The chemicals sector was bolstered by gains made by plastics group Victrex on Tuesday after the company reported its half-year results.Victrex said profit surged 57% while sales volumes rose 22% in the last six months after a strong performance in all of its major markets. The group, which manufactures and sells polymers, said pre-tax profit rose to £48.3m in the six months ended 31 March 2011 from £30.8m the year before. The banking sector has been weighed down by negative comments by ratings agency Moody's.RBS and Lloyds were out of favour after Moody's said it is considering downgrading several UK banks in response to the regulators appearing less willing to bail out lenders in the future. "The reassessment is not driven by either a deterioration in the financial strength of the banking system or that of the government," said Moody's senior credit officer Elisabeth Rudman. "It has been initiated in response to ongoing guidance from the UK authorities (the Bank of England, the Financial Services Authority and the Treasury) that banks that fail in the future should not expect capital injections from the public purse." ---BCTop performing sectors so far todayChemicals 7,492.54 +1.75%Mining 24,769.81 +1.75%Industrial Metals & Mining 7,538.55 +1.61%Automobiles & Parts 4,895.91 +1.55%Oil & Gas Producers 8,248.31 +1.34%Bottom performing sectors so far todayMobile Telecommunications 3,881.16 -0.89%Banks 4,423.87 -0.84%Life Insurance 4,346.99 -0.65%Insurance (non-life) 1,638.12 -0.64%Travel & Leisure 4,662.72 -0.50%