The effect of epoxide content on compatibility of poly(lactic acid)/epoxidized natural rubber blends

The objective of this work was to determine the effect of the epoxide content in epoxidized natural rubber (ENR) on the miscibility and compatibility with poly(lactic acid) (PLA) in prepared PLA/ENR blends. PLA was blended with 10 wt% of ENRs (epoxidized at 10, 15, 20, and 25 mol%). The presented study showed that the in situ graft copolymer, PLA-g-ENR, was formed during melt blending in the blends containing 10 and 15 mol% ENR. This work is the initial study showing the presence of PLA-g-ENR in the blends by ¹H-NMR and ¹³C-NMR. PLA-g-ENR acted as a compatibilizer, producing a partially miscible blend, indicated by an inward shift of the α-transition temperatures of PLA and ENR in the blends. PLA-g-ENR also greatly reduced the particle size of ENR and increased the impact strength, tensile strength, and elongation at break of the blends. The epoxide content of ENR changed deformation mechanisms of the blends.     

Compatibilization of poly(lactic acid)/epoxidized natural rubber blend with maleic anhydride

The objective of this work was to determine the compatibilization effect of different concentrations of maleic anhydride (MA) in poly(lactic acid) blended with epoxidized natural rubber (PLA/ENR). ENR-grafted MA [ENR-g-MA] was synthesized using four concentrations of MA: 0.15, 0.30, 0.45, and 0.60 phr. Using an internal mixer, binary (PLA/ENR, PLA/ENR-g-MA) and ternary (PLA/ENR/ENR-g-MA) polymer blends were prepared with a constant rubber content of 10 wt %. ENR impaired the mechanical properties of PLA, perhaps due to the relatively large size of the rubber particles. The compatibilization effect of MA was evaluated from the results of impact strength testing. ENR-g-MA was a toughening agent for PLA when the concentration of MA was in the range of 0.30–0.60 phr. MA increased miscibility between PLA and ENR. This effect was indicated in the blends by reductions in rubber particle size, the glass transition temperature of PLA, and the α-transition temperatures of PLA and ENR. In the binary polymer blends, the MA concentration in ENR-g-MA that produced the optimal mechanical properties of PLA was 0.60 phr. In the ternary blends, mechanical properties of PLA did not improve at any concentration of MA in ENR-g-MA. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48297.     

Effect of organoclay on non-linear rheological properties of poly(lactic acid)/poly(caprolactone) blends

The nonlinear viscoelastic properties of PLA/PCL blends with and without clay (montmorillonite, MMT) under large amplitude oscillatory shear (LAOS) flow were investigated. The G′ and G″ as a function of strain amplitude, Lissajous plots and FT-rheology methods were used to interpret nonlinear behavior of PLA/PCL blends with and without MMT. Additionally, scanning electron microscopy (SEM) images of PLA/PCL with MMT blends were taken to investigate the effects of clay on the internal structure of the PLA/PCL blends. A relationship between morphological changes and linear and nonlinear rheological properties was observed. SEM image analysis revealed that clay acted as a compatibilizer and then reduced the size of droplets in the PCL domain of the PLA matrix. As a result, nonlinear properties sensitively reflect morphological changes with increasing MMT amount. The nonlinear rheological properties of PLA/PCL/MMT/metallocene-LLDPE (mLLDPE) were also investigated when mLLDPE was used as an impact modifier to improve mechanical properties, and the nonlinear rheological properties of PLA/PCL/MMT and PLA/PCL/MMT/mLLDPE were also compared.     

The Effect of Epoxidized Natural Rubber (ENR-50) or Polyethylene Acrylic Acid (PEA) as Compatibilizer on Properties of Ethylene Vinyl Acetate (EVA)/Natural Rubber (SMR L) Blends

The effect of epoxidized natural rubber (ENR) or polyethylene acrylic acid (PEA) as a compatibilizer on properties of ethylene vinyl acetate (EVA)/natural rubber (SMR L) blends was studied. 5 wt.% of compatibilizer was employed in EVA/SMR L blend and the effect of compatibilizer on tensile properties, thermal properties, swelling resistance, and morphological properties were investigated. Blends were prepared by using a laboratory scale of internal mixer at 120°C with 50 rpm of rotor speed. Tensile properties, thermal properties, thermo-oxidative aging resistance, and oil swell resistance were determined according to related ASTM standards. The compatibility of EVA/SMR L blends with 5 wt.% of compatibilizer addition or without compatibilizing agent was compared. The EVA/SMR L blend with compatibilizer shows substantially improvement in tensile properties compared to the EVA/SMR L blend without compatibilizer. Compatibilization had reduced interfacial tension and domain size of ethylene vinyl acetate (EVA)/natural rubber (SMR L) blends.     

Study of biodegradable polylactide/poly(butylene carbonate) blend

Polylactide (PLA) was melt blended with poly(butylene carbonate) (PBC) in an effort to improve the toughness of the PLA without compromising its biodegradability and biocompatibility. The miscibility, morphology, thermal behavior, and mechanical properties of the blends were investigated. The blend was an immiscible two‐phase system with PBC uniformly dispersed within the PLA matrix. Because of the interfacial function, the incorporation of PBC accelerated the crystallization rate of PLA. By the incorporation of PBC, a polylatide‐based material with high stiffness and toughness was achieved. Even at 10% of PBC, high elongation at break of 139% was obtained, while the tensile strength remained as high as 50.7 MPa. The Pukanszky model gave credit to modest interfacial adhesion between PLA and PBC although PLA/PBC is an immscible blend. The plastic deformation, occurring via debonding process, is an important energy‐dissipation process and leads to a toughened, biodegradable polymer blend. The important point is that the toughening mechanism requires only modest level of adhesion between particles and the polymer. The molecular mobility is a crucial factor for yield stress and plastic flow. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Dynamic Mechanical and ESCA Studies of Aluminium-Aluminium Bonding by an Epoxidised Natural Rubber-Polyacrylic Acid Blend

A polyacrylic acid (PAA)-epoxidised natural rubber (ENR) blend becomes crosslinked during high temperature moulding and such a blend was found to be a good adhesive for aluminium (Al)-aluminium (Al) bonding. The joint strength can be improved by the incorporation of silica filler into the adhesive up to a loading of 5 phr. However, higher filler loading causes deterioration of the joint strength. Electron Spectroscopy for Chemical Analysis (ESCA) studies of the peeled and then leached Al surface shows that the ENR phase of the blend is primarily responsible for the adhesion with the Al surface. With the increase in filler loading adhesion with Al increases at the cost of crosslinking between the component polymers. This is substantiated by dynamic mechanical analyses of the blends and joints (that is, Al/blend/Al composites). The changes in dynamic mechanical properties of the blends due to Al adhesion could be correlated with the peel strength of the Al/blend/Al joints.     

High‐performance bio‐based poly(lactic acid)/natural rubber/epoxidized natural rubber blends: effect of epoxidized natural rubber on microstructure,toughness and static and dynamic mechanical properties

Attempts have been made to prepare high‐performance bio‐based blends through blending of poly(lactic acid) (PLA) with natural rubber (NR) in the presence of epoxidized natural rubber (ENR) as a compatibilizer. The prepared samples were characterized using differential scanning calorimetry, measuring the tensile properties and impact resistance, scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy and dynamic mechanical analysis (DMTA). Morphological studies revealed a matrix‐dispersed morphology for all blends, in which the average droplet size significantly decreased with the use of ENR. The elongation at break and impact strength of the blend containing 3 wt% ENR were 45 and 16 times those of neat PLA, respectively. These values are significantly higher than those previously reported for various simple and dynamically vulcanized rubber‐toughened PLAs. The influence of ENR on compatibility was confirmed by rheological tests, FTIR spectra and DMTA. DMTA also showed a marked increase in elastic modulus for the blend in the presence of 3 wt% ENR. The tensile properties and impact resistance were directly dependent on the ENR content and rubber droplet size. © 2018 Society of Chemical Industry     

Effect of epoxidized natural rubber on thermal properties,fatigue life,and natural weathering test of styrene butadiene rubber/recycled acrylonitrile‐butadiene rubber (SBR/NBRr) blends

The utilization of waste rubber powder in polymer matrices provides an attractive strategy for polymer waste disposal. Addition of recycled acrylonitrile‐butadiene rubber (NBRr) in rubber compounds gives economic (lowering the cost of rubber compounds) as well as processing advantages. In this study, the properties of styrene butadiene rubber (SBR)/NBRr blends with and without epoxidized natural rubber (ENR‐50) as a compatibilizer were determined. The results such as thermal gravimetric analysis (TGA), fatigue life, and natural weathering test of SBR/NBRr blends with and without ENR‐50 were carried out. Results showed that TG thermograms of SBR/NBRr blends with ENR‐50 show lower thermal stability compared blends without ENR‐50. The incorporation of ENR‐50 into SBR/NBRr blends has reduced char residue compared SBR/NBRr blends without ENR‐50. The incorporation of ENR‐50 in SBR/NBRr blends has increased the rigidity of the blends thus lowering the fatigue life. The increment in tensile properties retention of SBR/NBRr blends with ENR‐50 indicated the enhancement on weathering resistant. The surfaces of SBR/NBRr blends with ENR‐50 after 6 months exposure showed a minimal severity of crack compared with SBR/NBRr blends without ENR‐50. It revealed that the scale of cracks has reduced indicating well‐retaining interfacial adhesion between SBR and NBRr with the presence of ENR‐50 as a compatibilizer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of (3-aminopropyl)trimethoxysilane on mechanical properties of PLA/PBAT blend reinforced kenaf fiber

The composite-based poly(lactic acid) (PLA)/poly(butylene adipate-co-terephthalate) (PBAT)/kenaf fiber has been prepared using melt blending method. A PLA/PBAT blend with the ratio of 90:10 wt%, and the same blend ratio reinforced with various amounts of kenaf fiber have been prepared and characterized. However, the addition of kenaf fiber has reduced the mechanical properties sharply due to the poor interaction between the fiber and polymer matrix. Modification of the composite by (3-aminopropyl)trimethoxysilane (APTMS) showed improvements in mechanical properties, increasing up to 42.46, 62.71 and 22.00 % for tensile strength, flexural strength and impact strength, respectively. The composite treated with 2 % APTMS successfully exhibited optimum tensile strength (52.27 MPa), flexural strength (64.27 MPa) and impact strength (234.21 J/m). Morphological interpretation through scanning electron microscopy (SEM) reveals improved interaction and interfacial adhesion between PLA/PBAT blend and kenaf fiber. The fiber was well distributed and remained in the PLA/PBAT blend evenly. DMA results showed lower storage modulus (E′) for PLA/PBAT/kenaf fiber blend and an increase after modification by 2 wt% APTMS. Conversely, the relative damping properties decreased. Based on overall results, APTMS can be used as coupling agent for the composite since APTMS can improve the interaction between hydrophilic natural fibers and non-polar polymers.     

Bio‐based diblock copolymers prepared from poly(lactic acid) and natural rubber

New bio‐based diblock copolymers were synthesized from poly(lactic acid) (PLA) and natural rubber (NR). NR polymer chains were modified to obtain hydroxyl telechelic natural rubber oligomers (HTNR). Condensation polymerization between PLA and HTNR was performed at 110°C during 24 or 48 h. The molecular weight of PLA and HTNR and the molar ratio PLA : HTNR were varied. The new ester linkage in the diblock copolymers was determined by ¹H‐NMR. The molecular weight of the diblock copolymers determined from SEC agreed with that expected from calculation. The thermal behavior and degradation temperature were determined by DSC and TGA, respectively. The diblock copolymers were used as a toughening agent of PLA and as a compatibilizer of the PLA/NR blend. PLA blended with the diblock copolymer showed higher impact strength, which was comparable to the one of a PLA/NR blend. The former blend showed smaller dispersed particles as showed by SEM images, indicating the increase in miscibility in the blend due to the PLA block. The compatibilization was effective in the blends containing ～10 wt % of rubber. At a higher rubber content (>10 wt %), coalescence of the NR and diblock copolymer was responsible of the larger rubber diameter in the blends, which causes a decrease of the impact strength. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41426.     

Preparation and characterization of shape memory polymer networks based on carboxylated telechelic poly(ɛ-caprolactone)/epoxidized natural rubber blends

Shape memory polymer networks were prepared from blends of end-carboxylated telechelic poly(?-caprolactone) (XPCL) and epoxidized natural rubber (ENR). The XPCL/ENR blends can form cross linked structure via interchain reaction between the reactive groups of each polymer during molding at high temperature. Degree of crosslinking of the blend network and their thermomechanical properties were characterized by gel content measurement, DSC and DMA. We found that the degree of crosslinking and crystalline melting transition temperatures was dependent upon the blend compositions as well as the molecular weight of the XPCL segment in the blends. The blends showed a good shape memory behavior such as good shape fixity as well as a high final recovery rate when they exhibit crystalline melting transition with a sufficiently high degree of crosslinking. And the response temperature of the recovery was well matched with T_m of the samples.     

Rheological and thermal properties of thermoplastic natural rubbers based on poly(methyl methacrylate)/epoxidized‐natural‐rubber blends

Epoxidized natural rubbers (ENRs) with epoxide levels of 10, 20, 30, 40, and 50 mol % were prepared. The ENRs were later blended with poly(methyl methacrylate) (PMMA) with various blend formulations. The mixing torque of the blends was observed. The torque increased as the PMMA contents and epoxide molar percentage increased in the ENR molecules. Furthermore, the shear stress and shear viscosity of the polymer blends in the molten state increased as the ENR content and epoxide molar percentage increased in the ENR molecules. Chemical interactions between polar groups in the ENR and PMMA molecules might be the reason for the increases in the torque, shear stress, and viscosity. All the ENR/PMMA blends exhibited shear‐thinning behavior. This was observed as a decrease in the shear viscosity with an increase in the shear rate. The power‐law index of the blends decreased as the ENR contents and epoxide molar percentage increased in the ENR molecules. However, the consistency index (or zero shear viscosity) increased as the ENR contents and epoxide molar percentage increased. A two‐phase morphology was observed with scanning electron microscopy. The small domains of the minor components were dispersed in the major phase. For the determination of blend compatibility, two distinct glass‐transition‐temperature (T_g) peaks from the tan δ/temperature curves were found. Shifts in T_g to a higher temperature for the elastomeric phase and to a lower temperature for the PMMA phase were observed. Therefore, the ENR/PMMA blends could be described as partly miscible blends. According to the thermogravimetry results, the decomposition temperatures of the blends increased as the levels of ENR and the epoxide molar percentage increased. The chemical interactions between the different phases of the blends could be the reason for the increase. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3561–3572, 2004     

Mechanical properties of poly(lactic acid) and wheat starch blends with methylenediphenyl diisocyanate

Poly(lactic acid) (PLA) and wheat starch are biodegradable polymers derived from renewable sources. A previous study showed that thermally blending starch and PLA in the presence of methylenediphenyl diisocyanate (MDI) enhanced the mechanical properties of the blends. In this work, blends of PLA with various levels of wheat starch and MDI were hot mixed at 180°C then hot‐pressure molded at 175°C to form test specimens. The blends were characterized for mechanical properties, fracture microstructure, and water absorption. Pure PLA had a tensile strength of 62.7 MPa and elongation of 6.5%. The blend with 45% wheat starch and 0.5 wt % MDI gave the highest tensile strength of about 68 MPa with about 5.1% elongation. The blend with 20% starch and 0.5 wt % MDI had the lowest tensile strength of about 58 MPa with about 5.6% elongation. Dynamic mechanical analysis showed that storage modulus increased and tan δ decreased as starch level increased, but almost leveled off when starch level reached 45% or higher. Water absorption of the blends increased significantly with starch content. Yet the blend, if water proofed on its surface, has potential for short‐term disposable applications. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1257–1262, 2002; DOI 10.1002/app.10457     

丙烯酸酯接枝改性天然橡胶增韧聚乳酸

通过在天然橡胶(NR)分子链上接枝甲基丙烯酸甲酯(MMA)和丙烯酸丁酯(BA),制备了三种丙烯酸酯接枝改性NR:NR-g-PMMA,NR-g-PBA和NR-g-(PMMA,PBA)。采用核磁共振氢谱对三种接枝物进行了化学结构鉴定。将接枝改性后的NR和未改性的NR与PLA采用哈克密炼机熔融共混,分别制备了PLA/NR,PLA/NR-gPMMA,PLA/NR-g-PBA和PLA/NR-g-(PMMA,PBA)共混物,研究了接枝改性NR和未改性NR含量对共混物力学性能和热性能的影响。各共混物的拉伸弹性模量和拉伸强度均随接枝改性NR和未改性NR含量的增加而降低,断裂伸长率和缺口冲击强度随接枝改性NR和未改性NR含量的增加而提高。其中,PLA/NR-g-PBA共混物的断裂伸长率和缺口冲击强度比其它共混物提高的幅度大,当NR-g-PBA的质量分数为5%时,PLA/NR-g-PBA共混物的断裂伸长率达到78%,缺口冲击强度为5.2 k J/m2,而纯PLA的断裂伸长率仅为7.7%,缺口冲击强度为2.5 k J/m2,说明NR接枝分子柔顺性较高的BA更有利于促进其与PLA共混物的韧性提高。热分析结果表明,PLA/NR-gPBA共混物的热稳定性相比于纯PLA也有所提高。     

叶片挤出机制备PLA/MMT复合材料性能的研究

利用以拉伸形变为主导的叶片挤出机制备了不同质量比的聚乳酸/蒙脱土(PLA/MMT)纳米复合材料,通过透射电子显微镜(TEM)和X射线衍射仪(XRD)表征了该复合材料的微观结构及形貌,并探讨了不同含量的MMT对PLA/MMT复合材料的力学性能以及动态力学性能的影响。结果表明:PLA分子链插入MMT片层之间,形成了具有插层结构的PLA/MMT纳米复合材料;该复合材料的拉伸强度、拉伸模量及冲击强度均随着MMT含量的增加呈先增后减的趋势;当MMT含量为2.5%时,复合材料的综合力学性能达到最佳,其中拉伸模量比纯PLA提高了170%,冲击强度则提高了130%,说明少量MMT的加入对PLA能起到增强增韧的作用。另外,动态力学性能测试结果表明,随着MMT含量的增加,复合材料的玻璃化转变温度有下降的趋势。     

聚碳酸亚丙酯-聚乳酸共混熔纺纤维的制备与性能

以乙烯-马来酸酐共聚物(ZeMac)作为反应性相容剂,利用熔融纺丝法制备了聚碳酸亚丙酯(PPC)-聚乳酸(PLA)共混纤维。通过傅里叶变换红外光谱仪、热重分析仪、差示扫描量热分析仪、纤维强伸度仪等分别研究了共混纤维的分子结构、热稳定性、相容性及力学性能。结果表明:PLA的引入较大地提高了PPC的力学性能,加入少量的ZeMac可以有效地改善PPC的热稳定性,同时也能够提高共混体系的相容性。当PPC-PLA与PPC-PLA-ZeMac体系组分质量比分别为70/30和70/30/0.7时,其抗拉强度分别为11.23 MPa和20.83 MPa,较未改性的PPC分别提高了6.5倍和12.1倍,同时还能保持较高的断裂伸长率。该项研究为完全可生物降解PPC熔融共混纤维的工业化提供了可能性。     

Mechanical properties and morphological changes of poly(lactic acid)/polycarbonate/poly(butylene adipate‐co‐terephthalate) blend through reactive processing

The mechanical properties and morphological changes of poly(lactic acid) (PLA), polycarbonate (PC), and poly(butylene adipate‐co‐terephthalate) (PBAT) polymer blends were investigated. Several types of blend samples were prepared by reactive processing (RP) with a twin‐screw extruder using dicumyl peroxide (DCP) as a radical initiator. Dynamic mechanical analyses (DMA) of binary polymer blends of PC/PBAT indicated that each component was miscible over a wide range of PC/PBAT mixing ratios. DMA of PLA/PBAT/PC ternary blends revealed that PBAT is miscible with PC even in the case of ternary blend system and the miscibility of PLA and PBAT can also be modified through RP. As a result, the tensile strain and impact strength of the ternary blends was increased considerably through RP, especially for PLA/PBAT/PC = 42/18/40 (wt/wt/wt) with DCP (0.3 phr). Scanning electron microscopy (SEM) analysis of the PLA/PBAT/PC blends revealed many small spherical island phases with a domain size of approximately 0.05–1 μm for RP, whereas it was approximately 10 μm without RP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Enhancement of PVC/ENR blend properties by poly(methyl acrylate) grafted oil palm empty fruit bunch fiber

Effect of oil palm empty fruit bunch (OPEFB) fiber and poly(methyl acrylate) grafted OPEFB on several mechanical properties of poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blends were studied. The composites were prepared by mixing the fiber and the PVC/ENR blends using HAKEE Rheomixer at the rotor speed of 50 rpm, mixing temperature 150°C, and mixing period of 20 min. The fiber loadings were varied from 0 to 30% and the effect of fiber content in the composites on their ultimate tensile strength (UTS), Young's modulus, elongation at break, flexural modulus, hardness, and impact strength were determined. An increasing trend was observed in the Young's modulus, flexural modulus, and hardness with the addition of grafted and ungrafted fiber to the PVC/ENR blends. However the impact strength, UTS, and elongation at break of the composites were found to decrease with the increase in fiber loading. An increase in elongation at break and UTS and decrease in the flexural and Young's modulus was observed with the addition of PMA‐g‐OPEFB fiber compared to ungrafted fiber. This observation indicates that grafting of PMA onto OPEFB impart some flexibility to the blend. The morphology of cryogenically fractured and tensile fracture surfaces of the composites, examined by a scanning electron microscope shows that the adhesion between the fiber and the matrix is improved upon grafting of the OPEFB fiber. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal and mechanical properties of electron beam irradiated poly(vinyl chloride)/polystyrene blends

The effect of electron beam irradiation on the thermal and mechanical properties of poly(vinyl chloride)/polystyrene (PVC/PS) blends and PVC/PS blends containing epoxidized natural rubber (ENR) was studied. The thermogravimetric analysis study showed that the thermal decomposition of the plasticized PVC individual polymer goes through two stages, whereas PS decomposes through one stage. However, the temperature of the maximum rate of reaction (T_max) of PS is much higher than that for PVC and their blends. Meanwhile, the T_max was found to increase with increasing PS ratios in the blend. The thermal stability of PVC/PS blends was greatly increased after electron beam irradiation in comparison with unirradiated blends. Moreover, the addition of ENR to PVC/PS increased the thermal stability. On the other hand, the mechanical properties in terms of tensile strength and elongation at break of PVC/PS blends are lower than pure PVC polymer because of the immiscibility. However, the addition of ENR to the PVC/PS (80/20) blend increased the elongation at break from 114 to 321% associated with a small effect on the tensile properties. These behaviors were supported by structure morphology studies observations, which indicate an improvement in the interfacial adhesion between the phases. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

热处理对MMT填充PP的力学性能影响

研究了热处理对聚丙烯(PP)/钠基蒙脱土(MMT)复合材料力学性能的影响。结果表明:适当地对共混体系进行热处理,可有效改善材料的拉伸性能、弯曲性能及冲击性能,拉伸强度及弯曲强度最大增幅分别可提高2 MPa和4 MPa。PP/MMT共混体系力学性能的增加在于体系中聚合物结晶结构的完善及热应力的消除。