Polybutylene terephthalate mechanical properties

Thermoplastic polyesters include polybutylene terephthalate (PBT), which possesses good slip and wear properties, resists chemicals and hydrolysis, and has excellent dimensional stability. Mechanical parts in drug delivery and filter systems are preferably made of PBT. 

The need for mechanical reinforcement has been the driving force for most of the reported work on polymer/CNT composites. In an attempt to investigate the mechanical properties of electrospun PAN/SWNT nanofibers, Ko et al. (75) have used an atomic force microscope (AFM) to measure the elastic modulus of the electrospun composite nanofibers. The obtained fiber modulus was 140 GPa, a value which is much higher than that of conventional PAN fibers (60 GPa) (75). In a somewhat related but independent study, Mathew et al. (92) also used AFM to measure the mechanical properties of electrospun polybutylene/MWNT terephthalate nanofibers. Elastic deformation of MWNTs in electrospun PEO/MWNT and PVA/MWNT nanofibers was studied by Zhou and co-workers (84), and was found to increase with an increase in the modulus of the polymer matrix. In the same study, a simplified model was also proposed to estimate the elastic modulus ratio of MWNT and polymers. To confirm the validity of their model, these authors compared the model predictions with experimental data obtained from AFM measurements. 

The electrical properties of LCPs and polybutylene terephthalate (PBT) resins are comparable although LCPs offer at least a few advantages over PBT in electric applications, i.e., low mold shrinkage, fast cycling time, ease of molding thin parts, low moisture regain, and excellent chemical and mechanical properties. 

Polybutylene terephthalate (PBT) is different from PET with the substitution of four ethylene repeat units rather than the two in PET. This feature imparts additional flexibility to the backbone and reduces the polarity of the molecule, resulting in mechanical properties similar to those of PET. PBT blends such as PBT/ASA (acry-lonitrile/styrene/acrylic ester) are popular in automotive exterior and under-hood applications. 

Engineering thermoplastic resins (ETP) are those whose set of properties (mechanical, thermal, chemical) allows them to be used in engineering applications. They are more expensive than commodity thermoplastics and generally include polyamides (PA), polycarbonate (PC), linear polyesters such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), polyphenylene ether (PPE) and polyoxymethylene (POM). Specialty resins show more specialized performance, often in terms of a continuous service temperature of 200°C or more and are significantly more expensive than engineering resins. This family include fluoropolymers, liquid crystal polymers (LCP), polyphenylene sulfide (PPS), aromatic polyamides (PARA), polysulfones (P ), polyimides and polyetherimides. 

Table 3.2 Comparison of mechanical property enhancement of three polymer matrices material [polypropylene (PP), polybutylene terephthalate (PBT) and polyamide (PA)] when employed with HNTs...

Exterior door handles are another application that has turned to plastics to balance chemical resistance and mechanical properties. Many filled thermoplastics such as blends of PC and polybutylene terephthalate (PBT), polyethylene terephthalate (PET), and nylon have been tried or used in this application, with nylon as the clear wirmer. Exterior mirror housings likewise use many thermoplastic solutions such as ABS, PC/ABS, blends of polyphenylene oxide (PPO) and polystyrene (PS), nylon, blends of PP and ethylene propylene diene monomer (EPDM), and weatherable ABS. Again, nylon clearly dominates this application in terms of volume. Many other exterior parts continue to adopt thermoplastic solutions. Figure 14 shows an impingement shield constructed from LGF PP. 

At the beginning of a thermal loading condition, the mechanical properties of polybutylene terephthalate are often influenced by the increase in crystallinity, so that, e.g., impact strength decreases because of the higher degree of crystallization. Subsequently, oxidation will cause property changes. Figure 5.199. 

The promise of large-scale low-cost fermentations from renewable resources, especially corn, has spurred interest in the United States to develop chemical production for large-volume chemicals using bio-based processes. Succinic acid can be converted by hydrogenation to 1,4-butanediol, which has a world market in excess of 500,000 metric tons. Butanediol is used to produce polybutylene terephthalate (PBT) resins that have desirable mechanical and thermal properties and are a high-performance version of polyethylene terephthalate resins (PET). Also, 1,4-butanediol is a precursor of tetrahydrofuran, which can be polymerized to polytetrahydrofuran (PTHF). Gamma butyrolactone (GBL) can also be derived from 1,4-butanediol, and much of GBL is used to manufacture the solvent N-methyl-2-pyrrolidone (Szmant 1989). 

N. Hargarter, K. Friedrich, P. Catsman (1993) Mechanical properties of glass fiber/talc/polybutylene-terephthalate composites as processed by the radlite technique. Compos. Sci. Technol. 46,229. 

The compatibilizer improves the mechanical properties of PE/starch, and addition of a plasticizer is actually detrimental to the finished products. Although PE is used here to demonstrate the results of this invention, results are practically the same with other combinations of polymer and compatibilizer as disclosed therein. Incorporation of compatibiHzer is easily accomplished by mechanical blending of the polymer, starch, and compatibilizer prior to extrusion. Typically, the compatibilizer is composed of the same polymer as the primary polymer itself. The polymer component of the compatibilizer may be selected from the group consisting of polyethylene, polypropylene, polystyrene, polybutylene, poly(styrene-ethyl-ene-butylene-stryrene), poly(ethylene terephthalate), polyvinyl fluoride, polyvinyl chloride, or derivatives thereof [6]. 

Polybutylene terphthalate (PBT) is a semicrystalline thermoplastic polyester considered as a medium performance engineering polymer. It is produced industrially in a two-step batch or continuous process. The first step involves the transesterification of dimethyl terephthalate (DMT) with 1,4-butanediol (BDO) to produce hydrobutyl terephtlate (bis-HBT) at a temperature of 200 C. The second step consists to the polycondensation of bis-HBT at 250 C to yield PBT. It exhibits both excellent electrical properties and chemical resistance. When reinforced with glass fibers, it has improved stiffness and mechanical strength. Typical uses include connectors, capacitors and cable enclosures. PBT is also used in hot appliances such as iron and kettles. 

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