Modification of PET Blended Spinning

With the rapid increase in China’s PET fiber production and the differentiation efforts undertaken by PET fiber manufacturers using the slice-spinning process to ensure their survival, coupled with the fact that China still lags significantly behind international advanced technologies in the production of high-end, differentiated, and functional PET, the development of high-value-added, functional varieties has become an urgent issue.

II. Definition and Characteristics

PET blend modification refers to the process of combining two or more polymers, including PET, in appropriate proportions under specific conditions—such as temperature and shear stress—through melt blending to form polymer alloys or blends with new properties.

Fibers produced through blend spinning generally combine or complement the characteristics of the original polymers, or place one polymer in a microphase-separated state while dissolving the other polymer phase to produce ultrafine fibers.

III. Advantages

In the past, modifiers were typically added during the esterification and polycondensation processes to achieve physical or chemical modification of PET, thereby producing differentiated and functionalized PET (e.g., flame-retardant PET, cationic dye-dyeable PET, etc.). However, this method suffers from a limited variety of products, inflexibility in switching product types, a large amount of intermediate by-products, and high production costs. In contrast, producing a variety of differentiated and functionalized fibers through the co-spinning of PET and modifiers effectively resolves these issues. The production of differentiated fibers using this method offers significant market competitiveness and will substantially enhance China’s technological capabilities in the production of high-capacity, direct-spun PET fibers.

Production of Semi-Matte POY Yarn

The blending method is used to distribute flame-retardant materials in granular form within the fibers; however, existing research indicates that this granular distribution directly affects the crystallinity and uniformity of the fiber material, resulting in reduced fiber strength and a shorter service life;

IV. Blending Partners for Modified PET Biodegradable Polyester Fibers

In recent years, the development of biodegradable polyester fibers has received increasing attention. Many researchers have copolymerized polyethylene terephthalate (PET) with polyethylene glycol (PEG), polybutylene succinate (PBS), and other materials to improve the degradation properties of polyester, achieving some progress. However, excessive addition of these additives impairs spinnability, and while degradation performance is ensured, mechanical properties cannot be guaranteed. Additionally, attempts have been made to blend PET with polylactic acid (PLA) and polyhydroxybutyrate (PHB) for spinning; however, due to prohibitively high costs, these materials have not gained widespread adoption, limiting their application and development.

V. PET and Polyhydroxyalkanoate (PHA) Blends

Preparation of Blended Fibers

Prior to spinning, the PET-PHA blend pellets were dried in a drum-type vacuum oven at 100°C for 24 hours under vacuum, ensuring the moisture content of the pellets remained below 50 µg/g.

Effects of Modification

a. As PHA is added, the spinnability of the blend system decreases; the higher the PHA content, the poorer the spinnability.

b. With the addition of PHA, the melting peak of the fiber broadens and the melting temperature decreases. A small peak begins to split off below the main melting peak; when the mass fraction of PHA reaches 2%, the melting peak splits into two.

c. As the PHA content increased, the crystallinity of the blended fibers decreased, and both the fiber orientation and f. values decreased; the fibers’ moisture absorption improved; the tensile strength of the fibers decreased, and the maximum elongation at break increased.