微粒防護衣車縫邊氣膠穿透特性

Abstract

防護衣在製作上，為了增加穿著時的美觀與舒適，因此需加以剪裁與縫合，然而，不當的車縫邊卻也提供微粒穿透的途徑，因而降低微粒防護衣的效能。由於微粒穿透車縫邊的能力是其粒徑的函數，因此，不同等級與不同使用目的的防護衣所搭配的車縫方式應有所不同。目前防護衣車縫邊測試方法主要是針對整體洩漏率 (Total Inward Leakage, TIL)來做評估，但從微粒防護衣開發改良的觀點上，衣材的接合處，如拉鍊、車縫邊都是影響防護衣防護效果的重要因素，因此本研究除了探討微粒穿透車縫邊的特性之外，也比較不同量測方法在測定結果上的差異。 實驗中利用定量輸出霧化器與超音波霧化噴嘴分別產生次微米級與微米級多粒徑分佈測試微粒。並分別搭配SMPS與APS量測微粒的粒徑與數目濃度，微粒產生後經過氣膠電性中和器(Am-241)以中和微粒帶電。測試方法依序為：(1)主動抽氣過濾法：模擬動態活動時防護衣的車縫邊微粒穿透特性；(2) 內循環採樣法：評估防護衣的車縫邊在靜態時的微粒防護性能。測試的防護衣材料選用市面上常見的實驗衣(Lab coat)、醫療用隔離衣 (Hospital gown)、泰維克 (Tyvek barrier-man)微粒防護衣三種。車縫針型號依不同直徑 (Diameter, D)分為#9 (D=0.61 mm)、#11 (D=0.74 mm)、#14 (D=0.96 mm)和#16 (D=1.02 mm)四種，以評估不同車縫針大小對車縫邊穿透率的影響。車縫線粗細的影響分別使用40/2 (細)以及30/3 (粗)用以評估是否其影響洩漏孔徑的大小。車縫的方式為三線考克 (Serged seam)，另外也測試壓縫 (Serged seam with twin top stitch)對微粒穿透的影響。 主動式採樣法實驗結果，三種防護衣材其壓降變化順序為Tyvek >實驗衣 >隔離衣，實驗選定表面風速1cm/s的條件下進行量測，以0.1 μm的微粒來看，穿透率依序為6.1%、57.4%、66.2%。各防護衣材經 #9號針三線考克車縫 (Serged seam)後，以0.1 μm的微粒來看， Tyvek微粒穿透率從6.6%增加至62.3%，經壓縫後下降至22.9%；另外經#16號針考克車縫後Tyvek微粒穿透率從6.6%增加至93.3%，經壓縫後下降至86.1%。實驗衣在各參數改變下穿透率仍在57.4% ± 5% 以內，而醫療隔離衣在各參數變化下穿透率皆為66.2%± 5%。因此Tyvek 經壓縫後且選用#9號針能達到提升防護效能的結果。防護等級較低的實驗衣及醫療隔離衣分別為斜紋織布與平織布屬編織性材質，車縫針通過後因其布料的彈性而有填充的效果，另外透氣性高，車縫方式、車針大小改變造成的洩漏遠低於布料的整體洩漏率，所以穿透率不易受到影響 。模擬動態的主動式系統所量測出來的穿透率高於模擬靜態的內循環系統。而Tyvek在車縫邊處的洩漏不管是主動式或內循環系統中皆明顯高於沒車縫邊的防護衣材，建議加強與改善車縫邊的縫合方式，以利其對微粒防護效果更臻完美。

Personal protective clothing is designed to protect workers against hazardous substances that might come into contact with the skin. Several test methods have been developed to measure barrier properties of particulate protective clothing (PPC) against particulate assaults, normally in terms of total inward leakage. However, it has been shown that PPC provided less protection when the junctions became part of the ensemble. Those officially accepted test methods might not be appropriate to identify and characterize the leakage through junctions. Therefore, this study aimed to investigate the characteristics of aerosol penetration through junctions, mainly seams. The main objective of this study was to develop two test methods for evaluating the aerosol penetration through particulate protective clothing materials: (1) Active sampling method: monitoring aerosol penetration through PPC under extremely low filtration velocity, and (2) Closed-return sampling train method: using a closed-return to measure the PPC performance without active sampling. The active sampling method is useful to illustrate the aerosol penetration through protective clothing, when the wearers are in motion, vacuum might be created inside the clothing. The closed return sampling train method simulated the relative velocity due to indoor air flow and/or wear’s moving. In order to cover a broad size range, a constant output atomizer and an ultrasonic atomizing nozzle were used to generate polydisperse sub-micrometer-sized and micrometer-sized particles, respectively. The aerosol output was neutralized by using a 25 mCi radioactive source, Am-241, and then introduced into the mixing (test) chamber. Two different particle size spectrometers were used to measure the aerosol concentrations and size distributions upstream and downstream of the filters: a scanning mobility particle sizer (SMPS) for particles smaller than 0.7 mm, and an aerodynamic particle sizer (APS) for particles larger than 0.7 mm.

Both active sampling method and closed return sampling train method showed that the aerosol penetration through clothing with seam was much higher than that of clothing without seam. This phenomenon was particularly significant when the air resistance of clothing material was high. Sewing method also influenced PPC performance. Serge seam with twin top stitches was superior to simple serge seam. Pressure drop across clothing with seam decreased with increasing needle size. Aerosol penetration through clothing with seam was depended on needle size. A particular needle with coarser yarn helped reduce aerosol penetration, especially for high air resistance material, e.g. Tyvek.