High performance HTLNR/epoxy blend—Phase morphology and thermo-mechanical properties

An attempt was made to toughen diglycidyl ether of bisphenol A (DGEBA) type epoxy resin with liquid natural rubber possessing hydroxyl functionality (HTLNR). Epon 250 epoxy monomer is cured using nadic methyl anhydride as hardener in presence of N, N dimethyl benzyl amine as accelerator. HTLNR of different concentrations up to 20 wt % is used as modifier for epoxy resin. The addition HTLNR to an anhydride hardener/epoxy monomer mixture has given rise to the formation of phase-separated structure, consisting of small spherical liquid natural rubber particles bonded to the surrounding epoxy matrix. The particle size increased with increase in rubber content. The viscoelastic properties of the blends were analyzed using dynamic mechanical thermal analysis. The T_g corresponding to epoxy rich phase was evident from the dynamic mechanical spectrum, while the T_g of the rubber phase was overlapped by the β relaxation of epoxy phase. Glass transition of the epoxy phase decreased linearly as a function of the amount of rubber. The mechanical properties such as impact and fracture toughness were also carefully examined. The impact and fracture toughness increase with HTLNR content. A threefold increase in impact strength was observed with 15 wt % HTLNR/epoxy blend. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Polymer blends of epoxy resin and epoxidized natural rubber

The aim of this research was to investigate the behaviors of epoxy resin blended with epoxidized natural rubber (ENR). ENRs were prepared via in situ epoxidation method so that the obtained ENRs contained epoxide groups 25, 40, 50, 60, 70, and 80 mol %. The amounts of ENRs in the blends were 2, 5, 7, and 10 parts per hundred of epoxy resin (phr). From the results, it was found that the impact strength of epoxy resin can be improved by blending with ENRs. Tensile strength and Young's modulus were found to be decreased with an increasing amount of epoxide groups in ENR and also with an increasing amount of ENR in the blends. Meanwhile, percent elongation at break slightly increased when ENR content was not over 5 phr. In addition, flexural strength and flexural modulus of the blends were mostly lower than the epoxy resin. Scanning electron microscope micrograph of fracture surface suggested that the toughening of epoxy resin was induced by the presence of ENR globular nodules attached to the epoxy matrix. TGA and DSC analysis revealed that thermal decomposition temperature and glass transition temperature of the samples were slightly different. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 452–459, 2006     

Highly efficient in situ toughening of epoxy thermosets with reactive hyperbranched polyurethane

Hyperbranched polyurethane (HBPU), with low‐molecular‐weight polyethylene glycol space segments between the branching points, was synthesized by a pseudo one‐pot procedure. HBPU was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and gel permeation chromatography. The HBPU was used as a modifier of diglycidyl ether of bisphenol A (DGEBA)/anhydride system. The rheological properties of HBPU‐G3/DGEBA blends were investigated by rotational rheometer. A slight decrease in viscosity of modified blends was observed by adding low content of HBPU and there was chemical reaction between HBPU and epoxy resin even without a hardener. The mechanical and thermal properties of the HBPU‐G3/DGEBA thermosets were characterized and compared with that of the neat epoxy thermosets. Their impact fracture surfaces were investigated by scanning electron microscopy, and the results indicated that no phase separation occurred in the DGEBA/anhydride system after the introduction of HBPU, which was confirmed by dynamic mechanical analysis and thermogravimetric analysis. After addition of 10 wt % HBPU, the toughness of the modified thermosets was found to be significantly improved without sacrificing their processability and thermal and mechanical properties to a large extent. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40614.     

Blends of epoxy resin with amine‐terminated polyoxypropylene elastomer: Morphology and properties

A liquid diglycidyl ether of bisphenol A (DGEBA) epoxy resin is blended in various proportions with amine‐terminated polyoxypropylene (POPTA) and cured using an aliphatic diamine hardener. The degree of crosslinking is varied by altering the ratio of diamine to epoxy molecules in the blend. The mixture undergoes almost complete phase separation during cure, forming spherical elastomer particles at POPTA concentrations up to 20 wt %, and a more co‐continuous morphology at 25 wt %. In particulate blends, the highest toughness is achieved with nonstoichiometric amine‐to‐epoxy ratios, which produce low degrees of crosslinking in the resin phase. In these blends, the correlation between G_IC and plateau modulus (above the resin T_g), over a wide range of amine‐to‐epoxy ratios, confirms the importance of resin ductility in determining the fracture resistance of rubber‐modified thermosets. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 427–434, 1999     

Toughened cycloaliphatic epoxy resin for demanding thermal applications and surface coatings

An epoxy resin based on nonglycidyl ether and varying content of carboxyl‐terminated (poly)butadiene acrylonitrile copolymer was cured using an aromatic amine hardener. The ultimate aim of the study was to modify the brittle epoxy matrix by the liquid rubber to improve toughness characteristics. Fourier transform infrared spectroscopic analysis of the modified was performed to understand the structural transformations taking place during the uncured and cured stage of the modified systems. The decreasing trend in exothermal heat of reaction with increasing rubber content in the epoxy resin can be explained by the fact that the increase of carboxyl‐terminated butadiene acrylonitrile copolymer (CTBN) modifier might induce a high reactivity of the end groups with the epoxide ring and resulting shorter curing times and, hence, the faster curing process than the unmodified resin. Tensile strength, impact strength, and elongation‐at‐break behaviors of neat as well as modified networks have been studied to observe the effect of rubber modification. Blends sample exhibits better properties as compared to pure epoxy resin in terms of increase in impact strength and elongation‐at‐break of the casting and gloss, scratch hardness, adhesion, and flexibility of the film. The improvement in these properties indicate that the rubber‐modified resin would be more durable than the epoxy based on di glycidyl ether of bis‐phenol‐A and other epoxies. The films of coating based on epoxy with 15 wt % CTBN offered the maximum resistance toward different concentrations of acids, alkalies, and solvents as compared to the cured films of other blend samples. The thermal stability of the cycloaliphatic‐based epoxy resin was increased with the addition of 15 wt % CTBN in epoxy matrix. Cycloaliphatic‐based epoxy network modified with CTBN displayed two phase separated morphology with dispersed rubber globules in the matrix resin, i.e., they revealed the presence of two phase morphological features. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Comparison of thermoset soy protein resin toughening by natural rubber and epoxidized natural rubber

Fully bio‐based soy protein isolate (SPI) resins were toughened using natural rubber (NR) and epoxidized natural rubber (ENR). Resin compositions containing up to 30 wt % NR or ENR were prepared and characterized for their physical, chemical and mechanical properties. Crosslinking between SPI and ENR was confirmed using ¹H‐NMR and ATR‐FTIR. All SPI/NR resins exhibited two distinctive drops in their modulus at glass transition temperature (T_g ) and degradation temperature (T_d ) at around ?50 and 215 °C, corresponding to major segmental motions of NR and SPI, respectively. SPI/ENR resins showed similar T_g and T_d transitions at slightly higher temperatures. For SPI/ENR specimens the increase in ENR content from 0 to 30 wt % showed major increase in T_g from ?23 to 13 °C as a result of crosslinking between SPI and ENR. The increase in ENR content from 0 to 30 wt % increased the fracture toughness from 0.13 to 1.02 MPa with minimum loss of tensile properties. The results indicated that ENR was not only more effective in toughening SPI than NR but the tensile properties of SPI/ENR were also significantly higher than the corresponding compositions of SPI/NR. SPI/ENR green resin with higher toughness could be used as fully biodegradable thermoset resin in many applications including green composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44665.     

Influence of aliphatic amine epoxy hardener on the adhesive properties of blends of mono‐carboxyl‐terminated poly(2‐ethylhexyl acrylate‐co‐methyl methacrylate) with epoxy resin

The adhesive properties have been investigated in blends of mono‐carboxyl‐terminated poly(2‐ethylhexyl acrylate‐co‐methyl methacrylate) with diglycidyl ether of bisphenol A and three different aliphatic amine epoxy hardener. The adhesives properties are evaluated in steel alloy substrate using single‐lap shear test. The copolymers are initially miscible in the stoichiometric blends of epoxy resin and hardener at room temperature. Phase separation is noted in the course of the polymerization reaction. Different morphologies are obtained according to the amine epoxy hardener. The most effective adhesive for steel–steel joints in single‐lap shear test is the blends using 1‐(2‐aminoethyl)piperazine (AEP) as hardener. This system shows the biggest lap shear strength. However, the modified adhesives show a reduction in the mechanical resistance. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Epoxy modification with poly(vinyl acetate) and poly(vinyl butyral). I. Structure,thermal, and mechanical characteristics

Efficiency of the application of high strength heat resistant thermoplastics for improving fracture toughness and impact properties of epoxy resins motivated authors to try large‐scale production thermoplastics for the same purpose. Epoxy/anhydride systems were modified by up to 8 wt % poly(vinyl acetate) (PVAc) and up to 6 wt % poly(vinyl butyral) (PVB). In epoxy–PVAc blends it was possible to obtain morphologies with continuous thermoplastic phase. However, only sea‐island morphologies with a very small size of PVB‐rich phase were observed in epoxy–PVB matrices. The former type of morphology allowed a notable 2.4‐fold increase in the fracture toughness of epoxy resin and simultaneous up to 30% decrease in its' impact strength. The latter type of morphology caused a notably lower (45%) enhancement of the epoxy fracture toughness combined with a 50% increase in its' impact strength. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44081.     

Effect of different curing systems on heat shrinkability and mechanical properties of ethylene vinyl acetate/epoxidized natural rubber blends

Ethylene vinyl acetate (EVA)/epoxidized natural rubber (ENR) blends containing 10 and 30 wt % ENR were prepared by using an internal mixer. Five different types of curing systems were employed: dicumyl peroxide (DCP), sulfur (S), phenolic resin (Ph), DCP + S, and DCP + Ph. DCP could crosslink with both EVA and ENR while S and Ph were curing agents for ENR. The DCP system provided the lowest tensile properties and tear strength because of low crosslinking in ENR phase. Addition of sulfur or phenolic resin increased the mechanical properties due to a better vulcanization of the rubber phase. The mechanical properties of the blends decreased with increasing ENR content. The rubber particle size in the blends containing 30% ENR played a more important role in the mechanical properties than the blends containing 10% ENR. ENR particle size did not affect heat shrinkability of EVA and a well vulcanized rubber phase was not required for high heat shrinkage. Furthermore, heat shrinkage of the blends slightly changed as the ENR content increased for all curing systems. With regard to the mechanical properties and heat shrinkability, the most appropriate curing system was DCP + Ph and in the case the 10 wt % ENR content produced a more favorable blend. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermoplastic vulcanizates based on poly(methyl methacrylate)/epoxidized natural rubber blends: Mechanical,thermal, and morphological properties

Epoxidized natural rubbers (ENRs) with epoxide levels of 10, 20, 30, 40 and 50 mol % were prepared. The ENRs were later used to prepare thermoplastic vulcanizates (TPVs) by blending them with poly(methyl methacrylate) (PMMA) using various formulations. Dynamic vulcanization, using sulfur as a vulcanizing agent, was performed during the mixing process. The mixing torque increased as the ENR contents and epoxide molar percentage increased. This was because of an increasing chemical interaction between the polar groups of the blend components, particularly at the interface between the elastomeric and thermoplastic phases. The ultimate tensile strength of the TPVs with ENR‐20 was high because of strain‐induced crystallization. ENRs with epoxide levels >30 mol % exhibited an increase of tensile strength because of increasing levels of chemical interaction between the molecules and the different phases. The hardness of the TPVs also increased with increased epoxide levels but decreased with increased contents of ENRs. Two morphology phases with small domains of vulcanized ENR particles dispersed in the PMMA matrix were observed from scanning electron microscopy micrographs. The TPVs based on ENR‐20 and ENR‐50 showed smaller dispersed rubber domains than those of the other types of ENRs. Furthermore, the size of the vulcanized rubber domain decreased with increasing amounts of PMMA in the blends. The decomposition temperature of the TPVs also increased as both the levels of ENRs in the blends and the epoxide molar percentage increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1251–1261, 2005     

Epoxy resin containing the poly(sily ether): Preparation,morphology, and mechanical properties

The poly(sily ether) with pendant chloromethyl groups (PSE) was synthesized by the polyaddition of dichloromethylsilane (DCM) and diglycidylether of bisphenol A (DGEBA) with tetrabutylammonium chloride (TBAC) as a catalyst. This polymer was miscible with diglycidyl ether of bisphenol A (DGEBA), the precursor of epoxy resin. The miscibility is considered to be due mainly to entropy contribution because the molecular weight of DGEBA is quite low. The blends of epoxy resin with PSE were prepared through in situ curing reaction of diglycidyl ether of bisphenol A (DGEBA) and 4,4′‐diaminodiphenylmethane (DDM) in the presence of PSE. The DDM‐cured epoxy resin/PSE blends with PSE content up to 40 wt % were obtained. The reaction started from the initial homogeneous ternary mixture of DGEBA/DDM/PSE. With curing proceeding, phase separation induced by polymerization occurred. PSE was immiscible with the 4,4′‐diaminodiphenylmethane‐cured epoxy resin (ER) because the blends exhibited two separate glass transition temperatures (T_gs) as revealed by the means of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). SEM showed that all the ER/PSE blends are heterogeneous. Depending on blend composition, the blends can display PSE‐ or epoxy‐dispersed morphologies, respectively. The mechanical test showed that the DDM‐cured ER/PSE blend containing 25 wt % PSE displayed a substantial improvement in Izod impact strength, i.e., epoxy resin was significantly toughened. The improvement in impact toughness corresponded to the formation of PSE‐dispersed phase structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 505–512, 2003     

Preparation and properties of high performance phthalide‐containing bismaleimide modified epoxy matrices

A series of intercrosslinked networks formed by diglycidyl ether of bisphenol A epoxy resin (DGEBA) and novel bismaleimide containing phthalide cardo structure (BMIPP), with 4,4′‐diamino diphenyl sulfone (DDS) as hardener, have been investigated in detail. The curing behavior, thermal, mechanical and physical properties and compatibility of the blends were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), notched Izod impact test, scanning electron microscopy (SEM) and water absorption test. DSC investigations showed that the exothermic transition temperature (T_p) of the blend systems shifted slightly to the higher temperature with increasing BMIPP content and there appeared a shoulder on the high‐temperature side of the exothermic peak when BMIPP content was above 15 wt %. TGA and DMA results indicated that the introduction of BMIPP into epoxy resin improved the thermal stability and the storage modulus (G′) in the glassy region while glass transition temperature (T_g) decreased. Compared with the unmodified epoxy resin, there was a moderate increase in the fracture toughness for modified resins and the blend containing 5 wt % of BMIPP had the maximum of impact strength. SEM suggested the formation of homogeneous networks and rougher fracture surface with an increase in BMIPP content. In addition, the equilibrium water uptake of the modified resins was reduced as BMIPP content increased. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Toughening of an epoxy resin with hydroxy‐terminated poly(arylene ether nitrile) with pendent tertiary butyl groups

Hydroxy‐terminated poly(arylene ether nitrile) oligomers with pendent tert‐butyl groups (PENTOH) were synthesized by the nucleophilic aromatic substitution reaction of 2,6‐dichlorobenzonitrile with tert‐butyl hydroquinone in N‐methyl‐2‐pyrrolidone medium with anhydrous potassium carbonate as a catalyst at 200°C in a nitrogen atmosphere. The PENTOH oligomers were blended with diglycidyl ether of bisphenol A epoxy resin and cured with 4,4′‐diaminodiphenyl sulfone. The curing reaction was monitored with infrared spectroscopy and differential scanning calorimetry. The morphology, fracture toughness, and thermomechanical properties of the blends were investigated. The scanning electron micrographs revealed a two‐phase morphology with a particulate structure of the PENTOH phase dispersed in the epoxy matrix, except for the epoxy resin modified with PENTOH with a number‐average molecular weight of approximately 4000. The storage modulus of the blends was higher than that of the neat epoxy resin. The crosslink density calculated from the storage modulus in the rubbery plateau region decreased with an increase in PENTOH in the blends. The fracture toughness increased more than twofold with the addition of PENTOH oligomers. The tensile strength of the blends increased marginally, whereas the flexural strength decreased marginally. The dispersed PENTOH initiated several toughening mechanisms, which improved the fracture toughness of the blends. The thermal stability of the epoxy resin was not affected by the addition of PENTOH to the epoxy resin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Improving the toughness of epoxy with a reactive tetrablock copolymer containing maleic anhydride

Reactive block copolymers (BCPs) provide a unique means for toughening epoxy thermosets because covalent linkages provide opportunities for greater improvement in the fracture toughness (K_IC). In this study, a tailored reactive tetrablock copolymer, poly[styrene‐alt‐(maleic anhydride)]‐block‐polystyrene‐block‐poly(n‐butyl acrylate)‐block‐polystyrene, was incorporated into a diglycidyl ether of bisphenol A based epoxy resin. The results demonstrate the advantage of reactive BCP in finely tuning and controlling the structure of epoxy blends, even with 95 wt % epoxy‐immiscible triblocks. The size of the dispersed phase was efficiently reduced to submicrometer level. The mechanical properties, such as K_IC, of these cured blends were investigated. The addition of 10 wt % reactive BCP into the epoxy resins led to considerable improvements in the toughness, imparting nearly a 70% increase in K_IC. The designed reactive tetrablock copolymer opened good prospects because of its potential novel applications in toughening modification of engineering polymer composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42826.     

Toughening of cycloaliphatic epoxy resins by poly(ethylene phthalate) and related copolyesters

Poly(ethylene phthalate) (PEP) and poly(ethylene phthalate–co‐ethylene terephthalate) were used to improve the brittleness of the cycloaliphatic epoxy resin 3,4‐epoxycyclohexylmethyl 3,4‐epoxycyclohexane carboxylate (Celoxide 2021?), cured with methyl hexahydrophthalic anhydride. The aromatic polyesters used were soluble in the epoxy resin without solvents and effective as modifiers for toughening the cured epoxy resin. For example, the inclusion of 20 wt % PEP (MW, 7400) led to a 130% increase in the fracture toughness (K_IC) of the cured resin with no loss of mechanical and thermal properties. The toughening mechanism is discussed in terms of the morphological and dynamic viscoelastic behaviors of the modified epoxy resin system. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 388–399, 2002; DOI 10.1002/app.10363     

Preparation and properties of dynamically cured PP/MAH‐g‐EVA/epoxy blends

A method concerning with the simultaneous reinforcing and toughening of polypropylene (PP) was reported. Dynamical cure of the epoxy resin with 2‐ethylene‐4‐methane‐imidazole (EMI‐2,4) was successfully applied in the PP/maleic anhydride‐grafted ethylene‐vinyl acetate copolymer (MAH‐g‐EVA), and the obtained blends named as dynamically cured PP/MAH‐g‐EVA/epoxy blends. The stiffness and toughness of the blends are in a good balance, and the smaller size of epoxy particle in the PP/MAH‐g‐EVA/epoxy blends shows that MAH‐g‐EVA was also used as a compatibilizer. The structure of the dynamically cured PP/MAH‐g‐EVA/epoxy blends is the embedding of the epoxy particles by the MAH‐g‐EVA. The cured epoxy particles as organic filler increases the stiffness of the PP/MAH‐g‐EVA blends, and the improvement in the toughness is attributed to the embedded structure. The tensile strength and flexural modulus of the blends increase with increasing the epoxy resin content, and the impact strength reaches a maximum of 258 J/m at the epoxy resin content of 10 wt %. DSC analysis shows that the epoxy particles in the dynamically cured PP/MAH‐g‐EVA/epoxy blends could have contained embedded MAH‐g‐EVA, decreasing the nucleating effect of the epoxy resin. Thermogravimetric results show the addition of epoxy resin could improve the thermal stability of PP, the dynamically cured PP/MAH‐g‐EVA/epoxy stability compared with the pure PP. Wide‐angle x‐ray diffraction analysis shows that the dynamical cure and compatibilization do not disturb the crystalline structure of PP in the blends. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Studies on polyamide‐6/polyolefin blend system compatibilized with epoxidized natural rubber

Infrared spectra of polyamide‐6 (PA6) with and without epoxidized natural rubber (ENR) are presented. The influence of ENR used as a compatibilizer on the morphologies, crystallizability, mechanical properties, and thermal behavior of the polyamide‐6/polyolefins (PO) blends are studied. The infrared spectra suggest that under normal processing conditions, the carboxyl end groups of PA6 could chemically react in situ with the epoxy groups of ENR, and ester groups are created. This means that the PA6‐ENR grafting copolymer could be obtained during processing. All the morphological characterizations and thermal analyses show that the compatibility of PA6/PO blends is obviously improved by ENR because the copolymer increases the interaction between PA6 and PO. It is also found that the toughness of PA6/PO blends increase significantly after using ENR, while the tensile strength and the softening temperature of PA6/PO blends have almost no change. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 398–403, 2003     

The Curing Behavior and Adhesion Strength of the Epoxidized Natural Rubber Modified Epoxy/Dicyandiamide System

The curing properties and adhesive strengths of the epoxidized natural rubber (ENR, 25 mole percent epoxidation) modified epoxy systems are studied with differential thermal calorimetry (DSC), scanning electron microscopy (SEM), and lap shear strength (LSS) measurement. The results of DSC analyses indicate that the curing exotherm, the curing rate, the reaction order, and the glass transition temperature of the epoxy system are affected by the presence of reactive ENR. From SEM micrographs, it is obtained that a second spherical rubber phase is formed during cure and the particle size of the rubber phase is increased by increasing the curing temperature and the ENR content. The changes of the volume fraction of the rubber phase and the T_g of the cured systems indicate that the mutual dissolution between epoxy resin and ENR happens and which changes with the curing temperature and the ENR content. The LSS of adhesive joints prepared with the ENR modified adhesives are all lower than those of the unmodified epoxy system, and decrease with increasing the amount of ENR added because of the limited compatibility of the ENR with the epoxy matrix.     

Modification of epoxy resin by polysulfone to improve the interfacial and mechanical properties in glass fibre composites. I. Study of processes during matrix/glass fibre interface formation

The rheology of epoxy resin-polysulfone blends and wetting at the blend/glass fibre interface have been studied. Measurements were made in a rotary viscometer and in a modified Wilhelmy apparatus. It was shown that none of the blends investigated revealed non-Newtonian behaviour in the range of shear rates used. The viscosity of the blends increased as polysulfone content increased. Introduction of hardener resulted in a significant increase of the blends viscosity up to 2-3 orders of magnitude. Rheological tests suggested that 15 wt% polysulfone was the highest concentration useful for obtaining composites by solvent-free impregnation technique. These tests suggested that the structure of the cured epoxy-polysulfone blends depended on the modifier concentration. The structures of the blends differed for the blends containing 5 wt% polysulfone and 10-15 wt% polysulfone. All the blends (with the hardener) required at least 30 min at 180°C to achieve final values of the mechanical properties such as storage and loss moduli, loss tangent and complex viscosity. For all epoxy resin-polysulfone/glass fibre systems a complete wetting of the fibres was observed. Surface tension vs. polysulfone content dependency was found to be nonadditive. Surface tension measured was minimal for epoxy resin-5% polysulfone blend, while for other systems the values were close to that of epoxy resin. Modification of epoxy resin by polysulfone did not change the kinetics of the fibres wetting by 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.