Plastik krataa, sɛ́ mfiridwuma ne nneɛma a wɔde di dwuma a ɛho hia no, wɔde di dwuma kɛse wɔ adansi, nneɛma a wɔde kyekyere nneɛma ho, aguade ho dawurubɔ, nnuruyɛ mu mfiridwuma, ne mfuw afoforo mu. Ne adwumayɛ ne ne dwumadie ahodoɔ no, nea ɛkyerɛ titire ne nea ɛwɔ mu ne nea wɔpaw no. Saa asɛm yi bɛhwehwɛ nnyinasosɛm atitiriw a ɛwɔ plastic krataa mu no mu na wɔaka ne yɛ, nneɛma atitiriw a wɔde yɛ nneɛma, ne mfiridwuma mu nsɛm atitiriw ho asɛm kɔ akyiri, a ne botae ne sɛ ɛbɛma wɔanya nsɛm a wɔde gyina hɔ ma nnwuma a ɛfa ho.
I. Nnyinasosɛm atitiriw a ɛfa plastic krataa ho .
Plastik krataa no titiriw fi-molecular polymers (plastic resins) a wɔde honam fam anaa nnuru akwan ayɛ ho adwuma. Nea ɛka ho titiriw ne nneɛma a wɔde yɛ ade a ɛwɔ ase, nneɛma a wɔde ka ho, ne nneɛma a ɛboa. Base resin no na ɛkyerɛ sɛnea krataa no yɛ adwuma titiriw, ɔhyew a ɛko tia, ne nnuru a ɛyɛ den. Nneɛma a wɔtaa de gyina hɔ no bi ne polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polycarbonate (PC), ne acrylonitrile-butadiene-styrene copolymer (ABS).
Wɔde nneɛma a wɔde ka ho di dwuma de yɛ krataa no mu nneɛma pɔtee bi yiye, te sɛ:
1. Plasticizers: Ɛma ahoɔden a wɔde yɛ adwuma no tu mpɔn, a wɔtaa de di dwuma wɔ PVC nkratafa mu;
2. Stabilizers: Siw ɔhyew a ɛsɛe anaasɛ photooxidation, te sɛ kɔbere nkyene ne organotin nnuru ano;
3. Fillers: te sɛ calcium carbonate ne talc, tew ɛka so na ɛma rigidity tu mpɔn;
4. Ogya a ɛmma ogya ntumi nhyew: ɛma ogya a ɛko tia no yɛ kɛse, a ɛfata sɛ wɔde di dwuma wɔ adansi ne ɛlɛtrɔnik adwumayɛbea ahorow mu;
5. Colorants: Ma nkratafa kɔla pɔtee bi mma aesthetics anaa logos.
II. Akwan titiriw a wɔfa so yɛ plastic nkratafa .
Plastik krataa a wɔde yɛ nneɛma no gu ahorow, na akwan horow so nkɛntɛnso tẽẽ wɔ sɛnea ɛyɛ pɛpɛɛpɛ, ne kɛse yɛ pɛpɛɛpɛ, ne sɛnea wɔyɛ no yiye no so. Nea edidi so yi yɛ akwan a wɔtaa fa so yɛ no bi:
1. Extrusion .
Extrusion yɛ akwan a wɔtaa fa so yɛ plastic nkratafa no mu biako. Adeyɛ no fa resin pellets a wɔde frafra nneɛma a wɔde ka ho, ɔhyew ne nwene wɔ extruder mu, extruding no fa t{1}}wu mu nkratafa, afei fa three-roll calender ma shaping, cooling, na awiei koraa no wotwitwa no ma ɛyɛ nea wɔpɛ sɛ ɛyɛ nkyerɛkyerɛmu. Saa kwan yi fata ma thermoplastics te sɛ PE, PP, ne PVC. Ɛma mfaso a ɛwɔ nneɛma a wɔyɛ no daa ne nea ɛho ka sua so, nanso ne kɛse yɛ pɛ kɛse wɔ nsunsu ho nhyehyɛe so.
2. Calendering .
Calendering kwan no de rollers pii a ɛwɔ gap a wɔahyɛ so di dwuma de mia plastic a ayow kɔ nkratafa a ɛyɛ tratraa mu. Saa kwan yi fata ma nneɛma te sɛ PVC ne ABS, a ɛma-gloss a ɛkorɔn, ɛba fam-nkratafa a ɛyɛ den a wɔtaa de di dwuma wɔ ahosiesie ne nneɛma a wɔde kyekyere nneɛma mu. Ne mfaso no wɔ soro a ɛkorɔn a ɛyɛ tratraa, nanso ɛhwehwɛ sɛ wɔde nnwinnade a ɛho hia hyɛ mu na ɛwɔ ahwehwɛde ahorow a emu yɛ den wɔ nneɛma a wɔde yɛ nneɛma a wɔde yɛ nneɛma no ho.
3. Ɔhyew a wɔde mia .
Ɔhyew a wɔde mia no fata ma plastic a ɛyɛ hyew (te sɛ phenolic resins) anaa nkratafa akɛse a ɛyɛ den. Wɔde nneɛma a wɔde yɛ nneɛma a wɔayɛ no dedaw anaa nea wɔde ayɛ powder gu nkuku mu na wɔde ɔhyew a ɛkɔ soro ne nhyɛso kɛse sa. Saa kwan yi yɛ nea ɛyɛ mmerɛw kɛse na ebetumi ayɛ nkratafa a ɛwɔ nsusuwii a ɛyɛ den, nanso ɛma wonya nneɛma a wɔyɛ no yiye a ɛba fam na ɛma ahoɔden a wɔde di dwuma no kɔ soro.
4. CoExtrusion ne multilayer mfiridwuma a ɛwɔ ntoatoaso .
Sɛnea ɛbɛyɛ a nkratafa no nyinaa bɛyɛ adwuma yiye no, nnɛyi nneɛma a wɔyɛ no taa de coextrusion anaa lamination di dwuma. Sɛ nhwɛso no, wobetumi de substrate layer ayɛ wear-sentifed layer ne barrier layer de ayɛ soro-performance composite sheets. CoExtrusion de extruder ahorow pii di dwuma de ma nneɛma a ɛwɔ biakoyɛ mu, na ɛma multi-layer nhyehyɛe ahorow ba wɔ adeyɛ biako mu. Wɔde di dwuma kɛse wɔ soro-awiei adansi ne kar dwumadie.
iii. Mfiridwuma mu nsɛm titiriw ne nea wɔhwɛ so yiye .
Nneɛma pii a ɛka ho ne sɛnea plastic krataa so nneɛma no te ne sɛnea ɛyɛ papa, a nea ɛka ho ne nneɛma a wɔde yɛ nneɛma a wɔde yɛ nneɛma, sɛnea wɔyɛ no, ne sɛnea wɔyɛ nneɛma no pɛpɛɛpɛ. Nneɛma atitiriw a wɔde di dwuma no bi ne:
•Ɔhyew a wɔde di dwuma: ɔhyew a ɛkɔ soro dodo no betumi ama aporɔw aba, bere a ɔhyew a ɛba fam dodo no betumi anya nsu a ɛsen no so nkɛntɛnso;
•Pressure regulation: ɛma nneɛma kyekyɛ pɛpɛɛpɛ, ɛkwati ahurututu ne density a ɛnyɛ pɛpɛɛpɛ;
•Cooling rate: Ɛka krataa no crystallinity ne dimensional stability;
•Post-processing processes, te sɛ UV coating ne surface printing, betumi ama dwumadie akɔ so ayɛ yie.
iv. Awie
Ɔkwan a wɔfa so yɛ plastic krataa nneɛma no hwehwɛ sɛ wɔpaw no yiye a egyina sɛnea wɔde di dwuma no so. Efi mfitiase extrusion ne calendering so kosi coxtrusion ne compounding mfiridwuma a ɛkɔ anim so no, adeyɛ biara wɔ ne mfaso soronko ne nea wɔde di dwuma. Daakye, ɛnam nneɛma a ɛnyɛ nea atwa yɛn ho ahyia (te sɛ bio-gyina plastic) ne mfiridwuma a ɛyɛ nyansa a wɔde yɛ nneɛma so no, wɔbɛma akwan a wɔfa so yɛ plastic krataa no ayɛ nea ɛfata bio, na ɛbɛma wɔde adi dwuma kɛse wɔ nkɔso a ɛtra hɔ daa mu.
