干茧触蒸前处理对茧层表面与液滴接触角的影响

Effect of Direct Steaming Pretreatment on the Contact Angle Between Liquid Droplet and Cocoon Layer

触蒸前处理是用饱和蒸汽对煮茧前的干茧进行湿热处理的一种处理工艺。在外界环境条件一致的情况下,设置65、85、105℃的触蒸温度,对干茧分别进行20、40、60 min的触蒸前处理,再把经触蒸后的蚕茧和未触蒸的干茧同时进行真空渗透处理,测试经不同触蒸工艺条件处理后茧层表面与液滴的瞬间接触角值,观察茧层表面与液滴的瞬间接触形态,以及比较触蒸或未触蒸渗透处理后的茧层接触角变化,探究接触角与触蒸蚕茧润湿效果的关联性。结果表明:在对干茧的触蒸前处理工艺中,以105℃作为触蒸温度并控制触蒸时间为60 min时,蚕茧茧层表面与液滴的瞬间接触角值最小,且茧层表面与液滴的接触面最大;触蒸前处理蚕茧经真空渗透处理后,茧层表面与液滴的瞬间接触角值明显比未触蒸直接渗透处理后的茧层接触角值小。试验结果显示:在触蒸工艺中适当升高触蒸温度和延长触蒸时间,能改善茧层的润湿性和亲水性,且触蒸前处理工艺明显有利于真空渗透中蚕茧的润湿渗透;可通过测量处理后茧层表面与液滴接触角的方法,分析触蒸前处理对蚕茧的浸润渗透效果。

Direct steaming pretreatment is one of the pretreatment processes in cocoon cooking which uses saturated steam to do heat-moisture treatment to dry cocoons. While other environmental conditions were fixed,dry cocoons were treated by direct steaming pretreatment for 20,40 and 60 minutes at 65,85 and 105 ℃ steaming temperature respectively. Then,the steamed cocoons and dry cocoons without steaming were treated by vacuuming permeation at the same time. Afterwards,transient contact morphology of liquid droplet on cocoon surface was observed through measuring transient contact angles between liquid droplets and cocoon surfaces that have undergone various direct steaming pretreatments. Contact angle variation of cocoon layers was also compared between the steamed cocoons and un-steamed cocoons to explore the relationship of contact angle with wettability of steamed cocoons. The results showed that,after cocoons were treated at 105 ℃ steaming temperature for 60 minutes in the pretreatment process,the contact angle of liquid droplet with cocoon layer surface was the lowest and the contact area between liquid droplet and cocoon layer was the largest. The contact angle of cocoons treated by direct steaming pretreatment followed by vacuuming permeation was lower obviously than those treated only by vacuuming permeation. The above results demonstrate that increasing steaming temperature and time properly in the pretreatment process could obviously improve the wettability and hydrophilicity of cocoon layers. Direct steaming pretreatment is obviously favorable to permeability of wa-ter into cocoons in vacuum permeation. The permeation effect of direct steaming pretreatment can be analyzed through measuring the contact angles of cocoon layer surface after the treatment.