Liquid Epoxidized Natural Rubber Research Articles

Enhancing flexibility and durability of PVC with liquid epoxidized natural rubber: Innovative UV treatment to mitigate plasticizer migration

AbstractThis manuscript elucidates the preparation and utilization of liquid epoxidized natural rubber (LENR) with 50 mol% epoxidation level (LENR50) as a polymeric plasticizer for poly(vinyl chloride) (PVC), and further immobilization of the plasticizer in the plastic matrix through subsequent ultraviolet (UV)‐curing treatment. The plasticizing effect induced by LENR50 at 50 wt% loading was evident with a reduction of Tg from a high of 72.0 to 11.4°C. Positive enhancements were also documented in the mechanical properties of the LENR50‐plasticized PVC, specifically the big improvement in elongation at break and elastic modulus, from 106% to 430%, and from 646 to 7 MPa, respectively. The UV‐treated PVC/LENR film also exhibited superior resistance to migration compared with formulations with conventional plasticizers such as di‐2‐ethylhexyl phthalate (DEHP) and triethyl‐2‐acetyl citrate (ATEC). A similar outcome was recorded in the leaching resistance test, where LENR50 had the best resistance to leaching in four different solvents (water, soap solution, ethanol, and toluene). The LENR50‐plasticized PVC film recorded the lowest weight loss following 24 h immersion in both hydrophilic and lipophilic solvents. The findings from this study suggest that LENR50 could serve as an efficient bio‐based polymeric plasticizer for PVC.Highlights LENR as bio‐based polymeric plasticizer for PVC. Significant reduction in Tg and elastic modulus of PVC plasticized with LENR. UV treatment improved tensile strength and elongation at break of LENR/PVC film. UV‐treated PVC/LENR has superior plasticizer migration and leaching resistance.

Utilization of liquid epoxidized natural rubber as prepolymer and crosslinker in development of UV-curable palm oil-based alkyd coating

Innovation of new products from renewable resources are important for sustainable development. In this work, novel rubber-integrated palm oil-based alkyd resins were prepared using palm oil, glycerol, diacids, and liquid epoxidized natural rubber (LENR50). The synthesis started with alcoholysis of glycerol by palm oil to produce predominant mixture of monoglycerides, followed by polycondensation with diacids to form alkyd chain. In addition to glycerol, LENR50 was introduced as bio-based polyol for the alkyd synthesis. The rubber prepolymer was chemically integrated into the alkyd chain via the reaction between its epoxide or hydroxyl groups with COOH of diacids during polycondensation. Resultant alkyds were mixed with reactive diluent (styrene), crosslinker (trimethylolpropane triacrylate) and photoinitiators (benzophenone and 1-hydroxycyclohexyl phenyl ketone), and the mixtures were cured under UV irradiation. Introduction of LENR50 into the coating formulation has reduced the curing time, as well as improved some of the film properties of the coatings. Some of the LENR50-based coatings required as short as 3 mins of UV irradiation to form dry-hard films, while the control samples required much longer time. There was also notable increase in the gel content of the LENR-based alkyd coating, suggesting that the polyfunctionality of LENR50 could have increased the extent of crosslinking in the cured film. Other improvement recorded includes pencil hardness, film adhesion, solvent resistance, water resistance, and corrosion resistance. Thermal stability of the alkyd coatings is also reasonably good for general purpose coating applications. The findings from this study suggest that LENR50 could serve as an alternative polyol in synthesis of bio-based polyester binder for surface coating.

Facile synthesis of nickel-based supported halloysite nanotube catalysts and their role in photocatalytic degradation of liquid epoxidized natural rubber

Facile synthesis of nickel-based supported halloysite nanotube catalysts and their role in photocatalytic degradation of liquid epoxidized natural rubber

Effect of Carbon Nanofibers on Physical, Adhesion and Rheological Properties of Liquid Epoxidized Natural Rubber Modified Asphalt

This study aimed to evaluate the effects of carbon nanofibers (CNFs) on the performance of liquid epoxidized natural rubber (LENR)-modified asphalt. The physical, adhesion and rheological properties were determined by several tests such as penetration, elastic recovery, ring and ball softening point, Brookfield rotational viscometer, AFM and dynamic shear rheometer. LENR was used at concentrations of 3, 6, and 9%, while CNFs were used at contents of 0.3, 0.4, and 0.5% by weight of asphalt. Conventional test results showed that the increases in LENR and LENR/CNFs composite contents in binder leads to an increase in the hardness and consistency and a reduction in the temperature susceptibility of base asphalt. Adhesion results revealed that the addition of CNFs significantly increases the adhesion and bonding properties of base and rubberized binders. Rheological properties analysis exhibited that LENR improved the viscoelastic properties and permanent deformation resistance of asphalt at different temperatures and frequencies. On the other hand, it was found that the addition of CNFs significantly improves the stiffness, elasticity, and hardness of LENR-modified binders. The 6% LENR and 0.4% CNFs were found to be the optimum to enhance the physical, adhesion, and rheological properties of asphalt in this study. Thus, it can be stated that the addition of CNFs is promising to improve the performance of rubberized binders for high temperature applications.

Physical, mechanical and environmental stress cracking characteristics of epoxy/glass fiber composites: Effect of matrix/fiber modification and fiber loading

Modified epoxy composites reinforced with various glass fiber contents up to 12 wt% were prepared by a simple fabrication method which involved mechanical stirring, hot pressing and post-curing. The effects of matrix modification with liquid epoxidized natural rubber (LENR) and fiber treatment with silane coupling agent on the physical, mechanical and dynamic thermal properties were examined. The modified epoxy composites had reduced density, water resistance and hardness. When compared to untreated glass fiber, the epoxy/LENR composites containing treated fiber exhibited improved water resistance and hardness property with comparable composite density. At 9 wt% of treated fiber, it revealed the highest hardness value of 65.6 and reduced diffusion coefficient of 2.2013 × 10−7 mm2s−1. The excellent storage modulus and interfacial adhesion (lower Tan δ) were obtained for treated glass fiber composites. Based on environmental stress cracking resistance evaluation under corrosive mediums, the fiber treatment had positively contributed to the degradation mechanism.

Mechanical and thermal properties of polylactic acid/liquid epoxidized natural rubber blends

Polylactic acid (PLA) is a potential polymer to be used in various applications due to biodegradable and biocompatible characteristics. However, its brittle nature limits the usage of PLA. In order to improve the brittleness of PLA, liquid epoxidized natural rubber (LENR) was incorporated with PLA. The objective of this study is to investigate the effect of LENR as toughening agent on rigid PLA matrix in term of mechanical and thermal properties. Polylactic acid/liquid epoxidized natural rubber (PLA/LENR) blends were prepared by melt blending method using Brabender internal mixer with temperature 160 ?, mixing speed of 60 rpm and molded into test samples by compression molding. The LENR content was varied from 0, 5, 10, 15 and 20 wt%. It was found that the addition of LENR increased the impact strength of PLA.10 wt% of LENR showed the optimum impact strength which was 86.05 J/m. However, tensile strength and tensile modulus decreased slightly with increasing of LENR content. The morphology of PLA/LENR blends showed a good dispersion of LENR on PLA matrix at 10 wt% LENR. The differential scanning calorimeter (DSC) showed a gradual drop in melting temperature (Tm) as well as glass transition temperature (Tg) as LENR content increased.

The Characterization of Hydroxyl Terminated Epoxidized Natural Rubber (HTENR) via Oxidation Degradation Method

The degradation of epoxidized natural rubber (ENR-50) and liquid epoxidized natural rubber (LENR) was done via oxidative degradation method for the production of hydroxyl terminated epoxidized natural rubber (HTENR) and hydroxyl terminated liquid epoxidized natural rubber (HTLENR) has been analysed. Cobalt (II) acetylacetonate (CAA) were used as an oxidizing agent for chain scission reaction at temperature 60 °C in the presence of ethanol. The reaction temperature was fixed at 60 °C meanwhile reaction time and the amount of CAA were varied according to the reaction formulation. The HTENR and HTLENR obtained have been characterized using Gel Permeation Chromatography (GPC), Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR). GPC were used to determine the molecular weight before and after the oxidative degradation of respected HTENR and HTLENR were compared with ENR-50 and LENR. The lowest Mn and Mw of HTLENR that were obtained from the oxidative degradation method were found to be 5,163 g/mol and 58,087 g/mol. The appearances of OH end groups were verified by FTIR and NMR analyses to validate the position of each OH functional groups. FTIR analysis confirmed that HTENR and HTLENR contained OH group with the appearance of a broad peak around 3,400 cm-1 to 3,550 cm-1 after the reaction. The presence of OH end groups was verified by NMR analysis with the appearance at 3.39 ppm and 3.66 ppm, corresponding to methylene proton adjacent to hydroxyl group in HOCH2CH2CH2 and methane proton adjacent to OH group in CH2CH2CH(OH)CH3.

Preparation and characterization of hydroxyl terminated liquid epoxidized natural rubber

Hydroxyl terminated liquid epoxidized natural rubber (HTLENR) was successfully synthesized via oxidative degradation of liquid epoxidized natural rubber (LENR) in the presence of cobalt (II) acetyl acetonate (CAA) as the oxidizing agent. The effect of reaction time on molecular weight, chemical structures and hydroxyl content of HTLENR were investigated. The weight average molecular weight (Mw) and polydispersity index (PDI) of the prepared HTLENR were determined using gel permeation chromatography (GPC). The result shows that as the reaction time increased, the Mw decreased indicating the occurrence of higher chain scission. It was found that the lowest Mw was achieved at 10 h reaction time where the Mw and Mn were 37,545 g/mol and 3,233 g/mol. The structural analysis and hydroxyl content of HTLENR on the other hand, were studied by using fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR). The presence of OH group was confirmed by FTIR analysis with the appearance of broad peak at 3,200 - 3,600 cm-1. Subsequently, NMR analysis also confirmed that the highest amount of hydroxyl content which is 7.56 % was achieved at the longest reaction time which is 10 h.

Depolymerisation of liquid epoxidized natural rubber (LENR) using lanthanum hydroxide (La(OH)3)-HNT Catalyst

A simple and versatile method is reported for the synthesis of La(OH)3 on halloysite nanotubes (HNT) for the catalytic depolymerization of liquid epoxidized natural rubber (LENR). The lanthanum nitrate was incorporated into HNT by impregnation method. The characteristics of these La(OH)3−HNT catalysts were investigated by using SEM equipped with Energy Dispersive X-ray (EDX), X-Ray Fluorescence (XRF), Fourier-transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Ultraviolet Visible Light (UV-Vis) and Photoluminescence (PL). The obtained results confirm the presence of La(OH)3 on the surface of HNT. The presence of La(OH)3 -HNT in the LENR exhibited excellent depolymerization reaction resulting in a reduction of the average molecular weight (Mw) from 18984 to 2111. The Mw was measured by gel permeation chromatography (GPC).

Effect of Modified Natural Rubber on Morphology, Chemical Structure, and Crystallinity of Electrospun Polyvinylidene Difluoride Nanofibers

Natural rubber latex was chemically modified by enzymatic deproteinization, degradation, and epoxidation to produce deproteinized liquid epoxidized natural rubber (DP-LENR). Polyvinylidene difluoride (PVDF) was blended with DP-LENR and then electrospun to produce nanofibers. Scanning electron microscopy shows reduction in the fiber diameter and beading formation with increasing concentration of DP-LENR. Smooth surface of nanofibers suggests miscibility and chemical compatibility of PVDF with low concentration of DP-LENR. Infrared spectroscopy and X-ray diffraction analysis show the addition of DP-LENR has no effect on chemical structure and crystallinity of electrospun PVDF.

The Effect of Poly(ethylene-octene) Grafted Maleic Anhydride Elastomer (POEgMA) and Liquid Epoxidised Natural Rubber (LENR) on Mechanical Properties of Poly(hydroxyl-3-butyrate) (PHB)

Poly(hydroxyl-3-butyrate) (PHB) has a great potential in many applications due to its biodegradable and biocompatible properties. However, PHB is considered as a stiff material since it has high brittleness and narrow processing windows which limit the use of PHB. In order to improve the brittleness of PHB, poly(ethylene-octene) grafted maleic anhydride elastomer (POEgMA) and liquid epoxidized natural rubber (LENR) were incorporated into PHB using internal mixer. The blends were melt blended at temperature of 165 °C and rotor speed of 60 rpm for 8 min. The concentration of POEgMA and LENR were varied from 5, 10, 15 and 20 wt%. The mechanical and morphological properties were determined using tensile testing, Izod impact testing and scanning electron microscopy (SEM). Addition of 5 wt% POEgMA decreased the elongation at break and impact strength of PHB. The tensile strength and tensile modulus showed no significant changes with increasing amount of elastomers added to the blends. SEM micrograph revealed smaller rubber particles in the PHB/LENR system in comparison to the PHB/POEgMA blends at the same rubber concentration. The impact strength of PHB/LENR blends decreased significantly with the addition of elastomer. Thus based on this observation, it is suggested that the presence of LENR improves the plasticizing effect of the blends and not acting as an impact modifier.

Preparation of Reinforced Hydroxyl Terminated Liquid Epoxidized Natural Rubber Nanocomposite by Grafting of Graphene Oxide

Abstract In this research, liquid epoxidized natural rubber (LENR) with active end group which known as hydroxyl terminated liquid epoxidized natural rubber (HTLENR) has been synthesized via oxidative degradation method in the presence of cobalt acetyl-acetonate (CAA) and sodium borohydride (NaBH4). The conversion of LENR to HTLENR is vital to fully utilise the great properties of this liquid rubber and enable for further chemical modification. The molecular weight of the prepared HTLENR were confirmed using gel permeation chromatography (GPC) and weight average molecular weight (MW) of HTLENR revealed a slight decrease in comparison to MW of LENR at one hour reaction. Whilst the structure of LENR and HTLENR were studied using Fourier transform infra-red (FTIR) and neutron magnetic resonance (NMR). Subsequently graphene oxide (GO) has been inserted onto HTLENR backbone via grafting method. The efficiency of grafting was confirmed using Fourier transform infra-red (FTIR) analysis. HTLENR/GO nanocomposite prepared is important to be serve as a potential toughening agent which can be used in various applications such as aerospace, structural and automotive.

Mechanical Properties of Epoxy Matrix Composites Toughened by Liquid Epoxidized Natural Rubber (LENR)

Mechanical Properties of Epoxy Matrix Composites Toughened by Liquid Epoxidized Natural Rubber (LENR)

Mechanical properties of hybrid SiC/CNT filled toughened epoxy nanocomposite

Mechanical properties of epoxy nanocomposites filled single filler have been extensively studied by various researchers. However, there are not much discovery on the behavior of hybrid nanocomposite. In this study, single and hybrid nanocomposites of toughened epoxy filled CNT/SiC nanoparticles were investigated. The hybrid nanocomposites samples were prepared by combining CNT and SiC nanoparticles in toughened epoxy matrix via mechanical stirring method assisted with ultrasonic cavitations. Epoxy resin and liquid epoxidized natural rubber (LENR) mixture were first blend prior to the addition of nanofillers. Then, the curing process of the nanocomposite samples were conducted by compression molding technique at 130°C for 2 hours. The purpose of this study is to investigate the hybridization effect of CNT and SiC nanoparticles on mechanical properties toughened epoxy matrix. The total loading of single and hybrid nanofillers were fixed to 4% volume are 0, 4C, 4S, 3S1C, 2S2C, and 1S3C. Mechanical properties of hybrid composites show that the highest value of tensile strength achieved by 3S1C sample at about 7% increment and falls between their single composite values. Meanwhile, the stiffness of the same sample is significantly increased at about 31% of the matrix. On the other hand, a highest flexural property is obtained by 1S3C sample at about 20% increment dominated by CNT content. However, the impact strength shows reduction trend with the addition of SiC and CNT into the matrix. The hybridization of SiC and CNT show highest value in sample 1S3C at about 3.37 kJ/m2 of impact energy absorbed. FESEM micrograph have confirmed that better distributions and interaction observed between SiC nanoparticles and matrix compared to CNT, which contributed to higher tensile strength and modulus.

Properties of natural rubber filled with untreated and treated spent coffee grounds

ABSTRACTThis work studied the properties of spent coffee ground (SCG) filled natural rubber (NR). The SCG was initially characterized by various techniques, prior to being added into rubber. Results revealed that SCG had relatively large particle size with very low specific surface area. It is mainly composed of organic compounds (such as protein, fatty acid, cellulose, hemicellulose, and lignin) with small quantity of inorganic substances (oxides of potassium, silicon, magnesium, calcium, and phosphorous). The incorporation of SCG in NR gave relatively low reinforcement and tended to retard vulcanization due to the presence of hydroxyl groups on the SCG surface. In addition to untreated SCG, reinforcement of SCG treated by liquid epoxidized natural rubber (LENR) and bis‐(3‐triethoxysilylpropyl) tetrasulfide (TESPT) was investigated. Improvement of rubber properties was observed when SCG surface was treated. Overall, TESPT‐treated SCG gave the rubber with the highest mechanical properties, followed by LENR‐treated SCG and untreated SCG, respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46060.

Preparation of Liquid Epoxidized Natural Rubber by Oxidative Degradations Using Periodic Acid, Potassium Permanganate and UV-Irradiation

Epoxidized natural rubber (ENR) needs to be degraded into shorter chain lengths, to form liquid epoxidized natural rubber (LENR), for applications such as coating and adhesives. Since ENR contains both C=C and epoxide groups as reactive sites for degradation reactions, thus, LENR could be prepared by different methods through cleavages of C=C or epoxide groups, or a combination of both sites. Different mechanisms would produce different terminals on the LENR. This paper reports the oxidative degradation by (a) periodic acid, (b) potassium permanganate and (c) ultra violet (UV) irradiation. The degraded rubbers were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR) and Fourier transform infra-red spectroscopy (FTIR). Ester and ketone terminals were formed in all the three methods, but lactone and hydrofuranic structures were observed only in degradation by UV irradiation. NMR spectrum reveals that cyclization of ENR has occurred during degradation by periodic acid. At lower periodic acid concentration, degradation takes place only via C=C cleavage, but at higher concentration, the attack to the epoxide groups becomes more prominent. Potassium permanganate has attacked both the double bonds and epoxide groups. On the other hands, epoxide group was not affected during degradation by UV irradiation, which cleaved only the C=C bonds.

Epoxidation and Hydroxylation of Liquid Natural Rubber

Liquid natural rubber (LNR) was functionalized into liquid epoxidized natural rubber (LENR) and hydroxylated LNR (LNR-OH) via oxidation using a Na2WO4/CH3COOH/H2O2 catalytic system. Microstructures of LNR and functionalized LNRs were characterized using Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopies. The effect of CH3COOH, H2O2, Na2WO4, reaction time and temperature. reaction time and temperature on epoxy content were investigated. LNR-OH was obtained when oxidation reaction was conducted at a longer reaction time, higher temperature or excess amount of catalyst. Thermogravimetric analysis (TGA) reported the thermal behavior of functionalized LNRs. Molecular weight and polydispersity index (PDI) were determined using gel permeation chromatography (GPC).

CHARACTERIZATION OF RUBBER TOUGHENED EPOXY REINFORCED HYBRID KENAF/CARBON FIBER VIA WATER ABSORPTION AND THERMAL DEGRADATION

Toughened epoxies reinforced by hybrid of kenaf/carbon fiber, untreated and treated, with the addition of liquid epoxidized natural rubber (LENR), were tested for their water absorption and thermal degradation. Water absorption testing was conducted based on ASTM D1037 to study the effects of kenaf fibre and carbon fibre on water uptake property. In the thermal analysis, the thermal degradation of the specimen was investigated towards heat. The test used a termogravimetric analysis machine, model Mettler Toledo-TGA, at temperature range of 50 OC to 350 OC with an increment of 10 OC/min where the results showed the decreasing of degradation temperature when the treated fiber was used. The results also showed that the percentage of water absorptions for composites with the addition of LENR were lower compared to those of composites without LENR.

MECHANICAL PERFORMANCE OF MODIFIED EPOXY REINFORCED HYBRID NATURAL FIBER COMPOSITE

Kenaf fiber that is known as Hibiscus cannabinus, L. family Malvaceae is an herbaceous plant that can be grown under a wide range of weather conditions. The usage of kenaf fibers as a reinforcement material in the polymeric matrix has been widely investigated. In this research, liquid epoxidized natural rubber (LENR) was introduced to the epoxy to increase its toughness. Hybrid kenaf/carbon fibers, with different kenaf/carbon ratio weight, were used to reinforce the epoxy resins (with and without addition of epoxidized natural rubber) as the matrices. The flexural strength, flexural modulus and fracture toughness of the rubber toughened epoxy reinforced hybrid kenaf/carbon fiber composites were investigated. The results showed that the addition of liquid epoxidized natural rubber (LENR) had improved the flexural strength, flexural modulus and fracture toughness by 9.6%, 13.7%, and less 2% respectively at the ratio of 16:4 wt% fibre loading

Toughened polyester cellulose nanocomposites: Effects of cellulose nanocrystals and liquid epoxidized natural rubber on morphology and mechanical properties

Unsaturated polyester resin (UPR) has been modified with a liquid epoxidized natural rubber (LENR). The addition of LENR improves the toughness, but it is inevitably accompanied by a significant loss in stiffness, yield strength, and thermal resistance. Incorporation of a rigid material into the LENR–UPR blend, such as cellulose nanocrystal (CNC), provided a ternary polyester nanocomposites with desire mechanical properties. In the present work, the effects of different CNC and LENR content on the nanocomposite morphology and mechanical properties were examined. Morphological studies revealed that the size of the rubber particles is independent of the rubber content due to the chemical interaction of rubber and matrix; however, the size of the LENR particles increased with increasing CNC content. Tensile tests indicated that the blend’s tensile strength and elastic modulus could be further improved by incorporation of the CNCs. The high crystallinity and surface area of CNCs were the main factors for improvement of tensile properties of the blend. Moreover, the impact energy of the UPR improved when it was modified with the LENR, and even further improvement was achieved with the CNC addition to form nanocomposites. Dynamic mechanical thermal analysis (DMTA) showed that the storage modulus of nanocomposites with 1.5wt% rubber content was lower than those with 4.5wt% LENR; however, both samples showed a higher storage modulus than the neat UPR and the unfilled blend. The glass transition temperature (Tg) of the UPR decreased with the LENR addition, but improved with the addition of CNCs. The nanocomposites prepared with a higher LENR content displayed better mechanical properties than those with low LENR content.