When it comes to 3D printing, the sky is the limit. As 3D printing technology continues to advance, applications can be as far reaching as airplane and automobile parts to medical devices and even anatomically correct, biocompatible models. Although 3D printing technology is developing at a rapid pace, the technology itself is not new. It emerged in the 1980s as a means of creating rapid prototypes. In recent years the applications for 3D printed models have evolved with the available hardware, software, and printable materials. Evolving technology, paired with the creative and innovative minds of scientists, engineers, and physicians, has been the launching pad for developments within 3D printing technology specific to healthcare. One way 3D printing technology is poised to create better patient outcomes is in creating an anatomically and patient-specific models to aid in surgery and medical procedures. With the capability to 3D ...
What’s keeping you warm and dry this winter? Could it be “extreme cold weather” thermal underwear made of polypropylene fibers, which initially were developed for the U.S. Army? Polypropylene (PP) fibers have many applications. Ropes made of PP fibers float on water, because they are light and hydrophobic. They are used in diapers and medical bacteria-resistant fabric. PP fibers are even used to reinforce concrete. Compared to other synthetic and natural fibers (i.e., polyester, polyamide, acrylic, cotton, wool, and silk), PP fibers have the lowest density and moisture regain, and the highest insulation power, and stain and chlorine resistance.
Polypropylene fibers have been produced since the 1950s and found a niche in active sportswear in the 1980s. A consumer perception study of polypropylene apparel, performed by Cornell University back in 1985, revealed overall satisfaction over the apparel performance and care. The only problem was the limited color selection: PP fiber is hard to dye due to its high hydrophobicity. Traditionally coloring of polypropylene fibers has been performed during production: color is mixed in the polymer before it become a fiber.
Production of a polypropylene fiber that can be dyed using water solutions (the way polyester, nylon, and cotton are) has been a technological challenge. Over the years a number of approaches have been investigated. Although there are commercially available PP dyeable fibers (such as CoolVisions), this work is still ongoing. Researchers from Iran’s Institute for Color Science and Technology and Amirkabir University of Technology at Tehran recently published “Enhancing the Dyeability of Polypropylene Fibers by Melt Blending with Polyethylene Terephthalate” in Scientific World Journal:
Improving the dyeability of polypropylene fibres by means of chemical and physical modification methods inclusive of surface chemical reactions and functionalization, copolymerization and graft polymerizations, plasma and gamma radiation treatments, and blending of PP with polar polymers, metal compounds, inorganic nanoparticles, particularly, nanoclays, dendrimers and hyperbranched polymers, and many other additives has been widely investigated. […] Melt blending with different kinds of polymeric additives such as polystyrene, polyamides, and polyesters, prior to spinning, could be an efficient process for the dyeability modification of PP fibers. Amongst these polymers, polyesters, especially polyethylene terephthalate (PET), offer some advantages over the others, including improvement in dyeability, as well as enhancing the mechanical properties of the resultant fiber. […] Recirculation of waste polyethylene terephthalate can be a promising potential for recycling and reusing PET wastes in PP/PET blend fibers.
This approach was unconventional, as PET and PP are not compatible due to their different polarities and chemical structure, so initial blends resulted in a two-phase morphology (think of mixing oil and water). By adding “compatibilizer” (maleic anhydride grafted polypropylene) to the blend and carefuly optimizing the concentrations, the tripartite blend with desirable properties was obtained.
A variety of analytical methods was used to lead the optimization process of the polymer material. The uniform morphology of the blend was characterized by scanning electron microscopy (SEM); in situ chemical reaction of maleic anhydride with PET was confirmed by FT-IR spectroscopy; the reduction of crystallinity of the blends compared to original PP was derived from differential scanning calorimetry (DSC), and tensile strengths of some blends exceeded that of PP.
The optimized blends were used to make fibers that were dyed with commercial Terasil blue, yellow, and red dyes. Dye uptake and colorfastness were evaluated by means of spectrophotometry and polarized optical microscopy. This detailed work shows what it takes to achieve successful optimization and will hopefully result in more colorful products made of PP fibers: carpets, upholstery, clothing, geotextiles, and automotive interior fabrics.
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