Biopolymers - Wood-based

Question 1

What does wood consist of and give a short description

Answer 1

50% Cellulose (load-bearing compound), 25% Lignin (the glue), 20% Hemicellulose (the linkers) and extractives

Question 2

What main processes are there for wood?

Answer 2

Wood material technology, pulping and papermaking and biorefinery.

Question 3

What are the most common wood products?

Answer 3

Construction material, paper, fibers, energy, chemicals, polymers and nanomaterials.

Question 4

Whats makes lignin a potential compound for uses in biopolymer chemistry?

Answer 4

It’s aromatic, abundant and have reactive functional groups.

Question 5

Name some challenges for processing wood and utilize products.

Answer 5

extraction does not give 100% purity, structure dependent on extraction method, complex molecules,

Question 6

Whats the hierarchical structure of wood?

Answer 6

Cellulose polymer - elementary fibril (amorphous and crystalline regions) - microfibril - secondary wall structure (cellulose, lignin, hemicellulose) - cell wall layer - fibers - wood

Question 7

Whats the basic structure of cellulose?

Answer 7

glucose molecules creates a cellobiose based unit. The polymer have non-reducing and reducing end groups.

Question 8

What different region does cellulose have and what are their properties?

Answer 8

Amorphous domain - reactive and accessible for water (can swell)
Crystalline domain - not accessible for water, can only be modified on the surface, have polymorphs, differ by hydrogen bonding

Question 9

What are cellulose polymorphs?

Answer 9

The crystalline domain can have different structure. Natural cellulose I have the structure I alpha and beta. Cellulose produced by bacteria/algae is enriched in I alpha while plants mainly consists of I beta. With chemical modification cellulose I can be turned into cellulose II, III, IV.

Question 10

How can crystalline cellulose I be detected and whats the hypothesized structure?

Answer 10

Can be detected by x-ray. The structure is that the molecules lies in sheets. Within the sheets there is hydrogen bonds and between the sheets van der waals interaction.

Question 11

What nanocellulose grades are there from wood?

Answer 11

Microfibrillated cellulose MFC, Cellulose nanofibrils CNF, Cellulose nanocrystals CNC

Question 12

Whats the difference between the nanocellulose grades

Answer 12

MFC - fibers that have fibrillar surface due to mechanial or chemical treatment, CNF - individual fibrils liberated from the cell wall, CNC - crystalline parts of the cell wall fibrils.

Question 13

How do you produce MFC or CNF?

Answer 13

The raw material is pulp or biomass, this is pretreated with alkaline, acidic, enzymatic or oxidative solutions. Then it is disintegrated either by mechanical or enzymatic treatment. Then oxidative post-treatment and concentration or drying up to 15 w%

Question 14

Name some properties of nanofibrils

Answer 14

It’s a water-rich viscous gel or paste. This property can be modified to create different types of gels with different appearance and hardness. They are generally strong. films can also be created. good oxygen barrier.

Question 15

Why can cellulose be used for biosensing

Answer 15

It’s biocompatible, nontoxic, biodegradable, resistant to many solvents. Nanocellulose have high surface area and high mechanical strength.

Question 16

How is cellulose nanocrystals CNC produced?

Answer 16

pulp, biomass or cotton is pretreated by bleaching, disintegrated by acid or enzymatic hydrolysis and then post-treated by oxidation or removal of charges. Then it is concentrated or dried.

Question 17

Name some properties of CNC

Answer 17

Rod-like rigid particles. Can be a water-rich viscous gel or paste and its property can be modified. The modification can affect how light is reflected => appearance.

Question 18

How is nanocrystalline created from cellulose

Answer 18

By acidic hydrolysis

Question 19

Name some uses of CNC

Answer 19

It has hydrophilic and hydrophobic regions and can be used as emulsifier for pickering solutions. Can also be used to create films when it’s charged. The chiral property can give the film different colors.

Question 20

What is hemicellulose?

Answer 20

It’s a polysaccharide that is a little branched. Side product from the pulp industry.

Question 21

How is the hemicellulose different in soft- and hardwood.

Answer 21

In softwood the hemicellulose is mostly galactoglucomannans (mannose, glucose in the backbone with galactose branch) with some xylan, some acetyl groups. In hardwood it’s mosty xylans and some glucomannan. Backbone mainly xylose, have glucuronic acid and acetyl groups.

Question 22

What can hemicelluloses be used for?

Answer 22

To produce films and film additives that are renewable, oxygen, grease and aroma barrier. Can also be used as a surface active hydrotrope (emulsifier without a long tail). Because it is branched (soft wood galactoglucomannan)

Question 23

What is Lignin?

Answer 23

It’s a matrix material usually binding fibers together/the structural part of wood, it’s not a polysaccharide - more like a phenolic molecule/macromolecule. The structure is a bit unkown. The brown stuff left from pulping. Not so moist-sensitive as polysaccharides usually are.

Question 24

What uses are there for lignin?

Answer 24

Currently it’s main use is for energy but material uses are on the making. The particles can be used for pickering emulsions and encapsulate substances.