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PET, TPU, and PA compounds are used in films, monofilaments, footwear, hoses, cable sheathing, automotive parts, electrical components, and engineering plastics. Exposure to moisture, heat, hot water, or humid aging can gradually reduce their performance, but the degradation mechanism is not identical in every polymer. Selecting a Carbodiimide Anti-Hydrolysis Agent therefore requires more than matching an additive to a general resin category. Compounders must consider polymer chemistry, processing temperature, moisture control, formulation components, physical additive form, and the properties that must remain stable after aging.
PET, TPU, and PA compounds have different hydrolysis risks and selection requirements.
PET compounds generally require control of ester hydrolysis, intrinsic viscosity, melt behavior, and carboxyl end groups.
TPU selection depends heavily on whether the material is polyester-based or polyether-based.
PA compounds require evaluation of moisture absorption, dimensional change, reinforcement content, and mechanical retention.
Powder, liquid, and masterbatch forms must be matched to the production and feeding process.
Selection should be confirmed through real processing trials and application-relevant aging tests.
Carbodiimide chemistry can protect polymers containing ester, urethane, or amide-related structures, but that broad compatibility does not make all grades interchangeable. PET is a polyester whose molecular weight, intrinsic viscosity, and melt viscosity can decline when moisture promotes ester-bond cleavage. Polyester-based TPU also contains hydrolysis-sensitive ester segments, but failure is often observed through reduced elongation, flexibility loss, cracking, or lower durability.
PA behaves differently because its amide structure attracts and absorbs moisture. Moisture can alter dimensions, stiffness, impact response, and other mechanical properties before severe chain degradation becomes obvious. These different failure patterns mean that compounders must define the most relevant performance indicator before comparing stabilizer candidates.
Processing conditions create another important difference. PET is commonly processed at temperatures where insufficient drying can accelerate molecular-weight loss during extrusion or molding. TPU requires controlled drying and a thermal history that avoids damaging elasticity, color, or surface quality. PA6, PA66, modified nylon, and reinforced PA grades may run at different temperatures and contain glass fiber, flame retardants, pigments, or mineral fillers.
A useful carbodiimide stabilizer for compounds must therefore fit both the polymer chemistry and the complete production environment. A general anti-hydrolysis buying guide may help identify broad product categories, but it cannot replace compound-specific compatibility, processing, and aging tests.
PET hydrolysis cleaves ester linkages and creates shorter polymer chains with additional acid and hydroxyl end groups. As degradation progresses, compounders may observe lower intrinsic viscosity, reduced melt viscosity, weaker mechanical performance, brittleness, or unstable processing. Carboxyl end groups deserve particular attention because they can contribute to further hydrolysis, especially during humid or high-temperature exposure.
Processing-related degradation may begin before the finished part enters service. Residual moisture, excessive residence time, repeated heat histories, or poorly controlled recycled content can reduce molecular weight during extrusion or injection molding. A PET anti-hydrolysis agent should consequently be assessed for reactivity toward acid end groups, stability at the actual melt temperature, and its effect on viscosity retention.
Relevant PET applications include film, BOPET film, monofilament, sheet, injection-molded parts, packaging, fiber, and engineering compounds. The selection criteria may differ across these applications. Film and sheet production may require strong control of surface quality, transparency, haze, gels, and die deposits, while monofilament and molded parts may place more emphasis on tensile retention, toughness, and long-term humid-heat durability.
Physical form is an important part of PET selection. A PET-based PET Hydrolysis Masterbatch can simplify gravimetric feeding and help distribute the active ingredient through a compatible polyester carrier. The selected carrier should not introduce an incompatible polymer, unwanted haze, surface defects, or an unacceptable change in crystallization behavior.
Carbodiimide reactivity should be balanced against processing stability. A highly reactive additive may control acid-related degradation effectively, but it must still survive compounding temperatures and distribute evenly through the PET melt. Compounders should also assess whether the selected grade changes color, odor, viscosity, pressure, filtration behavior, or surface appearance.
A PET trial should include a blank formulation and several candidate dosage levels processed under identical drying, residence-time, and temperature conditions. Measure intrinsic viscosity or another suitable melt-viscosity indicator before and after processing. Record tensile strength, elongation, appearance, extrusion pressure, and melt stability.
Acid value or carboxyl end-group testing can help determine whether the carbodiimide stabilizer is controlling an important source of further degradation. Humid-heat aging should reproduce the expected application environment, while hot-water or pressure-aging tests may be useful for demanding monofilament and engineering applications. Film trials should additionally examine haze, surface defects, gels, and visual uniformity.
The first question is whether the TPU is polyester-based, polyether-based, or built around another soft-segment chemistry. Polyester TPU is generally more vulnerable to hydrolytic attack because water can cleave ester bonds within its soft segments. Polyether TPU usually offers stronger hydrolysis resistance, although its formulation and service conditions still need to be evaluated rather than assumed safe.
Hydrolysis in TPU may appear as molecular-chain scission, reduced tensile strength, lower elongation, flexibility loss, surface cracking, or reduced durability in hot water and humid environments. Selecting a TPU anti-hydrolysis agent without identifying the base chemistry can result in an unsuitable dosage, unnecessary additive cost, or inadequate long-term protection.
TPU is commonly used in footwear, hoses, cable sheathing, films, sheets, pipes, seals, and molded parts. These applications often rely on elongation, rebound, softness, surface quality, and resistance to repeated flexing. The Carbodiimide Anti-Hydrolysis Agent must support durability without creating an unacceptable increase in hardness, changing color, or reducing flexibility.
Moisture remaining in TPU or other formulation components should be controlled before processing because an additive is not a substitute for correct drying. Plasticizers, flame retardants, pigments, lubricants, fillers, and recycled content may also affect dispersion or introduce additional moisture.
The Carbodiimide Anti-Hydrolysis Agent should therefore be checked for compatibility with the complete TPU formulation, not only with neat resin. Powder and masterbatch forms may both be practical, depending on the feeding system, carrier compatibility, required dosage accuracy, and production scale.
Initial tensile results alone can hide future hydrolysis problems. A practical TPU program should compare tensile-strength retention, elongation retention, hardness change, color, surface cracking, and processing stability after exposure. Hot-water immersion is useful for parts expected to contact water directly, while humid-heat aging better represents warm and moisture-rich storage or service conditions.
Specimens should be examined at several aging intervals because two formulations may perform similarly at the beginning but diverge after longer exposure. Processing records should include melt behavior, extrusion pressure, strand quality, surface appearance, odor, plate-out, and any change in flexibility after molding or extrusion.
PA6, PA66, and modified PA compounds do not share one universal moisture response. Water enters the polymer and interacts with the amide-rich structure, potentially causing swelling, dimensional change, plasticization, stiffness reduction, and altered strength or impact behavior. The magnitude depends on the nylon grade, crystallinity, specimen geometry, conditioning history, temperature, and exposure time.
A PA nylon hydrolysis stabilizer must therefore be selected within a clearly defined conditioning and aging procedure. Otherwise, changes caused by normal moisture absorption may be confused with permanent hydrolytic degradation, making candidate comparisons unreliable.
Typical applications include automotive nylon parts, electrical and electronic components, reinforced PA compounds, industrial molded parts, connectors, housings, and high-temperature functional components. These products may need to retain dimensions, stiffness, strength, impact resistance, surface quality, and electrical properties after moisture exposure.
Glass fiber, minerals, flame retardants, impact modifiers, pigments, and heat stabilizers make PA selection more complex. Reinforcements can reduce or redirect dimensional movement, but interfaces between the fiber and polymer may become another location where moisture affects long-term performance.
Some powdered additives or fillers may carry moisture into the extrusion line, while high processing temperatures can narrow the stabilizer’s usable thermal window. The selected Carbodiimide Anti-Hydrolysis Agent must disperse adequately without disrupting reinforcement wet-out, surface finish, flame-retardant performance, or the balance of stiffness and impact resistance.
PA specimens should be measured in both dry-as-molded and moisture-conditioned states. Tensile strength, impact strength, dimensions, weight change, surface quality, and relevant electrical properties can then be compared before and after humid-heat aging.
Thermal aging may also be necessary for automotive, electrical, and high-temperature functional components, but it should be separated from hydrolysis testing so the main degradation driver remains identifiable. A successful stabilizer improves retained properties without creating unacceptable changes in processing, appearance, or another required function.
Factor | PET Compounds | TPU Compounds | PA Compounds |
|---|---|---|---|
Main concern | IV loss, ester hydrolysis, and acid end groups | Flexibility loss and polyester TPU hydrolysis | Moisture absorption and mechanical retention |
Key chemistry | Polyester | Urethane with polyester or polyether segments | Polyamide |
Common form | Powder or compatible masterbatch | Powder or compatible masterbatch | Powder or validated formulated type |
Processing focus | Drying, melt viscosity, and temperature | Moisture, heat history, and flexibility | Moisture and high processing temperature |
Key tests | IV, tensile properties, and humid aging | Elongation, hardness, and hot-water aging | Dimensions, impact, and mechanical retention |
Typical applications | Film, monofilament, sheet, and molded parts | Footwear, hoses, cables, film, and seals | Automotive, electrical, and engineering parts |
Powder offers formulation flexibility and is practical for laboratory screening or production lines with accurate loss-in-weight feeding and effective dispersion. KSTO’s Carbodiimide Powder is a monomeric product intended for polymer systems including PET, TPU, and PA.
Powder must remain protected from moisture and should be evaluated for dust handling, melting behavior, dispersion, and local overconcentration. Poor feeding accuracy can produce inconsistent stabilization even when the carbodiimide chemistry is suitable.
Liquid forms are generally more suitable for compatible polyol, adhesive, coating, dispersion, or accurately metered liquid systems. Their use in thermoplastic compounds should not be assumed. Compatibility with the base resin, other additives, processing temperature, and feeding equipment must be confirmed.
The company’s Liquid Polycarbodiimide is a polymeric liquid grade intended for systems that benefit from easy incorporation. Any thermoplastic application should still be validated under real compounding conditions.
Masterbatch is often convenient for continuous extrusion or molding because the active ingredient is already distributed in a carrier. Production teams may obtain more stable feeding and cleaner handling than with a low-dose powder.
Carrier compatibility remains critical. The carrier must suit the base polymer, processing temperature, optical requirements, mechanical targets, crystallization behavior, and final application. A convenient masterbatch can still produce poor results if its carrier changes the compound’s surface, color, flexibility, or long-term performance.
Glass fiber, mineral fillers, pigments, flame retardants, plasticizers, lubricants, and recycled resin can affect moisture level, acidity, dispersion, residence time, and the amount of Carbodiimide Anti-Hydrolysis Agent required. These components may also change the apparent effectiveness of a stabilizer by introducing new failure modes that are unrelated to hydrolysis.
Recycled PET may have a different molecular-weight and end-group profile from virgin PET. A filled PA compound may respond differently from an unfilled grade because of reinforcement interfaces, altered crystallization, and different moisture paths. A flame-retarded TPU may impose additional thermal or compatibility constraints that are absent from a natural-color formulation.
Fillers and powders can also introduce moisture when they are not dried or stored correctly. Plasticizers may change additive mobility, while pigments and lubricants may affect dispersion or surface appearance. Screening a carbodiimide stabilizer only in neat resin can therefore produce a result that does not transfer to commercial production.
Identify the exact polymer type, grade, supplier specification, and recycled-content level.
Define the application, service temperature, moisture exposure, and expected product lifetime.
Measure or estimate moisture content, acid-related risk, intrinsic viscosity, and other relevant starting properties.
Review fillers, reinforcements, pigments, flame retardants, plasticizers, lubricants, and existing stabilizers.
Select a small number of carbodiimide candidates with suitable reactivity and processing-temperature stability.
Choose powder, liquid, or masterbatch according to feeding, dispersion, handling, and carrier compatibility.
Build a dosage ladder that includes an unstabilized blank and several candidate concentrations.
Process all samples under identical, production-relevant drying, temperature, residence-time, and shear conditions.
Record initial processing behavior and properties before conducting application-relevant aging.
Compare retained properties, appearance, process stability, and cost-performance balance before pilot-scale production.
Processing records should include feeding consistency, torque, pressure, melt appearance, strand quality, odor, plate-out, color, and surface quality. The most useful result is not simply the formulation with the highest initial property. It is the formulation that retains the required properties after realistic exposure without creating an unacceptable processing or compatibility problem.
One common mistake is applying PET selection logic directly to TPU or PA. PET may be judged through intrinsic viscosity and carboxyl end groups, while TPU often requires stronger emphasis on elongation, flexibility, and hot-water durability. PA selection needs defined moisture conditioning and dimensional measurements.
Another mistake is treating all TPU grades as equivalent. Ignoring the difference between polyester-based and polyether-based TPU can lead to incorrect risk assessment and dosage selection. PA compounders may also misinterpret moisture-related property changes when dry-as-molded and conditioned specimens are not tested separately.
Selecting a masterbatch without checking its carrier can create haze, stiffness changes, surface defects, or poor compatibility. Ignoring fillers and flame retardants may hide moisture sources or chemical interactions. Testing only initial performance cannot demonstrate long-term hydrolysis protection.
Accelerated aging that is too severe or unrelated to real service conditions can also rank candidates incorrectly. Laboratory screening should narrow the options, but pilot-scale production is needed to confirm feeding, dispersion, process stability, appearance, and aging performance before mass production.
PET, TPU, and PA require different stabilization priorities even when all three can benefit from a Carbodiimide Anti-Hydrolysis Agent. PET selection should emphasize intrinsic viscosity, acid end groups, and melt stability. TPU requires flexibility retention and hot-water durability, while PA requires controlled conditioning and dimensional and mechanical retention.
Suzhou Ke Sheng Tong New Materials Technology Co., Ltd. is a manufacturer of carbodiimide anti-hydrolysis products in powder, liquid, and masterbatch forms. A structured selection and testing program can help compounders improve compatibility, processing reliability, and retained performance without relying on assumptions from another polymer system.
A: Their chemical structures, moisture responses, processing temperatures, additive packages, and critical performance indicators differ, so one selection method cannot accurately cover every compound.
A: Evaluate intrinsic viscosity, melt behavior, carboxyl end groups, tensile strength, elongation, surface appearance, processing stability, and retained performance after humid-heat aging.
A: Polyester-based TPU is generally more sensitive to hydrolysis than polyether-based TPU, making the soft-segment chemistry a primary input for stabilizer screening.
A: Absorbed moisture can alter dimensions, stiffness, impact behavior, strength, and electrical performance, so PA must be tested under defined conditioning and aging conditions.
A: Masterbatch can provide convenient and consistent feeding, provided its carrier is compatible with the base polymer, processing temperature, appearance, and performance requirements.
A: A grade may be applicable to multiple polymers, but compatibility, dosage, thermal stability, processing behavior, and aging performance must be validated separately for each compound.
