長(zhǎng)方形盒蓋的注塑模具設(shè)計(jì)--塑料注射模說(shuō)明書

長(zhǎng)方形盒蓋的注塑模具設(shè)計(jì)--塑料注射模說(shuō)明書,長(zhǎng)方形,盒蓋,注塑,模具設(shè)計(jì),塑料,注射,說(shuō)明書,仿單 外文資料翻譯 資料來(lái)源：書籍 文章名：Chapter 2 The Properties of Plastics 書刊名：《English for Die & Mould Design and Manufacturing》 作 者：劉建雄 王家惠 廖丕博 主編 出版社：北京大學(xué)出版社，2002 章 節(jié)：2.2 The Properties of Plastics 頁(yè) 碼：P24~P31 文 章 譯 名： 塑料的性能 The?Properties?of?Plastics Plastics are organic materials made from large molecules that are constructed by a chain-like attachment of certain building-block molecules. The properties of the plastic depend heavily on the size of the molecule and on the arrangement of the atoms within the molecule. For example, polyethylene is made from the ethylene building block that is initially a gas.Through?a process?called?polymerization,?a?chain?of?ethylene?molecules?isformed?by?valence?bonding?of??the?carbon?atoms?within?the?ethylene?molecule.?The?high?molecular?weight?product?which?results?iscalled?a?polymer.?Hence,?the?designation?polyethylene?is?used?todistinguish?the?high-?molecular-weight?plastic?from?its?gaseous?counterpart,?ethylene,?which?is?the?monomer?that?becomes?polymerized.The?“poly”?refers?to?the?“many”?ethylene?building?block?molecules?or?monomers,?which?join?to?form?the?polyethylene?plastic?molecule.Frequently,?the?term?“resin”?is?used,?interchangeably?with?“polymer”?to?describe?the?backbone?molecule?of?a?plastic?material.?However,?“resin”?is?sometimes?used?to?describe?a?syrupy?liquid?ofboth?natural?and?synthetic?resin. Plastics,?in?the?finished?product?form,?are?seldom?comprised?exclusively?of?polymer?but?also?include?other?ingredients?such?as?fillers,?pigments,?stabilizers,?and?processing?aids.?However,?designation?of?the?plastic?material?or?molding?compound?is?always?takenfrom?the?polymer?designation. Broadly?speaking?plastics?may?be?divided?into?two?categories:?thermoplastics?and?thermoset?plastics.?The?classes?of?materials?areso?named?because?of?the?effect?of?temperature?on?their?properties. 2.2.1Thermosets Thermoset?plastics?are?polymers?which?are?relatively?useless?intheir?raw?states.?Upon?heating?to?a?certain?temperatureaa?chemical?reaction?takes?place?which?causes?the?molecules?to?bond?togetheror?cross-link.?After?vulcanization?and?polymerization,?or?curing,the?thermoset?material?remains?stable?and?cannot?return?to?its?original?state.?Thus,?a”?thermo-seta”??identifies?those?materials?that?become?set?in?their?useable?state?resulting?from?the?addition?of?heat.?Normally,?a?thermoset?polymer?is?mixed?with?fillers?and?reinforcing?agents?to?obtain?the?properties?of?a?molding?compound. Thermosets?are?the?hardest?and?stiffest?of?all?plastics,?are?chemically?insoluble?after?curing,?and?their?properties?are?less?affected?by?changes?in?temperature?than?are?the?heat-sensitive?thermoplastics.?The?closest?non-plastic?counterparts?to?thermosets?in?properties?are?ceramics.?Common?examples?of?thermoset?plastics?are:?phenolics,?melamine,?urea,?alkyds,?and?epoxies.?Molding?compounds?madefrom?these?polymeric?resins?always?contain?additional?fillers?and?reinforcing?agents?to?obtain?optimum?properties. 2.2.2Thermoplastics Thermoplastic?polymers?are?heat-sensitive?materials?which?are?solids?at?room?temperature,like?most?metals.?Upon?heating,?the?thermoplastics?begin?to?soften?and?eventually?reach?a?melting?point?and?become?liquid.?Allowing?a?thermoplastic?to?cool?below?its?melting?point?causes?resolidification?or?freezing?of?the?plastic.?Successive?heating?and?cooling?cycles?cause?repetition?of?the?melting-freezing?cycle?just?as?it?does?for?metals. The?fact?that?thermoplastics?melt?is?the?basis?for?their?processing?into?finished?parts.?Thermoplastics?may?be?processed?by?any?method?which?causes?softening?or?melting?of?the?material.?Examples?of?thermoplastic?fabrication?techniques?using?melting?are:?injection?molding,?extrusion,?rotational?casting,?and?calendering.?Fabrication?methods?which?take?advantage?of?softening?below?the?melting?point?are:?thermoforming?(vacuum?or?pressure),?blow?molding,?and?forging.?Of?course,?normal?metal-cutting?techniques?can?also?be?applied?to?thermoplastics?in?the?solid?state.?Common?examples?of?thermoplastics?are:?polyethylene,?polystyrene,?polyvinyl?chloride?(PVC),?and?nylon?(polyamide). 2.2.3Fillers Plastics?often?contain?other?added?materials?called?fillers.?Fillers?are?employed?to?increase?bulk?and?to?help?impart?desired?properties.?Plastics?containing?fillers?will?cure?faster?and?hold?closer?to?established?finished?dimensions,?since?the?plastic?shrinkage?will?be?reduced.?Wood?flour?is?the?general-purpose?and?most?commonly?used?filler.?Cotton?frock,?produced?from?cotton?linters,?increases?mechanical?strength.?For?higher?strength?and?resistance?toimpact,?cotton?cloth?chopped?into?sections?about?1/2-inch?square?can?be?processed?with?the?plastic.?Asbestos?fiber?may?be?used?as?a?filler?for?increased?heat?and?fire?resistance,?and?mica?is?used?for?molding?plastic?parts?with?superior?dielectric?characteristics.?Glass?fibers,?silicon,?cellulose,?clay,?or?nutshell?flour?mayalso?be?used.?Nutshell?flour?is?used?instead?of?wood?flour?where?a?better?finish?is?desired.?Plastic?parts?using?short?fiber?fillers?will?result?in?lower?costs,?while?those?with?long?fiber?fillers?having??greater?impact?strengths?are?more?expensive.?Other?materials,?not?defined?as?fillers,?such?as?dyes,?pigments,?lubricants,?accelerators,?and?plasticizers?may?also?be?added.?Plasticizers?are?added?to?soften?and?improve?the?moldability?of?plastics.?Filler?and?modifying?agents?are?added?and?mixed?with?the?raw?plastic?before?it?is?molded?or?formed. 2.2.4Properties?of?Plastics 1.General?Properties The?problem?of?selecting?plastic?materials?is?that?of?finding the?material?with?suitable?properties?from?the?standpoint?of?intended?service,?methods?of?forming?and?fabricating,?and?cost. New?and?improved?plastic?materials?possessing?almost?any?desired?characteristic?are?being?introduced?continually.?There?are?plastics?that?do?not?require?plasticizers?that?have?greater?flexibility?under?lower?temperatures,?and?are?stable?under?higher?temperatures.?Some?resist?water,?acids,?oils,?and?other?destructive?matter.?The?wide?use?of?plastics?testifies?to?their?value;?however,?fundamental?limitations?should?be?considered?when?applying?a?new?material?or?adapting?an?old?material?to?new?applications. 2. Effects?of?Temperature Plastics?are?inclined?toward?rigidity?and?brittleness?at?low?temperatures,?and?softness?and?flexibility?at?high?temperatures.?They?are?fundamentally?unstable?dimensionally?with?respect?to?temperature,?and?are?susceptible?to?distortion?and?flow?when?subjected?to?elevated?temperatures.?The?thermoplastics?are?particularly?susceptible,?while?the?thermosetting?plastics?are?much?more?resistant,?differing,?however,?only?in?degree.?The?distinction?between?the?thermal?stability?of?the?thermosetting?and?thermoplastic?resins?is?not?well?defined.?A?true?distinction?can?be?drawn?only?between?individual?plastics,?rather?than?between?classes?of?plastics.?High?temperatures?not?only?seriously?reduce?the?mechanical?properties?of?plastics,?but?also?accelerate?the?destructive?action?of?external?agents?to?which?they?are?sensitive.?Continuous?heating?also?may?induce?brittleness?and?shrinkage?in?heavily?plasticized?materials?by?volatilization?of?plasticizers.?The?use?of?one?plastic?in?contact?with?a?dissimilar?plastic?in?a?proposed?application?should?be?checked?first?in?the?light?of?possible?a”?migration?of?plasticizera”?,?sometimes?resulting?in?discoloration?or?hardening?of?one?of?the?plastics. In?general,?moderate?temperatures?are?required?for?storage?of?plastics?over?long?periods;?low?temperatures?are?to?be?avoided?because?of?the?low-temperature?brittleness?of?most?of?the?plastics,?and?high?temperatures?should?be?avoided?because?of?the?rapid?loss?of?mechanical?properties,?volatilization?of?plasticizers,?and?the?susceptibility?of?a?large?number?to?distortion. Plastics,?with?only?a?few?exceptions,?are?extremely?sensitive?to?the?effects?of?water.?High-?humidity?atmospheres?induce?water?absorption?and?varied?resulting?effects,?depending?upon?the?composition?and?formulation?of?the?plastics.?Increased?water?content?plasticizes?some?materials,?and?there?is?a?general?lowering?of?the?mechanical?properties.?Water?absorption?is?responsible?for?swelling?in?certain?plastics?and?the?ultimate?decomposition?of?a?few.?Moist?or?wet?atmospheres?may?extract?plasticizers?from?heavily?plasticized?materials?and?also?provide?conditions?favorable?to?fungal?growth.?In?recent?years,?however,?new?plastics?have?come?into?use?that?have?first-class?moisture?resistance?and?may?contain?water?indefinitely?while?resisting?other?influences?at?the?same?time. Extremely?dry?environments?may?cause?brittleness?in?certain?plastics?as?a?result?of?loss?of?water?that?normally?contributes?to their?plasticity.?Cyclic?wet?and?dry?atmospheres?are?more?destructive?to?plastics?than?continuous?exposure?at?constant?humidity?because?of?the?mechanical?stresses?induced?in?the?plastics?by?swelling?and?shrinking?with?moisture?absorption?and?moisture?emission.?Relatively?constant,?moderate?to?low?humidities?are?preferred?for?plastic?storage?because?of?the?adverse?effects?of?water?on?the?structure?and?properties?of?these?materials,?and?the?possibility?of?plasticizer?loss?by?extraction?and?fungal?attack?in?moist?atmospheres 3.Effects?of?Light Prolonged?exposure?to?sunlight?will?affect?adversely?all?plastics?with?exception?of?tetrafluoroethylene?(Teflon).?The?change?induced?by?the?ultraviolet?components?may?vary?in?kind?and?severity?from?slight?yellowing?to?complete?disintegration?as?a?result?of?the?chemical?degradation?of?the?polymeric?compound?or?plasticizers.?Loss?of?strength,?reduced?ductility,?and?increased?fragility?usually?accompany?such?action.?Many?plastics?are?offered?in?special?formulations?containing?“ultraviolet?inhibitors”?which?should?be?utilized?when?this?influence?is?present.?Exposure?of?plastics?to?sunlight?during?storage?should?be?avoided,?especially?when?the?transparency?of?clear?materials?is?to?be?preserved. 4.Weight As?a?family,?plastics?are?light?when?compared?to?metals.?Mostplastics?have?a?specific?gravity?between?1.35?and?1.45,?which?is?less?than?that?of?magnesium. 5.Electrical?Resistivity Plastics?have?excellent?electrical?resistivity?making?them?have wide?application?as?an?insulating?material.?In?the?high-frequency?applications,?plastics?are?particularly?advantageous?and,?consequently,?are?being?used?to?a?large?extent?in?the?fields?of?radar?andtelevision. 6.Heat?Insulation Plastics?have?low?heat?conduction?and,?consequently,?have?application?as?an?insulating?material.?In?particular,?they?are?used?ashandles?for?appliances?and?tools?subjected?to?heat. Fabrication The?principal?characteristic?of?plastics?from?fabrication?standpoint?is?case?of?molding.?Both?thermosetting?and?thermoplastic?materials?lend?themselves?to?molding?irregular?and?complex?shapes?withrelatively?short?curing?cycles. Plastics?may?be?joined?by?using?various?cements,?chemical?solvents,?and?mechanical?fasteners.?Heat-sealing,?which?parallels?somewhat?the?welding?process?of?metals,?is?used?extensively?in?joining light?thermoplastic?films.?In?such?cases,?dielectric?heating?is?the?technique?usually?used.?Friction?adhesion?has?had??moderate?application?also?in?the?joining?of?small?thermoplastic?parts. Plastics?can?be?machined?with?conventional?machine?tools.?However,?certain?cautions?should?be?exercised.?In?order?to?maintain?a good?finish,?a?heavy?flow?of?coolant?should?be?used?so?as?to?avoid?temperatures?that?will?distort?the?work.?In?some?thermosetting?laminates?(glass,?for?example),?the?customary?high-speed?steel?tool?will?not?stand?up?in?view?of?the?abrasive?action?of?the?laminating?material.?Here,?either?tungsten?carbide?or?ceramic?cuttingtools?must?be?used. 7.Effects?of?Oxygen Organic?plastics?are?nearly?all?subject?to?oxidation?when?exposed?to?the?atmosphere.?The?process?is?accelerated?by?high?temperatures?and?light;?but,?over?long?periods?of?time,?oxidative?deterioration?may?take?place?at?room?temperature.?Oxidation?susceptibility?depends?largely?upon?the?chemical?nature?of?the?plastic?and?its compounding.?Materials?with?the?greatest?number?of?double?bonds in?their?molecular?structure?will?generally?be?the?most?sensitive to?oxidation.?Yellowing?and?a?gradual?loss?of?strength?and?ductility?are?the?principal?results?of?oxidative?processes. Oxidation?is?not?a?problem?of?great?magnitude?in?storage,?since?the?rigid?plastics?are?rather?resistant?to?oxidative?deterioration under?moderate?conditions. 8.Effects?of?Loading Under?moderate?conditions?the?common?thermoplastic?materials?aresubject?to?distortion?and?flow?when?significantly?loaded.?Such?plastics?cannot?be?expected?to?maintain?a?high?degree?of?mechanical stability?over?extended?periods?when?subjected?to?stress;?especially?is?this?true?when?they?are?also?exposed?to?relatively?high?temperatures.?The?thermoplastics?should,?however,?ma-?intain?themselves?fairly?well?when?not?subject?to?load?or?when?subjected?to?only?moderate?load.?Recently,?fillers,?such?as?glass?wool,?have?beenadded?to?thermoplastics?to?further?improve?this?property. The?thermosetting?plastics?are?much?more?load-stable?than?the?thermoplastics?because?of?their?structure?and?the?inclusion?of?fillers?in?their?formulation.?In?the?laminated?form?they?provide?a?rather?high?order?of?distortion?and?creep?resistance.?When?not?subjected?to?mechanical?stress?they?may?be?considered?to?be?highlystable.?These?materials,?however,?may?suffer?creep?over?long?periods,?especially?when?maintained?at?elevated?temperatures. The?thermoplastic?types?should?not?be?subjected?to?load?when?stored;?and,?whenever?possible,?the?loading?of?stress-bearing?thermosetting?moldings?or?laminates?should?be?removed?or?reduced. 10. Chemical?Stability Plastics,?in?general,?possess?a?high?degree?of?inherent?stability?with?respect?to?chemical?deterioration.?In?many?instances,?this?stability?may?be?fortified?by?the?addition?of?the?proper?stabilizers?during?compounding.?While?there?is?vast?difference?from?oneplastic?to?another,?the?general?statement?may?be?made?that?there is?a?plastic?available?to?resist?virtually?any?commercial?chemical.. 塑料的性能 熱塑性塑料熔體是熱塑性塑料加工成品的基礎(chǔ)。熱塑性塑料可以用任何方法加工，導(dǎo)致材料軟化或熔化。t的例子采用熔融的氣塑制造技術(shù)有：注射成型、擠壓、旋轉(zhuǎn)鑄造和壓延。利用熔點(diǎn)以下軟化的制造方法有：熱成型(真空或壓力)，吹塑，鍛造。當(dāng)然，普通的金屬切削技術(shù)也可以應(yīng)用于固態(tài)熱塑性塑料.熱塑性塑料的常見例子CS為：聚乙烯、聚苯乙烯、聚氯乙烯(PVC)和尼龍(聚酰胺)。 2.2.3填料 塑料是由大分子制成的有機(jī)材料，由某些積木分子組成的鏈狀附著體構(gòu)成。塑料的性能在很大程度上取決于o的大小。f分子和原子在分子內(nèi)的排列。例如，聚乙烯是由最初是氣體的乙烯構(gòu)件制成的。通過(guò)聚合法乙烯分子中的碳原子價(jià)鍵形成了一條乙烯分子鏈。高分子量的產(chǎn)物被稱為聚合物。因此，聚乙烯是用來(lái)區(qū)分高分子量塑料與其氣態(tài)對(duì)應(yīng)物乙烯，乙烯是聚合的單體?！皃oly”指的是“多”et。聚烯類物質(zhì)的組成分子或單體，它們連接在一起形成聚乙烯塑料分子。經(jīng)常使用“樹脂”一詞，并與“聚合物”互換來(lái)形容背板。塑料的分子。然而，“樹脂”有時(shí)被用來(lái)描述天然和合成樹脂的糖漿液體。塑料，以成品的形式，很少被包括在內(nèi)。廣泛的聚合物，但也包括其他成分，如填料，顏料，穩(wěn)定劑，和加工助劑。然而，塑料材料或模塑化合物的名稱總是從聚合物稱廣義地說(shuō)，塑料可分為兩類：熱塑性塑料和熱固性塑料。由于溫度的影響， 2.2.1熱固性材料 熱固性塑料是一種聚合物，在其原始狀態(tài)下是相對(duì)無(wú)用的。在加熱到一定溫度時(shí)，會(huì)發(fā)生化學(xué)反應(yīng)，使分子結(jié)合在一起，或交叉鏈接。經(jīng)過(guò)硫化、聚合或固化后，熱固性材料保持穩(wěn)定，不能恢復(fù)到原來(lái)的狀態(tài)。因此，“熱集”識(shí)別了那些成為由于加溫而處于可用狀態(tài)。通常，熱固性聚合物與填料和增強(qiáng)劑混合，以獲得模塑化合物的性能。 熱固性塑料是所有塑料中最堅(jiān)硬、最堅(jiān)硬的，固化后不溶于化學(xué)，其性能受溫度變化的影響小于熱敏熱塑性塑料。抽搐。與熱固性材料最接近的非塑性材料是陶瓷。熱固性塑料的常見例子有：酚醛、三聚氰胺、尿素、醇酸和環(huán)氧。成型化合物f這些樹脂總是含有額外的填料和增強(qiáng)劑，以獲得最佳的性能。 2.2.2 熱塑性塑料 熱塑性聚合物是一種熱敏材料，在室溫下是固體，就像大多數(shù)金屬一樣。加熱后，熱塑性塑料開始軟化，最終達(dá)到熔點(diǎn)，變成液體。允許熱塑性塑料冷卻到其熔點(diǎn)以下會(huì)導(dǎo)致溶解。塑料的凍結(jié)或凍結(jié)。連續(xù)的加熱和冷卻循環(huán)會(huì)導(dǎo)致熔化-凍結(jié)循環(huán)的重復(fù)， 塑料通常含有其它被稱為填料的附加材料。使用填料來(lái)增加體積并幫助賦予所需的性能。含有填料的塑料將更快地固化并保持更緊密以確定成品尺寸，由于塑料收縮將減少。木粉是一種通用的，也是最常用的填充劑.棉質(zhì)長(zhǎng)袍，由棉短絨制成，增加。機(jī)械強(qiáng)度。為了更高的強(qiáng)度和抗沖擊能力，將棉布切成約1/2英寸的方形，可以用塑料加工。石棉纖維可用作填充劑提高了耐熱性和耐火性，云母用于成型具有優(yōu)良介電特性的塑料零件。玻璃纖維、硅、纖維素、粘土或殼面也可以使用。n在需要更好的光潔度的地方，用utshell面粉代替木粉。使用短纖維填料的塑料零件會(huì)降低成本，而長(zhǎng)纖維填料的成本會(huì)更高。行動(dòng)能力更昂貴。其他未定義為填料的材料，如染料、顏料、潤(rùn)滑劑、促進(jìn)劑和增塑劑也可加入。增塑劑被添加到軟化和IM中。證明塑料的可模塑性。填充劑和改性劑在成型或成型之前，先加入原塑料，然后與其混合。 2.2.4塑料性能 1. 一般特性 塑料材料的選擇問(wèn)題是從服務(wù)目的、成型方法、制造方法、成本等方面尋找性能合適的材料。新的和改進(jìn)的塑料材料具有幾乎任何所需的特性正在不斷引入。有些塑料不需要具有更大柔韌性的增塑劑。呃溫度低，在高溫下是穩(wěn)定的。有些能抵抗水、酸、油和其他破壞性物質(zhì)。塑料的廣泛使用證明了它們的價(jià)值；然而，基本的l在應(yīng)用新材料或使舊材料適應(yīng)新應(yīng)用時(shí)，應(yīng)考慮模仿。 2. 溫度效應(yīng) 塑料在低溫下傾向于剛性和脆性，在高溫下傾向于柔軟和靈活。就溫度而言，它們?cè)诔叽缟匣旧鲜遣环€(wěn)定的。，并且在高溫下易受變形和流動(dòng)的影響。熱塑性塑料特別敏感，而熱固性塑料則更耐高溫，差別很大。然而，吳只在學(xué)位方面。熱固性樹脂和熱塑性樹脂的熱穩(wěn)定性之間的區(qū)別還沒有很好地界定。只有在單個(gè)pl之間才能進(jìn)行真正的區(qū)分。不是在塑料類之間。高溫不僅嚴(yán)重降低了塑料的力學(xué)性能，而且加速了外界因素對(duì)Wi的破壞作用。它們很敏感。連續(xù)加熱也可通過(guò)增塑劑的揮發(fā)而在嚴(yán)重增塑材料中引起脆性和收縮。一種塑料與迪西米的接觸在提議的應(yīng)用中，LAR塑料應(yīng)首先根據(jù)可能的“增塑劑遷移”進(jìn)行檢查，有時(shí)會(huì)導(dǎo)致其中一種塑料變色或硬化。 一般來(lái)說(shuō)，塑料的長(zhǎng)期儲(chǔ)存需要適度的溫度；由于大部分塑料的低溫脆性，所以必須避免低溫。由于力學(xué)性能的迅速喪失、增塑劑的揮發(fā)和大量變形的敏感性，應(yīng)避免Gh溫度的升高。 塑料，除了少數(shù)例外，對(duì)水的影響極為敏感。高濕度的大氣會(huì)引起不同的吸水率，并會(huì)產(chǎn)生不同的影響，這取決于成分。塑料的配方。水分含量的增加使一些材料的力學(xué)性能普遍下降。吸水是導(dǎo)致宮頸腫脹的原因。在塑料和最終分解的幾個(gè)。潮濕或潮濕的大氣可以從高度塑化的材料中提取增塑劑，也可以為真菌的生長(zhǎng)提供有利條件。參考文獻(xiàn)然而，在過(guò)去的幾年里，新塑料已經(jīng)投入使用，它們具有一流的防潮性能，并且在抵抗其他影響的同時(shí)，也可能無(wú)限期地含有水。 極度干燥的環(huán)境可能會(huì)導(dǎo)致某些塑料材料的脆性，這是由于水分的流失，而水的流失通常會(huì)導(dǎo)致塑料的可塑性。循環(huán)潮濕和干燥的大氣對(duì)塑料比連續(xù)暴露在恒定濕度下，由于機(jī)械應(yīng)力在塑料中引起的溶脹和收縮與吸濕和水分排放有關(guān)。相對(duì)由于水對(duì)這些材料的結(jié)構(gòu)和性能的不利影響，以及增塑劑lo的可能性，所以在塑料儲(chǔ)存中首選恒定、中、低濕度。潮濕大氣中的SS提取與真菌攻擊 3. 光的影響 長(zhǎng)時(shí)間暴露在陽(yáng)光下會(huì)對(duì)所有塑料產(chǎn)生不利影響，但四氟乙烯除外（特氟?。? 紫外線成分引起的變化可能與S的種類和嚴(yán)重程度不同由于聚合物或增塑劑的化學(xué)降解而完全崩解。失去強(qiáng)度，降低延性，增加脆性通常是accom。有這樣的行動(dòng)。許多塑料是以含有“紫外線抑制劑”的特殊配方提供的，當(dāng)這種影響存在時(shí)，應(yīng)加以利用。期間塑料暴露于陽(yáng)光下應(yīng)避免儲(chǔ)存，特別是在要保持透明材料的透明度時(shí)。 4. 韋特 作為一個(gè)家庭，塑料與金屬相比是輕的。大多數(shù)塑料的比重在1.35到1.45之間，比鎂的比重小。 5. 電阻率 塑料具有優(yōu)異的電阻率，因而作為一種絕緣材料有著廣泛的應(yīng)用。在高頻應(yīng)用中，塑料特別有利，因此Y，在很大程度上被用于雷達(dá)和電視領(lǐng)域。 6. 絕熱 塑料具有低導(dǎo)熱性，因此作為絕緣材料有著廣泛的應(yīng)用。特別是，它們被用作受熱的電器和工具的把手。 7. 制造 從制造角度看，塑料的主要特點(diǎn)是成型。熱固性材料和熱塑性材料都適合于用Re成型不規(guī)則和復(fù)雜的形狀。固化周期短。 塑料可以使用各種水泥、化學(xué)溶劑和機(jī)械緊固件連接。熱密封與金屬的焊接過(guò)程平行，在連接熱密封中得到了廣泛的應(yīng)用。熱塑性薄膜。在這種情況下，電介質(zhì)加熱是通常使用的技術(shù)。摩擦粘著在小型熱塑性零件的連接中也有一定的應(yīng)用。 塑料可以用傳統(tǒng)的機(jī)床加工。但是，應(yīng)采取某些警告措施。為了保持良好的光潔度，應(yīng)使用大量的冷卻劑，以避免溫度升高。會(huì)扭曲作品的模型。在一些熱固性層壓板(例如玻璃)中，由于層壓材料的磨料作用，傳統(tǒng)的高速鋼工具將不會(huì)起立。艾爾。在這里，必須使用碳化鎢或陶瓷刀具。 8. 氧效應(yīng) 有機(jī)塑料在暴露于大氣中時(shí)幾乎都會(huì)受到氧化。這一過(guò)程是由高溫和光加速的，但在很長(zhǎng)一段時(shí)間內(nèi)，氧化惡化。可能在室溫下發(fā)生。氧化敏感性在很大程度上取決于塑料的化學(xué)性質(zhì)及其復(fù)配。m中雙鍵數(shù)最大的材料分子結(jié)構(gòu)通常對(duì)氧化最敏感。變黃和逐漸失去強(qiáng)度和延展性是氧化過(guò)程的主要結(jié)果。 氧化不是一個(gè)很大的儲(chǔ)存問(wèn)題，因?yàn)橛操|(zhì)塑料在中等條件下是相當(dāng)?shù)挚寡趸踊摹? 9. 加載效應(yīng) 在適當(dāng)?shù)臈l件下，普通熱塑性材料在顯著加載時(shí)會(huì)發(fā)生變形和流動(dòng)。這種塑料不可能維持高度的機(jī)械穩(wěn)定。當(dāng)他們承受壓力時(shí)，會(huì)長(zhǎng)時(shí)間處于狀態(tài)；尤其是當(dāng)他們也暴露在相對(duì)較高的溫度下時(shí)。然而，熱塑性塑料應(yīng)該是屬于自己的。當(dāng)不受負(fù)荷或只承受中等負(fù)荷時(shí)，良好。最近，在熱塑性塑料中加入了玻璃棉等填料，以進(jìn)一步改善這一性能。 熱固性塑料由于其結(jié)構(gòu)和填料的存在，比熱塑性塑料具有更高的負(fù)載穩(wěn)定性。在層疊形式中，它們提供了一個(gè)相當(dāng)不錯(cuò)的高次變形和抗蠕變性能。當(dāng)沒有受到機(jī)械應(yīng)力時(shí)，它們可以被認(rèn)為是高度穩(wěn)定的。然而，這些材料可能會(huì)長(zhǎng)期蠕變，特別是在高溫下保持。 熱塑性材料儲(chǔ)存時(shí)不應(yīng)承受載荷；凡有可能，應(yīng)移除或減少承受應(yīng)力的熱固性模塑或?qū)訅喊宓呢?fù)荷。 10. 化學(xué)穩(wěn)定性 一般來(lái)說(shuō)，塑料在化學(xué)退化方面具有高度的內(nèi)在穩(wěn)定性。在許多情況下，加入適當(dāng)?shù)姆€(wěn)定劑可以加強(qiáng)這種穩(wěn)定性。在復(fù)合過(guò)程中。雖然一種塑料和另一種塑料有很大的不同，但一般的說(shuō)法是，有一種塑料可以抵抗幾乎任何商業(yè)化學(xué)品。 12