Toughening And Reinforcing Modification, Structure And Properties Of Poly (Butylenes Terephthalate)

At present, it has been an important project to obtain a new polymer material with excellent properties by means of modification of existing polymer materials. For structural polymer materials, strength and tough are the most important properties. Poly(butylenes terephthalate) has been an important one of the five engineering thermoplastics due to its good combination of properties such as high rates of crystallization, solvent resistance and excellent processability, used widely in auto, electronics industry and so on. But low notched impact strength of pure PBT limits its wider uses. Blending PBT with an elastomer to improve its impact strength is often performed. However, a sharply reduced strength of the overall blends is inevitable when high impact strength is obtained by blending PBT with an elastomer alone. How to obtain higher tensile or yield strength as the impact strength of material increases has been an object hunted for by many polymer studiers. In this work, toughening and reinforcing modification of PBT by blending with elastomers (POE-g-MAH, E-MA-GMA) and CaCO3 particles, polypropylene, polycarbonate respectively, by blending with ACR and polycarbonate as well was investigated. The mechanical properties, microstructure and the relationship between them were also carefully studied. The toughening mechanism of soft shell-hard core particles releasing its stress by a soft mode was proposed. The main works and conclusions were listed as following:1. Two types of functional polyolefin elastomers (POE-g-MAH, E-MA-GMA) have significant toughening effect on PBT. When elastomer content was up to 15%, britlle-to-ductile transition of the two blends took place. Their notched impact strength increased from 7.5KJ/m2 for pure PBT to 50KJ/m2 and 53.9 KJ/m2 respectively. When elastomer content continuously increased to 20%, the notched impact strength of the two blends increased to 59.8KJ/m2 and 91KJ/m2 respectively. But the tensile strength of them decreased sharply from 59.5Mpa for pure PBT to 40Mpa or less. PBT/E-MA-GMA blend has better strength and tough compared with PBT/POE-g-MAH blend. DSC results showed that two types of elastomers have different compatibilities with PBT. E-MA-GMA and PBT have stronger interaction of the blend components.2. Three-phase composite was obtained by blending PBT with elastomer and CaCO3 particles. The influences of type of elastomers, processing methods, size of CaCO3 particles, content of elastomer and CaCO3 particles on the phase morphology and properties of PBT were investigated. A study of phase morphology of PBT/POE-g-MAH/nano-CaCO3 composite by means of scanning electron microscopy (SEM) showed that the domains size of nano-CaCO3 capsulated by POE-g-MAH elastomer in composite when PBT was mixed directly with POE-g-MAH and nano-CaCO3 together or with nano-CaCO3 capsulated by POE-g-MAH elastomer is large. The mechanical properties of the composite are worse. The PBT/E-MA-GMA/CaCO3 composite which were mixed directly with CaCO3 and E-MA-GMA together have better impact strength and tensile strength than that of PBT mixed with CaCO3 capsulated by E-MA-GMA. A study of phase morphology revealed that composite of PBT mixed directly with micro-CaCO3 and E-MA-GMA together has few domains of capsulation structure. And the domain size of dispersed phase is small. However, there are always dispersed particles of capsulation structure in PBT/ E-MA-GMA/nano-CaCO3 when mixed directly with E-MA-GMA and nano-CaCO3 together or mixed nano-CaCO3 capsulated by E-MA-GMA. E-MA-GMA and micro-CaCO3 have synergistic toughening effect on PBT when mixing them directly with PBT together.3. Four types of impact modifiers with soft shell-hard core structure were prepared by melt blending POE-g-MAH with two types of PP through a twin screw extruder. The novel impact modifier(POEg2) with POE-g-MAH/PP ratio of 70/30 has most toughening effect. When POEg2 content was up to 15%, the notched impact strength increased from 7.5KJ/m2 for pure PBT to 51.2KJ/m2, which is approximately equal to that...