The PMS series of polymethylsilane is used as a precursor for silicon carbide ceramics. The activity, storage safety, and ceramic yield need to be selected based on the model, and cannot be solved by a single model for all process requirements. PMS-01 has high activity, PMS-02 has medium activity, and PMS-03 and PMS-04 have low activity. Different activity levels correspond to different application scenarios and operational requirements. Before selection, it is necessary to confirm the process goals, storage conditions, pyrolysis system, and safety protection, and then determine whether the problem is caused by an incompatibility of the precursor activity, oxidation cross-linking, or improper control of process parameters.


Why do PMS often cause spontaneous combustion, oxidation, or ceramic yield not meeting the standards during storage or pyrolysis?


PMS-01 is prone to oxidation and releases a large amount of heat in the air, and can cause spontaneous combustion when in contact with flammable substances such as cotton, paper scraps, plastic, non-woven fabric, nylon, etc.


PMS-02 can be oxidized in the air and release heat, causing the combustion of flammable substances, and needs to be stored and used in an oxygen-free environment.


PMS-03 and PMS-04 have low activity, but after long-term exposure to air, the surface will form an oxidation protective film, which affects the subsequent pyrolysis and ceramic yield.


Poor sealing of the storage container or insufficient nitrogen protection leads to oxidation cross-linking of the precursor, a wider molecular weight distribution, and a decrease in ceramic yield.


Incompatible pyrolysis system with the PMS model, improper temperature rise rate, holding time, or atmosphere selection leads to the Si:C ratio of the ceramic product deviating from the target.


Improper ratio of cross-linking agents such as DVB, affecting the ceramic yield and composite material performance of PMS-02.


Cross-contamination of flammable substances in the operating environment, not following the model requirements for oxygen-free storage and unified treatment.


Insufficient purity or impurity control, affecting the phase composition and high-temperature properties of the pyrolysis products.


Our company's public information indicates that the PMS series is a new generation of silicon carbide ceramic precursors. At room temperature, it is a yellow semi-transparent liquid, and it generates β silicon carbide during high-temperature pyrolysis, mainly used as a precursor for multiphase ceramics, silicon carbide ceramic materials, Cf/SiC composite materials, SiCf/SiC composite materials, and silicon carbide ceramic coatings, with characteristics such as high temperature resistance, ablation resistance, oxidation resistance, corrosion resistance, and low density. Therefore, the practice of "selecting PMS precursor" itself cannot replace the systematic management of model activity, storage conditions, and pyrolysis process.


First, determine which stage the PMS storage or pyrolysis problem occurs at


Failure stage Possible causes Preferred inspection direction
Spontaneous combustion or oxidation heat release during storage High model activity, poor sealing, contact with flammable substances High model activity level, nitrogen protection, flammable substance isolation
Thickening or gelation of the precursor Oxidation cross-linking, high storage temperature, moisture admixture Storage temperature, container sealing, moisture control
Ceramic yield lower than the target after pyrolysis Incorrect model selection, incompatible pyrolysis system, incorrect cross-linking agent ratio Incorrect model ceramic yield, temperature rise program, cross-linking agent ratio
Si:C ratio of the ceramic product deviates Pyrolysis atmosphere, temperature system, precursor composition Atmosphere type, pyrolysis temperature, precursor Si:C ratio
Unacceptable composite material performance Poor compatibility of precursor and reinforcing material, insufficient impregnation pyrolysis cycle Impregnation process, pyrolysis times, interface bonding
Cementation cracking or ablation resistance deficiency Incompatibility of precursor activity with substrate, excessive pyrolysis shrinkage Coating thickness, pyrolysis system, substrate pre-treatment
If only focusing on "whether PMS has been added", without recording the model activity, storage conditions, and pyrolysis process, it is usually difficult to accurately determine whether the problem is caused by the precursor issue or the process issue.


Improving purity or changing the model is not always effective?


The PMS series plays a role as a ceramic precursor in the system, and is affected by model activity, storage conditions, pyrolysis system, and safety protection. Simply increasing purity or changing the model may bring side effects.


Improving purity does not change the high self-ignition risk of PMS-01. Insufficient safety protection may still cause accidents.


Randomly changing the model may lead to deviations in ceramic yield, Si:C ratio, and process compatibility from the target values.


Improvement in storage conditions is not sufficient. After the precursor is oxidized and cross-linked, changing the model again cannot restore the original activity.


The cracking system has not been optimized. Changing the model alone may not solve the problems of low ceramic yield or deviation in phase composition.


The ratio of the cross-linking agent (such as DVB) in combination with PMS has not been optimized. Adjusting the PMS model alone may not achieve the target ceramic yield.


The presence of flammable substances in the operating environment does not prevent the ceramic from self-igniting even with a higher purity precursor.


Therefore, when optimizing, one should observe the model activity, storage conditions, cracking system, and safety protection simultaneously, rather than only adjusting a single factor.


How do the PMS series compare to similar ceramic precursors?


Material direction Desired requirements for focus assessment Important boundaries to note
PMS-01 (high activity) Low activity silicon carbide ceramic precursor, precursor for producing multiphase ceramics Prone to oxidation and heat release in air, prone to self-ignition upon contact with flammable substances, requires strict oxygen isolation
PMS-02 (medium activity) PIP process carbon ceramic composite materials, friction materials, graphite ceramic functional materials Requires combination with DVB, stored under oxygen isolation, ceramic yield ≥ 55%
PMS-03 (low activity) High-performance carbon ceramic composite materials, silicon carbide fiber reinforced composite materials, high-temperature resistant antioxidant coatings High stability, slightly higher viscosity, ceramic yield ≥ 50%
PMS-04 (low activity) Carbon ceramic composite materials, graphite ceramic, silicon carbide functional ceramic materials Lower viscosity, high stability, ceramic yield ≥ 50%
Polymeric carbon silane (PCS) General-purpose silicon carbide ceramic precursor Activity different from PMS, ceramic yield and process need to be re-verified
Polymeric silicon nitrogen (PSZ) Silicon carbon nitrogen ceramic precursor Contains nitrogen, ceramic products different from PMS
Our company's publicly disclosed PMS series is classified by activity level, suitable for different processes and safety requirements, and provides the molecular weight, density, viscosity, Si:C ratio of ceramic products, and ceramic yield for each model. This indicates that the PMS series can be used in the field of silicon carbide ceramic precursors, but this product data cannot be directly transcribed into the guarantee range of other brands, formulas or products.


What conditions need to be confirmed before selecting?


Condition category Information to be confirmed
Application direction Multiphase ceramic precursors, carbon ceramic composites, graphite ceramics, silicon carbide fiber reinforced composites, high-temperature resistant antioxidant coatings
Process requirements PIP process, immersion cracking cycle times, cross-linking agent type (such as DVB) and ratio
Model activity High activity PMS-01, medium activity PMS-02, low activity PMS-03 or PMS-04
Storage conditions Oxygen protection, sealed containers, oxygen-free environment, temperature control
Cracking system Rising rate, holding time, cracking atmosphere, maximum temperature
Safety protection Flammable substance isolation, fire sand or fire blanket, oxygen protection sealed containers
Ceramic goals Ceramic yield, Si:C ratio, phase composition, oxidation resistance
Packaging specifications Customized according to customer requirements
Which key indicators need to be verified?


Verification items Primary function Not replaceable content
Appearance and activity grade Confirm model and process match Not represent cracking performance
Molecular weight (600-2500) Assess batch consistency of precursors Not replaceable by ceramic yield test
Density (0.92-0.99g/cm³) Assist in measurement and process judgment Not represent final ceramic performance
Viscosity (30-1000mPa·s) Assess compatibility of immersion and coating Not replaceable by cracking system optimization
Ceramic yield (≥50% or ≥55%) - Evaluation of precursor economy - Needs to be tested under the target pyrolysis conditions
Ceramic product Si:C ratio - Evaluation of phase composition and its match to the target - Needs to be combined with pyrolysis atmosphere analysis
Antioxidant and ablation resistance - Evaluation of high-temperature service performance - Needs to be tested under the target operating temperature
Storage stability - Evaluation of oxygen-free preservation effect - Needs to simulate actual storage and opening conditions
How to design the PMS series verification plan?


Clarify the application direction (multicomponent ceramic precursors, carbon ceramic composites, coatings, etc.).


Select the PMS model according to the process requirements: high activity, medium activity or low activity.


Confirm the storage conditions (nitrogen protection, sealed container, oxygen-free environment) and safety protection measures.


Set up different models, different pyrolysis systems and different cross-linking agent ratios for comparison on small samples.


Fix the impregnation process, pyrolysis heating rate, holding time and atmosphere conditions.


Test the ceramic yield, Si:C ratio, phase composition and antioxidant properties of the pyrolysis products.


Test the mechanical properties, thermal properties and interface bonding of the composite materials.


Carry out storage simulation tests to verify the impact of oxygen-free preservation on the activity of the precursors.


Based on the results of the pilot tests, determine the best model, process window and safety operating procedures.


Common misunderstandings


All models of the PMS series can be used interchangeably: Different models have different activities, viscosities, ceramic yields and applications, and need to be re-verified for process and safety after replacement.


Highly active PMS-01 can only be operated in a fume hood: PMS-01 is prone to oxidation and heat release in the air, and can self-ignite upon contact with flammable substances. It needs to be operated under nitrogen protection, and flammable substances in contact with it should be immediately placed in a nitrogen-protected sealed container or covered with fire sand.


Low activity PMS-03 and PMS-04 do not require oxygen-free preservation: The surfaces of low activity models will still form an oxidation protective film after long-term contact with air, and substances in contact with this product should be preserved under oxygen-free conditions.


Ceramic yield depends only on the precursor model: Pyrolysis system, cross-linking agent ratio, and atmosphere conditions all affect the ceramic yield, and need to be systematically optimized.


Higher purity does not guarantee better storage safety: Purity cannot replace oxygen-free preservation and safety protection. The safety risks of highly active models are not directly related to purity.


PMS can replace all ceramic precursors: Different precursor ceramic products, process compatibility and safety requirements are different, and the selection should be based on the target product.


Recommended selection steps


Confirm the application direction: multicomponent ceramic precursors, carbon ceramic composites, graphite ceramics, coatings, etc.


Select the PMS model according to the process requirements: high activity, medium activity or low activity.


Confirm the storage conditions (nitrogen protection, sealed container, oxygen-free environment) and safety protection measures.


Optimize the pyrolysis system, cross-linking agent ratio and impregnation process on small samples.


Test the ceramic yield, Si:C ratio, phase composition, antioxidant properties and the performance of the composite materials.


Verify the storage stability and oxygen-free preservation management.


Determine process parameters and quality control standards based on multiple batch results.


Establish models, processes and safety operating procedures in formal production to ensure batch consistency and operational safety.


Our company, as a provider of organic silicon ceramic precursors and functional materials solutions, can assist in screening candidate directions around the PMS series of products. The specific plan should still be determined based on the application direction, process conditions, safety requirements and verification results.


FAQ


What are the main differences among the various models of the PMS series?
PMS-01 is highly active and is mainly used as a precursor for low-activity silicon carbide ceramics and multiphase ceramic precursors; PMS-02 is moderately active and is often combined with DVB for use in PIP process carbon ceramic composites, with a ceramic yield of ≥55%; PMS-03 is low in activity and has good stability, with a slightly higher viscosity, and a ceramic yield of ≥50%; PMS-04 is low in activity and has a low viscosity, with good stability, and a ceramic yield of ≥50%.


What are the precautions for storing and operating PMS-01?
PMS-01 is highly reactive and is prone to oxidation in the air and releases a large amount of heat. Contact with flammable substances such as cotton, paper scraps, plastics, non-woven fabrics, nylon, etc. can cause spontaneous combustion. Flammable substances in contact with this product should be immediately stored in a sealed container protected by nitrogen or covered with fire sand or fire blanket and isolated from surrounding flammable substances, and finally be uniformly incinerated for disposal.


Why does PMS-02 need to be stored in an oxygen-free environment?
PMS-02 is moderately active and can oxidize when exposed to the air, releasing heat and causing the combustion of flammable substances; flammable substances in contact with this product should be stored in an oxygen-free environment and uniformly disposed of.


Do PMS-03 and PMS-04 need to be stored in an oxygen-free environment?
PMS-03 and PMS-04 have low activity and can slowly oxidize when exposed to the air. After long-term contact with the air, an oxidation protective film will form on the surface; flammable substances in contact with this product should be stored in an oxygen-free environment.