Introduction
In the intricate world of polymer chemistry, where chains of molecules are meticulously built to deliver specific performance characteristics, the choice of initiator is paramount. Among the critical players enabling high-volume industrial processes is tert-butyl perpivalate (CAS 29240-17-3), a potent organic peroxide renowned for its efficiency as a radical generator. This comprehensive guide dives deep into the properties, applications, safety protocols, and critical considerations surrounding this essential chemical. Understanding its capabilities is vital for chemists, engineers, formulators, and procurement specialists seeking to optimize polymerization reactions, enhance production efficiency, and ensure workplace safety.
What is tert-Butyl Perpivalate (CAS 29240-17-3)?
tert-Butyl perpivalate, identified by its unique CAS registry number 29240-17-3, is a clear, volatile liquid organic peroxide. It belongs to the perester family, characterized by the general formula R-O-O-CO-R'. Its specific molecular structure consists of a tert-butyloxy group ((CH₃)₃C-O-) linked to the carbonyl of a pivaloyl (trimethylacetyl, (CH₃)₃C-C(=O)-) group, yielding the full molecular formula C₉H₁₈O₃.
Key Properties and Structure
Chemical Names: tert-Butyl perpivalate, tert-Butoxycarbonyl tert-butyl peroxide, Perpivalic acid tert-butyl ester (IUPAC-like), tert-Butyl pertrimethylacetate.
CAS Number: 29240-17-3 (The globally unique identifier).
Molecular Formula: C₉H₁₈O₃
Molecular Weight: 174.24 g/mol
Physical State: Colorless to pale yellow liquid.
Characteristic Odor: Distinct, pungent odor.
Solubility: Miscible with many common organic solvents (hydrocarbons, esters, ethers, chlorinated solvents). Very low solubility in water.
Boiling Point: Approximately 60-62 °C (at 20 hPa - important, decomposes before boiling at atm pressure).
Flash Point: Around 41 °C (closed cup) – Classifies as Flammable Liquid.
Active Oxygen Content: A crucial performance indicator for peroxides, typically around 9.18%, signifying its oxidizing power.
Decomposition Temperature (T₁/2): The temperature at which half the peroxide decomposes in a specific time (e.g., T₁/2 (1h) ~ 70°C; T₁/2 (10h) ~ 62°C). This defines its initiation window. See manufacturer datasheets for precise values.
Storage Requirements: Must be stored cold(typically < 25°C, often recommended around 10-20°C), away from ignition sources, incompatible materials, and in approved containers. Decomposition can be self-accelerating.
The Mechanism: Driving Radical Polymerization
tert-Butyl perpivalate (CAS 29240-17-3) functions as a free radical initiator. Upon heating to its decomposition temperature range, the relatively weak O-O bond cleaves homolytically. This cleavage generates two primary radical species:
1.tert-Butoxy Radical: (CH₃)₃C-O•
2.Pivaloyl (Trimethylacetyl) Radical: (CH₃)₃C-C(=O)•
The pivaloyl radical rapidly decarboxylates (loses CO₂) to form the stable tert-butyl radical: (CH₃)₃C•. It is primarily the highly reactive tert-butoxy ((CH₃)₃C-O•) and tert-butyl ((CH₃)₃C•) radicals that initiate polymerization by attacking the double bonds of monomers (like vinyl chloride, ethylene, styrene, acrylates).
Why Choose tert-Butyl Perpivalate? Advantages in Industrial Processes
What makes tert-butyl perpivalate (29240-17-3) a preferred choice for specific applications? Its unique decomposition profile offers distinct advantages:
1.High Initiation Efficiency at Lower Temperatures: Compared to common initiators like AIBN or some dialkyl peroxides, tert-butyl perpivalate decomposes at a relatively lower temperature range (T₁/2 ~62-70°C). This allows efficient initiation in polymerization processes where moderate temperatures are desired or required to control reaction kinetics or polymer quality.
2.Specific Radical Generation: Its decomposition predominantly yields tert-butoxy radicals, known for being highly effective hydrogen abstractors. This is particularly advantageous in processes like high-pressure LDPE manufacturing and certain copolymerizations.
3.Commercial Purity and Availability: It is produced commercially in high purity and consistency by major peroxide manufacturers, ensuring reliable performance and predictable reaction timescales critical for industrial production scheduling.
4.Versatility Across Monomers: Its solubility profile and effective initiation make it suitable for polymerization in bulk, solution, and suspension systems involving a wide range of monomers.
Core Applications: Where tert-Butyl Perpivalate Excels
1. Vinyl Chloride (PVC) Suspension Polymerization:
This is arguably the most significant industrial application for tert-butyl perpivalate (CAS 29240-17-3). It is frequently used in combination with initiators having different decomposition temperatures (e.g., peroxydicarbonates). Its moderate decomposition temperature provides:
•Excellent control over polymerization rate and heat generation.
•High conversion efficiencies.
•Consistent production of PVC resin with targeted molecular weight distribution and particle morphology.
•Crucial for achieving the desired properties (flow, thermal stability, gelation) in final PVC products like pipes, window profiles, films, and cable insulation.
2. Low-Density Polyethylene (LDPE) Production:
In the ultra-high-pressure (2000-3000 bar) tubular and autoclave reactors used for LDPE, tert-butyl perpivalate (29240-17-3) serves as a highly efficient primary or secondary (co-)initiator.
•Its decomposition characteristics complement other initiators (like peroxydicarbonates) in complex initiator systems.
•Contributes significantly to controlling the density and branching structure unique to LDPE.
•Enables high production rates essential for this capital-intensive process. LDPE is vital for films (packaging, agricultural), coatings, and flexible containers.
3. Acrylic Polymerizations:
Tert-butyl perpivalate is utilized in the production of acrylic resins (PMMA - polymethyl methacrylate) and polyacrylates for applications like:
•High-clarity cast sheets, rods, and tubes.
•Surface coatings requiring excellent weathering resistance and hardness.
•Adhesives and impact modifiers.
4. Styrene and Copolymer Production:
It finds application in the bulk polymerization of styrene for crystal PS (Polystyrene) and ABS (Acrylonitrile Butadiene Styrene), often in combination with other initiators to manage reaction temperatures and ensure uniformity.
5. Curing Agent for Unsaturated Polyester Resins (Limited Use):
While dialkyl peroxides (like MEKP) are more common, tert-butyl perpivalate can be used for elevated temperature curing schedules in specific composites or casting applications.
Critical Safety Handling and Storage Requirements
WARNING: tert-Butyl perpivalate (CAS 29240-17-3) is a HIGHLY REACTIVE and POTENTIALLY DANGEROUS material. Improper handling can lead to FIRE, EXPLOSION, and SEVERE HEALTH EFFECTS.
•Fire and Explosion Hazard: Flammable liquid and vapor. CLASS 5.2 Organic Peroxide (Type D, E, or F - Confirm with SDS). Uncontrolled decomposition, often self-accelerating and highly exothermic, can generate large volumes of gas, leading to violent rupture of containers and severe explosions. Elevated temperatures, contamination (especially acids, bases, metals, reducing agents, accelerators, amines), friction, or impact can trigger decomposition. DO NOT HEAT CONFINED MATERIAL.
•Reactivity Hazards: Strong oxidizing agent. Violent reactions occur with incompatible substances (combustibles, reducing agents, accelerators, strong acids/bases, transition metals and their salts). Can catalyze polymerization of polymerizable monomers (styrene, acrylates, etc.), generating hazardous heat.
•Health Hazards:
•Corrosive: Causes severe skin burns and eye damage (H314).
•Harmful if Swallowed or In Contact with Skin (H302/H312).
•May Cause Respiratory Irritation (H335).
•May Cause Damage to Organs Through Prolonged or Repeated Exposure (H372 - specific organs vary, liver/kidney are common).
•Suspected of Causing Genetic Defects (H341 - Handle with extreme care).
•Safe Handling PREREQUISITES:
•Consult and ADHERE to the specific Safety Data Sheet (SDS): Before ANY handling, obtain and thoroughly understand the latest SDS from your supplier. Procedures outlined here are general.
•
Training: Personnel must be fully trained in organic peroxide hazards, emergency procedures, and proper use of PPE.
•PPE (Minimum): Chemical-resistant gloves (e.g., Viton®, butyl rubber - check SDS compatibility), face shield/goggles, flame-retardant lab coat/coveralls, chemical apron, respirator with appropriate organic vapor cartridge if vapor concentration cannot be controlled below exposure limits. Impervious footwear.
•Engineering Controls: Perform operations in designated areas away from combustibles/incompatibles. Use under a well-maintained chemical fume hood with adequate airflow. Ground and bond all equipment to prevent static spark ignition. Avoid all ignition sources (smoking, hot surfaces, electrical arcing, sparks).
•Contamination Prevention: Use clean, dedicated equipment (pipettes, funnels) made of compatible materials (stainless steel 316, glass). NEVERuse contaminated or dirty equipment. Rigorously exclude incompatible substances.
•Temperature Control: Maintain storage and work areas below recommended temperatures (see SDS, often < 25°C, sometimes lower). Monitor temperatures closely. Only warm if explicitly permitted and controlled per SDS/manufacturer instructions. NEVER heat confined material.
•Minimize Quantities: Keep only the minimum amount needed for immediate work readily accessible.
•No Eating/Drinking/Smoking: Strictly prohibited in handling areas.
•Emergency Preparedness: Ready access to safety shower, eyewash station, appropriate fire extinguishers (Class ABC, CO₂, or foam – dry chemical unsuitable for peroxide fires), sand or inert absorbent, spill kits for organics/peroxides. Know emergency procedures for fire, spill, and exposure.
•Storage Requirements:
•Cold Storage: Store in original supplier containers or approved vented/peroxide-specific containers within a dedicated, well-ventilated, temperature-controlled refrigerator/cold room designed for flammable chemicals. Maintain temperature as specified by SDS (e.g., ≤ 20°C or colder).
•Separation: Store awayfrom all incompatible materials (flammables, combustibles, acids, bases, reducing agents, accelerators, heavy metal compounds, polymerizable monomers). Dedicated cabinet/refrigerator is best. UN separation code required (see SDS).
•Stability: Stability is limited. Adhere to supplier expiration dates. Mark containers clearly. Monitor stock regularly for signs of decomposition(increased pressure/bloating container, gas evolution, unusual odor, liquid discoloration, formation of solids/crystals). Inspect at least weekly. Immediately report abnormalities.
•Venting: Supplier containers are often vented. DO NOT store unvented containers of significant size. Non-vented transport containers must be used for transport only.
•Protection: Protect from physical damage and direct sunlight.
•Transportation:
•Classified as Dangerous Goods:
•UN Risk: UN3101 ORGANIC PEROXIDE TYPE D, LIQUID (or Type E/F - Confirm exact UN number and PG from SDS)
•Class: 5.2 (Organic Peroxide) + Sub Risk 3 (Flammable Liquid)
•Packing Group: Often II
•Requires UN-specification packaging, proper labeling, placarding on transport vehicles, and trained personnel. Strict regulations govern transport by land, sea (IMDG), and air (IATA/ICAO).
Regulatory Landscape & Compliance
Handling tert-butyl perpivalate (29240-17-3) involves navigating significant regulations:
•Classification & Labeling (GHS): Classified as hazardous per OSHA HazCom 2012 (US) and CLP Regulation (EU) with standard Hazard Statements (H statements - see Safety section above) and Precautionary Statements (P statements - obtain from SDS).
•Safety Data Sheet (SDS): Mandatory document providing detailed safety, handling, disposal, and regulatory information. Review SDS before purchase and handling.
•OSHA (US): Covered under Hazard Communication Standard (29 CFR 1910.1200), Process Safety Management (PSM) for large quantities and specific processes (Check applicability), and potentially General Duty Clause. Permissible Exposure Limits (PELs) or Threshold Limit Values (TLVs®) may apply.
•EPA (US): Subject to regulations under the Toxic Substances Control Act (TSCA) for manufacture/import. Reporting may be required under SARA Title III (EPCRA) Sections 302 (EHS), 311/312 (Tier II reporting), and 313 (TRI reporting). Also under CERCLA spill reporting.
•DOT (US Transport): Regulated as hazardous material under 49 CFR Parts 100-185 (including proper shipping name, UN number, hazard class, packing group, packaging, labeling, placarding).
•REACH & CLP (EU): Requires registration, evaluation, authorization (as applicable). Hazard classification and labeling according to CLP Annex VI. Exposure scenarios may be provided in SDS.
•Global Regulations: Comply with national/local regulations wherever handled, transported, or disposed of (e.g., DSEAR/COMAH in UK, WHMIS 2015 in Canada, etc.).
Procurement and Major Manufacturers
Sourcing tert-butyl perpivalate (CAS 29240-17-3) requires dealing with specialized chemical manufacturers and distributors due to its hazardous nature. Key global players include:
•
Arkema (Luperox® 11 brand)
•
Do Sender Chem (Perodox® 11)
•
NOF Corporation (Perbutyl P)
•
MPI Chemie
•
Akpa Kimya
•
Nouryon (formerly AkzoNobel Polymer Chemistry)
Purchase Considerations:
•Quality & Purity: Specify required purity level for your application.
•
Packaging: Ensure correct packaging size/type (drums, isotanks) suitable for safe transport, storage, and dispensing at your facility. Confirm container venting.
•
Technical Support: Evaluate supplier technical expertise and support for application and safety.
•
SDS & Documentation: Confirm provision of updated SDS and Certificates of Analysis (CoA).
•
Delivery Logistics: Ensure supplier understands and adheres to all hazardous goods transport regulations.
Conclusion
tert-Butyl perpivalate (CAS 29240-17-3) stands as an indispensable tool in the chemical engineer's arsenal, particularly within the PVC and LDPE sectors. Its unique combination of moderate decomposition temperature and efficient radical generation provides critical control over large-scale, economically vital polymerization processes. However, this power comes with significant responsibility. A thorough and uncompromising commitment to safety is non-negotiable – strict adherence to SDS instructions, rigorous engineering controls, comprehensive personnel training, and meticulous storage and handling protocols are paramount to mitigate the inherent risks of organic peroxides. Understanding both the significant operational advantages and the vital safety requirements of tert-butyl perpivalate (29240-17-3) is fundamental for anyone involved in its specification, procurement, transportation, storage, or use in industrial polymer production. By leveraging its efficiency while respecting its hazards, manufacturers can unlock enhanced performance while safeguarding personnel and facilities.
Request product-specific Safety Data Sheet (SDS) before handling tert-butyl perpivalate (CAS 29240-17-3)!