Poly(vinylidene fluoride)/thermoplastic polyurethane flexible and 3D printable conductive composites

This work focus on the development of polymeric blends to produce multifunctional materials for 3D printing with enhanced electrical and mechanical properties. In this context, flexible and highly conductive materials comprising poly(vinylidene fluoride)/thermoplastic polyurethane (PVDF/TPU) filled with carbon black-polypyrrole (CB-PPy) were prepared by compression molding, filament extrusion and fused filament fabrication. In order to achieve an optimal compromise between electrical conductivity, mechanical properties and printability, blends composition was optimized and different CB-PPy content were added. Overall, the electrical conductivities of PVDF/TPU 50/50 vol% co-continuous blend were higher than those found for PVDF/TPU 50/50 wt% (i.e., 38/62 vol%) composites at same filler content. PVDF/TPU/CB-PPy 3D printed samples with 6.77 vol% filler fraction presented electrical conductivity of 4.14 S m⁻¹ and elastic modulus, elongation at break and maximum tensile stress of 0.43 GPa, 10.3% and 10.0 MPa, respectively. These results highlight that PVDF/TPU/CB-PPy composites are promising materials for technological applications.     

Reduced graphene oxide (RGO)-induced compatibilization and reinforcement of poly(vinylidene fluoride) (PVDF)–thermoplastic polyurethane (TPU) binary polymer blend

Compatible blends of nonreactive thermoplastic fluoropolymer, poly(vinylidene fluoride) (PVDF) and thermoplastic polyurethane (TPU) at 70/30 weight ratio, were prepared by utilizing the unique structural feature of reduced graphene oxide (RGO). Here, RGO acts as a compatibilizer as well as a reinforcing filler. RGO interacts with both polymers and reduces the interfacial tension between them, leading to compatibilization. RGO content in the blends was varied from 0 to 0.5 wt %, and the best result was found at 0.3 wt % loading. Excellent compatibilization between PVDF and TPU was established by mechanical, morphological, and thermal property studies. Chemical interaction between the RGO/TPU and RGO/PVDF was proved by FTIR–ATR study. With the incorporation of 0.3 wt % RGO, tensile strength, Izod impact strength, and elongation at break of the blend were increased by 42%, 83%, and 43%, respectively. FESEM and AFM images of blends without loading of filler after etching out of TPU phase show nonuniformly distributed hole morphology. RGO-containing blend has shown much finer and uniformly distributed holes that confirm improved compatibility between the two incompatible polymers. RGO also improves the thermal stability of the compatible blends considerably. At 0.3 wt % loading, the onset of thermal degradation increased by about 10 °C. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47010.     

Hot melt adhesive properties of PA/TPU blends compatibilized by EVA-g-MAH

A new copolyamide (PA52) with good adhesion to aluminum (Al) sheets was synthesized from caprolactam, nylon 66 salt, nylon 1010 salt, and stearic acid, and a series of PA52/TPU blends compatibilized by maleic anhydride-grafted ethylene vinyl acetate (EVA-g-MAH) were prepared for use as hot melt adhesives. In the ternary blends (PA52/EVA-g-MAH/TPU), the weight ratio of PA52 to TPU was kept constant at 50/50 and the amount of EVA-g-MAH was varied at 0, 2, 4, 6, and 8 wt% over the total weight of the blend, respectively. The solubility parameters were taken into account to describe the partial compatibility of PA52/TPU blends. The effects of EVA-g-MAH content on the melt viscosity, morphology, mechanical and thermal properties of ternary blends were systematically investigated, and the adhesion strength of hot melt adhesives based on the ternary blends were determined in terms of 90° peeling strength tests of Al/adhesive/ABS stacks. The results showed that the melt viscosity of ternary blends were greater than that of PA52/TPU blend, and the blend containing 6 wt% EVA-g-MAH exhibited an optimal miscibility behavior and excellent mechanical properties, at the same time, its peeling strength reached the maximum (120 N/25 mm).     

Properties and preparation of olefin block copolymer/thermoplastic polyurethane blends

The properties of olefin block copolymer (OBC)/thermoplastic polyurethane (TPU) blends with or without maleic anhydride (MA) modification were characterized and compared. Compared with the OBC/TPU blends, OBC‐g‐MA/TPU blends displayed finer morphology and reduced domain size in the dispersed phase. The crystallization temperatures of TPU decreased significantly from 155.9 °C (OBC/TPU) to 117.5 °C (OBC‐g‐MA/TPU) at low TPU composition in the blends, indicating the inhibition of crystallization through the sufficient interaction of modified OBC with TPU composition. The modified systems showed higher thermal stability than the unmodified systems over the investigated temperature range due to the enhanced interaction through inter‐bonding. The highest improvement in tensile strength was more than fivefold for OBC‐g‐MA/TPU (50/50) in comparison with its unmodified blend via the enhanced interfacial interaction between OBC‐g‐MA and TPU. This also led to the highest Young's modulus of 77.8 ± 3.9 MPa, about twofold increase, among the investigated blend systems. A corresponding improvement on the ductility was also observed for modified blends. The modification did not vary the glass transition temperature and crystalline structure much, thus the improvement in the mechanical properties was mainly attributed to the improved compatibility and interaction from the compatibilization effect as well as increased viscosity from the crosslinking effect for modified blends. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43703.     

TPU增韧改性PBT的研究

分别采用醚型和酯型热塑性聚氨酯(TPU)对聚对苯二甲酸丁二醇酯(PBT)进行增韧改性，并对共混物的性能、形态结构及流变性能进行了研究。结果表明：醚型TPU对PBT有较好的增韧效果，共混物有明显的两相，PBT为连续相，TPU为分散相，当m(PBT)／m(TPU)=100／75时，拉伸屈服强度可达41．7MPa，缺口冲击强度326 J／m，是纯PBT的两倍，断裂伸长率330％；醚型TPU对PBT共混物的表观粘度有较大的影响，当m(PBT)／m(TPU)=100／50时．共混物表观粘度只有纯PBT的20％。     

PVC/TPU/NBR三元共混物的制备及性能研究

对PVC／热塑性聚氨酯（TPU）／SR三元共混物的性能进行研究，重点讨论NBR品种、TPU／NBR并用比、PVC聚合度、增塑剂DOP和硫化剂DCP用量对PVC／TPU／NBR三元共混物性能的影响。结果表明。PVC／TPU／NBR-3604三元共混物的物理性能较优；PVC／TPU／NBR-3604三元共混物的拉断伸长率和拉断永久变形均随着PVC聚合度的增大基本呈上升趋势；随着增塑剂DOP用量的增大，共混物的邵尔A型硬度、拉伸强度、撕裂强度和拉断永久变形均基本呈下降趋势，拉断伸长率增大；随着硫化剂DCP用量的增大。共混物的拉伸强度和拉断伸长率变化不大，撕裂强度基本呈逐渐减小的趋势。不同PVC／TPU／SR三元共混物的扫描电子显微镜照片表明，NBR与PVC和TPU的相容性较好。     

Scrutinizing the influence of peroxide crosslinking of dynamically vulcanized EVA/TPU blends with special reference to cable sheathing applications

A novel thermoplastic vulcanizate (TPV) based on the blends of ethylene vinyl acetate/thermoplastic polyurethane (EVA/TPU) at various blend ratios has been developed via dynamic vulcanization at 180 °C using di‐(2‐tert‐butyl peroxy isopropyl) benzene (DTBPIB) peroxide as the cross‐linking agent. Modification of the EVA/TPU blends via dynamic crosslinking significantly improves the tensile strength and modulus of the system and the improvement is more significant for EVA/TPU 50/50 and 60/40 blends. AFM study shows that crosslinked EVA particles are dispersed in the continuous TPU matrix and the dispersed EVA domain sizes are relatively smaller in EVA/TPU 50/50 and 60/40 blends leading to good mechanical properties. FTIR spectroscopy has been used to characterize the specific chemical changes occurring due to dynamic vulcanization. This TPV has excellent retention of physico‐mechanical properties even after reprocessing twice and the blends also have very good thermal resistance as indicated by aging study. The samples were found to exhibit remarkable improvement in oil resistance property as compared to their uncrosslinked counterpart. The creep behavior of the blends significantly improves after dynamic crosslinking and blends with higher TPU content show better creep resistance. Volume resistivity of all the peroxide vulcanized blends is in the range of 10¹³ ohm cm, which is suitable for cable sheathing application. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43706.     

Influence of the morphology and viscoelasticity on the thermomechanical properties of poly(lactic acid)/thermoplastic polyurethane blends compatibilized with ethylene-ester copolymer

Viscoelastic, interfacial properties, and morphological data were employed to predict the thermal and mechanical properties of compatibilized poly(lactic acid) (PLA)/thermoplastic polyurethane (TPU) blends. The combination of interfacial thickness measured by contact angle and entanglement density determined by dynamical mechanical analysis analyze data was employed to evaluate the mechanical behavior of PLA/TPU blends with and without ethylene-butyl acrylate-glycidyl methacrylate (EBG) compatibilization agent. The PLA/TPU blend (70/30 wt %) was prepared in a Haake internal mixer at 190 °C and compatibilized with different contents of EBG. The evaluation of the interfacial properties revealed an increase in the interfacial layer thickness of the PLA/TPU blend with EBG. The scanning electronic microscopy images showed a drastic reduction in the size of the dispersed phase by increasing the compatibilizer agent EBG content in the blend. The compatibilization of the PLA/TPU blends improved both the Izod impact strength and yield stress by 38 and 33%, respectively, in comparison with neat PLA/TPU blend. The addition of EBG into PLA/TPU blends significantly increased the entanglement density and the PLA toughening but resulted in a decrease of PLA deformation at break. The PLA and TPU glass transitions were affected by the EBG, suggesting that the PLA and TPU domains were partially miscible. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48926.     

Study on thermoplastic polyurethane/polypropylene (TPU/PP) blend as a blood bag material

Blends with different ratios of thermoplastic polyurethane/polypropylene (TPU/PP) were prepared by melt mixing using an internal Haake mixer. Properties of the blends were investigated using SEM micrographs of cryofractures and measurement of the mechanical strength, water absorption, cell culture, and platelet adhesion in vitro tests, which were compared with those of PVC blood bags. The effect of the addition of the ethylene–vinyl acetate (EVA) copolymer on the TPU/PP blend properties was investigated. The results indicated that a TPU/PP/EVA = 80/20/5 blend can be used as a new blood bag material. It was observed that the blend is homogeneous with higher mechanical strength than that of the commercial PVC blood bag. This blend also showed a compatible cell response in contact with L929 fibroblast cells and fewer tendencies to interaction with platelets compared to the PVC blood bag. Although the blends were immissible and no chemical reaction at the interface could be found, the blood compatibility of the blends were improved. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2496–2501, 2003     

Morphology and properties of blends with different thermoplastic polyurethanes and polyolefines

Unmodified blends of two thermoplastic polyurethanes (TPU) and six polyolefines were used to study the influence of the component viscosities on the blend morphology and mechanical properties. Blends were produced by melt mixing using a twin screw extruder. Interactions between the blend components could not be detected by DSC, DMA, selective extraction, and SEM micrographs of cryofractures. The variation in tensile strength with blend composition produce a U-shaped curve with the minimum between 40 and 60 wt % of polyolefine. At similar viscosity ratios (η_d/η_m), blends with polyether based TPU (TPU-eth) have a finer morphology than blends with polyester based TPU (TPU-est). This is due to the lower surface free energy of the polyether soft segments compared to the polyester soft segments. Different morphologies also lead to changes in mechanical behavior. Blends with TPU-eth show a lower decrease in tensile strength with blend composition than blends with TPU-est. The viscosity ratio between TPU and polyolefines can be directly correlated to the blend morphology obtained under similar blending conditions. TPU/PE blends show a lower dispersity than TPU/PP blends, due to the higher viscosity ratios of TPU/PE blends. This results in a greater reduction in tensile strength with the disperse phase content. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 749–762, 1997     

Polyoxymethylene/thermoplastic polyurethane blends compatibilized with multifunctional chain extender

Novel compatibilized polyoxymethylene/thermoplastic polyurethane (POM/TPU) blends are successfully developed using multifunctional chain extender, Joncryl ADR‐4368, as the compatibilizer. The outstanding compatibilization efficiency of Joncryl on POM/TPU blend was demonstrated by its even higher mechanical properties with only 0.5 wt % of Joncryl than those with 5 wt % of three commonly used compatibilizers. Addition of only 0.5 wt % Joncryl can double the impact strength and significantly improve its tensile strength and flexural strength for POM/TPU (75/25) blend. SEM images show that Joncryl can reduce TPU particle size and enhance the interfacial interactions between POM and TPU. The interparticle distance of TPU in POM/TPU/Joncryl blends was calculated as 0.2 μm, quite close to the critical matrix ligament thickness of POM/TPU blends (0.18 μm). The impact force profile vividly shows that the addition of Joncyl in POM/TPU blends can dramatically increase the total impact energy absorbed by this blend system and enhance the interfacial interactions between POM and TPU. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

异氰酸酯对聚乳酸/热塑性聚氨酯共混物性能的影响

以4,4^′-二苯基甲烷二异氰酸酯（MDI）为反应增容剂，采用熔融共混法制备了不同MDI含量的聚乳酸/热塑性聚氨酯（PLA/TPU）共混物，采用傅里叶变换红外光谱仪（FTIR）、万能试验机、冲击试验机、扫描电子显微镜（SEM）、差示扫描量热仪（DSC）和旋转流变仪对共混物力学性能、微观形态、热性能和流变性能进行了研究。结果表明：MDI可以有效改善共混物的力学性能，当MDI质量分数为1%时，共混物力学性能最佳，缺口冲击强度为40.0kJ/m²，断裂伸长率为214.1%，与未加MDI的共混物相比，分别增加了4.3倍和5.8倍，拉伸强度稍有下降（47.6MPa）；SEM表明，MDI的加入提高了共混物的相容性，加入MDI后，共混物的断面由海-岛结构变为核-壳包覆结构，相界面作用力增强；DSC测试表明，共混物的玻璃化转变温度、冷结晶温度和熔融温度随着MDI含量的增加而升高；流变测试表明，MDI质量分数的增加，共混物呈现更显著的剪切变稀行为，推测共混反应机理为：MDI质量分数的增加，体系内依次发生PLA的扩链、支化和TPU的交联。     

Influence of fluorine interface to the crystallization of poly (vinylidene fluoride)/silicone rubber/fluororubber elastomeric tertiary blends via dynamical curing

ABSTRACT

We demonstrate the influence of fluorine interface to the crystallization of poly(vinylidene fluoride) (PVDF)/silicone rubber (SR)/fluororubber (FKM) tertiary dynamic curing blends. In contrast to PVDF/SR binary blend, the average size of PVDF spherulites turns smaller and the crystallization rate is lower in PVDF/SR/FKM tertiary blend when more fluororubber component was added into the blends at the same crystallization temperature. Incorporation of FKM does not change the crystalline form of PVDF in the blends. The resulting mechanical properties of tensile strength, flexural strength, Izod impact strength and elongation at break for PVDF/SR/FKM tertiary blends are enhanced compared with PVDF/SR binary blend.     

Morphology and mechanical properties of thermoplastic elastomers from nylon-nitrile rubber blends

Nylon-nitrile rubber blends having different plastic-rubber component ratios (100/0, 80/20, 70/30, 60/40, 50/50, 40/60, 30/70, 20/80, and 0/100) were prepared by melt mixing technique in a Rheocord-90 at a temperature set at 180°C. The mixing characteristics of the blends have been analyzed from the rheographs. The morphology of the blend was studied using optical and electron microscopies, with special reference to the effect of blend ratio. The micrographs indicate a two-phase system where the component having lower proportions was found to disperse in the major continuous phase. A cocontinuous morphology was observed for 50/50 composition. Mechanical properties of the blends have been measured according to standard test methods. The effect of blend ratio on the mechanical properties like tensile strength, tear strength, elongation at break, stress-strain behavior, and hardness has been analyzed. The influence of the strain rate on the mechanical properties has also been analyzed. The mechanical properties were found to have a strong dependence on the amount of nylon in the blend. It is found that the blends with higher proportions of nylon have superior mechanical properties. The observed changes in mechanical properties are explained on the basis of the morphology of the blend. Various theoretical models such as Series, Parallel, Halpin-Tsai, and Coran's equations have been used to fit the experimental mechanical data. © 1996 John Wiley & Sons, Inc.     

Morphologies and mechanical properties of polylactide/thermoplastic polyurethane elastomer blends

To explore a potential method for improving the toughness of a polylactide (PLA), we used a thermoplastic polyurethane (TPU) elastomer with a high strength and toughness and biocompatibility to prepare PLA/TPU blends suitable for a wide range of applications of PLA as general‐purpose plastics. The structure and properties of the PLA/TPU blends were studied in terms of the mechanical and morphological properties. The results indicate that an obvious yield and neck formation was observed for the PLA/TPU blends; this indicated the transition of PLA from brittle fracture to ductile fracture. The elongation at break and notched impact strength for the PLA/20 wt %TPU blend reached 350% and 25 KJ/m², respectively, without an obvious drop in the tensile strength. The blends were partially miscible systems because of the hydrogen bonding between the molecules of PLA and TPU. Spherical particles of TPU dispersed homogeneously in the PLA matrix, and the fracture surface presented much roughness. With increasing TPU content, the blends exhibited increasing tough failure. The J‐integral value of the PLA/TPU blend was much higher than that of the neat PLA; this indicated that the toughened blends had increasing crack initiation resistance and crack propagation resistance. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Compatibilization of PVDF/PA6 Blend by the Addition of a Third Polymer PTFE

The compatibilization of poly(vinylidene fluoride) (PVDF) with polyamide 6(PA6, higher acrylonitrile content) blend was improved by adding poly(methyl methacrylate) (PTFE). It was confirmed by characterizing the mechanical and tribological properties of the blends. More homogeneous morphology was formed when PTFE was added into PVDF/PA6 blend, which was shown in scanning electron microscopy (SEM). The surface tension of blends was increased due to the higher polar surface tension of PTFE. As the content of PTFE was increased further, the tensile strength of the blend was slightly decreased.     

Tensile,stress-strain and creep rupture properties of poly (vinyl chloride)/poly(neopentyl glycol adipate)/poly(vinylidene fluoride) blends

Poly (vinyl chloride), PVC, and poly(vinylidene fluoride), PVDF, are incompatible polymers. Poly(neopentyl glycol adipate), PDPA, is miscible with both PVC and PVDF. With PDPA acting as a compatibilizer between PVC and PVDF. compatible PVC/PDPA/PVDF blends can be formed at PVDF content of about less than 50wt%. Above 50wt% PVDF the ternary blends exist in two phases exhibiting two glass transition temperatures, T_g, PVC is the main contributor to the mechanical strength while PDPA and PVDF contribute to the elastic properties of these blends. A compatible blend of 55/22.5/22.5 wt% PVC/PDPA/PVDF exhibiting one single T_g appears to show an interesting balance of the properties of the blend components.     

Impact modification of polyacetal by thermoplastic elastomer polyurethane

The main goal of this study was impact modification of polyacetal [polyoxymethylene (POM)] with thermoplastic elastomer polyurethane (TPU). We modified the impact strength of POM 10‐fold. The mechanical properties, thermal behavior, and morphology of POM/TPU blends consisting of 5 to 50% of TPU were studied. It was found that the best impact modification of the blends was at 15% concentration of TPU and the maximum elongation at break was at 30% concentration of TPU. The impact strength of POM/TPU blends can be improved by using diphenylmethane diisocyanate (MDI) as compatibilizer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2573–2582, 2002     

Thermoplastic elastomers-based natural rubber and thermoplastic polyurethane blends

Thermoplastic elastomers based on the blends of thermoplastic polyurethane (TPU) and natural rubber were prepared by a simple blend technique. The influence of the two different types of natural rubber (i.e., unmodified natural rubber (NR) and epoxidized natural rubber (ENR)) on properties of the blends was investigated. The main aim of this study was to improve heat resistance and damping properties, and also to prepare the TPU material with low hardness by blending with various amounts of natural rubber. It was found that the TPU/ENR blends exhibited superior modulus, hardness, shear viscosity, stress relaxation behavior and heat-resistant properties compared to the blends with TPU and unmodified NR. This was attributed to higher chemical interaction between the polar functional groups of ENR and TPU by improving the interfacial adhesion. It was also found that the ENR/TPU blends exhibited finer grain morphology than the blends with unmodified NR. Furthermore, lower tension set, damping factor (Tan ??) and hardness, but higher degradation temperature, were observed in natural rubber/TPU blends compared to pure TPU. This proves the formation of TPU material with high heat resistance, low hardness and better damping properties. However, the blends with higher proportion of natural rubber exhibited lower tensile strength and elongation at break.     

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

Blends 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.