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.     

Effect of carbon black on self‐crosslinking network structure of polychloroprene rubber and epoxidized natural rubber blends

The goal of this research is to improve poor network structure of polychloroprene rubber (CR)/epoxidized natural rubber (ENR) self‐crosslinking blends, which could substitute traditional vulcanizates in some application area. Carbon black (CB)–CR/ENR blends were prepared by reacting CR with ENR in the presence of CB. The structure of CR/ENR blends was characterized by attenuated total‐reflectance Fourier transform infrared spectroscopy (FTIR‐ATR). The effect of CB loading on curing characterization and mechanical properties of CR/ENR blends was investigated, and the interaction among CR, ENR, and CB was studied using differential scanning calorimetry. The effect of CB loading on the Payne effect of CR/ENR was investigated using rubber process analyzer. Scanning electron microscope was used to characterize the morphology of CB–CR/ENR blends. The results showed that CR/ENR blends were obtained by the ring‐opening reaction of epoxy groups in ENR and chlorine groups in CR. Mechanical properties of CR/ENR blends increased with the increase of CB loading. The Payne effect of CR/ENR became more remarkable with increasing CB loading. Morphology study indicated that interfacial compatibility between CR and ENR increased with the increase of CB loading because CB could strengthen the self‐crosslinking network structure of CR/ENR blends. The promoting effect of CB on self‐crosslinking reaction was verified by the assessment of crosslink density. POLYM. COMPOS., 38:463–471, 2017. © 2015 Society of Plastics Engineers     

Toughness enhancement of poly(lactic acid) by melt blending with natural rubber

Rubber toughened poly(lactic acid) (PLA) was prepared by blending with natural rubber (NR)‐based polymers. The blends contained 10 wt % of rubber and melt blended with a twin screw extruder. Enhancement of impact strength of PLA was primarily concernced. This study was focused on the effect of rubber polarity, rubber viscosity and molecular weight on mechanical properties of the blends. Three types of rubbers were used: NR, epoxidized natural rubber (ENR25 and ENR50), and natural rubber grafted with poly(methyl methacrylate) (NR‐g‐PMMA). Effect of viscosity and molecular weight of NR, rubber mastication with a two‐roll mill was investigated. It was found that all blends showed higher impact strength than PLA and NR became the best toughening agent. Viscosity and molecular weight of NR decreased with increasing number of mastication. Impact strength of PLA/NR blends increased after applying NR mastication due to appropriate particle size. DMTA and DSC characterization were determined as well. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermoplastic natural rubber based on polyamide‐12: Influence of blending technique and type of rubber on temperature scanning stress relaxation and other related properties

Thermoplastic natural rubber based on polyamide‐12 (PA‐12) blend was prepared by melt blending technique. Influence of blending techniques (i.e., simple blend and dynamic vulcanization) and types of natural rubber (i.e., unmodified natural rubber (NR) and epoxidized natural rubber (ENR)) on properties of the blends were investigated. It was found that the simple blends with the proportion of rubber ～ 60 wt % exhibited cocontinuous phase structure while the dynamically cured blends showed dispersed morphology. Furthermore, the blend of ENR exhibited superior mechanical properties, stress relaxation behavior, and fine grain morphology than those of the blend of the unmodified NR. This is attributed to chemical interaction between oxirane groups in ENR molecules and polar functional groups in PA‐12 molecules which caused higher interfacial adhesion. It was also found that the dynamic vulcanization caused enhancement of strength and hardness properties. Temperature scanning stress relaxation measurement revealed improvement of stress relaxation properties and thermal resistance of the dynamically cured ENR/PA‐12 blend. This is attributed to synergistic effects of dynamic vulcanization of ENR and chemical reaction of the ENR and PA‐12 molecules. Furthermore, the dynamically cured ENR/PA‐12 blend exhibited smaller rubber particles dispersed in the PA‐12 matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Characterization of epoxidized natural rubber/ethylene vinyl acetate (ENR‐50/EVA) blend: Effect of blend ratio

Epoxidized natural rubber/Ethylene vinyl acetate copolymer (ENR‐50/EVA) blends with different ratios were prepared by using a Haake internal mixer. The effect of the blend ratio on the processing, tensile properties (such as tensile strength, elongation at break, Young's modulus and stress–strain behavior), morphology, dynamic mechanical properties, and thermal properties has been investigated. The tensile properties increase with the increase of EVA content, whereas the stabilization torque increases with the increase of ENR‐50 content in the blend. In 40:60 and 50:50 blend of ENR‐50/EVA, both the phases exist as continuous phases, producing a co‐continuous morphology. At these blend ratio, the drastic change in properties were noted, indicating that the phase inversion occurs. The results on dynamic mechanical properties revealed that the blends are compatible. Blending of ENR‐50 and EVA lead to the improvement in thermal stability and 50:50 blend ratios is the most stable blend. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1504–1515, 2006     

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     

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.     

One‐step latex compounding method for producing composites of natural rubber/epoxidized natural rubber/aminosilane‐functionalized montmorillonite: enhancement of tensile strength and oil resistance

Montmorillonite (Mt) was intercalated with cetyltrimethylammonium bromide and functionalized with three types of aminosilane (3‐aminopropyltrimethoxysilane, n‐(2‐aminoethyl)‐3‐aminopropyltrimethoxysilane and 3‐[2‐(2‐aminoethylamino)ethylamino]propyltrimethoxysilane). The modified Mt was compounded with natural rubber (NR)/epoxidized natural rubber (ENR) via one‐step latex compounding. The effect of the modified Mt content on the oil resistance and mechanical properties of the NR/ENR/modified Mt composites was investigated. The X‐ray diffraction patterns of the composites showed partial intercalation/exfoliation of the modified Mt in the rubber matrix. Cryogenic fracture and X‐ray fluorescence results revealed highly dispersed modified Mt in the composites in the presence of 10 phr ENR. All three aminosilane groups slightly improved the oil resistance, with the long‐alkyl‐length group producing the greatest improvement. The addition of a small amount of modified Mt improved both oil resistance and tensile strength by increasing in the average diffusion path length in the NR matrix and enhancing the interaction between the modified Mt and the epoxide groups in ENR. The addition of 1.0 phr of modified Mt increased the tensile strength by 18% and decreased the elongation at break by 12% compared with a neat NR/ENR blend. © 2017 Society of Chemical Industry     

Modification of epoxidized natural rubber as a PLA toughening agent

In the present study, the modification of epoxidized natural rubber (ENR) was investigated to improve toughness of PLA. ENR-PLA copolymers were synthesized by 2 steps reactions. Acid hydrolysis of ENR to prepare macroinitiator (ENR-OH) and copolymerization with lactide to obtain ENR-PLA copolymers. The reaction time of acid hydrolysis and the lactide monomer loading was investigated. The optimum conditions were 8 h acid hydrolysis with 5wt% lactide loading to obtain ENR8-PLA5 copolymers. A series of samples of PLA blended with ENR-PLA copolymers was prepared using melt-blending. The blend of PLA with ENR8-PLA5 copolymers at 1 phr substantially improved the tensile properties. The elongation at break was increased 67%, and toughness was increased 64% compared to neat PLA. These results indicate that ENR8-PLA5 has potential as toughening agent for PLA. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48267.     

Self-vulcanizable rubber blend systems based on epoxidized natural rubber and chlorosulfonated polyethylene: Effect of blend composition,epoxy content of epoxidized natural rubber,and reinforcing black filler on physical properties

Mill mixed blend of epoxidized natural rubber and chlorosulfonated polyethylene forms a self-vulcanizable rubber blend during molding at high temperatures in absence of any vulcanizing agent, which is confirmed by FTIR studies. The extent of vulcanization reaction not only depends upon time and temperature of molding but also on the level of epoxidation in ENR and its proportion present in the blend. Physical properties of the blends are comparable to that of conventional rubber vulcanizates. Such blends can be reinforced by carbon black filler.     

Effects of epoxidized natural rubber (ENR‐50) and processing parameters on the properties of NR/EPDM blends using response surface methodology

The effects of epoxidized natural rubber (ENR‐50) and processing parameters on the properties of natural rubber/ethylene–propylene–diene rubber (NR/EPDM; 70 : 30 phr) blends were studied. The compounds were prepared by melt compounding method. Using response surface methodology of two‐level full factorial, the effects of ENR‐50 contents (?1 : 5 phr; +1 : 10 phr), mixing temperature (?1 : 50°C; +1 : 110°C), rotor speed (?1 : 40 rpm; +1 : 80 rpm), and mixing time (?1 : 5 min; +1 : 9 min) in NR/EPDM blends were evaluated. Cure characteristics and tensile properties were selected as the responses. The significance of factors and its interaction was analyzed using ANOVA and the model's ability to represent the system was confirmed using the constant of determination, R² with values above 0.90. It was found that the presence of ENR‐50 has the predominant role on the properties of NR/EPDM blends. The addition of ENR‐50 significantly improved cure characteristics and tensile strength up to 5.12% and 6.48% compared to neat NR/EPDM blends, respectively. These findings were further supported by swell measurement, differential scanning calorimetry, and scanning electron microscopy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40713.     

Aspects of miscibility in poly(vinyl chloride)/epoxidized natural rubber blends. Part I: Mechanical and morphological properties

Miscibility in poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blends was studied by examining evidence from tensile, impact, and physical properties. The observation of synergism in tensile strength, percent elongation at break, hardness, and relative density has reaffirmed PVC/ENR blends as miscible systems. Studies of impact properties, however, revealed that the blends are microheterogeneous in nature. This could be attributed to the large sizes of polymer molecules involved and the microgel content of ENR-50. Results from Fourier transform infrared spectroscopy (FTIR) revealed that hydrogen bonding is extensively involved in PVC/ENR systems. This evidence unveiled the exact nature of the specific interactions responsible for miscibility and hence the enhanced mechanical properties of PVC/ENR blends.     

Mechanical properties and blend compatibility of natural rubber –chlorosulfonated polyethylene blends

Natural rubber (NR) was blended with chlorosulfonated polyethylene (CSM) with various formulation and blend ratios (NR/CSM: 80/20 –20/80, wt/wt). Rubber blends were prepared by using a two‐roll mill and vulcanized in a compression mold to obtain the 2 mm‐thick sheets. Tensile properties, tear resistance, thermal aging resistance, ozone resistance, and oil resistance were determined according to ASTM. Compatible NR/CSM blends are derived from certain blends containing 20–30% CSM without adding any compatibilizing agent. Tensile and tear strength of NR‐rich blends for certain formulations show positive deviation from the rule of mixture. Thermal aging resistance depends on formulation and blend ratio, while ozone and oil resistance of the blends increase with CSM content. Homogenizing agents used were Stuktol®60NS and Epoxyprene®25. Stuktol®60NS tends to decrease the mechanical properties of the blends and shows no significant effect on blend morphology. Addition of 5–10 phr of epoxidized natural rubber (ENR, Epoxyprene® 25) increases tensile strength, thermal aging resistance, and ozone resistance of the blends. It is found that ENR acts as a compatibilizer of the NR/CSM blends by decreasing both CSM particle size diameter and α transition temperature of CSM. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 127–140, 2006     

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.     

Self‐crosslinkable lignin/epoxidized natural rubber composites

Self‐crosslinkable lignin/epoxidized natural rubber composites (SLEs) were prepared through a high‐temperature dynamic heat treatment procedure followed by a postcuring process. Because of the ring‐opening reaction between lignin and epoxidized natural rubber (ENR), lignin as a crosslinker and reinforcing filler was uniformly dispersed into the ENR matrix and was highly compatible with the polymer matrix; this was confirmed by scanning electron microscopy. The curing behavior, mechanical properties, and dynamic mechanical properties of the SLEs were studied. The results show that the crosslinking degree, glass‐transition temperature, modulus, and tensile properties of the SLEs substantially increased with the addition of lignin. A physical model was used to verify the strong interactions between lignin and ENR. Stress–strain curves and X‐ray diffraction suggested that the reinforcement effect on the SLEs mainly originated from lignin itself rather than from strain‐induced crystallization. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41166.     

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     

Thermal and mechanical properties of epoxidized natural rubber modified epoxy matrices

Two sets (A and B) of bisphenol A–diglycidyl ether (DGEBA) based epoxy resin formulations were modified with epoxidized natural rubber (ENR 50) and its liquid version (LENR 50), and cured with amino propoxylate initiator/accelerator at ambient temperatures. The ENR 50 loading range was 1.6–5.9 wt%. Both sets could be loaded up to 12 wt% with LENR 50. Significant improvements in tensile toughness and impact toughness could only be observed for set A formulations. At the maximum LENR 50 loading achieved, the improvement in tensile toughness is 250% in comparison with that of the neat formulation; that for impact toughness is 125%. Differential scanning calorimetry reveals multiple transitions, characteristic of these systems. Scanning electron micrographs of fractured surfaces show uniform rubber dispersions in the submicrometre size range. At the loading levels used, LENR 50 particle dispersions fall within the range of 0.33–0.47 µm in size; those of ENR 50 are 0.48–0.67 µm in average size. Improvements in toughness are similar for both versions of epoxidized natural rubber. For both LENR 50 and ENR 50 modified epoxy systems, the extremes of 0.80 (set A) and 1.95 (set B) in glycidyl ether/reactive hydrogen molar ratios considered show distinct failure mechanisms, that of ductile failure with yielding in the former and brittle failure in the latter, irrespective of reactive diluent content. © 1999 Society of Chemical Industry     

Novel ternary blends of natural rubber/linear low-density polyethylene/thermoplastic starch: influence of epoxide level of epoxidized natural rubber on blend properties

Novel degradable materials based on ternary blends of natural rubber (NR)/linear low-density polyethylene (LLDPE)/thermoplastic starch (TPS) were prepared via simple blending technique using three different types of natural rubber (i.e., unmodified natural rubber (RSS#3) and ENR with 25 and 50 mol% epoxide). The evolution of co-continuous phase morphology was first clarified for 50/50: NR/LLDPE blend. Then, 10 wt% of TPS was added to form 50/40/10: NR/LLDPE/TPS ternary blend, where TPS was the particulate dispersed phase in the NR/LLDPE matrix. The smallest TPS particles were observed in the ENR-50/LLDPE blend. This might be attributed to the chemical interactions of polar functional groups in ENR and TPS that enhanced their interfacial adhesion. We found that ternary blend of ENR-50/LLDPE/TPS exhibited higher 100 % modulus, tensile strength, hardness, storage modulus, complex viscosity and thermal properties compared with those of ENR-25/LLDPE/TPS and RSS#3/LLDPE/TPS ternary blends. Furthermore, lower melting temperature (T _m) and heat of crystallization of LLDPE (?H) were observed in ternary blend of ENR-50/LLDPE/TPS compared to the other ternary blends. Also, neat TPS exhibited the fastest biodegradation by weight loss during burial in soil for 2 or 6 months, while the ternary blends of NR/LLDPE/TPS exhibited higher weight loss compared to the neat NR and LLDPE. The lower weight loss of the ternary blends with ENR was likely due to the stronger chemical interfacial interactions. This proved that the blend with ENR had lower biodegradability than the blend with unmodified NR.     

Effect of epoxidized natural rubber on the processing behavior,tensile properties,morphology, and thermal properties of linear‐low‐density polyethylene/soya powder blends

The effect of epoxidized natural rubber (ENR) with 50 mol% epoxidation (ENR 50) on the processing behaviors, tensile properties, morphology, and thermal properties of linear‐low‐density polyethylene (LLDPE)/soya powder blends was investigated. The LLDPE was blended with various soya powder contents in a Haake internal mixer at 150°C and a rotor speed of 50 rpm for 10 min. The tensile properties were tested by using an Instron tensometer according to ISO 527. The thermal stability of the blends was determined by using a thermogravimetric analyzer (TGA). The tensile strength and elongation at the breakage point were significantly improved by the addition of ENR 50, as evidenced by morphological analysis using scanning electron microscopy (SEM). On the other hand, the tensile modulus increased with soya powder content up to 20% and decreased thereafter. The crystallinity and crystallization temperatures of the blends decreased with the incorporation of ENR, and the thermal stability of the blends was lower with higher soya powder content. However, ENR 50 improved the thermal stability of LLDPE/soya powder blends. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

The effect of polylactic acid (PLA)/poly‐d‐lactide stereocomplex on the thermal and mechanical properties of various PLA/rubber blends

This study investigated the effect of polylactic acid (PLA)/poly‐d ‐lactide (PDLA) stereocomplex (ST) on the improvement of the mechanical and thermal properties of various rubber‐toughened PLAs. In this work, natural rubber (NR), synthetic polyisoprene rubber (IR), silicone rubber (SI), acrylic rubber (ACM), acrylic core–shell rubber (CSR), thermoplastic copolyester (TPE) and thermoplastic polyurethane (TPU) were chosen as the toughening agents. 5 wt% PDLA was melt‐blended with PLA to form ST crystals in the presence of 15 wt% rubber in an internal mixer at 180 °C and 50 rpm. It was found that the melting temperature of ST crystal (T_m,sc) and the impact strength of ST/rubber blends were strongly correlated with the rubber domain size. For the blends of ST with compatible rubbers (ACM, CSR, TPE and TPU), the rubber domain sizes tended to be smaller with higher T_m,sc and higher impact strength than the blends with incompatible rubbers (NR, IR and SI). However, the presence of ST crystals in PLA/incompatible rubber blends, especially the blends with NR and IR, led to a significant increase in the rubber domain size and plunges in tensile toughness and impact strength. On the other hand, the presence of these crystals in PLA/compatible blends did not change the rubber size or the impact strength significantly compared with those without ST crystals except in the case of ST/ACM, which resulted in a large increase in the impact strength. Among all rubber types, CSR provided the highest impact strength for both the PLA and ST systems. © 2019 Society of Chemical Industry