The basics: understanding different plastics

exist 1967annualUSADustin in the movie “The Graduate”·Played by Huffmanmale protagonistbe informed about plasticIt’s a promising industry。 Does the male protagonist agree?ThisWe have no way of knowing what we think,But more than fifty years later, we now knowmanufacturingALL RIGHTIndustryI completely agree with this point of view,Plastics are now widely used in the manufacturing sector, includingMany types of plasticAndSimilar to plasticcovering almost all industrial categories, and has become an inseparable part of our lives.

ForbeginnerIn simple terms,There is a lot of plasticdifferent typeswhat are the differences and connections between different plastics? This confusion is usually due to the following reasons:

✓ No notion of relationship between the structure of the material and its properties.

✓ Product material performanceGenerally noReceive enough attention and not be assignedEnough time and effort.

✓ Even after overcomingaboveTwo obstacles, it is also difficult to find precise data on material properties.

for yourProduct selectionsuitable materialsmeetinginvolvingarriveWillData from various sources. Data from each source may be incomplete, overlapping and contradictory. You must combine this incomplete or even contradictory data.integrated together. For a material, the most important thing to consider is itsMaterial data sheet（MDS,Material data sheet）,A good suggestion isyou shouldas much as possiblefrom thatsurfacemediumgetGet as much information as possible. SometimesAlsoCan be obtained fromeachFor more detailed information, refer to the design manuals and application notes published by the material supplier.used forcan fillMaterialEmpty spaces in the data table. Complete and detailed documentsinformationGenerallyHigh-performance engineering and special materialsOnly there (to show the superiority of performance), and some common affairsProduct materialInformation may be missing。 ifYourealneedUnderstand a subject, youIn addition to searching for information, you can alsoneedDo some experiments and testsWork.

thermoplastic

Thermoplastic is a plastic that evolves above a certain temperaturesoft, becomeCanmoldmolded then solidified upon coolingand this process is repeated back and forth, soThermoplastics are often used in injection moldingand can usually be recycled again.

What happens to thermoplastics when heatedShow professionalismthe termJust say itIt’s a phase change. A very common example of a material undergoing a phase change iswaterexistIt turns into ice below zero and ice turns into water above zero. lower than thatphase changetemperature,MaterialIt’s solidStateabove this temperature,MaterialIt’s liquidState。

Some common thermoplastics

✓Acetal Acetalalso known as Delrin

✓ Acrylic(Acrylic, PMMA, polymethyl methacrylate）

✓ Acrylonitrile Butadiene Styrene (ABS,Acrylonitrile butadiene styrene)

✓ nylon Nylon (PA, Polyamide)

✓ polycarbonate (Polycarbonate PC )

✓ polyethylene (PE Polyethylene)

✓ polylactic acid (PLA, Polylactic acid)

✓ polypropylene (PP, Polypropylene)

✓ polystyrene (P.S.,Polystyrene)

✓ PTFE (PTE,polytetrafluoroethylene)also known as Teflon

✓ PVC (PVC,Polyvinyl chloride)

thermoset plastic

The name thermoset can seem a little confusing, especially when compared to thermoplastics (see previous section). A thermoset is a material that hardens irreversibly rather thanheatingMaterials that can be released. Remember the difference between these two plasticsThe easiest way is probably to use thermoplasticsThe heating is reversible, whilethermoset plasticIt isPermanent deformation.

thermoset materialsaccording tomaterialDifferent ingredientscan undergo a chemical reactionsolidifyor radiation hardening. Liquid silicone isa commonMoldableofThermoset materials.

Thermoset materials are generally more durable than thermoplastic materialsstrong,AlsoCanUsed in various casting processes。

Common thermoset plastics include:

✓Bakelite

✓ Epoxy resin

✓ Melamine

✓ Polyurethane (also found in thermoplastics, but less commonlySee）

✓ RTV Silicone

✓ silicone rubber

photopolymer

PhotosensitiveA polymer is a plastic,Before the liquid state is cured, it is often called photoresist.existlightingwill change its characteristicsa hardening reaction occurs。 These plastics are usually cured with UV light and harden very quickly. PhotosensitiveResinUsually used for3D PrintAndSimilar process(asUVprinting, etc.). Photopolymers tend to be more fragile than other types of plastics and are often unstable when exposed to sunlight or high humidity. Like thermosets, photopolymers also undergoirreversibleThe curing process, once hardened, cannot be softened again. when used for3DWhen printing and other processes,photosensitive resinWill harden layer by layer. usually viaa UV laserheadPaint (and cure) a coat on the resinComponentthen set the workbenchdeclinea layerhigh, SOAgainThe next layer is painted and cured, the processin progressuntil the wholeComponentform.

Photoresist is one of the important raw materials in digital manufacturing.ResinUsed to make products with certain characteristicsPhotopolymer.

Compare plastic and plastic

Technologyperspectivenot anything that looks like plasticImmediatelyEverything is plastic. Thermosetplasticand photosensitive polymersperformance behaviorwith truth“plastic»different,Although it is normal that ordinary people are not able to tell the difference.But if youDo you want to become an expert or just want to learn a little more?It is still interesting to compare plastics with similar plastics。

Stereolithography (a commonly used additive manufacturing process that can be shortened to SLA）OriginalThe material isphotosensitive resinrather than thermoplastics, therefore inA fewon key featuresYesUnlike ordinary engineering grade resin. despite this,These types of plasticsRIGHTdesignerand engineersis always very useful,if onlyThey are somewheresome dimensionsabove and expectedfinalthe production materials match, then theyalwayscan be used forAppearance、assemblyand limitedofFunctional tests. Usually, designersand engineersmostlookThe most important property is stiffness (technical term tensile modulus), SO,If the raw material is ABS type material when itgenerally refers to the materialAndABSofStiffness is similar, while other material properties can vary significantly.

PhotosensitiveEngineering grade materials and thermoplasticsMost common propertiesdifferentYesElongation at break (degree of stretch before break, measured as a percentage) and temperature strength (temperature before softening).The elongation at break and temperature resistance of photosensitive polymers are much lower than those of corresponding engineering plastics.

allPhotosensitivePolymers all have long-term sensitivity to oxygen,That is to say, if exposed to an oxygenated environment for a long time, various properties will age and degrade.and this sensitivityAs the temperature increases, it will increase。 measureagingThe general performance index isrelative heat index (Relative thermal index, RTI)。 Thisis currently measuredagingRIGHTPhotosensitivePolymer machineofOptimal long-term impact on mechanical and electrical performancemethod。 RTI Start by measuring key core attributes, The samples are then tested at several temperaturesofaging, monitoringThatbaselinepropertyuntil they return to their original values 50%. reach 50% The time required for execution is calledInvalidtime.

Choose the right plastic

If you don’t understandAComplete partsofapplicationperformanceThe request cannot be madecompletely accuratematerialchoose. butIf it is sometimes unprofitable to carry out too many technical calculations in advance for material selection, then how to choose a suitable material for the product?DownBelow we offer some quick options for plasticGeneral rule:

✓ to try ABS。 ABS Suitable for many applications. It’s reasonably priced, sturdy, relatively durable, beautiful, and forgiving even if you don’t follow all the standard design rules for plastic parts.buthemelting pointIt is indeed relatively weak.

✓ if necessaryEvencheap andStronger,AndAppearanceNot very important, try polypropylene (PP)。

✓ If you need to compare ABS For something sturdier or able to withstand higher temperatures, try polycarbonate (computer),PCNot as good asABSNext, tolerant design rules require an understanding of the design rules for plastic parts.。

✓ If you need beauty and transparency, try acrylic (PMMA）。 PMMA It might be a little crunchy.

transparent PC I will compare PMMA More solid, but less aesthetic.

✓ If these rules do not haveChoose the right materialthen you have to do the math andprojectanalyze.

If you are considering using injection moldingTO DOparts you canBefore making the mold, several parts are machined using different candidate target materials, then the mold is made once the final material is determined. It isMoldexistdesignhourYesneedmatchGot itidentificationMaterialofproperty,The resin shrinks as it hardens,Different resins have different shrinkage rates.So it may not be possible in the same moldto useVarious resinsdifferent resins canPart dimensions, tolerances andPrecisioncreate risks.