『工藝的秘密. 材料特輯2』塑料的生產和對環境的影響(中英)

塑料工藝提示

NOTES ON MANUFACTURING

不同分子結構的塑料有著不同的生產方式。熱塑性塑料需要加熱至熔融狀態方可塑形，因此他們的原材料（母料）都是顆粒狀，而類似熱成型（壓塑或吸塑等）需要在板狀或者片狀的塑料上進行加工（板狀或片狀的塑料也是通過顆粒狀的塑料母料加工拉伸塑形），不過這一前期加工會增加成本。熱塑性塑料也同樣適用於並紡纖維赫塑料薄膜的製作。

Plastics with different molecular structures lend themselves to different methods of manufacture .  Thermoplastic are shaped by heating them until they are soft or liquid enough to be formed . So they are generally supplied in granulated form . Processes such as thermoforming require sheet materials , which are extruded from granules . This increases the material costs due to the extra price that is required. Thermopile are also  available as drawn fire and blown film.

塑料不同的結晶度同樣也會影響生產工藝。例如，非結晶塑料無法實現像結晶塑料製品那樣尖銳鋒利的細節，因此他們更適用於熱成型工藝，因為他們在一定溫度內會保持鬆軟和熔融狀態。然而，結晶塑料再加熱後流動性很強，所以更適用於製作薄壁和複雜的造型。由於以上二者的差異，不是所有的熱塑性塑料兜兼容，尤其當設計師利用多點注塑和塑料焊接來加強材料之間連接的時候，需要格外注意。但是材料之間的不可兼容性有的時候也很有用，例如可作為脫模劑和潤滑劑。

Different amounts of crystallinity also affect processing. For example , amorphous materials do not have a sharp melting point like crystalline materials . Therefore , they are more suited to processes like thermoforming because the material stays soft and formable over a wider temperature range . in contrast , crystalline materials will flow more easily in the mold due  to their sharp melting point and are therefore more suitable for thin wall sections and complex features. Due to their different properties , not all thermoplastics are compatible care must be taken when using processes such as multi-shot injection molding and plastics welding to ensure a strong inter material bond material incompatibility is sometimes used as an advantage , for example , in release agents and lubricants.

熱固性塑料在模具中成型。 某些甚至可以在室溫下加工成型，例如聚酯，環氧樹脂和聚亞安酯，原材料是液體狀態，並混合催化劑和加固劑，可以通過注射和澆灌的方式進入模具。或者，粉末狀和固體狀的熱固性塑料母料可以通過加熱來形成分子之間的交叉連接。

Thermosets are cured in the mold. Some are engineered to cure at room temperature such as polyester and epoxy，and polyurethane. These are supplied in liquid form and mixed with a catalyst or hardener, they can be poured or injected into a mold. Alternatively , powdered , liquid or solid thermosets are heated in a mold to trigger the formation of cross-links. 

有機塑料的加工方式橫跨了熱固和熱塑性塑料：他們可以通過熱塑性塑料加工方式成型，但是正果過程是不可重複的（不可逆的）。CA和PLA的成型方式和熱塑性塑料大同小異。例如，有些食物的包裝就是通過壓制澱粉粉末成型。

The production of bioplastics crosses over with both thermoplastics and thermosets : they can be molded with thermoplastic technology . But the process may not be repeatable . Cellulose acetate ( CA ) and Polylactic acid are processed using similar techniques to thermoplastics . For example , Potatopak food packaging is produced by compression molding powdered starch.

材料的發展

MATERIAL DEVELOPMENTS

塑料產業一直在發展，新的混合劑，化合物和添加劑的研發給塑料產業提供了很多潛在機會，從而提升生產質量並降低成本。快速成型技術的發展也革新的設計過程，除了把成品誤差控制在幾微米之間外，也可以實現傳統塑料工藝不能實現的產品造型。某些塑料，例如環氧樹脂，填充尼龍，玻璃和碳填充尼龍，這些塑料之前的生產方式一直和大批量生產級塑料一樣（如ABS和PMMA）。然而，如今已經這些塑料已經可以實現小批量和單件生產，當然也包括產品手板。

The plastics industry is constantly evolving . New blends , compounds and additives are being developed to create opportunities , improve performance and reduce cost . Rapid prototyping has revolutionized the design process . not only are models accurate to within a few microns , but also this process is capable of producing plastic parts that cannot be made in piece in any other way . Plastics available include epoxy resin , unfilled nylon , and glass or carbon filled nylon. Traditionally these materials have been engineered to mimic production grade plastics such as acrylonitrile butadiene styrene and poly methyl methacrylate acrylic. Recent developments have made it suitable for direct manufacturing low volume parts and one offs as well as pre - production models.

導電多聚物融合了塑料工藝和金屬導電性的優勢，例如：電路列印，發光塑料和導電活性多聚物。電路列印是在塑料上進行的，這種新興科技可以改變我們的閱讀方式；依靠傳統非結晶矽顯示的硬質玻璃背板已經被塑料取代，意味著顯示屏變得更加輕薄；通過電發光原理的發光多聚物，當電流經過多聚物時可以自發光，如今已經可以放射不同顏色的光，從而實現了薄板顯示屏。

Conductive polymers combine the benefits of plastics technology with the conductivity of metals . Developments include printed circuitry , light emitting plastics and electroactive polymers. Printed circuitry is used in plastic. This technology has the potential to revolutionize the way we read books . reports and even the morning paper. The rigid glass back pane required for conventional amorphous silicon-based displays has been replaced by a plastic . which means the display can be flexible thinner and more lightweight. Light emitting polymers are based on the principles of electroluminescence. Polymer lights up when an electrical current is passed through it it is now possible to emit different colours of light to produce very thin flat panel displays.

環境影響

ENVIRONMENTAL IMPACTS

為了降低塑料對環境的影響，人類也做了很多努力嘗試。例如，一次性塑料現在由添加的生物活性添加劑的熱塑性塑料製成，熱塑性的循環利用率很高，有些甚至是100%的可循環材料。設計師的責任應該是確保塑料可以在汙染最小的情況下被回收，儘量使用單中塑料製作產品部件，時刻把可回收和可拆卸帶入自己的設計步驟中。

There have been many develop that reduce the environmental impacts of plastics . For example , many disposable products are produced in bioplastics thermoplastic with bioactive additives. Thermoplastics are very efficient to recycle there is minimal degradation of quality and some products are from 100 % recycled materials. the role of the designer is to ensure that plastics can be recycled with minimal contamination therefore parts should be designed in a single material if possible and with recycling and disassembly in mind.

提起汙染，塑料常常因為需要千年來完全降解而被人詬病，有一些塑料甚至在生產中就對環境有傷害，例如：聚酯，含有苯乙烯的環氧樹脂，酚脂。這些都是有汙染和一定毒性的。

This book cannot avoid mentioning the negative environmental impacts of certain plastics not only do they take thousands of years to biodegrade， some are also harmful in production . For example , polyester and epoxy contain styrene ，phenolic resin .these chemicals are known pollutants and are toxic.

有一些塑料被認為是不穩定的，具有致癌性的有機化合物。在生產過程中，一定要防止吸入人體。有一些塑料在使用周期裡甚至會釋放有害氣體，降低空氣品質並汙染環境。

Some are referred to as volatile organic compounds and are known carcinogens . during production care must be taken to avoid inhaling them , and some plastics will continue to off - gas during their lifetime and so both reduce indoor air quality and pollute the atmosphere.

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