Effects of amorphous nylon on the properties of poly(butylene terephthalate) and 70/30 poly(butylene terephthalate)/nylon 6 blends

Abstract

In this work, the effects of adding small amounts of amorphous nylon (a‐nylon) on the properties of poly(butylene terephthalate)(PBT) have been studied. Miscibility and properties of PBT/a‐nylon blends were compared with those of PBT/nylon 6 blends. Blends were prepared in a twin‐screw extruder. The compositions of a‐nylon or nylon 6 were varied from 0 to 20 phr. Rheological, thermal, mechanical, and dynamic mechanical properties of the blends were examined using a capillary rheometer, a differential scanning calorimeter (DSC), a universal testing machine (UTM), and a Rheometrics Mechanical Spectrometer(RMS), respectively. The PBT showed a single endotherm around 225.4°C on the DSC thermogram at the first heating scan but exhibited a second endotherm at a temperature below that of the original endotherm at the second heating scan. When a‐nylon was added, the original endotherm was remarkably affected, but the second endotherm was not appreciably changed; i.e., the heat of fusion at the original endotherm decreased linearly with increasing a‐nylon content, meaning that the addition of a‐nylon affects significantly only the higher‐melting crystals of PBT. The impact strength of PBT was decreased with nylon 6 content but was increased with increasing content of a‐nylon. With an increase in the a‐nylon content, the tensile modulus and the flexural modulus of PBT were decreased. Of interest is, however, that the tensile strength was significantly increased with a‐nylon up to 15 phr. The melt viscosity of PBT was decreased with increasing a‐nylon content, whereas it was not significantly changed with nylon 6 addition; i.e. the addition of a‐nylon acted as a lubricant or a processing aid for PBT. The dynamic mechanical and the morphological studies showed that PBT was more miscible with a‐nylon than with nylon 6. It was also found that a‐nylon exhibited a compatibilizing effect for the PBT/nylon 6 blend of 70/30 wt% composition.

Reactive processing compatibilization of direct injection molded polyamide‐6/poly(ethylene terephthalate) blends

“…Both PA‐6 and PET have been blended with many second components. Among them, PA‐6 has been blended with polyesters 5–9. The PA‐6/PBT blends showed5–7 two T g 's.…”

Syntheses and characterization of poly(butylene terephthalate) copolyesters modified with p‐acetoxybenzoic acid

“…The main T m at higher temperatures decreases with increasing PABA concentration up to 30 mol % of PABA and then levels off, and the second small peak below the main peak increases slightly with increasing PABA content. The additional melting peak at a lower temperature is thought to arise from PBT crystals that form from the amorphous phase during annealing and that form from recrystallization of crystals that have lower melting points 23–26…”

Mechanical and dielectric breakdown properties of PBT/TPE, PBT/PBT/PET, and PBT/antioxidant blends

“…Recent developments resulted in polymer blends of PBT with PET,5–9 nylon 6,10 polycarbonate (PC),11, 12 and polytetramethyleneglycol13 to improve impact resistance at low temperatures and other mechanical properties. PET/PBT blends have high electrical insulation properties, thermal resistance, and good mechanical properties 7, 8.…”