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The future of plastics: degraded or recycled? Very different properties and applications?

Time : 2023-05-05 Hits : 8

Degradable and recycled plastics are two potential options for solving the problem of white pollution.


1. Biodegradable plastics for packaging and agricultural films

 

Biodegradable plastics are plastics whose properties can meet the performance requirements for use, remain unchanged during their shelf life, and degrade to environmentally friendly substances under natural environmental conditions after use. Degradable plastics have their advantages in terms of performance, practicality, degradability and safety.

In terms of performance,biodegradable plastics can meet or in some specific areas exceed the performance of conventional plastics;

In terms of practicality,degradable plastics have application properties and hygiene properties similar to those of similar conventional plastics;

in terms of degradability,degradable plastics can, after use, complete degradation relatively quickly in the natural environment (specific micro-organisms, temperature, humidity) and become fragments or non-toxic gases that can be easily used by the environment, reducing the impact on the environment;

In terms of safety, the substances produced or left over by the degradation process of degradable plastics are harmless to the environment and do not affect the survival of humans and other organisms.

The biggest obstacle to replacing traditional plastics at present, and the disadvantage of biodegradable plastics, is their high production cost compared to similar traditional or recycled plastics. Therefore, in applications such as packaging and agricultural films, which are short-lived, difficult to recycle and separate, have low performance requirements and require high levels of impurities, biodegradable plastics have more substitution advantages.


2. Recycled plastics are suitable for applications where hygiene requirements are not high

Recycled plastics are plastic raw materials that are re-processed through physical or chemical methods such as pretreatment, melt granulation and modification of waste plastics. The biggest advantage of recycled plastics is that they are cheaper than new and biodegradable plastics and can be processed to produce only one aspect of the plastic's properties, depending on the performance required. In less frequent cycles, recycled plastics can maintain similar properties to conventional plastics, or can be blended with new material to maintain consistent properties.

However, after a number of cycles, the properties of recycled plastics deteriorate considerably or to the point of being unusable. In addition, recycled plastics are less likely to maintain good hygienic properties while remaining economical. For this reason, recycled plastics are suitable for applications where the number of cycles is low and the hygienic properties are not required.

The production process of recycled plastics


Waste plastics --- sorting --- crushing --- washing --- shaking dry --- auxiliary material configuration (modification) --- extrusion granulation --- pelletizing packaging --- final product

 

Changes in the properties of common plastics after recycling

Types of plastic

Change in performance after one regeneration

Performance changes after multiple regeneration

PE

Yellowing of colour and reduced performance

 

Decreasing viscosity for HDPE and increasing viscosity for LDPE

 

PP

Colour almost constant Melt index increased

 

Increased colour, still rising melt index, reduced fracture strength and tensile strength, etc.

 

PS

Yellowing of colour and reduced performance

 

The degree of decline in each property is proportional to the number of regenerations

 

PVC

More pronounced discolouration with a light brown tinge

Almost opaque brown colour with a tendency to decrease in specific viscosity

 

ABS

More pronounced discolouration, but no significant change in properties when blended up to 20-30%.

 

Colour increases and all properties tend to decrease

 

PA

Elongation decreases, elasticity tends to increase

 

Colour increases, elongation decreases further

Note: Melt index, the fluidity of plastic materials during processing; specific viscosity, the static viscosity of a unit volume of liquid

3、White pollution mainly comes from the packaging field, biodegradable plastics have more room to play

Through comparison, biodegradable plastics have more alternative advantages in packaging, agricultural film and other applications where the use time is short and difficult to recycle and separate, because of their more stable performance and lower recycling costs; while recycled plastics have more advantages in household utensils, construction materials, electrical appliances and other applications where the use time is long and easy to sort and recycle because of their lower prices and production costs. White pollution mainly comes from the packaging sector, where biodegradable plastics have more room to play. With policy promotion and cost reduction, the future biodegradable plastics market has a bright future.

Comparison of biodegradable and recycled plastic properties


Degradable plastic

Recycled plastics

Degradable

Fully-degradable

Non-degradable

New product properties

Close to conventional plastics

--

Recycled product properties

Non-renewable

Good

Recycled situation

Can be buried directly

with wide variation in recycling economics

Environmental benefits

Completely degradable, eliminating white pollution and saving oil resources

Waste plastic recycling, reduce resource waste

Price

Higher

Lower

For disposable, hard-to-recycle areas

×

Suitable for price-sensitive areas with low performance requirements

×

Main application industry

Packaging, agricultural film, etc.

Household utensils, building materials, etc.


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