PPDI-type thermoplastic polyurethane elastomers
Compared with traditional diphenylmethane diisocyanate (MDI) type and dimethyl biphenyl diisocyanate (TODI) thermoplastic polyurethane polyurethane material, p-phenylene diisocyanate (PPDI) type thermoplastic polyurethane elastomer has greatly expanded. The temperature range for the application of polyurethane materials.
Due to the symmetry of the PPDI molecular mechanism and the lack of a sterically hindered suspension group, the simple diisocyanate is excellent in hard segment chain stacking efficiency and good phase separation. In terms of stoichiometric ratio, although PPDI and MDI have similar formulation, hardness and modulus properties compared to TODI, the isocyanate has a lower molar ratio of polyol to polyol in PPDI. This trend reflects the inherent lower steric resistance and higher stacking efficiency for benzene structures. These properties make high-elastic PPDI-type thermoplastic polyurethane materials ideal for use in industries that require the lowest loss and high heat resistance. Test data indicates that PPDI-type thermoplastic polyurethane elastomers have unique dynamic properties and all heat resistance is improved, which will expand the application of thermoplastic polyurethane elastomers in key projects. PPDI technology also plays an increasingly important role in the hydraulic sealing process. In the hydraulic sealing process, the heat resistance and pressure resistance of the sealing material is a major engineering problem
The polyurethane industry has produced many chemical innovations over the past few decades. Most of these innovations are related to the commercialization of a large number of new chain extenders, and a few are related to the soft segment chain of polyols. In the early 1990s, the advent of DuPont Helen® PPDI (p-phenylene diisocyanate) opened the door for polyurethane technicians.
The material department of Ningbo CL Sealing Co., Ltd. mainly uses the injection molding process, and has started research on the use of PPDI in the field of thermoplastic polyurethane elastomer (TPU). It has been found that, in most cases, the PPDI type hard segment chain is coupled with polycaprolactone polyol, which is more flexible than the traditional diphenylmethane diisocyanate (MDI) type and dimethyl biphenyl diisocyanate (TODI) type polyurethane. Formulated to improve the heat resistance and hysteresis of TPU.
The basic physical properties of the three TPUs are listed in Table 1. All three compounds have excellent tensile properties and the Shore A and Shore D hardness ranges are narrow.
Based on the initial test results, the PPDI-type TPU showed excellent performance in terms of compression set and Bashore elasticity in two key areas. The compression set value means that the PPDI type material performs well in high temperature applications.
The Vicat softening point of each compound was determined according to the ASTM D-1525-91 test method by injecting one unit of VICAT / CSI using a standard needle having a cross-sectional area of 1 mm 2 (Fig. 2). The temperature at which the material is pierced by 1 mm is the Vicat softening temperature of the material. The heat distortion temperature value was measured by the ASTM D648-82/88 method using a CSI type HDV3 thermal deformation tester (Fig. 3). The sample was die cut and adjusted according to ASTM D-618 method. Both groups used a heating rate of 120 ° C / hour. The Vicat softening temperature measured by the PPDI sample was 198 ° C, which was significantly improved compared to the other two groups of materials. The thermal deformation value of the PPDI sample indicates an improvement over the TODI sample material; there is a clear advantage over the corresponding MDI compound.
Tensile strength values were tested at high temperatures using the Instron Environmental Tensile Test Chamber (Figure 4). The samples were conditioned and tested at room temperature, 100 ° C, 130 ° C and 150 ° C, respectively. The values were also tested at 100% modulus and 300% modulus (Figures 5 and 6). The values obtained still reflect that the PPDI type TPU has higher heat resistance than the pair of MDI and TODI type thermoplastic polyurethane elastomers.
The hot pants tear value was measured by the ASTM D-1938 method using the Instron Environmental Test Chamber (Figure 7). The samples were tested at room temperature, 100 ° C, 130 ° C and 150 ° C, respectively. At room temperature, the PPDI type TPU original pant tear value was 590 pli, showing the initial tear properties of the polymer under ambient conditions. The PPDI type TPU maintained the same thermal tear properties over the entire temperature range studied.
Due to its inherently simple rigid chemical structure,Ningbo CL Sealing Co.,Ltd's PPDI (p-phenylene diisocyanate) makes it possible to prepare thermoplastic polyurethane elastomers with extraordinary heat resistance. Compression set, Vicat softening temperature and tensile strength data verify that the heat resistance of PPDI type TPU far exceeds that of traditional materials. More notably, the loss modulus, Tan δ and power measurements indicate that PPDI-type materials can redefine the role of TPU technology in future dynamic material engineering techniques.
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