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Cost estimation is determining the probable cost of a project, which is critical in project development. For government projects in Indonesian construction industry, it is common to use a standard price of goods and services (called SHBJ) publised by the government as a cost reference. This research examines whether the SHBJ provide sufficient and reliable data. A case study from a contractor’s bidding document (RAB) and the SHBJ from the city of Yogyakarta are employed. The result shows that cost estimation based on the SHBJ and the contractor’s RAB gives 12% difference. Using SHBJ data from years 2010 – 2016 a regression equation is obtained as Yi = 62,156 X + 2,003,962 which can be used to estimate project cost in the future. This research also suggests some improvments for the SHBJ.

Polyurethanes are one of many types of polymers that are currently being developed worldwide. Some studies reported many substances involved in synthesizing polyurethanes (PU), with mostly originated from a biomass substance. Our laboratory has synthesized natural fiber – based PU to obtain hybrid PUs through varying reaction variables such as temperature. This study used cellulose, a biomass substance as well as polyethylene glycol and 4,4’ – methylenebis cyclohexyl isocyanate (HMDI) in synthesizing the hybrid PU, and investigated their thermal stability such as decomposition temperature by Differential Scanning Calorimetry (DSC) showed various tendency according to the chain extending temperature for the decomposition temperature. Simultaneous Thermal Analysis (STA) showed glass transition tendency of the product is proportional to the chain extending temperature, where the maximum glass transition obtained from the experimental is 59.8ºC at 70ºC of polymerization. Evaluation of functional group in the hybrid PUs was conducted with FT – IR spectroscopy measurement indicating urethane presence as part of the hybrid PUs.

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