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Comprehensive analysis of TPU

Comprehensive analysis of TPU
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  • Categories:Industry news
  • Author:
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  • Time of issue:2021-10-25 15:04
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(Summary description)

Comprehensive analysis of TPU
Top

(Summary description)

  • Categories:Industry news
  • Author:
  • Origin:
  • Time of issue:2021-10-25 15:04
  • Views:
Information
 

 

 

01

 

什么是弹性体?

The so-called elastic body refers to the glass transition temperature is lower than room temperature, elongation at break >50%, after the withdrawal of external force better recovery of polymer materials. And vitrification temperature higher than room temperature polymer materials called plastics. In the elastomer, the elongation at break is larger (>200%), the 100% fixed elongation stress is smaller, and the better elasticity can be called rubber. Therefore, elastomer is a more extensive kind of polymer material than rubber.

 

02

 

什么是聚氨酯弹性体?

Polyurethane, or PU for short, is a kind of polymer material containing more repeated carbamate groups (-NHCOO-) in the molecular chain. Polyurethane elastomer is a special kind of elastomer. From the perspective of molecular structure, polyurethane elastomer is a kind of block polymer. Generally, it is composed of oligomer polyol flexible long chain to form a soft segment, and diisocyanate and chain extender to form a hard segment, and the hard segment and soft segment are arranged alternately to form repeating structural units. In addition to polyurethane containing ammonia ester groups, hydrogen bonds can be formed within and between molecules, and the soft and hard segments can form microphase regions and produce microscopic phase separation. These structural characteristics make polyurethane elastomers with excellent wear resistance and toughness, known as "wear-resistant rubber". Polyurethane elastomers according to the molding process of the products can be roughly divided into three categories: one is the pouring polyurethane elastomer (CPU), two is the thermoplastic polyurethane elastomer (TPU), three is the mixing type polyurethane elastomer (MPU).

 

03

 

什么是热塑性聚氨酯弹性体?

Thermoplastic PU (TPU for short), also known as PU thermoplastic, is a linear block copolymer composed of oligomer polyol soft segment and diisocyanate-chain extender hard segment. It is a kind of polyurethane elastomer that can be plasticized by heating and dissolved by solvent.

VCG41165773698.jpg

 

04

 

TPU的特点

Compared with general plastics and rubber materials, TPU has a wide range of hard layer, outstanding mechanical properties, excellent high/low temperature resistance, good processing performance, excellent environmental protection performance, strong plasticity, strong designability, good transparency and other excellent characteristics. It has both the high elasticity of rubber materials and the high strength of engineering plastics. Because of its excellent performance and wide application, it has become one of the important thermoplastic elastomer materials. Compared to CPU and MPU, the molecular chain of TPU is basically linear, with little or no chemical cross-linking in the chemical structure. There are many physical crosslinks formed by hydrogen bonds between linear polyurethane molecular chains, which strengthen the morphology of TPU, thus giving it many excellent properties, such as high modulus, high strength, excellent wear resistance, chemical resistance, hydrolysis resistance, high and low temperature and mold resistance.

 

05

 

TPU的结构

TPU is A (AB) type block linear polymer, A stands for high molecular weight polymer polyol poly (ester or polyether, molecular weight 1000 ~ 6000), known as long chain; B stands for 2-12 straight chain carbon diols, called short chains. In the structure of thermoplastic polyurethane elastomer, A chain segment is called soft chain segment, with flexible and soft characteristics, so that TPU has extensibility; The ammonia ester chain generated by the reaction of B chain segment and isocyanate is called hard chain segment, which has rigid and hard properties. People make TPU products with different physical and mechanical properties by adjusting the proportion of A and B chain segments.

 

06

 

TPU的分类

According to the soft segment structure can be divided into polyester type, polyether type and butadiene type, they contain ester group, ether group or butadiene group respectively. According to the hard segment structure, it can be divided into ammonia ester type and ammonia ester urea type, which are obtained by diol chain extender or diamine chain extender respectively. The common division is divided into polyester type and polyether type.

 
 

The difference between polyether type and polyester type TPU

 

 

Polyether type (Ether) : high strength, hydrolysis resistance and high resilience, good low temperature performance. Polyester (Ester) : good tensile properties, flexural properties, friction resistance, solvent resistance and high temperature resistance.

 

(2) performance comparison tensile strength, tear strength, wear resistance, drug resistance, transparency: polyester > polyether bacterial resistance, low temperature impact: polyester < polyether system

 

07

 

TPU合成原料有哪些?

(1) Polymer diol is a large molecule diol with double functional groups in the molecular weight range of 500 ~ 4000. Its content in TPU elastomer is 50% ~ 80%, which plays a decisive role in the physical and chemical properties of TPU. Suitable for TPU elastomer polymer diols are polyester and polyether two categories: polyester has poly tetramethylene adipate diol (PBA), poly ε hexanolide diol (PCL), poly hexamethylene carbonate diol (PHC); Polyether category of poly oxide propylene ether diol (PPG), tetrahydrofuran all polyether diol (PTMG).

 

(2) The diisocyanate has a small molecular weight but outstanding function, which not only connects the soft segment and the hard segment, but also endodes TPU with various good physical and mechanical properties. The diisocyanate suitable for TPU includes: Diphenylmethane diisocyanate (MDI), 4,4' -dicyclohexylmethane diisocyanate (HMDI), p-phenyldiisocyanate (PPDI), 1, 5-naphthalene diisocyanate (NDI), p-phenyldimethyl diisocyanate (PXDI), etc.

 

(3) The chain extender has a molecular weight of 100 ~ 350, which is a small molecule dialcohol. The chain extender with a small molecular weight and an open chain structure without substituent group is conducive to TPU obtaining high hardness and high scalar quantity. The chain extenders suitable for TPU are: 1,4 butanediol (BDO), 1,4 pairs (2 hydroxyethoxy) benzene (HQEE), 1,4 cyclohexane dimethanol (CHDM), p-phenyldimethyl diol (PXG), etc.

 

08

 

TPU的合成

TPU can be divided into bulk polymerization and solution polymerization according to different synthetic processes.

图 生产氨酯基的反应

In bulk polymerization, it can be divided into pre-polymerization and one-step polymerization according to whether there is pre-reaction. The pre-polymerization method is to react diisocyanate and macromolecule diol for a certain time, and then add chain extension to produce TPU. TPU is synthesized by mixing macromolecules of diol, diiso-acid ester and chain extender in one step. Solution polymerization is to dissolve diisocyanate in solvent first, then add macromolecule diol to make it react for a certain time, and finally add chain extender to generate TPU. Soft segment type, molecular weight, hard segment or soft segment content and TPU aggregation state affect the density of TPU, and the density is about 1.10~1.25, no significant difference from other rubber and plastics. The density of polyether TYPE TPU is lower than that of polyester type TPU at the same hardness.

 

09

 

TPU是如何加工的?

Synthetic TPU particles need to be processed in a variety of ways to form the final product, mainly using melting method and solution method for TPU processing. Melt processing is used in the plastic industry commonly used processes: such as mixing, calendering, extrusion, blow molding and molding (including injection, compression, transfer and centrifugal, etc.); Solution processing is a solution made of granules dissolved in solvent or directly polymerized in solvent and then coated and spun. TPU final products generally do not need to be vulcanized crosslinking reaction, can shorten the production cycle, waste materials can be recycled and reused.

 

10

 

TPU作为增韧剂的改性应用

In order to reduce the product cost and obtain additional properties, TPU as a common toughening agent can be used to toughen a variety of thermoplastics and modified rubber materials. Because polyurethane is a highly polar polymer, it can be compatible with polar resins or rubber, such as chlorinated polyethylene (CPE) can be used to make medical products; Mixing with ABS can be used instead of engineering thermoplastics; With polycarbonate (PC), oil resistance, fuel resistance, impact resistance and other properties, can be used to make car body; The toughness can be improved when used with polyester. In addition, it is compatible with polyvinyl chloride, polyformaldehyde (POM) or polyvinylidene chloride; Polyester polyurethane can be compatible with L5% nitrile rubber or 40% nitrile rubber/PVC blends; Polyether polyurethanes are also compatible with 40% nitrile/PVC blends; It can also co-accommodate acrylonitrile styrene (SAN) copolymer; And reactive polysiloxane can form an interpenetrating network (IPN) structure. Most of the above - mentioned blends have been officially produced. In recent years, there are increasing domestic studies on the toughening of POM by TPU. On the one hand, the blending of TPU and POM improves the high temperature resistance and mechanical properties of TPU. On the other hand, TPU has a significant toughening effect on POM. The POM alloy with TPU changes from brittle fracture to ductile fracture. The addition of TPU also gives shape memory property to POM. The crystalline region of POM is the stationary phase of shape memory alloy, and the amorphous region of TPU and POM is the reversible phase. When the recovery temperature is 165℃ and recovery time is 120s, the recovery rate of POM alloy is more than 95%, and the recovery effect is the best. TPU is not compatible with non-polar polymer materials such as polyethylene, polypropylene, ethylene-propylene rubber, butadiene rubber, isoprene rubber or waste rubber powder, so it can not be used to make good composite materials. Therefore, for the latter, surface treatment methods such as plasma, corona, wet chemistry, bottom coating, flame or reactive gas are often used. For example, American air products and chemical companies on the molecular weight of 3 ~ 5 million ultra high molecular weight polyethylene fine powder, F2 / O2 active gas surface treatment, and 10% ratio added to the polyurethane elastomer, can significantly improve its bending modulus, tensile strength and wear resistance. In addition, F2 / O2 reactive gas surface treatment can improve the stiffness and tear toughness of the 6 ~ 35mm directional extension fiber.
 

11

 

TPU应用领域有哪些?

In 1958, American Goodrich Chemical Company (now renamed Lubrizol) registered the TPU product brand Estane for the first time. After 40 years, more than 20 product brands came out around the world, and each brand has several series of products. As an elastomer with excellent performance, TPU has a wide range of downstream products, which are widely used in daily necessities, sporting goods, toys, decorative materials and other fields. Here are a few examples.

 

(1) SHOE material TPU is used for shoe material mainly because of its excellent elasticity and wear resistance. Footwear products containing TPU are much superior to ordinary footwear products in terms of comfort, so they are widely used in high-grade footwear products, especially some sports shoes and casual shoes.

 

(2) hose because TPU hose has soft, good tensile strength, impact strength and high and low temperature resistance, so in China TPU hose is widely used as gas and oil hose for aircraft, tanks, cars, motorcycles, machine tools and other mechanical equipment.

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(3) Cable TPU provides tear resistance, wear resistance and bending characteristics, high and low temperature resistance is the key to cable performance. Therefore, in the Chinese market, advanced cables such as control cables and power cables with TPU, used to protect the design of complex cable coating materials, the use is increasingly widespread.

 

(4) medical TPU is a safe, stable, high-quality PVC material replacement, there will be no chemical harmful substances, such as phthalates migrated to medical catheter or medical bag of blood or other side effects, in the liquid level and development of extrusion and injection molding grade TPU, simply by existing PVC equipment slightly debugging can be easy to use.

 

(5) Cars and other vehicles with nylon fabric on both sides of extruded polyurethane thermoplastic elastomer, can be made carrying 3 to 15 people of inflatable combat attack raft and reconnaissance raft, its performance is far better than vulcanized rubber inflatable raft; Fiberglass reinforced polyurethane thermoplastic elastomers can be used to make body parts such as car side moulds, door skins, bumpers, friction strips and grills.

 

 

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