary phase exhibited a very low thermal conductivity (0.047 Wm⁻¹ K⁻¹, 72.4 % porous), which is an order of magnitude lower than the previously reported lowest thermal conductivity (0.14 Wm⁻¹ K⁻¹, 76.3 % porous) for powder processed porous SiC ceramics and is even lower than the thermal conductivity (0.060 Wm⁻¹ K⁻¹, 87.9% porous) of SiO₂ aerogel. The porous SiC-(16–73 wt%) SiO₂ composites processed from nano β-SiC and a 40 wt% carbon template exhibited a hierarchical (meso-/macro-porous) pore structure that transformed to a trimodal (micro-/meso-/macro-porous) porous structure when polysiloxane was added and sintering was performed at 600–1000 °C in air.     

Synergistic effects of aluminum hydroxide on improving the flame retardancy and smoke suppression properties of transparent intumescent fire-retardant coatings

A series of novel aluminum phosphate ester (APEA) flame retardants were synthesized by the salification of cyclic phosphate ester acid (PEA) with different mass ratios of aluminum hydroxide (ATH) and thoroughly characterized by Fourier transform infrared (FTIR) spectroscopy and ¹H nuclear magnetic resonance spectroscopy. The PEA and APEAs were thoroughly mixed with melamine formaldehyde resin to produce five kinds of transparent fire-retardant coatings. The synergistic effects of ATH on the thermal stability, flame retardancy, and smoke suppression properties of the coatings were investigated by different analytical instruments. The results show that the incorporation of ATH greatly decreases the weight loss, char index, flame spread rating, heat release rate, total heat release, smoke production rate, total smoke release and specific optical density in the coatings applied to plywood boards, which is ascribed to a more compact and intumescent char formed during burning, as determined from digital photographs and scanning electron microscopy images. The synergistic effects of ATH in the coatings depend on the content of ATH, and an excessive amount of ATH diminishes the synergistic effects on the flame retardancy and smoke suppression properties based on fire protection tests and cone calorimeter test. Thermo-gravimetric analysis reveals that the thermal stability and char-forming ability of the coatings gradually improve with increasing loading of ATH. FTIR analysis demonstrates that the incorporation of ATH forms a more phosphorus-rich crosslinked char and aromatic char during burning, thus effectively reducing the mass loss, heat release, and smoke production and exhibiting excellent synergistic flame retardant and smoke suppression effects in the coatings.     

Influence of metal ions on structure and properties of acrylic fibers

The acrylic fibers containing 10.8 wt % of acrylic acid as a comonomer were treated with 5% aqueous solution of sulphates of alkali metals (sodium and potassium) and transition metals (cobalt and nickel) at 90°C for 5 min. The effect of this treatment on the chemical structure, thermal behavior and mechanical properties of this fiber was investigated through FTIR, X-ray, DSC, and TGA techniques. The changes in the chemical structure of the fibers have been noticed as a change in the intensity of characteristic infrared absorption bands. Broadening of the absorption band at 1700 cm⁻¹ due to COO⁻ stretch is also noticed in the case of fibers treated with salts of alkali metals, probably because of formation of a COO⁻M⁺ structure. WAXD studies of the fibers treated with metal salts showed the decrease in the crystallinity of the treated fibers. DSC curves of metalated fibers showed the onset of exothermic cyclization at a higher temperature. The initial modulus of the samples increased after this treatment. The fibers treated with sulphates of alkali metals showed an approximately twofold increase in elongation at break compared to the untreated ones. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1647–1659, 1998     

Lightweight,robust, porous heterocyclic para-aramid aerogel hollow fibers for multifunctional applications

In nature, many fibers with warmth-retention properties, such as the hair of polar bears and rabbits, both have a hollow cross-section structure. The static air in fiber cavities can effectively inhibit heat conduction and serve as an effective thermal insulator. In this work, the high-performance heterocyclic para-aramid polymer was selected as the spinning solution, and aerogel hollow fiber was prepared by coaxial wet spinning and freeze-drying techniques. The effects of spinning solution concentration and lyophilized solvent on the micromorphology, mechanical properties, and specific surface area of heterocyclic para-aramid aerogel hollow fiber (HPAAHF) were systematically studied. The produced HPAAHF possessed excellent mechanical properties (tensible strength ~3.85 MPa), high specific surface area (~ 260.90 m² g⁻¹), and lightweight advantages. The thermal conductivity of HPAAHF was only 0.0278 W m⁻¹ K⁻¹, indicating its excellent thermal insulation properties. The aerogel fabric exhibited outstanding flame retardancy properties, with a total heat release of only 0.7 MJ m⁻² in the cone calorimetric experiment, making it a self-extinguishing fabric. In addition, phase change material was injected into the hollow structure to obtain aerogel-phase change material composite fibers, which exhibited great energy storage prospects. As a result, the high-performance heterocyclic para-aramid polymer-based aerogel hollow fiber was successfully prepared and had multifunctional applications in thermal insulation, flame retardancy, and heat energy storage fields.     

阻燃抑烟型聚乳酸/竹粉复合材料性能研究

采用模压成型法制备了氢氧化铝（ATH）、聚磷酸铵（APP）及APP+ATH阻燃型聚乳酸/竹粉(PLA/BF)复合材料,通过扫描电子显微镜考察了复合材料拉伸断面和燃烧后炭层的微观结构,并对其力学性能、热稳定性能和燃烧性能进行了测试。结果表明,阻燃剂的引入均降低了复合材料的力学性能,但显著提高了热稳定性,600 ℃时复合材料的残炭率分别达到了20.3 %、27.9 %和26.3 %;ATH对复合材料具有显著的抑烟效果,但抑热作用较APP要差,而ATH与APP复合阻燃剂使复合材料兼具较好的抑热作用和抑烟效果。     

Synergistic effects of aluminum hydroxide,red phosphorus,and expandable graphite on the flame retardancy and thermal stability of polyethylene

The flame-retardant low-density polyethylene (LDPE) composites loading aluminum hydroxide (ATH), red phosphorus (RP), and expandable graphite (EG) were successfully prepared. The flame retardancy, the thermo-oxidative stability, and the mechanical property of the composites were investigated. The synergistic effect of ATH, RP, and EG on the flame-retardant property and thermal behavior of LDPE were observed. The limiting oxygen index value of LDPE significantly increased from 17.1% to 25.4% upon the incorporation of 15 wt.% of the mixture of three fillers with ATH:RP:EG mass ratio of 1:1:1; and this composite achieved the V-0 classification of the UL94 vertical burning test. The thermogravimetric analysis of this composite under air atmosphere revealed that its residue weight remained 27.89% at 900°C. Furthermore, the results of tension tests indicated that the surface modification of ATH by magnesium stearate and RP by poly(methylhydrosiloxane) noticeably improved the tensile strength and the elongation of the composite.     

Structural characterization of LDPE/EVA blends containing nanoclay‐flame retardant combinations

The combination of different types of organo‐modified montmorillonite (MMT) with aluminum hydroxide (aluminum trihydrate—ATH), as a flame retardant system for polyethylene‐ethylene vinyl acetate (LDPE/EVA), blends were studied. Five different types of organically modified montmorillonite clays, each with different modifier, were used. The structural characterization was carried out by X‐ray diffraction (XRD) and scanning electron microscopy in transmission mode (STEM). The mechanical and rheological properties were also evaluated. The XRD analysis showed a clear displacement of the d₀₀₁ signal, which indicates a good degree of intercalation, especially for the MMT‐I28 and MMT‐20, from Nanocor and Southern Clay Products, respectively. The presence of ATH and the compatibilizer did not have any effect on the exfoliation of the studied samples. The thermal stability and flame retardant properties were evaluated by thermogravimetric analysis (TGA), limiting oxygen index (LOI—ASTM D2863), and flammability tests (Underwriters Laboratory—UL‐94). The effect of different compatibilizers on the clay dispersion and exfoliation was studied. The results indicated that the addition of montmorillonite makes it possible to substitute part of the ATH filler content while maintaining the flame retardant requirements. The thermal stability of MMT/ATH‐filled LDPE/EVA blends presented a slight increase over the reference ATH‐filled LDPE/EVA blend. Compositions with higher clay content (10 wt %) showed better physicochemical properties. The increased stability of the higher clay content compositions results from the greater inorganic residual formation; this material has been reported to impart better performance in flammability tests. The mechanical properties and flame retardancy remained similar to those of the reference compound. The reduced ATH content resulted in lower viscosities and densities, facilitating the processing of the polymer/ATH/clay compounds. Extrusion of these compounds produced a lower pressure in the extrusion head and required reduced electrical power consumption. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

阻燃剂对热固性酚醛树脂阻燃性能影响的研究

通过氧指数、垂直燃烧等级及产烟率测定研究了氢氧化铝(ATH)、氢氧化镁(MH)、膨胀石墨(EG)、膨胀型阻燃剂(IFR)等以单一或协同复配的形式对酚醛树脂(PF)体系阻燃性能的影响,并采用差热分析(DTA)对体系的微观热行为进行了研究。结果表明,放热量最小的体系为ATH/MH/EG/PF,ATH/MH/EG/IFR/PF体系的氧指数最大,达到96。ATH/MH/PF体系的产烟率最低(72%)。添加阻燃剂后,体系的垂直燃烧等级可提高到UL94V-0级。     

Strengthening of Class Fibers: 11, Ion Exchange *

Soda-alumina-silica glass fibers were ion-exchanged in potassium nitrate at 400°C; their strength was measured before and after exchange. The potassium concentration distribution and the optical retardation were also measured. The results for unetched fibers are consistent with the premise that the kinetics of exchange are controlled by diffusion with D⋍×10⁻¹¹ cm²/s) and with the predictions of thermal stress analysis with a dilation coefficient of 2.8×10⁻⁴ (wt fraction potassium)⁻¹. The existence of a broad maximum in the plot of strengthening of unetched fibers vs time may be explained by the existence of Griffith flaws about 2 μm deep in the unexchanged glass. A deleterious effect from ion exchange was noted with etched fibers, in which even a short (½ h) exchange caused significant weakening.     

Strategies for Preparing Continuous Ultraflexible and Ultrastrong Poly(Vinyl Alcohol) Aerogel Fibers with Excellent Thermal Insulation

Aerogel fibers are thermally insulating and can be woven, so they are expected to form a new generation of smart textiles that can efficiently reduce heat consumption. However, producing continuous aerogel fibers that have the necessary strength and toughness to be woven remains a great challenge. Herein, with the aid of freeze-thaw treatment of poly(vinyl alcohol) (PVA) solution and freeze-spinning technology, continuous PVA aerogel fibers with an aligned porous morphology are prepared in a large-scale. Freeze–thaw treatment greatly contributes to improving the spinnability of the spinning dope of aerogel fibers, which leads to the formation of the continuous fibers. Remarkably, through this process the aerogel fibers achieve ultraflexible and ultrastrong features, which results in excellent weaving ability, as well as attractive mechanical properties that benefit from the cross-linking of PVA molecular chains with the aligned porous structure. More importantly, a textile woven with the special porous structure aerogel fibers shows extraordinary thermal insulation (thermal conductivity as low as 0.026 W m⁻¹ K⁻¹) and infrared stealth. This study illustrates a promising direction for the design of next generation, wearable, intelligent materials that have great potential for personal thermal management applications.     

Synthesis of a phenylene phenyl phosphine oligomer and its flame retardancy for polycarbonate

A novel flame retardant, phenylene phenyl phosphine oligomer (PPPO) was synthesized and its chemical structure was characterized using Fourier transform infrared spectroscopy, ¹H, ¹³C, ³¹P nuclear magnetic resonance spectroscopy and mass spectrometer. PPPO was used to impart flame retardancy to polycarbonate (PC). Combustion behaviors and thermal degradation properties of PC/PPPO system were assayed by limiting oxygen index (LOI), vertical burning test (UL‐94), cone calorimeter test, and thermogravimetric analysis. PC/6 wt % PPPO passed UL‐94 V‐0 rating with 3.0 mm samples and the LOI value was 34.1%, and PC/8 wt % PPPO also passed UL‐94 V‐0 rating with 1.6 mm samples and the LOI value was 36.3%. Scanning electron microscopy reveals that the char properties had crucial effects on the flame retardancy of PC. Mechanical properties and water resistance of PC/PPPO system were also measured. After water resistance test, PC/6 wt % PPPO with 3.0 mm samples and PC/8 wt % PPPO with 1.6 mm samples kept V‐0 rating and mass loss was only 0.2%. The results revealed that PPPO was an efficient flame retardant for PC. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013