Plastic Material: PP Resin

Basic Information

Polypropylene(PP): The chemical formula of Polyoxymethylene is (C3H6)nLow density (approx. 0.89~0.91g/cm3), original color is white and translucent, lower cost than other plastic materials, recycleable, resin identification code: 5. 

PP and PE has many features in common, but PP is much easier to degraded by UV rays and heat, 與PE的材質特性有許多相似處,但PP比較容易在紫外線和熱能作用下被氧化降解,造成耐化學性降低。

PP can be classified into 3 kinds, PP-H, PP-R, and PP-B:

  • PP-H (Isotactic PP Homopolymeride): 僅由丙烯單體聚合而成,又可稱為「均聚聚丙烯」。其出現的年代較最早,並於日常生活中廣泛被使用。其分子鏈之中不存在乙烯單體,因此分子鏈的規整度很高,材料的結晶度高,但也因此造成材質較脆、容易斷裂,耐衝擊性能較差的特性PP-H has the highest crystallinity and therefore the highest hardness, tensile strength and stiffness. PP-R has a very good long-term creep strength at higher temperatures。
    Advantage: Good long-term creep strength at higher temperatures, better strength than the other two kinds.
    Disadvantage: 抗衝擊性能較差(較脆)、韌性差、尺寸穩定性差、易老化
    Application:extrusion molding, blow molding, injection molding. Products such as plastic bottle, packaging strap, brush, cord/rope/lanyard, plastic woven bag, toy, microwave meal box, document folder, electronic equipment, packaging film, etc.
    How to classify: 用火一燒,拉開的細絲是扁形的,因為延伸度不太好,所以拉得不長。
  • PP-R (PP Random Co-polymeride): 又可稱為「無規共聚聚丙烯」,是PP之中性能最好的一種。於丙烯單體中添加少量的乙烯(1-4%)單體,進行加熱、加壓、及催化劑作用下共聚製成。乙烯單體在丙烯的長鏈中隨機、無規律性地分布其中,因此降低了聚合物的結晶度和熔點、藉由增加韌性,使得耐衝擊性、抗氧老化性、長期耐熱性都獲得改善。由此可知,添加一定量的乙烯,對於長期熱穩定性、力學性能及機械加工性能都顯著的影響。尤其乙烯單體分布地越無規律,聚丙烯性能的改善更好。
    優點:綜合性能良好。由於乙烯的添加增加了韌性,因此兼顧強度高、剛性大的優點、耐熱性能好、尺寸穩定性佳、在低溫時韌性極佳(撓曲性好)、高透明性、光澤度好、外觀美觀。
    Application: 押出成型、吹出成形、薄膜級、射出成形。可用於生產管材、收縮膜、點滴瓶、高透明容器、透明家庭日常用品、一次性針筒、包裝紙薄膜等。
    How to classify: 燃燒後不會發黑,由於材質韌性較佳,因此能拉出很長的圓絲
  • PP-B (PP Block Co-polymeride): 乙烯含量較無規共聚聚丙烯高,一般為7~15%,但由於PP-B中兩個乙烯單體及三個單體連接在一起的機率非常高,因此乙烯單體僅存在嵌段中,PP-H的規整度並未被降低,因此無法藉由添加乙烯而改善PP-H的熔點、長期耐熱性、抗氧老化等性能。
    優點:於室溫及低溫下,抗衝擊性能較佳,具備一定程度的剛性,相較於PP-R,透明度低、光澤度也低。
    Application: extrusion molding, injection molding. Products such as baby stroller, sport equipment, luggage/suitcase, paint barrel, battery box, etc.
    How to classify: 燃燒後不會發黑,能拉出很長的圓絲
  • Common feature of above three kinds: non-hygroscopic (only adherent moisture on the surface, not absorbed), resistant to chemical, acidity, and alkalinity, poor resistance to oxidation under high temperature.

Properties

1. Tough yet flexible, resistant to fatigue

2. Heat resistance

3. Chemical, acidity, and alkalinity resistant

4. Nice electric insulativity

5. The surface is printable, which available for wide applications, such as LOGO printing or marking warning message/sign.

6. Low density, has the lightest weight among all kinds of resins, so we can use Buoyancy Test Method to classify it with other materials.

7. Smooth surface and glossy

8. Except PP, plastic is generlly not suitable to be used for producing microwave meal box because toxic substances release.

Limitation

1. Not resistant to UV rays, long-time exposure to UV rays may result in decrease of mechanical property, fading of color, cracking surface, or chalking

2. Ageing after contacted with copper

3. High shrinkage rate, approx. 1.8%-2.5%


Manufacture

  • Suitable molding method: extrusion molding, injection molding, blow molding, etc.
  • To improve poor resistance to UV rays: add DLTP (Dilauryl Thiodipropionate), Zinc Oxide
  • Drying before production is not necessary unless the humidity is too high, and it doesn't need too much time for drying (1~2 hours will be quite enough)

Application:  

auto parts, PP fiber for industrial usages, food container (available for microwave), dining ware, water bottle/cup, bucket, trach can, paint barrel, bottle of alcohol, syringe (injector), outer case of electronic equipment, rope/lanyard/cord/webbing, paper coin of UK, Australia, and Canada, etc.

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