本文探討了台灣石化業的主要部門塑膠原料業的成長過程以及成長的房、因，也探究了上游石化基本原料業與下游塑膠製品業對其成長的影響。這產業中除了PVC發展較早外，其他則都是在公營企業關始經營上游的經油裂解廠之同時隨著設廠生產，是典型的向前連鎖效應，而推動者則為國家。這六個產業從開始到1986年為止，都大量史維持相當的成長率，之後則各業有顯著不同的表現。在早期下游的需求對於各產業而言，都是主妥的成長動力，同時下游帶動作用越大的產業，其成長率就越快，顯現了一種動態的雪球效果。同時，技術變革、產業的成長潛能與市場競爭程度之間也呈現動態的相關性，並影響著產業的成長。政策因素對這產業有很深的影響，除了以公營企業經營上游並在啟始階段領導推動之外，政府一直採用各種關稅與非關稅的保護措施來扶植這產棠，直到1986年開始貿易自由化為止。同時這也是台灣發展的一個典型，出口導向政策常配合著中上游的進口替代，顯示這兩種政策並非是相互排斥的選擇。

This paper explores the history and causes of growth of Taiwan's plasticmaterial industry， which lies vertically between the upstream basic petrochemicals and the downstream plastic product sectors_ The study focuses on the six common plastics， PVC， LDPE， HDPE， PP， PS， and ABS， which comprise over 80% of the sector_ Almost all of them were established along with the state-run upstream naphtha-cracking plants_ That is， forward linkage effects were effective_ All grew steadily until liberalization in 1986_ For those sectors， whose inputs cannot be easily transported， their growth began to be restricted since the late 1980s when local protest postponed the construction of the fifth and sixth cracker. For other sectors their growth has been unhampered_ PS and ABS sectors grew rapidly by expanding their exports， especially to the mainland， in the later period_ The downstream's demand has been the engine of growth for all six sectors_ The backward linkage effects， however， are stronger in those sectors that did not face supply restriction and those that grew faster_ The greater the downstream's growth rate， the better its prospects， the greater the linkage effects and the faster the midstream's growth_ Market structure also matters_ Moreover， industrial policy has been instrumental in bringing about industrial upgrading_ That is， ladder-climbing does not come automatically for an NIG.