Summary
Summary Tema 10 - Materiais poliméricos
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1. Introdución 2. Características estruturais 3. Tipos de plásticos 4. Comportamiento dos polímeros
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TECNOLOXÍA DOS MATERIAIS TEMA 10TEMA 10
MATERIAIS POLIMÉRICOS
10.1 – INTRODUCIÓN
POLÍMEROS: Calquera sustancia natural ou sintética de alto peso molecular,
molecular comunmente superior a
10.000 g/mol, integrada por unidades máis pequenas (meros
meros)
meros unidas entre si por enlaces covalentes.
covalentes
PLÁSTICOS: Materiais compostos principalmente por polímeros, sintéticos ou naturais altamente modi-
ficados, que nalgunha etapa do seu procesado son facilmente moldeables en formas útiles.
RESINAS: Polímeros que aínda non foron conformados na súa forma final útil.
10.2 – CARACTERÍSTICAS ESTRUTURAIS
PESO MOLECULAR:
44443 ): Lonxitude total de polímero respecto do número de cadeas in-
Peso molecular medio numérico (2
dividuais.
44444
Peso molecular medio ou peso gravimétrico (2 6 ): Lonxitude total da cadea respecto da fracción má-
sica das cadeas individuais.
∑ 2< =<
Mi: Peso molecular medio no intervalo “i” 44443 =
2
∑ =<
∑ 2< =<
Ni: Número de moléculas de peso molecular Mi 44444
2 6 = ∑ 6< 2< =
∑ =<
3< @<
wi: Fracción de peso del intervalo “i” en moléculas wi =
∑ 3< @<
23
M0: Peso molecular da unidade monomérica n=
2<
44444
2
Índice de heteroxeneidade (IH) ou de polidispersión (PDI) ⟶ IH = 44446
23
Se o IH é alto o intervalo de fusión aumenta e prodúcese abrandamento e, polo tanto, peores pro-
piedades mecánicas, como a menor resistencia a axentes químicos.
Influencia do peso molecular:
• Aumento da temperatura de abrandamento.
• Maior viscosidade.
• Mellora das propiedades mecánicas.
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