Tires are made by adding fillers to polymeric matrix. Alongside other additives, the tire compounds are cured and shaped. The conventional fillers used in the process is carbon black and silica. Owing to the environmental concerns associated with the use of these fillers, lightweight polysaccharides derived from bio sources were explored in this work as possible replacement. The fillers that were used in this project were cellulose nanocrystals and alpha 1,3 glucan. Their surface chemistry is like that of silica fillers having abundant surface hydroxyl groups. These bio fillers are hydrophilic and not compatible with hydrophobic polymer matrix such as natural rubber. In this regard, they were modified to be compatible with the polymeric matrix. To achieve this modification, two silanes were employed: TESPD, APS being aliphatic silanes and SID, SIB being cyclic silanes. All the compounds were compared with silica compounds as reference. The results obtained with these fillers showed that the APS silanes promote very fast vulcanization and increases the crosslinking density. With this silane, a higher storage modulus was achieved, and properties were better than the reference silica compounds. The drawback that was experience with APS is the fact that large amount of the silane affects the tensile properties. The reaction mechanism observed for TESPD compounds reveals that the storage modulus of the compounds with this silane may not be comparable to that of APS but the tensile properties were remarkably higher. Deciding on which silanes to be used would therefore connect with the expected properties that is of interest. When the cyclic silanes were explored, their reactive nature made the vulcanization to be fast. The reinforcement of the various compounds was very interesting. However, it was observed that at low silane loading between 2-5%, the properties remain fairly the same even when the silane amounts were increased up to 12%. In fact, the cyclic silanes amount exceeding 5% made the material brittle and resulted in very inferior tensile properties. It is therefore advisable to prepare the polysaccharides filler with very low amount of cyclic silanes. The modifications with silanes were explored as it is heavily used in the tire industry. Alternatively, a green enzymatic modification using lipases as catalyst was also investigated. The procedure developed in this work was simplified with the possibility of recovering all the filler used in the reaction and the reuse of other reacting species. The concept in this modification was to graft moieties that can serve to hydrophobized the surface and subsequently promote a direct crosslinking between the filler and rubber. The cellulose nanocrystal was the filler for this modification and acetyl and methacrylate groups were grafted on the surface. When compounds were prepared with the modified CNC, the properties were very interesting. In fact, they were better than the reference silica. The results obtained in this process are very promising especially when the future of the tire industry is considered. Much attention was given to cellulose nanocrystals compared to alpha 1,3 glucan. Although glucan is a new entrant into the biofiller world for the tire industry, it is still being studied to ascertain their suitability. The compounds made with glucan using silanes showed that some aspects of the properties are lower that the reference silica. In terms of the green compounds and vulcanization properties, it was relatively better than silica compound. But when glucan compounds were vulcanized, the reinforcements and tensile properties were observed to be lower than silica compounds. It is obvious that more treatment, processing methods and the use of vast alternative modification strategy is needed to prepare glucan for improved properties and possible use in tire compounds.

I pneumatici sono realizzati aggiungendo riempitivi alla matrice polimerica. Insieme ad altri additivi, le mescole per pneumatici vengono polimerizzate e modellate. I riempitivi convenzionali utilizzati nel processo sono nerofumo e silice. A causa delle preoccupazioni ambientali associate all'uso di questi riempitivi, in questo lavoro sono stati esplorati polisaccaridi leggeri derivati da fonti biologiche come possibile sostituzione. I riempitivi utilizzati in questo progetto erano nanocristalli di cellulosa e alfa 1,3 glucano. La loro chimica superficiale è simile a quella delle cariche di silice aventi abbondanti gruppi idrossilici superficiali. Questi bio-riempitivi sono idrofili e non compatibili con la matrice polimerica idrofobica come la gomma naturale. A questo proposito, sono stati modificati per essere compatibili con la matrice polimerica. Per ottenere questa modifica, sono stati impiegati due silani: TESPD, APS essendo silani alifatici e SID, SIB essendo silani ciclici. Tutti i composti sono stati confrontati con i composti di silice come riferimento. I risultati ottenuti con queste cariche hanno mostrato che i silani APS favoriscono una vulcanizzazione molto rapida e aumentano la densità di reticolazione. Con questo silano, è stato ottenuto un modulo di stoccaggio più elevato e le proprietà erano migliori rispetto ai composti di silice di riferimento. Lo svantaggio riscontrato con APS è il fatto che una grande quantità di silano influisce sulle proprietà di trazione. Il meccanismo di reazione osservato per i composti TESPD rivela che il modulo di conservazione dei composti con questo silano potrebbe non essere paragonabile a quello di APS, ma le proprietà di trazione erano notevolmente superiori. La decisione su quali silani da utilizzare sarebbe quindi collegata alle proprietà attese che è di interesse. Quando sono stati esplorati i silani ciclici, la loro natura reattiva ha reso la vulcanizzazione veloce. Molto interessante il rinforzo delle varie mescole. Tuttavia, è stato osservato che a un basso carico di silano compreso tra il 2-5%, le proprietà rimangono pressoché le stesse anche quando le quantità di silano sono state aumentate fino al 12%. Infatti, la quantità di silani ciclici superiore al 5% rendeva il materiale fragile e produceva proprietà di trazione molto inferiori. Si consiglia quindi di preparare la carica polisaccaridica con bassissime quantità di silani ciclici. Le modifiche con i silani sono state esplorate in quanto è ampiamente utilizzato nell'industria dei pneumatici. In alternativa, è stata studiata anche una modifica enzimatica verde che utilizza le lipasi come catalizzatore. La procedura sviluppata in questo lavoro è stata semplificata con la possibilità di recuperare tutto il filler utilizzato nella reazione e il riutilizzo di altre specie reagenti. Il concetto in questa modifica era quello di innestare porzioni che possono servire per idrofobizzare la superficie e successivamente promuovere una reticolazione diretta tra il riempitivo e la gomma. Il nanocristallo di cellulosa è stato il riempitivo di questa modifica e sulla superficie sono stati innestati gruppi acetile e metacrilato. Quando i composti sono stati preparati con il CNC modificato, le proprietà erano molto interessanti. In effetti, erano migliori della silice di riferimento. I risultati ottenuti in questo processo sono molto promettenti, soprattutto se si considera il futuro dell'industria dei pneumatici. Il glucano è un nuovo concorrente nel mondo dei biofiller per l'industria dei pneumatici, è ancora in fase di studio per accertarne l'idoneità. I composti realizzati con glucano utilizzando silani hanno mostrato che alcuni aspetti delle proprietà sono inferiori alla silice di riferimento. In termini di composti verdi e proprietà di vulcanizzazione, era relativamente migliore del composto di silice.

(2021). Light Weight Polysaccharides as biofillers for Elastomeric Compounds. (Tesi di dottorato, Università degli Studi di Milano-Bicocca, 2021).

Light Weight Polysaccharides as biofillers for Elastomeric Compounds

IMIETE, IIKPOEMUGH ELO
2021

Abstract

Tires are made by adding fillers to polymeric matrix. Alongside other additives, the tire compounds are cured and shaped. The conventional fillers used in the process is carbon black and silica. Owing to the environmental concerns associated with the use of these fillers, lightweight polysaccharides derived from bio sources were explored in this work as possible replacement. The fillers that were used in this project were cellulose nanocrystals and alpha 1,3 glucan. Their surface chemistry is like that of silica fillers having abundant surface hydroxyl groups. These bio fillers are hydrophilic and not compatible with hydrophobic polymer matrix such as natural rubber. In this regard, they were modified to be compatible with the polymeric matrix. To achieve this modification, two silanes were employed: TESPD, APS being aliphatic silanes and SID, SIB being cyclic silanes. All the compounds were compared with silica compounds as reference. The results obtained with these fillers showed that the APS silanes promote very fast vulcanization and increases the crosslinking density. With this silane, a higher storage modulus was achieved, and properties were better than the reference silica compounds. The drawback that was experience with APS is the fact that large amount of the silane affects the tensile properties. The reaction mechanism observed for TESPD compounds reveals that the storage modulus of the compounds with this silane may not be comparable to that of APS but the tensile properties were remarkably higher. Deciding on which silanes to be used would therefore connect with the expected properties that is of interest. When the cyclic silanes were explored, their reactive nature made the vulcanization to be fast. The reinforcement of the various compounds was very interesting. However, it was observed that at low silane loading between 2-5%, the properties remain fairly the same even when the silane amounts were increased up to 12%. In fact, the cyclic silanes amount exceeding 5% made the material brittle and resulted in very inferior tensile properties. It is therefore advisable to prepare the polysaccharides filler with very low amount of cyclic silanes. The modifications with silanes were explored as it is heavily used in the tire industry. Alternatively, a green enzymatic modification using lipases as catalyst was also investigated. The procedure developed in this work was simplified with the possibility of recovering all the filler used in the reaction and the reuse of other reacting species. The concept in this modification was to graft moieties that can serve to hydrophobized the surface and subsequently promote a direct crosslinking between the filler and rubber. The cellulose nanocrystal was the filler for this modification and acetyl and methacrylate groups were grafted on the surface. When compounds were prepared with the modified CNC, the properties were very interesting. In fact, they were better than the reference silica. The results obtained in this process are very promising especially when the future of the tire industry is considered. Much attention was given to cellulose nanocrystals compared to alpha 1,3 glucan. Although glucan is a new entrant into the biofiller world for the tire industry, it is still being studied to ascertain their suitability. The compounds made with glucan using silanes showed that some aspects of the properties are lower that the reference silica. In terms of the green compounds and vulcanization properties, it was relatively better than silica compound. But when glucan compounds were vulcanized, the reinforcements and tensile properties were observed to be lower than silica compounds. It is obvious that more treatment, processing methods and the use of vast alternative modification strategy is needed to prepare glucan for improved properties and possible use in tire compounds.
ORLANDI, MARCO EMILIO
ZOIA, LUCA
pneumatici; nanocellulosa; alfa 1,3 glucano; silani; polimeri
Tires; nanocellulose; alpha 1,3 glucan; silanes; polimeri
CHIM/05 - SCIENZA E TECNOLOGIA DEI MATERIALI POLIMERICI
Italian
16-apr-2021
SCIENZA E NANOTECNOLOGIA DEI MATERIALI
33
2019/2020
open
(2021). Light Weight Polysaccharides as biofillers for Elastomeric Compounds. (Tesi di dottorato, Università degli Studi di Milano-Bicocca, 2021).
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/313695
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