Super toughened and highly ductile PLA/TPU blend systems by in situ reactive interfacial compatibilization using multifunctional epoxy-based chain extender

This study investigates the influence of using multifunctional epoxy Joncryl ADR 4468 chain extender (CE) on the properties of various polylactide (PLA)/thermoplastic polyurethane (TPU) (75 wt/25 wt) blend systems. The blends were based on two different TPU grades with ether- and ester-based soft segment as the dispersed phase (i.e., TPUether and TPUester) and an amorphous and a semicrystalline PLA grades as the matrix (i.e., aPLA and scPLA). PLA appeared to be more compatible with the TPUester, which caused the enhancement of the impact strength and strain at break values of the blends more remarkably. The dynamic rheological experiments also confirmed that the CE revealed a better reactivity with TPUester than TPUether. This further enhanced the interfacial compatibility between the PLA and TPUester and thereby dramatically improved the impact strength and ductility of the PLA/TPUester blends, specifically those with 0.5 wt% CE. Meanwhile, aPLA as the matrix reflected the TPUs toughening effect more efficiently than scPLA. This was due to the possible shrinkage caused by the crystallization of scPLA matrix, which could deteriorate the interfacial interactions between the phases in the corresponding blends.     

Toughening mechanism in polyoxymethylene/thermoplastic polyurethane blends

In order to better understand the toughening mechanism in polyoxymethylene (POM)/thermoplastic polyurethane (TPU) blends and obtain ‘super‐toughened’ POM, we carried out an investigation on the notched impact strength, fractured surface, inter‐particle distance and spherulite size of POM as a function of the TPU content. A compatibilizer, namely polystyrene‐block‐poly(ethylene–butylene)‐block‐polystyrene, grafted with maleic anhydride (SEBS‐graft‐MA), was used to enhance the interfacial interaction between the POM and TPU. The impact strength is found to increase in two steps as a function of TPU content, namely a linear increase at the very beginning, and then a jump of impact strength is seen when the TPU content is larger than 30 wt%. A ‘supertough behavior’ is not observed for POM/TPU blends at room temperature, but can be achieved after adding 5 wt% of SEBS‐graft‐MA as the compatibilizer. The impact strength was found to depend not only on the interparticle distance but also on the interfacial interactions between POM and TPU. The dependence of impact strength on crystal size is considered for the first time, and a single curve is constructed, regardless of the composition and interfacial interactions. Our results indicate that the crystal size of POM indeed plays a role in determining the toughness, and has to be considered when discussing the toughening mechanism. Copyright © 2004 Society of Chemical Industry     

Interfacial reaction and its influence on phase morphology and impact properties of modified‐polyacetal/thermoplastic polyurethane blends

The cationic polymerization of 1,3,5‐trioxane, 1,3‐dioxolane and a small amount of 2‐hydroxyacetic acid (HAA) was carried out, and the resulting modified‐polyacetal (POM) was blended with thermoplastic polyurethane (TPU) in melt. The results of ¹H NMR analysis indicated that HAA was almost incorporated in the modified‐POM, and that the resulting carboxyl end‐group and hydroxyl end‐group in the modified‐POM reacted with TPU during the melt blending. There were many boundary layers between the cavities and matrix in the modified‐POM/TPU (82/18 by weight) blend that was etched with tetrahydrofuran (THF), and the diameter of the cavities became ～0.3–1 μm long when the blending time reached 10 min. The results of scanning electron microscopic (SEM) observation and dynamic mechanical analysis (DMA) indicated that the modified‐POM/TPU blend had a good compatibility because of the interfacial reaction between the modified‐POM and TPU phase in the blend. The modified‐POM/TPU blend exhibited higher Charpy impact strength when compared with a normal‐POM/TPU blend; the toughness of the modified‐POM/TPU blend attributed to the good compatibility between the two phases. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4375–4382, 2006     

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.     

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.     

TPU增韧改性POM的研究

利用双螺杆挤出机制备了聚甲醛(POM)/热塑性聚氨酯弹性体(TPU)和POM/TPU/异氰酸酯预聚物(Z)共混物.采用力学性能测试方法、偏光显微镜(PLM)、傅立叶转换红外线光谱 (FTIR)、扫描电子显微镜(SEM)等研究了共混物的力学性能、结晶行为及形态结构.结果表明,不同种类TPU增韧的共混物的缺口冲击强度和断裂伸长率都随TPU含量的增加而增加,TPU(95A)增韧的POM/TPU共混物的刚性较好,TPU(250)增韧的POM/TPU共混物的韧性较好;Z能促进TPU在基体树脂中的均匀分散,增强两相界面的粘结力,并能细化球晶.     

聚氨酯增韧聚甲醛的研究

采用机械共混的方法，制备了聚甲醛(POM)／热塑性聚氨酯弹性体(TPU)复合材料；研究了缺口曲率半径对纯POM以及TPU增韧体系冲击韧性的影响；并对其形态结构进行了测试分析。结果表明，纯POM的冲击韧性受缺口尖锐程度影响大，TPU能减小POM结晶度，缩小球晶尺寸，显著降低POM的缺口敏感性；POM／TPU形成双连续结构时成为超韧体系。     

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     

Compatibilization effects in thermoplastic protein/polyester blends

Novatein thermoplastic protein was extrusion blended with poly(butylene adipate‐co‐terephthalate) (PBAT) in the presence of dual compatibilizers to produce blends with greater energy absorbing properties than pure Novatein. Compatibilizer pairs were Joncryl ADR‐4368 (glycidyl methacrylate‐functionalized) with 2‐methylimidazole (2MI), and poly‐2‐ethyl‐2‐oxazoline (PEOX) with polymeric diphenyl methane diisocyanate (pMDI). Uncompatibilized Novatein/PBAT blends had decreased tensile mechanical properties, attributed to phase separation, and poor interfacial adhesion. PBAT became finely dispersed in both compatibilized systems, but PEOX/pMDI blends showed embrittlement and large Novatein domains, which acted as stress concentrations. Tensile strength and elongation at break for Joncryl/2MI blends did not decrease compared with Novatein, even at 10 wt % PBAT, and impact strength increased threefold. Dynamic mechanical analysis and solvent extraction showed that PBAT coalesced in all systems, at compositions as low as 2 wt %. It was concluded that using Joncryl/2MI as a dual compatibilizer system can successfully produce a morphology that enhances energy absorption during fracture. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45808.     

Morphology control of polyoxy‐methylene/thermoplastic polyurethane blends by adjusting their viscosity ratio

Polyoxymethylene (POM) is an important plastic with very good properties. However, its poor impact strength limits its applications. Theoretical and experimental studies have confirmed that thermoplastic polyurethane (TPU) can effectively enhance the notched impact strength of POM. This paper reports that the notched impact strength of POM/TPU blends can be further improved when these blends are endowed with a fine morphology by changing the viscosity ratio of TPU to POM (P = η_TPU/η_POM) during processing. The experimental results show that the viscosity of TPU is more sensitive to temperature than that of POM, and that the viscosity ratio P decreases with increasing temperature; also for quite a wide range of shear rate, P is close to 1 when the processing temperature (T_p) is around 190 °C. Accordingly, the phase structure of POM/TPU blends changes with P. The dispersed phase of TPU shows ellipsoidal morphology when P > 1 at T_p < 190 °C, filamental morphology when P ≈ 1 at T_p ≈ 190 °C and spheroidal morphology when P < 1 at T_p > 190 °C. The results suggest that the filamental morphology endows POM/TPU (90/10) blends with the highest notched impact strength (～14 kJ m^?2). Copyright © 2006 Society of Chemical Industry     

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％。     

含异氰酸酯基的低聚物和聚醚增容改性POM/TPU共混物

利用双螺杆挤出机制备了聚甲醛(POM)/热塑性聚氨酯弹性体(TPU)、POM/TPU/含异氰酸酯基的低聚物(Z)以及POM/TPU/Z/聚醚3种共混物。采用力学性能测试、差示扫描量热分析(DSC)、偏光显微镜(PLM)、傅里叶转换红外线光谱 (FTIR)、扫描电子显微镜(SEM)、动态力学性能分析(DMA)等,研究了3种共混物的力学性能、结晶行为及形态结构。结果表明：共混物的缺口冲击强度和断裂伸长率随TPU含量的增加而提高;异氰酸酯基低聚物（Z）和聚醚在促进分散相分散、增强两相间的相容性方面发挥重要作用,降低了聚甲醛的结晶度,能够有效地提高共混物的缺口冲击强度和断裂伸长率。     

Morphology,thermal, and mechanical properties of polyacetal/ionomer blends

This study is directed towards the development of modifiers for and the understanding of their role in improving the impact properties of an engineering polymer, polyacetal (POM). It is demonstrated that modifiers that induce ion-dipole interactions can lead to substantial enhancements in the room temperature impact performance of POM without sacrificing its unique balance of mechanical, thermal, and chemical resistance properties. The mechanical and physical properties of blends of a commercial copolymer type polyacetal (POM) with terpolymers of ethylene, methylacrylate and acrylic acid (EAAT) and its zinc ionomer form (EAAT-Zn), are reported. Substantial differences both in the mechanical and impact performance were found in these two modified POM systems. DSC and optical microscopy studies of such blends demonstrates only minor differences in the microcrystalline structure of the two blend systems. A nearly three fold reduction in the spherulite size of POM was found from addition of as little 5% of either modifier, thus ruling out this mechanism for the observed increased toughness of the blends. Dynamic mechanical measurements and cryofractured surface microscopy observations indicate that enhancements in the physical properties of POM modified with zinc ionomers of EAAT are due to enhanced interfacial adhesion and to the (inherent) mechanical rigidity (due to ionic interactions), of the modifier. In these blends the tensile and impact strength are found to be a function of the degree of neutralization of the terpolymer acid content. In particular, an optimum balance of impact and tensile properties is obtained with partial neutralization (in the range of 25 to 50% of the terpolymer acid content) and at modifier addition levels in POM in the range of 5 to 10%. The EAAT modifier for POM was found to be ineffective even up to 20% addition as compared to EAAT-Zn modifier. Ion-dipole interactions are thus shown to be more influential than the hydrogen bonding that occurs in EAAT-POM blends. The study suggests a new approach to modify polar engineering polymers via such interactions.     

Compatibilization of an immiscible blend of EPDM and POM with an Ionomer

Immiscible blends of ethylene-propylene-diene-monomer (EPDM) and polyoxymethylene (POM), when EPDM is the major phase were compatibilized on the addition of an ionomer, poly(ethylene-co-methacrylic acid). The inclusion of the ionomer reduced the interfacial tension between the two phases, such that the diameter of the POM domains were significantly reduced to between 0.5 and 2 μm, typical of that required to toughen ductile polymers. The mechanical properties of the resultant compatibilized blends were significantly enhanced with increases in Young's modulus (↑54%), tensile strength (σ, ↑139%), elongation at break (ε, ↑97%), and tensile toughness (↑500%) with increasing ionomer content, relative to EPDM rubber alone. The ShoreA hardness of the compatibilized blend was 70.1 compared with 56.8 for the immiscible binary blend and, 50.2 for neat EPDM rubber.     

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     

Studies on thermal stability and behaviour of polyacetal and thermoplastic polyurethane elastomer blends

The influence of thermoplastic polyurethane (TPU) elastomer on the rigidity of polyacetal (polyoxymethylene, POM) was studied by determining heat deflection temperature (HDT). The higher the content of TPU in the POM/TPU blend, the lower the HDT of the blend, as would be expected. A comparative study of the recycle capability of POM and the blends was carried out by measuring melt flow index (MFI) on each successive extrusion. Stress-strain behaviour of the virgin material and that obtained after fourth-time extrusion was analysed for POM and the blends. The effect of γ-radiation on the mechanical behaviour of the blends was investigated. The kinetics of thermal degradation of POM, TPU and their blends was studied. The kinetic parameters, viz. activation energy and the order of reaction, were established. The values of the activation energy of the blends were found to be higher than those of the POM and TPU, indicating improved stability of the resultant blends.     

Investigation of structure and mechanical properties of toughened poly(l‐lactide)/thermoplastic poly(ester urethane) blends

In this study, poly(l ‐lactide) (PLA) is melt‐blended with thermoplastic polyurethane (TPU) to modify the brittleness of PLA. An aliphatic ester‐based TPU was selected in order to have an ester sensitivity for degradation and an inherent biocompatibility. Using this compatible TPU, there was no need to apply problematic compatibilizers, so the main positive properties of PLA such as biocompatibility and degradability were not challenged. The detected microstructure of PLA/TPU blends showed that when the TPU content was lower than 25 wt %, the structure appeared as sea‐islands, but when the TPU content was increased, the morphology was converted to a cocontinuous microstructure. A higher interfacial surface area in the blend with 25 wt % TPU (PLA25) resulted in a higher toughness and abrasion resistance. The various analyses confirmed interactions and successful coupling of two phases and confirmed that melt‐blending of PLA with the aliphatic ester‐based TPU is a convenient, cost‐effective, and efficient method to conquer the brittleness of PLA. The prepared blends are general‐purpose plastics, but PLA25 showed an optimum mechanical strength, toughness, and biocompatibility suitable for a wide range of applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43104.     

Stress relaxation behavior of polyacetal–thermoplastic polyurethane elastomer blends

The yield stress of polyacetal (POM) decreases monotonically with the incorporation of thermoplastic polyurethane (TPU) elastomer in POM/TPU blends as would be anticipated. However, the impact strength of the resultant POM/TPU blends increases initially up to 30% TPU and thereafter decreases with the addition of TPU. Stress relaxation measurements in simple extension were carried out for POM and its blends with 10, 20, and 30% TPU at a constant temperature (30°C). Rate of loss of the relaxation modulus was found to be a nonlinear function of time. It has been demonstrated that the stress relaxation modulus values measured at different strains can be superimposed by a shift along the logarithmic time axis to yield master curves of modulus over an extended time period. It has also been found that while it is possible to determine, at any strain, relaxation curves covering an appreciable time range, the demarcation of linear and nonlinear behavior ranges of stress could not be done for these materials as all the strain values chosen in our experiments were in the region of linear behavior. © 1993 John Wiley & Sons, Inc.     

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     

环氧聚合型扩链剂对POM/TPU共混体系的相容作用

使用环氧聚合型扩链剂作为POM/TPU共混物的相容剂,研究其对POM/TPU共混物的流变性能、力学性能、结晶性能和耐热性的影响。结果表明,添加环氧聚合型扩链剂后,POM/TPU共混物的熔体流动速率先升高然后降低;冲击强度提高,断裂伸长率大幅提高;结晶度先升高后降低;热变形温度提高。