Ozone oxidation of the surface of artificial ligament material polyethylene terephthalate fiber

doi:10.3969/j.issn.2095-4344.1362

Abstract

Abstract:

BACKGROUND: Artificial ligament material polyethylene terephthalate fiber has good physical-chemical- mechanical properties, but its surface affinity is poor, and it does not have good cell compatibility. Therefore, it is necessary to modify the surface of the material.

OBJECTIVE: This study was designed to form active sites on the surface of polyethylene terephthalate fiber by ozone oxidation, and to improve its cell compatibility.

METHODS: The polyethylene terephthalate fiber was braided into a grey fabric by warp knitting and cut into small cuts at suitable sizes. The small cuts were placed in distilled water for 30-minute ozone oxidation at room temperature with oxygen flow rate of 1 L/min and ozone concentration in aqueous solution of 10 mg/L. The surface morphology, mechanical properties, and toluidine blue adsorption of polyethylene terephthalate fiber were observed before and after ozone oxidation.

RESULTS AND CONCLUSION: Scanning electron microscopy showed that the surface roughness of polyethylene terephthalate fiber increased slightly after ozone oxidation, and there was no obvious evidence of cracking degradation. After ozone oxidation, peroxy groups were successfully introduced onto the surface of polyethylene terephthalate fiber with a concentration of 10^-⁵ mol/g. After ozone oxidation, the surface of the polyethylene terephthalate fiber did not show obvious degradation, and the mechanical property remained good. It can meet the requirement of the tensile properties of the artificial ligament material. Before ozone oxidation, the polyethylene terephthalate fiber lacked hydrophilic groups in the main chain, and hardly adsorbed toluidine blue. After ozone oxidation, toluidine blue absorption increased with the increase of hydrophilic groups on the surface of the fiber. All results suggest that ozone oxidation treatment not only ensures the mechanical property of polyethylene terephthalate fiber, but also introduces a sufficient amount of peroxy groups on its surface.

Key words: artificial ligament, polyethylene terephthalate, ozone, surface oxidation, peroxide density, deep cleanning, tensile properties, characterization

CLC Number:

Shi Fengtian, Zhang Mei, Sun Shichao, Chen Shuxiang, Li Dengyun, Sun Xuelian. Ozone oxidation of the surface of artificial ligament material polyethylene terephthalate fiber[J]. Chinese Journal of Tissue Engineering Research, 2019, 23(26): 4212-4216.

Figures/Tables 5

2.3 过氧基团含量检测结果臭氧处理使得聚合物表面产生活性基团，基团数量与材料、臭氧浓度、反应温度、臭氧氧化时间等有关。由于臭氧的强渗透性，氧化不仅可发生在聚合物表面，还可发生在材料内部[23]。臭氧氧化的深度过大，势必会降低纤维本体的抗拉强度[24]，因此控制臭氧化的程度，成为决定人工韧带性能的关键步骤。从生产成本、臭氧氧化速度、臭氧氧化均匀度等角度考虑，采用室温、水溶液中进行臭氧氧化反应，由于臭氧浓度是发生器固定参数，所以在此只改变臭氧处理的时间，来考察过氧基团的生成效果。由图4可见，聚对苯二甲酸乙二醇酯纤维表面上活性过氧基团的含量随着臭氧处理时间的增加而增加，初始线性关系良好，超过30 min后过氧基团的生成速率逐渐放缓。其可能的原因是：臭氧使聚对苯二甲酸乙二醇酯分子链受到高浓度强氧化剂的冲击，分子链上随之产生过氧基团，随着时间的增加，分子链与臭氧的接触愈加充分，因此其含量相应快速增加。但随着时间的进一步增加及聚对苯二甲酸乙二醇酯纤维表面分子链臭氧化反应的结束，臭氧渗入到纤维本体内部也愈加困难，同时纤维表面生成的过氧基团开始不可避免的发生分解[25]，因此过氧基团含量的增速愈趋于平缓。从图可知，臭氧氧化时间30 min较为适宜，既可保证必要的过氧基团数量又不致臭氧化深度过大而影响聚对苯二甲酸乙二醇酯纤维本体的力学性能，此时纤维表面的过氧化物浓度在10-5 mol/g数量级。臭氧氧化在聚对苯二甲酸乙二醇酯纤维表面产生过氧基团，这些过氧基团在光、热的作用下可分解为自由基，自由基继而可引发乙烯基单体聚合，从而在聚对苯二甲酸乙二醇酯纤维表面形成接枝聚合物[26]。可以说过氧基团的成功引入，为进一步改善纤维表面性能打下了良好基础。"

2.4 单丝力学性能检测结果臭氧氧化过程中，除在聚对苯二甲酸乙二醇酯纤维表面引入羟基、羧基等基团外，还不可避免地引起聚合物降解，导致纤维力学性能下降[12]。而对人工韧带而言，其力学性能尤其是拉伸性能，必须与正常成年人体韧带相似是韧带重建的首要标准[27]。因此，必须明确臭氧化前后纤维的力学性能的变化。从图5可看出臭氧氧化后，聚对苯二甲酸乙二醇酯纤维的断裂强力和断裂伸长率均出现下降。根据行业标准要求，人工韧带的断裂强度通常要在3 cN/dtex以上[28]，因此在满足纤维表面有充足的活性基团的情况下，有必要保证纤维力学性能有较多的富余。故选择臭氧化的时间30 min，此时聚对苯二甲酸乙二醇酯纤维的断裂强度>7 cN/dtex，力学性能损失不超过10%，完全满足人工韧带产品对聚对苯二甲酸乙二醇酯纤维拉伸性能的要求。 2.5 甲苯胺蓝吸附结果甲苯胺蓝为一种碱性染料，其分子可与-COOH、-OH等基团发生比例吸附关系，因此甲苯胺蓝既可使织物的处理效果直观化，更可用作表面亲水基团的定量分析[10，29]。由于前述已完成过氧基团的碘量法测试，因此在此次实验中，甲苯胺蓝染色仅用于臭氧氧化前后表面处理效果的观察。由图6可见，臭氧氧化前后的聚对苯二甲酸乙二醇酯织物颜色有明显差别，未经臭氧处理聚对苯二甲酸乙二醇酯主链上由于缺乏亲水性基团，与甲苯胺蓝分子的结合较少，也很不牢固，很容易被NaOH溶液冲掉，因此聚对苯二甲酸乙二醇酯织物依然为白色，表现出几乎不吸附甲苯胺蓝。与之相对，经臭氧处理后，聚对苯二甲酸乙二醇酯主链上的亲水基团大为增加，并与甲苯胺蓝分子形成牢固结合，因此织物表现出明显的蓝色。 "

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