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5¾ä»°µÄÓ¢Óï·Ò룡 1. On the other hand, the materials based on aliphatic diisocyanates are famous for their unchanged whiteness under ultraviolet, visible light and heat which is often the defect of those based on aromatic diisocyanates. ÁíÒ»·½Ã棬»ùÓÚÖ¬·¾×å¶þÒìÇèËáõ¥µÄ²ÄÁÏÒÔÆä¶ÀÓеİ×É«¶øÖø³Æ£¬ÇÒÆäÔÚ×ÏÍâ¹â¡¢¿É¼û¹âºÍÈÈÌõ¼þ϶¼²»»á±ä»Æ¡£¶øÕâͨ³£ÊÇ·¼Ïã×å¶þÒìÇèËáõ¥»ùµÄȱµã¡£ 2.In order to achieve optimal mechanical property, the molar ratio of TDI to total polyesters was set to be 2.1/1 to form some of the allophanate crosslinks as shown following ΪÁË»ñµÃ×îÓŵÄÁ¦Ñ§ÐÔÄÜ£¬TDIºÍ×ܵľÛõ¥µÄĦ¶û±È¶¨Î»2.1/1ÒÔÐγÉһЩëå»ù¼×Ëáõ¥µÄ½»Áªµã£¬ÈçÏÂͼËùʾ 3. However, it is regretful that Tms were decreased by 9 0C and 18 0C when molar ratios of unit of ¦Å-caprolactone to butylene succinate were 0.08 and 0.18, respectively. È»¶ø£¬ºÜÒź¶µÄÊÇ£¬µ±ÒÑÄÚõ¥ºÍ¶¡¶þËá¶¡¶þõ¥µÄĦ¶û±ÈΪ0.08 ºÍ 0.18ʱ£¬¹²¾ÛÎïµÄÈÛµãÏ·ֱð½µÁË9 0C ºÍ 18 0C¡£ 4. Meanwhile, Tms were reduced by 5 0C, 10 0C and 21 0C by incorporation of 5 mol%, 10 mol%, and 20 mol% 2-methyl succinic units, respectively. ͬʱ£¬ÒýÈë5 mol%, 10 mol%,ºÍ20 mol%·Ö±ðʹÈÛµãϽµÁË5 0C, 10 0C and 21 0C¡£ 5. The satisfactory tensile strength of block copolymers may be attributed to the formation of allophanate crosslinks by the introduction of excess TDI. The presence of allophanate crosslinks can be proved by the highest molecular weight of 20 series copolymers, followed by 40 ( in Table 2). This is because polyols with lower molecular weight needs more TDI to chain-extension. As the molar ratio of TDI to polyols was fixed at 2.1/1, relative more excess TDI was applied for 20 based copolymers which would cause more allophanate crosslinks. As a result, highest molecular weight in Table 2 is observed for the 20 based copolymers. The resulted additional chemical tie points by allophanate crosslinks lead to a more uniform stress distribution throughout the sample, thus preventing plastic flow of the crystals and leading to stress-transmission through soft segment. The more uniform stress distribution in combination with increasing chemical crosslinks led to the increasing tensile strength. Ƕ¶Î¹²¾ÛÎïÁîÈËÂúÒâµÄÀÉìÇ¿¶È¹éÓÚ¹ýÁ¿µÄTDIËùÐγɵÄëå»ù¼×Ëáõ¥½»Áª¼ü¡£ëå»ù¼×Ëáõ¥½»Áª¼ü¿ÉÒÔ´Ó20ϵÁеĹ²¾ÛÎïµÄ·Ö×ÓÁ¿×î¸ß£¬Æä´ÎÊÇ40ϵÁеķÖ×ÓÁ¿¶øµÃµ½Ö¤Êµ¡£ÕâÊÇÒòΪµÍ·Ö×ÓÁ¿µÄ¶þ´¼ÐèÒª¸ü¶àµÄTDIÀ´À©Á´¡£ÓÉÓÚTDIÓë¶þ´¼µÄĦ¶û±È¹Ì¶¨Îª2.1/1, ¶Ô20ϵÁÐÀ´½²£¬¹ýÁ¿µÄTDI¾Í»á¶àЩ£¬Õ⽫µ¼ÖÂÐγɸü¶àµÄëå»ù¼×Ëáõ¥½»Áª¼ü¡£Òò´Ë£¬Èç±í2Ëùʾ£¬20ϵÁеķÖ×ÓÁ¿×î¸ß¡£ ´Ë¶ÎµÄ×îºó2¾ä»°Ã»ÓдíÎó£¬Ö»Ðè¸ÄдÏ£¬ÏëÔÚ±£ÁôÔÒâµÄǰÌáÏ»»ÖÖ±í´ï·½Ê½¡£ [ Last edited by mengbaiyang on 2008-10-5 at 11:09 ] |
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djxustc
Ìú¸Ëľ³æ (ÕýʽдÊÖ)
- Ó¦Öú: 14 (СѧÉú)
- ½ð±Ò: 6109.7
- É¢½ð: 78
- ºì»¨: 291
- Ìû×Ó: 504
- ÔÚÏß: 2381.8Сʱ
- ³æºÅ: 615187
- ×¢²á: 2008-09-29
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1. On the other hand, the materials based on aliphatic diisocyanates are famous for their unchanged whiteness and they will not change to yellow when irradiated with ultraviolet, visible light or heated. That color changing is often the defect of materials based on aromatic diisocyanates group. ÁíÒ»·½Ã棬»ùÓÚÖ¬·¾×å¶þÒìÇèËáõ¥µÄ²ÄÁÏÒÔÆä¶ÀÓеİ×É«¶øÖø³Æ£¬ÇÒÆäÔÚ×ÏÍâ¹â¡¢¿É¼û¹âºÍÈÈÌõ¼þ϶¼²»»á±ä»Æ¡£¶øÕâͨ³£ÊÇ·¼Ïã×å¶þÒìÇèËáõ¥»ùµÄȱµã¡£ 2.In order to achieving optimal mechanical property, the molar ratio of TDI and total polyesters was set to be 2.1/1 to form some allophanate crosslinks point as shown in table X. ΪÁË»ñµÃ×îÓŵÄÁ¦Ñ§ÐÔÄÜ£¬TDIºÍ×ܵľÛõ¥µÄĦ¶û±È¶¨Î»2.1/1ÒÔÐγÉһЩëå»ù¼×Ëáõ¥µÄ½»Áªµã£¬ÈçͼX£¨Êý×Ö£©Ëùʾ 3. However, the Tms decrease by 9 0C and 18 0C when molar ratios of unit of ¦Å-caprolactone and butylene succinate are 0.08 and 0.18, respectively. È»¶ø£¬ºÜÒź¶µÄÊÇ(ɾ³ý)£¬µ±ÒÑÄÚõ¥ºÍ¶¡¶þËá¶¡¶þõ¥µÄĦ¶û±ÈΪ0.08 ºÍ 0.18ʱ£¬¹²¾ÛÎïµÄÈÛµãÏ·ֱð½µÁË9 0C ºÍ 18 0C¡£ 4. Meanwhile, Tms reduce by 5 0C, 10 0C and 21 0C by incorporation of 5 mol%, 10 mol%, and 20 mol% 2-methyl succinic units, respectively. ͬʱ£¬ÒýÈë5 mol%, 10 mol%,ºÍ20 mol%·Ö±ðʹÈÛµãϽµÁË5 0C, 10 0C and 21 0C¡£ 5. The satisfactory tensile strength of block copolymers may be attributed to the formation of allophanate crosslinking bonds by the introduction of excess TDI. The presence of allophanate crosslinking bonds can be proved by the highest molecular weight of 20 series copolymers, followed by 40 in Table 2. the reason is that diols with lower molecular weight need more TDI to extense the chain. As the molar ratio of TDI to diols was fixed at 2.1/1, relative more excess TDI was applied for 20-series copolymers which would cause more allophanate crosslinks. As a result, highest molecular weight in Table 2 is observed for the 20 based copolymers. The resulted additional chemical tie points by allophanate crosslinks lead to a more uniform stress distribution throughout the sample, thus preventing plastic flow of the crystals and leading to stress-transmission through soft segment. The more uniform stress distribution in combination with increasing chemical crosslinks led to the increasing tensile strength. Ƕ¶Î¹²¾ÛÎïÁîÈËÂúÒâµÄÀÉìÇ¿¶È¹éÓÚ¹ýÁ¿µÄTDIËùÐγɵÄëå»ù¼×Ëáõ¥½»Áª¼ü¡£ëå»ù¼×Ëáõ¥½»Áª¼ü¿ÉÒÔ´Ó20ϵÁеĹ²¾ÛÎïµÄ·Ö×ÓÁ¿×î¸ß£¬Æä´ÎÊÇ40ϵÁеķÖ×ÓÁ¿¶øµÃµ½Ö¤Êµ¡£ÕâÊÇÒòΪµÍ·Ö×ÓÁ¿µÄ¶þ´¼£¨diol not polyols£©ÐèÒª¸ü¶àµÄTDIÀ´À©Á´¡£ÓÉÓÚTDIÓë¶þ´¼µÄĦ¶û±È¹Ì¶¨Îª2.1/1, ¶Ô20ϵÁÐÀ´½²£¬¹ýÁ¿µÄTDI¾Í»á¶àЩ(ººÓï±í´ï»ìÂÒ)£¬Õ⽫µ¼ÖÂÐγɸü¶àµÄëå»ù¼×Ëáõ¥½»Áª¼ü¡£Òò´Ë£¬Èç±í2Ëùʾ£¬20ϵÁеķÖ×ÓÁ¿×î¸ß¡£ |
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