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L64 EO/PO Block Polyether Defoamer

    • Product Name: L64 EO/PO Block Polyether Defoamer
    • Factroy Site: Lingwu, Yinchuan, Ningxia, China
    • Price Inquiry: sales2@liwei-chem.com
    • Manufacturer: Anhui Liwei Chemical Co,Limited
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    Specifications
    HS Code 195997
    Product Name L64 EO/PO Block Polyether Defoamer
    Chemical Type Ethylene oxide/propylene oxide block copolymer nonionic surfactant
    Appearance Colorless to light yellow transparent liquid at 25°C
    Active Content 100%
    Viscosity At 25 C 850 mPa·s
    Cloud Point 1 Percent Aqueous 58°C
    Density At 25 C 1.05 g/cm³
    Ph 1 Percent Aqueous Solution 6.5
    Solubility Soluble in water, ethanol, benzene, and chloroform

    As an accredited L64 EO/PO Block Polyether Defoamer factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.

    Packing & Storage
    Packing L64 EO/PO Block Polyether Defoamer is supplied in 200 kg polyethylene drums, sealed for safe handling and storage.
    Container Loading (20′ FCL) 20′ FCL: pack 80 drums (200L) or 20 IBCs on pallets, secure properly, moisture-proof.
    Shipping L64 EO/PO Block Polyether Defoamer ships in sealed drums, IBCs, or bulk tankers to prevent contamination and moisture ingress. Use clean, dry equipment, avoid extreme temperatures, and secure loads properly. Standard non-hazardous chemical handling applies; ensure labeling and documentation comply with local transport regulations.
    Storage Store L64 EO/PO Block Polyether Defoamer in a tightly sealed container in a cool, dry, well-ventilated area away from direct sunlight, heat sources, and moisture. Keep away from strong oxidizers or acids. Avoid extreme temperatures. Under proper conditions, shelf life is typically one year. Stir or mix gently before use if stratification occurs.
    Shelf Life Shelf life is 24 months when stored sealed in a cool, dry place, protected from extreme temperatures and contamination.
    Application of L64 EO/PO Block Polyether Defoamer
    Dissolved oxygen depletion in a 5,000 L stirred-tank bioreactor after 38–42 hours of fed-batch culture triggers a measurable decrease in specific growth rate. Foam accumulation at the gas-liquid interface of fermentation broth—particularly in cultures producing extracellular proteins or polysaccharides—reduces working volume utilization by 15–25% when uncontrolled, and forces premature harvest of the batch. L64, a difunctional EO/PO block polyether with a polypropylene oxide core of approximately 30 repeat units flanked by polyethylene oxide blocks totaling approximately 26 repeat units (nominal molecular weight 2900 g/mol; EO content 40–50% w/w; HLB 12–15), exhibits an inverse solubility profile that is operationally significant under fermentation thermal conditions. The defoamer remains molecularly dispersed in the aqueous broth below its cloud point of approximately 61°C (1% aqueous solution, DIN 53917), but at typical upstream processing temperatures of 30–37°C the amphiphilic chains adsorb at air-water interfaces and displace foam-stabilizing protein films via a bridging-dewetting mechanism. Published data for this specific configuration is limited, but the surface tension reduction measured by the du Noüy ring method at 0.1% w/w addition in deionized water is consistently reported in the range 39–43 mN/m versus approximately 72 mN/m for pure water at 25°C. The practical dosing window for anti-foam control in bacterial fermentation falls between 0.01% and 0.1% w/w relative to the broth volume, with higher concentrations above 0.15% w/w frequently exhibiting no incremental foam suppression and increased risk of coalesced oil-like droplets that foul sterilizing filters downstream. Addition must follow sterile filtration through 0.2 µm hydrophobic PTFE membrane cartridges under aseptic conditions when the defoamer enters post-sterilization stages. Critical operational boundaries include the following: preautoclaving a dilute aqueous dispersion (1–2% w/w) of L64 at 121°C for 20–30 minutes may cause phase separation upon cooling if the solution is not re-homogenized by agitation; storage below 10°C produces gel-like viscosity increase that complicates peristaltic metering pump prime cycles at dosing rates below 0.5 mL/min; and combination with silicone-based defoamers in the same fermentation vessel generates mixed-foam destabilization behaviour that is unpredictable under sterile sampling constraints. In continuous fermentation configurations with dilution rates of 0.05–0.10 h⁻¹, continuous defoamer feed at 0.005–0.02% w/w relative to fresh medium feed rate is preferred over bolus dosing to avoid fluctuations in interfacial tension that alter oxygen mass transfer coefficient kLa by up to 8–12% following each slug addition. Dissolved oxygen probes (polarographic, membrane-covered Ag/Pt electrodes compensated at 37°C) register transient drops during foam collapse events, and process control algorithms must account for this signal noise when cascade loops adjust agitation and airflow. The use of L64 in downstream purification must account for residual carryover into microfiltration retentate, where concentrations above 50–100 ppm may interfere with tangential flow filtration membrane flux and require diafiltration volumes exceeding 5–7 times the concentrate volume for clearance.Emulsion polymerization presents a process window where the interaction between the EO/PO block polyether and charged latex particles determines both foam control efficacy and final dispersion stability. L64 competes with anionic emulsifiers (sodium lauryl sulfate, alkylbenzene sulfonates) for interfacial area but does not substitute for them in particle nucleation. In a seeded semi-batch vinyl acetate-co-butyl acrylate polymerization conducted in a 2,000 L glass-lined reactor with jacket temperature control at 72±2°C, foam generated during delayed monomer feed is controlled at L64 concentrations of 0.05–0.15% w/w relative to the total monomer charge. Addition above 0.20% w/w depresses the glass transition temperature of the dried film by 2–4°C due to plasticization from the polyether backbone, measured by differential scanning calorimetry per ASTM D3418. Published data for this specific configuration is limited, but the mechanism is attributed to the polypropylene oxide segment's miscibility with poly(vinyl acetate) domains, and the consequent migration of unreacted polyether to the film-air interface during coalescence. The practical targeting protocol involves pre-dispersing the defoamer in a portion of the aqueous phase containing the nonionic secondary emulsifier prior to pre-emulsion homogenization at 3,000–5,000 rpm using a rotor-stator mixer. Foam control in the reactor headspace is monitored by differential pressure transducers positioned at the condenser inlet; excursions above 50 mbar differential activate automatic defoamer dosing through diaphragm metering pumps sized for 10–50 mL per actuation. Residual monomer stripping at 60–65°C under vacuum (200–300 mbar absolute) represents the highest foam-pressure segment of the cycle, and L64's cloud point behaviour means defoaming efficacy improves slightly as the dispersion temperature approaches 55°C but may decrease again in post-stripping cooling to 40°C. In latex formulations destined for pressure-sensitive adhesive coatings conforming to ISO 13007 and EN 12004 adhesion classifications, residual L64 levels must be confirmed by gel permeation chromatography with refractive index detection to remain below 0.1% w/w on dry film, because higher levels alter surface tack development curves and open-time measurements according to ASTM D3654/ASTM D3654M.Central sump charging at coolant concentrations between 5.0% and 7.5% v/v generates stable microfoam that remains suspended for over 6 hours in the absence of mechanical breakage. This foam—entrained air dispersed in the aqueous metalworking fluid phase—reduces the effective lubricating film thickness at the tool-workpiece interface and accelerates microbial proliferation in the sump. In water-miscible metalworking fluids formulated with triethanolamine, petroleum sulfonates, and boric acid esters, L64 dosing at 0.02–0.08% w/w relative to the total fluid volume destabilizes foam in central circulation systems equipped with low-pressure (0.5–1.0 bar) gear pumps delivering 200–400 L/min to machining centers. The defoamer's action is most pronounced at sump temperatures of 25–40°C; at temperatures above 50°C the polyether approaches its cloud point in the brine phase and loses hydrophilic anchoring, which paradoxically reduces defoaming performance in high-speed grinding operations where sump temperatures routinely exceed 55°C. Foam height assessment per ASTM D892 (Sequence I, II, III) using the air-blower method at 24°C and 94°C provides a comparative benchmark: control emulsions without defoamer typically exceed 180 mL foam height at the end of the blowing period, while formulations containing 0.05% w/w L64 remain below 40 mL under identical conditions at 24°C, with performance degradation at 94°C attributed to cloud point inversion. Published data for this specific configuration is limited. An operational concern arises when the same central sump serves both high-speed and low-speed operations: the concentration window narrows because high-speed broaching (cutting speeds above 60 m/min) requires faster foam collapse kinetics than the diffusional adsorption rate of the polyether permits at concentrations below 0.03% w/w, while concentrations above 0.08% w/w produce torque reductions on forming taps measured in dedicated tapping torque test rigs (ASTM D5619) that exceed 10% and indicate boundary lubrication film displacement. Compatibility with tramp oil separation systems using coalescing plate packs or dissolved air flotation must be validated case-by-case, because the EO/PO block polyether reduces oil droplet coalescence rates and may divert emulsified tramp oil carryover into the cleaned fluid stream.

    Jet Dyeing Machine Foam Collapse and Crease Prevention Under High-Shear Liquor Circulation

    High-shear liquor circulation at jet dyeing machines equipped with variable-speed main pumps operating between 2.5 and 4.0 bar nozzle pressure entrains air at a rate proportional to fabric linear velocity. Polyester and polyamide knitted substrates processed at rope speeds of 250–450 m/min generate foam volumes that exceed the machine's internal overflow capacity within 10–15 minutes when the dyebath contains anionic leveling agents, dispersants, and electrolyte at 10–30 g/L sodium sulfate. L64 added directly to the dyebath preparation tank at 0.05–0.15 g/L (relative to total bath volume) suppresses foam throughout the heating phase to 130°C in high-temperature beam and jet machines conforming to ISO 105 color fastness testing protocols. The polyether's defoaming mechanism in this application relies on its limited solubility in the heated electrolyte solution; as bath temperature rises above the salting-out threshold determined by the Hofmeister series effect of sulfate ions, the polymer partitions away from bulk solution and accumulates at the rapidly generated air-water interface, rupturing foam lamellae via film drainage acceleration. In practice, the critical addition window in the heating programme is between 60°C and 90°C: below 60°C the reaction between the polyether and the dyebath surfactants produces weak interfacial adsorption, while above 90°C the approaching cloud point promotes partial agglomeration that may deposit on the fabric as low-level spotting detectable only with fluorescent tracer microscopy. Post-dyeing reduction clearing baths that employ sodium hydrosulfite at 3–5 g/L and caustic soda at 2–3 mL/L at 70–80°C exhibit renewed foaming because the reducing agent degrades residual polyether chains via ether cleavage at the EO-PO junctions, reducing effective concentration by 30–50% within 60 minutes. Dosing strategy must therefore include a post-clearing top-up of 0.02–0.05 g/L based on visual inspection or optical foam sensors installed at the machine's drain overflow. Consequences of overdose above 0.2 g/L include deposition on hydrophobic substrates (unmodified polyester at low uptake sites) that may interfere with subsequent finishing pad application and produce uneven water repellency measured by ISO 4920 spray test ratings lower than 4 on the 0–5 scale. The interaction of L64 with silicone-based softeners in the same bath is strongly antagonistic: combined use at neutral pH forms an aggregated complex that exhibits neither defoaming nor softening effects and may clog the nozzle filter screens at 50–80 µm mesh.Sugar beet diffusion towers operated under countercurrent extraction conditions at 70–75°C generate persistent foam at the raw juice collection trough. This foam volume frequently exceeds 20% of trough headspace during high-pectin campaigns in late season beets stored longer than 30 days. L64, when metered as a diluted 1–3% w/w aqueous solution into the raw juice trough at 2–10 ppm relative to juice flow rate, reduces foam headspace to below 5% within 3–5 minutes of injection, measured by level probes with analogue output. The block polyether operates in this medium at temperatures near its cloud point, which produces rapid phase separation and enhanced film rupture at the pectin- and raffinose-stabilized foam interfaces. The principal compatibility consideration in sugar processing is the downstream liming and carbonation stages: residual polyether at ppb-to-ppm levels does not interfere with calcium carbonate precipitation at 80–85°C (ISO 10531 juice purity determination), but concentrations in excess of 20 ppm in the thin juice may reduce evaporator heat transfer coefficients by 3–5% due to surface film modification on falling-film tubes. Published data for this specific configuration is limited. Analogous application in potato flume water (15–25°C, starch concentration 0.5–2.0% w/w) uses intermittent dosing controlled by foam sensor activation, with typical daily consumption rates of 0.01–0.05 kg per tonne of raw potatoes processed. Regulatory clearance for such food-processing aid applications requires compliance documentation per relevant national food law; in the United States, polyether clearance status for indirect uses is evaluated under 21 CFR Parts 175–178, while direct addition allowances for Poloxamer 184 in designated food categories appear in 21 CFR 172.808 with prescribed maximum concentrations that are ingredient-specific and must be verified against the current published regulation before commercial use.

    When Cooling Tower Blowdown Contains High Chloride and BOD Loading Before Biosolids Clarification

    Chlorinated blowdown discharge containing residual quaternary ammonium compounds produces stable foam blankets on cascade aerators. In industrial wastewater treatment facilities receiving mixed streams from metal finishing operations where chloride concentrations reach 800–1,200 mg/L and BOD₅ loading per ISO 5815-1 ranges from 300 to 600 mg/L, surface foam depth at the aeration basin can exceed 0.5 m, impairing UV disinfection transmittance and staff safety at open tank perimeters. L64 applied via chemical metering pumps into the aeration basin influent at a continuous dose of 5–15 ppm relative to flow rate collapses the foam blanket within 20–40 minutes and maintains foam depth below 50 mm at subsequent monitoring intervals per 24-hour sampling cycles. The defoamer functions under these conditions by displacing the quaternary ammonium compounds from the air-water interface; the polyether's lower equilibrium surface tension (39–43 mN/m at 0.1% w/w compared to approximately 30–35 mN/m for benzalkonium chloride at equivalent concentration) ensures preferential adsorption despite the cationic surfactant's electrostatic repulsion. However, a distinct constraint applies: in activated sludge systems operating at mixed liquor suspended solids concentrations of 3,000–5,000 mg/L (ISO 11923-1), daily dosing above 20 ppm leads to detectable polyether accumulation on sludge flocs, increasing sludge volume index by 10–15% and reducing settled sludge compaction in secondary clarifiers. Biodegradation testing according to OECD 301B (modified Sturm, CO₂ evolution) indicates that the block polyether is inherently biodegradable but not readily biodegradable; the test endpoint typically shows 20–35% mineralization in 28 days, which means total system removal depends heavily on sludge adsorption and subsequent anaerobic elimination in digesters. In sequencing batch reactors with hydraulic retention times below 8 hours, intermittents dosing should be triggered by surface foam sensors rather than continuous feed to prevent polyether accumulation, with maximum daily dosage capped at 0.5% of the total influent COD mass.

    Stock Preparation Foam Tolerance Data in Neutral Sulfite Semichemical Pulping

    In neutral sulfite semichemical pulping, black liquor dissolved solids exceed 12% w/w at the recovery evaporator inlet. Foam generation during brown stock washing at 60–70°C and pH 7.5–8.5 interferes with vacuum drum washer operation, where stable foam blankets at the washer hood reduce washing efficiency by as much as 15–20% and increase chemical oxygen demand carryover into the bleach plant. L64 is dosed directly into the washer shower water at 10–30 ppm relative to the shower water flow rate. The block polyether's cloud point in the high-electrolyte pulping liquor drops well below the process temperature, so the defoamer continuously exists in a phase-separated, finely dispersed state—this property enhances foam film destabilization at the liquor-vacuum interface but also poses a deposition risk on press felt surfaces if dosed above 50 ppm over extended production runs exceeding 8 hours. Machine trials on a 2.5 m-wide vacuum drum washer at 12–15 rpm drum speed demonstrated that foam thickness at the hood, measured by ultrasonic level transmitters calibrated to the washer geometry, remains below 20 cm at doses of 15–20 ppm, compared to uncontrolled foam heights that exceed 60 cm and trip high-level alarms. The defoamer also suppresses foam in subsequent weak black liquor storage tanks where entrained air reduces tank effective capacity by 10–30%; injection into the liquor transfer line at 5–10 ppm addresses this volume loss without affecting evaporator boiling point rise measurable across a 5-effect falling-film evaporator train. Compatibility with black liquor combustion chemistry in the recovery boiler has been validated in mill trials, but the long-term effect of polyether-derived sodium carbonate on smelt bed properties requires further site-specific confirmation. In the bleach plant, residual L64 carryover at 1–5 ppm does not measurably consume chlorine dioxide dose at the D0 stage, as verified by residual oxidant titration per TAPPI T 700 standards. Regulatory status for pulp and paper defoamers used in process water: the material must be assessed under relevant national effluent guidelines (e.g., US EPA Effluent Limitations Guidelines for the Pulp, Paper and Paperboard Point Source Category, 40 CFR Part 430) and any discharge permit conditions specified in the National Pollutant Discharge Elimination System permit.
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    Certification & Compliance
    More Introduction

    L64 EO/PO block polyether defoamer is a nonionic triblock copolymer with the arrangement poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide), CAS 9003-11-6. In compendial references, the same polymer architecture is described as Poloxamer 184 when manufactured under pharmaceutical controls, although defoamer-grade L64 is not automatically of compendial purity. The product is supplied as a 100% active liquid with no carrier oil, silicone fluid, or hydrophobic silica. Representative technical-bulletin values include an average molar mass of 2900 g/mol, an oxyethylene content near 40 wt%, an HLB value of approximately 15, and a pour point near 18 °C. These properties place L64 between low-foaming wetting agents and strongly hydrophobic droplet defoamers; it is water-dispersible at ambient temperature and converts to a dispersed defoamer phase near its cloud point.

    Specifications vary by manufacturer and by lot; the values presented here are not a certificate of analysis. The receiving process should verify lot-specific cloud point, viscosity, and residual ethylene oxide against the operating window before transfer into production.

    How Does the EO/PO Block Architecture Govern Defoaming and Deaeration?

    The block arrangement creates a temperature-sensitive amphiphile. The central poly(propylene oxide) block is hydrophobic and promotes adsorption at air-water and oil-water interfaces. The terminal poly(ethylene oxide) blocks hydrate in water and provide steric stabilization. At low temperatures below the cloud point, the polymer is largely water-soluble and behaves more as a low-foaming nonionic surfactant than as a droplet defoamer. As the solution temperature rises, hydration of the oxyethylene chains decreases. At the 1 wt% aqueous cloud point of approximately 60 °C measured by ISO 1065:1991, the copolymer separates into dispersed colloidal aggregates that spread at foam film interfaces, displace protein or surfactant films, and produce rapid bubble coalescence.

    The molar mass of 2900 g/mol is sufficiently low for fast diffusion from the bulk to freshly generated bubble surfaces in high-shear mixing equipment, but high enough to form an interfacial layer with reduced surface elasticity relative to typical anionic or protein-stabilized lamellae. In Ross-Miles foam testing according to ISO 696:1981, L64 can be evaluated at 0.05–0.20 wt%; the resulting foam-height reduction is strongly influenced by water hardness, temperature, and the molecular mass of the foam-stabilizing surfactant. Published data for this specific configuration is limited; laboratory screening under the receiving process conditions is required before setting a control limit.

    In recirculating aqueous metalworking and spray-washing systems, L64 is introduced upstream of high-shear pumps or spray nozzles at 0.01–0.10 wt% of the working fluid volume to suppress air entrainment and line foam. As a nonionic polyether, it does not add hardness-sensitive anionic charge and is compatible with many boramide and sulfonate-loaded semisynthetic oil packages. The operational boundary is thermal: above 60 °C the polymer can separate onto tank walls and heat-exchanger surfaces, reducing the active bulk concentration and creating an organic film that can retain metal fines. Below 40 °C L64 remains substantially soluble and may behave as a low-foaming surfactant rather than as a strong antifoam. This temperature-dependent transition means a cold make-up stream can reduce defoamer efficiency even when the bulk bath temperature is within specification.

    Cloud-Point Defoaming Is Not a Universal Mechanism

    The defoaming mode of L64 is strongly temperature-concentration dependent. In oil-free aqueous systems such as waterborne paints and adhesives, the polymer is typically fully soluble at room temperature and therefore does not provide the same rapid macrofoam knockdown as dispersed hydrophobic droplet defoamers. Instead, L64 accelerates air release from low-viscosity liquids during blending and transfer but may not control persistent foam in high-viscosity, high-surfactant, or protein-loaded formulations. When a formulation is processed at 50–65 °C, the copolymer approaches its cloud point and develops heterogeneous droplet character; defoamer strength rises. This effective processing window is often only 10–15 °C wide for a given concentration. Outside that window, the product either dissolves and loses droplet character or fully precipitates and loses uniform distribution.

    This behavior differs from silicone emulsion defoamers, which operate as insoluble low-surface-energy droplets across a wider temperature range. L64 requires the operating temperature and addition level to be balanced so that the process point is near the cloud point without exceeding it. For sustained process temperatures above 70 °C, higher-cloud-point EO/PO block copolymers or silicone-based chemistries are usually substituted. Evaporative surface cooling can create a 5–10 °C difference between the bulk liquid and the foam-film surface; this gradient should be measured or estimated before selecting the cloud-point target.

    Specification Ranges and Physical Characterization

    Property Representative value or range Test basis
    Average molar mass 2900 g/mol Supplier certificate; hydroxyl number
    Oxyethylene content 40 wt% NMR or supplier method
    HLB 15 Griffin calculation
    Cloud point, 1 wt% in water 58–62 °C ISO 1065:1991
    Dynamic viscosity at 25 °C 800–900 mPa·s ISO 2555 Brookfield
    Density at 25 °C 1.05–1.07 g/cm³ ASTM D891
    Pour point 18 °C Supplier method
    Water content ≤0.5 wt% Karl Fischer titration

    Because L64 is a polymeric distribution rather than a single molecular species, molar mass, cloud point, and viscosity are lot-dependent variables. Storage below the pour point can create waxy solids. Controlled warming to 25–35 °C and gentle recirculation are recommended before dosing. Direct steam sparging or localized electric band heaters above 80 °C are not recommended because oxidative degradation can shift the cloud point and reduce defoamer activity.

    In waterborne architectural coatings, L64 is evaluated as a grind-stage and letdown-stage deaerator at 0.05–0.20 wt% on total formulation. Unlike mineral oil defoamers, it introduces no distillate hydrocarbon phase and does not create an oily surface film on tinted bases. Unlike silicone defoamers, it reduces the risk of silicone-induced cratering in subsequent topcoats. However, L64 is not a direct replacement for hydrophobic particle defoamers in all low-VOC formulations. In high-airless-spray and high-freeze-thaw systems, L64 alone may not retain foam control after 28 days of shelf aging. Foam persistence should be measured under ASTM D3601 or an equivalent foam-in-aqueous-media test, and dried-film defects should be evaluated by drawdown and immersion. Above 0.30 wt% on total formulation, the hydrophilic polyether can increase dried-film water sensitivity; water-immersion testing according to ASTM D870 is used to identify this threshold.

    Comparative Defoamer Class Boundaries

    Defoamer type Active carrier Representative use level Primary advantage Primary limitation
    L64 EO/PO block polyether 100% polyether 0.05–0.20 wt% Non-silicone, water-dispersible, no hydrocarbon film Cloud point near 60 °C; overdose may increase film water sensitivity
    Silicone emulsion 10–30% polydimethylsiloxane/silica 0.001–0.02 wt% Very low use level; broad temperature range Potential cratering, silicone carryover, overcoat adhesion loss
    Mineral oil defoamer Hydrocarbon oil, hydrophobic silica/wax 0.10–0.50 wt% Cost-effective in wastewater and oil-containing systems Oil film, VOC contribution, incompatibility with clear aqueous systems
    Higher-MW EO/PO block copolymer 100% polyether 0.05–0.20 wt% Higher cloud point for hot processes Higher viscosity; slower film spreading

    The use levels in this table are industrial ranges observed in aqueous surfactant-laden systems and are not a substitute for dose-response testing in the target formulation. When silicone carryover is the controlling constraint, L64 may be selected even though its volumetric dose is higher. When process temperature exceeds 65 °C, higher-cloud-point EO/PO block copolymers or silicone emulsions may be selected despite their own residue constraints.

    When Fermentation Broth Foaming Restricts Oxygen Transfer

    Aerobic fermentation processes that release extracellular proteins, polysaccharides, or surfactants often generate stable proteinaceous foam that reduces working volume and blocks exhaust filters. L64 is used as an antifoam at 0.025–0.10 wt% of initial broth mass. In stirred-tank fermentors equipped with Rushton or pitched-blade impellers, addition is frequently made before sterilization to distribute the block copolymer through the medium. During heat sterilization at 121 °C, L64 can temporarily phase-separate because the process temperature is above the cloud point; after cooling to the fermentation set point, it usually redisperses. Vessel geometry, headspace pressure, and sparger type change the effective antifoam requirement, so fixed-dose recommendations are unreliable without pilot data.

    Compared with silicone-based fermentation antifoams, L64 does not introduce silicon-containing residues that can foul tangential-flow filtration membranes or anion-exchange chromatography resins in downstream purification. The trade-off is a higher effective dose than silicone emulsions, and an excessive polyether level can reduce the volumetric oxygen transfer coefficient by accumulating at the gas-liquid interface. Foam control in protein-rich broth is not linear with dosage: underdosing may leave a stable protein film at the liquid surface, while overdosing may slow oxygen transfer even when visible foam is absent. The gassing-out method for volumetric kLa measurement and foam-height recording under production aeration should be used to separate these effects.

    In paper machine whitewater and neutral pH retention systems, L64 is dosed at 2–20 mg/L of process water to control foam formed by wood resin soaps and polymeric wet-strength additives. The product does not contribute mineral oil to felt conditioning or wire deposits. Above 45 °C in closed water loops, the operating point may approach the cloud point, and defoamer activity shifts from a soluble surfactant to a dispersed droplet. The difference from oil-based defoamers is most apparent after shutdown: there is no floating hydrocarbon layer in chests or seal pits, and wash-up does not require solvent-based cleaning. This makes L64 suitable for mills that cannot release oil-contaminated whitewater to the effluent treatment plant without additional treatment.

    What Limits Shelf Stability and In-Circuit Compatibility?

    L64 is not compatible with strong oxidizing acids, concentrated hydrogen peroxide, or chlorinated disinfectants; these reagents attack the polyether chain and can generate viscous oxidation products. In water-treatment and metalworking systems where sodium hypochlorite shock dosing is used, L64 should be injected downstream of the oxidant feed point to prevent localized degradation. The pour point of 18 °C means that outdoor storage in unheated tanks can cause solidification. Partially melted product can show concentration gradients within the drum because the waxy solid and liquid fractions may differ in oxyethylene distribution. For uniform dosing, the material should be warmed to 25–35 °C and homogenized before transfer.

    In latex and dispersion systems, L64 can interact with associative thickeners. Hydrophobically modified ethoxylated urethane thickeners may compete for hydrophobic latex particle surfaces, leading to wet-state viscosity drift when L64 is overdosed. Rheological verification by Brookfield rotational viscometry at 25 °C is advised after any formulation change. If viscosity loss exceeds the target range, the defoamer dose should be reduced or a lower-HLB polyether defoamer evaluated.

    Defoamer-grade L64 is not automatically a direct food additive or pharmaceutical excipient. Uses in drug manufacture or pharmaceutical fermentation require a compendial Poloxamer 184 grade with batch-specific residual ethylene oxide, dioxane, and heavy metals data. Food-contact and potable-water applications require confirmation against applicable positive lists or national approvals. Unless specified in the supplier certificate, industrial defoamer grade is handled as a technical chemical under the receiving site’s GHS program and should not be used in applications where migration into the final dosage form is not controlled.