Design Improvement for Solving Black Spots Defect on the Rear-view Mirror in an Eco–car

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คุณาวุฒิ วิบูลย์พันธุ์
ณัฐพล ลิ้มจีระจรัส


Since launched to the domestic market in 2010, Eco-cars have been phenomenon and have become popular among car users in Thailand due to their inexpensive cost and low fuel consumption. However, a suspicion corresponded to the Eco-car’s low cost, which is always questioned by the customers, is the quality of their components. This research focuses on the investigation and solution of black spots defect on the rear-view mirror in a model of Eco-car, which reveals at about 2 months after being sold. The results from initial inspection on the physical structure of the rear-view mirror and the appearance of the black spots defect, and Energy-dispersive X-ray spectroscopy (EDX) technique confirmed that the root cause of the defect is the use of Ethylene propylene diene monomer (EPDM) foam as the support of the mirror plate. Sulfur, a composition in EPDM foam, reacted with silver coated on the back of the mirror plate and formed silver sulfide (Ag2S), a black-colored compound. In order to solve the problem, a new design of the rear-view mirror was proposed in which EPDM foams were replaced by plastic ribs as the mirror plate’s support. The success in the improvement has been proved that there is no claim of the modified rear-view mirrors in 4 months after the implementation of the new design.


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The Thailand Board of Investment. BOI drives a eco-car forward. THAILAND INVESTMENT REVIEW 2007;17:3.

Sarang Gopalakrishnan. Vulcanization and the Properties of Rubber. University of Illinois paper 2007.

ไพฑูรย์ หมายมั่นสมสุข. การวิเคราะห์ซัลไฟด์ในน้ำ. สำนักวิจัยและพัฒนาสิ่งแวดล้อมโรงงาน :11-5.


M. van Duin. Chemistry of EPDM Cross-Link. Elastomers and Plastics 2009:151-2.