Time-Dependent Properties of Multimodal Polyoxymethylene based binder for Powder Injection Molding / Časovno odvisne lastnosti multimodalnih, na polioksimetilenu temelječih veziv praškov za brizganje

Joamin GONZALEZ-GUTIERREZ, Gustavo Beulke STRINGARI, Barbara ZUPANČIČ, Galina KUBYSHKINA, Bernd VON BERNSTORFF and Igor EMRI  

Anali PAZU, 1 (2011), št. / No. 2 , strani / pages 129-128  
Celotno besedilo / Full text (PDF 

Abstract: Powder injection molding (PIM) is one of the most versatile methods for the manufacturing of small complex shaped components from metal, ceramic or cemented carbide powders for the use in many applications.  PIM consists of mixing the powder and a polymeric binder, injecting this mixture in a mold, debinding and then sintering. Catalytic debinding of polyoxymethylene (POM) is attractive since it shows high debinding rates and low risk of cracking. This work examines the possibility of using bimodal POM as the main component of the binding agent by studying its time-dependent and thermal properties and comparing them to monomodal POM. Furthermore, possible optimization of the binder formulation was investigated by the addition of short molecular weight polymeric chains (wax) to bimodal POM, as to create a multimodal material. It was observed that the magnitude of the complex viscosity for the commercial bimodal material was more than 2 times lower than for the chemically identical monomodal POM within the investigated frequency range. Viscosity values were observed to drop as the content of wax was increased, without compromising thebinders mechanical properties in solid state. A new formulation of bimodal POM plus 8 wt.% of added wax provided the most appropriate results from investigated combinations. This work has shown how the addition of short polymeric chains in POM influences its time-dependent properties in solid and molten state, which can be an important tool for the optimization of binders designed to be used in PIM technology.
Key words: Polyoxymethylene; Powder; Technology; Binder; Time-dependence

Povzetek: Praškasto brizganje (PIM) je ena najbolj vsestranskih metod za proizvodnjo majhnih kompleksno oblikovanih sestavnih delov iz kovine, keramike ali cementnega karbida v prahu za uporabo v številnih aplikacijah. PIM je sestavljen iz mešanja prahu in polimernega veziva, injiciranja te mešanice v kalup, razvezovanja in nato sintranja. Katalitično razvezovanje od polioksimetilena (POM) je privlačno, ker kaže visoko stopnjo razvezovanja in majhno tveganje za razpoke. To delo obravnava možnost uporabe bimodalne POM kot glavne sestavine veziva s študijem časovne odvisnosti in toplotnih lastnosti in jih primerjati z monomodalnim POM. Raziskana je bila možna optimizacija veziva z dodajanjem kratkih polimernih verig (vosek) bimodalnemu POM za ustvarjanje multimodalnega materiala. Ugotovljeno je bilo, da je obseg kompleksnih viskoznosti za komercialne bimodalne materiale več kot 2-krat nižji kot za kemično enake monomodalne POM znotraj opazovanega frekvenčnega območja. Vrednosti viskoznosti so padale, ko se je vsebnost voska povečala, ne da bi ogrozili mehanske lastnosti veziva v trdnem stanju. Nova oblika bimodalne POM plus 8 ut.% dodanega voska je najbolj ustrezala, glede na raziskane kombinacije.  
Ključne besede: polioksimetilen; prašek; tehnologija; vezivo; časovna odvisnost

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