Effect of hot pressing/melt mixing on the properties of thermoplastic polyurethane

Abstract

In-depth understanding of the influence of hot pressing and melt processing on the properties of thermoplastic polyurethane (TPU) is critical for effective mechanical recycling of TPU scraps. Therefore, this study focused on the effects of hot pressing and melt mixing on molecular weight (MW), polydispersity index (PDI), melt index (MI), characteristic IR peaks, hardness, thermal degradation and mechanical properties of TPU. The original TPU pellet (o-TPU) showed two broad peaks at lower and higher MW regions. However, four TPU film samples, TPU-0 prepared only by hot pressing of o-TPU pellet and TPU-1, TPU-2 and TPU-3 obtained by hot pressing of melt mixed TPUs (where the numbers indicate the run number of melt mixing), exhibited only a single peak at higher MW region. The TPU-0 film sample had the highest M n and the lowest PDI and hardness. The TPU-1 film sample had the highest M w and tensile modulus. As the run number of melt mixing increased, the peak-intensity of hydrogen bonded C=O stretching increased, however, the free C=O peak intensity, tensile strength/elongation at break and average MW decreased. All the samples showed two stage degradations. The degradation temperatures of TPU-0 sample (359 o C and 394 o C) were higher than those of o-TPU (342 o C and 391 o C). While all the melt mixed samples degraded at almost the same temperature (365 o C and 381 o C). The first round of hot pressing and melt mixing was found to be the critical condition which led to the significant changes of M n /M w /PDI, MI, mechanical property and thermal degradation of TPU.

Self‐healing polyurethane nanocomposite films with recoverable surface hydrophobicity

“…It was found that the shape of the stress–strain curve was very similar before and after recovery, indicating good healing effect of the film. However, the mechanical property of these films decreased inevitably after heating treatment, which was in accordance with the literatures . More importantly, the healing efficiency of the film decreased after the modified SiO 2 nanoparticles was added, which showed that the addition of SiO 2 not only lowered the mechanical property but also do harm to the bulk self‐healing property.…”

Design, Modeling, Control, and Application of Everting Vine Robots

“…These off-the-shelf films come manufactured in sheets or tubes, and the two main films used in everting vine robot construction have been low density polyethylene (LDPE) (Hawkes et al, 2017 ) and thermoplastic polyurethane (TPU). LDPE has an elastic strain limit on the order of 5% (Xu et al, 2016 ), while the elastic strain limit of TPU is on the order of 50% (Lee et al, 2009 ). These materials are lightweight, airtight, and inert with respect to most liquids.…”

Effects of glass fiber on the properties of polyoxymethylene/thermoplastic polyurethane/multiwalled carbon nanotube composites

“…In POM spectrum, the peaks at 2,975 and 2,918 cm −1 are assigned to CH 2 stretching, the peak at 1,467 cm −1 is attributed to CH 2 bending and wagging, and the peaks at 1,240, 1,093, and 935 cm −1 are characteristic of COC group . In TPU1 spectrum, the peak at 3,300–3,500, 3,000–2,800, and 1,726 cm −1 are assigned to NH, CH 2 , and CO groups, respectively . All the characteristic peaks of POM and TPU1 are shown in the spectrum of the composite, confirming the formation of POM/TPU/MWCNT/GF composite.…”