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Benzobisoxazole-containing diamine, 2, 6-Di(p-aminophenyl)benzo [1.2.5.4] bisoxazole (DIABO), was derived from diaminodihydroxybenzene dihydrochloride (DADHB·2HCl) and p-aminobenzoic acid (PABA) via condensation reaction. The structure of DIABO was confirmed through FTIR, 1H NMR, x-ray diffraction (XRD) and UV-Vis spectra, etc. The curing behavior of diglycidyl ether of bisphenol A (DGEBA) and DIABO as curing agent was investigated using differential scanning calorimetry (DSC). Dynamic kinetic parameters were calculated by using Kissinger's and Ozawa's methods, respectively. The glass transition temperatures of cured system, DGEBA/DIABO, DGEBA/DIABO/DDS (cured with mixtures of DIABO and diaminodiphenyl sulfone (DDS)) and DGEBA/DDS, were 213°C, 193°C and 175°C, respectively, based on torsional braid analysis (TBA). The integral procedure decomposition temperatures (IPDT) were 885°C, 734°C and 604°C, respectively. Char yields at 572°C were 39.82%, 24.66% and 21.57%, respectively. Hydrothermal ageing of cured resins was also discussed. All results showed that DIABO as curing agent can remarkably improve the thermal and hydrothermal resistance of the cured epoxy resins.

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Coincidence time resolution (CTR) is an important performance parameter of clinical positron emission tomography (PET) detectors, which is dependent on the parameters of the scintillation crystal, the timing measurement methods, and the electronics. In this work, CTRs of PET detectors using dual-ended readout of segmented LYSO arrays were measured with different timing measurement methods. The detector modules were composed of LYSO arrays of 8 × 8 with a crystal size of 3.10 × 3.10 × 20 mm3 or 13 × 13 with a crystals size of 1.88 × 1.88 × 20 mm3, coupled at each end to an 8 × 8 Hamamatsu SiPM array (S13361-3050NE-08) with pixel active area of 3.00 × 3.00 mm2 and pitch of 3.20 mm. The signals of the SiPM arrays were individually read out and processed by using the TOFPET2 ASICs. The CTRs of the detectors were measured after the timing alignment of the ASICs was performed. Timing measurement methods of the dual-ended readout detector such as the average time of the two SiPMs, the faster time of the two SiPMs, the time of the back SiPM, and the time of the front SiPM were compared. The average time of the two SiPMs provides the best CTR, which is explained by a simple model about the timing measurement methods of a dual-ended readout detector. The detector with one-to-one crystal-to-SiPM coupling provides better CTR than the detector with a crystal size smaller than the pixel size of the SiPM. The best CTR of 367 ± 6 ps was obtained by using the 8 × 8 LYSO array with unpolished lateral crystal surfaces and ESR reflectors. The CTR of the dual-ended readout detector can be improved if a DOI-dependent timing correction is used.