Liquid Natural Rubber Research Articles

Effect of triblock copolymers based on liquid natural rubber and low molecular weight poly(lactic acid) on physical properties of poly(lactic acid)/natural rubber blend

Triblock copolymers of poly(lactic acid) (PLA) and natural rubber (NR) (PLA–NR–PLA) with different lengths of PLA end blocks were produced from hydroxyl-terminated liquid natural rubber (HTLNR) and low molecular weight PLA (pre-PLA). The HTLNR with a number-average molecular weight $$(\bar{M}_{\text{n}} )$$ ~ 28,000 g/mol obtained from photochemical degradation of NR and pre-PLA with varying molecular weight ( $$\bar{M}_{\text{n}}$$ ~ 3000, ~ 6500, ~ 9700 g/mol) was subjected to condensation polymerization. The compatibilizing effect of copolymers on the physical properties of the PLA/NR blend was studied using PLA/NR/PLA–NR–PLA blend ratios of 90/10/0, 90/9/1, 90/8/2 and 90/7/3 percent by weight (wt%). From the tensile testing results, elongation at break of the blends increased with an increase in the amount of triblock copolymer and with the length of the PLA end block. The blend without the copolymer showed elongation at break of 60.54%, whereas the blend with 3 wt% of PLA–NR–PLA prepared from pre-PLA with $$\bar{M}_{\text{n}}$$ of ~ 9700 g/mol showed elongation at break of 199.38%. This was about a 300% increase. The highest impact strength of 79.58 kJ/m2 (400% higher than neat PLA) was also found for the blend containing 3 wt% of PLA–NR–PLA with the longest PLA end block. A reduction in the diameter and well dispersion of the rubber particles in the PLA matrix were seen in micrographs taken with a scanning electron microscope. In general, after the addition of PLA–NR–PLA into a PLA/NR blend, the Tg of NR phase shifted to a higher temperature, whereas the Tg of the PLA phase decreased. The PLA–NR–PLA triblock copolymer with the longest PLA end block is possibly used as an effective compatibilizer for the PLA/NR blend.

Preparation, characterization and properties of liquid natural rubber with low non-rubber content via photodegradation

Photodegradation of natural rubber (NR) latex produced low molecular weight liquid natural rubber (LNR). During the photodegradation, organic materials particularly surfactants and non-rubbers also decomposed. The decomposition of surfactants and non-rubbers could influence the stability of the latex. Anionic and non-ionic surfactants were used to stabilize NR latex during the photodegradation. It was found that the anionic surfactant gave better resistance to oxidizing agent and UV radiation compared to the non-ionic surfactant. Hence, better stability of the NR latex was observed throughout the reaction. The zeta potential of NR latex increased during photodegradation due to the presence of negatively charged substances. The nitrogen content, which represents protein in NR decreased after photodegradation, whilst the phosphate content, which represents phospholipid head increased in the serum. This indicates the occurrence of decomposition of the non-rubber compounds in NR. The molecular weight of NR latex stabilized with anionic surfactant, sodium dodecyl sulphate, reduced from 544 × 103 to 19 × 103 g/mol after 48 h of reaction. SEM micrographs showed the latex particles of LNR were spherical and larger compared to NR. FTIR and NMR spectra confirmed the presence of telechelic hydroxyl and carbonyl groups, resulted from the chain cleavage.

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.

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.

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.

Impregnation of liquid natural rubber (LNR) foam with activated carbon for enhancing oil removal from water

Impregnation of liquid natural rubber (LNR) foam with activated carbon for enhancing oil removal from water

Use of Carboxy Terminated liquid Natural Rubber (CTNR) as a reactive polymeric plasticizer in chloroprene vulcanizates

Maleic anhydride was chemically attached to depolymerized natural rubber by a photochemical reaction. The product is named as Carboxy Terminated liquid Natural Rubber (CTNR). This paper describes the use of CTNR as a reactive polymeric plasticizer for chloroprene (CR) vulcanizates, which can improve the tensile properties and ageing resistance of the chloroprene vulcanizates, due to similarity in polarities. The efficiency and permanence of this polymeric plasticizer were compared with that of conventional plasticizer in silica and carbon black filled CR vulcanizates. It is found that CTNR could replace the conventional plasticizer either partially or fully. A combination of the conventional plasticizer and CTNR could improve the ageing and oil resistance of the chloroprene vulcanizates.

Improving Asphalt Binder Properties Using Recycled Polyethylene Terephthalate and Natural Liquid Rubber

This paper investigates adding two types of polymer to asphalt binder in different proportions to demonstrate the effect of their mechanical properties on the asphalt. A 10% addition of polyethylene terephthalate (PET) is used in this research with different percentages of liquid natural rubber (LNR at 2%, 4%, 6%, and 8%). The natural rubber chemically is heated to increase the surface area to achieve the best penetration and to overcome phase separation issues caused by the difference in the densities of the rubber and asphalt. The asphalt tests showed improvement in the structures and viscosity, with a reduced softening point and improvements in temperature susceptibility with increases in the natural rubber ratio. The FTIR spectroscopy confirmed that the asphalt modification is a physical process, and other tests showed an increase in the asphalt binder resistance at low temperatures.

Magnetic properties of TPU/NR blends: low loading NiZn and LNR added

Thermoplastic polyurethane and natural rubber blending are able to change the origin properties polymer material. Then, this blend was added with magnetic filler, NiZn at low loading of 1wt% to 5wt%. Other than that, liquid natural rubber (LNR) was also added as compatibilizer. The previous study presented, NiZn ferrite at 3wt% in TPU/NR blend is the optimum filler loading, but LNR was not unbeaten in its role as compatibilizer. The addition of this magnetic filler enhanced the magnetic properties on saturation magnetization and remanence magnetization but decreased the value of coercive force.

Ultrasonic-enhanced synthesis of rubber-based hydrogel for waste water treatment: Kinetic, isotherm and reusability studies

Hydrogel is used as an adsorbent for the removal of dyes and heavy metals in waste water. In this work, different methods of synthesising novel hydrogels from liquid natural rubber (LNR) were investigated. The two different methods were ultrasonic-assisted polymerisation and heating under reflux. Through graft modification, LNR had initially combined with maleic anhydride (MaH) using benzoyl peroxide (BPO) as a radical initiator. After grafting, acrylic acid (AA) was crosslinked onto LNR-g-MaH using N,N-methylenebisacrylamide (MBA) and potassium persulfate (KPS) as a crosslinker and initiator, respectively. The best method between the two different techniques was identified via a five-level-two-factor response surface methodology (RSM). Higher adsorption percentage (93.34%) was observed in the ultrasonic technique. Meanwhile, the effects of adsorbent mass, dye concentration, pH solution and ionic strength were also investigated and results showed that different conditions were found to give different MG dye adsorption rates. The adsorption of MG dyes on hydrogel is dependent on pH and ionic strength solution. This action indicates an ion exchange mechanism. From an isotherm study, it was found that the Freundlich isotherm best fitted the adsorption of MG dyes. Furthermore, the adsorption kinetic data followed the pseudo-second order kinetic model and the reusability of hydrogel was also investigated.

Effect of Temperature, Time and Diimide/Rubber Ratio on the Hydrogenation of Liquid Natural Rubber by Response Surface Methodology

Hydrogenated liquid natural rubber (HLNR) was synthesized from liquid natural rubber (LNR) by thermolysis of p-toluenesulfonyl hydrazide (TSH). The HLNR structure was characterized by Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies. Thermogravimetric analysis (TGA) showed that the HLNR had higher decomposition temperature compared to LNR. A response surface methodology (RSM) based on a central composite rotatable design (CCRD) with five-level-three-factors was used to optimize the main important reaction parameters, such as the TSH:LNR weight ratio (1–3), reaction temperature (110–150 °C), and reaction time (1–8 h). A quadratic model was developed using this multivariate statistical analysis. Optimum conditions for the non-catalytic hydrogenation of LNR using TSH were obtained; an LNR hydrogenation percentage of 83.47% at a TSH:LNR weight ratio of 1.41, a reaction temperature of 118.11 °C, and a reaction time of 3.84 h were predicted. The R2 value of 0.9949 indicates that the model provides data that are well matched with those from the experiment.

New Approach on the Modification of Liquid Natural Rubber Production using Microwave Technique

High-speed synthesis using microwave technique has attracted considerable intentions among researchers as it provides an efficient time of doing reactions. Modification of liquid natural rubber (LNR) via hydrogenation using of 2,4,6-trimethylbenzenesulfonylhydrazide (MSH) produced hydrogenated liquid natural rubber (HLNR). The results showed that microwave-assisted hydrogenation of LNR was experimentally found to give expected product in a short time (10–20 min). The structure of products was characterized by Fourier-transform infrared (FTIR) and the percentage of hydrogenation was determined from the 1H-NMR spectrum. The highest hydrogenation percentage of HLNR for hydrogenation of LNR by microwave heating were obtained; an LNR hydrogenation percentage of 41.18% at a MSH:LNR weight ratio of 1.5:1, a microwave power of 600 W and a reaction time of 20 min. Diimide molecules have been generated more quickly at microwave frequencies and yield HLNR in a shorter time compared to reflux heating method.

Stacked-Cup Carbon Nanotube Flexible Paper Based on Soy Lecithin and Natural Rubber.

Stacked-cup carbon nanotubes (SCCNTs) are generally referred to as carbon nanofibers (CNFs). SCCNTs are much less expensive to fabricate and are regarded as good polymer modifiers suitable for large-scale production. Flexible, SCCNT-based soy lecithin biocomposites were fabricated using liquid natural rubber latex as binder. Natural polymers and the SCCNTs were dispersed in a green solvent using a benchtop high-pressure homogenizer. The inks were simply brush-on painted onto cellulose fiber networks and compacted by a hydraulic press so as to transform into conductive paper-like form. The resulting flexible SCCNT papers demonstrated excellent resistance against severe folding and bending tests, with volume resistivity of about 85 Ω·cm at 20 wt % SCCNT loading. The solvent enabled formation of hydrogen bonding between natural rubber and soy lecithin. Thermomechanical measurements indicated that the biocomposites have good stability below and above glass transition points. Moreover, the SCCNT biocomposites had high through-plane thermal conductivity of 5 W/mK and 2000 kJ/m3K volumetric heat capacity, ideal for thermal interface heat transfer applications.

Adsorption of Nickel Ion in Aqueous Using Rubber-Based Hydrogel

This work reports about a rubber-based hydrogel from liquid natural rubber (LNR) and acrylic acid (AAc) by using potassium persulfate (KPS) as an initiator and N,N-methylenebisacrylamide (MBA) as a crosslinking agent. The structure, stability, and morphology of the hydrogel were confirmed by using Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscope. The optimisation of the swelling capacity and Ni2+ removal percentage by the rubber-based hydrogel was conducted by using 5-level-2-factor response surface methodology. The effect of AAc:LNR ratio (0.59–3.41 g/g) and MBA concentration (0.02–0.23 M) parameters was studied with constant KPS concentration (0.05 M) used. Quadratic models for both responses (swelling and Ni2+ removal percentage) were successfully developed by using statistical analysis. The swelling degree and Ni2+ removal percentage of hydrogel were improved when high AAc:LNR ratio and lower MBA concentration were used. The R2 values for these quadratic models were 0.9891 and 0.9939 (swelling and Ni2+ removal percentage), respectively, which showed that the models were well-fitted with the experimental data. From the analysis, the optimum conditions for maximum swelling capacity (1181.90%) and Ni2+ removal percentage (26.74%) were hydrogel with AAc:LNR ratio 3.00 g/g and 0.05 M of MBA.

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.

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).

Fabrication of rubber gel as oil absorbent by using water as porosity agent for oil removal

ABSTRACTOil pollution is a crucial issue that has adversed impact not only on the environment but also human beings. As an alternative to all conventional approaches, a porous rubber gel based on liquid natural rubber (LNR) with excellent hydrophobic and wettability properties has been developed using a simple vulcanization reaction. To determine their sorption capability, LNR gel was employed for absorption of various types of oils such as Petrol A, Petrol B, kerosene, diesel, crude oil, and olive oil. The functionality of LNR gel was characterized by Fourier transform infrared spectroscopy and the morphology of LNR gel was observed using a scanning electron microscope. By combining wettability and hydrophobicity, the LNR gel exhibited high oil sorption capacity and selectivity for oil removal from water. The LNR gel was able to absorb oils, especially the low viscosity types. Besides, it can also be reused up to 20 cycles while maintaining its oil sorption performance. The selective absorbent shows the recovery of petrol in the range of 96–99% by squeezing the oil. Thus, LNR gel has great potential as green material for cleaning up oil contaminants on a large scale. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47749.

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.

Effectiveness of cellulosic Agave angustifolia fibres on the performance of compatibilised poly(lactic acid)-natural rubber blends

In this study, A. angustifolia cellulose was tested as a potential fibre for use in biocomposites based on a polylactic acid (PLA)/natural rubber (NR) blend compatibilised with liquid natural rubber. Biocomposite analyses were performed via mechanical, physical, morphological, thermal, and biodegradation characterisations to evaluate the influence of the cellulose content on the properties of biocomposites. The addition of Agave cellulose improved the tensile properties of the biocomposites with biocomposites reinforced by 7.5 wt% cellulose showing maximum tensile strength. Differential scanning calorimetry analysis showed that Agave cellulose acts as a nucleating agent for PLA, and the thermal stability improved up to 6% upon cellulose addition. Soil burial tests revealed that the biodegradability, which is directly influenced by the water absorption of the biocomposites, increased with increasing cellulose addition. Finally, water absorption tests indicated that biocomposites with low water resistance increase the degradation rates of the PLA–NR blends.

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.