Modification Of Nanocrystalline Cellulose And Its Application In Natural Rubber Composites

As a kind of environmental-friendly biomacromolecular material, nanocrystallinecellulose（NCC） has extensive sources, low cost, low density and can be easily prepared.Rod-like nanocrystalline cellulose has relatively high aspect ratio, perfect crystal structure,good thermal stability and excellent mechanical properties which make it a new type of greenreinforcing filler for rubber.Firstly, this paper discusses that influence of acid solution conditions on the preparationof nanocrystalline cellulose, including temperature, time and the liquid-solid ratio. And thebest conditions were confirmed for:45℃,30min,the liquid-solid ratio10（ml）:1（g）. Thelaser particle size analyzer, SEM and TEM analysis showed that NCC was typical ofnano-structure macromolecular material. The length of NCC was about100⁶00nm,diameter was in50nm below, slenderness ratio was larger. Fourier transfer infraredspectroscopy（FTIR）and X-ray diffraction（XRD）analysis showed that NCC had the samechemical structure with cellulose, with perfect crystal structure of the excellent mechanicalproperties. Thermal thermogravimetric analysis （TGA） and differential scanning calorimetry（DSC） test showed that NCC had good thermal stability. And related chemical reaction can beprocessed in the amorphous zone. Silane coupling agent of KH560, KH550, KH570, KH580,Si-69, A-151, titanate coupling agent NDZ-102, adhesive RH and vulcanization crosslinkingagent MDMA were applied to modify nanocrystalline cellulose. The result show that KH550and RH have better effects for modifying nanocrystalline cellulose and the dosage of KH550and RH were respectively0.3phr per10phrNCC,6phr per100phrNR.Nanocrystalline cellulose was modified by3-aminopropyl-triethoxysilane （KH550）. Themodified nanocrystalline cellulose （MNCC） was further investigated to partially replace silicafor natural rubber （NR） composites via coagulation. NR/MNCC/SiO₂and NR/NCC/SiO₂nanocomposites were prepared. Through the comparison of vulcanization characteristics,processing properties of compounds and mechanical properties, hot air aging properties,compression fatigue properties, dynamic mechanical performance，the abrasion resistance andresistance to flex cracking of NR/MNCC/SiO₂and NR/NCC/SiO₂nanocomposites, MNCCwas proved to be more efficient than NCC. Moreover, fine MNCC dispersion and stronginterfacial interaction were achieved in NR/MNCC/SiO₂nanocomposites. The observedreinforcement effects were evaluated based on the results of apparent crosslinking density（Vr）, thermo-gravimetric （TG） and scanning electron microscope （SEM） analyses ofNR/MNCC/SiO₂in comparison with NR/NCC/SiO₂nanocomposites. FTIR, DSC, TGA and contact angle test show that the interaction occurs between KH550and NCC, leading to moreclosely combination between NCC and NR. XRD analysis shows that the original perfectcrystal structure of NCC with excellent mechanical properties was kept after KH550modification.Influence of resorcinol and hexamethylenetetramine complex （RH） on the structure andproperties of NR/NCC/SiO₂/RH was studied. The structure was characterized by Vr, TGA andSEM. The processing properties, mechanical properties, hot air aging properties, dynamicmechanical properties and dynamic compression fatigue properties of the NR/NCC/SiO₂/RHnanocomposites were characterized by rubber processing analyzer （RPA）, electronic Tensilemachine and dynamic machine analyzer （DMA）, dynamic compression fatigue performancetester. The results showed that the whole performance of NR/NCC/SiO₂/RH nanocompositeswas substantially improved. Their better performances on processing, mechanical properties,hot air aging properties，dynamic mechanical properties，heat build-up and permanent setwere correlated to the better dispersion of NCC and stronger interface interaction between NRand NCC. FTIR and X-ray photoelectron spectroscopy （XPS） analysis showed that hydrogenbond was formed between phenolic hydroxyl group of RH and surface hydroxyl group ofNCC. DSC and TGA analysis further proof that the interaction between RH and NCC. XRDtest shows that the original crystalline structure of NCC did not change after adding RH.Epoxied natural rubber （ENR） act as compatibility agent filled into the NR/NCCcomposites. The result exhibit that the processing properties and mechanical performance ofNR/ENR/NCC are better compared to NR/NCC compound or composites. When about4phrENR was added into NR/NCC composites, the hot air aging performance and abrasionresistance were maintained. Resistance to flex cracking and wet resistance performance wereremarkly improved, rolling resistance was kept.In this paper, the result indicates that numbers of good performance of natural rubbercomposites were made when the nanocrystalline cellulose as a kind of reinforcing filler fornatural rubber. Better properties of natural rubber composites can be made when NCC wasmodified by KH-550or RH, then as reinforcing filler to partially replace silica for NR, or wasmodified by ENR directly.