Alteration of Bacterial Cellulose Properties by Diacetylglycerol

Bacterial cellulose (BC) was altered by means of 0.5-2.5% w/v diacetylglycerol in acetone-water through impregnation process provided DGBC composites. Results from the scanning electron microscope images, revealed that diacetylglycerol filled the pores of BC, leads to the significant enhanced in hydrophilicity and caused a smoother BC morphology. The addition of diacetylglycerol into BC caused a slightly changed in crystallinity indexes and bring about the reduction in tensile strength and Young's modulus but increased in elongation at break and toughness. The significant reduction of tensile strength and Young's modulus was achieved for DGBC 2.5% as well as for elongation at break and hydrophylicity improvement. Through the impregnation method, diacetylglycerol serves as biodegrada–ble and safe plasticizer, resulted in less rigid and higher ductility DGBC composites.     

Preparation and Properties of Layered Silicate Nanocomposites Based on Ethylene Vinyl Acetate Copolymers

(Nano)composites based on ethylene vinyl acetate copolymers (EVA) and montmorillonite modified by various alkylammonium cations were processed by mechanical kneading. Polymer intercalation and filler exfoliation were evidenced by X‐ray diffraction and transmission electron microscopy, respectively. Nanocomposites tensile properties showed that Young's modulus increases significantly even at very low content of the organo‐modified filler while preserving high ultimate elongation and tensile stress. The matrix thermal stability in air was increased by 40°C and, interestingly, the obtained nanocomposites present flame retardant properties.     

Effect of surface modification of colloidal silica nanoparticles on the rigid amorphous fraction and mechanical properties of amorphous polyurethane–urea–silica nanocomposites

Colloidal silica nanoparticles (NPs) modified with eight different silane coupling agents were incorporated into an amorphous poly(tetramethylene oxide)‐based polyurethane–urea copolymer matrix at a concentration of 10 wt % (4.4 vol %) in order to investigate the effect of their surface chemistry on the structure–property behavior of the resulting nanocomposites. The rigid amorphous fraction (RAF) of the nanocomposite matrix as determined by differential scanning calorimetry and dynamic mechanical analysis was confirmed to vary significantly with the surface chemistry of the NPs and to be strongly correlated with the bulk mechanical properties in simple tension. Hence, nanocomposites with an RAF of about 30 wt % showed a 120% increase in Young's modulus, a 25% increase in tensile strength, a 15% decrease in elongation at break with respect to the neat matrix, which had no detectable RAF, whereas nanocomposites with an RAF of less than 5% showed a 60% increase in Young's modulus, a 10% increase in tensile strength and a 5% decrease in the elongation at break. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2543–2556     

Physical characteristics and properties of waterborne polyurethane materials reinforced with silk fibroin powder

Degummed silk filament was pulverized with a home‐made machine to obtain silk fibroin (SF) powder, and the structure, morphology, and particle size of the SF powder were investigated. The individual spherical particles and aggregates with different morphology of silk fibroin coexisted in water. A waterborne polyurethane (WPU) aqueous dispersion was blended with the SF powder to prepare novel blended materials with improved physical properties. The average particle size and zeta potential of the WPU/SF aqueous dispersions were characterized. The result showed that the WPU/SF dispersion with higher SF content exhibited a less negative zeta potential and a larger average particle size. Furthermore, the effect of SF content on the morphology, miscibility, and mechanical properties of the resulting blended films was studied by scanning electron microscopy, wide‐angle X‐ray diffraction, dynamic mechanical thermal analysis, and tensile testing. The films showed an improved Young's modulus and tensile strength from 0.3 to 33.8 MPa, and 0.6 to 5.2 MPa, respectively, with the increasing of SF up to a content of 26 wt %. The negative charges in the periphery and the small particle size made a good effort on dispersing SF powder into the WPU matrix as small aggregates, and the SF powder led to the efficient strengthening of WPU materials. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 940–950, 2010     

Structure and properties of composites compression‐molded from silk fibroin powder and waterborne polyurethane

The degummed silk filament was pulverized with a home‐made machine to obtain the silk fibroin (SF) powder with the diameter of around 3 µm. The resulting SF powder was blended with waterborne polyurethane (WPU) aqueous dispersion, and then was dried and compression‐molded to prepare novel blended materials with improved miscibility and mechanical properties. WPU acted as a plasticizer and one of the components for the blends during the compression‐molded process. The structure, morphology, and properties of the blended films were investigated. The results indicated that β‐sheet of SF existed in the blended films. The SEM images showed that the cross‐section of the blended films exhibited an overall homogeneous morphology. Furthermore, the transmission electron microscope observation exhibited that some sphere‐like SF particles were well dispersed in the WPU matrix. The hydrogen bond interaction between SF and WPU in the blended films led to an increase of the glass transition temperature for the soft segment of WPU in the blended films. The blended films showed an improved Young's modulus and tensile strength from 1.2 to 288.9 MPa and 0.3 to 16.5 MPa, respectively, with the increasing of SF up to a content of 70 wt%. The hydrogen‐bonding interactions existing in SF and WPU and compression molding method played the important role in improving the miscibility and mechanical properties of the blended films. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis and characterization of compatibilized poly(ϵ‐caprolactone)/granular starch composites

To improve the mechanical properties of granular corn starch‐filled poly(ϵ‐caprolactone) (PCL) compositions, three strategies were investigated including the hydrophobic coating of starch granules by reaction with n‐butyl isocyanate, the addition of PCL‐grafted dextran (PGD) as an amphiphilic compatibilizer, and the use of PCL‐grafted granular starch (PGS). Except for the chemical modification of granular starch by reaction with n‐butyl isocyanate, the synthesis of both PGD and PGS relies upon the controlled ring‐opening polymerization (ROP) of ϵ‐caprolactone (CL) initiated by Al‐alkoxides generated onto the polysaccharide, either dextran or starch particles. While the hydrophobic coating of starch only provides higher tensile strength and elongation at break, these properties as well as Young's modulus and strength at yield of the PCL/starch blends were remarkably increased by locating the PCL‐grafted dextran at the filler/matrix interface. It is however worth pointing out that a tougher and stiffer material was obtained by melt blending PGS and pure PCL. These property changes were analyzed and clearly related to parameters such as filler dispersion, interfacial tension, interfacial adhesion and reinforcement by PCL crystallites.     

Bio-Based Nanocomposites of Cellulose Acetate and Nano-Clay with Superior Mechanical Properties

Summary: Bio-based nanocomposites were manufactured by melt intercalation of nanoclays and cellulose acetate (CA) with and without plasticizer. Glycerol triacetate (triacetin) as plasticizer up to 30 mass%, and different types of organo-modified and unmodified montmorillonites (MMTs) as filler were used. X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), were used to study clay dispersion, intercalation/exfoliation, and structure of the composites. XRD and TEM revealed very good dispersion and exfoliation of modified clay throughout the CA matrix. While for unmodified clay agglomeration and poor dispersion but an intercalated structure was observed. The mechanical properties of injection moulded test bars were determined by a tensile experiment giving tensile strength, Young's modulus and elongation at break. Adding plasticizer facilitated the processing and up to 20 mass%, increased the tensile strength, Young's modulus and elongation at break as well. Higher amount of plasticizer diminished the tensile properties except elongation showing a slight increase. In all plasticized composites, organo-modified clay improved the tensile strength and at the same time, young's modulus and elongation almost remained constant. On the other hand, plasticized CA compounded with unmodified clay revealed lower properties. In a particular case, compounding of unplasticized CA with unmodified clay resulted in superior mechanical properties with a novel structure. So that, in optimum percentage –5 mass%- of unmodified clay, tensile strength and young's modulus increased significantly by 335% and 100%, to 178 MPa and 8.4 GPa, respectively. This is a dramatic improvement in strength and stiffness of CA. Adding organo-modified clay resulted in a little improvement in tensile properties. SEM pictures of the optimum composite showed a core/shell structure with high orientation in the shell part. It is supposed that this behaviour is caused by the interaction between CA hydroxyl groups and free cations existing in the galleries of unmodified clay.     

Tensile and flexural properties of polypropylene composites filled with highly effective flame retardant magnesium hydroxide

The reinforcing effects of highly effective flame retardant magnesium hydroxide (FMX) content on the tensile and flexural properties of filled polypropylene (PP) composites were investigated within the FMX weight fraction range from 5 to 60 wt%. It was found that the Young's modulus and flexural modulus increased approximately linearly while the tensile yield strength and tensile fracture strength decreased slightly with increasing the FMX weight fraction. When the FMX weight fraction was lower than 20%, the tensile elongation at break decreased considerably, and then decreased slightly; the flexural strength increased when the FMX weight fraction was lower than 30%, and then decreased slightly. The tensile properties increased with increasing rate of tension. Moreover, the tensile yield strength of the composites was estimated using an equation proposed in previous work, and good agreement was shown between the predicted and the measured data.     

Mechanical properties of anion exchange membranes by combination of tensile stress–strain tests and dynamic mechanical analysis

The thermomechanical properties of anion exchange polymers based on polysulfone (PSU) quaternized with trimethylamine (TMA) or 1,4‐diazabicyclo[2.2.2]octane (DABCO) and containing hydroxide or chloride anions by tensile stress–strain tests and dynamic mechanical analysis (DMA) have been determined. The reported mechanical properties included the Young's modulus, tensile strength, and elongation at break from tensile tests and the storage and loss modulus and glass transition temperature from DMA. The anion exchange membranes behaved as stiff polymers with Young's modulus in the order of 1 GPa, relatively with high strength (about 30 MPa) and low elongation at break (around 10%) was observed. Tensile tests were also made with membranes exchanged with hydrogen‐carbonate and carbonate anions to control the absence of important carbonation of the OH form. The glass transition temperatures were of the order of 150 °C (PSU‐TMA) or 200 °C (PSU‐DABCO) for the hydroxide form, confirmed by differential scanning calorimetry; they increase further by about 50 K, when hydroxide ions are replaced by chloride. This result and the increase of the storage modulus could be interpreted by the higher hydration of hydroxide ions and the plasticizing effect of water, which reduced the Van der Waals interactions between the macromolecular chains. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1180–1187     

Cure characteristics and properties of NBR composites filled with co‐precipitates of black liquor and montmorillonite

Acrylonitrile‐butadiene rubber (NBR) composites filled with co‐precipitates of black liquor and montmorillonite (CLM) were prepared by mechanical mixing on a two‐roll mill. The cure characteristics, mechanical properties, thermal properties, and thermo‐oxidative aging properties of NBR/CLM composites were evaluated. Scanning electron microscopy and transmission electron microscopy showed that the filler particles were well dispersed in the NBR/CLM composites. The scorch time and optimum cure time increase with increasing filler loading. A remarkable enhancement in tensile strength, elongation at break, 300% modulus, and shore “A” hardness was also observed. When the loading of CLM was 40 parts per hundred rubbers, it showed about seven times increase in tensile strength, about 1.8 times increase in elongation at break, about three times increase in 300% modulus, and about 1.3 times increase in shore A hardness, respectively, as compared with those of pure cured NBR. Thermal properties and thermal oxidative aging properties, in general, were also improved with loading of this novel filler. Copyright © 2011 John Wiley & Sons, Ltd.     

Influence of imide functionalized organo‐modified Mg‐Al layered double hydroxide on the thermal and mechanical properties of new aliphatic‐aromatic poly (amide‐imide)

A new dicarboxylic acid modified Mg‐Al LDH (DLDH) containing imide groups was prepared and its effects on the thermal and mechanical properties of the new synthesized aliphatic‐aromatic poly (amide‐imide) (PAI) were investigated via preparation of PAI/nanocomposite films by solution casting method. The results of X‐ray diffraction (XRD), field emission‐scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM) showed a uniform dispersion for LDH layers into the PAI matrix. For comparison, the effects of polyacrylic acid‐co‐poly‐2‐acrylamido‐ 2‐methylpropanesulfonic acid (PAMPS‐co‐PAA) modified Mg‐Al LDH (ALDH) on the PAI properties were also studied. The thermogravimetric analysis (TGA) results exhibited that the temperature at 5 mass% loss (T₅) increased from 277 °C to 310 °C for nanocomposite containing 2 mass% of DLDH, while T₅ for nanocomposite containing 2 mass% of ALDH increased to 320 °C, along with the more enhancement of char residue compared to the neat PAI. According to the tensile test results, with 5 mass% DLDH loading in the PAI matrix, the tensile strength increased from 51.6 to 70.8 MPa along with an increase in Young's modulus. Also the Young's modulus of PAI nanocomposite containing 5 mass% ALDH reduced from 1.95 to 0.81 GPa.     

Effects of Modified MMT on Mechanical Properties of EVA/MMT Nanocomposites and Their Foams

In this study, nanocomposites of poly(ethylene-co-vinyl acetate) with two kinds of organically modified montmorillonite (OMMT) were prepared by melt intercalation. Their structures and mechanical properties were characterized by X-ray diffraction (XRD) and tensile test respectively. Especially, foaming of these nanocomposites mixed with chemical blowing agent was carried out through compression molding. Influences of OMMT on foaming ratio and mechanical properties were investigated by density test, tensile test and tear test. Results revealed that both kinds of OMMT with proper content increased tensile strength and Young's modulus of nanocomposites without a compromise of elongation at break. For foaming, OMMTs apparently improved foaming ratio and in particular, one of them can improve tear strength, tensile strength, Young's modulus and elongation although the density was decreased.     

The Effect of 3-aminopropyltrimethyoxysilane (AMEO) as a Coupling Agent on Curing and Mechanical Properties of Natural Rubber/Palm Kernel Shell Powder Composites

This research is conducted using palm kernel shell powder (PKS) as filler in natural rubber The effect of 3-aminopropyltrimethoxysilane as coupling agent on composites were studied at different palm kernel shell loading i.e, 0 5, 10, 15 and 20 phr The palm kernel shell was crushed and sieved to an average particle size of 5.53 μm The palm kernel shell filled natural rubber composites were prepared using laboratory size two roll mill The curing characteristics such as scorch time, cure time and maximum torque were obtained from rheometer The palm kernel shell powder filled natural rubber composites were cured at 150^oC using hot press according to their cure time Curing characteristics, tensile properties, rubber-filler interaction and morphological properties of palm kernel shell powder filled natural rubber were studied Scorch time and cure time show reduction but tensile strength, elongation at break, modulus at 100% (M100) and modulus at 300% (M300) increased with the presence of 3-aminopropyltrimethyloxysilane Rubber-filler interaction studies showed that rubber filler interaction in natural rubber filled with palm kernel shell powder improved with incorporation of 3-aminopropyltrimethyoxysilane.     

Mechanical properties of polymers containing fillers

The addition of fillers can significantly change the mechanical characteristics of a material. In this paper, a general, mechanistic model is established to determine the moduli, relaxation moduli, break strengths, and break strains for polymer films containing liquid and solid micro fillers. Based on rigorous continuum mechanics principles, this model considers the filler/filler interactions, incorporates the nonlinear synergistic effects of fillers, and provides accurate predictions in comparison with experimental data. The analytical model developed provides information that is not available or extremely difficult to obtain experimentally. The model can be applied to determine the filler/matrix adhesion and filler modulus using measured modulus of a filled polymer film (a filled polymer is a polymer containing fillers). It is found that the compression moduli of polymer films containing liquid fillers differ significantly from the tension moduli, especially when the volume fraction of the filler is high. The difference in compression and tension Young's moduli normalized by the tension Young's modulus is as high as 35%. The relative error in maximum pressure calculation during Hertzian contact caused by using the tension moduli is as high as 48%. The relaxation modulus of a filled polymer film is determined through inverse Laplace transforms of its composite modulus in the s‐space. For a filled polymer film containing liquid phase fillers, a closed form solution for its relaxation modulus has been obtained. It is found that the composite relaxation modulus of the filled polymer is proportional to the relaxation modulus of the matrix polymer multiplied by a factor related to the volume fraction of the liquid filler. The break strength of the filled polymer is found to be proportional to the break strength of the polymer matrix material multiplied by a power function of the modulus ratio of filled polymer to polymer matrix, R. The break strain of the filled polymer is proportional to the break strain of the polymer matrix multiplied by a power function of 1/R. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 155–172, 1999     

Click coupled graphene for fabrication of high‐performance polymer nanocomposites

An effective technique of using click coupled graphene to obtain high‐performance polymer nanocomposites is presented. Poly(ε‐caprolactone) (PCL)‐click coupled graphene sheet (GS) reinforcing fillers are synthesized by the covalent functionalization of graphene oxide with PCL, and subsequently the PCL‐GS as a reinforcing filler was incorporated into a shape memory polyurethane matrix by solution casting. The PCL‐click coupled GS has shown excellent interaction with the polyurethane matrix, and as a consequence, the mechanical properties, thermal stability, thermal conductivity, and thermo‐responsive shape memory properties of the resulting nanocomposite films could be enhanced remarkably. In particular, for polyurethane nanocomposites incorporated with 2% PCL‐GS, the breaking stress, Young's modulus, elongation‐at‐break, and thermal stability have been improved by 109%, 158%, 28%, and 71 °C, respectively. This click coupling protocol offers the possibility to fully combine the extraordinary performance of GSs with the properties of polyurethane. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Mechanical,thermal and morphological properties of poly(ε‐caprolactone)/zein blends

Blends of poly(ε‐caprolactone) (PCL) with zein (PCL/zein) in different proportions (100/0, 75/25, 50/50, 25/75 and 0/100 wt% containing 5 wt% glycerol) were compared based on their mechanical properties (tensile strength, elongation at break, and Young's modulus), and on their thermal properties, the latter determined by thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA). The morphology of the materials was studied by scanning electron microscopy (SEM). Blends of PCL/zein showed reduced tensile strength and elongation at break, but increased Young's modulus compared to the pure polymers, in agreement with the DMTA and SEM results. These findings indicated that PCL and zein were incompatible. TGA showed that the thermal stability was enhanced by the addition of zein to PCL, whereas SEM showed a poor interfacial interaction between the polymers. Copyright © 2004 John Wiley & Sons, Ltd.     

包覆重钙粉为填充剂的橡胶加工及性能

重钙粉作为填充剂被广泛应用于橡胶加工过程,但由于其表面具有极性,分散性较差,导致与橡胶材料界面结合较差,影响了橡胶产品的抗拉强度、断裂伸长率等力学性能。 本文采用沉淀法,在CaCl₂-H₂O-NH₃-CO₂体系中生成碳酸钙直接结晶于重钙粉颗粒表面,实现对重钙粉的表面包覆,将n(CaCl₂)：n(重钙粉)=1：100、5：100、10：100的包覆重钙粉填充到天然橡胶和再生胶中,橡胶的力学性能与填充未包覆重钙粉的橡胶相比有了一定的提升。 通过比较,在填充量较大(8.5%、15%)时,包覆重钙粉橡胶产品在硬度、定伸应力等力学性能上要好于轻钙粉橡胶产品;在填充量(5%、8.5%)时,包覆重钙粉橡胶产品的抗拉强度、断裂伸长率接近于白炭黑,硬度高于白炭黑橡胶产品。     

Mechanical properties of crosslinked polyolefin-based materials

The effect of crosslinking on mechanical properties of various polyethylene-based materials is compared. In virgin polyethylene, higher strength results from formation of spatial network, especially at increased temperatures. On the other hand, decreased crystalline portion leads to lower Young's modulus values compared with the uncrosslinked polymer. Crosslinking of LDPE/PP blends leads to a dramatic increase in elongation at break and impact resistance. The reason is seen in an in situ formation of very efficient compatibilizers via co-crosslinking on the phase boundary. In LDPE filled with silica, the main effect consists in higher elongation at break and increased toughness, although the effect is lower than that in LDPE/PP blends. Increased resistance to the crack growth rate was demonstrated to be a reason for the observed behaviour. In LDPE filled with organic fillers, formation of direct covalent bonds on the interface and a significant increase in adhesion is suggested to be the reason for the enormous increase in Young's modulus and tensile strength observed.     

Preparation and characterization of polyimide/pure silica zeolite hybrid films

In this study, amino derivative of pure silica zeolite nanocrystal (A‐PSZN) was dispersed into polyimide (PI) matrix to prepare PI/A‐PSZN hybrid films, and their thermal and mechanical properties, as well as hydrophobicity, were characterized scientifically. The test results show that PI/A‐PSZN hybrid films possess higher glass transition temperature, higher thermal stability and lower in‐plane coefficient of thermal expansion than pristine PI. The mechanical property data suggest that the incorporation of A‐PSZN results in an increase in Young's modulus and tensile strength of the hybrid films, but as its content exceeds the critical value (maybe 5 wt%), its enhancement effect on the hybrid's strength and toughness gets weaker. Furthermore, liquid dripping imaging analysis results indicate that the film's hydrophobicity is clearly improved by the introduction of A‐PSZN. As compared with PSZN, A‐PSZN exhibits better effect on enhancing the overall performance of pristine PI films. A comparison with other studies suggests that PI/A‐PSZN is a hybrid film with superior comprehensive properties. Copyright © 2013 John Wiley & Sons, Ltd.     

Batch and semicontinuous emulsion copolymerization of vinyl acetate–butyl acrylate. II. Morphological and mechanical properties of copolymer latex films

Vinyl acetate/(VAc)-butyl acrylate/(BuA) copolymer latex films of various copolymer compositions were investigated for their morphological properties by electron microscopy techniques, and for their mechanical properties by dynamic mechanical spectroscopy (DMS), differential scanning calorimetry (DSC), and tensile strength measurements. Batch copolymer latex films showed domains of PBuA dispersed in PVAc matrix; the domain sizes were increased with increased BuA content. Semicontinuous latex films were homogeneous in composition. Glass transition temperatures T_g determined from DMS and DSC indicated the presence of two, low and high, transition temperatures for batch latex films. The two temperatures approached the individual homopolymers, with increased PBuA content up to 51 mol %. Semicontinuous latex films showed only one single T_g. Tensile properties of the batch copolymer films showed a higher ultimate tensile strength, higher Young's modulus, and lower percent elongation to break compared to semicontinuous latex films. These differences were found to reflect the effect of mode of monomer addition during the emulsion copolymerization process on the particle morphology, and confirmed earlier data on bulk, colloidal, and surface properties of the same copolymer latexes.