新型气硬动物胶型芯粘结剂的改性工艺优化

针对动物胶常温凝聚、热硬消耗能源且效率低的问题,以动物骨胶为主要原料,经过碱解、改性处理后得到了一种新型型芯粘结剂,并采用吹CO2气体方式硬化.选择并优化了动物胶碱解工艺,引入活性基团对动物胶进行接枝共聚以及酯化改性,进一步提高了粘结强度,同时对新型动物胶粘结剂的吹气硬化和改性机理进行了理论分析.结果表明:改性动物胶铸造粘结剂最佳配比为m(丙三醇)∶m(糊精)∶m(乙醇)∶m(动物胶)=9∶10∶9∶100,改性温度为75℃,改性时间为90 min.吹CO2气体硬化的新型改性动物胶粘结剂,初强度大于0.8 MPa,终强度达到6.0 MPa,能够满足快速制芯生产要求.

新型气硬动物胶型芯粘结剂的制备工艺优化

以动物骨胶为主要原料,经过碱解、改性处理后得到了一种新型CO2硬化型芯粘结剂。针对传统动物胶常温凝聚、热硬消耗能源且效率低的不足,首先选择并优化了动物胶碱解工艺,并引入活性基团对动物胶进行接枝共聚以及酯化改性,进一步提高粘结强度。最后对新型动物胶粘结剂的吹气硬化和改性机理进行了理论分析。结果表明:改性动物胶铸造粘结剂最佳配比为m(丙三醇)∶m(糊精)∶m(乙醇∶)m(动物胶)=9∶10∶9∶100,改性温度75℃、改性时间90 min。吹CO2气体硬化的新型改性动物胶粘结剂,初强度大于0.65MPa、24h抗压强度达到4.2MPa,能够满足快速制芯生产要求。

新型CO_2硬化动物胶粘结剂改性工艺的优化

针对动物胶粘结剂砂型强度低、易于溃散的问题,通过碱解、改性处理得到了一种新型动物胶粘结剂,并采用吹CO_2气体的方式将其硬化.选择并优化动物胶粘结剂的碱解工艺,引入活性基团对动物胶粘结剂进行酯化反应和接枝共聚改性,从而进一步提高其粘结强度,并对新型动物胶粘结剂的吹气硬化和改性机理进行了理论分析.结果表明,动物胶粘结剂的最佳质量配比为丙烯酸∶过硫酸铵∶葡萄糖∶动物胶=30∶3∶15∶100.当改性温度为75℃、改性时间为90 min时,型砂的抗压强度可以达到2.75 MPa,满足快速制芯生产的要求.

醇改性动物胶粘结剂及其改性机理

为改善动物胶常温下易凝胶且型砂强度低的问题,通过醇对动物胶粘结剂的酯化交联对其进行改性处理,使其成为铸造用粘结剂。试验结果表明,醇类改性剂改善了动物胶的凝胶状态且显著提高了其型砂抗压强度,其中无水乙醇和丙三醇改性效果较佳,丙三醇改性动物胶粘结剂型砂的抗压初强度达到了0.92 MPa,终强度达到了3.77 MPa。依据强度指标,确定了改性工艺中最佳改性温度为75℃,最佳改性时间为90 min。并通过红外光谱仪和型砂试样的断口断裂方式进一步分析了动物胶粘结剂因醇的改性而改善其性能的粘结机理,其改性机理主要是由于醇类中的羟基-OH与动物胶侧链的羧基-COOH发生了酯化交联反应,改善了粘结力。

改性水溶性高分子粘结剂的制备及性能的研究

动物胶粘结剂是水溶性天然高分子粘结材料,具有无毒无害、可降解等特性,但其也具有在常温下易凝聚、流动性差、型砂强度低等问题,针对这一问题需要对其进行改性处理。在碱解条件下,采用丙三醇、乙醇和糊精对动物胶进行改性处理。试验表明:在碱解过程中,水胶比为8∶5,Na OH加入量为动物胶质量的5%,在改性过程中,选择的改性剂最佳配比(质量比)为:动物胶∶丙三醇∶乙醇∶糊精=100∶10∶10∶10,改性温度为75℃、改性时间为90 min。测得其表面张力值为26.451m N/m、抗压强度达到3.30 MPa,最后通过红外光谱对改性机理进行理论分析,分析认为改性剂丙三醇、乙醇和糊精可与动物胶发生反应。结果证明丙三醇、乙醇和糊精复合改性剂可以降低动物胶表面张力,提高表面润湿性,最终使得砂型强度增大。

GFAP and Fos immunoreactivity in lumbo-sacral spinal cord and medulla oblongata after chronic colonic inflammation in rats

AIM： To investigate the response of astrocytes and neurons in rat lumbo±sacral spinal cord and medulla oblongata induced by chronic colonic inflammation, and the relationship between them. METHODS： Thirty-three male Sprague-Dawley rats were randomly divided into two groups： experimental group （n = 17）, colonic inflammation was induced by intra-luminal administration of trinitrobenzenesulfonic acid （TNBS）; control group （n = 16）, saline was administered intra-luminally. After 3, 7, 14, and 28 d of administration, the lumbo-sacral spinal cord and medulla oblongata were removed and processed for anti-glial fibrillary acidic protein （GFAP）, Fos and GFAP/Fos immunohistochemistry. RESULTS： Activated astrocytes positive for GFAP were mainly distributed in the superficial laminae （laminae Ⅰ-Ⅱ） of dorsal horn, intermediolateral nucleus （laminae Ⅴ）, posterior commissural nucleus （laminae Ⅹ） and anterolateral nucleus （laminae Ⅸ）. Fos-IR （Fos-immunoreactive） neurons were mainly distributed in the deeper laminae of the spinal cord （laminae Ⅲ-Ⅳ, Ⅴ-Ⅵ）. In the medulla oblongata, both GFAP-IR astrocytes and Fos-IR neurons were mainly distributed in the medullary visceral zone （MVZ）. The density of GFAP in the spinal cord of experimental rats was significantly higher after 3, 7, and 14 d of TNBS administration compared with the controls （50.44±16.8, 29.24±6.5, 24.14±5.6, P〈0.05）. The density of GFAP in MVZ was significantly higher after 3 d of TNBS administration （34.34±2.5, P〈0.05）. After 28 d of TNBS administration, the density of GFAP in the spinal cord and MVZ decreased and became comparable to that of the controls （18.04±4.9, 14.64±6.4, P〉0.05）. CONCLUSION： Astrocytes in spinal cord and medulla oblongata can be activated by colonic inflammation. The activated astrocytes are closely related to Fos-IR neurons. With the recovery of colonic inflammation, the activity ofastrocytes in the spinal cord and medulla oblongata is reduced.