Effect of nanoclays on physico-mechanical properties and adhesion of polyester-based polyurethane nanocomposites: structure–property correlations

Polyester–polyurethane nanocomposites based on unmodified and modified montmorillonite clays were compared in terms of their morphology, mechanical, thermal, and adhesive properties. Excellent dispersion of the modified nanoclay in polymer with 3 wt% loading was confirmed from X-ray diffraction, and low-, and high-magnification transmission electron micrographs. The properties of the clay-reinforced polyurethane nanocomposites were a function of nature and the content of clay in the matrix. The nanocomposite containing 3 wt% modified clay exhibits excellent improvement in tensile strength (by ~100%), thermal stability (20 °C higher), storage modulus at 25 °C (by ~135%), and adhesive properties (by ~300%) over the pristine polyurethane.     

一种基于有序硬段的可生物降解聚氨酯的制备及性能

以聚乙二醇(PEG,Mn=600、1000)为引发剂,L-丙交酯(L-LA)为单体,在辛酸亚锡存在下开环聚合合成了三嵌段预聚物聚丙交酯-聚乙二醇-聚丙交酯(PLA-PEG-PLA),然后以具有有序结构的二氨基甲酸酯基二异氰酸酯(六亚甲基二异氰酸酯-1,4-丁二醇-六亚甲基二异氰酸酯,HBH)扩链制备了一种可生物降解的脂肪族聚氨酯(PU-I、PU-II)。作为对比,以4,4’-二苯基甲烷二异氰酸酯(MDI)作为扩链剂合成了芳香族聚氨酯(PU-III)。通过核磁共振、红外光谱、超高分辨质谱、凝胶渗透色谱等对预聚物、扩链剂、聚氨酯的化学结构进行了表征。通过对PU-I、PU-II和PU-III膜热性能、力学性能和体外降解性能的对比,研究了有序硬段对聚氨酯性能的影响。结果表明,相对于PU-III,PU-I具有更好的力学性能(断裂强度21 MPa,断裂伸长率840%)和较快的体外降解(19d);随着亲水链段PEG含量的增加,PU膜(PUII)的断裂强度降低,断裂伸长率增加,同时体外降解速率变快。该类型的脂肪族聚氨酯具有降解产物无毒、合适的力学性能和降解性能,可替代传统的芳香族聚氨酯,在医疗行业中有更广泛的用途。     

Preparation and dielectric properties of poly(arylene ether nitrile) containing carboxyl groups/carbon nanotubes composites

Poly(arylene ether nitrile) (PEN)/carbon nanotubes (CNTs) hybrid films were prepared with different CNTs content (0–2.5 wt%) by solution blending method. The dispersion of CNTs can be improved by the functional groups, which is attributed to the pendent carboxyl groups on the PEN matrix itself. Namely, the carboxyl groups on the side-chain of PEN react with the hydroxyl groups of CNTs. Scanning electron microscope showed that the dispersion of the CNTs was enhanced by the carboxyl groups on the PEN. Differential scanning calorimetry and thermal gravimetric analyses experiments showed that the hybrid films exhibit a good thermal stability. The dielectric constant of the hybrid film with 2.5 wt% CNT content reaches 27 compared to 4 at pure PEN at 1 kHz. From room temperature to 150 °C, temperature variation over the range has a slight effect on the dielectric properties of the hybrid films. The dielectric constant of the hybrid film with 2.5 wt% CNT content reaches 30 compared to 5 at pure PEN at 150 °C. The results illustrate that the PEN/CNTs hybrid films are good dielectric materials, which is favorable for many industrial applications.     

Fluorinated graphene reinforced polyimide films with the improved thermal and mechanical properties

In order to explore the addition effect of fluorinated graphene (FG) on the mechanical and thermal performances of polyimide (PI) matrix, FG sheets are first prepared and employed as the nanofillers to construct PI/FG nanocomposite films. The prepared film is optically transparent at low content of FG and experimental results demonstrate that the addition of FG can effectively enhance the properties of PI matrix. Especially, compared with pure PI matrix, the addition of 0.5 wt% FG in PI can endow 30.4% increase in tensile stress and 115.2% increase in elongation at break. Experimental analyses considering the morphology and microstructure are also conducted, and the results indicate that the improved mechanical properties of the PI/FG nanocomposite films are mainly attributed to the good dispersibility of FG sheets in PI host, and the effective stress transfer between the polymer and the FG.     

Properties of polymer networks prepared by blending polyester urethane acrylate with acrylated epoxidized soybean oil

Polyurethane network films were prepared using polyester urethane acrylate (PUA) having terminal double-bond functional groups and acrylated epoxidized soybean oil (AESO). PUA elastomers were prepared by reacting polyester diol with diisocyanates, hexamethylene diamine, and acrylic acid. PUA/AESO network blends are synthesized by a simultaneous thermal polymerization process. The physical and thermal properties of the polymer networks obtained from the blend of AESO and polyester urethane urea acrylate were studied using FTIR-ATR, the thermal degradation behavior was studied by thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, and tensile properties measurements being applied. The measurements were compared to the results for elastomers made from the PUA. The weight ratios of PUA/AESO affected the thermal and mechanical properties. With an increase in AESO content, the glass-transition temperature of the networks decreased from 40 to −4.8 °C, tensile strength increased from 1.7 to 9.8 MPa, and elongation at break decreased from 470 to 70%.     

Synthesis and characterization of photoactive polyurethane elastomers with 2,3-dihydroxypyridine in the main chain

Photoactive polyurethane elastomers with pyridine derivatives in the polymer backbone were synthesized by chain-extending isocyanate end-capped prepolymers with 2,3-dihydroxypyridine. The isocyanate-terminated prepolymers were obtained from poly(tetramethylene oxide) glycol of molecular weight 1400 (Terathane 1400) and 1,6-hexamethylene diisocyanate. The properties of the linear heterocyclic polyurethane were compared with properties of the crosslinked heterocyclic polyurethane obtained by chain extension with various crosslinkers. Heterocyclic polyurethane elastomers were characterized using Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), dynamic mechanical analysis (DMA), contact angle measurements, and mechanical analysis. Static mechanical measurements showed greater elongation and tensile strength for polyurethanes with a lower content of heterocyclic groups in the hard segment. The static contact angles of the cast films of these polymers indicated that the nature of the hard segment influences the surface polarity. The dynamic mechanical spectra revealed that linear polymers have two transition temperatures as results from a clear phase separation caused by high-intermolecular hydrogen bonds in the regions of pyridine units and urethane groups. Polyurethane elastomer films with pyridine moieties in the main chain form a photosensitive material. If stored in laboratory conditions (light, ambient air atmosphere), the color of the films changes from white to black. These photo-induced structural changes are studied by H NMR measurements.     

Effect of surface functionalization on mechanical properties and decomposition kinetics of high performance polyetherimide/MWCNT nano composites

In this investigation, Polyetherimide (PEI) reinforced with multi-walled carbon nanotube (MWCNT) using novel melt blending technique. Surface of MWCNTs are modified by acid treatment as well as by plasma treatment. PEI nano composites with 2 wt% treated MWCNT shows about 15% improvement in mechanical properties when compared to unfilled PEI. The thermal decomposition kinetics of PEI/MWCNT nano composites has been critically analyzed by using Coats – Redfern model. The increase in activation energy for thermal degradation by 699 kJ/mol for 2 wt% MWCNT implies improvement in the thermal properties of PEI. Studies under Fourier Transform Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM) depict significant interfacial adhesion with uniform dispersion of MWCNT in polymer matrix due to surface functionalization. 0.5 wt% chemically modified MWCNT shows typical alignment of MWCNT. There is a significant improvement in mechanical properties and thermal properties for surface functionalized MWCNT reinforced.     

Statistical evaluation of influence of xanthan gum and guar gum blends on dipyridamole release from floating matrix tablets

The present investigation explored the use of xanthan gum and guar gum for development of floating drug delivery system of dipyridamole using factorial design approach. The content of polymer blends (X(1)) and ratio of xanthan gum to guar gum (X(2)) were selected as independent variables. The diffusion exponent (n), release rate constant (k), percentage drug release at 1 hr (Q(1)) and 6 hr (Q(6)) were selected as dependent variables. Tablets of all batches had desired buoyancy characteristics. Multiple regression analysis with two way ANOVA revealed that both the factors had statistically significant influence on the response studied (p<0.05). Results of Tukey test showed the relative contribution of each level of different factors for the response studied. It was concluded that the ratio of xanthan to gaur gum had equal or dominant role as controlling factor on kinetics of drug release compared to content of polymer blends.     

Structure and properties of melt-processed PVDF/PMMA/polyaniline blends

Ternary blends composed of the matrix polymer poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) with different proportions of thermally doped polyaniline (PAni) using an alkylated dopant (dodecylbenzenesulfonic acid) (DBSA) were prepared by melt mixing. The effectiveness of these blends was compared with the corresponding binary blends of PVDF or PMMA with PAni–DBSA complex. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) measurements, thermal analysis by differential scanning calorimetry (DSC) and morphological studies by optical microscopy and scanning electron microscopy (SEM) were carried out to characterize the blends in light of the interactions between their components and on the resulting electrical conductivity. Though a notable dispersion of PAni–DBSA in the PMMA matrix was incurred along with better conductivity with respect to PVDF/PAni–DBSA and PVDF/PMMA/PAni–DBSA blends, the thin films based on PMMA/PAni–DBSA were found to be fragile in nature. However, the presence of PMMA in the ternary blends of PVDF/PMMA/PAni–DBSA provided improved dispersion of PAni–DBSA in the PVDF/PMMA host matrix as compared to PVDF/PAni–DBSA binary blends. An enhancement in the conductivity by about two orders of magnitude at >5 wt% PAni–DBSA was witnessed in the ternary blends than that of PVDF/PAni–DBSA binary blends. Thin films made of ternary blends of PVDF/PMMA/PAni–DBSA also offered superior mechanical properties and flexibility than that of PMMA/PAni–DBSA binary blends due to the contribution of PVDF in the blend.     

The surface characteristics of organoclays and their effect on the properties of poly(trimethylene terephthalate) nanocomposites

Biobased materials developed in conjunction with nanotechnology are poised to achieve a significant presence in the world market for polymeric materials. An example of an engineering polymer that can be partially derived from biomass is poly(trimethylene terephthalate). One of its raw materials, 1,3-propanediol, can be derived from corn sugar. In the present study we used a fully petroleum-based resin as an analog to the biobased material. Five organically modified montmorillonite clays were characterized via moisture uptake studies to determine the hydrophilic/hydrophobic nature of their surfaces. Nanocomposites were produced via melt compounding followed by injection molding with 5 wt.% organoclay loading to determine which modification gave the best balance of mechanical and thermal properties. It was found that the tensile modulus increased by up to 35% and the tensile stress at break by up to 50%. The heat deflection temperature of the nanocomposites versus the neat polymer increased by up to 33 °C. From these results, one organoclay was selected for detailed study over a loading range of 0–5 wt.%. The testing revealed that over this range, changes in the mechanical properties may go through a maximum (e.g. strength) or increase/decrease to a plateau (e.g. modulus, elongation at break). X-ray diffraction and transmission electron microscopy were also used to characterize the nature of the organoclay/polymer interaction. Biobased poly(trimethylene terephthalate)/organoclay nanocomposites are expected to exhibit properties similar to the petroleum-based resin.     

阳离子水性聚氨酯乳液的合成及性能

以二异氰酸酯和聚酯二元醇合成聚氨酯预聚体,采用N-甲基二乙醇胺(N-MDEA)为亲水扩链剂,制备了阳离子水性聚氨酯(CWPU)乳液,研究了制备CWPU乳液的影响因素,并研究了CWPU乳液涂膜的拉伸性能。研究表明,当N-MDEA的质量分数为7.0%-9.5%,R值为1.3-1.5,中和度为80%-100%时,可制得稳定性较好的CWPU乳液。随着N-MDEA含量增加,CWPU乳液涂膜拉伸强度增加,断裂伸长率下降;随着中和度的提高,涂膜拉伸强度和断裂伸长率同时提高。     

Fluorographene/polyimide composite films: Mechanical,electrical, hydrophobic,thermal and low dielectric properties

Nowadays, dielectric materials with excellent mechanical and hydrophobic properties are desired for use in the integrated circuits (ICs). For this reason, low dielectric constant fluorographene/polyimide (FG/PI) composite films were prepared by a facile solution blending method, suggesting that the mechanical, electrical, hydrophobic and thermal properties were significantly enhanced in the presence of FG. With addition of 1 wt% FG, the tensile strength, Young’s modulus and elongation at break were dramatically increased by 139%, 33% and 18% respectively when compared with pure PI film. Furthermore, composite films exhibit superior hydrophobic and thermal stability performance. Especially, the FG/PI film with 0.5 wt% of FG possessing a low dielectric constant of 2.48 and a good electrical insulativity that is lower than 10⁻¹⁴ S m⁻¹. Therefore, by their excellent performance, FG/PI hybrid films represent suitable candidate solutions with applications in the microelectronics and aerospace industries.     

Toughening of brittle poly(lactide) with hyperbranched poly(ester-amide) and isocyanate-terminated prepolymer of polybutadiene

Abstract  

The use of polylactide (PLA) in durable applications is currently being hampered by its brittleness and low impact strength. In this study, the effects on mechanical properties of two potential toughening agents for PLA, i.e., hydroxyl-terminated hyperbranched poly (ester amide) and isocyanate-terminated prepolymer of butadiene (ITPB), alone and in combination, are investigated with the aim of making tough PLA blends for use in durable non-food applications such as automotive interior. Synergistic effects in impact strength were observed in PLA ternary blends containing hyperbranched polymer (HBP) and ITPB. Impact strength of the PLA/HBP/ITPB ternary blend was improved by over 86 %, while the elongation at break was increased by over 100 %. Physical and chemical interactions between the hydroxyl-terminated HBP and the ITPB may be responsible for the observed synergistic effect and improvements in impact strength. Tensile, flexural, thermal, and thermo-mechanical properties of the PLA/HBP blends with varying amounts of the ITPB were studied. Scanning electron microscopy images showed evidence of stretched polymer which may indicate that the fracture behavior of PLA changed from brittle to ductile in the PLA/HBP/ITPB ternary blends.     

Mechanical properties and fracture morphologies of poly(phenylene sulfide)/nylon66 blends—effect of nylon66 content and testing temperature

Poly(phenylene sulfide) (PPS) was melt blended with Nylon66 and the mechanical properties and corresponding fracture morphologies were investigated. The thermal distortion temperature (HDT) of PPS/Nylon 66 blend showed that the inherent thermal stability of pure PPS can be maintained up to 30 wt% Nylon66, but then it started to decrease linearly thereafter to that of pure Nylon66 based on the rule of mixtures relationship. Tensile tests of PPS/Nylon66 blends at testing temperatures of –30, 25, 75, and 150°C showed that the maximum stress decreased up to 30 wt% Nylon66, and started to increase thereafter. Strain at break showed little change at low nylon content regardless of testing temperature, however, a large strain at break increase could be observed at more than 30 wt% Nylon66 and at 150°C testing temperature. At the same testing temperatures, the impact strength of PPS/Nylon66 blends was investigated, and it was found that an impact strength increase at all testing temperatures could be observed at more than 30 wt% Nylon66.     

Plasticized polylactic acid nanocomposite films with cellulose and chitin nanocrystals prepared using extrusion and compression molding with two cooling rates: Effects on mechanical,thermal and optical properties

Triacetate citrate plasticized poly lactic acid and its nanocomposites based on cellulose nanocrystals (CNC) and chitin nanocrystals (ChNC) were prepared using a twin-screw extruder. The materials were compression molded to films using two different cooling rates. The cooling rates and the addition of nanocrystals (1 wt%) had an impact on the crystallinity as well as the optical, thermal and mechanical properties of the films. The fast cooling resulted in more amorphous materials, increased transparency and elongation to break, (approx. 300%) when compared with slow cooling. Chitin nanocomposites were more transparent than cellulose nanocomposites; however, microscopy study showed presence of agglomerations in both materials. The mechanical properties of the plasticized PLA were improved with the addition of a small amount of nanocrystals resulting in PLA nanocomposites, which will be further evaluated for film blowing and thus packaging applications.     

Preparation and dielectric properties of fullerene-doped polyarylene ether nitrile film

In order to obtain polymer films with low dielectric constant (≤2.0) and enhanced mechanical strength, fullerene-doped polyarylene ether nitrile (PEN) film was designed and prepared according to the following step. At first, fullerene and PEN were dissolved in toluene and N-methyl pyrrolidone, respectively, and the solutions were mixed together. The films were prepared by solution casting/solvent evaporation method on glass sheet. The morphology and thermal analysis of the films were characterized by visual & SEM observation and DSC & TGA test, respectively. The mechanical properties and dielectric properties of the films were also measured. The results showed that the dispersion of fullerene was largely dependent on the evaporation methods of the solvents. The glass transition temperature (Tg) and thermal decomposition temperature (Td) of PEN films were improved with the addition of fullerene. The dielectric constant sharply decreased from 4.0 to about 2.0 with the addition of fullerene. At the same time, the mechanical properties were improved, which might be caused by the physical entanglement of PEN chains with fullerenes. The lowest ε value (1.75 at 1 MHz) and the highest tensile strength (142.2 Mpa) were simultaneously obtained in samples containing 3 wt% fullerenes, which indicated it’s the optimal content of fullerene.     

Preparation and characterization of iron phthalocyanine polymer magnetic materials

A novel kind of polymer magnetic material iron phthalocyanine (FePc) was prepared via the polymerization of phthalonitrile with iron pentacarbonyl. The pre-polymerization was monitored by FTIR and UV–Vis spectra. Microwave dielectric properties of prepolymers were dependent on their chemical structures. The thermal properties of FePc polymer were evaluated by TGA, the initial decomposition temperature of completely cured polymer was about 420 °C and char yield at 800 °C was 63.56%. Controlling the pre-polymerization degree of phthalonitrile by the reaction time, the magnetic properties of cured polymer materials can be finely tuned. The saturation magnetization of cured polymer decreased from 2.48 to 0.42 emu/g, whereas the coercive force increased from 123.8 to 228.6 Oe. The microstructure of iron phthalocyanine polymer was characterized by scanning electron microscope and the typical layer structure morphology of phthalocyanine polymer was clearly observed.     

Effect of polymer molecular weight and of polymer blends on the properties of rapidly gelling nasal inserts

The objective was to investigate the potential of polymer molecular weight (MW) and polymer blends for the control of drug release from in situ gelling nasal inserts prepared by lyophilization of solutions of model drugs (oxymetazoline HCl, diprophyllin) and polymers. Drug release, polymer solution viscosity, water uptake and mass loss, mechanical properties, and bioadhesion potential were measured. Sonication was effective to reduce the viscosity/polymer MW of carrageenan solutions. Nasal inserts prepared from sonicated carrageenan showed an insignificant reduction in water uptake with sonication time and no disintegration of the gel matrix. In contrast, inserts of different MW Na-alginates revealed a reduced water uptake and an increased mass loss with lower MW. Inserts prepared from carrageenan/low MW Na-alginate blends took up more water at a higher low MW Na-alginate content. Sonicated carrageenan inserts released oxymetazoline HCl independent of the sonication time and diprophyllin with only a slight reduction in the release rate. Release of both drugs from Na-alginate inserts was slow from high MW inserts because no insert dissolution occurred. Increasing the Na-alginate content of inserts prepared from polymer blends accelerated the drug release enabling release rates over a broad range. The bioadhesion potential of Na-alginate inserts was strongly reduced for the low MW grades because of dissolution of the inserts. Xanthan gum and Carbopol 971 blended with Na-alginate formed inserts with poor bioadhesion. The use of polymer blends to control the drug release from nasal inserts was superior to the use of polymers of different MW.     

Improvement of ternary recycled polymer blend reinforced with date palm fibre

This paper investigates the study and preparation of date palm fibre reinforced recycled polymer blend composites. This is the first paper which describes the recycled polymer ternary blends of (1) recycled low density polyethylene (RLDPE), (2) recycled high density polyethylene (RHDPE) and (3) recycled polypropylene (RPP). The date palm fibre reinforced composites (C_D00) were prepared by maintaining constant weight% of fibre of 20 wt% without any fibre treatment. Maleic anhydride (MA) was used as the compatabilizer (1 and 2 wt%) and the effect of compatabilizer on the blend matrix composites was studied. The mechanical, thermal, morphological properties, water absorption and chemical resistance properties were evaluated for these composites and also studied for pure blend matrix (C₀₀). Date palm fibre improved the tensile strength and hardness of recycled polymer blend matrix. Further improvement was achieved with 1% MA (C_D1), which showed that 1% MA treated composites (C_D1) had higher tensile strength, modulus and hardness properties. Thermal stability and water absorption were improved by 1% MA. These improvements were demonstrated at the nanoscale level by the decrease in roughness appearing in Atomic Force Spectroscopic Microscopy analysis indicating that flow is better under this concentration. The SEM analysis also showed that the fibre matrix adhesion improved by adding 1 wt% (C_D1) of MA. The melting and crystallisation temperatures of the blends did not change with the addition of date palm fibre and MA, indicating that the additives did not influence the melting and crystallisation properties of the composites. The chemical resistance test results showed that these composites are resistance to all chemicals but more weight gain observed in solvents. 2 wt% of MA (C_D2) caused poor adhesion between the polymer chains and fibres as well as polymer chain scission.     

Effect of the long chain extender on the properties of linear and castor oil cross-linked PEG-based polyurethane elastomers

Polyurethane (PU) elastomers were elaborated from polyethylene glycol of high molecular weight (MW = 4,000), 1,6-hexamethylene diisocyanate and polyethylene glycol (PEG₁₅₀₀) (MW = 1,500) as a long linear chain extender and/or castor oil as a cross-linker and were obtained in the form of transparent films. These poly(ether urethanes) elastomers are obtained by replacing the short-chain diol monomers with high molecular weight polyethylene glycols (PEG₁₅₀₀). High molecular weight polyethylene glycol (MW = 4,000 and 1,500, respectively) have greater chain length thus producing networks with lower cross-linking densities and higher average molecular weight between two consecutive cross-links. The PU properties were investigated using Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry, mechanical analysis and thermogravimetry. The results showed that the prepared polyurethanes (PUs) had very good tensile properties. The stress–strain data show that the PU elastomers obtained using a 60/40% OH_PEG1500/OH_{castor oil} ratio have the best mechanical properties. The thermal degradation of the castor oil cross-linked PU elastomers starts at 280–300 °C, compared to the thermal degradation of linear PUs which begins at 220 °C. During storage at 25 °C, the morphology and mechanical properties of the elastomer films have been observed to change in time.