| 摘要 |
<p>Polymeric compsn. used to form films for agricultural use, esp. for covering crops or plants, comprises >=80 wt.% polyolefin and 1-15 wt.% of a basic metallic sulphate additive of formula: (SO4)4M6'".M2'12(OH) (where M' is a monovalent metal, M'" is trivalent metal). Pref. the polyolefin is polyethylene or ethylene copolymer, esp. EVA copolymer present in an amt. of 90-97 wt.%. The films have low thermal transmittance props. in the spectrum ranging between 7-14 mu and excellent light diffusion props. with reduction in heat losses from greenhouses, are opaque to UV and are highly transparent to visible light and short wave IR radiation to provide the greenhouse effect. The additive has no adverse effect on the degradation of the polymer, esp. on exposing to constant weathering and have little abrasive effect on appts. used to make the films.</p> |
