| Polyester and polyamide are two types of thermoplastic fiber-forming polymer materials; both can be made into fiber products alone or be used in some differential fiber products through composite or blending melt spinning. The study on such fibers’ abilities of second melt blending forming after recycling, the compatibility and stability of blending systems, have not yet formulated and theorized or guide in actual applications, besides, the relevant research varies with different blending systems.In this paper, a torque rheometer was used to prepare bio-based polyamide(PA2)/PET in different weight ratios(10/90, 15/85, 20/80, 15/85) blending systems and different kinds of nylon(PA66, PA6, PA6/66 and PA12) and PET blending systems. We then studied the blending compatibility by methods of DSC, FTIR, POM, SEM, TEM and XRD etc. For PA2/PET blending, the research results showed that PA2 as dispersed phase, which distributed in the PET continuous phase randomly with a “sea-island” distribution structure. As the relative amount of PA2 increased, the particles size of PA2 increased and the decentralized configuration turned uneven, the compatibility of PA2/PET also became worse. The PA2 and PET phases crystallized respectively and influenced each other during the blending process, resulting in crystalline phase separation. PA2 played the role of heterogeneous nucleation. The crystallization degree of the blending system was lower than the total crystallization degree of pure PET and PA2. The whole crystallization degree decreased and no γ crystal was formed during the process. Two melting peaks(TM1/TM2; TM4/TM3) are shown in the DSC curve during both the first and the second heating processes, and TM3<TM1, TM4<TM2. In PA2/PET systems of different ratios, the ester chain and amide chain fractured and restructured as the blending time extended and an ester-amide exchange reaction occurred between the two components. Due to the ester-amide exchange, blending systems had a little compatibility, and the compatibility was directly related to the PA2 content and blending time.For the PA/PET blending systems with different chain structures, the dispersed phase PA distributed in the PET continuous phase in the state of ellipsoid particle with different particle size. The DSC curve showed that the melting peak were very close and even overlap for PA66/PET and PA2/PET blending systems. There are two separate melting peaks and crystallization peaks in PA6/PET, PA12/PET, PA2/PET and PA6/66/PET blending systems, but PA66/PET only had one crystallization peak, this was possibly because of co-crystallization of PA66/PET. PET crystallization temperature increased rapidly, with crystallization temperature between 203~208℃, and PA crystallization temperature was going down. While the rest of PA/PET system crystallized respectively and influenced each other, PA acted as heterogeneous nucleation during the blending process. XRD test showed that PA6/66/PET blending system compared with pure PET, crystallinity decreased obviously. For PA12/PET blending system, there was a little peak in the 22.6°, the system was mainly imperfect γ crystal and the crystallinity was very low. PA66/PET blending system formed co-crystallization system, and the crystallinity was also very low. There was almost no γ crystal of PA2/PET in the blending process. The crystallization peak of PET/PA6 system for α1 disappeared, the peak for α2 had become wider. Compared with pure PET and PA6, The crystallinity of PA6/PET reduced. The rank of the crystallization ability of PET was: PA2/PET> PA6/PET>PA6/66/PET>PA12/PET>PA66/PET. The FTIR test showed that ester-amide exchange reaction occurred in all the blending during the blending process. |
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