افزايش مقاومت در برابر حلال و سختي كوپليمر قطعه اي ﴿استايرن- ايزوپرن-استايرن﴾ در اثر تابش پرتو UV

چكيده انگليسي :

65 Increasing Solvent Resistance and Hardness of Styrene Isoprene Styrene Block Copolymer with UV Irradiation Mehdi Javani Javani mehdi@yahoo com Date of Submission September 16 2013 Department of Chemical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Saied Nouri Khorasani saied@cc iut ac ir Abstract Crosslinking reaction of polymers by ultraviolet UV irradiation has been important in industries specially for coating ink and printing applications In this research styrene isoprene styrene block copolymer was selected as a base polymer and photocrosslinking reaction under UV irradiation in presence of both benzoin photoinitiator and ethylene glycol dimethacrylate EGDMA monomer as crosslinking agent were carried out Styrene isoprene styrene block copolymer SIS have two phase morphology and is commonly used in pressure sensitive adhesives and flexographic printing plates In these applications SIS should have solvent resistance and chemical resistance properties UV irradiation curing has become a well accepted technology which is capable of fast polymerization in solid media despite severe molecular mobility restrictions Benzoin was used as photoinitiator because it has cromophor group C O that could absorb UV irradiation EGDMA was used as crosslinking agent as it has functional groups C C that could react with double bond C C of SIS Specimens were prepared by melt mixing in an internal mixer The compounds then made into sheets by compression molding machine ATR FTIR spectroscopy before and after exposure to UV shows absorbtion band of double bond C C at 1543 Cm 1 decreases after exposure This decreasing is due to reaction of double bond of copolymer with double bond of EGDMA Hardness and solubility tests shows with increasing concentration of benzoin photoinitiator 0 1 1phr hardness and gel content of samples increases while swelling ratio decreases Because with increasing of benzoin concentration free radical concentration produced under UV exposure were increased So crosslinking between polymeric chains increased and solvent resistance of polymer network increased Also with increasing EGDMA crosslinking agent 1 10phr hardness and gel content of samples increases while swelling ratio decreases Because with increasing concentration of EGDMA crosslinking between copolymer chains increase so diffusion of solvent in polymer network decrease At low concentration of EGDMA gelation did not occure Taguchi method for design of experiment showed maximum hardness and gel content is for compound contain of 1 phr benzoin photoinitiator and 10 phr EGDMA monomer Maximum increase of hardness and gel content occurred when using 1phr benzoin and 10 phr EGDMA it was about 53 8 for gel content and 37 for hardness Results of thermal stability test showed heating of unirradiated sample containing 1 phr benzoin and 10 phr EGDMA for 5 min at 150 C caused about 20 wt of sample has become insoluble in toluene As crosslinking reaction occure in sample upon heating So heat resistance of this compound is low However this compound can be used for flexographic printing plate but for increasing thermal stability of compound can be added an antioxidant to compound Physical properties of sample using difunctional monomers butyl acrylate and methyl methacrylate and tetrafunctional monomer Allyl methacrylate compared with effect of EGDMA Results show the sample with EGDMA has highest hardness and addition of methyl methacrylate and allyl methacrylate as crosslinking agent didn t have any effect on changing hardness Solubility test shows the sample containing butyl acrylate has most gel content and least swelling ratio Gel content in sample containing methyl methacrylate and allyl methacrylate were zero and 12 8 respectively Keywords photocrosslinking styrene isoprene styrene copolymer UV curing benzoin PDF created with pdfFactory trial version www pdffactory com

جواني، مهدي

افزايش مقاومت در برابر حلال و سختي كوپليمر قطعه اي ﴿استايرن- ايزوپرن-استايرن﴾ در اثر تابش پرتو UV

شبكه اي شدن نوري , پخت UV , بنزويين