Role of epoxidized natural Eucommia ulmoides gum in modifying the interface of styrene‐butadiene rubber/silica composites

Eucommia ulmoides gum (EUG) is a renewable and sustainable polymer, which could be used as rubber or plastic by altering its crosslinking density while the complicated extracting process and nonpolar molecular chains limited its application. In this effort, a novel extraction method was introduced, which could simplify the extraction process of EUG. Then, the extracted EUG‐chloroform (CHCl₃) solution was directly used to prepare epoxidized EUG (EEUG) with an epoxy degree of 40.0% to improve its polarity. The epoxidized natural EUG exhibiting both polar and nonpolar motives had an advantage in working as an interfacial compatibilizer for polymer composites, especially bio‐based composites due to its inherent biocompatibility. Accordingly, the role of EEUG in modifying the interface of styrene‐butadiene rubber (SBR)/silica composites were explored. The results showed that EEUG in SBR/silica composites acted not only as a compatibilizer but also as a constructure generating better mechanical properties than other compatibilizers, such as silane couplings, Si‐69 and KH‐550, and epoxidized natural rubber (ENR). The simplified extracting process and the epoxy modification of EUG would extend its application in rubber materials, medical materials, and biopolymer materials.     

Preparation of epoxidized Eucommia ulmoides gum and its application in styrene‐butadiene rubber (SBR)/silica composites

In this article, we primarily introduced a method to prepare epoxidized Eucommia ulmoides gum (EEUG) and studied its application as interfacial additive in styrene‐butadiene rubber (SBR)/silica composites. We prepared the EEUG from the Eucommia gum extract solution using E. ulmoides leaves pretreated with enzymatic solutions as the raw material, petroleum ether as the solvent, and peracetic acid (CH₃COOOH) as the oxidant under a certain temperature. Accordingly, we focused on studying the effects of a series of factors, such as the mole ratio (γ) of peracetic acid to double bonds of Eucommia gum and reaction time on the epoxidation degree and crystallization degree of Eucommia gum in the epoxidation process, in order to control the properties of the EEUG. Regarding the study of the application of EEUG in SBR/silica composites, we found that the addition of EEUG greatly promoted the properties of SBR/silica composites by improving the dispersion of silica in SBR composites, which possessed excellent mechanical properties, including higher tensile strength, tear strength, 100 and 300% modulus, wear resistance, and low heat buildup. Copyright © 2016 John Wiley & Sons, Ltd.     

Triple shape memory effect in multiple crystalline polyurethanes

Remembering more than one permanent shape is an attractive research topic for shape memory materials (SMMs). In this paper, multiple crystalline shape memory polyurethanes (SMPUs) are prepared with PCL10000 and PTMG2900 by a three‐step polymerization method. DSC and WAXD results show that the obtained polyurethane contains, simultaneously and independently, two kinds of crystals. In addition, it is confirmed through DMA analysis that reversible soft phase and hard domains are formed in the PCL‐PTMG based SMPU system; and two‐step modulus decreases at low temperature range can be obtained in the SMPU with suitable mass proportion of PCL to PTMG, e.g., 1:7. Thus, shape memory effect (SME) can be achieved in this system. Moreover, it is found that the PTMG soft segment dominates the shape memory effect when the PCL mass is lower than that of PTMG; while the PCL soft segment dominates the SME when PCL mass is higher than that of PTMG; and a two‐step programing shape recovery can be achieved when the mass proportion of PCL/PTMG reaches a balance value, e.g., 3:5. Copyright © 2009 John Wiley & Sons, Ltd.     

Binary Modification of Eucommia ulmoides Gum Toward Elastomer with Tunable Mechanical Properties and Good Compatibility

Eucommia ulmoides gum (EUG) was applied in blend rubber with a heavily limited amount because of its duality of rubber and plastic, and an efficient way of triazolinedione (TAD)‐based Alder‐ene reaction was used to improve the elastic properties of EUG. Binary modification of EUG with two TADs containing hexyl and polyhedral oligomeric silsesquioxane (POSS) groups were conducted to generate the modified EUG elastomers with tunable mechanical properties and good compatibility by varying TAD contents. When the low hexyl (1%) and POSS (0.2%) TADs incorporated, the modified EUGs displayed high tensile strength of 36.57 MPa with the elongation at break of 876%, and thus high toughness of 152.14 MJ m^?3. If high contents of hexyl (20%) and POSS (0.2%) TADs employed, the modified EUGs exhibited excellent elongation at break of 1165% and recovery rate of 60%, and especially its loss factor reached up to 0.83?0.65 at 20?70°C. Therefore, the modified EUGs containing the polar urazole and POSS groups should be a novel elastomer with good compatibility, wear resistance, and damping properties. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019     

Actuation design for high‐performance shape memory polyurethanes

A series of shape memory polyurethanes were synthesized from poly(tetramethylene glycol), 4,4‐methylene diphenyl diisocyanate, and 1,3‐butanediol. The prepolymers with different molecular weights (M_c) were capped with 2‐hydroxyl ethylacrylate or 3‐aminopropyltriethoxysilane (APTES) and crosslinked by UV curing or a sol–gel reaction. Variations of the crosslinker functionality (f), subchain density (N), and hard segment content (HSC) produced systematic variations of the glass transition temperature (6–45 °C), accompanied by changes in the mechanical, dynamic mechanical and shape memory properties. More than 95% of shape fixity and 98% of shape recovery up to the fourth cycles were obtained with APTES crosslinked 3000M_c with 30% of HSC. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1473–1479     

UHPLC‐ESI‐MS/MS determination and pharmacokinetics of pinoresinol glucoside and chlorogenic acid in rat plasma after oral administration of Eucommia ulmoides Oliv extract

This study aimed to develop a specific UHPLC‐ESI‐MS/MS method for simultaneous determination and pharmacokinetics of pinoresinol glucoside and chlorogenic acid in rat plasma after oral administration of Eucommia ulmoides . The chromatographic separation was achieved on a Hypersil GOLD column with gradient elution by using a mixture of 0.1% formic acid aqueous solution and acetonitrile as the mobile phase at a flow rate of 200 μL/min. A tandem mass spectrometric detection was conducted using multiple‐reaction monitoring via an electrospray ionization source in negative ionization mode. Samples were pre‐treated by a single‐step protein precipitation with acetonitrile, and bergenin was used as internal standard. After oral administration of 3 mL/kg E. ulmoides extract in rats, the maximum plasma concentrations of pinoresinol glucoside and chlorogenic acid were 57.44 and 61.04 ng/mL, respectively. The times to reach the maximum plasma concentration were 40.00 and 23.33 min for pinoresinol glucoside and chlorogenic acid, respectively. The intra‐ and inter‐day precision (RSD) values for the two analytes were <2.46 and 5.15%, respectively, and the accuracy (RE) values ranged from −12.76 to 0.00. This is the first study on pharmacokinetics of bioactive compounds in rat plasma after oral administration of E. ulmoides extract.     

Mechanical properties of high‐density polyethylene and crosslinked high‐density polyethylene in crude oil and its components

The tensile and stress‐relaxation properties of an uncrosslinked and a loosely silane‐crosslinked high‐density polyethylene exposed to organic “crude‐oil” penetrants were assessed. The measurements were performed on penetrant‐saturated samples, surrounded by the organic liquid throughout the experiment. The penetrant solubilities in the two polymers were similar and in accordance with predicted values based on the solubility parameter method. The stiffness and strength of the swollen samples were significantly less than those of the dry samples, indicating a plasticization of the amorphous component. Raman spectroscopy on polyethylene exposed to deuterated n‐hexane revealed a penetrant‐induced partial melting/dissolution of the crystal surface and an intact crystal core component. The stress‐relaxation rates, within the time frame of the experiment (～1 s to 18 h), were approximately the same, independent of silane‐crosslinks and the presence of penetrants. This indicated that the mechanical α‐relaxation, which is the main relaxation process occurring in the measured time interval, was not affected by the penetrants. Consequently, its rate seemed to be independent of the crystal surface dissolution (decrease in the content of crystal‐core interface). The shape of the “log stress–log time” curves of the swollen samples was, however, different from that of the dry samples. This was most likely attributed to a time‐dependent saturation of penetrant to a higher level associated with the stretched state of the polymer sample. The silane crosslinks affected only the elongation at break, which was less than that of the uncrosslinked material. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 641–648, 2006     

Quadruple‐shape‐memory effect of TPI/LDPE/HDPE composites

Shape‐memory polymers are important smart materials with potential applications in smart textiles, medical devices, and sensors. We prepared trans‐1,4‐polyisoprene, low‐density polyethylene (LDPE), and high‐density polyethylene (HDPE) shape‐memory composites using a simple mechanical blend method. The mechanical, thermal, and shape‐memory properties of the composites were studied. Our results showed that the shape‐memory composites could memorize 3 temporary shapes, as revealed by the presence of broad melting transition peaks in the differential scanning calorimetry curves. In the trans‐1,4‐polyisoprene/LDPE/HDPE composites, the cross‐linked network and the crystallization of the LDPE and HDPE portions can serve as fixed domains, and all crystallizations can act as reversible domains. We proposed a schematic diagram to explain the vital role of the cross‐linked network and the crystallization in the shape‐memory process.     

Shape memory behavior of carbon nanotube‐reinforced trans‐1,4‐polyisoprene and low‐density polyethylene composites

Shape memory composites of trans‐1,4‐polyisoprene (TPI) and low‐density polyethylene (LDPE) with easily achievable transition temperatures were prepared by a simple physical blending method. Carbon nanotubes (CNTs) were introduced to improve the mechanical properties of the TPI/LDPE composites. The mechanical, cure, thermal, and shape memory properties of the TPI/LDPE/CNTs composites were investigated in this study. In these composites, the cross‐linked network generated in both the TPI and LDPE portions acted as a fixed domain, while the crystalline regions of the TPI and LDPE portions acted as a domain of reversible shape memory behavior. We found that CNTs acted as not only reinforced fillers but also nucleation agents, which improved the crystalline degree of the TPI and LDPE portions of the composites. Compared with the properties at the other CNT doses, the mechanical properties of the TPI/LDPE composites when the CNT dose was 1 phr were improved significantly, showing excellent shape memory properties (R_f = 97.85%, R_r = 95.70%).     

Reversible nonlinear conduction behavior for high‐density polyethylene/graphite powder composites near the percolation threshold

The reversible nonlinear conduction (RNC) behavior of high‐density polyethylene/graphite powder composites with various graphite powder volume concentrations slightly above the threshold has been studied. The relationships between the current density (J) and electric field (E) of the composites, as shown in J(E) curves, can be well described by the scaling functions of J/J_c ～ (E/E_c) when E < E_c and J/J_c ～ (E/E_c) when E > E_c, where J_c is the crossover current density and E_c is the crossover electric field. The results indicate that J_c scales with the linear conductivity σ₀ as J_c ～ σ. It is believed that the macroscopic RNC is a combined result of the microscopic conduction processes, involving electronic transporting along carbon chains and tunneling or hopping across thin polymer bridges. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2833–2842, 2001     

Synergistically toughening high‐density polyethylene with calcium carbonate and elastomer

The microstructure, impact strength, and rheological properties of blends consisting of high‐density polyethylene (HDPE) and maleated poly (ethylene‐octene) (POEg) and/or calcium carbonate (CaCO₃) were investigated. The improvement of impact strength of HDPE/POEg was limited due to the high miscibility between them. The introduction of CaCO₃ had a negative impact on the toughness of the matrix because of the poor interfacial adhesion. In ternary blends of HDPE/POEg/CaCO₃, an elastomer layer was formed around CaCO₃ particles due to the strong interaction between POEg and CaCO₃, which improves the HDPE‐CaCO₃ interfacial strength and the toughness of the blends. A significant enhancement of dynamic viscosity, storage modulus, and the low‐shear viscosity were observed as the results of the high miscibility of HDPE with POEg and strong interaction between POEg and CaCO₃. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3213–3221, 2005     

Hydrogel‐coated polyurethane/urea shape memory polymer foams

Shape memory polymers (SMPs) are a class of responsive polymers that have attracted attention in designing biomedical devices because of their potential to improve minimally invasive surgeries. Use of porous SMPs in vascular grafts has been proposed because porosity aids in transfer of fluids through the graft and growth of vascular tissue. However, porosity also allows blood to leak through grafts so preclotting the materials is necessary. Here hydrogels have been synthesized from acrylic acid and N‐hydroxyethyl acrylamide and coated around a porous SMP produced from lactose functionalized polyurea‐urethanes. The biocompatibility of the polymers used to prepare the cross‐linked shape memory material is demonstrated using an in vitro cell assay. As expected, the hydrogel coating enhanced fluid uptake abilities without hindering the shape memory properties. These results indicate that hydrogels can be used in porous SMP materials without inhibiting the shape recovery of the material. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1389–1395     

Electrical breakdown in high‐density polyethylene/graphite nanosheets conductive composites

The electrical breakdown is investigated in high‐density polyethylene/graphite nanosheets (HDPE/GNs) conductive composites. A sample suffers electrical breakdown when the applied field exceeds the critical electrical breakdown field below which the sample reaches a stable state. It is found that the ratio of the critical electrical breakdown resistance to the linear resistance assumes a fixed value Y, which is found to be about 1.30 in HDPE/GNs conductive composites. The value Y is independent of GNs' content, sample size, breakdown cycle, but depends on the property of GNs. The critical breakdown field E_b scales with the resistance R₀ as with the exponent y_b = 0.46 ± 0.02, which is close to the value predicted in mean‐field theory but higher than the value given by the singly connected bonds networks. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 576–582, 2009     

Organic‐montmorillonite modified shape memory epoxy composite

A series of organic‐montmorillonite (OMMT) modified shape memory epoxy (SMEP) composites were prepared for the purpose of application on space deployable structures. Tensile test, dynamic mechanical analysis (DMA), X‐ray diffraction (XRD), scanning electron microscope (SEM), and fold‐deploy shape memory test methods were used to characterize the mechanical, structure, and shape memory properties of these materials. The results showed addition of OMMT could improve the composites' toughness, tensile strength, transition temperature, and shape recovery speed, while shape recovery ratio was unaffected. Composite with 3wt%. OMMT had the optimum combination property. It could fully recover its original shape in about 2 min at 185°C under the maximum bending angle of 180°. Its elongation at break and tensile strength were increased by 835 and 17.4%, respectively, compared to that of neat SMEP. The transition temperature also slightly increased. Copyright © 2010 John Wiley & Sons, Ltd.     

Optimization of the shape memory effect in shape memory polymers

In this article, we show that given a thermoresponsive shape memory polymer, it is possible to alter a number of its properties, such as the recovery temperature, shape fixity ratio, maximum recovery stress, and final recovery stress (and even a right combination of some of them, e.g., the maximum recovery stress and final recovery stress), simply by means of selecting the programming temperature to achieve optimized performance. Some concerns for the implementation in real engineering practice are also discussed. Although the focus is on the case of a fixed maximum strain in programming, alternative programming approaches can be investigated in a similar way for optimized performance as well. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Nonuniversal transport behavior in heterogeneous high‐density polyethylene/graphite nanosheet composites

The direct‐current resistivity of high‐density polyethylene/graphite nanosheet composites above the percolation threshold has been measured and fitted to a power law, which gives a conductivity critical exponent (0.10 ± 0.01) and a percolation threshold (2.97 ± 0.03). These fitted parameters are in disagreement with universal theoretical predictions, and plausible explanations of the observed discrepancies are given. The sample‐to‐sample fluctuations in the relative resistivity seem to obey a power law. This fluctuation behavior, if interpreted in terms of correlation‐length fluctuations, yields a correlation‐length critical exponent, 0.52 ± 0.06, that is consistent with the mean‐field value of 1/2. Interpretations of these experimental results imply that nonuniversal transport behavior in disordered composites is caused by composites being in a nonuniversal scaling regime. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1846–1852, 2006     

A hydrogel‐forming liquid crystalline elastomer exhibiting soft shape memory

Research in the field of liquid crystalline polymers has recently witnessed the introduction of liquid crystalline hydrogels. Here, we report the synthesis and characterization of a new liquid crystalline network featuring elastomeric softness, water‐swelling and shape memory characteristics. By comparing with a nonmesogenic network prepared using the same procedure, we reveal structure–property relationships of the liquid crystalline and crystalline polymer networks. Wide angle and small angle X‐ray scattering studies were used to examine the liquid crystalline ordering in both dry and hydrated states. Such ordering was found to be related to the observed shape memory and actuation (two‐way shape memory) properties and these phenomena are highlighted with demonstrations of shape change in response to heat and water stimuli. This study provides insight into the mechanisms affecting the shape evolution of water activated anisotropic liquid crystalline hydrogels and enables the future design of materials or devices for a variety of applications such as biomaterials interacting with body fluids in a hydrated state. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 38–52     

Electroactive shape memory cyanate/polybutadiene epoxy composites filled with carbon black

Electroactive shape memory composites were synthesized using polybutadiene epoxy(PBEP) and bisphenol A type cyanate ester(BACE) filled with different contents of carbon black(CB). Dynamic mechanical analysis(DMA), scanning electron microscopy(SEM), electrical performance and electroactive shape memory behavior were systematically investigated. It is found that the volume resistivity decreased due to excellent electrical conductivity of CB, in turn resulting in good electroactive shape memory properties. The content of CB and applied voltage had significant influence on electroactive shape memory effect of developed BACE/PBEP/CB composites. Shape recovery can be observed within a few seconds with the CB content of 5 wt% and voltage of 60 V. Shape recovery time decreased with increasing content of CB and voltage. The infrared thermometer revealed that the temperature rises above the glass transition temperature faster with the increase of voltage and the decrease of resistance.     

Influence of modified mesoporous silica SBA‐15 on the flammability of intumescent high‐density polyethylene

This work aims to investigate the fire retardant properties of a novel type of high‐density polyethylene composites. Our intumescent system consists in using classical flame retardants such as ammonium polyphosphate, pentaerythritol in combination with porous mesostructured silica (SBA‐15) fillers. Prior to use, SBA‐15 was chemically modified using different organic and inorganic grafts in order to obtain some specific properties, such as an improved compatibility with the polymer, or different types of surface acidity in order to increase charring reactions. Limiting oxygen index, UL‐94, pyrolysis flow combustion calorimetry and thermogravimetric analysis were used to assess the burning behavior and thermal stability, respectively, of the processed composites. By keeping the total amount of additives always equal to 25 wt%, the better flammability characteristics were in general obtained at low SBA‐15 loadings (<2 wt%). X‐ray diffraction and Fourier transform infrared spectroscopy analyses of the residues showed that the formation of a barrier mainly constituted by crystalline silicon phosphates is probably a key to enhance the fire properties. Further slight improvements brought by the surface modification of SBA‐15 nanofillers are discussed according to type of incorporated particles. Copyright © 2016 John Wiley & Sons, Ltd.