Preparation, Structure And Property Study Of Poly(Trimethylene Terephthalate) Nanocomposites

Poly (trimethylene terephthalate)(PTT) is a kind of new polyester produced commercially in the middle1990s, and it is widely used in textile, packaging, engineering plastics and other fields. However, it shows some shortcomings such as low moisture absorption, poor dyeability, low strength, poor flame retardancy and barrier property in its application. In recent years, the blending or hybrid modification for the pristine polymer materials is one of the simple and effective modification methods, and has been extensively used in the studies on polymer materials. In this paper, cellulose acetate butyrate (CAB) and montmorillonite (MMT) were chosen as organic and inorganic additives to modify PTT, respectively and together. PTT/CAB blends and their fibers, PTT/MMT nanocomposites and PTT/CAB/MMT ternary nanocomposites were prepared correspondingly through melt mixing by twin screw extruder and melt spinning. The main research contents and conclusions are as follows:(1) Environment friendly and renewable CAB was adopted to modify PTT and PTT/CAB blends containing3-10wt%CAB were prepared. The interactions between their molecules and their morphological structures were characterized by infrared spectroscopy (IR) and scanning electron microscope (SEM), and it was found that a certain degree of hydrogen bonds form between carbonyls of PTT and hydroxyls of CAB in the blending system, and CAB at nanometer size (100-300nm) in spherical particle shape evenly disperses in the PTT matrix. Nonisothermal crystallization behavior of PTT/CAB blends was studied by differential scanning calorimetry (DSC), and it was indicated that when CAB exsits.the crystallization temperature of PTT during cooling from melt moves to higher temperature, half crystallization time bcomes shorter and its crystallization rate constant increases, thus, CAB has played a role of heterogeneous nucleation. Rheological behavior of PTT/CAB blends was studied by capillary rheometer. It was showed that the addition of3wt%CAB makes the viscosity of PTT melts lower and improves the processing flow property of PTT, which is advantageous to the forming process of PTT. PTT/CAB blend fibers with practical values were successfully obtained through melt spinning, and the tensile strength of the fibers is more than2.8cN/dtex. Hydroscopicity and dyeability of the blend fibers were evaluated, and it is found that the hydroscopicity of PTT/CAB blend fibers rises gradually and their dyeing effects are more and more obvious with content of CAB increasing; when10wt%CAB was added, the moisture absorption increases by more than50%and the dye uptake increases by nearly10%. It can be inferred that the blend will have a better application prospect in the field of textile.(2) A natural laminar nanometer material, MMT, was adopted to modifiy PTT, and PTT/MMT nanocomposites with1-5wt%MMT were prepared. The morphological structures of the composites were characterized by X-ray diffraction (XRD), SEM and transmission electron microscope (TEM), and it was showed that the layer spacing of MMT in PTT/MMT system increases significantly, from2.348nm of original MMT to4.413nm, and MMT layer thickness is about a dozen to tens of nanometers, which proved that the intercalation compound of PTT and MMT is achieved by melt blending method and PTT/MMT nano-scale composites have been prepared successfully. The rheological properties of PTT/MMT nanocomposites were studied, and the results showed that1-3wt%MMT makes the processing flow properties of PTT better. The flame retardancy of PTT/MMT nanocomposites was tested, and the results indicated that the addition of MMT significantly improves the melting and droping behavior of the composites during burning, when2wt%MMT was added, no molten drops flows down in the process of PTT/MMT combustion. The barrier property of PTT/MMT composite sheet has been improved obviously compared with that of PTT sheet, when MMT content is5wt%, the air permeability coefficient of PTT/MMT composites reduces by about51%compared with that of PTT. PTT/MMT composites increased the additional value of PTT products in the plastic application field, and they will have an advantage especially as packaging and building materials. (3) CAB and MMT were used together to modify PTT, and PTT/CAB/MMT ternary nanocomposites containing2wt%MMT and3-10wt%CAB were prepared, and their structures and properties were studied. SEM and TEM testing results indicated that in this system, CAB in spherical particle shape and MMT in laminar shape both at nanometer size evenly disperse in PTT. The mechanical property research results showed that each mechanical performance index is better than that of PTT; and compared with the system of PTT/MMT composites, the addition of CAB makes up for the loss of impact toughness of the composites, that is to say, both the impact strength and elongation at break of the ternary nanocomposites increase as CAB content increases, at the same time, their tensile strength and moduli are at a good level. Oxygen index determination results showed that the melting and droping property of PTT/CAB/MMT nanocomposites is improved significantly, and no molten drops appear, combustion coke does not drop when burning. This suggests that the addition of MMT and CAB improves the integrated performance of PTT materials.