Common PBT material modification and application
The shortcomings of PBT materials, such as inadequate flame retardancy, insufficient heat distortion temperature, and insufficient notched impact strength, are becoming more and more visible as the amount of PBT resin keeps rising. Relevant professionals continue to tweak it to make up for the pure PBT resin's poor performance and increase its application domains. Glass fiber reinforced, flame retardant modified, and blended alloy modified goods are the three primary categories of PBT modified products available in China at the moment.
1. Strengthened alteration
The bonding force between glass fiber and PBT resin is strong when glass fiber is added. PBT resin can keep its initial benefits, such as chemical resistance and processability, by adding a particular proportion of glass fiber. It can also improve its mechanical qualities and get over PBT resin's notch sensitivity.
Automobiles, electronics, and electric tools are where these things are most frequently found. The application fields and the percentage of glass fiber are also varied.
On the keyboard, glass fiber reinforced PBT material was used
2. Flame-resistant alterations
Crystalline aromatic polyester is PBT. Its flame retardancy is UL94HB if no flame retardant is used. It can only achieve UL94V0 after adding a flame retardant.
Halogen flame retardants including bromide, Sb2O3, phosphide, and chloride are often utilized. The most widely used PBT flame retardant has traditionally been decabromodiphenyl ether. All parties are searching for alternatives to decabromodiphenyl ether now that its usage has been outlawed, but there hasn't been any performance benefit.
But as a general trend, big businesses have recently prioritized halogen-free flame retardant technology. It possesses lower density, superior electrical characteristics, and same mechanical qualities to existing materials when compared to the current halogen-based PBT. The market is still dominated by halogen-containing flame-retardant products, nevertheless, because there aren't any affordable, viable alternatives.
3. Modification of mixed alloys
PBT is typically blended with other polymers to increase heat resistance, enhance warping deformation brought on by shrinkage during molding operations, and increased impact strength.
It is frequently modified at home and abroad through blending. The primary polymers used to blend-modify PBT are PC, PET, etc. Automobiles, electronics, and electric tools are where these things are most frequently found. The application fields and the percentage of glass fiber are also varied.
Benefits: Polycarbonate (PC) has great performance and may be melt-blended with PBT in any ratio as long as the temperature is higher than the point at which PC turns into glass, which is 150°C. The combined PC/PB alloy may compensate for the inadequacies of PBT's notched impact strength, impact resistance, and heat resistance as well as the inadequate formability and wear resistance of PC.
Due to the fact that PBT is a crystalline polymer and PC is an amorphous polymer, their alloy represents a typical system in which amorphous and crystalline materials are blended. As a result, phase separation is likely to happen during blending modification, leading to poor interface bonding and compatibility, poor sex, and other drawbacks.
Therefore, to destroy the PBT crystal and increase system compatibility, a particular quantity of compatibilizer will be applied during the blending process. During the process of mixing tougheners and glass fibers, a specific quantity of compatibilizer will also be added in order to further enhance the toughness and strength of the PC/PBT alloy.
Benefits: PBT and Polyethylene Terephthalate (PET) have comparable chemical compositions and solubility properties. Good compatibility exists between the two combined systems, and only one glass transition temperature Tg is visible.
Cons: When PBT and PET are combined, a block copolymer is produced as a result of a chemical process. These block copolymers are susceptible to transesterification, which results in the formation of a random copolymer at a later stage, lowering the molecular weight and mechanical characteristics of the polymer and eventually lowering the alloy's quality.
Therefore, a certain amount of chain extender can be added to the blend system to react with the carboxyl groups of the two, connect PBT and PET, and generate block copolymers of PBT-PET, PET-PET or PBT-PBT. The relative molecular mass and intrinsic viscosity of the system are increased within a short period of time, and the resulting PET/PBT alloy has excellent properties such as high strength, good rigidity, high heat distortion temperature, good dimensional stability, and good surface gloss.
Figure PBT/PET alloy material used in car lamp trim
Some materials with higher compatibilization effects, such as PU, PP, ABS, SBS, EPDM, POE, ASA, EVA, and elastomers, have also been tested to melt mix and alter PBT in addition to the materials already stated. Some of these materials will also be biodegradable. When PBT, PCL, and PBS bioresins are combined, a PBT alloy with an environmental protection function may be produced.