The flame retardant and smoke suppression effect of fullerene by trapping radicals in decabromodiphenyl oxide/Sb2O3 flame‐retarded high density polyethylene

To improve the large release of smoke and heat for brominated flame retardants (BFRs) in fire hazard, fullerene (C₆₀) had been introduced in high density polyethylene (HDPE)/bromine flame retardant (Deca/Sb₂O₃, BFR in short) system in this study. The effects of C₆₀ on the thermal properties, flame retardant properties, rheological behaviors, and smoke release behaviors in HDPE/BFR blends were researched. During polymer thermal degradation, C₆₀ and BFR exhibited the trapping radical ability in condensed phase and gaseous phase, respectively. The intergrated effects of C₆₀ and BFR on the thermal stability and flammability of HDPE were studied by thermo‐gravimetry and cone calorimeter. It was indicated that the introduction of C₆₀ improved the thermal and thermo‐oxidative stability of HDPE/BFR blends. A remarkable advantage of adding C₆₀ was to reduce the peak heat release rate and the average specific extinction area, especially at higher concentration of C₆₀. The analysis of rheological behaviors and pyrolysis products revealed that C₆₀ can capture alkyl radicals, chain radicals, and bromine radicals in the condensed phase, which was in favor of terminating the thermo‐oxidative decomposition and inhibiting the heat and smoke release of HDPE/BFR blends during combustion.     

Improving the flame‐retardant efficiency of aluminum hydroxide with fullerene for high‐density polyethylene

The influence of fullerene (C₆₀) on the flame retardancy and thermal stability of high‐density polyethylene (HDPE)/aluminum hydroxide (ATH) composites was studied. After the addition of three portions of C₆₀ to an HDPE–ATH (mass ratio = 100:120) composite, a V‐0 rating in the UL‐94 vertical combustion test was achieved, and the limiting oxygen index increased by about 2%. The results of cone testing also showed that the addition of C₆₀ effectively extended the time to ignition and the time to maximum heat‐release rate while cutting down the peak heat‐release rate. Thus, fewer flame retardants were needed to achieve a satisfactory flame retardance. Consequently, the adverse effects on the mechanical properties because of the high level of flame‐retardant loading was reduced, as evidenced by the obvious enhancements in the tensile strength, elongation at break, and flexural strength. Electron spin resonance spectroscopy proved that C₆₀ was an efficient free‐radical scavenger toward HO· radicals. Thermogravimetric analysis coupled to Fourier transform infrared spectroscopy demonstrated that in both N₂ and air atmospheres, C₆₀ increased the onset temperature of the matrix by about 10 °C because of its enormous capacity to absorb free radicals evolved from the degradation of the matrix to form crosslinked network, which was covered by aluminum oxide. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44551.     

Fabrication and microstructure of in situ vanadium carbide ceramic particulates-reinforced iron matrix composites

In this work, a novel process that combines infiltration casting with subsequent heat treatment was applied to fabricate in situ vanadium carbide (V₈C₇) ceramic particulates-reinforced iron matrix composites. Based on the differential scanning calorimetry (DSC) data, the as-cast samples were subjected to heat treatment at 1164 °C for different dwelling times (0, 10, 15, and 20 min). The effects of different heat treatment times on the phase evolution, microstructure, and microhardness of the as-prepared composites were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS), and Vickers hardness tester, respectively. The experimental results revealed that only graphite, α-Fe, and V₈C₇ phases dominate in the composite samples after heat treatment at 1164 °C for 20 min. The average microhardness of the as-prepared composites varied among the different regions as follows: 458 HV_0.05 (vanadium wire), 1055 HV_0.05 (composite area), and 235 HV_0.05 (iron matrix). The microhardness of the composite region is four times higher than that of the iron matrix and two times higher than that of the vanadium wire because of the formation of the vanadium carbide phases (V₂C and V₈C₇) as reinforcement within the iron matrix.     

Effect of Friedel–Crafts reaction on the thermal stability and flammability of high‐density polyethylene/brominated polystyrene/graphene nanoplatelet composites

Brominated flame‐retarded high‐density polyethylene (HDPE) composites containing graphene nanoplatelets (GNPs) were prepared via melt blending. A Lewis acid catalyst, anhydrous aluminium chloride (AlCl₃), was added to initiate Friedel–Crafts reaction for promoting the dispersion of the GNPs in the polymer matrix. Transmission electron microscopy images and Raman spectroscopy revealed that the GNPs were partly unfolded and the domains became smaller in the presence of AlCl₃. Limiting oxygen index and microscale combustion calorimetry showed that the incorporation of AlCl₃ into HDPE reduced flammability and slowed down the heat release rate. Thermogravimetric analysis and char residue measurements proved that a uniform dispersion of GNPs was crucial for forming a continuous and compact carbon layer, thus isolating the underlying materials from flame and preventing heat transfer. Rheological and mechanical tests indicated that interfacial adhesion between polymer chains and GNPs was enhanced. © 2014 Society of Chemical Industry     

Differential Scanning Calorimetry Analysis of Goat Fats: Comparison of Chemical Composition and Thermal Properties

The physical–chemical properties, fatty acid composition and thermal properties of goat subcutaneous (SF), tallow (TF) and intestinal (IF) fats were determined. SF differed from other fat types with respect to its lower melting (41.6 °C), lower saponification (190.3 mg KOH/g) and higher iodine (40.4) values as compared to those of other fats. Goat fat types contained palmitic acid (C_16:0), stearic acid (C_18:0), oleic acid (C_18:1ω9) and linoleic acid (C_18:2ω6) as the major components of the fatty acid composition (23.06–23.52, 22.95–39.03, 21.94–36.16 and 1.96–2.22%, respectively). A differential scanning calorimetry (DSC) study revealed that two characteristic peaks were detected in both crystallization and melting curves. Major peaks (T _peak) of TF and IF were similar and determined as 34.02–35.24 and 9.95–10.72 °C, respectively for the crystallization peaks and 15.11–18.26 and 50.70–52.76 °C, respectively for the melting peaks in the DSC curves; but those of SF (27.14 and 4.36 °C for crystallization peaks and 8.39 and 44.93 °C for melting peaks) differed remarkably from those of other fat types.     

α‐Thiophene end‐capped styrene copolymer containing fullerene pendant moieties: Synthesis,characterization, and gas sensing properties

We report the synthesis, characterization, and gas sensing properties of a styrene copolymer bearing α‐thiophene end group and fullerene (C₆₀) pendant moieties P(S‐co‐CMS‐C₆₀). First, the copolymer of styrene (S) and chloromethylstyrene (CMS) monomers was prepared in bulk via a bimolecular nitroxide‐mediated radical polymerization (NMP) technique using benzoyl peroxide (BPO) as the radical initiator and nitroxy‐functional thiophene compound (Thi‐TEMPO) as the co‐radical and this gave α‐thiophene end‐capped copolymer P(S‐co‐CMS). The chloromethylstyrene units of P(S‐co‐CMS) allowed further side‐chain functionalization onto P(S‐co‐CMS). The obtained P(S‐co‐CMS) was then reacted with sodium azide (NaN₃) and this led to the copolymer with pendant azide groups, P(S‐co‐CMS‐N₃), and then grafted with electron‐acceptor C₆₀ via the reaction between N₃ and C₆₀. The final product was characterized by using NMR, FTIR, and UV–vis methods. Electrical characterization of P(S‐co‐CMS‐C₆₀) thin film was also investigated at between 30 and 100 °C as the ramps of 10 °C. Temperature dependent electrical characterization results showed that P(S‐co‐CMS‐C₆₀) thin film behaves like a semiconductor. Furthermore, P(S‐co‐CMS‐C₆₀) was employed as the sensing layer to investigate triethylamine (TEA), hydrogen (H₂), acetone, and ethanol sensing properties at 100 °C. The results revealed that P(S‐co‐CMS‐C₆₀) thin film has a sensing ability to H₂. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43641.     

Synthesis and explosive decomposition of polynitro[60]fullerene

Prolonged treatment of C₆₀ in benzene with very high concentrations of N₂O₄ leads to a new polynitro[60]fullerene whose composition was determined as C₆₀(NO₂)₁₄ by thermogravimetric analysis. The compound is unstable and deflagrates above 170 °C when heated under nitrogen or in air with the release of a considerable amount of heat as observed by the differential thermal analysis and as measured by differential scanning calorimetry. The decomposition steps of C₆₀(NO₂)₁₄ were followed by the thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy analytical technique. At the deflagration point C₆₀(NO₂)₁₄ releases a mixture of nitrogen oxides: NO₂ and NO with minor amounts of N₂O. The deflagration leaves a residue of oxidized carbon which by heating releases CO₂ and CO and at 700 °C is reduced to a carbonaceous matter free from residual oxygenated groups showing also the presence of small amounts (⩽10%) of C₆₀ fullerene.     

Viscoelastic,thermal, and morphological analysis of HDPE/EVA/CaCO<Subscript>3</Subscript> ternary blends

High density polyethylene (HDPE), calcium carbonate (CaCO₃), and ethylene vinyl acetate (EVA) ternary reinforced blends were prepared by melt blend technique using a twin screw extruder. The thermal properties of these prepared ternary blends were investigated by differential scanning calorimetry. The effect of EVA loading on the melting temperature (T _m) and the crystallization temperature (T _C) was evaluated. It was found that the expected heterogeneous nucleating effect of CaCO₃ was hindered due to the presence of EVA. The melt viscosities of the ternary reinforced blends were affected by the % loading of CaCO₃, EVA, and vinyl acetate content. Viscoelastic analysis showed that there is a reduction of the storage modulus (G′) with increasing of EVA loading as compared to neat HDPE resin or to HDPE/CACO₃ blends only. The morphology of the composites was characterized by scanning electron microscopy (SEM). The dispersion and interfacial interaction between CaCO₃ with EVA and HDPE matrix were also investigated by SEM. We observed two main types of phase structures; encapsulation of the CaCO₃ by EVA and separate dispersion of the phases. Other properties of ternary HDPE/CaCO₃/EVA reinforced blends were investigated as well using thermal, rheological, and viscoelastic techniques.     

Preparation and characterisation of BaTiO3 based PTC ceramics with high performance

Abstract

The nanocrystalline BaTiO₃ based PTC powders had been prepared by a simple sol–gel method starting from comparatively cheap raw materials. The powders and ceramics were characterised by thermogravimetry–differential scanning calorimetry, X-ray diffraction and scanning electron microscopy, while electronic properties of the ceramics were also studied. The good material electronic properties were obtained, including a Curie temperature (T _C) of 100°C, a resistivity at room temperature (ρ _25°C) of 18 Ω cm, a high resistivity step ratio (ρ _max/ρ _min) of 1·2×10⁶, a temperature coefficient of resistivity (α ₃₀) of 17% °C^?1 and a withstand voltage intensity (V _b) of 196 V mm^?1.     

Phase segregation behavior in PE/DOP blends and glass‐transition temperatures of polyethylene

Phase segregation behavior in PEs/DOP blends, interactions between PEs and DOP, and glass‐relaxation transitions of PEs were investigated. FTIR, DSC, and TGA data demonstrated that molecular interactions were present between PEs and DOP. DMA data demonstrated that pure PEs each (except HDPE) exhibited two loss maxima at about ?20 and ?120°C but the PEs/DOP blends (including the HDPE/DOP blend) yielded one new loss maximum at about ?60°C. The glass‐relaxation transitions corresponding to the three loss maxima on the DMA curves were designated α (?20°C), β (?60°C), and γ (?120°C) transitions and were attributed to the relaxation of the amorphous phases in the interlamellar, interfibrillar, and interspherulitic regions, respectively, based on DMA, WAXD, SAXS, and POM measurements. The controversial T_g values of PEs and their origin were thus clarified in this study. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3591–3601, 2001     

Epoxy resin/phosphorus‐based microcapsules: Their synergistic effect on flame retardation properties of high‐density polyethylene/graphene nanoplatelets composites

Two types of microcapsule flame retardants are prepared by coating ammonium polyphosphate (APP) and aluminum diethylphosphinate (ADP) with epoxy resin (EP) as the shell via in situ polymerization, and blended with high density polyethylene (HDPE)/graphene nanoplatelets (GNPs) composites to obtain flame‐retardant HDPE materials. Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), and water contact angle results confirm the formation of core–shell structures of EP@APP and EP@ADP. The limiting oxygen index (LOI), vertical burning test (UL‐94), cone calorimetry, and Raman spectroscopy are employed to characterize the HDPE/GNPs composites filled with EP@APP and EP@ADP core–shell materials. A UL94 V‐0 level and LOI of 34% is achieved, and the two flame retardants incorporated in the HDPE/GNPs composite at 20 wt % in total play a synergistic effect in the flame retardancy of the composite at a mass ratio of EP@ADP:EP@APP = 2:1. According to the cone‐calorimetric data, the compounding composites present much lower peak heat release rate (300 kW/m²) and total heat release (99.4 MJ/m²) than those of pure HDPE. Raman spectroscopic analysis of the composites after combustion reveals that the degree of graphitization of the residual char can reach 2.31, indicating the remarkable flame retarding property of the composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46662.     

Characterization of two precursor polyblends: Polyhydroxyamide and poly(amic acid)

Blends of two precursor polymers, polyhydroxy amide (PHA) and poly(amic acid) (PAA), were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The presence of PHA enhanced thermal and mechanical properties of the polyblends. All of the polyblended films showed large endothermic peaks that decreased monotonically with increasing heat treatment temperature. The cyclization onset temperature (T₁), initial decomposition temperature (T₂), and weight residue at 900°C of the polyblends were shown to be in the ranges of 144–146°C, 532–540°C, and 44–45%, respectively. Also, the thermal stabilities were enhanced consistently with increasing annealing temperature from 25 to 250°C. The ultimate strength and initial modulus of the polyblends increased from 84 to 136 MPa and from 2.93 to 5.34 GPa, respectively, with increasing PHA content. Similar to the trend of thermal stability, increasing the annealing temperature of the polyblends increased the tensile properties of the films. The observed tensile properties are discussed in terms of the morphology of the fractured films as studied by scanning electron microscopy (SEM). The degree of crystallinity of the polyblends was characterized as a function of heat treatment temperatures by wide angle X‐ray diffractometry (WAXD).     

Effect of Polar Organic Solvents on Self‐Aggregation of Some Cationic Monomeric and Dimeric Surfactants

Surface and micellization behavior of some cationic monomeric surfactants, viz., cetyldiethylethanolammonium bromide (CDEEAB), cetyldimethylethanolammonium bromide (CDMEAB), tetradecyldiethylethanolammonium bromide (TDEEAB) and dimeric surfactants, i.e., alkanediyl‐α, ω‐bis(dimethylhexadecylammonium bromide) (C₁₆‐s‐C₁₆, 2Br^? where s = 4, 12), butanediyl‐1,4‐bis(dimethyldodecylammonium bromide (C₁₂‐4‐C₁₂, 2Br^?) and 2‐butanol‐1,4‐bis(dimethyldodecylammonium bromide) (C₁₂‐4(OH)‐C₁₂, 2Br^?), was studied in water‐organic solvents [10 and 20 % v/v ethylene glycol (EG) and diethylene glycol (DEG)] by conductivity, surface tension and steady‐state fluorescence methods at 300 K. The main focus of the present work is on the study of the effect of organic solvents on the critical micelle concentration (CMC), Gibbs free energy of micellization (ΔG°_m), Gibbs free energy of transfer (ΔG°_trans), Gibbs adsorption energy (ΔG°_ads) and some interfacial parameters such as the surface excess concentration (Γ_max), minimum area per surfactant molecule (A_min) and surface pressure (π_CMC). The aggregation number (N_agg) and Stern‐Volmer quenching constant (K_SV) were also determined by the steady‐state fluorescence method. It was observed that N_agg decreased with increasing volume percent of organic solvent. The results exhibited an increase in CMC in water‐organic solvents as compared to the respective surfactants in pure water. The negative values of ΔG°_m and ΔG°_ads indicate a spontaneous micellization process. The thermodynamics of micellization revealed that the micellization‐reducing efficiency of glycols increases with the concentration and the number of ethereal oxygens in the glycol.     

Synthesis and rapid expansion in supercritical carbon dioxide through porous sintered metal plate of poly(1,1,2,2‐tetrahydroperfluorodecyl acrylate)

Poly(1,1,2,2‐tetrahydroperfluorodecyl acrylate) [poly(TA‐N)] was synthesized in dry benzene using AIBN as an initiator at 60°C. The effects of the monomer concentration (C_m), initiator concentration (C_i), and reaction time on the polymerization were investigated. The results of DSC and TGA showed that when the C_i remains constant, the higher the C_m value is, the better the thermal character for the product in the range of experiments. When the reaction was conducted for 30 h, polymerization is almost completed. The C_i should remain lower than 0.25 g/100 g monomer when the C_m is lower than 15 g/L. When the C_m is higher than 15 g/L, the C_i should be increased slightly. When the C_m remains constant, it was observed that an increase in the C_i increases the yield (mass of polymer after reaction/mass of monomer before reaction). On the other hand, the melting (T_m) and decomposition (T_d) temperatures of the reaction product decrease, except when the C_m reaches 20 g/L and the reaction time is 30 h. High purity CO₂ was continuously pumped using a high pressure syringe pump. Rapid expansion of poly(TA‐N) in supercritical CO₂ happened under control through a porous sintered metal plate. The poly(TA‐N) morphology was analyzed with a scanning electron microscope. An amorphous polymer was formed at a preexpansion temperature of 45°C. Fibers were formed at temperatures of around 60–80°C. An increase of the temperature slightly increases the particle size. At 105°C, most of the particles are spheres and dendrites. The corresponding CO₂ flow rate upon expansion was 2.5–5.0 ± 0.3 L/min (STP) and the pressure drop was 2 MPa. At the higher CO₂ flow rate, the spheres and dendrites became smaller. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2763–2768, 2003     

Effect of addition of oligobetapinene on morphology,thermal and gas permeation properties in blends with HDPE

Binary blends of high density polyethylene (HDPE) and oligobetapinene (OBP) were prepared by melt mixing. The morphology, thermal and permeability properties of compression molded and slow cooled films are reported. Applying the first‐derivative procedure on differential scanning calorimetry (DSC) traces, we have detected the temperature of glass transition (T_g) of HDPE as a large peak centered from ?125 to ?100°C. In the blends, we observed that the OBP molecules were able to resolve the transition into two components. The lower one was ascribed to the γ‐transition of HDPE, and the upper one was attributed to its T_g. The OBP molecules also formed another transition at a higher temperature. The blends were composed at least of three distinct phases, likely composed of amorphous HDPE with some amount of OBP molecules, amorphous OBP with some polyolefin and crystalline HDPE. The scanning electron microscopy (SEM) investigations revealed segregation of the components. The permeation to CO₂ of plain HDPE and 90/10 blends was similar, but at higher concentrations of oligomer, the value was slightly higher than that of neat HDPE. The decrease of overall crystallinity was counterbalanced by the presence of an OBP rich phase in the blend and could explain the slight increase in permeability of the film blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 315–320, 2004     

Thermal Stability and Crystallization Kinetics of MgO–Al2O3–B2O3–SiO2 Glasses

To support commercialization of the MgO–Al₂O₃–B₂O–SiO₂-based low-dielectric glass fibers, crystallization characteristics of the relevant glasses was investigated under various heat-treatment conditions. The study focused on the effects of iron on the related thermal properties and crystallization kinetics. Both air-cooled and nucleation-treated samples were characterized by using the differential thermal analysis/differential scanning calorimeter method between room temperature and 1200°C. A collected set of properties covers glass transition temperature (T_g), maximum crystallization temperature (T_p), specific heat (ΔC_p), enthalpy of crystallization (ΔH_cryst), and thermal stability (ΔT=T_p—T_g). Using the Kinssiger method, the activation energy of crystallization was determined. Crystalline phases in the samples having various thermal histories were determined using powder X-ray diffraction (XRD) and/or in situ high-temperature XRD method. Selective scanning electron microscope/energy-dispersive spectroscopy analysis provided evidence that crystal density in the glass is affected by the iron concentration. Glass network structures, for air-cooled and heat-treated samples, were examined using a midinfrared spectroscopic method. Combining all of the results from our study, iron in glass is believed to function as a nucleation agent enhancing crystal population density in the melt without altering a primary phase field. By comparing the XRD data of the glasses in two forms (bulk versus powder), the following conclusions can be reached. The low-dielectric glass melt in commercial operation should be resistant to crystallization above 1100°C. Microscopic amorphous phase separation, possibly a borate-enriched phase separating from the silicate-enriched continuous phase can occur only if the melt is held at temperatures below 1100°C, that is, below the glass immiscibility temperature. The study concludes that neither crystallization nor amorphous phase separation will be expected for drawing fibers between 1200°C and 1300°C in a commercial operation.     

Trans-free margarine from highly saturated soybean oil

Highly saturated (HS) soybean oil (SBO), which contained 23.3% palmitic acid (C_16:0) and 20.0% stearic acid (C_18:0), was interesterified at 70°C in preparation for the processing of a trans-free margarine. High-performance liquid chromatography analysis of the triacylglycerides and analysis of the sn-2 fatty acid composition showed no further change after 10 min of interesterification. The interesterified HS SBO had a slip melting point of 34.5°C, compared with 9.5°C in the non-interesterified HS SBO, and increased melting and crystallization temperatures were found using differential scanning calorimetry. Analysis of solid-fat content by nuclear magnetic resonance revealed the presence of only a small amount of solids above 33°C. A 50:50 blend of interesterified HS SBO and SBO with a typical fatty acid composition was used to make the margarine. Compared to commercial soft-tub margarine, the maximal peak force on the texture analyzer of this blended margarine was about 2.3 times greater, the hardness about 2.6 times greater, and adhesiveness about 1.5 times greater. There were small but statistically significant differences (α=0.05) in the sensory properties of spreadability, graininess, and waxiness between the commercial and blended margarines at 4.5°C and, except for graininess, at 11.5°C. These very small differences suggest a potential use for HS SBO in margarine products.     

Determining the Crystal Volume Fraction of BS2 Glass by Differential Scanning Calorimetry and Optical Microscopy

In this work, the crystal volume fraction, α(t), of a barium disilicate (BS₂) glass‐ceramic was carefully investigated by optical microscopy (OM) and differential scanning calorimetry (DSC). X‐ray diffraction experiment revealed that the reflected peaks of the glass‐ceramic, which was prepared by heat treatment at 1000°C for 12 h, were indexed as the low‐temperature orthorhombic sanbornite mineral phase. This result was confirmed by the refinement of the crystal structure parameters. Bulk samples were then heat‐treated in the range of 760°C to 830°C. In each case, the α(t) values obtained by DSC were higher than those determined by OM due to surface crystallization and the formation of new nuclei during the heating/cooling steps in the DSC experiments. OM and DSC techniques were also used to estimate the number of preexisting nuclei, N_q, in a set of samples heat‐treated at 790°C directly in the DSC furnace. At this temperature, it was found that the N_q obtained directly by OM measurements were in reasonable agreement with those calculated from the combination of overall crystallization with crystal growth kinetics.     

Protection of high‐density polyethylene–silicon composites from ultraviolet–visible photodegradation

The extent of the ultraviolet–visible (UV–vis) photoirradiation effect on high‐density polyethylene (HDPE) and HDPE–silicon (Si) composites is reported in terms of the addition of Si microparticles at contents of 0.1, 1, and 5 wt %. A standard accelerated UV–vis exposure was applied over 2750 h, corresponding to 22 months in Florida. Thermogravimetry, differential scanning calorimetry, and Fourier transform infrared spectroscopy were used as reliable techniques for monitoring the quality of the HDPE–Si composites. The increasing addition of Si microparticles delayed the photodegradation of the HDPE–Si composites. Because of their strong light‐scattering effects, Si microparticles blocked the degradation of tertiary carbons of the HDPE backbone and reduced the apparition of vinyl groups; this prevented the structural impoverishment of HDPE–Si composites. Consequently, variations in the crystallization temperature (T_c) and melting temperature (T_m), which were indicators of photodegradation, were not modified. In general, the HDPE–Si composite formulation with 5 wt % Si microparticles was useful for protecting the material from photodegradation and, thus, should be an environmentally friendly, reliable alternative UV–vis blocker. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45439.     

Dynamic mechanical analysis of fibers. I. Effect of experimental variables and material type

Depending upon the fiber material, some of the experimental variables can have a profound effect on the dynamic tensile modulus vs. temperature data. With the use of an experimental fiber (25°C < T_g < 75°C; T_m > 220°C; hot stretched), the effect of several variables, e.g., moisture/volatiles, annealing/relaxation, frequency (strain rate), pretension, and % strain on the modulus retention term [(E_100°C/E_25°C) × 100] have been studied. Of these variables, pretension and especially % strain dramatically increase the modulus retention and this effect is attributed to the elastic orientation under force (EOF), i.e., it exists only in the presence of tensile forces and is reversible. Such an effect was insignificant for Kevlar (T_g ? 375°C) and absent for steel wire. Dynamic modulus measurements at 25°C using sonic techniques also support the EOF phenomenon in polyethylene yarns (T_g ～ ?30°C) but not in Kevlar polymide yarns (T_g ～ 375°C).