Flame Retardant Modification And Application Of Thermoplastic Elastomers

Flame Retardant Modification And Application Of Thermoplastic Elastomers

I. Flame retardancy of polyolefin thermoplastic elastomers

II. Flame retardancy of styrenic thermoplastic elastomers

III. Flame retardancy of polyurethane elastomers

IV. Flame retardancy of vinyl chloride thermoplastic elastomers

V. Flame retardancy of polyester TPEE elastomers

VI. Conclusion

For polymers, in addition to mechanical properties and aging properties, flame retardant properties are a very important indicator.

Industrial developed countries polymer flame retardant modification started earlier, the production and application of flame retardant polymer materials, China in this regard and the developed countries have a big gap. In recent years, the rapid development of China's TPE and the requirements for its flame retardancy, making flame retardant thermoplastic elastomers become a hot spot in the field of materials research.

The types of thermoplastic elastomers are more, applied in flame retardant materials, at present, more research at home and abroad are mainly polyolefins, styrenics, polyurethane, polyester elastomers and polyvinyl chloride elastomers and so on.

1. Flame retardancy of polyolefin thermoplastic elastomers

Polyolefin thermoplastic elastomer is composed of rubber and polyolefin resin. The preparation of polyolefin thermoplastic elastomers generally have two processes: mechanical blending method and dynamic vulcanization method.

Polyolefin thermoplastic elastomer has excellent abrasion resistance, weather resistance, lower cost, can replace thermosetting vulcanized rubber, has a strong competitive advantage.

• Simple Blended TPO Flame Retardant

Simple blending TPO flame retardant research is more extensive, generally using EPDM/PP or POE/PP blending, flame retardant system is divided into halogenated system and halogen-free flame retardant system.

Halogen flame retardant system using decabromodiphenyl ethane and antimony trioxide composite system as a flame retardant, antimony trioxide and halogenated flame retardants share a synergistic effect, first of all, the thermal decomposition of halogen-containing organics to produce hydrogen halide, and Sb2O3 synthesis to generate antimony trihalide, with hydrogen halide with the display of flame retardant properties.

TPO halogen-free flame retardant system is an inorganic flame retardant (hydroxide compounds), the principle is that the hydrated metal oxides will be released after the heat of crystalline water, absorbing a large amount of heat, thereby inhibiting the rise in polymer temperature, preventing the delayed combustion; at the same time, a large number of dehydration decomposition reaction of the water vapor can be diluted flammable gases, to play a flame retardant effect.

However, this kind of flame retardant needs to add a relatively large amount, the larger the addition, the lower the impact strength, through the surface modification of inorganic flame retardants can obtain the ideal performance of low-cost halogen-free flame retardant TPO materials.

In addition, there are relevant tests show that the phosphorus and nitrogen-type compound flame retardant on the flame retardant effect of the hybrid TPO is also relatively good, the amount of additive relative to the hydroxide is much less than the same level of flame retardant performance can be achieved, and the impact on the physical properties of the material is also relatively small, such as:

Piperazine pyrophosphate and melamine polyphosphate (MPP) compounding system, organic aluminum hypophosphite and melamine cyanuronate (MCA) compounding system, or inorganic hydroxide and phosphorus-nitrogen compounding system shared synergistically, reducing the amount of inorganic flame retardant additives to improve the performance of the material can be prepared to meet the requirements of the various types of flame-retardant TPO blending materials.

Flame-retardant TPO co-blended materials are widely used in automotive parts, electronic and electrical appliances, functional sheathing, flooring, as well as wire and cable sheathing and insulated wire.

• Dynamically vulcanized TPO (TPV) flame retardant

The emergence of dynamic vulcanization method is an important milestone in the development of thermoplastic elastomers, and its flame retardant research is one of the current hot spots. Due to its special dynamic vulcanization system, which gives it excellent comprehensive performance.

Preparation of dynamic vulcanization of TPO (TPV) of the basic formula: PP 30 parts, EPDM (oil-filled) 70 parts, dipropylene peroxide (DCP) 1 ~ 1.5 parts, ultrafine talc (or flame retardant) appropriate amount of other additives appropriate amount.

Flame retardant selection: Flame retardant using magnesium hydroxide as the main, with the use of decabromodiphenyl ethane and antimony trioxide; non-halogenated flame retardant generally use magnesium hydroxide, aluminum hydroxide, aluminum diethyl organophosphonate and so on.

TPV is widely used in automotive parts, electronic and electrical appliances, consumer goods and construction and other fields, specifically automotive sealing materials, automotive engine systems, brakes and muffler parts, battery shells, wire and cable insulation and sheathing, household goods/medical supplies packaging.

2. Flame retardancy of styrenic thermoplastic elastomers

Styrenic thermoplastic elastomers are block copolymers of polystyrene and rubber (butadiene, isoprene, butene/ethylene, butene/propylene) and their modifications. Styrenic thermoplastic elastomers have excellent tensile strength, high coefficient of surface friction, good low-temperature properties, excellent electrical properties, and good processing properties.

Flame retardant selection:

There are halogenated systems to choose decabromodiphenyl ethane and antimony trioxide compound; halogen-free systems generally choose melamine cyanurate (MCA), melamine polyphosphate (MPP), diethyl organic aluminum hypophosphite, piperazine pyrophosphate, inorganic aluminum hypophosphite, triazine charcoal-forming agent and so on.

As SEBS, the raw material of styrenic elastomers, needs to be filled with a certain number of times of white oil or naphthenic oil to adjust the hardness, feel and reduce the processing temperature, and these oils have a great influence on the flame retardant properties, so choose the suitable flame retardant system and the right amount of flame retardant, and the SEBS with the right molecular weight to meet the requirements.

In order to improve the hardness and strength, it is necessary to add a certain amount of polypropylene, polystyrene, POE and other high strength resins. In addition, in order to improve the processing temperature resistance and aging performance of the material, it is also necessary to add some antioxidants.Lubricating dispersant can choose silicone powder, silicone masterbatch, EBS, PE wax, erucic acid amide, oleic acid amide, etc., the liquid lubricant using silicone oil, etc., the type of additives and additive amount must pay attention to not have precipitation.

Basic formula of flame retardant TPE:

SEBS+White oil (naphthenic oil)+PP+POE+Grafted SEBS+Filler+Flame retardant+Antioxidant+ UV+Anti-copper agent+Slip agent+Pigments.

• Halogen-free flame-retardant TPE cover material for data cables

Extrusion molding method: the material should be easy to plasticize at low temperatures, flame retardant peripheral material due to the addition of more flame retardant, will affect the extrusion appearance, if poor plasticization will cause pinholes, bulging bags, impurities and white spots, etc., so the formulation design and the requirements of the mixing equipment is higher, the use of high-shear high-torque equipment for flame retardant material performance is better, especially flame retardant TPE wire material formulation design needs to pay attention to the cracking and long-term Aging performance.

Applications: Sheathing for consumer electronics data cables, insulated cables, power cables, charging pile sheathing cables, etc.

• Injection molding grade halogen-free flame retardant TPE plug material

Injection molding of flame retardant TPE needs to use low melting point and high fluidity material combination, so the higher the flame retardant properties, the corresponding hardness adjustment and mechanical properties also have a greater impact, at present, generally more halogen-free flame retardant application system, in line with ROHS2.0 and Reach environmental control standards.

Applications: charging data cable USB header, power cord plugs

3. Flame retardancy of polyurethane elastomers

Thermoplastic polyurethane elastomers are usually polymerized from oligomeric polyols, isocyanates, chain extenders/crosslinkers and small amounts of additives, and are classified as polyester and polyether types.

Polyurethane elastomers are a kind of block polymerization, generally composed of polyol flexible long chain constitutes the soft segment, with diisocyanate and chain extender constitutes the hard segment. Polyurethane elastomer molecular chain contains a large number of ammonia ester groups and ether, ester and urea groups, with strong hydrogen bonding.

By the many ethers and esters to generate the formula can be very different performance of polyurethane elastomer varieties. 1940s, Germany and the United Kingdom was the first to develop, the end of the 1970s, China officially began mass production. With excellent abrasion resistance, transparency, fatigue resistance.

Polyester-type TPU elastomer flame retardant additive less can meet the requirements of flame retardant, and polyether-type TPU elastomer, often need to add more flame retardant to meet the requirements of flame retardant, so the impact on the performance is relatively large, especially the flame retardant is not hydrolysis-resistant, easy to precipitate, need to be adjusted through the formula to improve mechanical properties and aging requirements.

Flame retardant selection: non-halogenated flame retardant system generally have magnesium hydroxide, aluminum hydroxide, melamine cyanurate (MCA), diethyl organic aluminum hypophosphite, inorganic aluminum hypophosphite and phosphate flame retardants.

Flame retardant TPU basic formula:

• TPU (polyester) 80~90 parts + compatibilizer + halogen-free flame retardant 8~12 parts + wax (appropriate amount) + UV agent + antioxidant

• TPU (polyether) 60~70 parts + compatibilizer + halogen-free flame retardant 30~35 parts + wax (appropriate amount) + UV agent + antioxidant

Polyether type TPU flame retardant is added more, it is recommended to use flame retardant masterbatch processing.

Applications: communication wires and cables, charging pile sheathing, sea cables and other cables, etc.

4. Flame retardancy of vinyl chloride thermoplastic elastomers

Vinyl chloride flame retardant thermoplastic elastomer (TPVC) is a flame retardant modifier of PVC material with good weather resistance, scratch resistance, soft handfeel and low price, which is widely used in China.By the latest PVC blending technology can be obtained soft, low-pressure stereotypes and has a good chemical corrosion resistance, this mixture has better low-temperature flexibility compared to ordinary TPE materials, and can be made into flame-retardant materials.

Depending on the method of imparting rubber-like elasticity to PVC, TPVC is available in high polymerization, cross-linked and alloy types.PVC is available from a wide variety of sources and is domestically available at low prices. It is found that NBR and PVC have similar solubility parameters, similar polarity, close surface tension and good compatibility. NBR/PVC thermoplastic elastomers prepared by dynamic vulcanization technology have good physicochemical properties, and thus there is much interest in such elastomers.

According to the relevant literature, Peng and other NBR/PVC system of thermoplastic elastomers on the flame retardant and antistatic treatment of research, dynamic vulcanization method to prepare a flame retardant, antistatic properties of the NBR/PVC blend of thermoplastic elastomers, and found that the formulation of rubber-plastic blending ratio, the amount of carbon black filler, aluminum hydroxide filler amount and the amount of crosslinking agent have a greater impact on the performance of elastomers, the return to the refining has little effect on the performance of elastomers, and the amount of crosslinking agent has a significant impact on the performance of elastomers. It was found that the rubber-plastic blending ratio, the amount of carbon black filling, the amount of aluminum hydroxide filling and the amount of cross-linking agent in the formulation had a greater effect on the performance of the elastomers, while the refining had little effect on the performance of the elastomers.

PVC resin itself is relatively good flame retardant, oxygen index can reach 36%, but due to the addition of plasticizers on the flame retardant effect, can be compounded with other flame retardants can be higher requirements of flame retardant properties, can be compounded with the flame retardant magnesium hydroxide, aluminum hydroxide, decabromodiphenylethylene, antimony trioxide, zinc borate and so on.Tetrabromophthalic anhydride ester (B45-Z) can also be used to replace some of the plasticizers, the oxygen index has been greatly improved, but the density will also increase, this is due to the bromine-containing compounds of the specific gravity (B45-Z specific gravity of 1.545, while the specific gravity of DOTP is less than 1).

TPVC elastomers are used in a wide range of applications, flooring, wires and cables, charging pile sheathing lines, door and window seals, etc. However, with more and more research on flame-retardant TPEs, many of these applications need to be halogen-free, and they have now been replaced by flame-retardant TPEs.

5. Flame retardancy of polyester TPEE elastomers

Thermoplastic polyester elastomer, abbreviated as TPEE, is a block copolymer containing polyester hard segments and polyether soft segments.TPEE hard and soft segments of the two-phase separation between the microstructure, in which the hard segment for the aromatic polyester, generally terephthalic acid; soft segments of polytetrahydrofuran polyether and aliphatic polyester which are the two most common, with outstanding strength, high temperature resistance, is a comprehensive performance of engineering plastics elastomers.

TPEE's most important feature is its tensile stress under low stress than the same hardness of other polymer products, so its parts wall thickness can be made thinner, and low-temperature toughness, chemical resistance, oil resistance is excellent, and has good electrical insulation properties.

In recent years, with the expansion of TPEE applications, its flame retardant requirements are increasingly high, and even the market has appeared on the irradiation crosslinking flame retardant TPEE materials for wire and cable and oil-resistant harness bellows.

At this stage, the domestic flame retardant TPEE modification is relatively rare, common flame retardant system or halogen-containing flame retardant still occupies a major share of the market, the amount of additive is low, the mechanical properties of TPEE and other properties of the impact of a little.However, due to the demand for halogen-free, halogen-free flame retardant TPEE development is also a new research direction, mainly diethyl aluminum hypophosphite, inorganic aluminum hypophosphite, inorganic hydroxide-based, halogen-free flame retardant on the mechanical properties of the TPEE has a greater impact on the mechanical properties of the TPEE, if the requirements of flame retardant level to V0 or VW-1 or very rare.

Applications: wire and cable, harness sheathing and bellows, etc.

Conclusion

With the increased investment in the research and development of flame retardant thermoplastic elastomers, various types of flame retardant thermoplastic elastomers will be increasingly used in various industries and play an important role.

Especially the new energy automobile and other industries to improve the flame retardant requirements of the material, the flame retardant polymer materials of all types of high requirements, so the development of new technologies and new materials for flame retardant thermoplastic elastomers is also a hot spot of great concern at present.

As thermoplastic elastomers are widely used in various industries, there is an increasing demand for their flame retardant properties. With its profound technical accumulation in the flame retardant field, YINSU Flame Retardant Company has developed a series of elastomer flame retardant products. These include highly efficient ADP, red phosphorus masterbatch that provides excellent flame retardant effect, and red phosphorus compound flame retardant with excellent performance. In addition, YINSU has also introduced antimony trioxide replacement agents, which are designed to provide more environmentally friendly and efficient flame retardant solutions.

These innovative products not only meet the market demand for high-performance flame retardant materials, but also provide a strong guarantee for the safe application of elastomer materials. YINSU Flame Retardant's products, with their excellent performance and environmental advantages, are gradually becoming the new choice in the flame retardant industry.