pH Of Latex Research Articles

Effect of Tomato Juice Volume on Coagulation Time and Latex Weight

Natural latex clumping takes longer than using chemicals. Another alternative is needed to coagulate the latex by adding acid from natural ingredients. Tomatoes (Lycopersicum esculentum Mill) have 29.32 mg of ascorbic acid and 0.54 g of citric acid every 100 grams, they have the potential to be used as a natural latex coagulator. The research method add tomato juice to fresh latex to break down the emulsion and form rubber lumps. After mixing, the weight of the latex is weighed. The constant variables are the latex volume of 10 ml, and the tomato juice volume of 5,10,20,30,40,50,60,70,80,90 and 100 ml respectively. The higher the volume of tomato juice, the faster it will clot. The best volume of tomato juice is 100 ml with a clumping time of 52 minutes. Increasing the volume of tomato juice increased the weight of latex to 13.1 grams and reduced the pH of latex to 4.9. Giving tomato juice every 5 ml accelerated clumping up to 360 minutes (6 hours) compared without tomato juice.

Combination of exploitation systems to optimize yield of GT1 clone in smallholder rubber (Hevea brasiliensis) plantation in Sumatera Utara, Indonesia

Clone GT1 is one of the low metabolism clones and is recommended for smallholder and large plantations. These clones are responsive to stimulants and reach production peak at the mid-economic cycle period. Its production can reach 2200-3000 kg-1ha-1year-1 and is relatively more resistant to high exploitation pressures if the agroecosystem conditions are suitable. This study aimed to determine the effect of the combined application of liquid stimulant concentration and tapping interval on the physiology and productivity of latex in rubber clone GT1. This research was conducted at Naga Rejo Village, Galang District, Regency of Deli Serdang, Province of Sumatera Utara, located at an altitude of 49 masl with Ultisol soil type. The research design is factorial randomized completed block design (RCBD) consisting of 9 levels, namely S2d4 without a stimulant, S2d4 ET 3.5%, S2d4 ET 4.5%, S2d5 without a stimulant, S2d5 ET 3.5%, S2d5 ET 4.5%, S2d6 without a stimulant, S2d6 ET 3.5%, S2d6 ET 4.5 % with three replicas of each treatment. The results showed that the tapping system on clone GT1 obtained the highest annual production with tapping system S2d4 ET 4.5% (DS3) of 214.51 g/t/y. The lowest production is obtained in January-March when the leaves fall. High sucrose levels in the non-stimulant treatment (8.54 -12.98 mM) indicated that at least sucrose was converted into latex. The pH of latex is directly proportional to the stimulant, so an increase in the concentration of the stimulant raises the pH and metabolism of latex formation.

Pengaruh Penambahan Ekstrak Jeruk Purut (Cytrus hitrix D.C) Sebagai Koagulan Alami Terhadap Karakteristik Karet

Natural rubber is a plantation commodity that has a significant role in the country's economy. This study aims to determine the effect of the natural coagulant extract of kaffir lime with centrifugation and non-centrifugation treatment on the coagulation process, pH and coagulation time, characteristics of rubber clone IRR 118 and comparison of the quality of rubber with 2% formic acid chemical coagulant. The volume of coagulant used was 75 mL mixed with 150 mL of latex, so that coagulation occurred and produced coagulum. Then the resulting coagulum is analyzed for the characteristics of the rubber to determine the quality of the rubber. Characteristic analysis carried out was Dry Rubber Content (DRC), Initial Plasticity (Po), Plasticity Retention Index (PRI), Mooney Viscosity, ash content, impurities content, volatile matter content, and nitrogen content. The results showed that the natural coagulant extract of kaffir lime could coagulate latex, lowering the pH of latex thereby speeding up coagulation time. From the rubber characteristic test using kaffir lime natural coagulant it complies with SNI 06-1903-2017 SIR 20. The quality of rubber produced from using kaffir lime natural coagulant extract as a coagulant can equate the quality of rubber produced by using 2% formic acid chemical coagulant, but coagulant The natural ingredients used have drawbacks, namely the availability of seasonal fruit, and the need for treatment before being used as a coagulant.

Determination of optimal latex pH level and evaluation of natural rubber coagulum quality when using lactic acid for coagulation of rubber latex

The objectives of this study were to determine the optimal latex pH level for coagulation of rubber latex using lactic acid and to evaluate the effects of lactic acid on natural rubber coagulum quality. In this study, 3% lactic acid was added to the latex until the latex pH values reached 4.6, 4.9, 5.2, 5.5 and 5.8; meanwhile, the control treatment was added with 3% acetic acid until the latex pH value was at 5.4. The rubber coagula of the optimum and the control treatment were evaluated for mechanical, physical and chemical criteria based on the international standards of quality for natural rubber grades. The results showed that latex pH of 5.5 resulted from the addition of 3% lactic acid was the optimum for latex coagulation, which also helped to reduce the necessary amount of acid used in latex coagulation and therefore reducing the risk of water pollution. The quality of natural rubber coagulum that was coagulated by lactic acid met all requirements of technical standard for SVR 5 grade based on the Standard Vietnamese Rubber 3769:2004. The rubber coagulum coagulated by 3% lactic acid had a higher initial plasticity (Po) and a lower plasticity retention index (PRI) than that coagulated by 3% acetic acid.

Preparation, rheology, and film properties of polyacrylate latex using amphiphilic macroreversible addition‐fragmentation chain transfer agents as surfactants

ABSTRACTReversible addition‐fragmentation chain transfer (RAFT) radical emulsion polymerization of n‐butyl acrylate (nBA) and methyl methacrylate (MMA) was successfully performed in the presence of the amphiphilic macro‐RAFT agents poly(acrylic acid‐b‐styrene) (PAA‐PSt) trithiocarbonate. First, the amphiphilic macro‐RAFT agents PAA‐PSt were prepared and their surface activities in aqueous solutions were studied. Subsequently, the effects of pH values of the latexes and degree of polymerization (DP) of the PAA hydrophilic segments in the amphiphilic macro‐RAFT agents on the latex particle size and molecular weight of the polyacrylate products, as well as the rheological properties of the latexes, surface morphology, and water resistance of the latex films were investigated in detail. It was found that the rheological behaviors of the as‐prepared latexes can be tuned by adjusting solid content, temperature, pH value, and DP of the hydrophilic segments, respectively, due to their effects on particle packing, hydrophobic association, hydration layer, and hydrodynamics volume. In addition, atomic force microscopy (AFM) was applied to investigate the surface morphology, and the results demonstrated that the surface phase separation and roughness of the latex films changed with the latex pH values and DP of the hydrophilic segments. Finally, the films with good water resistance were obtained by directly casting the as‐prepared polyacrylate latexes at room temperature. Our study indicated that employing amphiphilic macro‐RAFT agents to prepare polyacrylate latexes with well‐defined chemical compositions and structures is a facile and environmentally friendly strategy, which would have wide potential application in coatings, inks, adhesives and thickening agents, and so on. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47463.

CELLULASE IMMOBILIZATION ON POLY(METHYL METHACRYLATE) NANOPARTICLES BY MINIEMULSION POLYMERIZATION

Abstract Cellulases are efficient enzymes for the conversion of cellulose into glucose. Their use in immobilized form enables them to be reused in successive cycles in many biotechnological processes. Unlike conventional methods of immobilization by covalent bonding, in miniemulsion polymerization the immobilization of enzyme and the synthesis of polymer nanoparticles (support) occur simultaneously. Based on these aspects, the immobilization of cellulose on poly(methyl methacrylate) (PMMA) nanoparticles by miniemulsion polymerization was studied. The surfactant type (non-ionic and ionic) and latex pH showed great influence on cellulase activity. High activity values were obtained only when non-ionic surfactant (Lutensol AT50) and buffering agent (NaHCO3) were used simultaneously. MMA polymerization rate and final monomer conversion were not affected by the presence of cellulase. The maximum immobilization efficiency (60%) was obtained when 6 wt.% of cellulase was used and stable PMMA nanoparticles (133 nm) were obtained. The relative activity profile of immobilized cellulase, for pH as well as temperature, was similar to that reported for the free form. Immobilized enzyme keeps its activity throughout seven days when stored at 4 oC and phosphate buffer pH 6.0. Based on the results obtained in this work, miniemulsion polymerization as a method for cellulase immobilization on PMMA nanoparticles showed to be a promising technique with high possibility of industrial application.

Ind

Smoke liquid is a liquid obtained from smoke condensation during charcoal firing process. The main content of the smoke liquid is acetic acid, hence, can be used as an alternative latex coagulant. Acid in vinegar can reduce the pH of latex and cause the latex to coagulate rapidly. This paper determines effectiveness of using smoke liquid as a latex coagulant and characteristics of the treated latex. The smoke liquid in this study was derived from pine wood. The smoke liquid solutions consisted of the crude smoke liquid and the diluted solution in various concentrations of 5, 10, 15 and 20%. The smoke liquid solution was then each poured into a container of latex. Testing was undergone by observing latex coagulating time, coagulate condition, texture, color, odor and homogenity. The most effective smoke liquid which produced the best latex based on its performances was then taken for further testing of physico-chemical properties which included dry rubber content, plasticity retention index (PRI), initial plasticity (Po), final plasticity (Pa), dirt content, ash content, volatile matter content (Vm), and nitrogen content. Results were then compared with the conventional use of formic acid as a control coagulant. The result showed that the crude and distillate smoke liquid solutions with concentration of 10% produced the best coagulantperformances than the other solutions. Rubber latex treated with the crude smoke liquid produced the best physico-chemical properties and could meet requirements of the Indonesian National Standard (SNI) for Rubber Quality.

The Chemical Study of<i> Calotropis</i>

Calotropis (Asclepiadaceae) commonly known as “madar” is a useful medicinal plant. The two species i.e. Calotropis gigantea and Calotropis procera are to a great extent having a very similar chemical properties, but the colours of their flowers are different. The pH of latex of these two species has been found different in the present study. The temperature effects have been noticed on their pH values which is varying from 7.2 to 8.1 between the temperatures 25 °C to 45 °C and then remains constant for Calotropis gigantia. The milky latex contains hydrocarbons, fatty acids, sterols and terpenels. Seven spots have been observed on the TLC plates; out of which 3 were identified as calotoxin, uscharin and calactin. Aluminum, calcium, cadmiun, cobalt, chromium, copper, iron, magnese, magnesium, nickel, lead, and zinc metal elements were investigated in the latex and similarly in the leaves and bark from the AA spectra. The amount of magnese was found the highest in the latex of both species but calcium was found highest in leaves and bark of both species. Copper, chromium and lead were not found at all in latex but a very little amount of copper and lead were found in leaves and bark. The atomic absorption spectrophotometer was used to investigate the metals which were measured in the order of ppm.

The Chemical Study of<i> Calotropis</i>

Calotropis (Asclepiadaceae) commonly known as “madar” is a useful medicinal plant. The two species i.e. Calotropis gigantea and Calotropis procera are to a great extent having a very similar chemical properties, but the colours of their flowers are different. The pH of latex of these two species has been found different in the present study. The temperature effects have been noticed on their pH values which is varying from 7.2 to 8.1 between the temperatures 25 °C to 45 °C and then remains constant for Calotropis gigantia. The milky latex contains hydrocarbons, fatty acids, sterols and terpenels. Seven spots have been observed on the TLC plates; out of which 3 were identified as calotoxin, uscharin and calactin. Aluminum, calcium, cadmiun, cobalt, chromium, copper, iron, magnese, magnesium, nickel, lead, and zinc metal elements were investigated in the latex and similarly in the leaves and bark from the AA spectra. The amount of magnese was found the highest in the latex of both species but calcium was found highest in leaves and bark of both species. Copper, chromium and lead were not found at all in latex but a very little amount of copper and lead were found in leaves and bark. The atomic absorption spectrophotometer was used to investigate the metals which were measured in the order of ppm.

The diacetone acrylamide crosslinking reaction and its control of core‐shell polyacrylate latices at ambient temperature

AbstractSelf crosslinkable core‐shell polyacrylate latices (PAs) cured at ambient temperature were synthesized by semicontinuous‐seeded emulsion polymerization with diacetone acrylamide (DAAM) and adipic dihydrazide (ADH) as crosslinkable monomers. The influences of DAAM monomer mass content, neutralizer, and curing temperature on the properties of self crosslinkable core‐shell latices and the keto‐hydrazide crosslinking were discussed. The spectroscopic techniques such as Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), atomic force microscopy (AFM), transmission electron microscopy (TEM), and contact angle instruments were used to determine the structure and properties of PAs. The water evaporating rate during the film‐forming process of self crosslinkable core‐shell latices was also investigated. FTIR analyses demonstrate that the keto‐hydrazide crosslinking reaction does not occur in the latex environment but occurs at ambient temperature with the evaporation of water during the film‐forming process. The results of DSC show that the core‐shell crosslinkable PAs have two glass transition temperatures (Tg), and Tgs of crosslinked film are higher than that of non crosslinked fim. Moreover, the keto‐hydrazide reaction is found to be acid catalyzed and favored by the loss of water and the simultaneous decrease in pH arising from the evaporation of ammonia or amines during film‐forming process. Hence, in the volatile ammonia or amines neutralized latices, the latex pH value adjusted to 7–8, which not only ensure the crosslinkable latex with good storage stability but also obtain a coating film with excellent performances by introducing the keto‐hydrazine crosslinking reaction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

The diacetone acrylamide crosslinking reaction and its influence on the film formation of an acrylic latex

Waterborne colloidal polymers (i.e. latex) represent a promising alternative to organic solvent-based systems in coatings applications. The development of mechanical strength and hardness is often enhanced by chemical crosslinking that creates a three-dimensional network. If extensive crosslinking occurs within the particles prior to their coalescence, however, interdiffusion will be prevented. A weaker product will result. We have explored the inter-relationship between coalescence, crosslinking, and surfactant exudation in an acrylic latex containing diacetone acrylamide exploiting the “keto-hydrazide” crosslinking reaction. The complementary use of spectroscopic techniques on a model system determined that the crosslinking reaction yields an imine, not an enamine as has been proposed in some literature. Gel fraction measurements were used to probe the rate and amount of crosslinking and identified a slower rate in larger particles, suggesting that the transport of crosslinking agent is rate-limiting. The keto-hydrazide reaction was found to be acid catalyzed and favored at lower water concentration. Measurement of the latex pH relative to the polymer mass fraction during film formation clarified the expected point of onset for crosslinking in relation to particle packing. Atomic force microscopy was used to follow surface leveling relative to the competing influence of crosslinking. The rate and total amount of surfactant exudation were found to be influenced by crosslinking, particle deformability (as determined by the temperature relative to the polymer glass transition temperature), and the evaporation rate (as controlled by the relative humidity). There is evidence that surfactant exudation can be triggered by the particle deformation that occurs at film formation temperatures well above the glass transition temperature.

Manufacture Process of Light Calcium Carbonate from Limestone

This process and parameters of fabricating light calcium carbonate from limestone were discussed in the paper. Raw limestone in experiment comes from Luquan city, Hebei province. The results of chemistry and XRD analysis indicate that ingredient of this limestone is mainly calcium carbonate, dolomite, silicon dioxide, which takes 83.81%, 11.03% and 1.67% separately, and a few of other impurities. The process includes calcinations, assimilation, carbonation, drying and others. It was ascertainable that the time of calcinations exceeded 5 hours at 850~ 950 and loss of calcinations was 42%. The time of assimilation was around 25 minutes at 70~90The time of carbonation was about 30 minutes at 50~90, and the airflow was about 160L/min and PH of latex after carbonation was 7.2~7.4. The light calcium carbonate product was obtained in experiment, whose fine sphere size was about 10 nanometer, with the agglomeration particle size 2~3μm. The degree of white improved from 42 to 76. As a result, the comprehensive properties of the produce were improved consumedly.

Studies of Dimethyl Meta‐Isopropenylbenzyl Isocyanate (TMI) for Preparation of Ambient Cross‐linkable Latexes—Film Formation and Cross‐Linking

Single‐pack, ambient cross‐linkable acrylic latexes containing dimethyl meta‐isopropenylbenzyl isocyanate (TMI) repeat units were prepared by batch and semicontinuous emulsion polymerization processes at 40°C using methyl methacrylate (MMA) and n‐butyl acrylate (BA) as the principal comonomers and methacrylic acid (MAA) as a functional comonomer. Degree of cross‐linking and mechanical properties of films from batch latexes increased as the level of TMI increased from 0–5 wt%. Increasing latex pH (from 1–4) to 9 by adding dilute aqueous NaOH brings about an increase in degree of cross‐linking and mechanical properties of films. This effect is further enhanced by incorporation of MAA repeat units, which also give rise to physical cross‐linking through associations between MAA repeat units. Thus, by use of both TMI and MAA, a synergy is achieved in which the TMI repeat units provide for chemical cross‐linking that is accelerated by the effect of MAA repeat units, which also provide for physical cross‐linking, leading to greater improvements in film mechanical properties than when only TMI or MAA is incorporated. Core‐shell particles with an outer TMI/MAA‐containing layer are more susceptible to aliphatic isocyanate (NCO) hydrolysis, which can be detrimental if the rate of hydrolysis is too high. Although the rate of NCO hydrolysis in the TMI/MAA‐containing phase can be reduced by having an outer phase of unreactive poly(MMA/BA), this also prevents development of strong interfaces between particles during film formation. The TMI latexes are colloidally stable during storage for one year, but suffer from extensive NCO hydrolysis and substantial intraparticle cross‐linking, which converts the particles into microgels. The mechanical properties of films from the stored latexes are far inferior to films cast just after latex preparation due to the poor film integrity resulting from the low level of interparticle chemical cross‐linking. Thus, in order to obtain optimum properties in films, TMI latexes should be used soon after preparation and NCO hydrolysis must proceed at a rate that is synchronized with the particle integration stage of film formation. Dedicated to Professor John L. Stanford on the occasion of his 60th birthday.

Studies of Dimethyl Meta‐Isopropenylbenzyl Isocyanate (TMI) for Preparation of Ambient Cross‐linkable Latexes—Stability of NCO Groups in Latex Form

Single‐pack, ambient cross‐linkable acrylic latexes containing dimethyl meta‐ isopropenylbenzyl isocyanate (TMI) repeat units were prepared by batch and semicontinuous emulsion polymerization processes at 40°C using methyl methacrylate (MMA) and n‐butyl acrylate (BA) as the principal comonomers. The semicontinuous processes were used to prepare structured latexes in which the locus of functional groups within the particles was controlled. In some polymerizations, methacrylic acid (MAA) was incorporated at similar levels to TMI (2 and 5 wt%). An FT‐IR method was established for monitoring loss of isocyanate (NCO) groups during latex storage and was shown to give reliable values of rate coefficients. The results showed that NCO functionality was lost gradually over a period of 1–2 weeks depending on latex parameters. Inclusion of MAA repeat units increased the rate of loss of NCO groups by an order of magnitude when the TMI and MAA were uniformly incorporated. The rate also increased significantly on changing latex pH from acidic (pH 1–4) to basic (pH 9) using NaOH. Particle morphology and functional group location also were important. Loss of NCO groups was fast for core‐shell latexes in which the NCO groups were incorporated only in the shell (with more direct access to water from the continuous phase), but much slower when a core containing the TMI and MAA repeat units was protected from the continuous phase by an unreactive poly(MMA/BA) shell layer. The observations show that TMI‐containing latexes have a relatively short shelf‐life and emphasize the importance of casting films soon after latex preparation for optimum cross‐linking during film formation. Dedicated to Professor John L. Stanford on the occasion of his 60th birthday.

Chemical modification of polydienes in latex medium: Study of epoxidation and ring opening of oxiranes

AbstractReferring to previous work carried out in organic solvents, a study of the action of nucleophilic reagents on epoxidized units of 1,4‐epoxidized polyisoprene (synthetic polyisoprene or natural rubber) was performed in latex medium. Among the considered reagents, dialkylphosphate and ammonium diethyldithiophosphate demonstrated the ability to add under these reaction conditions on epoxidized units according to a SN2 substitution with an oxirane ring‐opening mechanism. A systematic study was performed with dibutylphosphate that was shown to be very reactive. Grafting of phosphorated groups along polyisoprene chains was carried out via reaction of the acidic function (P‐OH) of the phosphate with oxirane rings previously created on a 1,4‐polyisoprene backbone. The prominent role of latex pH on the reaction was shown. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 39–52, 2005

Immobilization of cationic polymer particles having active ester groups onto solid surfaces

Monodispersed cationic polymer particles with sulfonium groups and active ester groups at their surfaces were prepared by emulsifier-free emulsion copolymerization of styrene (ST) with a water-soluble active ester monomer, methacryloyloxyphenyldimethylsulfonium methylsulfate (MAPDS). The cationic polymer particle monolayers were fabricated on unmodified and aminated glass plates by electrostatic interactions and chemical reactions, respectively. The polymer particles were immobilized onto unmodified glass plates at relatively regular intervals in the absence of electrolytes, and the morphology of particle monolayers on the glass plates was changed with solid content of latex, electrolyte and cationic surfactant concentration. The polymer particles were immobilized onto aminated glass plate as aggregates by controlling the pH of latex and electrolyte concentration. Remaining active ester groups of the particle monolayers were confirmed to react easily with primary amino compounds.

Ribosomal and polyadenylated RNA content of rubber tree latex, association with sucrose level and latex pH

Poly(A) content of latex polysomes in tapped Hevea trees of different age and clonal origin varied from 0.1 μg to 0.5 μg ml −1 latex cytosol indicating poly(A) +RNA levels of 1.5 μg – 7.5 μg ml −1 and between 3% and 7.5% in proportion to rRNA. The level of rRNA was in the range 43 μg – 120 μg ml −1. The poly(A) +RNA exhibited a polydisperse sedimentation pattern with prominent peaks at 16 S, 20 S and 24 S, and an apparent mean size of 2270 nucleotides. Clonal differences in rRNA were significant and within different clonal trials were associated with variations in the level of latex sucrose and in latex pH suggesting an association with the activity of latex glycolysis. Level of polysomal poly(A), also in proportion to rRNA, was significantly higher in clone PB 217 than in clones GT 1 and PB 235 exhibiting much lower sucrose content of latex. Bark treatment with ethephon increasing latex pH, sucrose utilization and latex yield increased the levels of rRNA and particularly of poly(A) +RNA. This increase did not result in an increase of soluble proteins and may thus be concerned with synthesis of proteins bound to latex structures. Low levels of polysomes for cytoplasmic structure formation may be involved in association of low sucrose with latex vessel senescence.

Modification of pH of latex cytoplasm by ethylene

In the absence of glycolytic activity the pH of isolated latex cytoplasm of Hevea brasiliensis increases progressively during the first hours of incubation. This increase is greatly enhanced after bark treatment with 2-chloroethylphosphonic acid. The process of alkalization is not enzymic and is oxygen dependent. This observation is discussed in relation to the increase in latex pH in situ under hormone action.

Cinetique d'action de l'acide 2-chloro ethylphosphonique sur les polyribosomes du latex d' Hevea brasiliensis

Effects of 2-chloroethylphosphonic acid on the latex of Hevea brasiliensis were studied during 7 days after its application on the tapping panel of the tree. Ribosome polymerisation shows a dramatic rise within 12 hr after treatment. This shift is overcome at first without rRNA synthesis. Increase of latex production and latex pH exhibit similar features and start 24 hr after application of the, stimulant. After 4 days, rRNA concentration and the stability of the lutoïds (microvacuoles with lysosomal characteristics) change significantly.

Control of carbohydrate metabolism by ethylene in latex vessels ofHevea brasiliensis MUEL. ARC in relation to rubber production

The treatment of the bark of regularly tapped trees with 2-ohloroethylphosphonio acid (CEPA) in the long run brings down sucrose level in the latex even when latex production is not increased. The sucrose deficit thus caused persists for a number of months after the treatment probably due to the depletion of carbohydrate reserves by the stimulation. The loss of carbohydrates not related to an increase of rubber produotion grows as the concentrations of applied CEPA are raised. The treatment increases the activity of phosphoenolpyruvate (PEP) carboxylase and decreases pyruvate deoarboxylation in mitochondria-free oytoplasmic latex serum. The pyruvate deoarboxylase has a sharp optimum at pH 6.5 and is almost inactive at pH 7.5 while PEP oarboxylase, like invertase, has the optimum at weakly alcaline pH and is only slightly active at pH 6.5. The CEPA-induced changes in the activity of these enzymes are related to an increase of latex pH after the treatment. Consistently with this the evolution of CO2 from sugars catabolised in the serum was found to decrease with increasing pH. It is concluded that the observed ethylene-induced changes in enzyme aotivities bring about in latex vessels a deviation of the glycolysis-fed metabolio flux from synthetic pathways to mitochondrial oxidations and consequently a decrease in the efficiency of sucrose conversion to rubber.