Surface coating of bamboo fibres and its effects on the mechanical properties of casting polyurethane elastomer
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摘要: 通过一种异氰酸酯基团(—NCO)质量分数为14.5wt%的高活性聚氨酯(PU)包覆剂对竹纤维(BF)进行表面包覆获得包覆型竹纤维(PUBF),采用原位聚合法制备了包覆型竹纤维增强浇注型聚氨酯(PUBF/PU)弹性体复合材料。采用FTIR、SEM、XRD及接触角测试仪对PUBF及BF进行了表征。结果表明,BF表面成功包覆了具有活性氨基(—NH2)封端的PU薄层,改善了BF与浇注型聚氨酯PU间的界面相容性及界面结合。复合材料中的PUBF质量分数为3wt%时,80℃下预聚体黏度仅为2.2 Pa·s,与纯预聚体黏度接近;对应PUBF/PU复合材料的拉伸和撕裂强度分别为38.0 MPa和82.9 kN/m,比纯浇注型PU分别提高51.6%和25.6%。高活性PU包覆剂预先包覆BF适合制备PUBF/PU复合材料。Abstract: The coated bamboo fibres (PUBF) were obtained by using high-reactivity polyurethane (PU) coating agent to coat bamboo fibres (BF), and the mass fraction of isocyanate group (—NCO) in PU coating agent was 14.5wt%. The PUBF/PU casting elastomer composites were prepared by in-stiu polymerization. The BF and PUBF were characterized by FTIR, SEM, XRD and contact angle testing. The results show that the surface of the BF is successfully coated by a thin layer of PU terminated with reactive amino groups (—NH2), which improves the interface compatibility and interfacial bonding between the BF and the casting PU. When the mass fraction of PUBF in the composite is 3wt%, the viscosity of the prepolymer at 80℃ is only 2.2 Pa·s, which is close to the viscosity of the pure PU. The tensile and tear strengths of the corresponding PUBF/PU composite are 38.0 MPa and 82.9 kN/m, respectively, improved by 51.6% and 25.6% compared with the pure casting PU. The BF pre-coated by high-reactivity PU coating agent is suitable for preparing the PUBF/PU composite.
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Key words:
- surface treatments /
- bamboo fibres /
- polyurethane /
- composites /
- viscosity /
- mechanical properties
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表 1 BF和PUBF的接触角及表面能参数
Table 1. Contact angles and surface free energy parameters of BF and PUBF
Sample Contact angle θ ± SD#/(°) Surface free energy/(mJ·m−2) Water Ethylene glycol $\gamma _{\rm{s}}^{\rm{p}}$ $\gamma _{\rm{s}}^{\rm{d}}$ ${\gamma _{\rm{s}}} = \gamma _{\rm{s}}^{\rm{p}} + \gamma _{\rm{s}}^{\rm{d}}$ BF 18.1±1.2 24.9±1.1 85.4 1.1 86.5 PUBF 69.5±2.1 52.4±1.4 22.0 11.6 33.6 Notes: SD#—Standard deviation; $\gamma _{\rm{s}}^{\rm{p}}$, $\gamma _{\rm{s}}^{\rm{d}}$ and ${\gamma _{\rm{s}}}$ —Polar, non-polar part and total of surface free energy, respectively. 表 2 PUBF/PU和BF/PU复合材料力学性能随纤维质量分数的变化
Table 2. Variations in mechanical properties of PUBF/PU and BF/PU composites with the mass fractions of PUBF and BF
Sample Tensile strength/
MPaTear strength/
(kN·m−1)Elongation at
break/%Hardness
(HA)Rebound
rate/%PU 25.1(0.8) 66.0(1.3) 528(10) 85(1) 45(1) BF/PU-0.5 25.5(0.6) 76.7(1.9) 505(13) 86(1) 43(1) BF/PU-1 29.7(1.4) 79.1(2.9) 500(21) 87(1) 42(1) BF/PU-3 31.2(1.5) 81.2(2.9) 537(14) 90(2) 39(2) BF/PU-5 24.8(1.0) 82.6(2.6) 549(17) 91(1) 37(1) PUBF/PU-0.5 30.6(1.2) 77.1(2.1) 628(20) 86(1) 45(1) PUBF/PU-1 33.0(0.9) 80.6(1.6) 634(17) 86(1) 44(2) PUBF/PU-1.5 35.1(0.6) 82.2(2.1) 605(23) 87(1) 42(1) PUBF/PU-3 38.0(1.5) 82.9(1.4) 583(17) 88(2) 40(2) PUBF/PU-5 26.1(1.1) 88.2(2.0) 549(17) 86(1) 39(1) Notes: BF/PU-x and PUBF/PU-x stand for the composites with the fiber mass fractions of x%; Data in parentheses refer to the standard deviations. -
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