Cell structure and hardness evolutions of TPU foamed sheets with high hardness via a temperature rising foaming process

Thermoplastic Laminated Composites Applied to Impact Resistant Protective Gear: Structural Design and Development

“…TPU has a structure consisting of hard and soft segments that are alternatively aligned. Hard segments provide crystallization sites while soft segments help with the expansion of the TPU composite films [ 25 , 26 ]. Specifically, the soft segments could be entangled with each other, which strengthens the blending level of TPU and MTPU subsequently.…”

Supercritical Fluid Microcellular Foaming of High-Hardness TPU via a Pressure-Quenching Process: Restricted Foam Expansion Controlled by Matrix Modulus and Thermal Degradation

“…As mentioned above, the foaming temperature is a critical factor to control foam ex pansion, and a mountain-shaped relationship between foaming temperature and foam expansion ratio has been widely reported [38]. Figure 7 summarizes the optimum foamin temperature (Tof) of TPU as a function of sample hardness [6,16,21,[42][43][44][45][46][47][48][49][50], where the com pressed CO2 was used as the blowing agent. It is seen that an increase in resin hardnes tends to increase the Tof of TPU foams.…”

“…Figure 3 shows the storage modulus (E') of HD-TPU as a function of temperature ranging from −90 • C to 180 • C. The modulus curve could be roughly divided into four regions: below 0 • C, 0-60 • C, 60-150 • C, and above 150 • C. When the temperature was below 0 • C, the decrease in the modulus was mainly due to the secondary relaxation and the motion of SSs. When the temperature was over T g of the SSs, the SSs entered the rubbery state, while the HSs were still in the glassy state [21,35]. The increase in the SS's mobility and the expansion of the free volume resulted in a slight drop in the storage modulus.…”

“…Unfortunately, the physical foaming of HD-TPU is rarely reported. In a recently published paper [21], Jiang et al investigated the foaming behaviors of three HD-TPU foams using a temperature-rising foaming method. Various parameters, i.e., saturation pressure, foaming temperature, and foaming time, were carried out to adjust the foam expansion ratio and cell structure, and a maximum expansion ratio of about 10 times was obtained for 75D-HD-TPU foam using a mild saturation (6 MPa/25 • C/24 h) and foaming (170 • C/30 s) condition.…”

Preparation and performance study of a reactive polyurethane hot-melt adhesive/CS–Fe3O4 magnetic nanocomposite film/fabric

“…TPU displays a high initial bond strength and long storage period, and can be reversibly bonded; however, its ultimate bond strength and heat and chemical resistances are poor owing to its linear structure. 16 On the other hand, reactive polyurethane hot-melt adhesive (PUR) usually refers to low-molecular-weight linear polyurethanes terminated with isocyanates. PUR contains excess isocyanate groups (–NCO) that react with atmospheric moisture to form polymers with cross-linked networks that eventually form a permanent cross-linked structure.…”