CELANESE HOSTAFORM C 13031 XF

1.1 Overview of POM as an Engineering Thermoplastic

Polyoxymethylene (POM), commonly known as acetal plastic, stands as a high-performance engineering thermoplastic material widely adopted across diverse industries. Its widespread utility stems from a remarkable combination of mechanical and physical attributes. POM exhibits high strength and stiffness, coupled with robust resistance to wear, various chemicals, and moisture. Furthermore, its inherently low friction characteristics make it an excellent choice for applications demanding durability and high wear resistance, such as precision gears, bearings, and critical automotive components.

The material's processing versatility is another significant advantage. POM can be readily processed through techniques like injection molding, extrusion, blow molding, and machining, allowing for the creation of intricate shapes and parts with tight tolerances. This ease of fabrication, combined with its resistance to temperature fluctuations and non-hygroscopic nature, ensures that it does not absorb moisture from the air. This property is particularly important as it helps maintain consistent mechanical and dimensional properties even under humid conditions. The synergistic combination of high strength, stiffness, low friction, and exceptional dimensional stability positions POM as a preferred material for precision components where consistent performance under mechanical stress and environmental exposure is paramount. This goes beyond a mere collection of individual attributes; it represents a holistic material profile engineered for demanding applications.

1.2 Homopolymer vs. Copolymer POM: Key Distinctions and Advantages

Polyoxymethylene plastics are primarily categorized into two types: homopolymer (POM-H) and copolymer (POM-C). While both offer excellent performance, their distinct molecular structures lead to differing property profiles, making each suitable for specific applications.

Homopolymer POM is characterized by a more uniform backbone, which facilitates organized crystalline packing. This structural purity typically translates into higher stiffness, strength, hardness, and superior impact strength. Additionally, POM-H generally exhibits enhanced fatigue and creep resistance, making it suitable for applications where rigidity and wear resistance are primary concerns.

In contrast, copolymer POM, such as HOSTAFORM C 13031 XF, is produced through the copolymerization of trioxane and 1,4-dioxane, introducing comonomers into the polymer chain. This molecular modification imparts improved resistance to stress cracking, superior chemical resistance, particularly against strong alkalis, and enhanced thermal stability compared to homopolymers. Copolymer POM also generally offers better long-term stability and higher continuous use temperatures. The selection between POM homopolymer and copolymer is not arbitrary; it is a strategic decision driven by specific application requirements, especially those involving chemical exposure and long-term thermal stability. The "XF" designation on C 13031 XF, which signifies its fuel resistance, directly capitalizes on the inherent advantages of the POM copolymer structure in aggressive chemical environments. The superior chemical resistance of POM copolymer is the fundamental reason why C 13031 XF, as a copolymer, is specifically engineered and targeted for fuel system applications, where its molecular structure provides the necessary resilience against chemical deterioration that a homopolymer might lack.

2.1 Material Composition and Unique Characteristics

CELANESE HOSTAFORM C 13031 XF is an acetal copolymer grade (POM-C) meticulously engineered and manufactured by Celanese. The "XF" suffix in its designation is a critical indicator, denoting its specialized modification to resist deterioration from aggressive fuel blends, thereby positioning it as a highly specialized material for the transportation industry.

A distinctive feature of Hostaform C 13031 XF in its natural form is its characteristic yellow color (Color code 50/5339). This specific coloration is not merely aesthetic; it serves as a deliberate visual cue to signify its intended use in fuel systems. This color coding is a crucial safety and identification feature, reflecting a comprehensive design approach that extends beyond the material's inherent properties to encompass practical application and regulatory adherence. In industrial settings, color coding is frequently employed for safety, identification, and maintenance. Given the inherent risks associated with fuel systems (e.g., flammability, toxicity), the yellow color acts as an immediate visual identifier for technicians and manufacturers, confirming the component's intended use and potentially its specific chemical resistance profile. This assists in proper assembly, maintenance, and adherence to safety protocols. Beyond its natural yellow, the product is also available in black (Color code 10/9022), specifically formulated for applications requiring laser welding. This dual-color availability underscores the material's adaptability for specific functional and processing requirements. Furthermore, Hostaform C 13031 XF is described as an "easy flow" grade for injection molding, yet it concurrently offers increased strength, rigidity, and hardness. This combination represents an optimized balance, facilitating efficient processing while ensuring high mechanical performance in the final component.

2.2 Intended Applications and Target Industries

The primary and most critical application for Hostaform C 13031 XF lies within transportation industry fuel systems. Its specific modification to withstand aggressive fuel blends is the fundamental reason for this specialization. Modern fuels, particularly those with higher ethanol or biodiesel content, can be significantly more corrosive or chemically aggressive towards conventional plastics. The explicit targeting of "transportation industry fuel systems" for C 13031 XF indicates that this material directly addresses a specific, high-stakes engineering challenge where standard POM grades might fail due to the increasing aggressiveness of these modern fuel compositions. Without such specialized materials, the integrity of fuel systems could be compromised, potentially leading to leaks, material degradation, and safety hazards. This material therefore represents a sophisticated engineering solution developed in response to evolving industry demands.

More broadly, as a POM copolymer, Hostaform C 13031 XF inherits the general versatility characteristic of polyoxymethylene materials. POM is widely used across various sectors, including the automotive industry for components like fuel system parts, interior trim, and door handles. It also finds application in the electrical industry (switches, connectors), consumer goods (zippers, handles), industrial manufacturing (bearings, valves, pump components), and even certain medical devices (syringes, surgical instruments for specific grades). However, the "XF" grade's specific formulation and designation clearly indicate a concentrated focus on applications where direct fuel contact is anticipated and critical.

3.1 Physical Properties

The physical characteristics of Hostaform C 13031 XF are fundamental for initial design considerations and processing optimization.

Table 1: Physical Properties of HOSTAFORM C 13031 XF

The density of 1420 kg/m³ contributes to the material's overall robustness. A Melt Volume-Flow Rate (MVR) of 12 cm³/10min at 190 °C and 2.16 kg load indicates a moderate flow rate, which is beneficial for injection molding, allowing for good processability while maintaining sufficient melt viscosity for part integrity. The molding shrinkage values, 2.2% parallel and 1.9% normal, highlight a slight anisotropy that is important for precise mold design to achieve tight tolerances in the final component. A particularly noteworthy physical property is its low humidity absorption, measured at 0.3%. This low moisture uptake is a critical factor for maintaining dimensional stability, especially for precision components operating in variable humidity environments, such as automotive fuel systems, where consistent part geometry is paramount for sealing integrity and overall functionality. Minimal dimensional change due to moisture absorption is vital for long-term reliability and preventing leaks, directly supporting its application in environments exposed to varying humidity and temperature.

3.2 Mechanical Properties

The mechanical strength and resilience of Hostaform C 13031 XF are fundamental to its performance in demanding applications, particularly those involving load-bearing and impact resistance.

Table 2: Mechanical Properties of HOSTAFORM C 13031 XF

The high tensile modulus of 2850 MPa indicates substantial stiffness, while a yield stress of 62 MPa defines the point at which the material begins plastic deformation. The nominal strain at break of 30% suggests a degree of toughness before fracture. The flexural modulus of 2900 MPa at 23°C confirms its resistance to bending deformation. A particularly important characteristic for automotive applications is the material's impact strength. Hostaform C 13031 XF demonstrates a high Charpy impact strength of 150 kJ/m² at +23°C and a robust 140 kJ/m² even at -30°C. This consistent high impact performance across a wide temperature range is a critical performance indicator for automotive components, which must withstand sudden impacts or vibrations in diverse operating conditions, including harsh winter climates. This means that parts made from C 13031 XF will resist brittle fracture and maintain structural integrity even in very cold environments, enhancing both safety and reliability. The difference between unnotched and notched impact strengths (7.5 kJ/m² at +23°C and 6 kJ/m² at -30°C for notched) highlights the material's sensitivity to stress concentrations, a factor designers must consider for optimal part geometry.

3.3 Thermal Properties

The thermal behavior of Hostaform C 13031 XF is crucial for understanding its performance under varying temperature conditions and its suitability for applications exposed to heat.

Table 3: Thermal Properties of HOSTAFORM C 13031 XF

The melting temperature of 170 °C is consistent with typical POM copolymer melting points. The Temperature of Deflection Under Load (DTUL) values are particularly insightful: 102 °C at 1.80 MPa and 159 °C at 0.45 MPa. This difference highlights the material's load-dependent thermal stability. While the material can withstand higher temperatures under lighter loads, its practical continuous service temperature under significant mechanical load will be lower. This necessitates careful design considerations for high-temperature, high-stress applications to prevent premature part failure due to creep or deformation under combined thermal and mechanical loads. The coefficient of linear thermal expansion is 90 E-6/K for both parallel and normal directions, indicating its dimensional change with temperature. The burning rate of 61.7 mm/min (ISO 3795 (FMVSS 302)) provides crucial information regarding its flammability characteristics, which is highly relevant for automotive safety standards.

3.4 Electrical Properties

While the primary focus for Hostaform C 13031 XF is its fuel resistance, its electrical properties can be relevant for integrated components or sensors within fuel systems. Although specific electrical property data for C 13031 XF is not explicitly detailed in all XF-specific datasheets, the general excellent electrical properties of POM are well-established. For instance, a related grade, Hostaform C 13031, exhibits a dielectric constant of 4 at both 100Hz and 1MHz, a volume resistivity of 1E12 Ohm*m, and an electric strength of 35 kV/mm.

Given that C 13031 XF is a variant of C 13031 primarily differentiated by fuel resistance modification, it is reasonable to infer that C 13031 XF retains the good electrical insulation characteristics inherent to POM copolymers. This is an important consideration for modern automotive fuel systems, which often incorporate electrical sensors (e.g., for fuel level or pressure) that rely on stable electrical signals. The inherent insulating capabilities of the base polymer are beneficial for overall system integration, preventing short circuits or signal interference within these critical components.

4.1 Resistance to Aggressive Fuel Blends (e.g., diesel, biodiesel)

Hostaform C 13031 XF is specifically engineered to resist deterioration from aggressive fuel blends, making it exceptionally well-suited for transportation industry fuel systems. The material has undergone extensive testing to confirm its chemical compatibility with various standard fuels. It demonstrates good resistance to ISO 1817 Liquid 1 (E5), Liquid 2 (M15E4), Liquid 3 (M3E7), and Liquid 4 (M15) when exposed at 60°C. Furthermore, it resists standard fuel without alcohol (preferably ISO 1817 Liquid C) and standard fuel with alcohol (preferably ISO 1817 Liquid 4) at 23°C.

Long-term immersion tests provide further validation of its durability. Hostaform C 13031 XF, alongside its closely related grade C 13031, maintained only moderate mass change levels after an extensive 6000 hours of immersion at 90°C in aggressive media such as US#2 ultra-low sulfur diesel and biodiesel blends (B20 using soybean methyl esters), with weekly fuel refreshes. This quantitative data, showing moderate mass change over such prolonged exposure at elevated temperatures, is a significant indicator of the material's long-term reliability. It moves beyond a simple statement of "resistance" to quantify the material's stability under sustained, high-temperature chemical exposure, which is absolutely critical for ensuring the lifespan and safety of automotive components. This robust performance reduces the risk of material breakdown, component failure, and associated safety hazards or environmental leaks over the vehicle's operational lifetime.

4.2 Compatibility with Diesel Exhaust Fluid (AdBlue®)

In addition to fuel resistance, Hostaform polyacetals, including C 13031 (which shares a foundational chemistry with C 13031 XF), have been rigorously tested for chemical compatibility with Diesel Exhaust Fluid (DEF), also known as AdBlue®. These tests, conducted over 28 days at both 60 °C and 80 °C, yielded excellent results. After exposure, the AdBlue® solution itself retained its purity and composition, consistently satisfying the stringent requirements of DIN and ISO standards (DIN 70070, DIN 70071, ISO 22241-1, ISO 22241-2).

Crucially, the mechanical properties of the Hostaform grades also demonstrated exceptional retention. Modulus retention values exceeded 85%, and elongation at break values remained above 100% after 28 days of exposure to AdBlue® at both 60 °C and 80 °C. This signifies that the material, by extension, is not only resistant to the chemical attack of DEF but also maintains its structural integrity and flexibility. This property is vital for components that may be exposed to both fuel and DEF in modern diesel vehicles, ensuring that parts do not become brittle or lose their load-bearing capacity, which is critical for the reliability of emission control systems.

4.3 General Chemical Resistance Profile (solvents, alkalis, acids)

As a POM copolymer, Hostaform C 13031 XF generally exhibits good chemical resistance to a broad spectrum of solvents, fuels, and many other chemicals. It is particularly noted for its robust resistance to strong alkalis and demonstrates good hydrolysis resistance. For instance, POM-C is known to resist chemicals such as ethanol and formaldehyde without significant degradation.

However, it is important to note that no single polymer offers universal chemical resistance. Hostaform C 13031 XF, like other POM materials, is susceptible to attack by strong mineral acids (with a pH below 4) and oxidizing agents. Some sources indicate severe effects from specific strong acids (e.g., Acetic Acid, Hydrochloric Acid) and halogens (e.g., Bromine, Chlorine). While C 13031 XF excels in fuel resistance, its general chemical resistance profile, particularly its vulnerability to strong acids and oxidizing agents, underscores the importance of understanding specific chemical exposures in any given application. This means that while it is an excellent choice for its targeted fuel system applications, it should not be indiscriminately used in environments where such aggressive chemicals are present. Designers must conduct thorough chemical compatibility assessments for each unique application. The material generally exhibits low environmental stress cracking, which enhances its durability in stressed environments.

Table 4: Chemical Resistance of HOSTAFORM C 13031 XF to Specific Media

5.1 Pre-Drying Recommendations

Generally, pre-drying of Hostaform C 13031 XF is not required due to its inherently low moisture absorption. This characteristic minimizes the risk of hydrolytic degradation during processing. However, in practical industrial scenarios, if the material has been exposed to moisture through improper storage, handling, or if regrind material is used, drying may become necessary to prevent common processing defects such as splay marks and odor problems in the molded parts. This recommendation, despite the material's non-hygroscopic nature, underscores the practical realities of industrial handling; even excellent inherent material properties can be compromised by inadequate storage, highlighting the importance of proper material management in manufacturing.

When drying is deemed necessary, the recommended conditions are:

• Drying Time: 3 hours, with some sources suggesting 3 to 6 hours.
• Drying Temperature: 80 - 100 °C, or 100 - 120 °C.
• Maximum Water Content: The material should not exceed 0.2% water content prior to processing.

5.2 Temperature Parameters (Melt, Mold, Zones)

Precise temperature control throughout the injection molding machine is critical for ensuring optimal melt quality, consistent mold filling, and the desired properties in the final component.

Table 5: Typical Injection Molding Processing Conditions for HOSTAFORM C 13031 XF - Temperatures

The recommended melt temperature range is 190 - 210 °C. The mold temperature range of 80 - 120 °C is particularly significant. It has been observed that higher mold temperatures, up to 120°C, can result in moldings with increased toughness and rigidity. This indicates that mold temperature is a critical process variable for tuning the final mechanical properties of the part. As POM is a semi-crystalline thermoplastic, its mechanical properties are directly influenced by the degree of crystallization, which in turn increases with higher mold temperatures. This means that engineers can optimize the mold temperature to achieve specific performance characteristics required for different applications, highlighting the sophisticated interplay between processing parameters and material properties.

5.3 Pressure Parameters (Injection, Hold, Back Pressure)

Appropriate pressure settings are essential for achieving complete mold filling, minimizing defects, and ensuring part integrity.

Table 6: Typical Injection Molding Processing Conditions for HOSTAFORM C 13031 XF - Pressures

Injection pressure and hold pressure ranges are specified from 600 to 1200 bar. For back pressure, a range of 0 to 40 bar is given, but it is explicitly stated that back pressure on Hostaform POM materials should be maintained as low as possible, just enough to remove air from the pellets during feeding. This instruction is a critical optimization point, implying that excessive back pressure, while sometimes used to improve melt homogeneity, can be detrimental for POM. High back pressure can lead to increased melt temperature and shear, potentially causing material degradation or increased cycle times without significant benefit. This specific guidance directs processors to avoid unnecessary energy input and potential polymer degradation, emphasizing that for Hostaform C 13031 XF, the primary function of back pressure (air removal) should be prioritized.

5.4 Speed Parameters (Injection, Screw Speed)

Controlling injection and screw speeds influences melt quality, mold filling dynamics, and the final appearance and integrity of the molded part.

Table 7: Typical Injection Molding Processing Conditions for HOSTAFORM C 13031 XF - Screw Speed

The recommended injection speed for Hostaform C 13031 XF is "slow-medium". This recommendation, for a material described as an "easy flow" grade, might initially appear counter-intuitive. However, for POM, this approach is designed to prevent excessive shear heating and the generation of formaldehyde, which can occur at high injection speeds. Such conditions can degrade the material, compromising its long-term stability, particularly in the aggressive fuel environments for which C 13031 XF is intended. Therefore, despite its easy-flowing nature, the "slow-medium" injection speed prioritizes maintaining material integrity and avoiding degradation by carefully controlling shear and temperature during injection. This is especially crucial for a fuel-resistant grade where long-term chemical stability is paramount. The specified screw speeds, ranging from 70 RPM for a 55mm screw diameter to 150 RPM for a 25mm screw diameter, are also tailored to ensure proper plastication without inducing excessive shear. Standard injection molding machines equipped with three-phase (15 to 25 D) plasticating screws are suitable for processing this material.

6.1 Primary Applications in Transportation Fuel Systems

CELANESE HOSTAFORM C 13031 XF is explicitly "specially targeted for transportation industry fuel systems". Its unique modification to resist aggressive fuel blends is the fundamental reason for this specialized focus. This includes a range of critical components within automotive systems, such as various fuel system parts, and potentially interior trim components and door handles where fuel contact or exposure to fuel vapors might occur.

A notable feature supporting its role in fuel systems is the distinctive yellow color (Color code 50/5339) of its natural form, which is specifically chosen to denote its use in fuel applications. This explicit color coding for fuel system use is a strong indicator of its critical role in safety and regulatory compliance within the automotive sector. It extends beyond mere material performance to address practical aspects of manufacturing, assembly, and maintenance, ensuring correct material usage in high-risk applications. The material's proven resistance to hot diesel and various standard fuel blends (ISO 1817 Liquids, US#2 diesel, biodiesel) over extended periods and at elevated temperatures further confirms its suitability for these demanding environments.

6.2 Other Potential Applications

While Hostaform C 13031 XF is specifically tailored for fuel systems, its underlying nature as a high-performance POM copolymer means it inherits many of the general advantages of POM-C. This broad property profile makes it suitable for a wider range of applications where high strength, stiffness, excellent dimensional stability, and good chemical resistance are valued.

General POM applications include:

• Electrical Industry: Components such as switches, connectors, and gears benefit from POM's excellent insulation properties and dimensional stability.
• Consumer Goods: Its wear resistance and durability make it suitable for items like zippers, handles, and rods.
• Industrial Manufacturing: Applications such as bearings, valves, and pump components leverage its dimensional stability, low friction, and high-temperature resistance.
• Medical Devices: While C 13031 XF is not explicitly designated as food or medical grade, other POM grades are used in medical devices like syringes, surgical instruments, and pumps due to their chemical resistance, dimensional stability, and biocompatibility.

This implies that if an application outside of fuel systems requires a combination of high mechanical performance, excellent dimensional stability, and good chemical resistance (especially to alkalis or solvents), Hostaform C 13031 XF could be a strong candidate. Its robust properties, even if over-specified for fuel resistance in a particular non-fuel application, could simplify material procurement by allowing a single, high-performance POM grade to be used across multiple product lines, demonstrating a potential for cross-industry application.

6.3 Advantages for Specific Part Designs

The comprehensive property profile of Hostaform C 13031 XF offers significant advantages for specific part designs:

• High Strength, Stiffness, and Rigidity: These properties make it ideal for applications requiring structural integrity and substantial load-bearing capabilities.
• Low Friction and High Wear Resistance: This characteristic is crucial for sliding or rotating applications, such as gears and bearings, where long-term smooth operation and minimal material degradation are necessary.
• Good Dimensional Stability: This is paramount for components requiring tight tolerances and consistent performance across varying temperatures and over extended periods.
• Excellent Resilience: The material's ability to recover its original shape after stress makes it highly suitable for components that function as clips or springs, ensuring consistent performance over repeated cycles.
• Resistance to Stress Cracking: This property enhances the durability of components, particularly in environments where they are subjected to continuous stress in the presence of chemicals.

The combination of "excellent resilience" and "resistance to stress cracking" is particularly valuable for designing complex part geometries that incorporate features like snap-fits or living hinges. This means that designers can leverage these properties to create integrated, multi-functional components, which can reduce assembly steps, potentially lower overall part count, and improve the long-term reliability of integrated components.

7.1 Relevant Standards and Approvals

Hostaform C 13031 XF has a specified burning rate of 61.7 mm/min for a thickness of 1 mm, tested according to ISO 3795 (FMVSS 302). This standard is highly relevant for automotive interior materials, and its compliance is a direct indicator of its suitability for automotive applications where fire safety standards are mandatory. This specific certification is not merely a material property; it acts as a regulatory gatekeeper, confirming that the material can be legally and safely used in automotive interiors, including fuel system components that might be in the passenger compartment or engine bay, where fire safety is paramount.

While specific certifications like PFOA, PFOS, ROHS, and FDA (21 CFR 177.2470) are explicitly mentioned for other Hostaform grades (e.g., C 13031 80/5688 BLUE or C 13031 XAP), the general Hostaform product line frequently complies with various regulations. For instance, many Hostaform products comply with FDA and EU food contact regulations (2002/72 EC), and some have successfully passed drinking water testing by organizations such as WRAS, KTW, and NSF. Additionally, certain medical technology (MT) grades possess Drug Master Files and comply with USP Class VI guidelines. These broader statements from the manufacturer indicate a general capability and commitment to meeting diverse regulatory requirements across their product portfolio.

7.2 Safety Data Sheet (SDS) Availability

Safety Data Sheets (SDS) for Hostaform products, including C 13031 XF, are readily available from Celanese. Users can typically access these documents through Celanese's dedicated SDS search tool or by contacting their customer services department. The availability of an SDS is a fundamental requirement for industrial materials, ensuring workplace safety and compliance with chemical handling regulations. These documents provide crucial information regarding safe handling procedures, proper storage conditions, disposal guidelines, and emergency protocols for the material. This ensures that users of C 13031 XF can access vital safety information, thereby promoting safe handling, storage, and disposal practices throughout manufacturing and in end-use environments.

CELANESE HOSTAFORM C 13031 XF POM is a highly specialized acetal copolymer (POM-C) engineered to meet the rigorous demands of modern industrial applications, particularly within transportation fuel systems. This material distinguishes itself through a balanced and robust profile of physical, mechanical, and thermal properties, including high strength, stiffness, and exceptional impact resistance, even at sub-zero temperatures. Its inherent dimensional stability and low moisture absorption ensure consistent performance in precision components, a critical requirement for maintaining sealing integrity and functionality in varying environmental conditions.

The material's most defining characteristic is its superior chemical resistance, specifically tailored for aggressive fuel blends. Extensive testing has demonstrated its long-term stability and only moderate mass change when immersed in various standard fuels, including hot diesel and biodiesel blends, at elevated temperatures for thousands of hours. Furthermore, its proven compatibility with Diesel Exhaust Fluid (AdBlue®), maintaining excellent mechanical property retention after exposure, underscores its suitability for the complex chemical environments of modern diesel vehicles. The distinctive yellow color of its natural form serves as a practical safety and identification feature, ensuring correct material usage in critical fuel system applications.

From a processing perspective, Hostaform C 13031 XF offers favorable injection molding characteristics, with well-defined parameters for pre-drying (if necessary), temperature control across zones, and pressure and speed settings. The guidance on maintaining a "slow-medium" injection speed, despite its easy flow, exemplifies the manufacturer's deep understanding of POM processing, prioritizing material integrity and long-term stability by mitigating potential degradation from excessive shear heating.

In essence, CELANESE HOSTAFORM C 13031 XF is not merely a plastic; it is a highly engineered solution designed to address specific, complex challenges in the automotive sector. Its development reflects a profound understanding of both polymer science and real-world application demands, particularly the evolving nature of fuels and the paramount need for long-term reliability and safety in critical components. This comprehensive approach, from molecular design to processing guidelines and regulatory compliance, positions Hostaform C 13031 XF as a robust, reliable, and purpose-built material that significantly contributes to product innovation, safety, and longevity in demanding automotive and industrial applications.