Dynamic Mechanical Thermal Properties Research Articles

Morphology and properties of poly(vinylidene fluoride)/silicone rubber blends

ABSTRACTBlends of poly(vinylidene fluoride) (PVDF) and silicone rubber (SR) were prepared through melt mixing. The morphology, rheology, crystallization behavior, mechanical properties, dynamic mechanical properties and thermal properties of the PVDF/SR blends were investigated. The blend with 9 wt % of SR showed spherical shape of disperse phase whereas the blend with 27 wt % of SR resulted in irregular shape of rubber phase. The rheology showed that the complex viscosity and storage modulus of the blends decreased with increasing the SR content. The mechanical properties of the blends were decreased with increasing the SR content but that were significantly improved after dynamical vulcanization. The crystallization temperature of PVDF phase in PVDF/SR blends was increased. The incorporation of SR improved the thermal stability of PVDF/SR blends, and the temperature at 10% mass loss of the blends increased to about 489°C compared with 478°C of the pure PVDF. The mass of residual char in experiment of the blends was lower than that obtained in theory. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39945.

Properties of glycerin-thermally modified wood flour/polypropylene composites

This study aimed to investigate the combination effect of glycerin treatment and thermal modification of wood flour on the physical, mechanical, thermal dynamic mechanical properties of wood flour/polypropylene (PP) composite. The morphological aspect was also investigated. The wood flour was first impregnated in the aqueous solution of glycerin, followed by heat treatment at 200°C for 1 h. Then the unmodified or modified wood flour was blended with PP at a weight ratio of 4:6 to prepare composites. Moisture adsorption experiment and X-ray photoelectron spectroscopy analysis of wood flour demonstrated that the hygroscopicity and the free surface hydroxyl groups of wood flour decreased after glycerin-thermal modification. Thickness swelling of the 10% wt glycerin-thermally modified wood flour/PP composite was reduced by 42.8% after 96 h immersion as compared to unmodified control. Evaluation of mechanical properties in impact and flexure modes indicated that glycerin treatment alone had no significant effect, but the combination of glycerin and thermal treatment slightly decreased the strength, with the exception of 10% glycerin and heat modified sample. Dynamic mechanical analysis and scanning electron microscope illustrated the improved interfacial bonding between PP and wood flour modified by 10% glycerin and heat treatment. POLYM. COMPOS., 35:201–207, 2014. © 2013 Society of Plastics Engineers

Waterborne Epoxy/Alkyd Resin Insulation Coatings Modified by Siloxane

The epoxy resin (ER) and 2,3-epoxypropoxypropytrimethoxysilane (KH-560) were used to prepare alkyd resin (AR) insulating coating. The modified waterborne alkyd resin insulating coating was prepared. The dynamic mechanical properties, thermal properties and electrical properties of the composites were characterized by DMA, TG, et al. The results show that the tertiary amine has a good catalyzing effect for this reaction. When the mass ratio of AR with ER is 1 : 1, the glass transform temperature Tg of material is 64.6 °C. When the content of KH-560 is 5% mass fraction of the alkyd resin, the Tg of composites increase 5.6 °C, the initial degradation temperature increased by 63.78 °C; The rs and rv of composites are between 109 ~ 1012 MΩ; the ε and tanδ is between 0.6553 ~ 0.9975 and 0.0025-0.0036, respectively. The pencil hard degree and the impact strength of coating film are all over 5H and 40N, respectively.

Effect of Carbon Nanotube Addition on the Wear Behavior of Basalt/Epoxy Woven Composites

The effect of acid-treated carbon nanotube (CNT) addition on the wear and dynamic mechanical thermal properties of basalt/epoxy woven composites was investigated in this study. Basalt/CNT/epoxy composites were fabricated by impregnating woven basalt fibers into epoxy resin mixed with 1 wt% CNTs which were acid-treated. Wear and DMA (dynamic mechanical analyzer) tests were performed on basalt/epoxy composites and basalt/CNT/epoxy composites. The results showed that the addition of the acid-treated CNTs improved the wear properties of basalt/epoxy woven composites. Specifically, the friction coefficient of the basalt/epoxy composite was stabilized in the range of 0.5-0.6 while it fell in the range of 0.3-0.4 for basalt/CNT/epoxy composites. The wear volume loss of the basalt/CNT/epoxy composites was approximately 68% lower than that of the basalt/epoxy composites. The results also showed that the glass transition temperature of basalt/CNT/epoxy composites was higher than that of basalt/epoxy composites. The improvement of wear properties of basalt/epoxy composites by the addition of acid-treated CNTs was caused by the homogeneous load transfer between basalt fibers and epoxy matrix due to the reinforcement of CNTs.

Preparation and Characterization of Nanocrystalline Cellulose/Natural Rubber (NCC/Nr) Composites

Surface modified nanocrystalline cellulose (NCC) was prepared by silicon-69, and then blended into natural rubber latex to prepare nanocomposites. The nanocomposites properties of tensile properties, tear strength, morphology and thermal dynamic mechanical properties were measured by mechanical property testing, scanning electron microscopy (SEM), and dynamic mechanical analysis (DMA), respectively. The results showed that modified NCC is homogeneously distributed throughout NR matrix, which leads to the enhancement on mechanical properties. Moreover, the storage modulus (E) of modified nanocellulose filled NR is higher than unmodified nanocellulose filled NR, and the tanδ is reversed.

Effect of food/oral-simulating liquids on dynamic mechanical thermal properties of dental nanohybrid light-cured resin composites

ObjectiveThe purpose of this work was the study of the effect of food/oral simulating liquids on the dynamic mechanical thermal properties (viscoelastic properties) of current commercial dental light-cured resin composites characterized as nanohybrids. These nanohybrids were Grandio, Protofill-nano and Tetric EvoCeram. MethodsThe properties were determined under dry conditions (1h at 37°C after light-curing) and also after storage in dry air, distilled water, artificial saliva SAGF® or ethanol/water solution (75vol%) at 37°C for up 1, 7, 30 or 90 days. Dynamic mechanical thermal analysis tests were performed on a Diamond Dynamic Mechanical Analyzer in bending mode. A frequency of 1Hz and a temperature range of 25–185°C were applied, while the heating rate of 2°C/min was selected to cover mouth temperature and the materials’ likely Tg. ResultsStorage modulus, loss modulus and tangent delta were plotted against temperature over this period. The Tg of composites was obtained as the temperature indicated by tanδ peak. Moreover, the maximum height of tanδ peak, the width at the half of tanδ maximum and a parameter known as “ζ” parameter were determined. All composites analyzed 1h after light-curing and 1 day in air or in food/oral simulating liquids showed two Tg. All composites stored for 7, 30 or 90 days in any medium showed unique Tg value. Also among the various properties studied the most sensible in the structural changes of composites seems to be the Tg. SignificanceStorage of composites in dry air at 37°C which is very close to their Tg (40°C) for 1 or 7 days caused post curing reactions, while storage for 30 or 90 days has no further effect on composites. Storage in water or artificial saliva 37°C for 1 or 7 days caused post curing reactions, while storage for 30 or 90 days seems to cause plasticization effect affecting some parameters analogously. Storage in ethanol/water solution (75vol%) 37°C for 1 or 7 days caused also post curing reactions, while storage for 30 or 90 days caused plasticization and/or probable oxidation/hydrolysis of polymeric network.

Preparação e caracterização de biocompósitos baseados em fibra de curauá, biopolietileno de alta densidade (BPEAD) e polibutadieno líquido hidroxilado (PBHL)

Neste trabalho, foram utilizadas fibras de curauá como reforço de matriz termoplástica de biopolietileno de alta densidade. O polietileno foi obtido por polimerização de eteno, gerado do etanol de cana de açúcar. Este polímero é também chamado de biopolietileno (BPEAD), por ser preparado a partir de material oriundo de fonte natural. Desta forma, pretendeu-se contribuir para desenvolver materiais que, dentre outras propriedades, causem menor emissão de CO2 para a atmosfera na sua produção, utilização e substituição, comparativamente a outros materiais. Adicionalmente, polibutadieno líquido hidroxilado (PBHL) foi acrescentado à formulação do compósito, visando a um aumento na resistência à propagação da trinca durante impacto. Os compósitos e as fibras foram caracterizados por várias técnicas, tais como microscopia eletrônica de varredura (MEV), Calorimetria Exploratória Diferencial (DSC), Termogravimetria (TG), além da caracterização dos compósitos quanto à Análise Térmica Dinâmico-Mecânica (DMTA), propriedades mecânicas (impacto e flexão) e absorção de água. A presença das fibras de curauá diminuiu algumas propriedades do BPEAD, como resistência ao impacto. A análise de DMTA mostrou que as fibras geram material mais rígido. Pode-se considerar que a introdução de PBHL na formulação do material foi eficiente, levando a uma resistência ao impacto do compósito BPEAD/PBHL/Fibra maior do que a do compósito BPEAD/Fibra.

Estudo da dispersão de argilas organofílicas em nanocompósitos de prolipropileno obtidos pelo método em solução com auxílio de ultrassom

Nanocompositos de polipropileno PP/OMMT foram preparados com o uso de duas argilas modificadas organofilicamente (C-15A e I-44P) e de um compatibilizante (PP-g-MA) pelo metodo em solucao utilizando-se um banho de ultrassom. O objetivo deste estudo foi compreender a morfologia dos nanocompositos, ou seja, o grau de dispersao destas argilas na matriz de polipropileno, e consequentemente, correlaciona-la com as propriedades finais obtidas. A morfologia dos nanocompositos foi avaliada por Difracao de Raios X (DRX) e Microscopia Eletronica de Transmissao (MET). As propriedades mecânico-dinâmicas e termicas dos nanocompositos foram avaliadas por Analise Mecânico-Dinâmica (DMA) e Calorimetria Diferencial de Varredura (DSC). Analises estatisticas das imagens de transmissao foram realizadas possibilitando a obtencao da razao de aspecto (comprimento/espessura) das particulas de argila.

Thermal Stability and Dynamic Thermal Mechanical Properties of Microcellular Polylactic Acid Scaffolds

Thermal Stability and Dynamic Thermal Mechanical Properties of Microcellular Polylactic Acid Scaffolds

Synthesis and properties of highly hydrophilic waterborne polyurethane‐ureas containing various hardener content for waterproof breathable fabrics

AbstractAs part of an ongoing search for highly hydrophilic waterborne polyurethanes for waterproof breathable fabrics, a waterborne polyurethane [waterborne polyurethane‐ureas (WBPU): P70, the number indicates the poly(ethylene glycol) (PEG) content] dispersion was synthesized from PEG (70 wt %) and dimethylol propionic acid (14 mol %) as the hydrophilic/ionic components, 4,4′‐diisocyanato dicyclohexylmethane as a diisocyanate, ethylenediamine as a chain extender, and aliphatic tri‐isocyanate as a hardener. To determine the best highly hydrophilic WBPU coatings for waterproof breathable fabrics, this study focused on the effect of the hardener content(0–1.2 wt %) in the WBPU P70 sample on the dynamic thermal mechanical properties, contact angle/surface energy, water swelling, water insolubility, and water vapor transmission rate (WVTR). The contact angle, water swelling, glass transition temperature, modulus, and strength increased with increasing hardener content, whereas the surface energy, water insolubility, and WVTR decreased. Sample P70/0.5 (cured sample containing 0.5 wt % of hardener) showed relatively good dimensional stability in water (high water insolubility), strong hydrophilicity (low‐water contact angle/high‐surface energy/high water absorption), and a high WVTR, highlighting its promising applications in waterproof breathable fabrics. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Influence of Polyacrylate on the Compatibility in P(MMA/EA)/PU Semi-IPNs

The Semi-Interpenetrating Polymer Networks(Semi-IPNs) of poly(methyl methyacrylate/ethyl acrylate)(P(MMA/EA)) and polyurethane thermoplastic elastomer (PU) were synthesized by PU and copolymer of methyl methacrylate and ethyl acrylate to improve the compatibility of polymethyl methacrylate(PMMA) and PU Semi-IPNs . The structure and properties were investigated by Fourier transform infrared spectrometer, Solid nuclear magnetic resonance spectrometry, Dynamic mechanical thermal analysis and Mechanical properties. The tensile stress of (P(MMA/EA)/PU)( P(MMA/EA):PU=3:7) can get to 9.6MPa, the additional physical crosslinks and entanglement for Semi-IPNs are the reasons.

Tropical wood polymer nanocomposite (WPNC): The impact of nanoclay on dynamic mechanical thermal properties

In this study, wood polymer nanocomposites (WPNCS) were manufactured from five Malaysian tropical wood species by vacuum-impregnation attended by in situ polymerization using phenol–formaldehyde resin and montmorillomite nanoclay. Percentage weight gain and density of wood polymer nanocomposites depended on wood species. Thermo-mechanical properties of wood samples were investigated by the dynamic mechanical thermal analysis (DMTA) over the temperature range of −100 °C to 200 °C. The intrinsic properties of the components, morphology of the system and the nature of interface between the phases were also determined through DMTA test. Storage modulus (E′) of WPNC samples exhibited significant improvement over the temperature range, in both glassy region and rubbery plateau in relation to their corresponding raw wood samples and wood polymer composites (WPCs). Furthermore, damping (loss tan δ) peaks of all wood species were lowered by PF-Nanoclay system treatment, an indication of improved surface interphase of wood. Dynamic Young’s modulus (Ed) of wood was also calculated using free–free vibration testing. A significant increment was obtained for the PF-Nanoclay impregnated WPNC samples.

Enthalpy relaxation of photopolymerized multilayered thiol-ene films

Multilayered thiol-ene network films with two and three different components were fabricated by spin coating and photopolymerization. The distinctive glass transition temperatures of each layer component were observed at corresponding glass transition regions of each bulk sample. Sub-Tg aging of 10-, 21-, and 32-layered thiol-ene films was investigated in terms of enthalpy relaxation. Enthalpy relaxation of each layer component occurred independently and presented the characteristic time and temperature dependency. Overlapped unsymmetrical bell-shaped enthalpy relaxation distribution having peak maximum at Tg-10°C of each layer component was observed, resulting in broad distribution of enthalpy relaxation over wide temperature range. In addition, enthalpy relaxation of each layer component in the multilayered thiol-ene films was significantly accelerated comparing to that of bulk thiol-ene samples. Dynamic mechanical thermal properties of multilayered thiol-ene films also showed two and three separated glass transition temperature. However, for 32-layered thiol-ene film consisting of three different layer components, glass transition and damping region are overlapped and the width is extended more than 100°C. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Preparation and Application of a New Curing Agent for Epoxy Resin

A new curing agent based on palmitoleic acid methyl ester modified amine (PAMEA) for epoxy resin was synthesized and characterized. Diglycidyl ether of bisphenol A (DGEBA) epoxy resins cured with different content of PAMEA along with diethylenetriamine (DETA) were prepared. The mechanical properties, dynamic mechanical properties, thermal properties, and morphology were investigated. The results indicated that the PAMEA curing agent can improve the impact strength of the cured epoxy resins considerably in comparison with the DETA curing agent, while the modulus and strength of the cured resin can also be improved slightly. When the PAMEA/epoxy resin weight ratio is 30/100, the comprehensive mechanical properties of the cured epoxy resin are optimal; at the same time, the crosslinking density and glass transition temperature of the cured epoxy resin are maximal.

Synthesis and properties of UV curable polyurethane acrylates based on two different hydroxyethyl acrylates

Two kinds of UV curable polyurethane acrylate oligomers (PUPA and PUCA) were synthesized via the addition reaction between isophorone diisocyanate (IPDI) and polyethylene glycol monoacrylate (PEA6) or polycaprolactone modified hydroxyethyl acrylate (PCLA2). The structures of PUPA and PUCA were characterized by Fourier transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance (1H NMR), gel permeation chromatography (GPC) and differential scanning calorimeter (DSC), and the thermal stability and dynamic mechanical thermal properties of their cured films were measured by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA), respectively. The viscosity of the oligomers and mechanical properties of the cured films were also studied. The results show that both oligomers have narrow molecular weight distribution. The viscosity of PUPA is 2.310 Pa·s at 25 °C, while that of PUCA is up to 3.980 Pa·s. The UV cured PUPA and PUCA films have homogeneous phase structure, and the PUCA film shows higher glass transition temperature and storage modulus. Furthermore, the PUCA film possesses better mechanical properties than PUPA, while the latter shows better alkali resistance.

Chitosan/rice straw nanofibers nanocomposites: Preparation, mechanical, and dynamic thermomechanical properties

AbstractNanofibers were isolated from rice straw pulp using ultrahigh friction grinding and high‐pressure homogenization. Chitosan nanocomposites were prepared using the isolated nanofibers at fiber loading from 2.5 to 20% by solution casting and evaporation technique. The effect of nanofiber loading on dry and wet tensile strength, dynamic mechanical thermal properties, and cyrstallinity of chitosan were studied using tensile testing, thermogravimetric analysis, dynamic mechanical thermal analysis, and X‐ray diffraction. Addition of rice straw nanofibers (RSNF) to chitosan resulted in significant improvement in wet and dry tensile strength, and shift of glass transition temperature (Tg) of chitosan matrix to higher values. Chitosan nanocomposites prepared using RSNF (CRSNF) had remarkable wet and dry tensile strength, which could be attributed to presence of both nanofibers and nanosilica particles originally present in rice straw fibers. Addition of RSNF to chitosan did not affect its onset thermal degradation temperature. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Polyvinyl Alcohol/Na-Montmorillonite Nanocomposite Hydrogels Prepared by Freezing–Thawing Method: Structural, Mechanical, Thermal, and Swelling Properties

Physically crosslinked nanocomposite hydrogels based on polyvinyl alcohol (PVA) containing Na-montmorillonite were prepared by the cyclic freezing–thawing method. The primarily exfoliated morphology of prepared nanocomposite hydrogels was confirmed by X-ray diffractometry (XRD) and transmission electron microscopy (TEM) as complementary techniques. It is shown that some interactions developed between the hydroxyl groups of PVA chains and Na-montmorillonite silicate layers in the nanocomposite hydrogels. Differential scanning calorimetry (DSC) results indicated some shifting in the glass transition temperature of the PVA hydrogel in the presence of the nanoclay. Swelling measurements showed that the swelling ratios of the nanocomposite hydrogels were increased either by decreasing the Na-montmorillonite content or by increasing the swelling medium temperature. Dynamic mechanical–thermal properties results showed higher storage modulus for nanocomposite hydrogels in temperature ranges both below and above 0°C. It was also found that the hardness of the nanocomposite hydrogels increased by increasing the nanoclay loading level.

Thermo-mechanical behaviors of epoxy resins reinforced with nano-Al2O3 particles

This study examined the thermo-mechanical behavior of epoxy resins/nano-Al2O3 composites including the curing behavior, thermal stability, dynamic mechanical properties and thermal mechanical properties. The DSC curve peak temperature of the composites was decreased by the addition of nano-Al2O3. The thermal stability of the composites was similar to that of the neat epoxy resins. Dynamic mechanical analysis (DMA) indicated the glass transition temperature of the composites to be approximately 11°C higher than that of the neat epoxy resins. The coefficient of thermal expansion (CTE) of the composites decreased with increasing nano-Al2O3 content.

Novel quinoline-based polyurethane elastomers. The effect of the hard segment structure in properties enhancement

Polyurethane elastomers incorporating a quinoline moiety along their polymeric backbones and aliphatic, aromatic or heterocyclic crosslinkers have been synthesized and characterized. For this, NCO-terminated urethane oligomers were prepared from poly(butylene adipate) diol and methylene diphenyl diisocyanate and were subsequently chain extended with 2,4-quinolinediol and different crosslinkers. This study reports the influence of the different crosslinker chemical structures and the hard segment molar ratio on the thermal and dynamic mechanical thermal properties, as well as on the mechanical properties of these elastomers. The fluorescence spectra of polyurethane elastomers were determined at an excitation wavelength of 290 nm. The different chemical structures of the crosslinkers determine the hard segment cohesion and reduce the mobility of the soft phase, having an important effect on thermal stability and on the mechanical properties of the polyurethane films. Thus the incorporation of aromatic crosslinkers results in polyurethanes with lower elongation and stress at break. The highest mechanical properties were obtained for polyurethanes crosslinked with aliphatic crosslinkers.

Non-isothermal crystallization kinetics and dynamic mechanical thermal properties of poly(butylene succinate) composites reinforced with cotton stalk bast fibers

Degradable poly(butylene succinate) (PBS) was reinforced with cotton stalk bast fibers (CSBF) which had been pre-treated by the continuous steam explosion method. The non-isothermal crystallization kinetics, crystalline structure and spherulitic morphology of neat PBS and CSBF/PBS composites were investigated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarizing optical microscopy (POM). Moreover, the dynamic mechanical thermal properties of neat PBS and CSBF/PBS composites were studied by dynamic mechanical thermal analysis (DMA). The results showed that CSBF played a dual role for acting as both nucleating agents to promote nucleation and physical hindrances to retard the transport of chain segments during the non-isothermal crystallization. In non-isothermal crystallization kinetics, the Ozawa model failed to describe the crystallization behavior of these systems, while Avrami model and Liu model (modified Avrami–Ozawa model) were found applicable. Though the spherulites drastically decreased in size when CSBF were added into PBS matrix, the crystalline structure did not change. In addition, the presence of CSBF largely enhanced the storage modulus of PBS matrix.