Wood pulp for sack paper is made from softwood by the kraft process . The long fibers provide the paper its strength and wet strength chemicals are added to even further improve the strength. Both white and brown grades are made. Sack paper is then produced on a paper machine from the wood pulp. The paper is microcrepped to give porosity and elasticity. Microcrepping is done by drying with loose draws allowing it to shrink. This causes the paper to elongate 4% in the machine direction and 10% in the cross direction without breaking.  Machine direction elongation can be further improved by pressing between very elastic cylinders causing more microcrepping.  The paper may be coated with polyethylene (PE) to ensure an effective barrier against moisture , grease and bacteria . A paper sack can be made of several layers of sack paper depending on the toughness needed.
One potentially interesting idea is to write a psychology case study of a particular individual or group of people. In this type of paper, you will provide an in depth analysis of your subject, including a thorough biography. Generally, you will also assess the person, often using a major psychological theory such as Piaget's stages of cognitive development or Erikson's eight-stage theory of human development . It is also important to note that your paper doesn't necessarily have to be about someone you know personally. In fact, many professors encourage students to write case studies on historical figures or fictional characters from books, television programs, or films.