Reporter:Chen-Kun LinAdviser:Cheng-Chien Wang

2011.05.31

• Natural rubber (NR) is almost 100% cis-polyisoprene and has numerous advantages for a wide range of applications because of its outstanding physical properties including high resilience, strength, and fatigue resistance .

• In addition, it is a renewable resource and the applications of natural rubber latex (NRL) can be further expanded by the grafting of a second polymer within NRL particles .

Introduction

• Traditionally, polyacrylates have been established in wide-ranging applications as adhesives, coatings, and sealants.

• Principally, they have relatively low glass transition temperatures, which make them apt to handle, process,and purify .

• The chemical modification of NRL by grafting polyacrylates should combine the properties of both NR and the polymer of the grafted monomer.

Introduction

• The miniemulsion process is a versatile technique to synthesize a range of different polymeric nanoparticles, complex hybrid (polymer/inorganic) nanoparticles, functionalized nanoparticles, polymeric nanocapsules for controlled release applications, etc .

• Different parameters like, e.g., the monomer addition sequence , the hydrophilicity of the monomers and polymers , the initiating , the viscosity within the monomer swollen seed latex particles, the reaction temperature, the degree of cross-linking of the polymer chains, etc., have influence on the morphology of these modified NRL particles .

Introduction

• In this paper, we have used miniemulsion polymerization as a technology platform to graft BA on NRL.

• Different types of free radical initiators and different amounts of monomers were used to investigate the grafting efficiency of BA on NRL.

Introduction

• Centrifuged NRL with 69% solid content

• Monomers:methyl, ethyl, butyl, hexyl, or lauryl acrylates

• Sodium dodecyl sulfate (SDS), hexadecane

• 2,2′-azobis(2-methylbutyronitrile) (V59) and 2,2′-azobis(4-methoxy-2,4-dimethyl valeronitrile) (V70)

• 2,4-Pentanedione, cumene hydroperoxide, horseradish peroxidase(HRP)

Materials

3 g butyl, hexyl, or lauryl acrylate

124 mg hexadecane, 60 mg initiator(i.e., V70)

ExperimentalSynthesis of PBA, PHA, and PLA in miniemulsion

124 mg SDS and 12 g deionized water

Stirred for 1 h for pre-emulsificationmixture was ultrasonicated forv120 s

The mixture was stirred at 35 °C for 1 day

ExperimentalGrafting butyl/hexyl/lauryl acrylates with NRL using V59 as initiator

3 g methyl, ethyl, butyl, hexyl or lauryl acrylate,124 mg hexadecane, 60 mg initiator(i.e., V59)

124 mg SDS and 12 g deionized water

14.5 g NRL for pre-emulsification

The miniemulsion was prepared by ultrasonicating the mixture during 120 s

Then, this mixture was stirred at 72 °C for 24 h.

ExperimentalGrafting butyl acrylate with NRL using cumene hydroperoxide

3 g butyl acrylate,124 mg hexadecane, 45 mg of cumene hydroperoxide

120 mg SDS and 12 g deionized water

14.5 g NRL for pre-emulsification

By ultrasonicating the mixture during 120 s

N2 gas and 50 °C 56 mg tetraethylenepentamine and stirred for 24 h

ExperimentalGrafting butyl acrylate with NRL using HRP

3 g butyl acrylate,124 mg hexadecane

120 mg SDS and 10 g deionized water

were stirred with 14.5 g NRL

Mixture stirred under nitrogen in an ice bath for pre-emulsification and

by ultrasonicating the mixture during 120 s

ExperimentalGrafting butyl acrylate with NRL using HRP

9mg HRP was dissolved in 2 g deionized waterand purged with nitrogen for 10 min and injected into theminiemulsion and stirred for 5 min, followed by adding 9

μL 2,4-pentanedione and 7 μL H2O2 simultaneously.

ExperimentalGel fraction

After forming films, the reaction products were submitted to Soxhlet extraction to evaluate the gel content

The extractionwas performed with toluene for a period of 24 h

After eachextraction, the gel fractions were dried at 40 °C in vacuum

Results and discussion

Results and discussion

Results and discussionFilm-forming properties

Fig. 1 Photograph of (a) opaque NRL and PBA (16.4 wt.%) blend and (b) transparent BA (26.7 wt.%)- grafted NR films

Results and discussionFilm-forming properties

Fig. 2 DSC analysis of (a) blend of NRL and PBA (16.4 wt.%) and (a) BA (26.7 wt.%)-grafted NRL. Arrows are indicating the Tgs

Results and discussionDSC analysis

Fig. 3 DSC analysis of (a) blend of NRL and PLA (16.4 wt.%) and (b) LA (16.4wt.%)/NRL. The arrows indicate the Tm

BANRL

Fig. 4 TEM picture of double chemically fixed and ultramicrotome sections of pure NRL

Results and discussionMorphology by TEM analysis

Fig. 5 TEM pictures of double chemically fixed and ultramicrotome sections of PBA (26.7 wt.%) grafted NRL: (1) PBA particles, (2) PBA-grafted NRL

Results and discussionMorphology by TEM analysis

• That grafting efficiencies between 18% and 68% with respect to the amount of employed BA are achieved depending on the initiating system and the amount of BA.

• The grafting efficiency of HA (41 wt.%) is observed to be higher than LA (31 wt.%) on NRL.

• All the polyacrylate (16.4 wt.%)-grafted NRL produces transparent films without cracks.

Conclusions

• Grafting reactions with a higher amount of BA particularly with 26.7 wt.% lead to brittle films.

• Grafting of the acrylate polymers on NRL the Tg of the polyacrylates vanish and probably merge with the Tg of NRL.

• TEM analysis of the modified NRL with BA demonstrates distinct core–shell structures.

Conclusions

回收 NBR-BA微乳液聚合

• 使用回收的 NBR 橡膠，加入單體，使用微乳化聚合，再將橡膠還原成 NBR 乳液。

攪碎過烘乾的橡膠 2 克 +Eac 30 克溶加入 BA 18 克 ，十八烷醇 0.8 克，起始劑

0.18 克

5 克 SLS 加入 100 毫升水 溶

倒入

均質機混合攪拌 30 分

在 75℃下反應 2 小時提高至 80 ℃反應 5 小時最後升至 85 1℃ 小時

未通氮氣

BA 18 克 + 十八烷醇 0.8 克 加入攪碎過烘乾的橡膠 2 克，起始劑 0.18 克

5 克 SLS 加入 100 毫升水 溶

倒入

均質機混合攪拌 30 分

在 75℃下反應 2 小時提高至 80 ℃反應 5 小時最後升至 85 1℃ 小時

未通氮氣