در سال های اخیر, تلاش های بسیاری برای توسعه پلاستیک های زیست تخریب پذیر از منابع تجدید پذیر صورت گرفته است. نشاسته یک کربوهیدرات پر مصرف است.Because of poor mechanical properties and hydrophilicity of starch for using of this natural polymer as biocompatible polymer, many researchers have investigated to starch composite with different polymers, such as styrene. But significant differences between structure of starch and synthetic polymers are factors for incompatibility. لذا برای بهبود این ناسازگاری, محققان بسیاری کار های مختلفی انجام داده اند که می توان به اصلاح شیمیایی ساختار نشاسته و پل ی استا ی رن و/یا اضافه نمودن یک سازگار کننده به آلیاژ اشاره نمود. در ا ی ن پژوهش کوپل ی مر پ ی وند ی پل ی استا ی رن- نشاسته با استفاده از ی ک ش ر وع کننده حرارت ی Therefore, many researchers have investigated on chemical modification of starch and styrene structures and/or adding a compatibilizer to the compound for more compatibility. In this work, graft copolymer of starch-polystyrene (PS-g-starch) by using benzoyl peroxide as thermal initiator, was prepared in an internal mixer as reactor. و به منظور افزا ی ش درصد پ ی وند زن ی ب ی ن ا ی ن دو پل ی مر ناسازگار از مالئ ی ک ان ی در ی د به عنوان ی ک سازگار کننده ی چند عامل ی به روش خشک و ی ک ی ا دو مرحله ا ی در همان دستگاه مخلوط کن داخل ی استفاده شد. ابتدا در روش دو مرحله ا یIn order to increase the percentage of grafting, maleic anhydride (MA) was used as dry compatibilizer by one or two stages mechanism in the same internal mixer. To evaluate grafting and homopolymerization percentage, extraction analysis carried out in soxhlet apparatusand toluene as solvent for isolating homopolymer part. Then acid leaching method with acetic acid and perchloric acid was used for isolating grafting part. Grafting and homopolymerizationpercent and yield werecalculated by gravimetry method.The highest percentage of grafted polymer in one and two steps methods was 36.152% and 57.25%, respectively, in 10% composition of MA. To confirm the grafting reaction and kinds of new functional groups Transfer Infrared Spectroscopy (FTIR) of samples after grafting extraction was used, that showed new peaks in 1720 cm-1 for C=O band of grafted MA in soxhleted samples and in 1460, 1553 and 3058 cm-1 for C-H groups and 1600 for C=C group of aromatic rings of polystyrene. Because of extraction of samples, these results are reason for successful substitution of MA's carboxilic groups and grafting of polystyrene on starch chains. To confirm the quality of esterification and grafting reactions Scanning Electronic Microscope (SEM) was used, this analyse before and after of soxhlet extraction showed the covering and grafting of polystyrene on starch, respectively and after alloying of samples with High impact polystyrene (HIPS) showed the hemogen samples and no phase separation was observed. To investigate of thermal stability of samples, thermal gravimetric analyses (TGA) was used. Their thermal stability of the product were obtained from the temperature test TGA استفاده شد. TGA was used. Result indicated that the samples showed two steps thermal degradation. The first step occurred in 320-410?C indicates modificated starchpart degridation that was incresed than native starch and the second step occurred in 410-560?C representing the polystyrene degradation. To evaluate the process ability of compounds, the melt flow index was determined and sheats with hot press at 180 ?C was prepared. نتا ی ج حاک ی از ی ک تخر ی ب دو مرحله ا ی م ی باشد که بخش اول مربوط به نشاسته اصلاح شده بوده( ؟ ) که نسبت به نشاسته خالص افزا ی ش ی افته است و بخش دوم مربوط به پل ی استا ی رن م ی باشد( ؟ ). نتا ی ج فوق حاک ی از ا ی ن م ی باشد که نمونه ها ی حاصل شده قابل ی ت فرآ ی ندپذ ی ر ی داشته و دارا ی خصلت ترموپلاست ی ک ی م ی باشند. Above results indicated that synthesize d samples have prossesability and thermoplastic character . In order to increasing MFI of samples the moderate amonght of HIPS was added to samples and MFI was measured that shows MFI was increased by increasing HIPS (highest MFI was 0.33 g/min at 10% HIPS composition). Also, for determination of hardness, physical properties Hardness shore D was used, that shows Hardness was decreased by increasing HIPS, and for evaluation of Impact strength of samples, Impact test was used and results shows increasing in breakage energy by increasing HIPS (highest breakage energy was 0.2 J at 10% HIPS composition). Keywords : Starch, styrene, maleic anhydride, esterification, graft copolymer, internal mixer.